JP2018132450A - Obstacle detection device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an obstacle detection device capable of suppressing fluctuation of a detection range due to temperature and humidity without using a temperature sensor and a humidity sensor. SOLUTION: In an obstacle detection device 1 mounted on a vehicle, an ultrasonic sensor 12 transmits an ultrasonic wave and receives a reflected wave in which the ultrasonic wave is reflected by an obstacle. The storage unit 16 stores each piece of information regarding a plurality of first reverberation waveforms generated by transmission of ultrasonic waves under a plurality of environmental conditions in association with a threshold value for detecting an obstacle. The selection unit 18 identifies the first reverberation waveform corresponding to the second reverberation waveform generated by the transmission of ultrasonic waves, and determines the threshold value corresponding to the first reverberation waveform from the threshold values stored in the storage unit 16. select. The detection unit 20 detects the obstacle by comparing the magnitude of the reflected wave received by the ultrasonic sensor 12 and the threshold value selected by the selection unit 18. [Selection diagram] Figure 1

Description

  The present invention relates to an obstacle detection apparatus that detects an obstacle.

  An obstacle detection device that transmits an ultrasonic wave, receives a reflected wave reflected by the obstacle, obtains a distance to the obstacle based on the propagation time of the reflected wave, and detects the obstacle is known. (For example, refer to Patent Document 1).

JP 2003-248050 A

  Since the ultrasonic wave is attenuated by the influence of the outside air and the attenuation amount depends on the temperature and humidity, the range in which the obstacle detection device can detect the obstacle varies depending on the temperature and humidity. Therefore, depending on the temperature and humidity, the detection range may be too narrow or the detection range may be too wide, and there is a possibility that an obstacle cannot be detected properly. Although it is conceivable to provide a temperature sensor and a humidity sensor and adjust the detection range according to the temperature and humidity, the cost increases.

  This invention is made | formed in view of such a condition, The objective is to provide the obstruction detection apparatus which can suppress the fluctuation | variation of the detection range by temperature and humidity, without using a temperature sensor and a humidity sensor.

  In order to solve the above-described problem, an obstacle detection device according to an aspect of the present invention is an obstacle detection device mounted on a vehicle, which transmits an ultrasonic wave, and a reflected wave in which the ultrasonic wave is reflected by the obstacle. And each of the information related to the plurality of first reverberation waveforms generated by transmitting ultrasonic waves under a plurality of environmental conditions is stored in association with the threshold for detecting the obstacle. A storage unit and a first reverberation waveform corresponding to a second reverberation waveform generated by transmitting ultrasonic waves are specified, and a threshold value corresponding to the first reverberation waveform is selected from the threshold values stored in the storage unit. A selection unit; and a detection unit that detects an obstacle by comparing the magnitude of the reflected wave received by the ultrasonic sensor with a threshold selected by the selection unit.

  It should be noted that any combination of the above-described constituent elements and a conversion of the expression of the present invention between a method, an apparatus, a system, a recording medium, a computer program, etc. are also effective as an aspect of the present invention.

  According to the present invention, fluctuations in the detection range due to temperature and humidity can be suppressed without using a temperature sensor and a humidity sensor.

It is a block diagram which shows the structure of the obstruction detection apparatus which concerns on one Embodiment. It is a wave form diagram which shows an example of the detection signal containing the 1st reverberation waveform acquired previously of the obstacle detection apparatus of FIG. It is a wave form diagram which shows an example of the detection signal containing the 2nd reverberation waveform at the time of calibration of the obstacle detection apparatus of FIG. FIG. 4 is a diagram illustrating characteristic values of a first reverberation waveform in FIG. 2 and a second reverberation waveform in FIG. 3. It is a figure which shows the detection range which the obstacle detection apparatus of FIG. 1 can detect an obstacle. It is a figure which shows the detection range which the obstacle detection apparatus of a comparative example can detect an obstacle. It is a flowchart which shows the process of the obstruction detection apparatus 1 of FIG.

  FIG. 1 is a block diagram illustrating a configuration of an obstacle detection apparatus 1 according to an embodiment. The obstacle detection device 1 includes a transmission unit 10, an ultrasonic sensor 12, a reception unit 14, a storage unit 16, a selection unit 18, and a detection unit 20.

  The obstacle detection device 1 is provided in a vehicle such as an automobile, for example. The obstacle detection apparatus 1 performs calibration for adjusting the obstacle detection range so as to meet the current environmental conditions. The timing at which the calibration is started is not particularly limited. For example, it is assumed that the ignition switch of the vehicle is turned on or the shift lever of the vehicle is put in the back.

  The transmission unit 10 causes the ultrasonic sensor 12 to transmit ultrasonic waves for a predetermined period at a timing when calibration is started and at a predetermined transmission timing after the end of calibration. In addition, the transmission unit 10 outputs a signal indicating the transmission timing of the ultrasonic waves to the selection unit 18 and the detection unit 20.

  The ultrasonic sensor 12 transmits ultrasonic waves according to the control of the transmission unit 10. Specifically, the ultrasonic sensor 12 transmits an ultrasonic wave by vibrating a piezoelectric element (not shown) based on the electrical signal supplied from the transmission unit 10. Even when the transmission unit 10 stops supplying the electric signal, the piezoelectric element continues to vibrate for a certain time. This vibration after the supply of electric signals is stopped is called reverberation. That is, reverberation occurs in the ultrasonic sensor 12 due to the transmission of ultrasonic waves. The reverberation decays with time.

  Further, the ultrasonic sensor 12 receives a reflected wave reflected by an obstacle existing around the vehicle of the transmitted ultrasonic wave, converts the reflected wave into an electric signal, and outputs the electric signal to the receiving unit 14.

  The reception unit 14 amplifies the electrical signal output from the ultrasonic sensor 12, performs envelope detection on the amplified electrical signal, and outputs the obtained detection signal to the selection unit 18 and the detection unit 20. Since the electrical signal output from the transmission unit 10 is also input to the reception unit 14, the detection signal includes information on the transmitted ultrasonic waves. The magnitude of the detection signal, that is, the amplitude voltage represents the magnitude (amplitude) of the transmitted ultrasonic wave, reverberation or reflected wave. In the present embodiment, the amplitude voltage of the detection signal decreases as the magnitude of the transmitted ultrasonic wave, reverberation or reflected wave increases. The smaller the magnitude of the transmitted ultrasonic wave, reverberation or reflected wave, the larger the amplitude voltage of the detection signal. Contrary to this example, the amplitude voltage of the detection signal may increase as the size of the transmitted ultrasonic wave or the like increases.

  The storage unit 16 is configured by a non-volatile memory or the like, and associates each piece of information related to the plurality of first reverberation waveforms generated by transmission of ultrasonic waves under a plurality of environmental conditions with a threshold for detecting an obstacle. I remember. The plurality of environmental conditions are different in at least one of temperature and humidity. Each threshold value is a value suitable for the corresponding environmental condition. For example, the higher the temperature and humidity, the higher the threshold is set. The information regarding the plurality of first reverberation waveforms includes the magnitude of each time of the plurality of first reverberation waveforms, and is acquired in advance by operating the obstacle detection apparatus 1 in a factory or the like that manufactures the vehicle. Information on the plurality of first reverberation waveforms is acquired for each ultrasonic sensor 12. The number of the environmental condition and the first reverberation waveform is not particularly limited, but a more appropriate threshold can be selected as the number is larger.

  FIG. 2 is a waveform diagram showing an example of a detection signal including the first reverberation waveforms 111 to 114 acquired in advance by the obstacle detection apparatus 1 of FIG. The four detection signals are acquired under different environmental conditions. Each environmental condition can be associated with an attenuation coefficient m. The attenuation coefficient m represents the degree of attenuation of ultrasonic waves in the air, and changes according to temperature and humidity. Attenuation increases as the attenuation coefficient m increases. For example, the higher the temperature and humidity, the greater the attenuation coefficient m. The four detection signals correspond to attenuation coefficients m = 0.67, 0.62, 0.42, and 0.32, respectively.

  Time t0 is an ultrasonic transmission timing, and ultrasonic waves are transmitted between times t0 and t1. Reverberation occurs between times t1 and t2. Waveforms of the detection signal between times t1 and t2 are first reverberation waveforms 111 to 114. Since the characteristics of the ultrasonic sensor 12 change according to temperature and humidity, the reverberation also changes, and the first reverberation waveforms 111 to 114 are different from each other. The first reverberation waveform 111 corresponds to the attenuation coefficient m = 0.67, and the first reverberation waveform 112 corresponds to the attenuation coefficient m = 0.62. The first reverberation waveform 113 corresponds to the attenuation coefficient m = 0.42, and the first reverberation waveform 114 corresponds to the attenuation coefficient m = 0.32.

  FIG. 3 is a waveform diagram showing an example of a detection signal including the second reverberation waveform 131 at the time of calibration of the obstacle detection apparatus 1 of FIG. Times t0 to t2 correspond to times t0 to t2 in FIG. By transmitting ultrasonic waves from the ultrasonic sensor 12 at the time of calibration, a second reverberation waveform 131 is generated in the detection signal. The waveform of the detection signal at times t1 to t2 is a second reverberation waveform 131. The detection signals at times t3 to t4 correspond to the reflected waves received by the ultrasonic sensor 12.

  The selection unit 18 specifies a first reverberation waveform corresponding to the second reverberation waveform 131 and selects a threshold corresponding to the first reverberation waveform from the thresholds stored in the storage unit 16. Specifically, the selection unit 18 identifies a first reverberation waveform that is most similar to the second reverberation waveform 131 from among the plurality of first reverberation waveforms 111 to 114, and identifies the identified first reverberation waveform. A threshold corresponding to the waveform is selected. A method for specifying the first reverberation waveform similar to the second reverberation waveform 131 is not particularly limited, and a known method can be used, but in the present embodiment, the following method is used.

  The selection unit 18 uses one first reverberation waveform 111 among the plurality of first reverberation waveforms 111 to 114 as a reference. For each of the plurality of first reverberation waveforms 111 to 114, the selection unit 18 determines the magnitude of the first reverberation waveform and the magnitude of the reference first reverberation waveform 111 at predetermined times between times t1 and t2. Is calculated as a characteristic value of the first reverberation waveform.

  That is, the selection unit 18 calculates the sum of the differences between the first reverberation waveform 111 and the reference first reverberation waveform 111 at each predetermined time as the characteristic value of the first reverberation waveform 111. The selection unit 18 calculates the sum of the differences between the first reverberation waveform 112 and the reference first reverberation waveform 111 at each predetermined time as the characteristic value of the first reverberation waveform 112. The selection unit 18 calculates the sum of the differences between the first reverberation waveform 113 and the reference first reverberation waveform 111 at each predetermined time as the characteristic value of the first reverberation waveform 113. The selection unit 18 calculates the total sum of the differences between the first reverberation waveform 114 and the reference first reverberation waveform 111 at each predetermined time as the characteristic value of the first reverberation waveform 114.

  Accordingly, the characteristic value of the first reverberation waveform 111 is 0, and the first reverberation waveform having a smaller characteristic value is more similar to the reference first reverberation waveform 111. That is, the characteristic value represents the degree of similarity between each of the plurality of first reverberation waveforms 111 to 114 and the reference first reverberation waveform 111.

  Once the information about the plurality of first reverberation waveforms 111 to 114 is stored, the characteristic values of the plurality of first reverberation waveforms 111 to 114 do not change, so these characteristic values are not calculated for each calibration. It's okay. Therefore, the selection unit 18 calculates characteristic values of the plurality of first reverberation waveforms 111 to 114 in advance when information about the plurality of first reverberation waveforms 111 to 114 is stored in the storage unit 16 at a factory or the like. The characteristic value is preferably stored in the storage unit 16. Therefore, in this case, the information regarding the plurality of first reverberation waveforms 111 to 114 stored in the storage unit 16 includes characteristic values.

  The selection unit 18 calculates the characteristic value of the second reverberation waveform 131, and corresponds the first reverberation waveform having the characteristic value closest to the characteristic value of the second reverberation waveform 131 to the second reverberation waveform 131. The first reverberation waveform is specified. The selection unit 18 calculates the sum of the difference between the magnitude of the second reverberation waveform 131 and the magnitude of the reference first reverberation waveform 111 at each predetermined time as a characteristic value of the second reverberation waveform 131.

  4 is a diagram showing characteristic values of the first reverberation waveforms 111 to 114 in FIG. 2 and the second reverberation waveform 131 in FIG. In the example of FIG. 4, the characteristic value of the second reverberation waveform 131 is closest to the characteristic value of the first reverberation waveform 112 with the attenuation coefficient m = 0.62. Therefore, the first reverberation waveform 112 is identified as being most similar to the second reverberation waveform 131, and a threshold value corresponding to the identified first reverberation waveform 112 is selected. When the threshold is selected, the calibration is finished.

  The detection unit 20 detects an obstacle using the reflected ultrasonic wave transmitted at the time of calibration and the reflected ultrasonic wave transmitted after the calibration is completed. The detection unit 20 detects an obstacle by comparing the magnitude of the reflected wave received by the ultrasonic sensor 12, that is, the amplitude voltage of the detection signal corresponding to the reflected wave and the threshold value selected by the selection unit 18. . The detection unit 20 detects the presence of an obstacle when the amplitude voltage of the detection signal corresponding to the reflected wave is equal to or less than a threshold value. In this case, the detection unit 20 calculates the distance to the obstacle based on the time from the transmission timing of the ultrasonic wave to the timing at which the amplitude voltage of the detection signal becomes equal to or lower than the threshold, and the sound speed. The detection unit 20 does not detect the presence of an obstacle when the amplitude voltage of the detection signal corresponding to the reflected wave is larger than the threshold value.

  In the example of FIG. 3, the amplitude voltage of the detection signal corresponding to the reflected wave is equal to or less than the threshold at time t3a. Therefore, the detection unit 20 detects the presence of an obstacle.

  The configuration of the selection unit 18 and the detection unit 20 can be realized in hardware by a CPU, memory, or other LSI of an arbitrary computer, and is realized in software by a program loaded in the memory. Here, functional blocks realized by the cooperation are depicted. Accordingly, those skilled in the art will understand that these functional blocks can be realized in various forms only by hardware, or by a combination of hardware and software.

  FIG. 5 is a diagram showing a detection range R1 in which the obstacle detection apparatus 1 of FIG. 1 can detect an obstacle. The ultrasonic sensor 12 is provided outside the vehicle body 200 of a vehicle such as a passenger car. For example, the ultrasonic sensor 12 is provided in the vicinity of the bumper 202 at the lower rear of the vehicle body 200. In this example, the obstacle detection device 1 detects an obstacle when the vehicle backs in the direction d1, and when the obstacle is detected, the vehicle provided in the vehicle according to the distance to the obstacle. A control unit (not shown) controls a vehicle brake and the like.

  When the temperature or humidity changes, the attenuation amount of the ultrasonic wave changes, but the selection unit 18 selects a threshold value suitable for the attenuation coefficient as described above. Therefore, even if the temperature or humidity changes, the distance of the obstacle where the magnitude of the reflected wave is equal to the threshold value is substantially constant, and the detection range R1 is substantially constant. Therefore, even if the temperature or humidity changes, the possibility of erroneous detection of the road surface 300 that should not be detected is low, and obstacles such as the curb 302 higher than the road surface 300 can be detected appropriately. It can be detected at an appropriate distance.

  FIG. 6 is a diagram illustrating detection ranges R2 and R3 in which the obstacle detection device of the comparative example can detect an obstacle. The obstacle detection device of the comparative example differs from the obstacle detection device 1 of FIG. 1 in that the threshold value is a constant value. When the temperature or humidity changes, the attenuation amount of the ultrasonic wave changes. Therefore, when the threshold value is constant, the distance of the obstacle where the magnitude of the reflected wave becomes equal to the threshold value changes, and the detection range changes. . In the case of low temperature and low humidity, the detection range R2 becomes too wide, and there is a possibility that the road surface 300 that should not be detected is erroneously detected. In the case of high temperature and high humidity, the detection range R3 may become too narrow, and obstacles such as the curb 302 may not be detected, or detection of the obstacle 304 behind the vehicle may be delayed.

  Next, the overall operation of the obstacle detection apparatus 1 will be described. FIG. 7 is a flowchart showing processing of the obstacle detection apparatus 1 of FIG. When calibration is started, the ultrasonic sensor 12 transmits an ultrasonic wave (S10). Next, the selection part 18 specifies the 1st reverberation waveform similar to the 2nd reverberation waveform generated by transmission of an ultrasonic wave (S12). Next, the selection unit 18 selects a threshold value corresponding to the identified first reverberation waveform from the threshold values stored in the storage unit 16 (S14). Here, the calibration ends.

  Next, the ultrasonic sensor 12 receives the reflected wave in which the ultrasonic wave transmitted in S10 is reflected by the obstacle (S16). Next, the detection unit 20 compares the magnitude of the reflected wave received by the ultrasonic sensor 12 with the threshold value selected by the selection unit 18 to detect an obstacle (S18). When an obstacle is detected (Y in S20), the detection unit 20 notifies the detection of the obstacle to an external vehicle control unit or the like (S22), and ends the process. When no obstacle is detected (N in S20), the detection unit 20 controls the transmission unit 10, the ultrasonic sensor 12 transmits an ultrasonic wave (S24), and the process returns to S16.

  As described above, according to this embodiment, the first reverberation waveform corresponding to the second reverberation waveform 131 at the time of calibration is specified, and the threshold corresponding to the first reverberation waveform is selected. A threshold can be selected according to the temperature and humidity of the hour. Thereby, detection range R1 can be controlled according to temperature and humidity. Therefore, fluctuations in the detection range R1 due to temperature and humidity can be suppressed without using a temperature sensor and a humidity sensor.

  The storage unit 16 stores characteristic values of the plurality of first reverberation waveforms 111 to 114, calculates the characteristic value of the second reverberation waveform 131, and has a characteristic value close to the characteristic value. The reverberation waveform is specified as the first reverberation waveform corresponding to the second reverberation waveform 131. Thereby, the threshold value can be selected by calculating only the characteristic value of the second reverberation waveform 131 during calibration. Therefore, the number of calculation of characteristic values during calibration can be minimized, and the calibration time can be shortened.

  Further, since the obstacle is detected using the reflected ultrasonic wave transmitted at the time of calibration, the time from when the threshold is selected until the obstacle can be detected can be shortened. Moreover, since it is not necessary to transmit ultrasonic waves dedicated for calibration, power consumption can be reduced.

  In the above, this invention was demonstrated based on embodiment. This embodiment is an exemplification, and it is understood by those skilled in the art that various modifications can be made to each of those constituent elements or combinations of the respective treatment processes, and such modifications are also within the scope of the present invention. is there.

  For example, calibration may be performed by transmitting an ultrasonic wave dedicated for calibration. In this case, the detection unit 20 detects an obstacle using only the reflected ultrasonic wave transmitted after the threshold is selected without using the reflected ultrasonic wave transmitted during calibration. In this modified example, the characteristic value can be calculated and the threshold value can be selected at a lower speed than in the above embodiment. Therefore, the design of the selection unit 18 is facilitated and the configuration of the selection unit 18 is simplified. it can.

  In addition, a plurality of first reverberation waveforms in a plurality of environmental conditions with respect to one ultrasonic sensor 12 may be acquired in advance at a factory or the like, and the information may be shared by the plurality of obstacle detection apparatuses 1. In this case, a reverberation waveform is acquired at a factory or the like for each ultrasonic sensor 12 under one environmental condition, and the ultrasonic sensor 12 in which a reverberation waveform different from the first shared reverberation waveform by a predetermined value or more is excluded. Thus, it is possible to suppress the deterioration of the threshold selection accuracy. In this modification, the number of first reverberation waveforms acquired in advance at a factory or the like for each ultrasonic sensor 12 can be reduced.

One embodiment of the present invention is as follows.
[Item 1]
An obstacle detection device mounted on a vehicle,
An ultrasonic sensor that transmits an ultrasonic wave and receives a reflected wave of the ultrasonic wave reflected by an obstacle; and
A storage unit that stores each piece of information related to the plurality of first reverberation waveforms generated by transmission of ultrasonic waves under a plurality of environmental conditions in association with a threshold for detecting an obstacle;
A selection unit that specifies a first reverberation waveform corresponding to a second reverberation waveform generated by transmission of an ultrasonic wave, and selects a threshold corresponding to the first reverberation waveform from the thresholds stored in the storage unit; ,
A detection unit that detects an obstacle by comparing the magnitude of the reflected wave received by the ultrasonic sensor with the threshold value selected by the selection unit;
An obstacle detection device comprising:
According to this aspect, since the first reverberation waveform corresponding to the second reverberation waveform is specified and the threshold corresponding to the first reverberation waveform is selected, when transmitting / receiving ultrasonic waves for detecting an obstacle The threshold value can be selected according to the environmental conditions (temperature and humidity). Thereby, a detection range can be controlled according to temperature and humidity. Therefore, fluctuations in the detection range due to temperature and humidity can be suppressed without using a temperature sensor and a humidity sensor.

[Item 2]
The information related to the plurality of first reverberation waveforms stored in the storage unit is the similarity between each of the plurality of first reverberation waveforms and the reference first reverberation waveform among the plurality of first reverberation waveforms. Including the characteristic value to represent,
The selection unit calculates a characteristic value of the second reverberation waveform that represents the similarity between the second reverberation waveform and the reference first reverberation waveform, and has a characteristic value close to the characteristic value of the second reverberation waveform. Identifying a first reverberation waveform as a first reverberation waveform corresponding to the second reverberation waveform;
3. The obstacle detection device according to item 1, wherein
In this case, the threshold value can be selected by calculating only the characteristic value of the second reverberation waveform. Therefore, the number of times of calculating the characteristic value for the reverberation waveform can be minimized when the threshold is selected, and the processing time can be shortened.

[Item 3]
The selection unit selects the threshold using a second reverberation waveform generated by transmission of ultrasonic waves during calibration,
The detection unit detects an obstacle using an ultrasonic reflected wave transmitted at the time of the calibration,
3. The obstacle detection device according to item 1 or 2, wherein
In this case, the time from when the threshold is selected until the obstacle can be detected can be shortened. Moreover, since it is not necessary to transmit ultrasonic waves dedicated for calibration, power consumption can be reduced.

[Item 4]
The detection unit detects an obstacle using an ultrasonic reflected wave transmitted after the threshold is selected.
3. The obstacle detection device according to item 1 or 2, wherein
In this case, the calculation of the characteristic value and the selection of the threshold value can be performed at a lower speed, so that the selection unit can be easily designed and the configuration of the selection unit can be simplified.

DESCRIPTION OF SYMBOLS 1 ... Obstacle detection apparatus, 10 ... Transmission part, 12 ... Ultrasonic sensor, 14 ... Reception part, 16 ... Memory | storage part, 18 ... Selection part, 20 ... Detection part.

Claims (4)

An obstacle detection device mounted on a vehicle,
An ultrasonic sensor that transmits an ultrasonic wave and receives a reflected wave of the ultrasonic wave reflected by an obstacle; and
A storage unit that stores each piece of information related to the plurality of first reverberation waveforms generated by transmission of ultrasonic waves under a plurality of environmental conditions in association with a threshold for detecting an obstacle;
A selection unit that specifies a first reverberation waveform corresponding to a second reverberation waveform generated by transmission of an ultrasonic wave, and selects a threshold corresponding to the first reverberation waveform from the thresholds stored in the storage unit; ,
A detection unit that detects an obstacle by comparing the magnitude of the reflected wave received by the ultrasonic sensor with the threshold value selected by the selection unit;
An obstacle detection device comprising: The information related to the plurality of first reverberation waveforms stored in the storage unit is the similarity between each of the plurality of first reverberation waveforms and the reference first reverberation waveform among the plurality of first reverberation waveforms. Including the characteristic value to represent,
The selection unit calculates a characteristic value of the second reverberation waveform that represents the similarity between the second reverberation waveform and the reference first reverberation waveform, and has a characteristic value close to the characteristic value of the second reverberation waveform. Identifying a first reverberation waveform as a first reverberation waveform corresponding to the second reverberation waveform;
The obstacle detection device according to claim 1. The selection unit selects the threshold using a second reverberation waveform generated by transmission of ultrasonic waves during calibration,
The detection unit detects an obstacle using an ultrasonic reflected wave transmitted at the time of the calibration,
The obstacle detection apparatus according to claim 1 or 2, wherein The detection unit detects an obstacle using an ultrasonic reflected wave transmitted after the threshold is selected.
The obstacle detection apparatus according to claim 1 or 2, wherein

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