JP7639384B2 - Object detection device - Google Patents

Description

The present invention relates to an object detection device that is mounted on a moving body and configured to detect objects around the moving body.

When an ultrasonic sensor detects an object such as an obstacle, there is a problem that the signal emitted by another ultrasonic sensor mounted on the vehicle itself or another ultrasonic sensor mounted on another vehicle around the vehicle itself may be mistaken for the sensor's own signal. In response to this problem, Patent Document 1 proposes a technique that uses multi-bit encoding using the FSK or PSK method.

Special Publication No. 2013-538344

According to the technology disclosed in Patent Document 1, an ultrasonic sensor is capable of identifying whether or not a received wave is a reflected wave of ultrasonic waves that it itself transmitted. However, when the ultrasonic sensor faces a wall or a pole, even if the reflected wave is an ultrasonic wave that it itself transmitted, the reflected wave from the base and the reflected wave from the front overlap.

The inventors have discovered that when encoding is used in obstacle detection using ultrasonic sensors, in scenes where reflected waves overlap, interference between the reflected waves makes it difficult to identify the code. The present invention has been made in consideration of the circumstances exemplified above. In other words, the present invention provides, for example, an object detection device with improved code identification performance.

The object detection device (3) according to the first aspect is configured to detect an object (B) around a moving body (C) when mounted on the moving body.
This object detection device is
A drive control unit (71) that sets a frequency modulation mode within a predetermined frequency band in a drive signal that drives a transmission unit (40A) to transmit to the outside a transmission wave that is an ultrasonic wave encoded by frequency modulation;
a detection unit (73) that detects the object based on a reception signal corresponding to a reception result by a receiving unit (40B) of a reception wave including a reflected wave of the transmission wave by the object;
Equipped with
The detection unit has a determination unit (74) that determines a code included in the received wave based on a match between a reference signal corresponding to the drive signal and the received signal,
the drive control unit is configured to select and set, as a code to be assigned to the drive signal, any one of a plurality of types of codes including at least a first code characterized by a frequency modulation mode in which a frequency increases over time in a first frequency band, a second code characterized by a frequency modulation mode in which a frequency increases over time in a second frequency band different from the first frequency band, a third code characterized by a frequency modulation mode in which a frequency decreases over time in a third frequency band, and a fourth code characterized by a frequency modulation mode in which a frequency decreases over time in a fourth frequency band different from the third frequency band, and to increase a frequency band and/or a number of pulses in the drive signal as the code corresponding to a frequency band farther away from a center frequency of the transmission unit;
an upper limit frequency of the first frequency band is higher than an upper limit frequency of the second frequency band;
a lower limit frequency of the first frequency band is higher than a lower limit frequency of the second frequency band,
an upper limit frequency of the third frequency band is higher than an upper limit frequency of the fourth frequency band;
The lower limit frequency of the third frequency band is higher than the lower limit frequency of the fourth frequency band.
The object detection device (3) according to the third aspect is configured to detect an object (B) around a moving body (C) when mounted on the moving body.
This object detection device is
A drive control unit (71) that sets a frequency modulation mode within a predetermined frequency band in a drive signal that drives a transmission unit (40A) to transmit to the outside a transmission wave that is an ultrasonic wave encoded by frequency modulation;
a detection unit (73) that detects the object based on a reception signal corresponding to a reception result by a receiving unit (40B) of a reception wave including a reflected wave of the transmission wave by the object;
Equipped with
The detection unit has a determination unit (74) that determines a code included in the received wave based on a match between a reference signal corresponding to the drive signal and the received signal,
The drive control unit is
a code to be assigned to the drive signal is selected and set from a plurality of types of codes including at least a first code characterized by a frequency modulation mode in which the frequency increases over time in a first frequency band, a second code characterized by a frequency modulation mode in which the frequency increases over time in a second frequency band different from the first frequency band, a third code characterized by a frequency modulation mode in which the frequency decreases over time in a third frequency band, and a fourth code characterized by a frequency modulation mode in which the frequency decreases over time in a fourth frequency band different from the third frequency band;
When the start frequency of the drive signal is close to the center frequency of the transmitter, the start frequency is set to the opposite side of the center frequency of the transmitter from the end frequency of the drive signal;
When the end frequency of the drive signal is close to the center frequency of the transmitter, the end frequency is configured to be on the opposite side of the center frequency of the transmitter from the start frequency of the drive signal,
an upper limit frequency of the first frequency band is higher than an upper limit frequency of the second frequency band;
a lower limit frequency of the first frequency band is higher than a lower limit frequency of the second frequency band,
an upper limit frequency of the third frequency band is higher than an upper limit frequency of the fourth frequency band;
The lower limit frequency of the third frequency band is higher than the lower limit frequency of the fourth frequency band.
The object detection device (3) according to the sixth aspect is configured to detect an object (B) around a moving body (C) when mounted on the moving body.
This object detection device is
A drive control unit (71) that sets a frequency modulation mode within a predetermined frequency band in a drive signal that drives a transmission unit (40A) to transmit to the outside a transmission wave that is an ultrasonic wave encoded by frequency modulation;
a correction unit (72) that corrects a reference signal corresponding to the drive signal in accordance with a moving speed of the moving body;
a detection unit (73) that detects the object based on a reception signal corresponding to a reception result by a receiving unit (40B) of a reception wave including a reflected wave of the transmission wave by the object;
Equipped with
The detection unit has a determination unit (74) that determines a code included in the received wave based on a match between the reference signal and the received signal,
the drive control unit is configured to select and set, as a code to be assigned to the drive signal, any one of a plurality of types of codes including at least a first code characterized by a frequency modulation mode in which a frequency increases over time within a first frequency band, a second code characterized by a frequency modulation mode in which a frequency increases over time within a second frequency band different from the first frequency band, a third code characterized by a frequency modulation mode in which a frequency decreases over time within a third frequency band, and a fourth code characterized by a frequency modulation mode in which a frequency decreases over time within a fourth frequency band different from the third frequency band;
an upper limit frequency of the first frequency band is higher than an upper limit frequency of the second frequency band;
a lower limit frequency of the first frequency band is higher than a lower limit frequency of the second frequency band,
an upper limit frequency of the third frequency band is higher than an upper limit frequency of the fourth frequency band;
The lower limit frequency of the third frequency band is higher than the lower limit frequency of the fourth frequency band.
The object detection device (3) according to the ninth aspect is configured to detect an object (B) around a moving body (C) when mounted on the moving body.
This object detection device is
A drive control unit (71) that sets a frequency modulation mode within a predetermined frequency band in a drive signal that drives a transmission unit (40A) to transmit to the outside a transmission wave that is an ultrasonic wave encoded by frequency modulation;
a detection unit (73) that detects the object based on a reception signal corresponding to a reception result by a receiving unit (40B) of a reception wave including a reflected wave of the transmission wave by the object;
Equipped with
The detection unit has a determination unit (74) that determines a code included in the received wave based on a match between a reference signal corresponding to the drive signal and the received signal,
the drive control unit is configured to select and set, as a code to be assigned to the drive signal, any one of a plurality of types of codes including at least a first code characterized by a frequency modulation mode in which a frequency increases over time within a first frequency band, a second code characterized by a frequency modulation mode in which a frequency increases over time within a second frequency band different from the first frequency band, a third code characterized by a frequency modulation mode in which a frequency decreases over time within a third frequency band, and a fourth code characterized by a frequency modulation mode in which a frequency decreases over time within a fourth frequency band different from the third frequency band;
an upper limit frequency of the first frequency band is higher than an upper limit frequency of the second frequency band;
a lower limit frequency of the first frequency band is higher than a lower limit frequency of the second frequency band,
an upper limit frequency of the third frequency band is higher than an upper limit frequency of the fourth frequency band;
a lower limit frequency of the third frequency band is higher than a lower limit frequency of the fourth frequency band,
A plurality of the transmitting units are arranged in an arrangement direction that intersects with the direction of travel of the moving body, and among the plurality of the transmitting units, the transmitting unit that is currently driven by the drive control unit is designated as the self transmitting unit, and the other transmitting units different from the self transmitting unit are designated as other transmitting units.The drive control unit assigns a code different from that of the other transmitting units to the drive signal so that the frequency changes in a different direction from that of the adjacent other transmitting units.
The object detection device (3) according to the twelfth aspect is configured to detect an object (B) around a moving body (C) when mounted on the moving body.
This object detection device is
A drive control unit (71) that sets a frequency modulation mode within a predetermined frequency band in a drive signal that drives a transmission unit (40A) to transmit to the outside a transmission wave that is an ultrasonic wave encoded by frequency modulation;
a detection unit (73) that detects the object based on a reception signal corresponding to a reception result by a receiving unit (40B) of a reception wave including a reflected wave of the transmission wave by the object;
Equipped with
The detection unit has a determination unit (74) that determines a code included in the received wave based on a match between a reference signal corresponding to the drive signal and the received signal,
the drive control unit is configured to select and set, as a code to be assigned to the drive signal, any one of a plurality of types of codes including at least a first code characterized by a frequency modulation mode in which a frequency increases over time within a first frequency band, a second code characterized by a frequency modulation mode in which a frequency increases over time within a second frequency band different from the first frequency band, a third code characterized by a frequency modulation mode in which a frequency decreases over time within a third frequency band, and a fourth code characterized by a frequency modulation mode in which a frequency decreases over time within a fourth frequency band different from the third frequency band;
an upper limit frequency of the first frequency band is higher than an upper limit frequency of the second frequency band;
a lower limit frequency of the first frequency band is higher than a lower limit frequency of the second frequency band,
an upper limit frequency of the third frequency band is higher than an upper limit frequency of the fourth frequency band;
a lower limit frequency of the third frequency band is higher than a lower limit frequency of the fourth frequency band,
K transmitters are arranged in an arrangement direction intersecting with the traveling direction of the moving body, and among the plurality of transmitters, the transmitter currently driven by the drive control unit is defined as a local transmitter, and the other transmitters different from the local transmitter are defined as other transmitters. When a total of K transmissions in which each of the K transmitters transmits the transmission wave once in turn is defined as one cycle, the drive control unit assigns a different code to the drive signal that drives the local transmitter for each cycle,
When there are M types of codes that can be assigned to the drive signal, the drive control unit assigns M types of codes to the drive signal that drives the own transmission unit in M cycles.

In addition, in each section of the application documents, each element may be given a reference symbol in parentheses. However, such a reference symbol merely indicates an example of the correspondence between the element and the specific means described in the embodiment described below. Therefore, the present invention is not limited in any way by the description of the above reference symbols.

1 is a plan view showing a schematic configuration of a vehicle equipped with an in-vehicle system capable of detecting surrounding objects. 2 is a block diagram showing a schematic functional configuration of the in-vehicle system shown in FIG. 1 . 3 is a time chart showing frequency characteristics of a specific example of a drive signal that can be output by the drive signal generating unit shown in FIG. 2 . 4 is a vehicle plan view illustrating an example of driving a plurality of ultrasonic sensors using the driving signals illustrated in FIG. 3 . FIG. 4 is a graph showing frequency characteristics of a received signal corresponding to the drive signal shown in FIG. 3 . 4 is a graph showing amplitude characteristics of a received signal corresponding to the drive signal shown in FIG. 3 . 11 is a time chart showing frequency characteristics of a drive signal in a comparative example. 8 is a graph showing frequency characteristics and amplitude characteristics of a received signal corresponding to the drive signal of the comparative example shown in FIG. 7 . 8 is a graph showing frequency characteristics and amplitude characteristics of a received signal corresponding to the drive signal of the comparative example shown in FIG. 7 . 3 is a graph showing the effect of pulse compression processing by the reception signal processing unit shown in FIG. 2 . 3 is a time chart showing an overview of Doppler shift correction by the correction unit shown in FIG. 2 . 3 is a plan view of a vehicle illustrating an overview of Doppler shift correction performed by a correction unit shown in FIG. 2. 3 is a time chart showing frequency characteristics of another specific example of a drive signal that can be output by the drive signal generating unit shown in FIG. 2 . 14 is a graph showing frequency characteristics of a received signal corresponding to the drive signal shown in FIG. 13 . 4 is a time chart showing frequency characteristics in still another specific example of a drive signal that can be output by the drive signal generating unit shown in FIG. 2 . 16 is a graph showing frequency characteristics of a received signal corresponding to the drive signal shown in FIG. 15 . 4 is a time chart showing frequency characteristics in still another specific example of a drive signal that can be output by the drive signal generating unit shown in FIG. 2 . 4 is a time chart showing frequency characteristics in still another specific example of a drive signal that can be output by the drive signal generating unit shown in FIG. 2 . 10 is a vehicle plan view illustrating another driving example in which each of the ultrasonic sensors is driven using the drive signals illustrated in FIG. 3 and the like. FIG. 10 is a vehicle plan view illustrating another driving example in which each of the ultrasonic sensors is driven using the drive signals illustrated in FIG. 3 and the like. FIG. 10 is a vehicle plan view illustrating another driving example in which each of the ultrasonic sensors is driven using the drive signals illustrated in FIG. 3 and the like. FIG. 10 is a vehicle plan view illustrating another driving example in which each of the ultrasonic sensors is driven using the drive signals illustrated in FIG. 3 and the like. FIG.

(Embodiment)
Hereinafter, an embodiment of the present invention will be described with reference to the drawings. Note that various modified examples applicable to one embodiment may be hindered from understanding the embodiment if they are inserted in the middle of a series of explanations related to the embodiment. For this reason, the modified examples are described together after the explanation of the embodiment.

(Overall system configuration)
1, the in-vehicle system 1 is mounted on a vehicle C as a moving body. The vehicle C is a so-called four-wheeled automobile, and has a box-shaped body C1 formed in a substantially rectangular shape in a plan view. The shape of each part of the vehicle C in a "plan view" refers to the shape of that part when the vehicle C is stably placed on a horizontal surface so as to be able to run, and the part is viewed from the line of sight in the same direction as the direction of gravity. The vehicle C equipped with the in-vehicle system 1 according to this embodiment is hereinafter referred to as the "own vehicle."

Hereinafter, the imaginary straight line that passes through the center of the host vehicle in the vehicle width direction in a plan view and is parallel to the vehicle overall length direction of the host vehicle is referred to as the vehicle center line LC. The vehicle overall length direction is a direction perpendicular to the vehicle width direction and perpendicular to the vehicle height direction. The vehicle height direction is a direction that determines the height of the host vehicle and is a direction parallel to the direction of gravity when the host vehicle is stably placed on a horizontal surface so that it can be driven. In addition, "front," "rear," "left," "right," and "up" are defined as shown by the arrows in Figure 1. In other words, the vehicle overall length direction is synonymous with the front-rear direction. In addition, the vehicle width direction is synonymous with the left-right direction.

The vehicle system 1 includes an electronic control unit 2 and an ultrasonic sensor 3. The electronic control unit 2 is an in-vehicle microcomputer that may also be referred to as an ECU, and includes a CPU, ROM, RAM, non-volatile RAM, etc. (not shown). ECU stands for Electronic Control Unit. The non-volatile RAM is a storage device that allows information to be rewritten while the power is on, but retains information in a non-rewritable manner while the power is off, such as a flash ROM. The ROM, RAM, and non-volatile RAM are non-transient physical storage media. The electronic control unit 2 is designed to be mounted inside the vehicle body C1.

The electronic control unit 2 is connected to the ultrasonic sensor 3 via an on-board information communication line so that information can be transmitted and received. In this embodiment, the vehicle is equipped with multiple ultrasonic sensors 3. The electronic control unit 2 is configured to control the overall operation of the on-board system 1, including the timing of ultrasonic transmission and reception operations in each of the multiple ultrasonic sensors 3, by reading and executing a control program stored in a ROM or non-volatile RAM. In other words, the on-board system 1 is configured to detect an object B around the vehicle based on the results of ultrasonic transmission and reception in the ultrasonic sensor 3 while mounted in the vehicle.

The front bumper of the vehicle, i.e., the bumper C2 on the front side of the vehicle body C1, is equipped with a first front sensor 3A, a second front sensor 3B, a third front sensor 3C, and a fourth front sensor 3D as ultrasonic sensors 3. Similarly, the rear bumper of the vehicle, i.e., the bumper C2 on the rear side of the vehicle body C1, is equipped with a first rear sensor 3E, a second rear sensor 3F, a third rear sensor 3G, and a fourth rear sensor 3H as ultrasonic sensors 3.

The first front sensor 3A is provided at the right end of the front bumper so as to transmit a transmission wave to the right front of the vehicle. The second front sensor 3B is provided between the first front sensor 3A and the vehicle center line LC in the vehicle width direction so as to transmit a transmission wave approximately in front of the vehicle. The third front sensor 3C is provided at a position approximately symmetrical to the second front sensor 3B across the vehicle center line LC. The third front sensor 3C is provided between the vehicle center line LC and the fourth front sensor 3D in the vehicle width direction so as to transmit a transmission wave approximately in front of the vehicle. The fourth front sensor 3D is provided at a position approximately symmetrical to the first front sensor 3A across the vehicle center line LC. The fourth front sensor 3D is provided at the left end of the front bumper so as to transmit a transmission wave to the left front of the vehicle.

The first rear sensor 3E is provided at the right end of the rear bumper so as to transmit a transmission wave to the right rear of the vehicle. The second rear sensor 3F is provided between the first rear sensor 3E and the vehicle center line LC in the vehicle width direction so as to transmit a transmission wave to the approximately rear of the vehicle. The third rear sensor 3G is provided at a position approximately symmetrical to the second rear sensor 3F across the vehicle center line LC. The third rear sensor 3G is provided between the vehicle center line LC and the fourth rear sensor 3H in the vehicle width direction so as to transmit a transmission wave to the approximately rear of the vehicle. The fourth rear sensor 3H is provided at a position approximately symmetrical to the first rear sensor 3E across the vehicle center line LC. The fourth rear sensor 3H is provided at the left end of the rear bumper so as to transmit a transmission wave to the left rear of the vehicle.

(Ultrasonic sensor)
Hereinafter, a schematic configuration of the ultrasonic sensor 3 will be described with reference to Fig. 2. In Fig. 2, for the sake of simplicity, only one of the multiple ultrasonic sensors 3 connected to the electronic control device 2 is shown, and the others are omitted.

The ultrasonic sensor 3 is configured to transmit a transmission wave, which is an ultrasonic wave encoded by frequency modulation, toward the outside of the vehicle. The ultrasonic sensor 3 is also configured to receive a reception wave that includes a reflected wave of the transmitted transmission wave by an object B, thereby detecting an object B present in the vicinity and acquiring the distance to the object B.

Specifically, the ultrasonic sensor 3 includes a transmitter/receiver 4, a drive signal generator 5, a received signal processor 6, and a sensor controller 7. In this embodiment, the transmitter/receiver 4, drive signal generator 5, received signal processor 6, and sensor controller 7 are supported by a single sensor housing made of synthetic resin or the like.

In this embodiment, the ultrasonic sensor 3 has only one transmitter/receiver 4, and is configured to perform a transmission/reception function using the transmitter/receiver 4. That is, the transmitter/receiver 4 has a function as a transmitter 40A that transmits transmission waves to the outside, and a function as a receiver 40B that receives received waves. Specifically, one transmitter/receiver 4 has one transducer 41. The transmitter 40A and receiver 40B are configured to achieve the transmission function and the reception function, respectively, using the common transducer 41.

The transducer 41 is configured to function as a transmitter that transmits outgoing waves and as a receiver that receives reflected waves. The transducer 41 has a structure as a so-called resonant ultrasonic microphone that incorporates an electromechanical energy conversion element such as a piezoelectric element. Specifically, the transducer 41 is formed by joining an electromechanical energy conversion element to the bottom plate of a casing that is substantially cylindrical with a bottom. When the casing is mounted on the vehicle, it is inserted into a through hole C3 formed in the bumper C2, so that the transmitting/receiving surface 41a, which is the outer surface of the bottom plate that constitutes the diaphragm, faces the external space of the vehicle.

The transmitting/receiving unit 4 includes a transducer 41, a transmitting circuit 42, and a receiving circuit 43. That is, the transmitting unit 40A includes a transducer 41 and a transmitting circuit 42. The receiving unit 40B includes a transducer 41 and a receiving circuit 43. The transducer 41 is electrically connected to the transmitting circuit 42 and the receiving circuit 43.

The transmission circuit 42 is configured to drive the transducer 41 based on the input drive signal, thereby causing the transducer 41 to emit a transmission wave in the ultrasonic band. Specifically, the transmission circuit 42 has a digital/analog conversion circuit and the like. That is, the transmission circuit 42 is configured to perform processing such as digital/analog conversion on the drive signal output from the drive signal generation unit 5, and apply the AC voltage generated thereby to the transducer 41.

The receiving circuit 43 is configured to generate a receiving signal corresponding to the result of receiving the ultrasonic waves at the transducer 41, and to output the generated receiving signal to the receiving signal processing unit 6. Specifically, the receiving circuit 43 has an amplifier circuit and an analog/digital conversion circuit, etc. That is, the receiving circuit 43 is configured to perform signal processing such as amplification and analog/digital conversion on the voltage signal input from the transducer 41, thereby generating and outputting a receiving signal corresponding to the frequency and amplitude of the received ultrasonic waves.

In this way, the transmitter/receiver 4 is configured to generate a reception signal according to the distance to object B by transmitting a transmission wave and receiving a reflected wave of the transmission wave transmitted by the transducer 41 as a transmitter/receiver. The received wave when the transducer 41 as a transmitter/receiver receives a reflected wave of the transmission wave transmitted by itself is hereinafter referred to as a "regular wave". In contrast, the received wave caused by a transmission wave from another device is hereinafter referred to as an "irregular wave". "Other devices" include ultrasonic sensors 3 mounted on other vehicles different from the host vehicle, as well as other ultrasonic sensors 3 mounted on the host vehicle.

The drive signal generating unit 5 is configured to generate a drive signal that drives the transmitting unit 40A. The drive signal is a signal for driving the transmitting unit 40A to transmit a transmission wave from the transducer 41, and is, for example, a pulsed signal in the ultrasonic band. Specific examples of the drive signal will be described later. The drive signal generating unit 5 also outputs a reference signal corresponding to the drive signal to the received signal processing unit 6. The reference signal is a signal for comparison with the frequency characteristics in the received signal for code identification, and has frequency characteristics that correspond to the frequency characteristics of the drive signal.

The received signal processing unit 6 is configured to perform various signal processing including pulse compression processing on the received signal output from the receiving circuit 43, and to output the processing result signal generated by the signal processing to the sensor control unit 7. Specifically, the received signal processing unit 6 has a correlation filter (e.g., a matched filter) for performing correlation processing calculations between the received signal and a reference signal.

The sensor control unit 7 is communicatively connected to the electronic control unit 2 so as to cooperate with the electronic control unit 2 to control the operation of the ultrasonic sensor 3. That is, the sensor control unit 7 is configured to control the output of the drive signal from the drive signal generation unit 5 to the transmission unit 40A, and to detect the object B based on the processing result signal output from the reception signal processing unit 6.

The sensor control unit 7 is configured as an on-board microcomputer equipped with a CPU, ROM, RAM, non-volatile RAM, etc. (not shown), and is configured to control the operation of the ultrasonic sensor 3 by reading and executing a control program stored in the ROM or non-volatile RAM. Specifically, the sensor control unit 7 includes a drive control unit 71, a correction unit 72, and a detection unit 73 as functional components realized on the on-board microcomputer.

The drive control unit 71 is configured to control the emission state of the transmission wave from the transmitter 40A by outputting a control signal to the drive signal generation unit 5. The control signal is a signal for controlling the output characteristics of the drive signal output from the drive signal generation unit 5 to the transceiver unit 4, specifically, the output timing, frequency, number of pulses, etc. In other words, the drive control unit 71 is configured to control the output timing, frequency, number of pulses, etc. of the drive signal generated and output by the drive signal generation unit 5. The frequency of the drive signal may be referred to as the "drive frequency" below.

In this embodiment, the drive control unit 71 is configured to set the frequency modulation mode of the drive signal within a predetermined frequency band. In other words, the drive signal generation unit 5 is capable of selectively outputting one of multiple types of drive signals having different frequency bands and/or frequency modulation modes. Specific examples of multiple types of drive signals will be described later.

The correction unit 72 is configured to correct the reference signal (i.e., Doppler shift correction) in accordance with the moving speed of the host vehicle. Specifically, in this embodiment, the correction unit 72 corrects the reference signal in accordance with the moving speed of the host vehicle and the relative position of object B with respect to the host vehicle. The correction of the reference signal by the correction unit 72 will be described in detail later.

The detection unit 73 is configured to detect object B based on a received signal corresponding to the reception result by the receiving unit 40B of the received wave. Specifically, the detection unit 73 is configured to identify whether or not the received signal corresponds to a normal wave based on the processing result signal output from the received signal processing unit 6. Furthermore, when the received signal is a normal wave, the detection unit 73 is configured to calculate the distance to object B based on the propagation time.

The detection unit 73 has a determination unit 74 for identifying whether the received signal corresponds to a normal wave. The determination unit 74 is configured to determine the code contained in the received wave based on the coincidence between a reference signal corresponding to the drive signal and the received signal. Specifically, the determination unit 74 is adapted to determine the code based on a processing result signal that is the calculation result of the coincidence between the reference signal and the received signal after correction by the correction unit 72.

(Operation Overview)
An outline of the operation of the configuration of this embodiment will be described below with reference to Figures 1 to 4. In the following description, the device configuration, control method, and control program according to this embodiment may be simply referred to as "this embodiment."

Referring to FIG. 2, the drive control unit 71 outputs a control signal to the drive signal generation unit 5. The drive signal generation unit 5 then generates a drive signal based on the control signal and outputs the generated drive signal to the transmission unit 40A. The transmission unit 40A is driven by the drive signal. That is, the transmission circuit 42 excites the transducer 41 based on the input drive signal. As a result, a transmission wave is transmitted from the transducer 41, which functions as a transmitter, to the outside of the vehicle. The transmission wave is encoded by frequency modulation based on the drive signal.

The drive control unit 71 sets the code in the drive signal, i.e., the frequency modulation mode within a specified frequency band. Specifically, the drive control unit 71 selects one of multiple types of codes to be assigned to the drive signal. When transmitting a single transmission wave, it is possible to set a multi-bit code string in which multiple codes are arranged.

(Operation example 1)
3 shows a specific example of the drive signal. In this example, the drive signal generating section 5 can selectively output four types of drive signals, the first drive signal DS1 to the fourth drive signal DS4. "Selectively outputtable" means that in one drive signal generating section 5, while any one of the first drive signal DS1 to the fourth drive signal DS4 is being output, the other three are not output. Specifically, for example, in one drive signal generating section 5, while the first drive signal DS1 is being output, the second drive signal DS2 to the fourth drive signal DS4 are not output from the drive signal generating section 5. However, in the drive signal generating section 5, after the first drive signal DS1 is output, any one of the first drive signal DS1 to the fourth drive signal DS4 can be output again. The first drive signal DS1 to the fourth drive signal DS4 have different frequency bands and/or frequency modulation modes. The drive control unit 71 controls which of the first drive signal DS1 to the fourth drive signal DS4 the drive signal generating unit 5 outputs.

In the figure, the microphone center frequency fc is the center of a predetermined design transmission/reception frequency band fr0 for the transducer 41 as a transmitter/receiver, and is approximately the same as or close to the resonant frequency. The design transmission/reception frequency band fr0 is a range in which the sensitivity is 0 to Sb [dB] when the sensitivity at the microphone center frequency fc is 0 [dB]. In other words, the design transmission/reception frequency band fr0, which is a frequency range in which the transmitter 40A can transmit and receive signals well, is a frequency band between the design upper limit frequency fu and the design lower limit frequency fd, in which the sensitivity is 0 to Sb [dB]. Sb is typically, for example, -3 [dB]. The sensitivity is the sensitivity when the transducer 41 is used as a receiver. The microphone center frequency fc can also be called the "design center frequency."

The first frequency band fr1 is a frequency band corresponding to the first drive signal DS1. That is, the first drive signal DS1 has a frequency modulation pattern in which the frequency changes over time within the first frequency band fr1. Similarly, the second frequency band fr2 is a frequency band corresponding to the second drive signal DS2. The third frequency band fr3 is a frequency band corresponding to the third drive signal DS3. The fourth frequency band fr4 is a frequency band corresponding to the fourth drive signal DS4. In the figure, the center frequencies in each of the first frequency band fr1 to the fourth frequency band fr4 are indicated by circles. The center frequency in each of the first frequency band fr1 to the fourth frequency band fr4 is the median between the upper limit frequency and the lower limit frequency in each frequency band.

As shown in FIG. 3, the center frequency of the first frequency band fr1 is higher than the microphone center frequency fc. In this example, the lower limit frequency of the first frequency band fr1 is the microphone center frequency fc. The upper limit frequency of the first frequency band fr1 is the design upper limit frequency fu. In other words, the first frequency band fr1 is the higher frequency band when the design transmission/reception frequency band fr0 is divided in half by the microphone center frequency fc.

The first drive signal DS1 corresponds to the symbol UH. The symbol UH is characterized by a frequency modulation pattern in which the frequency increases over time within the first frequency band fr1. Specifically, the symbol UH corresponds to an "up chirp" in which the drive frequency increases linearly from the lower limit frequency to the upper limit frequency in the first frequency band fr1. In the symbol UH, "U" indicates "up chirp," and "H" indicates a frequency band higher than the microphone center frequency fc.

The center frequency of the second frequency band fr2 is lower than the microphone center frequency fc. In addition, the upper limit frequency of the second frequency band fr2 is lower than the upper limit frequency of the first frequency band fr1. Furthermore, the lower limit frequency of the second frequency band fr2 is lower than the lower limit frequency of the first frequency band fr1. In other words, the second frequency band fr2 is in a relationship in which the first frequency band fr1 is offset to the lower frequency side.

In this example, the lower limit frequency of the second frequency band fr2 is the design lower limit frequency fd. The upper limit frequency of the second frequency band fr2 is the microphone center frequency fc. In other words, the second frequency band fr2 is the lower frequency band when the design transmission/reception frequency band fr0 is divided in half by the microphone center frequency fc. In other words, the first frequency band fr1 and the second frequency band fr2 are obtained by dividing the design transmission/reception frequency band fr0 in half by the microphone center frequency fc.

The second drive signal DS2 corresponds to the symbol UL. The symbol UL is characterized by a frequency modulation mode in which the frequency increases over time in a second frequency band fr2 that is different from the first frequency band fr1. Specifically, the symbol UL corresponds to an "up chirp" in which the drive frequency increases linearly from the lower limit frequency to the upper limit frequency in the second frequency band fr2. In the symbol UL, "U" indicates "up chirp" and "L" indicates a frequency band lower than the microphone center frequency fc.

The center frequency of the third frequency band fr3 is higher than the microphone center frequency fc. In this example, the lower limit frequency of the third frequency band fr3 is the microphone center frequency fc. Furthermore, the upper limit frequency of the third frequency band fr3 is the design upper limit frequency fu. In other words, the third frequency band fr3 is the higher frequency band when the design transmission/reception frequency band fr0 is divided into two by the microphone center frequency fc. Furthermore, the third frequency band fr3 is the same as the first frequency band fr1. In other words, the first frequency band fr1 and the third frequency band fr3 have the same center frequency and frequency bandwidth.

The third drive signal DS3 corresponds to the symbol DH. The symbol DH is characterized by a frequency modulation pattern in which the frequency decreases over time within the third frequency band fr3. Specifically, the symbol DH corresponds to a "down chirp" in which the drive frequency increases linearly from the upper limit frequency to the lower limit frequency in the third frequency band fr3. In the symbol DH, "D" indicates "down chirp," and "H" indicates a frequency band higher than the microphone center frequency fc.

The center frequency of the fourth frequency band fr4 is lower than the microphone center frequency fc. The upper limit frequency of the fourth frequency band fr4 is lower than the upper limit frequency of the third frequency band fr3. The lower limit frequency of the fourth frequency band fr4 is lower than the lower limit frequency of the third frequency band fr3. In other words, the fourth frequency band fr4 is offset to the lower frequency side from the third frequency band fr3.

In this example, the lower limit frequency of the fourth frequency band fr4 is the design lower limit frequency fd. Furthermore, the upper limit frequency of the fourth frequency band fr4 is the microphone center frequency fc. In other words, the fourth frequency band fr4 is the lower frequency band when the design transmission/reception frequency band fr0 is divided in half by the microphone center frequency fc. In other words, the third frequency band fr3 and the fourth frequency band fr4 are obtained by dividing the design transmission/reception frequency band fr0 in half by the microphone center frequency fc. Furthermore, the fourth frequency band fr4 is the same as the second frequency band fr2.

The fourth drive signal DS4 corresponds to the symbol DL. The symbol DL is characterized by a frequency modulation pattern in which the frequency decreases over time in a fourth frequency band fr4 that is different from the third frequency band fr3. Specifically, the symbol DL corresponds to a "down chirp" in which the drive frequency increases linearly from the upper limit frequency to the lower limit frequency in the fourth frequency band fr4. In the symbol DL, "D" indicates "down chirp" and "L" indicates a frequency band lower than the microphone center frequency fc.

In this way, the drive control unit 71 selects and sets the code to be assigned to the drive signal from multiple types of codes, UH, UL, DH, and DL. As a result, the code to be set to a specific bit is selected from UH, UL, DH, and DL. Specifically, for example, a multi-bit code sequence of "UH, DL, UL, ..." can be generated. Then, a transmission wave that has been chirp frequency modulated corresponding to the code or code sequence set by the drive control unit 71 is transmitted from the transceiver unit 4.

Figure 4 shows a state in which the vehicle is detecting an obstacle ahead of the vehicle while the vehicle is traveling forward. As shown in Figure 4, when mounted on the vehicle, the first front sensor 3A to the fourth front sensor 3D are arranged in a vehicle width direction that intersects with the traveling direction of the vehicle.

Here, the "own sensor" and "other sensor" of the multiple ultrasonic sensors 3 arranged in the vehicle width direction, i.e., the first front sensor 3A to the fourth front sensor 3D, are defined as follows. The "own sensor" is one of the first front sensor 3A to the fourth front sensor 3D that is of interest. The "other sensor" is one of the first front sensor 3A to the fourth front sensor 3D that is different from the own sensor. Specifically, for example, when explaining the operation of the second front sensor 3B, the second front sensor 3B is the "own sensor", and the first front sensor 3A, the third front sensor 3C, and the fourth front sensor 3D are the "other sensors". The transducer 41 provided in the own sensor corresponds to the "own transmission unit", and the transducer 41 provided in the other sensor corresponds to the "other transmission unit". As is clear from the above definition, the "other sensor" is also mounted on the own vehicle, just like the "own sensor". In contrast, the ultrasonic sensor 3 mounted on a vehicle other than the vehicle itself will be referred to as a "sensor mounted on another vehicle" below to distinguish it from an "other sensor." The above-mentioned "other device" is a collective term for "other sensors" and "sensors mounted on another vehicle."

In this embodiment, the drive control unit 71 in each of the first front sensor 3A to the fourth front sensor 3D cooperates with the electronic control unit 2 to assign a different code to the drive signal in the sensor so that the frequency changes in a different direction from the other adjacent sensors. That is, for example, as shown in FIG. 4, the codes in the first front sensor 3A to the fourth front sensor 3D are DH, UH, DL, and UL, respectively. As a result, the sensor and the other adjacent sensors are a combination of up-chirp and down-chirp. Specifically, the first front sensor 3A and the second front sensor 3B, which are adjacent to each other, have different chirp directions, that is, different directions of frequency change over time. Similarly, the second front sensor 3B has different chirp directions from the first front sensor 3A and the third front sensor 3C adjacent to it. Also, the third front sensor 3C has different chirp directions from the second front sensor 3B and the fourth front sensor 3D adjacent to it. Additionally, the chirp directions of the third front sensor 3C and the fourth front sensor 3D, which are adjacent to each other, are different.

(effect)
Hereinafter, the effects achieved by this embodiment and the above-mentioned operation example will be described with reference to FIGS.

As shown in FIG. 4, in this embodiment, the first front sensor 3A to the fourth front sensor 3D, which are multiple ultrasonic sensors 3 provided on the same surface of the vehicle body C1 (i.e., the front surface in the above example) and arranged in the vehicle width direction, are driven with different drive signals. As a result, the first front sensor 3A to the fourth front sensor 3D transmit and receive transmission waves encoded with different codes. In particular, the chirp directions are different between adjacent sensors, where interference is most likely to occur. Therefore, this embodiment improves interference resistance.

Figure 5 shows the frequency characteristics of the received signal, i.e., the reflected signal, corresponding to each code. In the figure, a linear waveform corresponding to the frequency characteristics of the drive signal is shown by a dashed line. Such dashed waveform corresponds to the reference signal before Doppler shift correction is performed by the correction unit 72. The Doppler shift correction by the correction unit 72 will be described later. Figure 6 shows the amplitude waveform of the received signal corresponding to each code.

7 to 9 show an example using the first comparison drive signal DSu and the second comparison drive signal DSd, whose frequencies change over the entire range of the design transmission/reception frequency band fr0, as a comparative example. FIG. 7 shows the frequency characteristics of the first comparison drive signal DSu and the second comparison drive signal DSd. The first comparison drive signal DSu has a frequency modulation mode in which the drive frequency increases linearly from the design lower limit frequency fd to the design upper limit frequency fu, and corresponds to the symbol UP. The symbol UP indicates "up chirp". The second comparison drive signal DSd has a frequency modulation mode in which the drive frequency decreases linearly from the design upper limit frequency fu to the design lower limit frequency fd, and corresponds to the symbol DN. The symbol DN indicates "down chirp". FIG. 8 shows the frequency characteristics and amplitude waveform of the received signal corresponding to the first comparison drive signal DSu. FIG. 9 shows the frequency characteristics and amplitude waveform of the received signal corresponding to the second comparison drive signal DSd. In FIG. 8 and FIG. 9, the linear waveforms corresponding to the frequency characteristics of the drive signal or the reference signal before Doppler shift correction are shown by dashed lines.

Figure 10 shows the effect of pulse compression by the received signal processing unit 6. (a) in Figure 10 shows the intensity characteristics of the received signal when no pulse compression processing is performed. As shown in this figure, the peak of the received signal drops due to interference between multiple reflected waves, shown by the dashed lines. In contrast, (b) in Figure 10 shows the intensity characteristics of the received signal when pulse compression processing is performed by the received signal processing unit 6. As shown in this figure, pulse compression shortens the signal width and suppresses the drop in the peak. This achieves a certain degree of good code identification and reduced interference between reflected waves.

However, when detecting an obstacle using ultrasonic waves, there is a problem that received waves resulting from transmitted waves from another device may be mistakenly detected as received waves resulting from transmitted waves from the vehicle's own sensor. In response to this problem, technology has been proposed to reduce the risk of interference by encoding signals using FSK (Frequency Shift Keying) or the like (see, for example, Patent Document 1, etc.). By using such conventional technology, the risk of interference can be reduced by assigning a unique code to each of the multiple ultrasonic sensors 3 mounted on the vehicle.

However, when the ultrasonic sensor 3 mounted on the vehicle faces a wall or pole, the reflected waves from the base and the front overlap. The inventors discovered that when using an encoding method such as FSK to detect an obstacle with the ultrasonic sensor 3, in a scene where the reflected waves overlap like this, it becomes difficult to distinguish the codes due to interference between the reflected waves.

Specifically, for example, a situation is assumed in which a transmission wave having a three-bit code of "101" is transmitted from a sensor facing a wall or a pole. In this three-bit code, "1" corresponds to "UP" and "0" corresponds to "DN". In such a situation, there is a concern that an error in identifying the code will occur due to interference between the second bit of the code "0" in the front reflected wave, i.e., "DN", and the first bit of the code "1" in the root reflected wave, i.e., "UP". In particular, unlike radar that uses radio wave transmission and reception, in ultrasonic sensors 3 that use ultrasonic transmission and reception by transducers 41 that are resonant ultrasonic microphones, it is difficult to restore the code when interference occurs. For this reason, in object detection using this type of ultrasonic sensor 3, a technology is required that allows good code identification even when interference occurs between reflected waves, and that increases the number of codes.

In this regard, the inventors have discovered that by setting the sweep frequency band of the drive signal to a high frequency side and a low frequency side based on the microphone center frequency fc, and combining this with the chirp direction, multi-coding in one bit can be realized. Specifically, when N frequency bands are set within the design transmission/reception frequency band fr0 and two chirp directions, up chirp and down chirp, are used, "N x 2" types of codes can be used per bit (for example, N = 2 in the example of Figure 3). In this embodiment, such multi-coding and pulse compression enable good code identification even if interference occurs between reflected waves. Therefore, according to this embodiment, it is possible to provide an object detection device with even improved code identification performance.

Figures 11 and 12 show an overview of Doppler shift correction by the correction unit 72. When the relative speed between the vehicle and object B is high, Doppler shift becomes a problem. When Doppler shift occurs, as shown in Figure 11 (a), even if the wave is normal, a mismatch occurs between the received signal and the reference signal, making it impossible to recognize the code. In particular, the configuration of this embodiment has unique issues such as being susceptible to the effects of Doppler shift and the positional relationship in the lateral direction (i.e., the vehicle width direction) associated with directivity.

The correction unit 72 corrects the reference signal as shown in FIG. 11(b) according to the moving speed, i.e., vehicle speed, of the host vehicle. Specifically, referring to FIG. 12, the relative position coordinates B (X, Y) of the object B with respect to the host vehicle can be calculated based on the distance measurement results obtained using two ultrasonic sensors 3 (for example, the first front sensor 3A and the second front sensor 3B in the example of FIG. 12). Based on the relative position coordinates B (X, Y) and the vehicle speed vector V of the host vehicle, the relative velocity vectors V1, V2 between each of the two ultrasonic sensors 3 and the object B are calculated. Based on the relative velocity vectors V1, V2, the correction amount of the reference signal can be calculated.

(Operation example 2)
Fig. 13 shows another specific example of the drive signal. Fig. 14 shows the frequency characteristics of the received signal, i.e., the reflected signal, corresponding to each symbol shown in Fig. 13. In the following description of the operation example, the same symbols are used for parts that are the same as or equivalent to those in the above operation example 1. Therefore, in the following description of the operation example, for elements having the same symbols as those in the above operation example 1, the description in the above operation example 1 may be used as appropriate unless there is a technical contradiction or special additional explanation. The same applies to the other operation examples described below.

In this example, the drive signal generating unit 5 can selectively output the first drive signal DS1 to the fourth drive signal DS4, which are four types of drive signals with different frequency bands and/or frequency modulation modes. In other words, the drive control unit 71 controls which of the first drive signal DS1 to the fourth drive signal DS4 the drive signal generating unit 5 outputs.

The transducer 41 stably vibrates ultrasonically at the resonant frequency or at the microphone center frequency fc, which is a frequency close to the resonant frequency. Therefore, once the transducer 41 is excited at a frequency close to the microphone center frequency fc, the vibration frequency is difficult to change from that frequency. Therefore, at frequencies close to the microphone center frequency fc, the frequency of the reflected wave is difficult to change. In this regard, by sweeping the drive frequency so as to cross the microphone center frequency fc when transmitting the transmission wave, it is possible to widen the frequency band of the received signal.

Therefore, in this example, the drive control unit 71 causes a first frequency band fr1, whose center frequency is higher than the microphone center frequency fc, and a second frequency band fr2, whose center frequency is lower than the microphone center frequency fc, to overlap partially near the microphone center frequency fc. Specifically, the lower limit frequency of the first frequency band fr1 is lower than the microphone center frequency fc. Meanwhile, the upper limit frequency of the first frequency band fr1 is the design upper limit frequency fu. In contrast, the upper limit frequency of the second frequency band fr2 is higher than the microphone center frequency fc. Meanwhile, the lower limit frequency of the second frequency band fr2 is the design lower limit frequency fd.

Similarly, the drive control unit 71 partially overlaps the third frequency band fr3, whose center frequency is higher than the microphone center frequency fc, with the fourth frequency band fr4, whose center frequency is lower than the microphone center frequency fc, near the microphone center frequency fc. Specifically, the lower limit frequency of the third frequency band fr3 is lower than the microphone center frequency fc. Meanwhile, the upper limit frequency of the third frequency band fr3 is the design upper limit frequency fu. In contrast, the upper limit frequency of the fourth frequency band fr4 is higher than the microphone center frequency fc. Meanwhile, the lower limit frequency of the fourth frequency band fr4 is the design lower limit frequency fd. Also, in this example, the first frequency band fr1 and the third frequency band fr3 are the same, and the second frequency band fr2 and the fourth frequency band fr4 are the same.

In other words, in this example, when the start frequency of the drive signal is close to the microphone center frequency fc, the drive control unit 71 sets the start frequency to the opposite side of the microphone center frequency fc to the end frequency of the drive signal. On the other hand, when the end frequency of the drive signal is close to the microphone center frequency fc, the drive control unit 71 sets the end frequency to the opposite side of the microphone center frequency fc to the start frequency of the drive signal. This makes it possible to increase the frequency band in the received signal, thereby improving the identification performance.

(Operation example 3)
Fig. 15 shows yet another specific example of the drive signal. Fig. 16 shows the frequency characteristics of the received signal, i.e., the reflected signal, corresponding to each symbol shown in Fig. 15.

When performing "N x 2" types of multi-coding per bit by combining N frequency bands set within the design transmission/reception frequency band fr0 with two types of chirp directions, up-chirp and down-chirp, it is preferable that there is no difference in discrimination performance between the multiple types of codes. In other words, if the discrimination ability of a certain code is too high or too low compared to the discrimination ability of other codes, this leads to a decrease in overall discrimination performance.

The transducer 41, which is a resonant ultrasonic microphone, stably vibrates ultrasonically at the microphone center frequency fc, which is the resonant frequency or a frequency close to the resonant frequency. Therefore, once the transducer 41 is excited at a frequency close to the microphone center frequency fc, it becomes difficult to change the vibration frequency from that frequency. In other words, the ease of sweeping the frequency of the actual transmission wave differs depending on the sweep mode of the drive frequency. Therefore, in this example, the drive control unit 71 sets the frequency band and/or the number of pulses in the drive signal so as to suppress the difference in frequency bandwidth in the received wave between multiple codes.

Specifically, in this example, the drive control unit 71 increases the frequency band and the number of pulses in the first drive signal DS1 (i.e., symbol UH) and the fourth drive signal DS4 (i.e., symbol DL), which are characterized by a frequency sweep in which the drive frequency moves away from the microphone center frequency fc over time, as shown in FIG. 15. The dashed lines in FIG. 15 indicate the state before the frequency band and the number of pulses are increased. On the other hand, the drive control unit 71 does not increase the frequency band and the number of pulses in the second drive signal DS2 (i.e., symbol UL) and the third drive signal DS3 (i.e., symbol DH), which are characterized by a frequency sweep in which the drive frequency changes toward the microphone center frequency fc over time.

In this way, in this example, the code determines whether the drive frequency band crosses the microphone center frequency fc. Also, in this example, the code determines the number of pulses in the drive signal. This makes it possible to improve the overall discrimination performance by making the discrimination performance between multiple types of codes as uniform as possible.

(Operation example 4)
17 shows yet another specific example of the drive signal. In the above operation examples 1 to 3, the combination of two frequency bands set within the design transmission/reception frequency band fr0 and two types of chirp encoding, up-chirp and down-chirp, allows for "2 x 2" types of multi-encoding per bit. In contrast, this example allows for "4 x 2" types of multi-encoding per bit by combining four frequency bands set within the design transmission/reception frequency band fr0 and two types of chirp encoding, up-chirp and down-chirp.

In the figure, the upper intermediate frequency fmu is the frequency that is intermediate, or the median, between the microphone center frequency fc and the design upper limit frequency fu. The lower intermediate frequency fmd is the frequency that is intermediate, or the median, between the microphone center frequency fc and the design lower limit frequency fd.

Specifically, in this example, the drive control unit 71 controls which of the first drive signal DS1 to the eighth drive signal DS8 the drive signal generation unit 5 outputs. The first drive signal DS1 to the eighth drive signal DS8 have different frequency bands and/or frequency modulation modes. The first frequency band fr1 to the eighth frequency band fr8 are frequency bands that correspond to the first drive signal DS1 to the eighth drive signal DS8, respectively.

The center frequency of the first frequency band fr1 is higher than the microphone center frequency fc. In this example, the lower limit frequency of the first frequency band fr1 is the microphone center frequency fc. Also, the upper limit frequency of the first frequency band fr1 is the upper intermediate frequency fmu. The first drive signal DS1 corresponds to the symbol UH1. The symbol UH1 is characterized by a frequency modulation mode in which the frequency increases over time within the first frequency band fr1. Specifically, the symbol UH1 corresponds to an "up-chirp" in which the drive frequency increases linearly from the lower limit frequency to the upper limit frequency in the first frequency band fr1.

The center frequency of the second frequency band fr2 is lower than the microphone center frequency fc. In addition, the upper limit frequency of the second frequency band fr2 is lower than the upper limit frequency of the first frequency band fr1. Furthermore, the lower limit frequency of the second frequency band fr2 is lower than the lower limit frequency of the first frequency band fr1. In other words, the second frequency band fr2 corresponds to the first frequency band fr1 offset to the lower frequency side.

In this example, the lower limit frequency of the second frequency band fr2 is the lower intermediate frequency fmd. The upper limit frequency of the second frequency band fr2 is the microphone center frequency fc. The second drive signal DS2 corresponds to the symbol UL1. The symbol UL1 is characterized by a frequency modulation mode in which the frequency increases over time within the second frequency band fr2. Specifically, the symbol UL1 corresponds to an "up chirp" in which the drive frequency increases linearly from the lower limit frequency to the upper limit frequency in the second frequency band fr2.

The center frequency of the third frequency band fr3 is higher than the microphone center frequency fc. In this example, the lower limit frequency of the third frequency band fr3 is the microphone center frequency fc. The upper limit frequency of the third frequency band fr3 is the upper intermediate frequency fmu. The third drive signal DS3 corresponds to the symbol DH1. The symbol DH1 is characterized by a frequency modulation mode in which the frequency decreases over time within the third frequency band fr3. Specifically, the symbol DH1 corresponds to a "down chirp" in which the drive frequency increases linearly from the upper limit frequency to the lower limit frequency in the third frequency band fr3.

The center frequency of the fourth frequency band fr4 is lower than the microphone center frequency fc. In addition, the upper limit frequency of the fourth frequency band fr4 is lower than the upper limit frequency of the third frequency band fr3. Furthermore, the lower limit frequency of the fourth frequency band fr4 is lower than the lower limit frequency of the third frequency band fr3. In other words, the fourth frequency band fr4 corresponds to the third frequency band fr3 offset toward the lower frequency side.

In this example, the lower limit frequency of the fourth frequency band fr4 is the lower intermediate frequency fmd. The upper limit frequency of the fourth frequency band fr4 is the microphone center frequency fc. The fourth drive signal DS4 corresponds to the symbol DL1. The symbol DL1 is characterized by a frequency modulation mode in which the frequency decreases over time within the fourth frequency band fr4. Specifically, the symbol DL1 corresponds to a "down chirp" in which the drive frequency increases linearly from the upper limit frequency to the lower limit frequency in the fourth frequency band fr4.

The center frequency of the fifth frequency band fr5 is higher than the microphone center frequency fc. In this example, the lower limit frequency of the fifth frequency band fr5 is the upper intermediate frequency fmu. The upper limit frequency of the fifth frequency band fr5 is the design upper limit frequency fu. The fifth drive signal DS5 corresponds to the symbol UH2. The symbol UH2 is characterized by a frequency modulation mode in which the frequency increases over time within the fifth frequency band fr5. Specifically, the symbol UH2 corresponds to an "up chirp" in which the drive frequency increases linearly from the lower limit frequency to the upper limit frequency in the fifth frequency band fr5.

The upper limit frequency of the fifth frequency band fr5 is higher than the upper limit frequency of the first frequency band fr1. Also, the lower limit frequency of the fifth frequency band fr5 is higher than the lower limit frequency of the first frequency band fr1. In other words, the fifth frequency band fr5 corresponds to the first frequency band fr1 offset to the higher frequency side.

The center frequency of the sixth frequency band fr6 is lower than the microphone center frequency fc. In this example, the lower limit frequency of the sixth frequency band fr6 is the design lower limit frequency fd. The upper limit frequency of the sixth frequency band fr6 is the lower intermediate frequency fmd. The sixth drive signal DS6 corresponds to the symbol UL2. The symbol UL2 is characterized by a frequency modulation mode in which the frequency increases over time within the sixth frequency band fr6. Specifically, the symbol UL2 corresponds to an "up chirp" in which the drive frequency increases linearly from the lower limit frequency to the upper limit frequency in the sixth frequency band fr6.

The upper limit frequency of the sixth frequency band fr6 is lower than the upper limit frequency of the second frequency band fr2. The lower limit frequency of the sixth frequency band fr6 is lower than the lower limit frequency of the second frequency band fr2. In other words, the sixth frequency band fr6 is equivalent to the second frequency band fr2 offset to the lower frequency side.

The center frequency of the seventh frequency band fr7 is higher than the microphone center frequency fc. In this example, the lower limit frequency of the seventh frequency band fr7 is the upper intermediate frequency fmu. The upper limit frequency of the seventh frequency band fr7 is the design upper limit frequency fu. The seventh drive signal DS7 corresponds to the symbol DH2. The symbol DH2 is characterized by a frequency modulation mode in which the frequency decreases over time within the seventh frequency band fr7. Specifically, the symbol DH2 corresponds to a "down chirp" in which the drive frequency increases linearly from the upper limit frequency to the lower limit frequency in the seventh frequency band fr7.

The upper limit frequency of the seventh frequency band fr7 is higher than the upper limit frequency of the third frequency band fr3. Also, the lower limit frequency of the seventh frequency band fr7 is higher than the lower limit frequency of the third frequency band fr3. In other words, the seventh frequency band fr7 is equivalent to the third frequency band fr3 offset toward the higher frequency side.

The center frequency of the eighth frequency band fr8 is lower than the microphone center frequency fc. In this example, the lower limit frequency of the eighth frequency band fr8 is the lower design limit frequency fd. The upper limit frequency of the eighth frequency band fr8 is the lower intermediate frequency fmd. The eighth drive signal DS8 corresponds to the symbol DL2. The symbol DL2 is characterized by a frequency modulation mode in which the frequency decreases over time within the eighth frequency band fr8. Specifically, the symbol DL2 corresponds to a "down chirp" in which the drive frequency increases linearly from the upper limit frequency to the lower limit frequency in the eighth frequency band fr8.

The upper limit frequency of the eighth frequency band fr8 is lower than the upper limit frequency of the fourth frequency band fr4. Also, the lower limit frequency of the eighth frequency band fr8 is lower than the lower limit frequency of the fourth frequency band fr4. In other words, the eighth frequency band fr8 corresponds to the fourth frequency band fr4 offset toward the lower frequency side.

In this example, the first frequency band fr1 is the same as the third frequency band fr3. The second frequency band fr2 is the same as the fourth frequency band fr4. The fifth frequency band fr5 is the same as the seventh frequency band fr7. The sixth frequency band fr6 is the same as the eighth frequency band fr8. Furthermore, the first frequency band fr1, the second frequency band fr2, the fifth frequency band fr5, and the sixth frequency band fr6 are the respective bands obtained when the design transmission/reception frequency band fr0 is divided into four. Similarly, the third frequency band fr3, the fourth frequency band fr4, the seventh frequency band fr7, and the eighth frequency band fr8 are the respective bands obtained when the design transmission/reception frequency band fr0 is divided into four.

In this example, four frequency bands are set within the design transmission/reception frequency band fr0, and two chirp directions, up-chirp and down-chirp, are used, making it possible to use "4 x 2" types of codes per bit. This further increases the number of code types that can be set per bit, thereby enabling good code identification.

(Operation example 5)
Fig. 18 shows yet another specific example of the drive signal. This example corresponds to the introduction of the method of operation example 3 shown in Fig. 15 to operation example 5 shown in Fig. 17. That is, this example is intended to equalize the identifiability of the eight types of codes UH1 to DL2.

In the ultrasonic sensor 3 that uses the transducer 41, which is a resonant ultrasonic microphone, to transmit and receive ultrasonic waves, when driven at a drive frequency far from the microphone center frequency fc, the transmission efficiency is lower than when driven at the microphone center frequency fc or a drive frequency close to it. Therefore, in this example, the drive control unit 71 increases the frequency band and/or the number of pulses in the drive signal the more the code corresponding to the frequency band farther away from the microphone center frequency fc.

Specifically, in this example, the drive control unit 71 increases the frequency band and/or the number of pulses in the fifth drive signal DS5 to the eighth drive signal DS8 corresponding to the fifth frequency band fr5 to the eighth frequency band fr8, which are further away from the microphone center frequency fc, from the example in FIG. 17 (i.e., see the dashed line in FIG. 18) among the first frequency band fr1 to the eighth frequency band fr8. In contrast, the drive control unit 71 sets the frequency band and the number of pulses in the first drive signal DS1 to the fourth drive signal DS4 corresponding to the first frequency band fr1 to the fourth frequency band fr4 to the same as in the example in FIG. 17.

In this way, in this example, the drive frequency band and the number of pulses in the drive signal are set depending on the code. This makes it possible to equalize the discrimination performance between multiple types of codes as much as possible, thereby improving the overall discrimination performance.

(Operation example 6)
19A to 19D, like FIG. 4, show an example of driving the plurality of ultrasonic sensors 3, ie, the first front sensor 3A to the fourth front sensor 3D, arranged in the vehicle width direction on the front side of the vehicle body C1.

In this embodiment, the first front sensor 3A to the fourth front sensor 3D perform transmission and reception operations at a predetermined time period. Here, a total of four transmissions and receptions, in which each of the first front sensor 3A to the fourth front sensor 3D performs transmission and reception once, are referred to as "one cycle." That is, in this embodiment, the second front sensor 3B performs transmission and reception operations at the cycle start time t1, the third front sensor 3C performs transmission and reception operations at the intermediate time t2, and the first front sensor 3A and the fourth front sensor 3D perform transmission and reception operations at the cycle end time t3. "One cycle" is the period from the transmission of the transmission wave at the cycle start time t1 to the end of the reception process corresponding to the transmission of the transmission wave at the cycle end time t3. The cycle start time t1 arrives repeatedly at a predetermined time period while the operating condition of the in-vehicle system 1, i.e., the obstacle detection condition, is satisfied.

As shown in Figures 19A to 19D, in this embodiment, a first front sensor 3A to a fourth front sensor 3D, which are multiple ultrasonic sensors 3 arranged in the vehicle width direction on the same surface of the vehicle body C1 (i.e., the front surface in the example of Figures 19A to 19D), are driven with different drive signals each corresponding to a different code during one cycle. At this time, this embodiment assigns a code different from that of other sensors to the drive signal of the sensor itself so that the frequency changes in a different direction from that of other adjacent sensors. Furthermore, this embodiment assigns a different code to the drive signal that drives the sensor itself for each cycle.

In this example, as shown in FIG. 3, FIG. 13, or FIG. 15, there are four types of codes that can be assigned to the drive signal. In this case, in this embodiment, four types of codes are assigned to the drive signal that drives the local sensor in four cycles.

Specifically, in this embodiment, as shown in FIG. 19A, in the first cycle, the sign of the transmission wave from the second front sensor 3B, which is driven at the cycle start time t1, is set to UH. The sign of the transmission wave from the third front sensor 3C, which is driven at the intermediate time t2, is set to DL. And the signs of the transmission waves from the first front sensor 3A and the fourth front sensor 3D, which are driven at the cycle end time t3, are set to DH and UL, respectively.

In this embodiment, as shown in FIG. 19B, in the second cycle, the sign of the transmission wave from the second front sensor 3B, which is driven at the cycle start time t1, is DL. The sign of the transmission wave from the third front sensor 3C, which is driven at the intermediate time t2, is UH. And the signs of the transmission waves from the first front sensor 3A and the fourth front sensor 3D, which are driven at the cycle end time t3, are UL and DH, respectively.

In this embodiment, as shown in FIG. 19C, in the third cycle, the sign of the transmission wave from the second front sensor 3B, which is driven at the cycle start time t1, is set to UL. The sign of the transmission wave from the third front sensor 3C, which is driven at the intermediate time t2, is set to DH. And the signs of the transmission waves from the first front sensor 3A and the fourth front sensor 3D, which are driven at the cycle end time t3, are set to DL and UH, respectively.

In addition, in this embodiment, as shown in FIG. 19D, in the fourth cycle, the sign of the transmission wave from the second front sensor 3B, which is driven at the cycle start time t1, is set to DH. The sign of the transmission wave from the third front sensor 3C, which is driven at the intermediate time t2, is set to UL. And the signs of the transmission waves from the first front sensor 3A and the fourth front sensor 3D, which are driven at the cycle end time t3, are set to UH and DL, respectively.

According to this embodiment, by assigning a unique code to each of the multiple ultrasonic sensors 3 mounted on the vehicle, the risk of interference within the vehicle can be reduced. In addition, by changing the code transmitted by one ultrasonic sensor 3 for each transmission, the risk of interference with sensors mounted on other vehicles can be reduced. Therefore, according to this embodiment, good code identification is possible.

(Modification)
The present invention is not limited to the above embodiment. Therefore, the above embodiment can be modified as appropriate. Representative modified examples will be described below. In the following description of the modified examples, differences from the above embodiment will be mainly described. In addition, the same reference numerals are used for parts that are the same or equivalent to each other in the above embodiment and the modified examples. Therefore, in the following description of the modified examples, the description of the above embodiment can be appropriately used for components having the same reference numerals as the above embodiment, unless there is a technical contradiction or special additional explanation.

All or part of the electronic control unit 2 may be configured with a digital circuit, such as an ASIC or FPGA, configured to enable the above-mentioned operations. ASIC stands for Application Specific Integrated Circuit. FPGA stands for Field Programmable Gate Array. In other words, in the electronic control unit 2, the on-board microcomputer portion and the digital circuit portion may coexist.

The electronic control device 2 and the ultrasonic sensor 3 are not limited to being mounted on an automobile, i.e., on a vehicle. That is, for example, the electronic control device 2 and the ultrasonic sensor 3 may be mounted on a ship or an aircraft.

The ultrasonic sensor 3 is not limited to a configuration capable of transmitting and receiving ultrasonic waves using a single transducer 41 as shown in FIG. 2. That is, for example, a transmitting transducer 41 electrically connected to a transmitting circuit 42 and a receiving transducer 41 electrically connected to a receiving circuit 43 may be provided in parallel.

The configuration of each part, such as the transmission circuit 42 and the reception circuit 43, is not limited to the specific example shown in the above embodiment. That is, for example, the digital/analog conversion circuit may be provided in the drive signal generation unit 5 instead of the transmission circuit 42. Also, the transmission circuit 42 may be integrated with the drive signal generation unit 5. Similarly, the reception circuit 43 may be integrated with the reception signal processing unit 6.

All or part of the functional components in the sensor control unit 7 may be provided in the electronic control unit 2. In other words, the object detection device according to the present invention may be configured with at least one of the electronic control unit 2 and the ultrasonic sensor 3.

All or part of the sensor control unit 7 may be configured with a digital circuit, such as an ASIC or FPGA, configured to enable the above-mentioned operations. ASIC stands for Application Specific Integrated Circuit. FPGA stands for Field Programmable Gate Array. In other words, in the sensor control unit 7, the on-board microcomputer part and the digital circuit part may coexist.

The program according to the present invention, which enables the execution of various operations, procedures, or processes described in the above embodiment, can be downloaded or upgraded via V2X communication. V2X is an abbreviation for Vehicle to X. Alternatively, such a program can be downloaded or upgraded via a terminal device provided in a manufacturing plant, a maintenance plant, a dealer, etc. of the vehicle C. Such a program can be stored on a memory card, an optical disk, a magnetic disk, etc.

In this way, each of the above functional configurations and methods may be realized by a dedicated computer provided by configuring a processor and memory programmed to execute one or more functions embodied in a computer program. Alternatively, each of the above functional configurations and methods may be realized by a dedicated computer provided by configuring a processor with one or more dedicated hardware logic circuits. Alternatively, each of the above functional configurations and methods may be realized by one or more dedicated computers configured by combining a processor and memory programmed to execute one or more functions with a processor configured with one or more hardware logic circuits. Furthermore, the computer program may be stored in a computer-readable non-transitive tangible storage medium as instructions executed by the computer. In other words, each of the above functional configurations and methods can be expressed as a computer program including procedures for realizing it, or as a non-transitive tangible storage medium storing the program.

The present invention is not limited to the specific functional configurations and operational examples shown in the above embodiments. That is, for example, in FIG. 3, the lower limit frequency of the first frequency band fr1 may be near the microphone center frequency fc, the upper limit frequency of the second frequency band fr2 may be near the microphone center frequency fc, the lower limit frequency of the third frequency band fr3 may be near the microphone center frequency fc, and the upper limit frequency of the fourth frequency band fr4 may be near the microphone center frequency fc.

In FIG. 3, the first frequency band fr1 and the third frequency band fr3 may be different. That is, the center frequency and/or the frequency bandwidth may be different between the first frequency band fr1 and the third frequency band fr3. Similarly, the second frequency band fr2 and the fourth frequency band fr4 do not have to be the same.

In FIG. 13, the first frequency band fr1 and the third frequency band fr3 may be the same or different. That is, the center frequency and/or frequency bandwidth may be different between the first frequency band fr1 and the third frequency band fr3. Similarly, the second frequency band fr2 and the fourth frequency band fr4 may be the same or different. The same applies to FIG. 17.

The second drive signal DS2 and the third drive signal DS3 in FIG. 15 can be replaced with those in FIG. 3.

In FIG. 17, the fifth frequency band fr5 and the seventh frequency band fr7 may be different. Similarly, the sixth frequency band fr6 and the eighth frequency band fr8 may be different.

The frequency change may not be linear, but may be curved. The frequency change may not be monotonically increasing or decreasing. That is, for example, referring to FIG. 13, the first drive signal DS1 corresponding to the symbol UH may have a frequency characteristic in which the drive frequency slightly drops from the microphone center frequency fc and then rises to the design upper limit frequency fu. Such a frequency modulation mode is also generally characterized by a frequency modulation mode in which the frequency rises over time within the first frequency band fr1, and may be called an "up chirp". Similarly, the fourth drive signal DS4 corresponding to the symbol DL may have a frequency characteristic in which the drive frequency slightly rises from the microphone center frequency fc and then falls to the design lower limit frequency fd. Such a frequency modulation mode is also generally characterized by a frequency modulation mode in which the frequency drops over time within the fourth frequency band fr4, and may be called a "down chirp".

The center frequency may be the median or the average value.

Needless to say, the elements constituting the above embodiments are not necessarily essential, except when expressly stated as essential or when it is considered to be clearly essential in principle. Furthermore, when the numbers, amounts, ranges, etc. of components are mentioned, the present invention is not limited to those specific values, except when expressly stated as essential or when it is clearly limited to specific values in principle. Similarly, when the shapes, directions, positional relationships, etc. of components are mentioned, the present invention is not limited to those shapes, directions, positional relationships, etc., except when expressly stated as essential or when it is clearly limited to specific shapes, directions, positional relationships, etc., in principle.

The modified examples are not limited to the above examples. In addition, multiple modified examples may be combined with each other. Furthermore, all or part of the above embodiment and all or part of the modified examples may be combined with each other.

2 Electronic control device 3 Ultrasonic sensor 4 Transmitting/receiving unit 40A Transmitting unit 40B Receiving unit 7 Sensor control unit 71 Drive control unit 72 Correcting unit 73 Detection unit 74 Determination unit

Claims (14)

An object detection device (3) configured to detect an object (B) around a moving body (C) when mounted on the moving body,
A drive control unit (71) that sets a frequency modulation mode within a predetermined frequency band in a drive signal that drives a transmission unit (40A) to transmit to the outside a transmission wave that is an ultrasonic wave encoded by frequency modulation;
a detection unit (73) that detects the object based on a reception signal corresponding to a reception result by a receiving unit (40B) of a reception wave including a reflected wave of the transmission wave by the object;
Equipped with
The detection unit has a determination unit (74) that determines a code included in the received wave based on a match between a reference signal corresponding to the drive signal and the received signal,
the drive control unit is configured to select and set, as a code to be assigned to the drive signal, any one of a plurality of types of codes including at least a first code characterized by a frequency modulation mode in which a frequency increases over time in a first frequency band, a second code characterized by a frequency modulation mode in which a frequency increases over time in a second frequency band different from the first frequency band, a third code characterized by a frequency modulation mode in which a frequency decreases over time in a third frequency band, and a fourth code characterized by a frequency modulation mode in which a frequency decreases over time in a fourth frequency band different from the third frequency band, and to increase a frequency band and/or a number of pulses in the drive signal as the code corresponding to a frequency band farther away from a center frequency of the transmission unit;
an upper limit frequency of the first frequency band is higher than an upper limit frequency of the second frequency band;
a lower limit frequency of the first frequency band is higher than a lower limit frequency of the second frequency band,
an upper limit frequency of the third frequency band is higher than an upper limit frequency of the fourth frequency band;
a lower limit frequency of the third frequency band is higher than a lower limit frequency of the fourth frequency band;
Object detection device. The drive control unit is
When the start frequency of the drive signal is close to the center frequency of the transmitter, the start frequency is set to the opposite side of the center frequency of the transmitter from the end frequency of the drive signal;
When the end frequency of the drive signal is close to the center frequency of the transmission unit, the end frequency is set to the opposite side of the center frequency of the transmission unit to the start frequency of the drive signal.
The object detection device according to claim 1 . An object detection device (3) configured to detect an object (B) around a moving body (C) when mounted on the moving body,
A drive control unit (71) that sets a frequency modulation mode within a predetermined frequency band in a drive signal that drives a transmission unit (40A) to transmit to the outside a transmission wave that is an ultrasonic wave encoded by frequency modulation;
a detection unit (73) that detects the object based on a reception signal corresponding to a reception result by a receiving unit (40B) of a reception wave including a reflected wave of the transmission wave by the object;
Equipped with
The detection unit has a determination unit (74) that determines a code included in the received wave based on a match between a reference signal corresponding to the drive signal and the received signal,
The drive control unit is
a code to be assigned to the drive signal is selected and set from a plurality of types of codes including at least a first code characterized by a frequency modulation mode in which the frequency increases over time in a first frequency band, a second code characterized by a frequency modulation mode in which the frequency increases over time in a second frequency band different from the first frequency band, a third code characterized by a frequency modulation mode in which the frequency decreases over time in a third frequency band, and a fourth code characterized by a frequency modulation mode in which the frequency decreases over time in a fourth frequency band different from the third frequency band;
When the start frequency of the drive signal is close to the center frequency of the transmitter, the start frequency is set to the opposite side of the center frequency of the transmitter from the end frequency of the drive signal;
When the end frequency of the drive signal is close to the center frequency of the transmitter, the end frequency is configured to be on the opposite side of the center frequency of the transmitter from the start frequency of the drive signal,
an upper limit frequency of the first frequency band is higher than an upper limit frequency of the second frequency band;
a lower limit frequency of the first frequency band is higher than a lower limit frequency of the second frequency band,
an upper limit frequency of the third frequency band is higher than an upper limit frequency of the fourth frequency band;
a lower limit frequency of the third frequency band is higher than a lower limit frequency of the fourth frequency band;
Object detection device. the drive control unit sets a frequency band and/or a pulse number in the drive signal so as to suppress a difference in frequency bandwidth in the received wave among the first code, the second code, the third code, and the fourth code.
The object detection device according to any one of claims 1 to 3 . Further comprising a correction unit (72) that corrects the reference signal according to the moving speed of the moving object.
The object detection device according to any one of claims 1 to 4 . An object detection device (3) configured to detect an object (B) around a moving body (C) when mounted on the moving body,
A drive control unit (71) that sets a frequency modulation mode within a predetermined frequency band in a drive signal that drives a transmission unit (40A) to transmit to the outside a transmission wave that is an ultrasonic wave encoded by frequency modulation;
a correction unit (72) that corrects a reference signal corresponding to the drive signal in accordance with a moving speed of the moving body;
a detection unit (73) that detects the object based on a reception signal corresponding to a reception result by a receiving unit (40B) of a reception wave including a reflected wave of the transmission wave by the object;
Equipped with
The detection unit has a determination unit (74) that determines a code included in the received wave based on a match between the reference signal and the received signal,
the drive control unit is configured to select and set, as a code to be assigned to the drive signal, any one of a plurality of types of codes including at least a first code characterized by a frequency modulation mode in which a frequency increases over time within a first frequency band, a second code characterized by a frequency modulation mode in which a frequency increases over time within a second frequency band different from the first frequency band, a third code characterized by a frequency modulation mode in which a frequency decreases over time within a third frequency band, and a fourth code characterized by a frequency modulation mode in which a frequency decreases over time within a fourth frequency band different from the third frequency band;
an upper limit frequency of the first frequency band is higher than an upper limit frequency of the second frequency band;
a lower limit frequency of the first frequency band is higher than a lower limit frequency of the second frequency band,
an upper limit frequency of the third frequency band is higher than an upper limit frequency of the fourth frequency band;
a lower limit frequency of the third frequency band is higher than a lower limit frequency of the fourth frequency band;
Object detection device. The correction unit corrects the reference signal in accordance with the moving speed and a relative position of the object with respect to the moving body.
7. The object detection device according to claim 5 or 6 . A plurality of the transmitters are arranged in an arrangement direction intersecting with the traveling direction of the moving body, and among the plurality of the transmitters, the transmitter currently driven by the drive control unit is defined as a self-transmitting unit, and the other transmitters different from the self-transmitting unit are defined as other transmitters. The drive control unit assigns a code different from that of the other transmitters to the drive signal so that the frequency of the other transmitters changes in a direction different from that of the adjacent other transmitters.
The object detection device according to any one of claims 1 to 7 . An object detection device (3) configured to detect an object (B) around a moving body (C) when mounted on the moving body,
A drive control unit (71) that sets a frequency modulation mode within a predetermined frequency band in a drive signal that drives a transmission unit (40A) to transmit to the outside a transmission wave that is an ultrasonic wave encoded by frequency modulation;
a detection unit (73) that detects the object based on a reception signal corresponding to a reception result by a receiving unit (40B) of a reception wave including a reflected wave of the transmission wave by the object;
Equipped with
The detection unit has a determination unit (74) that determines a code included in the received wave based on a match between a reference signal corresponding to the drive signal and the received signal,
the drive control unit is configured to select and set, as a code to be assigned to the drive signal, any one of a plurality of types of codes including at least a first code characterized by a frequency modulation mode in which a frequency increases over time within a first frequency band, a second code characterized by a frequency modulation mode in which a frequency increases over time within a second frequency band different from the first frequency band, a third code characterized by a frequency modulation mode in which a frequency decreases over time within a third frequency band, and a fourth code characterized by a frequency modulation mode in which a frequency decreases over time within a fourth frequency band different from the third frequency band;
an upper limit frequency of the first frequency band is higher than an upper limit frequency of the second frequency band;
a lower limit frequency of the first frequency band is higher than a lower limit frequency of the second frequency band,
an upper limit frequency of the third frequency band is higher than an upper limit frequency of the fourth frequency band;
a lower limit frequency of the third frequency band is higher than a lower limit frequency of the fourth frequency band,
A plurality of the transmitters are arranged in an arrangement direction intersecting with the traveling direction of the moving body, and among the plurality of the transmitters, the transmitter currently driven by the drive control unit is defined as a self-transmitting unit, and the other transmitters different from the self-transmitting unit are defined as other transmitters. The drive control unit assigns a code different from that of the other transmitters to the drive signal so that the frequency of the other transmitters changes in a direction different from that of the adjacent other transmitters.
Object detection device. K transmitting units are arranged in an arrangement direction intersecting with the traveling direction of the moving body, and among the plurality of transmitting units, the transmitting unit currently driven by the drive control unit is defined as a local transmitting unit, and the other transmitting units different from the local transmitting unit are defined as other transmitting units, and a total of K transmissions in which each of the K transmitting units transmits the transmission wave in sequence once are defined as one cycle, the drive control unit assigns a different code to the drive signal that drives the local transmitting unit for each cycle.
An object detection device according to any one of claims 1 to 9. When the number of types of codes that can be assigned to the drive signal is M, the drive control unit assigns M types of codes to the drive signal that drives the transmission unit itself in M cycles.
The object detection device according to claim 10. An object detection device (3) configured to detect an object (B) around a moving body (C) when mounted on the moving body,
A drive control unit (71) that sets a frequency modulation mode within a predetermined frequency band in a drive signal that drives a transmission unit (40A) to transmit to the outside a transmission wave that is an ultrasonic wave encoded by frequency modulation;
a detection unit (73) that detects the object based on a reception signal corresponding to a reception result by a receiving unit (40B) of a reception wave including a reflected wave of the transmission wave by the object;
Equipped with
The detection unit has a determination unit (74) that determines a code included in the received wave based on a match between a reference signal corresponding to the drive signal and the received signal,
the drive control unit is configured to select and set, as a code to be assigned to the drive signal, any one of a plurality of types of codes including at least a first code characterized by a frequency modulation mode in which a frequency increases over time within a first frequency band, a second code characterized by a frequency modulation mode in which a frequency increases over time within a second frequency band different from the first frequency band, a third code characterized by a frequency modulation mode in which a frequency decreases over time within a third frequency band, and a fourth code characterized by a frequency modulation mode in which a frequency decreases over time within a fourth frequency band different from the third frequency band;
an upper limit frequency of the first frequency band is higher than an upper limit frequency of the second frequency band;
a lower limit frequency of the first frequency band is higher than a lower limit frequency of the second frequency band,
an upper limit frequency of the third frequency band is higher than an upper limit frequency of the fourth frequency band;
a lower limit frequency of the third frequency band is higher than a lower limit frequency of the fourth frequency band,
K transmitters are arranged in an arrangement direction intersecting with the traveling direction of the moving body, and among the plurality of transmitters, the transmitter currently driven by the drive control unit is defined as a local transmitter, and the other transmitters different from the local transmitter are defined as other transmitters. When a total of K transmissions in which each of the K transmitters transmits the transmission wave once in turn is defined as one cycle, the drive control unit assigns a different code to the drive signal that drives the local transmitter for each cycle,
When the number of types of codes that can be assigned to the drive signal is M, the drive control unit assigns M types of codes to the drive signal that drives the transmission unit in M cycles.
Object detection device. a center frequency of the first frequency band is higher than a center frequency of the transmission unit;
a center frequency of the second frequency band is lower than a center frequency of the transmitter;
a center frequency of the third frequency band is higher than a center frequency of the transmitter;
The center frequency of the fourth frequency band is lower than the center frequency of the transmitter.
An object detection device according to any one of claims 1 to 12 . a lower limit frequency of the first frequency band is a center frequency of the transmitter or a frequency close to the center frequency of the transmitter;
an upper limit frequency of the second frequency band is at or near a center frequency of the transmitter;
a lower limit frequency of the third frequency band is a center frequency of the transmitter or a frequency close to the center frequency of the transmitter;
The upper limit frequency of the fourth frequency band is the center frequency of the transmitter or in the vicinity thereof.
The object detection device according to claim 13 .

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