JP7630876B2 - Electronic device and vehicle stop determination method - Google Patents

Description

The present invention relates to an electronic device that has the function of determining whether a moving object is in a stopped or parked state.

Navigation devices installed in moving objects (such as automobiles and motorcycles) use a GPS receiver, angular velocity sensor, acceleration sensor, etc. to calculate the vehicle's position, and use this to search for a route to a destination and provide route guidance. Navigation devices also use vehicle speed pulses generated in response to the rotation of the wheels to determine the distance traveled by the moving object and whether it has stopped. For example, the stoppage determination device in Patent Document 1 compares the difference between the average acceleration value for a currently specified period and the average acceleration value for a previously specified period with a threshold value, and determines that the moving object is stopped when the difference is equal to or less than the threshold value.

JP 2012-163465 A

Navigation devices use the output of the angular velocity sensor (gyro sensor) installed in the vehicle to calculate the vehicle's heading (amount of rotation), and also use the vehicle speed pulse to calculate the vehicle's travel distance, making it possible to detect the vehicle's relative position from these results. However, because detection by the angular velocity sensor contains errors, if detection errors accumulate, the detection accuracy of the vehicle's position will decrease. To avoid this, when the vehicle is stopped, the zero point of the angular velocity sensor output is corrected so that detection errors do not accumulate.

In addition, the navigation device uses the vehicle speed pulse to determine whether the vehicle is stopped. In other words, it determines that the vehicle is stopped when the vehicle speed pulse is not input. However, with this determination method, if the vehicle is traveling at an extremely slow speed, the vehicle speed pulse is not input, and it may be erroneously determined that the vehicle is stopped. To avoid such erroneous determination, as described in Patent Document 1, an acceleration sensor is also used, and the vehicle is determined to be stopped when the difference in the average acceleration is equal to or less than a threshold value.

However, such a vehicle stop determination using an acceleration sensor has the following problem. Fig. 1 is a graph showing an example of the fluctuation of acceleration detected by the acceleration sensor while the vehicle is stopped, where the vertical axis is the acceleration sensor output [m/ ^s2 ] and the horizontal axis is time [seconds]. Note that the acceleration sensor can detect acceleration in three axial directions, the X-axis, the Y-axis, and the Z-axis, but here, the acceleration of the X-axis parallel to the straight-ahead direction of the vehicle is shown.

Even when the vehicle is stopped (idling), the detected acceleration fluctuates as shown in ranges S1, S2, and S3. For example, the acceleration in range S3 is greater than the acceleration in ranges S1 and S2. Such fluctuations in acceleration can occur due to vehicle vibration, individual differences in parts, product environment, and the like. If the threshold value for determining whether the vehicle is stopped is set to a fixed value, the accuracy of determining whether the vehicle is stopped may decrease due to fluctuations in acceleration, and it is also difficult to determine an optimal threshold value in advance. Furthermore, even when comparing the difference between the average acceleration value for the currently specified period and the average acceleration value for the previously specified period with a threshold value as in Patent Document 1, if there is a fluctuation in acceleration, the difference in the average values will also vary, making it difficult to accurately determine whether the vehicle is stopped.

The present invention aims to solve these conventional problems and provide an electronic device and a method for determining whether a vehicle is stopped that improves the accuracy of determining whether the vehicle is stopped compared to conventional methods.

The electronic device according to the present invention is mounted on a moving body and has a function of determining whether the moving body is stopped, and includes a detection means for detecting the acceleration of the moving body, and a determination means for determining whether the moving body is stopped based on a difference between a first average value of acceleration in a first detection period detected by the detection means and a second average value of acceleration in a second detection period detected by the detection means, divided by the standard deviation of acceleration in the first detection period or the second detection period.

In one embodiment, the determination means compares the value with a threshold value, and determines that the moving body is in a stopped state when the value is equal to or less than the threshold value. In one embodiment, the determination means performs a stopped state determination when a vehicle speed pulse is not input for a certain period of time. In one embodiment, when the first detection period is longer than the second detection period, the value is divided by the standard deviation of the acceleration in the first detection period. In one embodiment, the electronic device further includes a storage means for storing the acceleration detected by the detection means, and the determination means acquires the acceleration in the first detection period and the second detection period from the storage means. In one embodiment, the electronic device further includes an angular velocity detection means for detecting the angular velocity of the moving body, and a correction means for correcting the output of the angular velocity detection means when the determination means determines that the moving body is in a stopped state.

The method of the present invention for determining whether a vehicle is stopped using an acceleration sensor mounted on a moving object includes a step of determining whether the moving object is stopped based on a difference between a first average value of acceleration in a first detection period and a second average value of acceleration in a second detection period detected by the acceleration sensor, divided by the standard deviation of acceleration in the first detection period or the second detection period.

According to the present invention, the stopped state of a moving object is determined based on the difference between the first average value of acceleration in a first detection period and the second average value of acceleration in a second detection period divided by the standard deviation of acceleration in the first detection period or the second detection period. This makes it possible to suppress the effects of variations and fluctuations in acceleration while the vehicle is stopped, and to determine the stopped state using the same threshold value regardless of changes in vehicle vibration or individual differences in parts. This allows for improved accuracy compared to determining the stopped state using a conventional acceleration sensor.

4 is a graph illustrating an example of fluctuations in the output value of an acceleration sensor while the vehicle is stopped. 1 is a block diagram showing a configuration of an in-vehicle device according to an embodiment of the present invention; FIG. 2 is a block diagram showing a configuration of a vehicle stop determination function according to an embodiment of the present invention. 11A and 11B are diagrams illustrating an example of settings of a detection period setting unit according to an embodiment of the present invention. FIG. 4 is a diagram illustrating a function of an averaging processor according to an embodiment of the present invention. 5 is a graph illustrating an effect of a vehicle stop determination function according to an embodiment of the present invention.

Next, an embodiment of the present invention will be described. The electronic device according to the present invention is mounted on a moving object such as an automobile or motorcycle, and has a function of determining whether the moving object has stopped using an acceleration sensor. The electronic device according to the present invention is not particularly limited, but can be, for example, an in-vehicle device equipped with navigation, audio, and visual functions mounted on a vehicle, a multi-function mobile phone (smartphone), a portable information terminal (tablet computer, laptop computer, notebook computer), etc.

Next, an embodiment of the present invention will be described with reference to the drawings. FIG. 2 is a block diagram showing an example of the configuration of an in-vehicle device 100 according to an embodiment of the present invention. The in-vehicle device 100 includes an input unit 110, a position detection unit 120, a navigation unit 130, a communication unit 140, a display unit 150, an audio output unit 160, a memory unit 170, a vehicle state acquisition unit 180, and a control unit 190. Although not shown here, the in-vehicle device 100 may also include, for example, audio-visual functions, a television and radio broadcast receiving function, etc.

The input unit 110 includes an input key device, a voice input recognition device, a touch panel, etc., and receives instructions from the user via these devices and provides them to the control unit 190. The position detection unit 120 detects the vehicle's position using various sensors. In one aspect, the position detection unit 120 includes a GPS receiver 122, an acceleration sensor 124, an angular velocity sensor (gyro sensor) 126, etc., and detects the current position of the vehicle using the outputs of these sensors. In another aspect, the position detection unit 120 may detect the vehicle's position using a vehicle speed pulse 182 acquired from the vehicle state acquisition unit 180 in addition to the above-mentioned sensors 122, 124, 126.

The GPS receiver 122 receives GPS signals transmitted from GPS satellites and detects the absolute position (latitude, longitude, altitude) of the vehicle based on the received GPS signals. This detection is performed at regular time intervals (for example, at one-second intervals).

The acceleration sensor 124 detects, for example, acceleration on three axes (X-axis, Y-axis, and Z-axis). The X-axis is, for example, the straight-ahead direction of the vehicle, the Y-axis is the lateral direction of the vehicle, and the Z-axis is the vertical direction. The acceleration detected by the acceleration sensor 124 can be used, for example, to calculate the inclination and travel distance of the vehicle. Acceleration detection is performed at regular time intervals (for example, 10 times per second). Note that the acceleration sensor 124 may detect acceleration in one or two axial directions.

The angular velocity sensor 126 detects, for example, angular velocity (angles/s) indicating the amount of rotation per unit time about three axes (yaw, pitch, roll). That is, the amount of rotation in the direction of travel of the vehicle, the amount of rotation forward and backward of the vehicle, and the amount of rotation left and right of the vehicle are detected. Angular velocity detection is performed at regular time intervals (for example, 10 times per second). Note that the angular velocity sensor 126 may detect only yaw, or may detect yaw and roll, or yaw and pitch.

The navigation unit 130 displays a road map of the area around the vehicle's position on the display unit 150 based on the vehicle's position detected by the position detection unit 120, searches for a route from the vehicle's position to the destination, displays the searched route on the road map, and provides guidance to the destination. The navigation unit 130 uses road map data stored in the memory unit 170, or obtains the necessary road map data from a road map server on the network connected via the communication unit 140.

The communication unit 140 enables wired or wireless data communication between the in-vehicle device 100 and the outside. For example, it enables data communication with an external server via the Internet. The communication unit 140 may use a communication module built into the in-vehicle device 100, or may use the communication function of an electronic device (e.g., a smartphone) externally connected to the in-vehicle device 100.

The display unit 150 displays a navigation screen, a menu screen, etc., provided by the navigation unit 130, and the audio output unit 160 outputs audio guidance, etc., provided by the navigation unit 130. The storage unit 170 is a non-volatile storage medium, and can store data and application software necessary for the in-vehicle device 100. The storage unit 170 can also store a road map database used by the navigation unit 130. The vehicle state acquisition unit 180 acquires information related to the state of the vehicle, for example, via an in-vehicle bus, etc. The information related to the state of the vehicle includes, for example, a vehicle speed pulse 182, gear information, side brake information, and blinker information. The acquired information is provided to the control unit 190.

The control unit 190 controls the operation of each part of the in-vehicle device 100. In one aspect, the control unit 190 includes a microprocessor or microcontroller equipped with ROM/RAM, etc., and controls various operations by executing a program stored in the ROM/RAM or application software stored in the memory unit 170. In this embodiment, the control unit 190 has a vehicle stop determination function that utilizes the acceleration sensor 124 in addition to normal operation control of the in-vehicle device 100.

Figure 3 is a block diagram showing the configuration of the vehicle stop determination function of this embodiment. The vehicle stop determination function 200 includes a vehicle stop determination unit 210, an acceleration storage unit 220, a detection period setting unit 230, an averaging processing unit 240, and a threshold comparison unit 250.

In one embodiment, the vehicle stop determination unit 210 determines whether the vehicle is stopped based on the vehicle speed pulse 182 acquired from the vehicle state acquisition unit 180. The vehicle speed pulse is a pulse waveform generated according to the rotation of the tires, that is, the number of pulses is proportional to the number of rotations of the tires. The vehicle stop determination unit 210 determines that the vehicle is stopped when the vehicle speed pulse is not input for a certain period of time. However, if the vehicle is traveling at an extremely low speed, the vehicle speed pulse is not input for a certain period of time, and there is a risk of erroneously determining that the vehicle is stopped. To avoid this, the vehicle stop determination unit 210 also uses the acceleration sensor 124 as described below, and uses the detection result of the acceleration sensor 124 as a weighting requirement for the vehicle stop determination. Note that when the vehicle stop determination unit 210 finally determines that the vehicle is stopped, the control unit 190 performs a correction to set the amount of rotation of the angular velocity sensor 126 to 0, eliminating the accumulation of detection errors.

The acceleration storage unit 220 sequentially stores the acceleration output from the acceleration sensor 124 at regular time intervals. The acceleration storage unit 220 is not particularly limited, but is configured, for example, using a memory or register with a certain storage capacity, and holds the acceleration output from the acceleration sensor 124 for a certain period of time. In one embodiment, the acceleration storage unit 220 stores the acceleration in the X-axis direction (the acceleration in the straight-line direction of the vehicle), which has good sensitivity when the vehicle is stopped. However, this is not essential, and the acceleration of the Y-axis or Z-axis other than the X-axis may also be stored.

The detection period setting unit 230 sets a detection period of acceleration for performing a vehicle stop determination, and reads out the acceleration of the set detection period from the acceleration storage unit 220. The detection period setting unit 230 pre-sets two detection periods with different periods. In one embodiment, as shown in FIG. 4(A), detection periods t1 and t2 based on time ts are set (t1>t2). Time ts is, for example, the timing when the vehicle speed pulse is not input and the vehicle stop determination unit 210 performs a vehicle stop determination using the acceleration sensor. The detection period t2 overlaps with the detection period t1, but as shown in FIG. 4(B), the detection period t1 and the detection period t2 may not overlap. In the example of FIG. 4(B), the detection period t1 is a period that is the offset period toff from the time ts (toff>t1, t1>t2). The detection period setting is not limited to the above, and detection period t1 and detection period t2 may partially overlap, or detection period t1 and detection period t2 may be equal in length.

The averaging processing unit 240 calculates the average value of the acceleration for the detection period set by the detection period setting unit 230, then calculates the difference between the average values, and divides the difference by the standard deviation. Specifically, as shown in the following formula, it calculates the difference between the average value of the acceleration sensor output for the past detection period t1 based on time ts and the average value of the acceleration sensor output for the past detection period t2 based on time ts, and calculates the difference correction value P by dividing this difference by the standard deviation of the acceleration sensor output for the detection period t1.

The variation in the acceleration detected by the acceleration sensor during detection period t1 is equalized by averaging, and the variation in the acceleration detected by the acceleration sensor during detection period t2 is also equalized by averaging. However, as shown in FIG. 1, even when the vehicle is stopped (idling stop, etc.), if the acceleration detected by the acceleration sensor fluctuates, the difference between the average value of detection period t1 and the average value of detection period t2 also varies (fluctuations), and therefore it becomes difficult to accurately determine the stopped state by comparing the difference with a threshold value.

This embodiment assumes that the errors generated by the acceleration sensor follow a normal distribution, and utilizes the property that the difference in the average values for different detection periods is proportional to the standard deviation of the population. In other words, when the overall variation in acceleration is large, the variation in the difference between the average value for detection period t1 and the average value for detection period t2 also becomes large, and the standard deviation becomes proportionally large. Conversely, when the overall variation in acceleration is small, the variation in the difference between the average value for detection period t1 and the average value for detection period t2 also becomes small, and the standard deviation becomes proportionally small. By dividing the difference by the standard deviation, the difference correction value P becomes a value that suppresses the effects of variation or fluctuations in acceleration while the vehicle is stopped.

Here, since detection period t1 is greater than detection period t2, the standard deviation of the acceleration sensor output during detection period t1 is used, but if detection period t1 is less than detection period t2, the standard deviation of the acceleration sensor output during detection period t2 is used. This is because the longer the detection period, i.e., the greater the number of acceleration sensors, the more reliable the standard deviation will be.

FIG. 5 shows an example in which the output of the acceleration sensor while the vehicle is stopped is sampled and corrected using the standard deviation. FIG. 5(A) shows an example in which the difference in the average value of the acceleration during different periods while the vehicle is stopped is small, and the standard deviation is 40 m/ ^s2 . FIG. 5(B) shows an example in which the difference in the average value of the acceleration during different periods while the vehicle is stopped is large, and the standard deviation is 100 m/ ^s2 . The vertical axis of the graph shows the number of differences in the average value, and the horizontal axis shows the range of the difference in the average value [m/ ^s2 ]. Both are roughly normal distributions and have similar shapes, but the magnitude of the difference in the average value is different. In FIG. 5(A), the number of differences in the average value is the largest in the range from -2 to +2, and in FIG. 5(B), the number of differences in the average value is the largest in the range from -5 to +5. Since the magnitude of the difference in the average value between the two is different, it is difficult to compare the differences with the same threshold value to determine whether the vehicle is stopped.

5(C) and (D) are graphs obtained by dividing the difference in the average values of FIG. 5(A) and (B) by the standard deviation. In FIG. 5(C), the number of differences in the average values is the largest in the range of −0.05 to +0.05 by dividing the difference in the average values by the standard deviation = 40 m/ ^S2 , and in FIG. 5(D), the number of differences in the average values is the largest in the range ^of −0.05 to +0.05 by dividing the difference in the average values by the standard deviation = 100 m/S2. In this way, the magnitude of the difference in the average values is the same in FIG. 5(C) and (D) regardless of the variation in acceleration. Therefore, it is possible to perform a stop determination using the same threshold value.

The threshold comparison unit 250 compares the difference correction value P with the threshold Th. The threshold Th is a value that can be estimated from the detection periods t1 and t2, and is set in advance. The threshold comparison unit 250 provides the comparison result to the stopped vehicle determination unit 210. If the difference correction value P<threshold Th, the stopped vehicle determination unit 210 determines that the vehicle is stopped, and if the difference correction value P≧threshold Th, it determines that the vehicle is not stopped (moving). The result of the determination of the stopped state is used, for example, to correct the zero point of the angular velocity sensor 124, making it possible to improve the accuracy of corrections made when the vehicle is stopped.

Figure 6 is a graph illustrating an example of acceleration sensor output while the vehicle is moving and while stopped, and an example of determining whether the vehicle is stopped. At time ts, no vehicle speed pulse is input, and the stop determination unit 210 uses the acceleration sensor to determine whether the vehicle is stopped. When the vehicle is moving, the average acceleration values of detection period A and detection period B are compared. Since the difference between the average values is large, it is determined that the vehicle is moving. In other words, the difference correction value P is greater than or equal to the threshold value Th.

While the vehicle is stopped, the average values of acceleration in detection periods C and D are compared. As the difference in the average values is small, it is determined that the vehicle is stopped. In other words, difference correction value P < threshold value Th. Also, during another period while the vehicle is stopped, the average values of acceleration in detection periods E and F are compared. There is more variation in acceleration than in detection periods C and D, and the difference in the average values is also larger, but correction based on the standard deviation is applied and it is determined that the vehicle is stopped. In other words, difference correction value P < threshold value Th.

In this way, according to this embodiment, when an acceleration sensor is used to determine whether a vehicle is stopped, the difference in the average values is corrected by the standard deviation of the acceleration, so that even if there is variation in the difference in the average values due to vehicle vibration, individual differences in parts, or the product environment, the stopped state can be accurately determined using the same threshold value.

In the above embodiment, an example was shown in which an acceleration sensor was used when performing a stop determination based on the vehicle speed pulse, but this is just one example. For example, the stop determination may be performed using only the acceleration sensor, regardless of the stop determination based on the vehicle speed pulse, or the stop determination may be performed using the acceleration sensor in combination with a method using other sensors (for example, a change in absolute position using GPS positioning). Furthermore, in the above embodiment, an example was shown in which the zero point of the angular velocity sensor is corrected when a stop determination is made, but it is also possible to calibrate or correct other sensors.

The above describes in detail the preferred embodiment of the present invention, but the present invention is not limited to a specific embodiment, and various modifications and variations are possible within the scope of the gist of the invention described in the claims.

100: In-vehicle device 110: Input unit 120: Position detection unit 122: GPS receiver 124: Acceleration sensor 126: Angular velocity sensor 130: Navigation unit 140: Communication unit 150: Display unit 160: Audio output unit 170: Memory unit 180: Vehicle state acquisition unit 182: Vehicle speed pulse 190: Control unit t1, t2, A, B, C, D, E, F: Detection period

Claims (6)

An electronic device mounted on a moving body and having a function of determining a stopped state of the moving body,
A detection means for detecting the acceleration of a moving object;
A storage means for storing the acceleration detected by the detection means;
a setting means for setting first and second detection periods based on a timing for determining a stopped state by using the detection means;
a determination means for reading out from said storage means the accelerations during the first detection period and the second detection period set by said setting means, and determining whether the moving object is in a stopped state based on a value obtained by dividing a difference between a first average value of the accelerations during said first detection period and a second average value of the accelerations during said second detection period by a standard deviation of the accelerations during the first detection period or the second detection period, whichever is longer ;
An electronic device having: The electronic device according to claim 1, wherein the determination means compares the value with a threshold value, and determines that the moving body is in a stopped state when the value is equal to or less than the threshold value. The electronic device according to claim 1, wherein the determination means receives a vehicle speed pulse proportional to the number of rotations of the tires of the moving body and the detection result of the detection means, determines whether the moving body is stopped based on the vehicle speed pulse, and, if the vehicle speed pulse is not input for a certain period of time, determines whether the moving body is stopped using the detection means. The electronic device further comprises:
An angular velocity detection means for detecting the angular velocity of a moving body;
4. The electronic device according to claim 1, further comprising: a correcting means for correcting an output of said angular velocity detecting means when said determining means determines that the mobile object is in a stopped state. A method for determining whether a vehicle is stopped using an acceleration sensor mounted on a moving object, comprising:
storing the acceleration detected by the acceleration sensor in a memory;
setting first and second detection periods based on a timing for determining a stopped state using the acceleration sensor;
reading out the accelerations during the first detection period and the second detection period from the memory;
A method for determining whether a moving body is stopped, the method comprising: determining whether the moving body is stopped based on a difference between a first average value of acceleration in the first detection period and a second average value of acceleration in the second detection period divided by a standard deviation of acceleration in the first detection period or the second detection period, whichever is longer . 6. The method for determining whether or not the moving body is stopped as described in claim 5, wherein the determining step receives a vehicle speed pulse proportional to the number of rotations of the tires of the moving body and the detection result of the acceleration sensor, determines whether or not the moving body is stopped based on the vehicle speed pulse, and, if a vehicle speed pulse is not input for a certain period of time, determines whether or not the moving body is stopped using the acceleration sensor.

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