JPH0743426B2 - Ultrasonic obstacle sensor - Google Patents

Description

TECHNICAL FIELD The present invention relates to an ultrasonic obstacle sensor used for automobiles and the like.

In particular, the present invention relates to an ultrasonic obstacle sensor of an automobile suspension control device that detects a road surface condition ahead of the vehicle and reduces a shock of a vehicle body.

[Prior Art] As a conventional obstacle sensor using ultrasonic waves, for example, there is a device for detecting an obstacle around a vehicle disclosed in Japanese Patent Publication No. 1-30436.

Further, for example, there is a suspension device disclosed in Japanese Unexamined Patent Publication No. 62-131813 for absorbing the shock of the vehicle body by detecting the front road surface condition in advance.

Conventionally, when trying to detect an object (obstacle) with ultrasonic waves, there are many methods that calculate the road separation from surrounding objects with ultrasonic waves, from short distance (several cm) to long distance (several meters). Various measures have been proposed for accurately measuring an object.

However, in this method, a reflected wave from a predetermined road surface is also detected as an obstacle, so that the reflected wave from the road surface should not be detected by devising the directivity of the horn, for example. In general, there is no proposal for signal processing that positively detects only the reflected wave signal on the road surface and effectively detects obstacles on the road from the signal on the contrary. .

On the other hand, a method of irradiating a road ahead with a continuous wave and continuously observing a received wave to detect an obstacle on the road has been proposed, but the continuous wave has the following many drawbacks.

Due to the heat generated by the transmitter, the energy of ultrasonic waves cannot be increased.

 It is affected by transmitting and receiving waves and standing waves.

It is not possible to distinguish between a reflected wave from a predetermined road surface in front and a signal other than that.

There is no point in distinguishing the influences of the intensity change of the reflected wave other than unevenness, such as wind and temperature unevenness.

[Problems to be Solved by the Invention] In the conventional ultrasonic obstacle sensor as described above, the reflected wave from the road surface is also detected as an obstacle, so that the directivity of the horn must be devised. was there.

Further, when the continuous wave is irradiated, there is a problem that the energy of the ultrasonic wave cannot be increased due to heat generation of the transmitter.

Furthermore, the condition of the reflected wave from the obstacle changes due to the change of the surface condition of the road surface near the obstacle (whether it is a smooth road surface like concrete or a rough road surface like gravel). The intensity of the reflected wave from the road surface, which should be called backland, also changes greatly.

The present invention has been made to solve the above-mentioned problems, and it is possible to effectively distinguish and determine only a change in signal due to an obstacle from among changes in a received signal of a reflected wave,
Moreover, it is an object of the present invention to obtain an ultrasonic obstacle sensor capable of detecting the state of the road surface in the background.

[Means for Solving the Problems] An ultrasonic obstacle sensor according to the present invention is an ultrasonic obstacle sensor attached to a vehicle, and includes a first command signal for intermittently generating an ultrasonic wave and Timing command means for generating a second command signal indicating a predetermined time range, ultrasonic signal generating means for generating an ultrasonic signal based on the first command signal, and the above-mentioned ultrasonic signal generator in response to the ultrasonic signal. Ultrasonic wave transmitting means for radiating ultrasonic waves to the road surface diagonally forward, ultrasonic wave receiving means for receiving the reflected wave of the ultrasonic wave and generating a reception signal, and a predetermined time range based on the second command signal. Received signal amplification means that extracts and amplifies received signal, AM detects and outputs AM detected signal, and detects the peak value of the reflected wave AM detected signal during a predetermined time for each ultrasonic wave transmission And then find it the next peak value By holding until the peak value is detected, a peak value detecting means for outputting a time-series signal which is a continuous signal representing a temporal change in the peak value, and the time-series signal is compared in magnitude with a predetermined comparison level, and the diagonal forward It is provided with a comparison means for outputting an obstacle detection signal indicating the unevenness of the road surface within a predetermined range.

[Operation] In the present invention, the timing command means generates the first command signal for intermittently generating ultrasonic waves and the second command signal indicating the predetermined time range, and the ultrasonic signal generating means. An ultrasonic wave signal is generated based on the first command signal, and the ultrasonic wave is radiated onto the road surface diagonally forward in response to the ultrasonic wave signal by the ultrasonic wave transmitting means. Further, the ultrasonic wave reception means receives the reflected wave of the ultrasonic wave and generates a reception signal. In addition, the reception wave amplifying means extracts and amplifies the reception signal within a predetermined time range based on the second command signal, AM-detects it, and outputs an AM detection signal. Furthermore, by the peak value detecting means, for each ultrasonic wave transmitted, the AM of the reflected wave is
The peak value of the detection signal during a predetermined time is detected,
By holding it until the next peak value is detected, a time-series signal that is a continuous signal representing the temporal change of the peak value is output. Then, the time-series signal is compared in magnitude with a predetermined comparison level by the comparison means, and an obstacle detection signal representing the unevenness of the road surface within the predetermined range diagonally forward is output.

[Embodiment] The construction of an embodiment of the present invention will be described with reference to FIG. 1, FIG. 2, FIG. 3, FIG. 4, FIG.

FIG. 1 is a block diagram showing an embodiment of the present invention.

In FIG. 1, an embodiment of the present invention comprises a timing command means (1), an ultrasonic signal generating means (2) connected to the timing command means (1), and an ultrasonic signal generating means (2). ) And ultrasonic transmission means (3) such as an ultrasonic microphone installed near the bumper of the vehicle body
Similarly, an ultrasonic wave receiving means (4) such as an ultrasonic microphone installed near the bumper of the vehicle body, a received wave amplifying means (5) connected to the ultrasonic wave receiving means (4), and a timing commanding means. (1) and average value calculating means (6) connected to the received wave amplifying means (5), and reference value setting means (7)
And an amplification factor changing means (8) whose input side is connected to the average value computing means (6) and reference value setting means (7) and whose output side is connected to the received wave amplifying means (5), and the received wave amplifying means ( 5) connected to the peak value detecting means (9), the comparison level setting means (100), and the peak value detecting means (9) and the comparison level setting means (100).
0) and an average value calculating means (130) connected to the peak value detecting means (9).

FIG. 2 is a circuit diagram showing the timing command means (1) of the embodiment of the present invention.

In FIG. 2, the timing command means (1) is connected to, for example, a Hitachi HD63BO1Y microcomputer (10), a crystal oscillator (11) connected to this microcomputer (10), and a microcomputer (10). Starting circuit (12), monostable multi-pulse generation circuit (15) connected to the microcomputer (10), and monostable multi-pulse generation circuit (16) connected to this monostable multi-pulse generation circuit (15) ) And a monostable multipulse generator circuit (17) connected to the monostable multipulse generator circuit (15)
It consists of and.

The starter circuit (12) is composed of a self-resetting normally open starter switch (13) installed in the driver's seat of an automobile and a shaping circuit (14) connected to the starter switch (13). There is.

FIG. 3 is a circuit diagram showing the ultrasonic signal generating means (2) of one embodiment of the present invention.

In FIG. 3, an ultrasonic signal generating means (2) is a NAND connected to the ultrasonic oscillation circuit (20) and the microcomputer (10) of the ultrasonic oscillation circuit (20) and the timing command means (1). Gate (21) and this NAND gate (21)
Connected to this inverter (22) and this inverter (2
2) the amplifier circuit (23) connected to this amplifier circuit (2)
It consists of a step-up transformer (24) connected to 3).

FIG. 4 is a circuit diagram showing details of the receiving system according to the embodiment of the present invention.

In FIG. 4, the received wave amplifying means (5) includes an amplifying circuit (50) connected to the ultrasonic wave receiving means (4) and an AM detection variable amplifying circuit (51) connected to the amplifying circuit (50). It consists of and.

The AM detection variable amplification circuit (51) includes an AM detection circuit connected to the amplification circuit (50), an FET (52) connected to the amplification factor changing means (8), an AM detection circuit and an FET (52). ) Is connected to the variable amplifier circuit (53).

The average value calculating means (6) includes an analog switch (60),
The resistors (6
1) and a capacitor (62).

The peak value detecting means (9) is a peak hold circuit composed of a diode, a capacitor and a resistor.

FIG. 5 is a side view showing the mounting position of the embodiment of the present invention.

In FIG. 5, the ultrasonic wave transmitting means (3) and the ultrasonic wave receiving means (4) are attached below the bumper (201) of the vehicle body (200) and are obliquely forward about 20 ° (20 ° ± 10 °). Is oriented.

6 (a) and 6 (b) are a side view and a front view showing ultrasonic wave transmitting means (3), (4) which are a part of one embodiment of the present invention.

Next, the operation of the above-described embodiment will be described with reference to FIGS. 7 and 8.

FIG. 7 is a timing chart showing a signal waveform according to an embodiment of the present invention, and FIG. 8 is a timing chart showing a signal waveform with the time axis changed in the embodiment of the present invention.

In FIGS. 7 (a) to (m), v ₀ is a command signal, v ₁ is a drive signal, v ₂ is a received signal which is a reflected wave from a rough asphalt surface without large obstacles, and v ₂ ^* is Received signal that is a reflected wave from the asphalt surface where an obstacle exists, v ₃ is an AM detection signal of the received signal v ₂ ^* , v ₄ is a reflected wave that is a reflected wave from a concrete surface with a smooth surface without large obstacles Signal, v ₄ ^* is a received signal that is a reflected wave from a concrete surface where an obstacle is present, v ₅ is an AM detection signal of the received signal v ₄ ^* ,
v _6a , v _6b, and v _6c are timing pulse signals, v ₇ is a received signal amplified for a predetermined period, and v ₈ is an average level signal.

In FIGS. 8A to 8D, v ₉ is a time series signal, v ₁₀
Is an obstacle detection signal, v ₁₁ is an average value signal, and v ₁₂ is a control voltage signal.

First, the timing command means (1)
A command signal v ₀ shown in FIG. 7A for pulse-oscillating an ultrasonic wave for a predetermined time is supplied to the ultrasonic signal generating means (2).

The timing command means (1) may be constituted by a programmable timer built in the microcomputer (10) or can be easily realized by using a commercially available timer IC. The start switch (13) of the timing command means (1) produces a low level signal due to its temporary closing, and the shaping circuit (14) inversely shapes the low level signal and produces it as a start signal. Microcomputer (1
0) is a crystal oscillator (1
Generate a series of clock signals based on the oscillation action of 1),
In response to each of these clock signals, a computer program stored in advance inside the clock signal is executed, and the command signal v ₀
Is output.

The ultrasonic signal generating means (2), based on the command signal v ₀ ,
The ultrasonic wave transmitting means (3) is driven by the drive signal v ₁ shown in FIG. 7, which has a predetermined voltage and frequency for a predetermined time.

This ultrasonic signal generating means (2) is composed of an ultrasonic oscillation circuit (2
A series of ultrasonic oscillation pulses arising from 0) at a predetermined high frequency, the command signal v ₀ from the microcomputer (10)
Is generated, the ultrasonic wave pulse generated from the inverter (22) is amplified by the amplifier circuit (23) as a series of oscillation pulses, and the booster transformer (24). ) And is applied to the ultrasonic wave transmitting means (3).

The ultrasonic wave transmitting means (3) irradiates an ultrasonic pulse to the road surface G diagonally forward and downward, and the ultrasonic wave receiving means (4) receives signals v ₂ , v ₂ ^* , v which are reflected waves from the road surface. Receive ₄ or v ₄ ^* .

The time t ₁ section of the received signal v ₂ shown in FIG. 7 (c) is the component of the unnecessary reflected wave due to the direct wave or the wraparound, and it is improved by the layout of the ultrasonic microphone, the directivity formation, and the device for holding. . The time t _b corresponds to the round-trip time of the shortest detection path Sb shown in FIG. 1 when the ultrasonic wave transmitting / receiving means are adjacent to each other and have the same directivity. At the same time, t _a corresponds to the center path Sa and t _c corresponds to the farthest path Sc, where t _a = 2Sa / C, t _b = 2Sb / C, t _c = 2Sc / C, where C is the speed of sound. .

Further, from the directivity of the ultrasonic wave transmission means (3) and receiving means (4), the intensity of the reflected wave from the road surface G takes a maximum value at the point corresponding to the time t _a, the time t _b, corresponding to t _c It will disappear when you do. The change in the intensity during that time is determined by the directional characteristics determined by the characteristics of the ultrasonic wave transmitting means (3) and the receiving means (4) and the geometrical layout, and the directional characteristics of the surface condition of the road surface G and the reflection of ultrasonic waves on the surface. Is determined by
It becomes a substantially mountain-shaped waveform showing _a peak at time ta.

The received signal v ₂ ^* shown in FIG. 7 (d) is the waveform of the received signal v _{2 with} the reflected wave from the obstacle S superimposed, and t ₂ is the ultrasonic wave transmitting means (3) and the receiving means ( 4) is equivalent to the round trip time of the shortest route between the obstacle S and the obstacle S is stationary on the road surface G, and the vehicle equipped with the ultrasonic obstacle sensor is on the road surface G.
Considering the case where the vehicle travels too close to the obstacle S and gets too close to the obstacle S, the obstacle S is captured at the time t _c , and after the time t _a is passed to the time t _b , the detection becomes undetectable, and then the vehicle becomes an obstacle. It goes over the object S and goes too far, and t ₂ changes from t _c → t _a → t _b . Since the peak of the reflected wave of the obstacle S is substantially equivalent to the value obtained by multiplying the reflection intensity from the road surface G corresponding to the time of t ₂ by a predetermined magnification, the peak of the obstacle S is traced according to t _2. It can be seen that the mountain shape is formed as in the case of the intensity of the reflected wave only on the road surface G.

The received wave amplifying means (5), for example, amplifies the received signal v ₂ ^* in order to facilitate processing of the received level, performs AM detection, and performs AM detection.
Output the detection signal v ₃ . If the road surface G is flat, the AM detection signal v ₃ consists of the received wave v _{3 (A)} only on the road surface, and if the obstacle S is on the road surface G, the received wave v _{3 (B)} corresponding to the obstacle S The component of is also superposed, and v ₃ ≈v _{3 (A)} + v _{3 (B)} is obtained as an AM detection signal.

Since the received wave amplifying means (5) masks the signal in the unnecessary signal section t ₂ at the same time as the AM detection, only the signal in the necessary section of t _{b to} t _c is AM detected and the AM detected signal v You get ₃ .

By the way, the received signals shown in FIGS. 7 (c) and 7 (d)
v ₂ and v ₂ ^* are the cases where the surface of the road surface G is rough, such as asphalt, and when the surface of the road surface G is concrete, the received signal v shown in FIGS. 7 (f) and (g) ₄ , v ₄ ^*
become that way. This is because if the received signals v ₂ and v ₂ ^* are traveling at low speed even when traveling on the same asphalt surface,
This is the same as when the received signals v ₄ and v ₄ ^* are traveling at high speed.

It is difficult to distinguish the AM detection signals v ₃ and v ₅ shown in FIGS. 7 (e) and 7 (h) as they are at the same determination level, for example, by distinguishing v _{3 (A)} and v _{3 (B).} Is. However, when the peak of the received wave at time (t _c -t _b ) is detected and its time-series change is observed, the reflected wave of the road surface G as shown by the dotted line and the alternate long and short dash line in FIG. Although the peak of No. varies depending on the road surface G, its average value is a predetermined value corresponding to the surface state of the road surface G, and the peak of the obstacle S is detected as a signal that is changed from the peak of the road surface and protrudes. It is possible.

On the other hand, the timing command means (1) uses the command signal V ₀ as a trigger to calculate the time corresponding to t _b to t _c until the next cycle, or FIG. 7 (i) to (k) The timing pulse signals v _6a , v _6b and v _6c shown in (4) are prepared and the average value calculating means (6) is operated.

The timing command means (1) may be created equally between the command signal v ₀ in programmable timer of the microcomputer (10), it is triggered by the command signal v _0, a pulse signal of a predetermined time width Output timer IC
You may comprise a monostable multivibrator circuit by.

Timing pulse signals v _6a and v _6b thus obtained
And v _6c correspond to t _b , t _a -t _b and t _c -t _b .

The reception wave amplifying means (5) is, for example, a variable amplification that amplifies the reception signal v ₄ ^* , performs AM detection to obtain an AM detection signal v _5, and then controls the amplification degree by controlling the gate voltage of the FET (52). The reception signal v ₇ whose amplification is controlled by the circuit (53) is obtained and supplied to the average value calculating means (6).

The average value calculating means (6) samples only the signal of a predetermined period by the analog switch (60) controlled by the timing pulse signal v _6c , averages and holds the level, and amplifies the average level signal v ₈ . The rate changing means (8) is supplied.

The amplification factor changing means (8) compares the average level signal v ₈ with a desired reference value so that the average level signal becomes the reference value.
The gate voltage of FET (52) is feedback controlled.

The peak value detecting means (9) samples and holds the peak voltage of the signal in the above-mentioned predetermined period with a predetermined time constant, and holds it to convert it into an analog time-series signal v ₉ to compare it with (110). That is, each time the ultrasonic wave is transmitted, the peak value of the reflected wave AM detection signal during the predetermined time is detected and held until the next peak value is detected. It outputs a time-series signal that is a continuous signal that represents a dynamic change. As shown in FIG. 8A, the time-series signal v ₉ has a waveform when passing through a road protrusion that is an obstacle while traveling on asphalt at a predetermined speed.

The comparison means (11) compares the time series signal v ₉ with a predetermined comparison level and outputs an obstacle detection signal v ₁₀ . That is, if there is a protrusion on the road surface, the level changes at a predetermined ratio with respect to the average value of the time-series signal v _9. Therefore, by comparing the level with the comparison level, the obstacle shown in FIG. Detection signal v ₁₀
Can be obtained.

In the case of the present embodiment, since the automatic gain control circuit (AGC) for controlling the peak value or the average level of the output of the received signal to be substantially constant is provided, the average output signal v ₁₁ and signal v ₈ are It becomes substantially constant, and instead the signal v ₁₂ which is the control voltage of the AGC becomes an output voltage level indicating the surface condition such as the roughness and unevenness of the road surface, so that the surface condition of the road surface can be detected.

Further, in another embodiment in which the FET (52) is changed to a fixed resistance, when the AGC function is stopped (OFF), the average value of the signal v ₁₁ and the signal v ₈ becomes an output level corresponding to the surface condition of the road surface. Therefore, the surface condition of the road surface can be similarly detected.

Even on the same road surface, the above-mentioned level changes depending on the vehicle speed. Therefore, the vehicle speed signal causes μ of the road surface (a friction coefficient that quantifies the roughness of the road surface, such as μ = 0 for ice and μ≈1 for asphalt). It goes without saying that the accuracy can be further improved by changing the judgment value of. It is needless to say that the absolute value of the roughness is not necessary, but when a signal having a sudden change of μ is required, the purpose is achieved by the signal having the change of the signals v ₈ , v ₁₁ and v ₁₂ .

Furthermore, in the above example, since the case of using AGC was described, the level of change due to obstacles with respect to the level of the peak value of the road surface could be determined by a fixed threshold value even at a substantially constant ratio. Needless to say, the same effect can be obtained by setting a threshold value so as to detect a change of a predetermined ratio when AGC is OFF. Further, although the average value calculating means, the peak value detecting means, and the comparing means are composed of analog circuits, it goes without saying that the same effect can be obtained even if the microcomputer and the A / D converter are composed of a digital circuit and a program. . In this case, the time series change of the peak value can be easily realized by storing the peak value in time series. Further, although the ultrasonic wave transmitting means and the receiving means are separately installed, it is needless to say that the same effect can be obtained even if one microphone is used for both transmission and reception because it is a pulse system.

As described above, according to one embodiment of the present invention, even in the case of pulse oscillation, the peak value of a predetermined section of the received wave is processed in time series as if it were a continuous wave, and the level change From the ratio, it is possible to provide an excellent device that solves the drawbacks of continuous waves with a simple configuration of detecting obstacles.

In addition, the addition of AGC has the effect that the level of comparison can be made a simple circuit configuration with a substantially constant level, and the application range of this sensor can be stabilized and expanded to a wide range regardless of the road surface condition or the increase or decrease in vehicle speed. There is.

Furthermore, by outputting the output corresponding to the average of the received signal level or the average of the peak values, for example, the output of AGC as the signal of the roughness of the road surface, not only the obstacle sensor but also the slipperiness of the road surface By outputting information and information about changes in road surface conditions, suspension, brakes, 4WD and 4
A sensor effective for controlling WS can be provided.

The mounting portion and the angle θ (20 ° ± 10 °) provide optimum conditions for maximizing the effects of the above-described embodiment.

[Advantages of the Invention] As described above, the present invention is an ultrasonic obstacle sensor mounted on a vehicle, and shows a first command signal and a predetermined time range for intermittently generating ultrasonic waves. A timing command means for generating a second command signal, an ultrasonic signal generating means for generating an ultrasonic signal based on the first command signal, and the ultrasonic wave diagonally forward in response to the ultrasonic signal. An ultrasonic wave transmitting means for irradiating the road surface, an ultrasonic wave receiving means for receiving a reflected wave of the ultrasonic wave and generating a received signal, and a received signal in a predetermined time range are extracted based on the second command signal. Received wave amplifying means for amplifying and AM detecting and outputting an AM detected signal, and for each transmission of the ultrasonic wave, detects the peak value of the AM detected signal of the reflected wave during a predetermined time, and then detects it. Hold until the peak value of is detected Thereby, a peak value detecting means for outputting a time-series signal which is a continuous signal representing a temporal change of the peak value,
Since the time-series signal is compared with a predetermined comparison level in magnitude to output an obstacle detection signal indicating the unevenness of the road surface within the predetermined range in the obliquely forward direction, a change in the received signal of the reflected wave is provided. It is possible to effectively distinguish and determine only the signal change due to the obstacle from among the above.

[Brief description of drawings]

FIG. 1 is a block diagram showing an embodiment of the invention, FIG. 2 is a circuit diagram showing a timing command means of an embodiment of the invention, and FIG. 3 is an ultrasonic signal generating means of an embodiment of the invention. FIG. 4 is a circuit diagram showing a receiving system of an embodiment of the present invention, FIG. 5 is a side view showing a part of an embodiment of the present invention, and FIGS. 6 (a) and 6 (b). ) Is a side view and a front view showing a part of an embodiment of the present invention, and FIG. 7 is a timing chart showing signal waveforms of respective parts of the embodiment of the present invention,
FIG. 8 is a timing chart showing the signal waveform of each part of the embodiment of the present invention. In the figure, (1) ... timing command means, (2) ... ultrasonic signal generating means, (3) ... ultrasonic wave transmitting means, (4) ... ultrasonic wave receiving means, (5) ... reception wave Amplifying means, (6) ... Average value calculating means, (7) ... Reference value setting means, (8) ...
Amplification factor changing means, (9) ... Peak value detecting means, (10
0) …… Comparison level setting means, (110) …… Comparison means,
(130) ... means calculation means. In the drawings, the same reference numerals indicate the same or corresponding parts.

Claims (1)

[Claims] 1. An ultrasonic obstacle sensor mounted on an automobile, the timing of generating a first command signal for intermittently generating ultrasonic waves and a second command signal indicating a predetermined time range. Commanding means, ultrasonic wave signal generating means for generating an ultrasonic wave signal based on the first commanding signal, ultrasonic wave transmitting means for irradiating the ultrasonic wave to an obliquely forward road surface in response to the ultrasonic wave signal, Ultrasonic wave receiving means for receiving a reflected wave of a sound wave and generating a reception signal, extracting and amplifying a reception signal within a predetermined time range based on the second command signal, AM detecting and outputting an AM detection signal Received wave amplifying means, for each transmission of the ultrasonic wave, by detecting the peak value of the AM detection signal of the reflected wave during a predetermined time, and holding it until the next peak value is detected, the peak value Representing the temporal change of Value detecting means for outputting a time-series signal which is a signal, and comparing the time-series signal with a predetermined comparison level to output an obstacle detection signal indicating the unevenness of the road surface within a predetermined range diagonally ahead. An ultrasonic obstacle sensor, characterized by comprising: