JP2022154560A - Distance measuring device - Google Patents

Abstract

To enable estimating a rise position of a reflection wave from the reflection wave that is reflected by an obstacle which exists at a periphery of a vehicle to return.SOLUTION: A distance measuring device comprises: an acquisition unit in which an ultrasonic sensor mounted on a vehicle acquires a reflection wave indicating an acoustic wave being reflected by an obstacle existing at a periphery of the vehicle to return, of transmission waves being transmitted; an estimation unit that estimates a rise position of the reflection wave on the basis of a straight line defining a maximum value of an amplitude of the reflection wave acquired by the acquisition unit and a value of the amplitude of the reflection wave which first exceeds a first threshold value, of the reflection wave information in a case where an intersection indicating a point that intersects between reverberation information which indicates time-dependent change of reverberation of the transmission wave transmitted by the ultrasonic sensor and reflection wave information indicating time-dependent change of the reflection wave reflected by the obstacle is lower than the first threshold value indicating a detection threshold value of reception intensity which can be detected by the ultrasonic sensor.SELECTED DRAWING: Figure 7

Description

The present disclosure relates to ranging devices.

In recent years, vehicles are equipped with a sonar for detecting obstacles around the vehicle. Also, a technique has been proposed in which a sonar is installed in a vehicle and it is determined whether or not an obstacle detected by the sonar exists in a short distance from the vehicle (see, for example, Japanese Patent Application Laid-Open No. 2002-200010).

Japanese Patent No. 6387786

However, when the vehicle and the obstacle are at a short distance, the reflected wave from the obstacle overlaps the reverberation of the sonar transmission wave, making it difficult to detect the distance to the obstacle. Therefore, when the reverberation time of the transmission wave of the sonar becomes longer, the range in which the obstacle cannot be detected expands, making it difficult to grasp the distance to the obstacle.

The present disclosure provides a distance measuring device capable of estimating the rising position of the reflected wave from the reflected wave returned after being reflected by an obstacle existing around the vehicle.

A distance measuring device according to the present disclosure acquires a reflected wave indicating a sound wave that is reflected back by an obstacle existing around the vehicle, among transmission waves transmitted by an ultrasonic sensor mounted on the vehicle. an acquisition unit, reverberation information indicating temporal changes in reverberation of the transmitted waves transmitted by the ultrasonic sensor, and reflected wave information indicating temporal changes in the reflected waves reflected by the obstacle; When the intersection indicating points is below a first threshold indicating a detection threshold of the reception intensity detectable by the ultrasonic sensor, the maximum value of the amplitude of the reflected wave obtained by the obtaining unit and the reflected wave information and an estimating unit for estimating a rising position of the reflected wave based on a straight line defining an amplitude value of the reflected wave that exceeds the first threshold value for the first time.

Since the distance measuring device according to the present disclosure can estimate the rising position of the reflected wave from the obstacle even at a short distance, it is possible to obtain more accurate information about the distance to the obstacle.

FIG. 1 is a block diagram schematically showing an example of the configuration of a vehicle including a distance measuring device according to Embodiment 1. FIG. FIG. 2 is a diagram for explaining reflection of ultrasonic waves. FIG. 3 is a received waveform state diagram for explaining received waveforms. FIG. 4 is a diagram showing an example of sonar arrangement. FIG. 5 is a diagram showing an example of the transmission cycle of ultrasonic waves. FIG. 6 is a diagram showing an example of tracking. 7 is a diagram illustrating an example of a functional configuration of the distance measuring device according to the first embodiment; FIG. FIG. 8 is a graph showing an example of the amplitude of a vibration signal when the distance measuring device according to the first embodiment receives reflected waves superimposed on reverberation. FIG. 9 is a graph showing an example of amplitude of a vibration signal when the distance measuring device according to the first embodiment receives reflected waves superimposed on reverberation. FIG. 10 is a graph showing an example of the amplitude of a vibration signal when the distance measuring device according to the first embodiment receives reflected waves superimposed on reverberation. 11 is a graph showing an example of the amplitude of a vibration signal when the distance measuring device according to Embodiment 1 receives a reflected wave; FIG. 12 is a flowchart illustrating an example of processing executed by the distance measuring device according to the first embodiment; FIG. 13 is a diagram illustrating an example of a functional configuration of a distance measuring device according to a second embodiment; FIG. FIG. 14 is a diagram explaining a method of specifying a reverberation curve. FIG. 15 is a diagram illustrating an example of adjusting the detection conditions based on the reverberation curve. FIG. 16 is a diagram showing the relationship between the saturation value and the reflected wave portion. FIG. 17 is a diagram showing the relationship between saturation values, thresholds, and reverberation curves. 18A and 18B are diagrams for explaining the timing of calculating the distance in the reflected wave. FIG. 19 is a diagram explaining a method of identifying the peak position and the rising position. 20A and 20B are diagrams for explaining the processing when the vicinity of the peak is saturated. FIG. 21 is a diagram illustrating adjustment of the offset between the peak position and the rising position. FIG. 22 is a diagram illustrating a method of estimating a rising point from the waveform of the uphill slope of the reflected wave RW1. FIG. 23 is a diagram illustrating a method of dynamic control of detection conditions according to the reverberation curve. FIG. 24 is a diagram for explaining the timing at which reflected waves cannot be detected based on the predicted distance. FIG. 25 is a flowchart for explaining a processing procedure for measuring a distance by the distance measuring device according to the second embodiment; FIG. 26 is a diagram illustrating an example of dynamically changing the threshold. FIG. 27 is a diagram showing an example of an air attenuation curve. FIG. 28 is a diagram showing an example of a modification of the threshold. FIG. 29 is a flowchart for explaining a processing procedure for measuring a distance by the distance measuring device according to the third embodiment;

Hereinafter, embodiments of a distance measuring device according to the present disclosure will be described with reference to the drawings.

(First embodiment)
FIG. 1 is a block diagram schematically showing an example of the configuration of a vehicle including a distance measuring device according to the first embodiment.

The vehicle 1 includes a sonar 10 , an ECU (Electronic Control Unit) 20 , a notification section 30 and a drive control section 40 .

The ECU 20 is a control unit that controls the sonar 10 to detect the distance to an object around the vehicle 1 and controls the operation of the vehicle 1 according to the detection result. For example, when the ECU 20 determines from the distance information obtained from the sonar 10 that an obstacle is positioned in the traveling direction of the vehicle 1 , the ECU 20 executes various controls such as braking the vehicle 1 . The ECU 20 also acquires information from various sensors other than the sonar 10 . For example, the ECU 20 acquires speed information, direction information, and acceleration information from known sensors.

The notification unit 30 notifies that an obstacle has been detected. For example, the notification unit 30 is a device that performs display output and audio output.

The drive control unit 40 is a device that controls the motion of the vehicle 1, and is a device that controls drive devices such as a brake and an engine. The sonar 10, the notification unit 30, and the drive control unit 40 are connected to the ECU 20 via a LAN cable or the like. sent in the form of a signal.

The sonar 10 includes a piezoelectric element 11 , a driving circuit 12 , a receiving circuit 13 and a controller 14 . The sonar 10 operates the drive circuit 12 under the control of the controller 14 to apply an AC voltage of 50 KHz to the piezoelectric element 11. The piezoelectric element 11 deforms according to the AC voltage and emits ultrasonic waves of the same frequency. . Since the period during which the AC voltage is applied is short, the sonar 10 emits pulsed ultrasonic waves.

As shown in FIG. 2 , pulsed ultrasonic waves emitted by a sonar 10 mounted on a vehicle 1 are reflected when they hit a road surface RS or an obstacle OB, and part of them returns to the piezoelectric element 11 . Since the piezoelectric element 11 converts pressure applied to its surface into voltage, it outputs a voltage proportional to the sound pressure of the received sound. The received sound also includes the reflected wave. Since the piezoelectric element 11 transmits and receives ultrasonic waves in this manner, it may be called a transmitting/receiving section. The receiving circuit 13 amplifies the voltage output by the piezoelectric element 11 to generate a received signal, and sends the received signal to the controller 14 .

The controller 14 acquires a received waveform based on the received signal. Here, the received waveform is obtained by envelope-detecting an AC sound wave waveform converted from sound pressure to voltage by the piezoelectric element 11 and converting it into sound wave reception intensity, which indicates the time change of the intensity of the received signal. is. A part that converts the received signal of the controller 14 into a received waveform may be called a detection part. This detection section may be provided in the receiving circuit 13 . In other words, the configuration may be such that the voltage output from the receiving circuit 13 is amplified, envelope detection is performed, and the received waveform is acquired and output to the controller 14 .

When the ultrasonic waves emitted by the sonar 10 hit an obstacle OB and are reflected, the farther the obstacle OB is, the longer it takes for the reflected wave to return. If it can be specified, the distance can be calculated based on the time difference between the transmission time and the reception time. Also, the ultrasonic waves are reflected when they hit the road surface RS. This reflected wave from the road surface is called road surface reflection.

Since the received intensity of the reflected wave from the road surface is smaller than the received intensity of the reflected wave from the obstacle OB, a curve that does not exceed the received intensity of the reflected road surface is set as a detection threshold in advance. It is determined that there is a reflected wave, and it is determined that there is no reflected wave in the portion below the detection threshold. Since the road surface reflection is not detected by the distance measuring device, it is sometimes called unnecessary reflection, or noise is not distinguished from road surface reflection and is included in noise. In general, ultrasonic waves are rapidly attenuated in the air, so the farther the reflected ultrasonic waves are, the lower the received intensity is. Therefore, the detection threshold is set to be lower as the distance is longer. Hereinafter, for the sake of convenience, the detection threshold will be referred to as a threshold.

Here, FIG. 3 shows a received waveform state diagram showing the temporal change of the reflected wave in the received waveform. The reflected wave includes an obstacle reflected portion OB and a road surface reflected portion RS. A line that encloses the waveform attached to the reflected portion OB and the road surface reflected portion RS is the envelope. As described above, the envelope can be obtained by detecting the envelope of the alternating sound wave. The vehicle 1 can detect the reflected wave OB of the obstacle according to the determined threshold value and calculate the distance based on the time delay from the transmitted wave to the reflected OB.

In FIG. 3, the left end is the time point when the sonar is emitted, and the plateau continues from there to the portion where it is attenuated according to the attenuation curve. In this flat part, the receiving circuit is saturated by the residual reverberation of the transmitted vibration, and the amplitude is therefore limited to the maximum value. It should be understood that there is a decaying waveform at . There is a part in the middle of the flat part that looks like a dent in the waveform, but this is a dent that occurs when sampling the AC sound wave waveform, and it will be flattened if envelope detection is performed. In other words, it has nothing to do with the mode of reverberation. The reverberation will be explained later.

The vehicle 1 may be provided with one sonar 10, or as shown in FIG. 4, may be provided with a plurality of sonars 10 (sonars 10a to 10h). As shown in FIG. 4, when multiple sonars 10 are provided, the sensing ranges of adjacent sonars 10 may overlap.

The vehicle 1 shown in FIG. 4 uses the sonar 10b and the sonar 10c to detect obstacles in the traveling direction when traveling straight. Also, the vehicle 1 detects an obstacle in the direction in which the vehicle 1 turns using the sonar 10a and the sonar 10d. The outer sonar 10a and sonar 10d are also called corner sonars. When an obstacle enters in the direction of travel from the side of the vehicle 1, the corner sonar first detects it.

Further, when vehicles around the vehicle 1 are also equipped with sonar, the sonar 10 may receive reflected waves of ultrasonic waves transmitted from other vehicles, resulting in erroneous detection. Therefore, as shown in FIG. 5, the sonar 10 determines that there is an obstacle when it transmits ultrasonic waves at a predetermined cycle and receives reflected waves at the same timing for a predetermined number of consecutive times. The timing at which the sonar 10 emits ultrasonic waves is when the flat portion described with reference to FIG. 3 begins, that is, when the waveform in FIG. 5 rises to the saturation level.

Next, detection and tracking of obstacles will be described with reference to FIG. FIG. 6 is a diagram schematically showing movement of the position of the reflected wave RW1 when the vehicle 1 approaches an obstacle. FIG. 6 is a flattened graph obtained by compensating the attenuation of the reflected wave due to the distance from the waveform shown in FIG.

The sonar 10 determines that there is an obstacle when the reflected wave RW1 exceeds a predetermined obstacle threshold TH. Incidentally, the obstacle threshold TH is desired to be a value higher than the noise NZ. This noise NZ includes road reflections. The time from when the ultrasonic wave is transmitted to when the reflected wave is detected is the flight time until the transmitted ultrasonic wave is reflected by an object such as an obstacle and returns. Therefore, the vehicle 1 can calculate the distance from the sonar 10 to the object by dividing the flight time by the speed of sound and halving it.

In addition, the vehicle 1 repeats object detection as shown in FIG. 6, calculates the distance each time, and performs a process called tracking to track changes in the distance information. For example, the vehicle 1 calculates the speed at which the distance of the object decreases by tracking, that is, the approach speed, and if the vehicle speed and the approach speed match within an error range, the object is not moving and is a stationary object. can be determined.

Further, the vehicle 1 can identify the coordinate information of the object by processing the FT when the sound wave reflected by one object is received by a plurality of sonars according to the principle of trilateration. Tracking on this coordinate is also included in tracking.

In addition, the piezoelectric element 11 of the sonar 10 continues to vibrate even after the transmission, that is, the application of the AC voltage is stopped. The vibration after stopping the application of the AC voltage is the reverberation RB shown in FIG. This reverberation RB draws an exponential curve and gradually attenuates. The distance measuring device of the present embodiment appropriately calculates the distance even in the range affected by the reverberation RB.

(Functional configuration diagram of rangefinder)
FIG. 7 is a diagram showing an example of the functional configuration of distance measuring device 100 according to the present embodiment. The ranging device 100 may be implemented by the controller 14 of the sonar 10 or by the ECU 20 . Moreover, the range finder 100 may be implemented by a combination of the sonar 10 and the ECU 20 . Also, the rangefinder 100 may be a device independent of the sonar 10 and the ECU 20 .

As shown in FIG. 7 , distance measuring device 100 has acquisition section 201 , determination section 202 , and estimation section 203 . Note that although the example of FIG. 7 illustrates only the functions related to the present embodiment, the functions of the distance measuring device 100 are not limited to these.

The acquisition unit 201 acquires a reflected wave representing a sound wave reflected by an obstacle OB existing around the vehicle 1 and returning from the transmission waves transmitted by the sonar 10 mounted on the vehicle 1 . Specifically, the sonar 10 mounted on the vehicle 1 transmits transmission waves. The transmitted transmission wave hits an obstacle OB existing around the vehicle 1 . When the transmitted wave hits the obstacle OB, it is reflected by the obstacle OB and the sound wave returns. The sonar 10 receives reflected waves indicative of the returning sound waves reflected by the obstacle OB. Acquisition unit 201 acquires a reflected wave received by sonar 10 .

The determination unit 202 acquires the reverberation information obtained by the obtaining unit 201, which indicates the temporal change in the reverberation of the transmitted wave transmitted by the sonar 10, and the reflected wave indicating the temporal change in the reflected wave reflected by the obstacle OB. It is determined whether or not the intersection of the information and the intersection exceeds the first threshold that indicates the detection threshold of the reception intensity that can be detected by the sonar.

Specifically, the determining unit 202 obtains the reverberation information obtained by the obtaining unit 201, which indicates the temporal change of the reverberation of the transmission wave transmitted by the sonar 10, and the temporal change of the reflected wave reflected by the obstacle OB. Acquire reflected wave information that indicates the change. The determination unit 202 synchronizes the reverberation information and the reflection information over time, which is the change over time, and superimposes the reverberation information and the reflection wave information. The determination unit 202 acquires an intersection point indicating a point where the reverberation information and the reflected wave information intersect from the result of superimposing the reverberation information and the reflected wave information. The determination unit 202 determines whether or not the obtained intersection exceeds a first threshold indicating the detection threshold of the reception intensity that can be detected by sonar.

Further, the determination unit 202 determines whether or not the maximum value of the amplitude of the reflected wave acquired by the acquisition unit 201 exceeds a second threshold indicating the threshold of the reflection intensity of the reflected wave. Specifically, the determination unit 202 acquires the maximum value of the amplitude of the reflected wave from the reflected wave information indicating the temporal change of the reflected wave reflected by the obstacle OB acquired by the acquisition unit 201 . The determination unit 202 determines whether or not the maximum value of the amplitude of the reflected wave exceeds a second threshold indicating the threshold of the reflection intensity of the reflected wave. The second threshold, which indicates the threshold of the reflection intensity reflected by the reflected wave, is set, for example, to the maximum amplitude of the reflection intensity.

Furthermore, the determination unit 202 determines whether or not the reflected wave acquired by the acquisition unit 201 exists during the reverberation period indicated by the reverberation information. Specifically, the determining unit 202 obtains the reverberation information obtained by the obtaining unit 201, which indicates the temporal change of the reverberation of the transmission wave transmitted by the sonar 10, and the temporal change of the reflected wave reflected by the obstacle OB. Acquire reflected wave information that indicates the change. The determination unit 202 synchronizes the reverberation information and the reflection information over time, which is the change over time, and superimposes the reverberation information and the reflection wave information. The determination unit 202 determines whether or not the reflected wave exists during the reverberation period indicated by the reverberation information, based on the result of superimposing the reverberation information and the reflected wave information.

The estimating unit 203 uses the determining unit 202 to obtain reverberation information indicating temporal changes in the reverberation of the transmitted waves transmitted by the sonar, and reflected wave information indicating temporal changes in the reflected waves reflected by the obstacle OB. When it is determined that the intersection point indicating the intersection point is below the first threshold value indicating the detection threshold of the reception intensity that can be detected by the sonar, the maximum value of the amplitude of the reflected wave obtained by the obtaining unit 201 and the reflected wave information are obtained. The rise position of the reflected wave is estimated based on the value of the amplitude of the reflected wave that first exceeds the first threshold and the straight line that defines the amplitude of the reflected wave.

Here, using FIG. 8, the estimating unit 203 determines the maximum value of the amplitude of the reflected wave and the value of the amplitude of the reflected wave that exceeds the first threshold for the first time in the reflected wave information. The content of estimating the rising position of the reflected wave will be described based on. FIG. 8 is a graph showing an example of the amplitude of the vibration signal when the distance measuring device 100 according to the first embodiment receives reflected waves superimposed on reverberation.

A solid line in FIG. 8 is a graph showing the amplitude of the vibration signal when the sonar 10 receives the reflected wave. A solid line 81 is an example of reverberation information, and indicates, for example, the amplitude of the drive signal and the vibration signal corresponding to the reverberation. A solid line 82 is an example of reflected wave information, and indicates, for example, the amplitude of the vibration signal corresponding to the reflected wave. Further, the saturation value of the sensor in FIG. 8 is the largest amplitude value that can be detected by the controller 14 . Even if a voltage higher than the saturation value of the sensor is applied from the receiving circuit 13 to the controller 14, the controller 14 detects the saturation value of the sensor as an amount corresponding to the voltage.

Here, as shown in FIG. 8, the first threshold 83 is the detection threshold of the reception intensity that can be detected by sonar. The maximum value 84 of the amplitude of the reflected wave is the value received by the controller 14 and indicates the same value as the saturation value of the sensor. A crossing point 85 indicates the value of the amplitude of the reflected wave that exceeds the first threshold value for the first time among the reflected wave information. A straight line 86 is a straight line connecting the maximum value 84 and the intersection point 85 . Based on a straight line 86 that connects the maximum amplitude value 84 of the reflected wave and the value of the amplitude of the reflected wave that first exceeds the first threshold among the reflected wave information, the estimating unit 203 determines that the straight line 86 and the intensity It is assumed that the intersection showing a value of 0 is the rising position 87 of the reflected wave.

Return to FIG. Further, when the determination unit 202 determines that the intersection point is equal to or greater than the first threshold, the estimation unit 203 indicates the intersection point of the maximum amplitude of the reflected wave, the reverberation information, and the reflected wave information. The content of estimating the rising position based on the straight line that defines the intersection will be described. FIG. 9 is a graph showing an example of amplitude of a vibration signal when the distance measuring device 100 according to the first embodiment receives reflected waves superimposed on reverberation.

A solid line in FIG. 9 is a graph showing the amplitude of the vibration signal when the sonar 10 receives the reflected wave. A solid line 91 is an example of reverberation information, and indicates, for example, the amplitude of the drive signal and the vibration signal corresponding to the reverberation. A solid line 92 is an example of reflected wave information, and indicates, for example, the amplitude of the vibration signal corresponding to the reflected wave. The description of the parts common to those in FIG. 8 described above will be omitted as appropriate. In FIG. 8 described above, the intersection point 85 indicates the value of the amplitude of the reflected wave that exceeds the first threshold for the first time among the reflected wave information. On the other hand, the intersection 95 in FIG. 9 represents reverberation information indicating temporal changes in the reverberation of the transmitted waves transmitted by the sonar, reflected wave information indicating temporal changes in the reflected waves reflected by the obstacle OB, and differs from FIG. 8 in that it shows the intersection of .

As shown in FIG. 9, the first threshold value 93 is a detection threshold value of the reception intensity that can be detected by sonar. The maximum value 94 of the amplitude of the reflected wave is the value received by the controller 14 and indicates the same value as the sensor saturation value. An intersection point 95 indicates a point where reverberation information and reflected wave information intersect. A straight line 96 is a straight line connecting the maximum value 94 and the intersection point 95 . The estimating unit 203 obtains the maximum value 94 of the reflected wave amplitude, reverberation information indicating the temporal change in the reverberation of the transmitted wave transmitted by the sonar, and the reverberation information indicating the temporal change in the reflected wave reflected by the obstacle OB. Based on the straight line 96 connecting the wave information and the intersection point indicating the intersection point, it is estimated that the intersection point where the straight line 96 and the intensity indicates a value of 0 is the rising position 97 of the reflected wave.

Return to FIG. Furthermore, when the determining unit 202 determines that the maximum value of the amplitude of the reflected wave is less than the first threshold, the estimating unit 203 compares the maximum value and the duration of the pulse of the transmitted wave transmitted by the sonar. The rising position is estimated based on the transmitted wave pulse length shown. Further, when the determining unit 202 determines that the reflected wave acquired by the acquiring unit 201 does not exist during the reverberation period indicated by the reverberation information, the estimating unit 203 determines the maximum amplitude of the reflected wave and the sonar estimates the rising position based on the transmitted wave pulse length, which indicates the duration of the pulse of the transmitted wave transmitted by .

Here, using FIGS. 10 and 11, the estimating unit 203 estimates the rising position based on the maximum amplitude value of the reflected wave and the transmitted wave pulse length indicating the duration of the pulse of the transmitted wave transmitted by the sonar. I will explain what to do. FIG. 10 is a graph showing an example of the amplitude of a vibration signal when the distance measuring device according to the first embodiment receives reflected waves superimposed on reverberation. 11 is a graph showing an example of the amplitude of a vibration signal when the distance measuring device according to Embodiment 1 receives a reflected wave; FIG.

A solid line in FIG. 10 is a graph showing the amplitude of the vibration signal when the sonar 10 receives the reflected wave. A solid line 111 is an example of reverberation information, and indicates, for example, the amplitude of the drive signal and the vibration signal corresponding to the reverberation. A solid line 112 is an example of reflected wave information, and indicates, for example, the amplitude of the vibration signal corresponding to the reflected wave. Descriptions of the parts common to those in FIGS. 8 and 9 described above will be omitted as appropriate. 8 and 9 described above, the maximum value of the reflected wave is greater than or equal to the first threshold. On the other hand, FIG. 10 differs from FIGS. 8 and 9 in that it shows that the maximum value of the reflected wave is less than the second threshold indicating the threshold of the reflection intensity reflected by the reflected wave. do.

As shown in FIG. 10, maximum 114 is the maximum reflected wave received by the sonar. The transmitted wave pulse length 115 is the transmitted wave pulse length indicating the connection time of the pulse of the transmitted wave transmitted by the sonar. Here, the transmission wave pulse length will be explained. The transmitted wave pulse length is the integrated time from the time when the sonar starts transmitting to the time 116 that indicates the maximum amplitude 114 of the transmitted wave. As a result, since the estimation unit 203 can know the time when the sonar started transmission, the time 116 of the maximum amplitude 114 of the reflected wave and the transmitted wave pulse length 115 indicating the pulse duration of the transmitted wave transmitted by the sonar are calculated. The rising position 117 can be estimated from the difference between .

A solid line in FIG. 11 is a graph showing the amplitude of the vibration signal when the sonar 10 receives the reflected wave. A solid line 111 in FIG. 11 is a graph showing the amplitude of the vibration signal when the sonar 10 receives the reflected wave. A solid line 111 is an example of reverberation information, and indicates, for example, the amplitude of the drive signal and the vibration signal corresponding to the reverberation. A solid line 112 is an example of reflected wave information, and indicates, for example, the amplitude of the vibration signal corresponding to the reflected wave. The description of the parts common to those in FIG. 10 described above will be omitted as appropriate. In FIG. 10 described above, the maximum value of the amplitude of the reflected wave is greater than or equal to the second threshold, whereas FIG. 11 differs in that the reflected wave does not exist during the reverberation period indicated by the reverberation information.

As shown in FIG. 11, maximum 124 is the maximum amplitude of the reflected waves received by the sonar. The transmitted wave pulse length 125 is the transmitted wave pulse length indicating the connection time of the pulse of the transmitted wave transmitted by the sonar. The estimator 203 estimates the rising position 127 from the difference between the time 126 of the maximum amplitude 124 of the reflected wave and the transmitted wave pulse length 125 indicating the duration of the pulse of the transmitted wave transmitted by the sonar.

Next, with reference to FIG. 12, an operation example of the distance measuring device 100 having the configuration described above will be described. FIG. 12 is a flowchart showing an example of processing executed by the distance measuring device 100 of the embodiment.

First, the acquisition unit 201 acquires a reflected wave representing a sound wave reflected by an obstacle OB existing around the vehicle 1 and returning from the transmission waves transmitted by the sonar 10 mounted on the vehicle 1 ( step S31).

The determination unit 202 determines whether or not the reflected wave acquired by the acquisition unit 201 exists during the reverberation period indicated by the reverberation information (step S32). Here, if the reflected wave acquired by the acquisition unit 201 exists during the reverberation period indicated by the reverberation information (step S32: Yes), the determination unit 202 proceeds to step S33. On the other hand, if the reflected wave acquired by the acquisition unit 201 in step S32 does not exist during the reverberation period indicated by the reverberation information (step S32: No), the determination unit 202 proceeds to step S37.

Further, the determination unit 202 determines whether or not the maximum value of the amplitude of the reflected wave acquired by the acquisition unit 201 exceeds the first threshold (step S33). Here, if the maximum value of the amplitude of the reflected wave acquired by the acquisition unit 201 exceeds the first threshold (step S33: Yes), the determination unit 202 proceeds to step S34. On the other hand, if the maximum value of the amplitude of the reflected wave acquired by the acquisition unit 201 does not exceed the first threshold in step S33 (step S33: No), the determination unit 202 proceeds to step S37.

Further, the determining unit 202 indicates the reverberation information indicating temporal changes in the reverberation of the transmitted waves transmitted by the sonar 10 and the temporal changes in the reflected waves reflected by the obstacle OB, which are obtained by the obtaining unit 201. It is determined whether or not the intersection point between the reflected wave information and the reflected wave information exceeds a first threshold value indicating the detection threshold value of the reception intensity that can be detected by the sonar (step S34).

Here, if the intersection of the reverberation information acquired by the acquisition unit 201 and the reflected wave information exceeds the first threshold (step S34: Yes), the determination unit 202 proceeds to step S35. On the other hand, in step S<b>34 , when the reverberation information acquired by the acquisition unit 201 and the reflected wave information and the intersection do not exceed the first threshold (step S<b>34 : No), the determination unit 202 proceeds to step S<b>36 .

The estimating unit 203 calculates an intersection point indicating the intersection of reverberation information indicating the temporal change in reverberation of the transmitted wave transmitted by the sonar and reflected wave information indicating the temporal change in the reflected wave reflected by the obstacle OB. is less than a first threshold indicating the detection threshold of the reception intensity that can be detected by sonar, the maximum value of the amplitude of the reflected wave acquired by the acquisition unit and the reflected wave information exceed the first threshold for the first time. Based on the value of the amplitude of the reflected wave and the straight line defining the value, a first estimation process for estimating the rising position of the reflected wave is performed (step S35).

Further, when the intersection of the reverberation information and the reflection information is equal to or greater than the first threshold, the estimation unit 203 determines the rising position based on the straight line defining the maximum value of the amplitude of the reflected wave and the intersection. A second estimation process is performed (step S36).

Furthermore, the estimating unit 203 determines if the maximum amplitude of the reflected wave is less than the first threshold, or if the reflected wave acquired by the acquiring unit 201 does not exist during the reverberation period indicated by the reverberation information. A third estimation process for estimating the rising position is performed based on the maximum amplitude of the reflected wave and the transmitted wave pulse length indicating the duration of the pulse of the transmitted wave transmitted by the sonar (step S37).

As described above, in the present embodiment, of the transmission waves transmitted by the sonar mounted on the vehicle, reflected waves from obstacles existing around the vehicle are acquired. Further, the intersection point between the reverberation information indicating the temporal change of the reverberation of the transmitted wave and the reflected wave information indicating the temporal change of the reflected wave indicates the detection threshold of the reception intensity that can be detected by the sonar. When it is below the threshold of 1, the rise of the reflected wave is based on a straight line that defines the maximum value of the amplitude of the reflected wave and the value of the amplitude of the reflected wave that first exceeds the first threshold among the reflected wave information. Estimate location.

According to the configuration of the present embodiment described above, even when the reflected wave from the obstacle and the reverberation of the transmitted wave from the sonar overlap, the maximum value of the amplitude of the reflected wave and the detection threshold of the reception intensity that can be detected by the sonar The rising position of the reflected wave can be estimated from the value of the amplitude of the reflected wave that first exceeds the threshold indicating . As a result, it is possible to estimate the rising position of the reflected wave from the obstacle even at a short distance, so that it is possible to obtain more accurate information about the distance to the obstacle.

(Second embodiment)
A second embodiment will be described with reference to the drawings.

Next, a second embodiment will be described. The description of the parts common to the above-described first embodiment will be appropriately omitted. In the above-described first embodiment, of the transmission waves transmitted by the ultrasonic sensor mounted on the vehicle, the reflected waves representing the sound waves reflected by the obstacles existing around the vehicle and returning are acquired. an acquisition unit, reverberation information indicating temporal changes in reverberation of the transmitted waves transmitted by the ultrasonic sensor, and reflected wave information indicating temporal changes in the reflected waves reflected by the obstacle; When the intersection indicating points is below a first threshold indicating a detection threshold of the reception intensity detectable by the ultrasonic sensor, the maximum value of the amplitude of the reflected wave obtained by the obtaining unit and the reflected wave information and an estimating unit for estimating a rising position of the reflected wave based on a straight line defining an amplitude value of the reflected wave that exceeds the first threshold value for the first time.

On the other hand, in the present embodiment, a transmitting/receiving unit that transmits a transmitted wave that is an ultrasonic wave and receives a reflected wave generated by the transmitted wave, and detects the received signal received by the transmitting/receiving unit A detection unit that obtains a received waveform that indicates a change in intensity over time, a feature amount detection unit that detects the feature amount of the reflected wave based on the received waveform, and a rangefinder that measures the distance from the range finder to the object based on the feature amount. A measured distance calculator that calculates the distance, a predicted distance calculator that calculates a predicted distance that predicts the measured distance in the next measurement based on the measured distance, and a detection condition control that controls detection conditions related to feature amount detection. and an output control unit that outputs one of the measured distance and the predicted distance as an output value, and the detection condition control unit determines, based on the predicted distance, the reverberation period during which reverberation of the transmitted wave remains in the transmission and reception unit. If the reflected wave reaches inside, the detection condition is adjusted, and the output control unit outputs the predicted distance instead of the measured distance when the predicted distance output condition for outputting the predicted distance as an output value is satisfied. It is different from the first embodiment described above in that it is output as a value.

(Functional configuration diagram of rangefinder)
A range finder 100 according to the second embodiment will be described with reference to FIG. FIG. 13 is a block diagram of the distance measuring device 100. As shown in FIG. The distance measuring device 100 includes a feature amount detection unit 101 , a measured distance calculation unit 102 , a predicted distance calculation unit 103 , a detection condition control unit 104 , an output control unit 105 , an acquisition unit 201 , a determination unit 202 and an estimation unit 203 .

The feature quantity detection unit 101 detects the feature quantity of the reflected wave RW1 generated by the reflection of the transmitted wave from the object, based on the received waveform. The feature amount detection unit 101 detects feature amounts based on the detection conditions adjusted by the detection condition control unit 104 . As will be described in detail later, the feature amount detection unit 101 detects, as feature amounts, the position information of the peak of the reflected wave RW1 on the received waveform, the position information of the intersection with the threshold value, the position information of the intersection with the saturation value, and the like. do.

The position information is a combination of the time difference between the specified time and the time when the ultrasonic wave was transmitted, and the intensity value at the specified time. It can be said that it is a combination of strengths. Hereinafter, in order to avoid complicating the description, detection of the characteristic quantity of the reflected wave RW1 is called detection of the reflected wave, and position information on the received waveform is abbreviated as position. be. Also, although the horizontal axis of the received waveform is time, it is sometimes said that the horizontal axis of the received waveform is distance on the premise that time is converted into distance.

The measured distance calculator 102 calculates the distance from the sonar 10 to an object such as an obstacle as the measured distance based on the reflected wave RW1. For example, when the measured distance calculation unit 102 detects the position of the intersection of the reflected wave RW1 from the sonar 10 and the threshold, based on the time difference between the time when the reflected wave RW1 crosses the threshold and the time when the ultrasonic wave is transmitted, , the distance from the sonar 10 to the object is calculated as the measured distance. Note that the calculation method of calculating the distance from the position of the intersection with the threshold value is only an example, and other calculation methods will be introduced later.

The predicted distance calculation unit 103 calculates a predicted distance by predicting the measured distance in the next measurement. The predicted distance calculation unit 103 calculates the predicted distance by a known method using information on the speed, acceleration, and traveling direction of the vehicle 1 and the latest measured distance. The detection condition control unit 104 controls detection conditions related to feature amount detection. The detection condition control unit 104 specifies, for example, a reverberation curve that indicates the attenuation process of reverberation, and adjusts the feature amount detection condition based on the reverberation curve. The feature quantity detection condition is, for example, a threshold. The output control unit 105 controls what is output as the distance. For example, the output control section 105 outputs either the measured distance or the predicted distance.

Here, a method for specifying the reverberation curve by the detection condition control unit 104 will be described with reference to FIG. 14 . FIG. 14 is a diagram showing a received waveform RW including a reverberation period RBTR. The received waveform RW includes the waveform of the portion of the reverberation period RBTR that indicates the attenuation process of reverberation, the reflected wave RW1 from the obstacle OB, and the reflected wave RW2 from the road surface RS. The detection condition control section 104 may specify the reverberation curve RBC by processing the waveform of the reverberation period RBTR portion of the received waveform RW.

The bottom of the received waveform RW is the reflection from the road surface RS (road surface reflection), and the rising portion from the road surface reflection is the portion of the reverberation period RBTR. The reverberation period RBTR can be said to be a period until the reverberation becomes weaker than the road surface reflection. In the reverberation period RBTR, noise and reflected waves RW1 are superimposed on the reverberation curve RBC. Since noise occurs randomly, the detection condition control section 104 acquires the received waveform RW multiple times and averages the received waveform RW during the reverberation period RBTR to remove the noise component. oppress.

Since the reflected wave from the obstacle OB does not always exist, the detection condition control unit 104 excludes the received waveform RW when the reflected wave RW1 from the obstacle OB is detected from the above averaging process. Alternatively, the received waveform RW from which the reflected wave RW2 from the obstacle OB has been removed may be averaged.

Further, since the reverberation is attenuated according to an exponential curve, the detection condition control unit 104 may specify the reverberation curve using a regression analysis method. The detection condition control unit 104 may, for example, logarithmically transform the reception intensity in the reverberation period RBTR, specify the coefficient of the exponential function in the regression equation, and specify the reverberation curve RBC.

Through such processing, the detection condition control section 104 can specify the reverberation curve based on the received waveform RW. The controller 14 can store the reverberation curve specified based on the received waveform RW and use it for subsequent detection.

Further, the reverberation attenuates according to an exponential function, but since the speed of attenuation differs depending on the individual sonar 10, the speed of attenuation is specified as a characteristic value, and this characteristic value is stored instead of the reverberation curve. You can stay. For example, the detection condition control unit 104 specifies the coefficient of the exponential function or a value related to the coefficient as a characteristic value indicating the characteristic of reverberation attenuation of the sonar 10 when a rangefinder or a vehicle equipped with the rangefinder is shipped. Alternatively, the specified characteristic value may be stored, and the reverberation curve may be specified based on the characteristic value.

For example, since there is a predetermined relationship between the impedance of the sonar 10 and the reverberation curve, the detection condition control unit 104 obtains the impedance of the sonar 10 when the rangefinder 100 is activated, and stores it as a characteristic value. may

In this way, the detection condition control unit 104 can more appropriately specify the reverberation curve by correcting the reverberation curve based on the characteristic value.

Next, an example of adjusting the detection conditions based on the reverberation curve will be described with reference to FIG. FIG. 15 is a diagram showing thresholds for detecting the reflected wave portion RW1. As shown in FIG. 15, in the reverberation period RBTR, the detection condition control unit 104 adds the noise margin NM to the reverberation curve RBC, thereby using the curve shifted upward as the threshold TH1 for detecting the reflected wave RW1. do.

The noise margin NM is, for example, approximately 3 dB. The detection condition control unit 104 also sets the level of the reflected wave from the road surface (intensity averaged on the time axis) to the level of the reflected wave from the road surface (intensity averaged on the time axis) during the road reflection period that is not the reverberation period RBTR, and adds the same noise margin as in the reverberation period RBTR as a threshold value. may be In this case, if the reverberation period RBTR is set to a period until the reverberation curve attenuates to the level of the reflected wave from the road surface, discontinuity of the threshold TH1 does not occur at the boundary between the reverberation period and the road surface reflection period.

The detection condition control section 104 may set the noise margin to a fixed value, or may calculate the noise amplitude from the received waveform during the period other than the reverberation period RBTR and determine the noise margin so as not to fall below the noise amplitude.

In this way, the detection condition control unit 104 sets the curve obtained by shifting the reverberation curve RBC upward as the threshold value TH1, and the feature amount detection unit 101 detects the reflected wave RW1 based on the threshold value TH1. It is possible to increase the possibility of detecting the reflected wave RW1 even during the period RBTR.

By the way, the received waveform data has an upper limit value, and if the intensity of the reverberation or reflected wave exceeds the intensity corresponding to the upper limit value, the data will uniformly reach the upper limit value regardless of the actual intensity. The intensity corresponding to this upper limit value is called a saturation value. Here, the relationship between the saturation value and the reflected wave RW1 will be described with reference to FIG. FIG. 16 is a diagram showing the relationship between the saturation value and reflected waves. In FIG. 16, reflected waves from an object whose distance from the sonar as a starting point gradually decreases as it approaches are shown side by side on one received waveform.

As shown in FIG. 16, when the saturation value is SV2, the reverberation intensity indicated by the reverberation curve RBC exceeds the saturation value SV2 before the reflected wave RW1c is received, so the data are uniformly at the upper limit. . Even at the timing of the reflected wave RW1c, the data continues to be the upper limit value, so the distance measuring device 100 cannot detect the reflected wave RW1c.

When the detection condition control unit 104 adjusts and lowers the reception intensity by lowering the transmission intensity of the sonar 10 or lowering the amplification degree of the reception signal, the saturation value can be relatively increased. Then, when the saturation value becomes SV1, the feature amount detection unit 101 can detect a reflected wave such as RW1c.

Even if the saturation value becomes SV1, reflected waves such as RW1d cannot be detected. At this time, since the shortest distance at which detection is possible is determined by the intersection of the reverberation curve and the saturation value, if the shortest distance at which detection is required is determined, the saturation value may be determined in advance according to the reverberation curve.

If the intensity of transmission is lowered or the degree of amplification of the received signal is lowered in order to increase the saturation value, it becomes difficult to detect weak reflected waves. Only when it is necessary to detect the distance, it may be controlled to raise the saturation value in advance, and as a result of calculating the predicted distance, it is saturated only when it is found that the reflected wave will be received during the reverberation period. It may be controlled to increase the value. The ranging device 100 can control the saturation value by acquiring information indicating the parking state from the ECU 20 .

Next, the conditions under which the reflected wave RW1 can be detected will be described with reference to FIG. FIG. 17 is a diagram showing the relationship between the saturation value SV, the threshold TH1, and the reverberation curve RBC. As shown in FIG. 17, in the reverberation period RBTR, the detection condition control unit 104 sets a curve obtained by adding a noise margin to the reverberation curve RBC as the threshold TH1, so the threshold TH1 may exceed the saturation value SV. In the section where the threshold TH1 exceeds the saturation value SV, the received data does not exceed the threshold TH1, so the range finder 100 cannot detect the reflected wave RW1.

In addition, although the reflected wave RW1d cannot be detected even in a section where the reflected wave RW1d does not reach the reverberation curve RBC, the section in which the reflected wave RW1d cannot be detected is wider because the threshold TH1 exceeds the saturation value SV. Since the threshold TH1 is determined by the reverberation curve, it can be said that the undetectable period is determined by the reverberation curve RBC. When the threshold value TH1 exceeds the saturation value SV as a result of calculating the predicted distance, the ranging device 100 may determine that the detection condition cannot be adjusted detectably.

Further, when the distance measuring device 100 tries to detect the reflected wave RW1 and fails to detect it, it may be determined that the reflected wave RW1 is not detected. In this way, when the distance measuring device 100 cannot detect the reflected wave RW1 with the threshold TH1, the output control section 105 of the distance measuring device 100 outputs the predicted distance instead of the measured distance. As a result, the distance measuring device 100 can output the distance even when the reflected wave RW1 cannot be detected due to the relationship between the reverberation curve RBC, the threshold TH1, and the saturation value SV.

Next, the position for calculating the distance in the reflected wave RW1 will be described with reference to FIG. As shown in FIG. 18A, when an ultrasonic wave is output from the sonar 10 and reflected by an obstacle OB, not only the sound wave reflected by the closest point to the sonar 10 but also the corresponding Sound waves reflected around the closest point also reach the sonar 10 .

As shown in FIG. 18(b), consider a case where an area AR2 has a projection like an area AR1. The sound waves reflected in the area AR1 at the nearest point reach the sonar 10 first, but the sound waves reflected in the surrounding area AR2, which is larger than the area AR1 and reaches the sonar 10 later, tend to be stronger. .

Therefore, as shown in FIG. 18(c), the reflected wave RW1 forms two mountains having signal intensity peaks PP1 and PP2. Alternatively, since the sonar is equipped for anti-collision purposes and the distance required for anti-collision is the distance to the nearest point, the faster PP1 should be chosen to calculate the distance.

However, depending on the detection threshold, it is not always possible to separate and detect the two peaks, and the peak position when detected as one combined peak is the position of PP2, which has a higher intensity. Also, when only one of the two peaks is detected, there is a high probability that PP2, which has a higher intensity, will be detected. Therefore, it is desirable to calculate the distance based on the rise time point SP instead of the signal intensity peak points PP1 and PP2.

However, during the reverberation period, the bottom portion of the reflected wave is hidden by the reverberation, so the waveform of the reflected wave cannot be observed near the rising point SP. Therefore, as shown in FIG. 18(d), the measurement distance calculation unit 102, for example, identifies the peak position and the rise position when the reflected wave RW1a is detected, and calculates the time difference between the peak time and the rise time. is calculated. The rising position is difficult to estimate at the time of the reflected wave RW1c because it is hidden by the reverberation, but at the time of the reflected wave RW1a, the influence of the reverberation and road surface reflection is small, so it can be estimated with a relatively small error.

Assuming that the time difference between the peak position and the rise position is the same even at the time of the reflected wave RW1c, the measured distance calculation unit 102 can estimate the rise position from the peak position at the time of the reflected wave RW1c and the above time difference. Even if the difference between the intensity values of the reflected wave and the reverberation is small, the peak position can be specified, so the rising position can be specified even if the distance is short.

Next, a method for identifying the peak position and the rising position will be described with reference to FIG. 19 . The true rise time is the time when the intensity of the reflected wave rises from zero, but as shown by the reverberation curve RBC, the reverberation decays according to an exponential function, so the received waveform never becomes zero. In other words, a waveform in which the intensity of the reflected wave rises from zero cannot be observed. Therefore, a practical zero level ZL larger than zero is determined, and the intersection of the reflected wave and the line of the zero level ZL is defined as a practical rising point.

FIG. 19(a) defines the practical zero level ZL as −50 dB, for example, and the point at which the practical zero level and the intensity distribution of the reflected wave intersect, that is, the intersection point of the zero level ZL and the reflected wave RW1. An example of a typical rising time is shown. However, near the point where the reflected wave intersects the zero level ZL, the reflected wave is hidden due to reverberation and road surface reflection and cannot be observed. processing to extend to the line of

FIG. 19B shows an example in which the point of intersection of the threshold TH1 and the intensity distribution of the reflected wave RW1, that is, the point of intersection of the threshold TH1 and the reflected wave RW1, is set as the practical rising point. In this case, since the rise time is determined by comparing the waveform of the reflected wave within the observable range with the threshold, the implementation is easier. In terms of accuracy, the latter can be said to be inferior in accuracy because the difference between the practical start-up time and the true start-up time is large, but it can be said that there is not much difference, so depending on the required accuracy, the latter is adopted. may

In addition, since noise overlaps the reflected wave, the point at which the maximum value is obtained changes depending on the position where the noise is added. can become

FIG. 19(c) shows a method of stably identifying the peak time. For example, the point of intersection of the threshold value and the reflected wave RW1 and the point of time when the intensity of the downward slope of the reflected wave RW1 is the same as that of the point of intersection are obtained, and the middle point of these points of time is defined as the peak point. Thus, by using the waveform information of the entire observable reflected wave RW1, the distance can be stably calculated even if the reflected wave contains noise.

Next, the processing when the vicinity of the peak is saturated will be described with reference to FIG. The method of identifying two points on a line with the same intensity on the uphill slope and downhill slope of the peak and estimating that there is a peak at the midpoint of the two points shown in FIG. 19(c) is geometrically It can be rephrased as an operation of approximating the waveform of the reflected wave RW1 by an isosceles triangle and applying the two vertices on the lower side to the upward slope and the downward slope. Since this method uses the points on the uphill slope and the points on the downhill slope that sandwich the peak, and does not use the waveform near the peak, it can be applied even when the waveform near the peak cannot be observed due to saturation.

The point at which the reflected wave RW1 is fitted to the lower left vertex of the isosceles triangle may be the intersection point between the reflected wave RW1 and the reverberation curve, or the intersection point with the road surface reflection curve, as shown in FIG. may The RBC in FIG. 20(a) is a continuous curve of the reverberation curve and the road surface reflection curve. The road surface reflection curve is obtained by estimating the intensity curve of the road surface reflection when there is no obstacle, and is obtained by the same method as the method of estimating the reverberation curve from the received waveform described above.

Furthermore, as shown in FIG. 20(b), the lower left vertex of the isosceles triangle may be the intersection of the reflected wave RW1 and the threshold TH1. As in the reflected wave RW1c in FIGS. 20A and 20B, when the vicinity of the peak is saturated, the intensity of the peak cannot be specified. is no problem.

FIG. 20(c) shows a method of applying the vertex of the lower side of the isosceles triangle to the oblique side, and the vicinity of the vertex is drawn enlarged. SV is the level of reception strength corresponding to the saturation value, and is called the saturation value SV. In the section where the reflection intensity curve exceeds the saturation value SV, the waveform data is saturated at the maximum value, so the values are the same. The maximum value is, for example, 255 if the waveform data is 8-bit data.

That is, when the reflection intensity curve exceeds the saturation value SV, the position of the peak of the reflected wave cannot be specified as the point where the waveform data takes the maximum value. However, if the lower side of the isosceles triangle approximated to the waveform of the peak portion is from the left end to the right end of the section where the waveform data of the reflected wave RW1d is saturated at the maximum value, it can be identified that the peak is at the midpoint. .

This method is applicable only when the peak of the reflected wave exceeds the saturation value SV. Otherwise, as the lower side of the isosceles triangle, the intensity value at the intersection of the reflected wave RW1 and the reverberation curve or the intensity value at the intersection with the road surface reflection curve is used as the reference intensity value instead of the saturation value SV, and the waveform data is used as the reference. A method may be applied in which the range exceeding the intensity value is defined as the lower side of an isosceles triangle, and a peak is found at the distance between the midpoints of the lower side.

Next, the adjustment of the offset between the peak position and the rising position will be described with reference to FIG. In order to simplify the explanation in FIG. 20 and the like, it is assumed that the offset between the peak position and the rising position is constant, but the offset may be adjusted. The offset between the peak position and the rising position can be rephrased as the difference between the distance to the maximum reflecting surface and the distance to the nearest point (shortest distance). This distance difference depends on the shape of the object and may change when approaching.

FIG. 21(a) is a layout diagram when an obstacle OB such as a support is located in front of the guardrail GD. The shortest distance is the distance to the obstacle OB, and the distance to the maximum reflecting surface is approximately the distance to the guardrail GD. In FIG. 21(b), the closest point is on the guardrail GD. The maximum reflection surface is within the range where the sound wave hits, and when the sonar 10 is at position A, it is far by the distance difference DS1.

As the sonar 10 approaches the sonar position B, the range hit by the sound wave narrows while maintaining a similarity relationship. Therefore, the distance difference DS2 between the distance to the maximum reflecting surface and the distance to the nearest point is smaller than the distance difference DS1 when the sonar 10 is at the sonar position A in proportion to the distance to the guardrail GD.

In the case of FIG. 21(b), since the distance to GD is about half, the distance difference DS2 and the distance difference DS1 are also about half. When the object has a convex portion as shown in FIG. 21(a), the width of the reflected wave is wide and the peak is split into two. It becomes a narrow, sharp reflected wave, and the closer it gets to the object, the sharper it becomes.

Therefore, the shape of the obstacle OB may be estimated, and whether or not to adjust the offset may be determined according to the estimation result. For example, if the offset between the peak position and the rising position is small at position A, it may be determined that there is no convex portion, and correction may be added to reduce the offset in proportion to the distance.

Next, a method for estimating the rising point from the waveform of the reflected wave RW1 on the uphill slope will be described with reference to FIG. Up to this point, the position of the peak of the reflected wave RW1 is specified, the offset between the rising position and the peak position is specified before the object approaches, and when the object approaches, the offset (or corrected offset) from the peak position is Although the method of estimating the pulled position as the rising position has been described, the rising position may be estimated from the data of the uphill slope of the peak.

This method can be rephrased as a process of approximating the entire received waveform of the reflected wave with a triangle, identifying the oblique side as a straight line passing through two points on the received waveform, and determining the lower left vertex. If the zero reference of the intensity of the rising position, that is, the intensity of the reflected wave is -50 dB, for example, the rising position is specified as the intersection of the -50 dB line and a straight line passing through two points on the received waveform, which is the oblique side.

In the case of FIG. 22A, the oblique side has a point P1 that is the intersection of the reflected wave and the saturation value SV, a point P2 that is the intersection of the reflected wave and the threshold value, and a point P3 that is the intersection of the reflected wave and the reverberation curve. The oblique side can be specified by selecting any two points from the points P1 to P3. For example, when the point P3 is greatly deviated from the line connecting the points P1 and P2, the oblique side may be identified by the points P1 and P2, otherwise the oblique side may be identified by the points P2 and P3.

In the case of FIG. 22(b), since the point P2 exceeds the saturation value SV and cannot be specified, the oblique side can be specified by the points P1 and P3. In the case of FIG. 22(c), since there is no point P1 that is the intersection with the saturation value SV, the oblique side can be specified by the points P2 and P3.

Next, with reference to FIG. 23, a method of dynamically controlling the detection conditions according to the reverberation curve will be described. When specifying the rising position from two points on the oblique side of the reflected wave RW1, it is better to have a margin of a predetermined value or more between the two points. For example, until the state of FIG. 23(a) is reached, there is a margin M1 of a predetermined threshold value (for example, 10 dB) or more between the point P4, which is the intersection point of the reflected wave RW1 and the reverberation curve RBC, and the saturation value SV. , and is slightly below the margin M1 at the time of FIG. 23(a).

If the arrival time of the reflected wave RW1 becomes earlier without changing the saturation value SV in the state of FIG. Since P4 exceeds the saturation value SV at the exceeding position, it becomes impossible to specify the rising position using P4.

At this time, the detection condition control unit 104 uses the predicted distance calculated by the predicted distance calculation unit 103 to determine the oblique side of the reflected wave RW1 and the reverberation curve RBC in the next detection from the previous approach speed of the vehicle 1. The intersection point P5 is predicted, and the transmission intensity or amplification degree of the sonar 10 is adjusted so that the point P5 and the saturation value SV exceed the margin M1. In the case of dynamically controlling the saturation value SV, digital control of the transmission strength is less prone to time delays and more accurate than adjusting the amplification in an analog circuit.

When the object approaches as predicted, the state shown in FIG. 23(b) is obtained. If the prediction and adjustment of the saturation value SV are repeated here, the state shown in FIG. 23(c) is obtained. If the saturation value SV remains as shown in FIG. 23(a), when the reflected wave RW1 approaches over the line L1, the reverberation exceeds the saturation value SV and becomes undetectable. However, as described above, by controlling the saturation value SV according to the predicted distance of the object and the saturation curve, it is possible to detect even if the point P4, which is the intersection of the reflected wave RW1 and the reverberation curve RBC, crosses the line L1. It's becoming

In this manner, the detection condition control unit 104 predicts the position of the reflected wave RW1 included in the received waveform RW based on the predicted distance, identifies the intersection point between the predicted reflected wave RW1 and the reverberation curve RBC, and determines the intersection point. and the margin to the saturation value. As a result, the range finder 100 can widen the range in which the distance can be measured despite the influence of reverberation by increasing the saturation value SV.

Next, with reference to FIG. 24, conditions for determining that the reflected wave RW1 cannot be detected based on the predicted distance will be described. A case where the intersection of the reflected wave RW1 and the threshold is used will be described below, but in the method of specifying the rising position from two points on the oblique side of the reflected wave RW1, it is possible not to use the intersection of the reflected wave RW1 and the threshold. , can be applied to two arbitrarily selected points.

When the saturation value SV is not dynamically controlled, DS3 is the distance between the intersection point P11 of the oblique side of the reflected wave RW1 and the saturation value SV and the intersection point of the reverberation curve RBC and the saturation value SV in FIG. 24(a). . In the case of FIG. 24(a), the rising position of the reflected wave RW1 is determined by extending a straight line connecting the intersection point P11 on the oblique side of the reflected wave RW1 and the intersection point P12 between the oblique side of the reflected wave RW1 and the reverberation curve RBC. can be estimated.

However, as the object approaches from the state in FIG. and the intersection point P12 of the oblique side of the reflected wave RW1 overlap to form one point. Therefore, the rising position of the reflected wave cannot be specified by extending the line connecting the two points. In other words, the distance measuring device 100 may determine that the reflected wave RW1 cannot be detected after the distance DS3 has progressed from the distance shown in FIG. 24(a).

Further, as shown in FIG. 24B, even if the distance traveled by the reflected wave RW1 is less than the distance DS3, it becomes difficult to stably identify the rising position of the reflected wave RW1 when the two points are close to each other. Therefore, it may be determined that the reflected wave RW1 cannot be detected even when the difference between the intensity values at the two points is less than a predetermined value (for example, 3 dB).

Further, as shown in FIG. 24(c), when the reflected wave RW1 does not cross the saturation value SV and does not generate an intersection point, the method of identifying the rising position from two points on the oblique side of the reflected wave RW1 cannot be applied. , the reflected wave RW1 cannot be detected.

Furthermore, when using the intersection of the reflected wave RW1 and the threshold, the intersection of the reflected wave RW1 and the threshold does not occur, or the intersection of the reflected wave RW1 and the threshold and the intersection of the reflected wave RW1 and the reverberation curve RBC Similarly, when the difference between the intensity values of RW1 and RW1 is less than a predetermined value, it may be determined that the reflected wave RW1 cannot be detected. When it is determined that the reflected wave RW1 cannot be detected due to any condition, the rangefinder 100 outputs the predicted distance instead of the measured distance.

Next, a processing procedure for distance measurement by the distance measuring device 100 will be described with reference to FIG. 25 . First, the feature amount detection unit 101 of the range finder 100 acquires the received waveform RW (step S1), and detects the feature amount of the reflected wave RW1 based on the detection conditions controlled by the detection condition control unit 104. FIG.

When the feature amount of the reflected wave RW1 is detected, for example, when the position of the intersection of the reflected wave RW1 and the threshold value TH is specified, the measurement distance calculation unit 102 calculates the feature amount of the reflected wave RW1 (in this case, on the received waveform from the origin to the intersection with the threshold value), the measured distance is calculated (step S2). The predicted distance calculation unit 103 calculates the predicted distance based on the vehicle travel information such as the speed of the vehicle 1 and the measured distance (step S3).

Based on the predicted distance and the reverberation curve RBC specified in advance, when the predicted distance of the obstacle OB falls within the reverberation period, the detection condition control unit 104 sets the detection condition (threshold value TH) to the reverberation curve RBC. The threshold value TH1 is corrected to exceed it (step S4). At this time, the threshold TH1 may be a value obtained by adding, for example, a predetermined margin to the reverberation intensity value at the predicted distance of the obstacle OB.

When the received waveform RW is acquired next time, the feature amount detection unit 101 detects the feature amount of the reflected wave RW1 based on the new detection conditions, and calculates the measured distance based on the feature amount of the reflected wave RW1. (Step S5). Thus, the output control unit 105 outputs a new measured distance (step S6).

As described above, the distance measuring device 100 adjusts the detection conditions for the reflected wave RW1 based on the predicted distance when the position of the obstacle OB belongs to a position affected by reverberation. For example, the distance measuring device 100 detects the reflected wave RW1 based on the threshold TH1 exceeding the reverberation curve RBC.

Thereby, the distance measuring device 100 can calculate the distance to the obstacle OB even when the obstacle OB is located at a position affected by reverberation. Since the reverberation curve RBC can be specified before detecting the obstacle, the threshold TH1 can be specified before detecting the obstacle. In other words, step S4 may be executed only for the first time after the range finder 100 is activated, and thereafter the set detection conditions may not be changed. In this way, when the threshold value TH1, which is the detection condition, is determined before a series of detections is performed and is not changed, it can be said that the detection condition is statically controlled.

The process of step S4 may be executed only the first time the predicted distance of the obstacle OB enters the reverberation period, and may be skipped from the second time. It may be executed every time while it is in . In these cases, it can be said that the detection conditions are dynamically controlled because the detection conditions are changed in accordance with the reverberation curve at each time every time a series of detections are performed.

(Third Embodiment)
In the third embodiment, the distance measuring device 100 sets the threshold for detecting the reflected wave RW1 to the intensity of the reflected wave RW1 when the position of the obstacle OB belongs to a position affected by reverberation, based on the predicted distance. An example of dynamic change based on is explained.

Here, an example of dynamically changing the threshold will be described with reference to FIG. When the distance measuring device 100 determines that the position of the obstacle OB belongs to the position affected by reverberation based on the predicted distance, the detection condition control section 104 sets the threshold for detecting the reflected wave RW1 to the reflected wave. Change based on the intensity of RW1.

For example, as shown in FIG. 26, the detection condition control unit 104 sets the threshold higher as the reflected wave RW1 approaches. That is, the detection condition control unit 104 sets the threshold TH12 for the position of the reflected wave RW1b to be higher than the threshold TH11 for the position of the reflected wave RW1a. In this way, since the rangefinder 100 dynamically increases the threshold, it is possible to calculate the distance even at a position near the sonar 10 where the degree of influence of reverberation increases.

Specifically, the detection condition control unit 104 may dynamically change the threshold based on the transition of the peak value of the reflected wave RW1. In FIG. 26, the predicted value of the intensity value of the peak of the reflected wave RW1b at the next predicted distance is obtained based on the intensity value of the peak of the reflected wave RW1a, and a predetermined value is obtained from the intensity value of the peak at the next predicted distance. The subtracted value is used as the threshold TH12 in the next detection.

When the reflected wave RW1b is received, the next predicted distance is calculated, the predicted intensity value of the peak of the reflected wave RW1c at the next predicted distance is obtained, and the threshold value TH13 for the next detection is obtained. dynamically repeats the settings of Note that the detection condition control section 104 may predict the transition of the peak value of the reflected wave RW1b based on the air attenuation factor.

Here, FIG. 27 shows an example of an air attenuation curve. FIG. 27 is a diagram showing an example of an air attenuation curve for each temperature. The vertical axis of the graph in FIG. 27 is the strength of the received signal, and the horizontal axis is the distance. It shows that the intensity of the received signal decreases as the distance increases at any temperature. FIG. 27 also shows that the strength of the received signal is affected by temperature, and that the lower the temperature, the less the strength of the received signal decreases.

Next, FIG. 28 shows an example of the form of the threshold. For example, as shown in FIG. 28(a), the thresholds TH11 to TH14 may be curved, or as shown in FIG. 28(b), the thresholds TH21 to TH24 may be polygonal. can be Also, as shown in FIG. 28(c), the thresholds TH31 to TH34 may be stepped.

As described above, the threshold TH may be dynamically updated each time a reflected wave is received. may be obtained as a predicted received signal strength curve, and a curved threshold as shown in FIG. 28(a) may be set based on the predicted received signal strength curve. The set threshold may be updated each time the reflected wave RW1b or the reflected wave RW1c is received, or may be maintained on the condition that the reflected wave changes as predicted.

Moreover, the detection condition control unit 104 may further set the threshold such that the threshold is above the reverberation curve RBC. That is, when setting the threshold values shown in FIG. 28, it may be added as a condition to be above the reverberation curve RBC. For example, if the threshold set according to the predicted reception strength curve is below the reverberation curve RBC in some section, the threshold in that section may be corrected to be above the reverberation curve RBC.

Next, a processing procedure for distance measurement by the distance measuring device 100 according to the third embodiment will be described with reference to FIG. 29 .

First, the sonar 10 transmits ultrasonic waves (step S11). The feature amount detection unit 101 acquires the received waveform RW (step S12). When the signal intensity of the reflected wave is equal to or greater than the threshold value (step S13: Yes), the feature amount detection unit 101 detects the feature amount of the reflected wave RW1, and the measured distance calculation unit 102 calculates the position of the reflected wave RW1. (step S14).

When the ECU 20 determines that the calculated distance is within the warning range (step S15: Yes), the ECU 20 causes the notification unit 30 to display/audio output based on the warning (step S16). Further, when the ECU 20 determines that the calculated distance is within the collision determination range (step S17: Yes), the ECU 20 causes the drive control section 40 to operate the brake (step S18).

If the distance belongs to the reverberation influence range (step S19: Yes), the detection condition control unit 104 acquires the peak value of the reflected wave RW1 (step S20). Subsequently, the detection condition control unit 104 estimates the peak value of the reflected wave RW1 in the next reception (step S21).

For example, the detection condition control section 104 may estimate the peak value of the reflected wave RW1 in the next reception based on the degree of increase in the peak value of the past reflected wave RW1. That is, the detection condition control unit 104 stores in advance information that associates the distance and the signal strength of the reflected wave RW1, and estimates the peak value of the reflected wave RW1 in the next reception based on the information. Good (step S21). Alternatively, the detection condition control section 104 may estimate the peak value of the reflected wave RW1 at the predicted distance from the peak value of the reflected wave RW1, the air attenuation curve, and the temperature information.

The detection condition control unit 104 updates the threshold based on the estimated peak value of the reflected wave RW1 (step S22). Since such threshold control is repeated while the vehicle is running, if the vehicle 1 is not stopped (step S23: No), the process proceeds to step S11. In this case, in step S13, the feature amount detection unit 101 detects the feature amount using the new threshold.

As described above, when the reflected wave arrives during the reverberation period, the distance measuring device 100 dynamically changes the threshold for detecting the feature amount based on the transition of the feature amount. Even if an obstacle OB is positioned at the position, the distance to the obstacle OB can be calculated.

A program to be executed by the distance measuring device 100 of the present embodiment is preinstalled in a ROM or the like and provided.

A program executed by the distance measuring device 100 of the present embodiment is a file in an installable format or an executable format, and can be stored in a computer such as a CD-ROM, a flexible disk (FD), a CD-R, a DVD (Digital Versatile Disk), etc. may be recorded on a recording medium readable by .

Furthermore, the program executed by the distance measuring device 100 of this embodiment may be stored in a computer connected to a network such as the Internet, and may be provided by being downloaded via the network. Also, the program executed by the distance measuring device of this embodiment may be provided or distributed via a network such as the Internet.

While several embodiments of the invention have been described, these embodiments have been presented by way of example and are not intended to limit the scope of the invention. These embodiments can be implemented in various other forms, and various omissions, replacements, and modifications can be made without departing from the scope of the invention. These embodiments and their modifications are included in the scope and spirit of the invention, as well as the scope of the invention described in the claims and equivalents thereof.

1 vehicle 10 sonar 20 ECU
30 reporting unit 40 drive control unit 100 distance measuring device 101 feature amount detection unit 102 measured distance calculation unit 103 predicted distance calculation unit 104 detection condition control unit 105 output control unit 201 acquisition unit 202 determination unit 203 estimation unit

Claims (4)

A ranging device that can be mounted on a vehicle,
an acquisition unit that acquires, from among transmitted waves transmitted by an ultrasonic sensor mounted on a vehicle, a reflected wave that indicates a sound wave that returns after being reflected by an obstacle existing in the vicinity of the vehicle;
A point of intersection indicating a point where reverberation information indicating temporal changes in reverberation of the transmitted waves transmitted by the ultrasonic sensor and reflected wave information indicating temporal changes in the reflected waves reflected by the obstacle intersect. is below a first threshold indicating the detection threshold of the reception intensity that can be detected by the ultrasonic sensor,
Based on a straight line that defines the maximum value of the amplitude of the reflected wave acquired by the acquisition unit and the value of the amplitude of the reflected wave that first exceeds the first threshold among the reflected wave information, an estimating unit that estimates a rising position of the reflected wave;
A rangefinder with a The estimation unit
If the intersection is greater than or equal to the first threshold,
estimating the rising position based on a straight line defining the maximum value and the intersection;
The distance measuring device according to claim 1. The estimation unit
when the maximum value is less than a second threshold indicating the threshold of the reflection intensity reflected by the reflected wave; or
When the reflected wave acquired by the acquisition unit does not exist during the reverberation period indicated by the reverberation information,
estimating the rising position based on the maximum value and a transmitted wave pulse length indicating the duration of the pulse of the transmitted wave transmitted by the ultrasonic sensor;
3. The distance measuring device according to claim 1 or 2. a transmitting/receiving unit that transmits a transmission wave that is an ultrasonic wave and receives a reflected wave generated by the transmission wave;
a detection unit for detecting a received signal received by the transmitting/receiving unit and obtaining a received waveform indicating a temporal change in strength of the received signal;
a feature amount detection unit that detects a feature amount of the reflected wave based on the received waveform;
a measured distance calculation unit that calculates a distance from the distance measuring device to an object as a measured distance based on the feature quantity;
A predicted distance calculation unit that calculates a predicted distance obtained by predicting the measured distance in the next measurement based on the measured distance;
a detection condition control unit that controls detection conditions related to detection of the feature quantity;
an output control unit that outputs one of the measured distance and the predicted distance as an output value;
with
The detection condition control unit adjusts the detection condition based on the predicted distance when the reflected wave reaches the transmission/reception unit during a reverberation period in which reverberation of the transmission wave remains,
The output control unit outputs the predicted distance as an output value instead of the measured distance when a predicted distance output condition for outputting the predicted distance as an output value is satisfied.
The distance measuring device according to any one of claims 1 to 3.

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