JP6218061B2 - Object detection device - Google Patents

Description

  The present invention relates to an object detection device that outputs a distance to a detection target.

  Conventionally, there has been an ultrasonic sensor that determines that a detection target has been detected by measuring a time difference between transmitting an ultrasonic wave to a monitoring area and receiving a reflected wave from an object (see, for example, Patent Document 1).

  The receiving unit that receives the reflected wave from the object also receives a wave component (noise) other than the reflected wave from the obstacle. Therefore, in order to prevent erroneous detection due to noise, in the obstacle detection device of Patent Document 1, when a time difference measured a plurality of times falls within an allowable error continuously for a predetermined number of times, a stationary object exists. It is estimated.

Japanese Patent Laid-Open No. 2-19785

  In the conventional object detection apparatus, the distance to the target object is obtained from the time difference when the reflected wave is last detected or the average value of the time differences for a plurality of times when the reflected wave is detected. Therefore, when an erroneous distance is detected due to noise or the like, the object detection device may output a distance different from the original distance to the target object. In addition, when the object detection device is moving, the time difference until the reflected wave from the object is received changes, so the time difference measured multiple times deviates from the allowable error, and false detection is made when there is no object. There was also a possibility.

  The present invention has been made in view of the above problems, and an object of the present invention is to provide an object detection device that can more accurately determine the distance to an object even when the object detection device itself is moving. It is to provide.

In order to solve the above problems, an object detection device of the present invention is an object detection device that outputs a distance to a detection target, and includes a transmission / reception unit, a distance calculation unit, a determination unit, and an output unit. . The transceiver unit transmits a pulse wave propagating through space periodically receives a reflected wave reflected by the detection subject. The distance calculation unit obtains a distance to the detection object based on a propagation time from when the transmission / reception unit transmits the pulse wave to when the reflection wave is received. The determination unit determines whether the reflected wave received by the transmission / reception unit is a reflected wave from the detection target. When the determination unit determines that the transmission / reception unit has received a reflected wave from the detection target, the output unit outputs the distance obtained by the distance calculation unit. The determination unit uses the speed of change of the distance to the detection target due to the movement of the object detection device as the allowable change width of the distance obtained by the distance calculation unit , and the self-speed of the object detection device. Set in conjunction with. If the difference between the distance obtained by the distance calculation unit last time and the distance obtained this time is within the range of the change width for a predetermined number of times, the transmission / reception unit determines that the detection object is It is judged that the reflected wave by is received.

In the present invention, the determination unit is configured such that the distance to the detection object previously obtained by the distance calculation unit and the distance to the detection object obtained this time are the same distance continuously for a predetermined number of times and the self-speed If is zero, it is determined that the detection object is stationary. The determination unit is configured such that the distance to the detection target previously obtained by the distance calculation unit and the distance to the detection target obtained this time are the same distance continuously for a predetermined number of times, and the own speed is zero. For example, it is preferable to determine that the detection object is moving at a speed equal to the self-speed.
In the present invention, the determination unit sets, as the change width, a minus-side change width and a plus-side change width with respect to the distance previously obtained by the distance calculation unit, and the minus-side change width. Is a value larger than the change width on the plus side. If the distance calculated by the distance calculation unit is within the range of the change width on the minus side or the change range on the plus side, the determination unit determines the distance obtained by the distance calculation unit last time and the current calculation. It is also preferable to determine that the difference from the measured distance is within the range of the change width.

  According to the present invention, since the determination unit uses the change width that changes in conjunction with its own speed as a determination criterion, even if the object detection device itself is moving, the received reflected wave is a reflected wave caused by the same detection object. It can be judged more accurately. The judgment unit detects whether the difference between the distance obtained by the distance calculation unit last time and the distance obtained this time is within the range of the change range for a predetermined number of times, thereby detecting false detection due to noise or the like. Reduce. By the determination operation of the determination unit, the object detection device can more accurately determine the distance to the detection target even if the object detection device itself is moving.

It is a schematic block diagram which shows the object detection apparatus of this embodiment. (A)-(d) is a conceptual diagram explaining the operation | movement which a judgment part judges whether the reflected wave by a detection target was received. 3 is a flowchart for explaining a determination operation of a determination unit 4;

  Hereinafter, embodiments of an object detection device according to the present invention will be described with reference to FIGS. The object detection device 1 of this embodiment is applied to an obstacle detection device that is attached to a vehicle such as an automobile, for example, detects an obstacle around the vehicle, and warns a person who operates the vehicle.

  The object detection device 1 of the present invention includes a transmission / reception unit 2, a distance calculation unit 3, a determination unit 4, and an output unit 5.

  The object detection device 1 measures the propagation time from the transmission of an ultrasonic pulse wave to the reception of a reflected wave, and obtains the propagation speed of the pulse wave and the distance from the propagation time to the object. In the description of this embodiment, an example in which an ultrasonic wave is used as a pulse wave will be described. However, the pulse wave is not limited to an ultrasonic wave. For example, a pulse wave is transmitted using a medium such as a radio wave or light, and reflected. You may receive waves.

  The transmission / reception unit 2 includes an ultrasonic transducer (not shown) for both transmission and reception and a control unit (not shown). The control unit periodically outputs a control signal to the ultrasonic transducer, and transmits a pulse wave T (ultrasonic wave) from the ultrasonic transducer. When the pulse wave T propagates through the space and is reflected by a surrounding object, the reflected wave R is received by the ultrasonic transducer. The transmitting means for the pulse wave T and the receiving means for the reflected wave R are not limited to the ultrasonic vibrator, and may be any appropriate means capable of transmitting and receiving ultrasonic waves. In addition, although the transmission / reception unit 2 includes one transmission / reception ultrasonic transducer, the transmission / reception unit 2 may include a transmission ultrasonic transducer and a reception ultrasonic transducer separately.

  The transmission / reception unit 2 outputs a transmission timing signal ST to the distance calculation unit 3 when transmitting the pulse wave T, and outputs a reception timing signal SR to the distance calculation unit 3 when receiving the reflected wave R.

  The distance calculation unit 3 is realized by, for example, a microcomputer executing a built-in program. When the distance calculation unit 3 receives the transmission timing signal ST, the distance calculation unit 3 starts counting clock signals with a certain period. When the distance calculation unit 3 receives the reception timing signal SR, the distance calculation unit 3 finishes counting the clock signal, and obtains the propagation time TW of the pulse wave T from the number of counts during that time. The method for obtaining the propagation time TW is not limited to the method by counting the number of clocks, and may be an appropriate method for obtaining the time difference.

  When the distance calculation unit 3 calculates the distance d to the object based on the propagation time TW, the distance calculation unit 3 outputs the measurement result of the distance d to the determination unit 4. The distance d can be obtained from the propagation speed of the pulse wave T and the propagation time TW. For example, in dry air with a temperature of 0 degrees in the standard state, the propagation speed of the ultrasonic wave is about 331 m / s. If the state of the ultrasonic medium (temperature, density, pressure, etc.) is constant, the propagation of the ultrasonic wave The speed can be considered constant. Therefore, for example, the distance d from the object detection device 1 to the object can be obtained by dividing the distance obtained by the product of the propagation time TW and the ultrasonic propagation velocity by 2. The method for obtaining the distance d is not limited to the method for obtaining the distance d by calculating the propagation time TW and the ultrasonic wave propagation velocity, and may be obtained by an appropriate method. For example, a comparison table of the propagation time TW and the distance d may be set in the distance calculation unit 3 in advance, and the distance calculation unit 3 may obtain the distance d by referring to the comparison table from the measured propagation time TW.

  The vehicle to which the object detection device 1 is attached is provided with a vehicle speed sensor (not shown) that measures the speed of the vehicle.

  The determination unit 4 is realized by, for example, a microcomputer executing a built-in program, and holds a determination count value in a memory or the like, for example. The determination unit 4 determines whether or not the distance obtained by the distance calculation unit 3 is a distance to the same object, that is, whether or not noise or the like is erroneously detected.

When there is a stationary object around the stationary object detection device 1, the distance to the previously obtained object and the distance to the currently obtained object are substantially the same. On the other hand, when the object detection device 1 is moving at a certain speed, the distance to the object obtained last time and the distance to the object obtained this time change by a distance corresponding to the own speed, so that the pulse wave T The propagation time TW also changes according to the own speed. Therefore, the determination unit 4 sets an allowable change width AD of the distance to the target according to the own speed, and the distance dp to the target obtained by the distance calculation unit 3 last time and the distance to the target determined this time. If the difference from d falls within the range of the change width AD continuously for a predetermined number of times, it is determined that the distance to the same object. The determination unit 4 sets the change width AD so as to be proportional to the measured value Vs of the own speed taken from the speed sensor, for example. For example, the change width AD is obtained by adding the change width AD0 when the own speed Vs is 0 and a value obtained by multiplying the own speed Vs by a predetermined coefficient. The change width AD0 is set to an allowable error range between the distance to the object obtained last time and the distance to the object obtained this time when the object is stationary with the own speed Vs being 0. Has been. Note that the method of obtaining the change width AD is not limited to the method in which the determination unit 4 obtains the change width AD by calculation, and the change width AD may be obtained by an appropriate method. For example, a comparison table of the own speed Vs and the change width AD may be set in the determination unit 4 in advance, and the determination unit 4 may obtain the change width AD by referring to the comparison table from the own speed Vs. The distance calculation unit 3 and the determination unit 4 are not limited to being realized by separate microcomputers, and may be realized by a single microcomputer.

  Next, the determination operation of the determination unit 4 will be described with reference to FIGS. The determination unit 4 sets the determination count value to 0 when the object detection device 1 is activated, and resets the distance dp (step S1 in FIG. 3).

  When an object enters the detection range of the object detection device 1, as shown in FIG. 2A, the transmission / reception unit 2 receives the reflected wave R1 with respect to the transmitted pulse wave T1, and the distance calculation unit 3 receives the target. The distance d (d1) to the object is obtained and output to the determination unit 4. When the distance d to the object is input in a state where the distance dp is reset (step S2), the determination unit 4 temporarily stores the input distance d as the distance dp in the memory (step S3).

  Thereafter, as shown in FIG. 2 (b), when the transmission / reception unit 2 continuously detects the reflected wave R2 for the pulse wave T2 following the reflected wave R1, the distance calculation unit 3 detects the distance d (d2) to the object. Is output to the determination unit 4 (step S4). When the distance d is input from the distance calculation unit 3, the determination unit 4 takes in the own speed Vs from the vehicle speed sensor and sets the change width AD.

  As shown in FIG. 2B, when the distance d is out of the range of the change width AD due to the influence of the noise N or the like, that is, when (d1−AD) ≦ d2 ≦ (d1 + AD) is not satisfied (No in step S5). The determination unit 4 determines that they are not reflected waves from the same object. Then, the determination unit 4 sets the determination count value to 0, resets the distance dp (step S10), and returns to the process of step S2. In other words, when the difference between the distance dp obtained by the distance calculation unit 3 last time and the distance d obtained this time is out of the range of the change width AD, that is, (−AD) ≦ (d−dp) ≦ AD is not satisfied. At this time, the determination unit 4 sets the determination count value to 0 and resets the distance dp.

  On the other hand, when the distance d obtained by the distance calculation unit 3 is within the range of the change width AD centered on the distance dp (= d1) obtained last time, that is, (d1−AD) ≦ d2 ≦ (d1 + AD). When satisfy | filling (Yes of step S5), the judgment part 4 judges that it is a reflected wave by a detection target object. Then, the determination unit 4 increments the determination count value by one (step S6). In other words, when the difference between the distance dp obtained by the distance calculation unit 3 last time and the distance d obtained this time is within the range of the change width AD, that is, (−AD) ≦ (d−dp) ≦ AD. When satisfied, the determination unit 4 increments the determination count value by one. The determination unit 4 temporarily stores the distance d obtained this time in the memory as the distance dp (step S7).

  Next, the determination unit 4 compares the determination count value with a predetermined number of times C. If the determination count value is smaller than the predetermined number of times C (No in step S8), the determination unit 4 returns to the process of step S4 and repeats the above process when the measured value of the distance d is input from the distance calculation unit 3. . If the determination count value is equal to or greater than the predetermined number of times C (Yes in step S8), the determination unit 4 determines that the detection target exists at the distance obtained by the distance calculation unit 3 at this time, and sends the distance d to the output unit 5. Is output (step S9).

  When the distance d is input from the determination unit 4, the output unit 5 outputs the distance d to an external device (not shown). The external device is constituted by a display unit (not shown), for example.

  The determination unit 4 is not limited to setting the change width AD every time the distance calculation unit 3 outputs the distance d, but sets the change width AD at an appropriate timing that can respond to the change in the own speed Vs. May be. For example, until the difference between the previous self-speed Vs and the current self-speed Vs exceeds a predetermined range, the self-speed Vs is considered to be constant, and the determination unit 4 does not set the change width AD and The change width AD may be used for the above determination as it is.

  As described above, the object detection device 1 of the present invention includes the transmission / reception unit 2, the distance calculation unit 3, the determination unit 4, and the output unit 5. The transmission / reception unit 2 periodically transmits a pulse wave T propagating in space and receives a reflected wave R reflected by a detection target. The distance calculation unit 3 obtains the distance d to the detection target based on the propagation time TW from when the transmission / reception unit 2 transmits the pulse wave T to when the reflected wave R is received. The determination unit 4 sets the change width AD of the distance to the detection target in conjunction with the own speed Vs of the object detection device 1. If the difference between the distance dp previously obtained by the distance calculation unit 3 and the distance d obtained this time is within the range of the change width AD for a predetermined number of times, the determination unit 4 determines that the transmission / reception unit 2 has the same detection. It is determined that the reflected wave R from the object has been received, and the distance d obtained this time is output from the output unit 5.

  Thereby, since the determination part 4 uses the change width AD which changes in conjunction with the own speed Vs as a determination reference, even if the object detection apparatus 1 itself moves, the received reflected wave R is based on the same detection object. It is possible to more accurately determine whether the wave is a reflected wave. The determination unit 4 determines whether or not the difference between the distance dp obtained by the distance calculation unit 3 last time and the distance d obtained this time is within the range of the change width AD continuously for a predetermined number of times. Reduce false detection by By the determination operation of the determination unit 4, the object detection device 1 can more accurately determine the distance to the detection target even if the object detection device 1 itself is moving. For example, when the vehicle to which the vehicle speed sensor is attached is accelerating, as shown in FIG. 2D, the determination unit 4 detects by setting the change width AD larger according to the self-speed Vs that becomes larger. The distance d obtained from the reflected wave from the object is not easily deviated from the range of the change width AD. Therefore, the false detection that the detection target object does not exist is reduced.

  In the present embodiment, the determination unit 4 may additionally perform the following processing. If the distance dp to the previous detection object and the distance d to the current detection object are equal distances a predetermined number of times and the own speed Vs is 0, the determination unit 4 determines the detection object. Is determined to be stationary. If the distance dp and the distance d are equidistant continuously for a predetermined number of times and the own speed Vs is not 0, the determination unit 4 determines that the detection target is moving at a speed equal to the own speed Vs. .

  Thereby, when the distance from the object detection device 1 to the detection target has not changed, the object detection device 1 determines whether the detection target is stationary or moving at a speed equal to the own speed Vs. Can be output.

  In the present embodiment, the object detection device 1 detects the distance to the detection target when the difference between the distance dp and the distance d is within the range of the change width AD even if the detection target is moving. It is possible. For example, the object detection device 1 detects a detection target that moves so as to approach or separate from the object detection device 1 at a speed such that the difference between the distance dp and the distance d is within the range of the change width AD. Can do.

  Further, by adding to the determination unit 4 a determination operation as to whether or not the distance d to the detection target to be output to the output unit 5 is small, the determination unit 4 can detect only the detection target approaching the object detection device 1. Can be detected. When the determination unit 4 determines that the object to be detected is approaching the object detection device 1, for example, by outputting a warning signal and a distance d from the output unit 5, the vehicle on which the object detection device 1 is mounted is provided. The fact that there is an approaching detection object can be output to the display unit or the like.

  In the determination by the determination unit 4 in the present embodiment (step S5), (−AD) ≦ (d−dp) ≦ AD is used, but the minimum value and the maximum value of this inequality need not be the same value. For example, when the object detection device 1 is installed in a bumper or the like of a vehicle and the object detection device 1 detects a distance to a detection target around the vehicle, the detection target is detected with respect to the object detection device 1. The risk is higher when approaching than when moving away. Therefore, the negative change width AD2 is set to a larger value than the positive change width AD1 (AD1 <AD2), and the determination unit 4 determines (−AD2) ≦ (d−dp) ≦ AD1 in step S5. It may be. Accordingly, the determination unit 4 can reduce detection omissions more for a detection target approaching the object detection device 1 than for a detection target moving away from the object detection device 1.

DESCRIPTION OF SYMBOLS 1 Object detection apparatus 2 Transmission / reception part 3 Distance calculation part 4 Judgment part 5 Output part T Pulse wave R Reflected wave Vs Self-speed

Claims (3)

An object detection device that outputs a distance to a detection object,
A transceiver for receiving a reflected wave reflected by the object to be detected transmits a pulse wave propagating through space periodically,
A distance calculation unit for obtaining a distance to the detection object based on a propagation time from when the transmission / reception unit transmits the pulse wave to reception of the reflected wave;
A determination unit that determines whether the reflected wave received by the transmission / reception unit is a reflected wave by the detection object;
When the determination unit determines that the transmission / reception unit has received a reflected wave from the detection object, an output unit that outputs the distance obtained by the distance calculation unit;
With
The determination unit uses the speed of change of the distance to the detection target due to the movement of the object detection device as the allowable change width of the distance obtained by the distance calculation unit , and the self-speed of the object detection device. Set in conjunction with
If the difference between the distance obtained by the distance calculation unit last time and the distance obtained this time is within the range of the change width for a predetermined number of times, the transmission / reception unit determines that the detection object is It is judged that the reflected wave by received is received, The object detection apparatus characterized by the above-mentioned. The determination unit is configured such that the distance to the detection target previously obtained by the distance calculation unit and the distance to the detection target obtained this time are the same distance continuously a predetermined number of times, and the own speed is 0. If so, the detection object is determined to be stationary,
The determination unit is configured such that the distance to the detection target previously obtained by the distance calculation unit and the distance to the detection target obtained this time are the same distance continuously a predetermined number of times, and the own speed is 0. Otherwise, it is determined that the object to be detected is moving at a speed equal to the self-speed.   The determination unit sets, as the change width, a minus-side change width and a plus-side change width with respect to the distance previously obtained by the distance calculation unit, and the minus-side change width is set to the plus side. If the distance calculated by the distance calculation unit is within the range of the change width on the minus side or the change range on the plus side, the distance calculation unit previously obtained The object detection apparatus according to claim 1, wherein a difference between the distance and the distance obtained this time is determined to be within the range of the change width.

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