JP2014085131A - Distance detection device, and distance detection program - Google Patents

Abstract

PROBLEM TO BE SOLVED: To enable distance detection device to identify plural stationary article, the device being used in detecting a distance to a target by transmitting and receiving a sound wave.SOLUTION: A sound-wave sensor performs: enhancing a set sensitivity for obtaining a reflection wave after elapsing a response period since transmitting a sound wave, the response period corresponding to a reference distance that is within a distance in which plural targets with different sizes of surfaces for receiving the sound wave can be identified (S130-S160); determining presence of a target and a distance thereto by comparing a reception level of the reflection wave obtained as a result of the transmitted wave being reflected on the target with a pre-set threshold (S170). Thus enhancing the sensitivity for a zone farther than the reference distance makes it possible to detect both targets with a small reflection surface and a large reflection surface. Further, thus lowering sensitivity for a zone closer to the reference distance detects no target with a small reflection surface, while enabling detection of a target with a large reflection surface.

Description

  The present invention relates to a distance detection device that detects a distance to a target by transmitting and receiving sound waves, and a distance detection program.

  As the distance detection device, one that distinguishes a moving object and a stationary object using the Doppler effect is known (for example, see Patent Document 1).

JP 2010-139330 A

However, the distance detection device has a problem that it is difficult to distinguish different stationary objects such as small steps and wall surfaces.
Accordingly, in view of such problems, an object of the present invention is to enable identification of a plurality of stationary objects in a distance detection device and a distance detection program that detect a distance to a target by transmitting and receiving sound waves. To do.

  The distance detection apparatus according to claim 1, wherein the target determination unit is preset with a reception level of a reflected wave obtained by reflecting the transmitted sound wave on the target. The presence or absence of the target and the distance to the target are determined by comparing with the threshold. The sensitivity changing means transmits the sound wave, and then determines the target after a corresponding time corresponding to a reference distance within a distance range in which a plurality of targets having different reflection surface sizes of the sound wave can be identified. The means sets the sensitivity for obtaining the reflected wave higher.

  According to such a distance detection device, the sensitivity is increased in a region farther than the reference distance, so that the reflective surface is small (low reflectance) and the reflective surface is large (high reflectance). ) Both can be detected. In addition, in the region closer than the reference distance, the sensitivity is lowered, so that a small reflection surface is not detected, and a large reflection surface can be detected. Therefore, a plurality of targets can be identified by detecting a change between a state where the target can be detected and a state where the target cannot be detected in a process in which the distance to the target changes with the reference distance interposed therebetween. This is particularly useful in a system that requires both detection accuracy and response, such as a system that applies a brake according to detection information of a sonar.

  Therefore, it is possible to satisfactorily identify a plurality of targets having different sizes of sound wave reflection surfaces, such as whether a target approaching the reference distance or more and less than the reference distance is a small step or a wall surface, for example. it can.

  In order to achieve the above object, a computer may be used as a distance detection program for realizing each unit constituting the distance detection device. Further, the descriptions in the claims can be arbitrarily combined as much as possible. At this time, a part of the configuration may be excluded within a range in which the object of the invention can be achieved.

It is explanatory drawing which shows schematic structure of the distance detection system 1 to which this invention was applied. 4 is a flowchart showing a detection process executed by the calculation unit 11 of the acoustic wave sensor 10. It is a graph which shows the reflected wave intensity | strength corresponding to various threshold values. It is a graph which shows the reflected wave intensity in case a target is a wall surface. It is a graph which shows the reflected wave intensity in case a target is a level | step difference. It is a graph which shows the reflected wave intensity in case a target is (phi) 400 pole. 4 is a flowchart showing avoidance processing executed by a CPU 11 of a collision avoidance control unit 40.

Embodiments according to the present invention will be described below with reference to the drawings.
[Configuration of this embodiment]
The distance detection system 1 to which the present invention is applied is mounted on a vehicle such as a passenger car, for example, and detects obstacles such as wall surfaces and steps located in front of or behind the vehicle (own vehicle) to drive the vehicle. This is a system that performs control such as braking when there is a hindrance (eg wall surface). As shown in FIG. 1, the distance detection system 1 includes a sound wave sensor 10, a sonar control unit 30, a collision avoidance control unit 40, and a brake actuator 50.

  The sonic sensor 10 and the sonar control unit 30 are connected via a communication line 4 that performs communication using, for example, the LIN protocol. The sonar control unit 30, the collision avoidance control unit 40, and the brake actuator 50 include, for example, the CAN protocol. The communication line 5 is used for communication.

  The sound wave sensor 10 has a function as a well-known sound wave sensor that detects a distance to a target that reflects sound waves by transmitting and receiving sound waves such as ultrasonic waves. In particular, the sound wave sensor 10 of the present embodiment has a function of changing the sensitivity according to the distance of the target to be detected. A function for changing the sensitivity will be described later.

  The sonic sensor 10 includes a calculation unit 11, a transmission / reception unit 12, a first amplification unit 13, a variable amplification unit 14, a second amplification unit 15, a comparison unit 16, a threshold voltage generation unit 17, and a communication unit 18. And.

  The calculation unit 11 is configured as a computer including a CPU 11a, a memory 11b, and the like, and transmits various commands to each unit configuring the sound wave sensor 10. In addition, the calculating part 11 implements processes, such as a detection process mentioned later. The memory 11b stores a distance detection program referred to in the present invention and is executed by the CPU 11a.

  The transmission / reception unit 12 transmits a sound wave in response to a command from the calculation unit 11 and receives the reflected wave from the target. And a signal is produced | generated according to the magnitude | size of the reception level of a reflected wave, and it sends to a 1st amplifier. In addition, the transmission / reception part 12 is comprised from the piezoelectric element, for example.

The first amplifying unit 13 and the second amplifying unit 15 are configured by an amplifier circuit such as an amplifier. The first amplification unit 13 amplifies the signal output from the transmission / reception unit 12 with a predetermined amplification factor.
The variable amplifying unit 14 amplifies the signal output from the first amplifying unit 13 at an arbitrary amplification factor set by the arithmetic unit 11 each time. The second amplifying unit 15 amplifies the signal output from the variable amplifying unit 14 with a predetermined amplification factor.

  The threshold voltage generation unit 17 generates a threshold voltage for comparison in accordance with a command from the calculation unit 11. The comparison unit 16 compares the threshold voltage generated by the threshold voltage generation unit 17 with the voltage of the signal output from the second amplification unit 15, and when the signal voltage exceeds the threshold voltage, the calculation unit 11 outputs a signal.

  The computing unit 11 computes the distance at which the target reflecting the sound wave is present according to the timing at which the signal from the comparing unit 16 is received. The calculation unit 11 transmits the calculation result of the distance to the target to the sonar control unit 30 via the communication unit 18 and the communication line 4. However, the communication unit 18 (the same applies to communication units 38 and 48 described later) is configured as a known communication module that performs communication via the communication lines 4 and 5.

  Next, the sonar control unit 30 includes a CPU 31, a memory 32, and a communication unit 38. The CPU 31 performs processing according to the program stored in the memory 32. Specifically, the CPU 31 controls the acoustic sensor 10 such as setting for the acoustic sensor 10, and the collision avoidance of the calculation result of the distance to the target. Processing to be transmitted to the control unit 40 is performed.

  Further, the collision avoidance control unit 40 has a function of controlling a controlled object such as the brake actuator 50 according to the detection result of the target. The collision avoidance control unit 40 includes a CPU 41, a memory 42, and a communication unit 48. The CPU 41, the memory 42, and the communication unit 48 have the same hardware configuration as the CPU 31, the memory 32, and the communication unit 38 provided in the sonar control unit 30. In addition, CPU41 of the collision avoidance control part 40 performs processes, such as an avoidance process mentioned later.

[Process of this embodiment]
In such a distance detection system 1, the calculation unit 11 (CPU 11a) of the sound wave sensor 10 performs the detection process shown in FIG. The detection process is a process for detecting the distance to the target while changing the sensitivity.

  Specifically, as shown in FIG. 2, first, it is determined whether or not the sound wave transmission timing has come (S110). Here, the sound wave is set to be transmitted at a preset period (for example, 100 ms). In this process, whether or not the transmission timing is reached by monitoring the elapsed time since the last sound wave was transmitted. Determine whether.

  If it is not the transmission timing (S110: NO), the process of S110 is repeated. Moreover, if it is a transmission timing (S110: YES), a sound wave will be transmitted via the transmission / reception part 12 (S120). In this process, for example, a sound wave is transmitted for 0.2 ms.

  Subsequently, it is determined whether or not a predetermined time (corresponding time) set in advance has elapsed after transmission of the radio wave (S130). Here, the specified time represents a time corresponding to a reference distance within a distance range in which a plurality of targets having different sizes of sound wave reflection surfaces can be identified after the sound wave is transmitted. For example, the reference distance When the length is 2 m, it is about 12 ms.

  If the specified time has not elapsed (S130: NO), the sensitivity of the sound wave sensor 10 is set to be relatively low (S140). Specifically, by setting the amplification factor by the variable amplification unit 14 to be relatively low and setting the threshold voltage to be generated by the threshold voltage generation unit 17 to be relatively high, a small step or the like on the reflection surface is not detected. In addition, a wall surface having a large reflection surface can be detected. When such a process is completed, the process proceeds to S170 described later.

  In the process of S130, if the specified time has elapsed (S130: YES), it is determined whether or not a preset measurement end time has elapsed since the sound wave was transmitted (S150). Here, as the measurement end time, a time (for example, 30 ms: equivalent to 5 m) from the start of transmission of sound waves to the end of detection of a necessary distance is set.

  If the measurement end time has not elapsed (S150: NO), the sensitivity of the sound wave sensor 10 is set to be relatively high (S160). Specifically, by setting the amplification factor by the variable amplifying unit 14 to be relatively high and setting the threshold voltage to be generated by the threshold voltage generating unit 17 to be relatively low, one having a small reflecting surface and a large reflecting surface. Be able to detect both things.

  Subsequently, when the signal based on the reflected wave exceeds the threshold voltage, the signal transmitted from the comparison unit 16 is detected, and the distance to the target is calculated based on the time after transmitting the sound wave at this time. 11 (S170), and the process proceeds to S130. If the measurement end time has elapsed in S150 (S150: YES), the detection process is terminated.

  Here, in the present embodiment, as shown in FIG. 3A, the amplification factor (gain) by the variable amplifier 14 and the threshold voltage (threshold) to be generated by the threshold voltage generator 17 are set. That is, the gain is switched to a higher gain at the reference distance (A), and the threshold voltage is switched to a smaller value at the reference distance (A).

  At this time, the wall surface (upper solid line) whose target is a large reflecting surface is detected in an area closer than the reference distance (A), but a step of 5 cm 90 ° (lower side) whose target is a small reflecting surface. The threshold voltage and the amplification factor are set so that the solid line) is not detected in the region closer than the reference distance (A). Further, the threshold voltage and the amplification factor are set so that any target is detected in a region farther than the reference distance (A).

  The threshold voltage and the amplification factor are set experimentally so that such characteristics can be obtained. In FIG. 3A, the threshold voltage is set to increase stepwise and monotonously in a region closer to the reference distance (A), and stepwise and monotonously in a region farther than the reference distance (A). Is set to be low. As described above, the sensitivity is set so that only a target having a large reflection surface is detected in an area closer than the reference distance (A) and any target is detected in an area farther than the reference distance (A). If so, it can be set to any value (threshold voltage or amplification factor).

  Here, in FIG. 4, FIG. 5, and FIG. 6 (b), it is shown whether or not the target vehicle can be detected when the host vehicle approaches the target as time passes. Is detected. In the acoustic wave sensor 10 set in this way, when the target is a wall (a target having a large reflecting surface) that needs to avoid a collision, as shown in FIG. Can also be detected from a distant area.

  Therefore, when a wall that needs to avoid a collision is closer than the reference distance (A), it is possible to quickly perform control for avoiding the collision. Further, when the target is a small step (a target having a small reflecting surface) that does not need to avoid collision, as shown in FIG. 5A, when the target is closer than the reference distance (A) , No longer detected. Therefore, control for avoiding a collision by mistake is not performed.

  Here, a comparative example in the case where the sensitivity is not changed as in the present embodiment is shown in FIGS. 3B and 3C. FIG. 3B shows an example in which the sensitivity is set so as not to detect a target having a small reflecting surface such as a step, and FIG. 3C shows sensitivity for detecting a target having a large reflecting surface at an early stage. An example of setting is shown.

  In a system using an ultrasonic sonar, in order to ensure the accuracy of the detection, it is common to determine the object detection confirmation by detecting a plurality of times (for example, three times). When sensitivity is set as shown in FIG. 3 (b), if the target is a wall that needs to avoid collision, the wall and step can be identified as shown in FIG. 4 (b). A wall cannot be detected unless it is close to a certain distance. For this reason, it may take more time to finalize the detection result and the necessary control may be delayed. In this case, if the target is a step that does not need to avoid a collision, the step is not detected as shown in FIG. .

  Next, in the case where the sensitivity as shown in FIG. 3C is set, when the target is a wall that needs to avoid a collision, as shown in FIG. Similar to the setting, since the wall can be detected at an early stage, appropriate control can be performed. However, in the case where the target does not need to avoid a collision, as shown in FIG. 5C, the detected state continues even if the distance from the step approaches, so the collision is avoided. There is a risk that control that is not necessary for this purpose is performed.

  Therefore, it has been confirmed that the configuration of the present embodiment has an advantage compared to the above example. In the configuration of the present embodiment, it is necessary to avoid a collision, but it is advantageous when detecting a φ400 pole that is a target having a smaller reflecting surface than the wall surface.

  For example, when detecting a φ400 pole, for example, an output of a reflected wave as shown in FIG. 6A is obtained, but when approaching this φ400 pole, as shown in FIG. The detection / non-detection status changes. That is, when the distance to the target is farther than the reference distance (A), the detection state is set, and at the reference distance (A), the detection state is temporarily set, but the detection state is set again. Therefore, necessary control can be performed.

  Next, avoidance processing for avoiding a vehicle collision using the detection result of the sound wave sensor 10 will be described with reference to FIG. Although this process is a process for avoiding a collision of a vehicle, the object is to make it possible to reduce the impact at the minimum even if the collision cannot be avoided.

  In the avoidance process, as shown in FIG. 7, first, the detection result of the target by the sound wave sensor 10 is acquired (S310). Then, it is determined whether or not a target has been detected (S320). In this process, even if the target is not detected in the current avoidance process, if the target is detected within a certain time (for example, within 1.0 seconds) (that the target has been detected within a certain time) Is recorded in the memory 42), the processing in S320 treats the target as detected.

  If the target is not detected (S320: NO), the avoidance process is terminated. If the target has been detected (S320: YES), the fact that the target has been detected is recorded in the memory 42 (S330). However, if the target is not detected in the current process, the process of S330 is omitted.

  Subsequently, the risk level is determined (S340). Here, the degree of danger is uniquely determined by a map or a mathematical formula prepared in advance by comprehensively considering the speed and acceleration of the host vehicle, the distance to the target, and the like. If the degree of risk is less than a predetermined reference value (S340: NO), the avoidance process is terminated.

  If the degree of risk is equal to or higher than the reference value (S340: YES), the distance to the target is compared with the reference distance (S350). Here, the reference distance is a distance corresponding to the specified time used for the determination in the process of S130.

  If the distance to the target is less than the reference distance (S350: YES), braking is applied to apply braking to the vehicle via the brake actuator 50 (S360), and the avoidance process is terminated. If the distance to the target is greater than or equal to the reference distance (S350: NO), preparation for braking is performed (S370).

  Here, the preparation for applying the brake indicates that the brake actuator 50 is operated to the extent that the brake is not applied, and the brake can be immediately applied when the brake is applied, for example, the brake pad is brought close to the brake disk.

When such processing ends, the avoidance processing ends.
[Effects of this embodiment]
In the distance detection system 1 described in detail above, the calculation unit 11 of the sound wave sensor 10 is within a distance range in which a plurality of targets having different reflection surface sizes can be identified after transmitting the sound wave. To obtain a reflected wave after the specified time (corresponding time) corresponding to the reference distance has elapsed (timing close enough to be considered to be the same as or simultaneously with the specified time and within a distance range where the target can be identified) Set a higher sensitivity. Then, the presence / absence of the target and the distance to the target are determined by comparing the reception level of the reflected wave obtained by reflecting the transmitted sound wave on the target with a preset threshold value.

  According to such a distance detection system 1, since sensitivity is high in a region farther than the reference distance, it is possible to detect both a small reflection surface and a large reflection surface. In addition, in the region closer than the reference distance, the sensitivity is lowered, so that a small reflection surface is not detected, and a large reflection surface can be detected. Therefore, a plurality of targets can be identified by detecting a change between a state where the target can be detected and a state where the target cannot be detected in a process in which the distance to the target changes with the reference distance interposed therebetween.

  Therefore, it is possible to satisfactorily identify a plurality of targets having different sizes of sound wave reflection surfaces, such as whether a target approaching the reference distance or more and less than the reference distance is a small step or a wall surface, for example. it can.

In the distance detection system 1, the calculation unit 11 of the sound wave sensor 10 sets the sensitivity in a stepwise manner.
According to such a distance detection system 1, it is possible to easily detect a target having a reference distance or more by changing the sensitivity stepwise (that is, abruptly changing the sensitivity). When the sensitivity is changed stepwise in this way, the sensitivity is preferably changed by, for example, about 6 dB or more.

  Further, in the distance detection system 1, the calculation unit 11 of the sound wave sensor 10 monotonously decreases the threshold value after the lapse of the specified time. Even in this case, it is possible to easily detect a target having a reference distance or more.

  In the distance detection system 1, the collision avoidance control unit 40 (CPU 41) prepares for braking when the target is detected at a reference distance or more, and when the target is detected at a distance less than the reference distance. The braking is applied to the vehicle.

  That is, since the sensitivity is set high below the reference distance, almost all targets can be identified, and preparations for applying braking can be made according to the identification results. Then, when the target is less than the reference distance in a state where the target is recognized at the reference distance or more, braking is applied when the target is recognized. At this time, since braking preparation is already prepared, braking can be performed promptly. In addition, although it is difficult to identify a target at a reference distance or more, since no braking is applied, malfunction can be suppressed.

[Other Embodiments]
Embodiments of the present invention are not limited to the above-described embodiments, and can take various forms as long as they belong to the technical scope of the present invention.

  For example, in the above embodiment, control is performed to apply braking when the target is less than the reference distance in a state where the target is recognized above the reference distance, but instead of control such as braking or the like In addition to the above control, a warning or the like may be notified.

Moreover, in the said embodiment, although the structure as described in all the claims was shown, the structure of Claim 2 or less is not an essential structure, and can be selectively employ | adopted arbitrarily.
[Relationship Between Configuration of Present Embodiment and Means of Present Invention]
The sound wave sensor 10 in the present embodiment corresponds to the distance detection device in the present invention. Further, among the processes in the present embodiment, the process of S170 corresponds to the target determining means in the present invention, and the processes of S130 to S160 correspond to the sensitivity changing means in the present invention.

  Further, the processes in S140 and S160 correspond to the threshold value changing means in the present invention, the process in S360 corresponds to the braking application executing means in the present invention, and the process in S370 corresponds to the braking application preparing means in the present invention. .

  DESCRIPTION OF SYMBOLS 1 ... Distance detection system, 4 ... Communication line, 5 ... Communication line, 10 ... Sound wave sensor, 11 ... Calculation part, 12 ... Transmission / reception part, 13 ... 1st amplification part, 14 ... Variable amplification part, 15 ... 2nd amplification part 16 ... comparison unit, 17 ... threshold voltage generation unit, 18 ... communication unit, 30 ... sonar control unit, 31 ... CPU, 32 ... memory, 38 ... communication unit, 40 ... collision avoidance control unit, 41 ... CPU, 42 ... Memory, 48 ... communication unit, 50 ... brake actuator.

Claims (5)

A distance detection device (10) for detecting a distance to a target by transmitting and receiving sound waves,
Target determination means for determining the presence of the target and the distance to the target by comparing the reception level of the reflected wave obtained by reflecting the transmitted sound wave on the target with a preset threshold (S170). When,
After transmitting the sound wave, the target determining means transmits the reflected wave after a corresponding time corresponding to a reference distance within a distance range in which a plurality of targets having different sound wave reflection surfaces can be identified. Sensitivity changing means (S130 to S160) for setting a higher sensitivity to obtain;
A distance detection device comprising: The distance detection apparatus according to claim 1,
The distance detection apparatus, wherein the sensitivity changing means sets the sensitivity to be higher stepwise. The distance detection apparatus according to claim 2,
The sensitivity changing means is a threshold changing means (S140, S160) for monotonously decreasing the threshold after the corresponding time has elapsed.
A distance detection device comprising: The distance detection device according to any one of claims 1 to 3,
The distance detection device is mounted on a vehicle,
Braking application preparation means (S370) for preparing for applying braking in the vehicle when a target is detected at the reference distance or more;
Braking application executing means (S360) for applying braking in the vehicle when a target is detected below the reference distance;
A distance detection device comprising:   The distance detection program for implement | achieving a computer as each means which comprises the distance detection apparatus of any one of Claims 1-4.

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