JP5807197B2 - Object detection device - Google Patents

Description

  The present invention relates to an object detection apparatus that detects the presence of an object and obtains a distance to the object.

  Conventionally, a vehicle proximity alarm device using ultrasonic waves is known, and is disclosed in, for example, Patent Document 1. The conventional example described in Patent Document 1 includes an oscillating unit that oscillates an ultrasonic frequency signal, a transmitting unit that converts the signal from the oscillating unit into an ultrasonic wave, and an output, and converts the received ultrasonic wave into an electrical signal. Receiving means. In addition, this conventional example measures the reflected wave detecting means for detecting the reflected wave by the signal from the receiving means, the distance from the time until the reflected wave is detected to the obstacle, and within a preset time. Control means for changing the measurement range if no reflected wave is detected.

  The control means periodically checks the signal from the reflected wave detection means, and switches the measurement range when no detection signal is received within the measurement time corresponding to the measurement range. On the other hand, if the control means receives a detection signal within the measurement time, if the detection time is longer than the time when the influence of the direct wave directly input from the transmission means disappears, it is considered as a reflected wave, and the distance to the obstacle Calculate Therefore, in this conventional example, if the oscillation time of the oscillating means is increased so that an obstacle far away can be detected, the disadvantage that the reflected wave from the obstacle at a short distance overlaps with the direct wave and cannot be detected is improved.

JP-A-6-76199

  However, in the above conventional example, when the signal from the oscillating means is converted by the transmitting means (ultrasonic vibrator) and the ultrasonic wave is transmitted, the ultrasonic vibrator will not stop after the signal from the oscillating means stops. Transmits ultrasonic waves caused by reverberation vibration. Since the ultrasonic waves generated by the reverberation vibration are received by the reception means (ultrasonic transducer), the reflected wave is buried in the reverberation vibration when the reflected wave from the object is detected and the distance to the object is very close. If this happens, the object cannot be detected. This problem can also occur in the case where ultrasonic waves are transmitted and received by one ultrasonic transducer.

  Here, in order to avoid the reflected wave from the object being buried in the reverberation vibration, it may be possible to use a high-performance ultrasonic transducer with a small reverberation vibration itself, but in this case, the cost increases. was there.

  The present invention has been made in view of the above points, and an object of the present invention is to provide an object detection apparatus that can detect an object existing at a very short distance without increasing costs.

An object detection device of the present invention includes a transmission / reception unit that transmits / receives an ultrasonic wave, and a control unit that detects the object based on time required to receive a reflected wave from the object. If the reflected wave is not received at the time when half the time required for receiving the first reflected wave has elapsed after receiving the first reflected wave, multiple reflections occur due to the first reflected wave. If the second reflected wave is received, it is determined that the object is present at a position closer to the position detected by the first reflected wave.

  In this object detection apparatus, the transmission / reception unit includes a plurality of ultrasonic transducers provided at regular intervals, and an ultrasonic wave transmitted by one of the adjacent ultrasonic transducers is transmitted. Is received by the other ultrasonic transducer, and the control unit detects the object based on a transmission timing of the one ultrasonic transducer and a reception timing of the other ultrasonic transducer. Is preferred.

  The present invention has an effect of being able to detect an object existing at a very short distance without increasing costs.

BRIEF DESCRIPTION OF THE DRAWINGS It is a figure which shows Embodiment 1 of the object detection apparatus based on this invention, (a) is a block diagram, (b), (c) is a wave form diagram for demonstrating operation | movement. It is a wave form diagram for demonstrating the operation | movement in Embodiment 2 of the object detection apparatus which concerns on this invention. It is a wave form diagram for demonstrating the operation | movement in Embodiment 3 of the object detection apparatus which concerns on this invention. It is the schematic which shows Embodiment 4 of the object detection apparatus which concerns on this invention.

(Embodiment 1)
Hereinafter, Embodiment 1 of an object detection device according to the present invention will be described with reference to the drawings. In the present embodiment, as shown in FIG. 1A, an ultrasonic transducer 1 (transmission / reception unit) that transmits / receives ultrasonic waves and an ultrasonic transducer 1 that drives the ultrasonic transducer 1 to generate ultrasonic waves And a processing unit 3 for processing a reflected wave from the object A1 received by the ultrasonic transducer 1. Moreover, this embodiment is provided with the control part 4 which detects the object A1 from the process result of the process part 3 while controlling the drive part 2. FIG.

  This embodiment is mounted on a vehicle (not shown), for example, to detect an obstacle (object A1) around the vehicle and determine the distance to the obstacle. When the present embodiment is mounted on a vehicle, the ultrasonic transducer 1 is embedded in a vehicle bumper, and other members are disposed in the vehicle interior.

  The ultrasonic transducer 1 vibrates when an oscillation signal is input from the drive unit 2 and transmits ultrasonic waves having the frequency of the oscillation signal to the external space. Further, the ultrasonic transducer 1 receives a reflected wave from the object A1 existing in the external space and vibrates, thereby converting the received wave into a received signal based on the frequency of the reflected wave and outputting it to the processing unit 3. .

  The drive unit 2 includes an oscillator (not shown) that oscillates an oscillation signal having a predetermined frequency, and a switch (not shown) that switches the connection between the oscillator and the ultrasonic transducer 1. The switch is turned on / off by a control signal supplied from the control unit 4. Therefore, the drive unit 2 inputs an oscillation signal to the ultrasonic transducer 1 based on the control signal given from the control unit 4, and transmits ultrasonic waves from the ultrasonic transducer 1 at a predetermined interval.

  The processing unit 3 includes a low-pass filter (LPF) 30, an amplifier circuit 31, an envelope detection circuit 32, a comparator 33, and a gate circuit 34. The low pass filter 30 removes noise included in the received signal output from the ultrasonic transducer 1. The amplifier circuit 31 amplifies the received signal that has passed through the low-pass filter 30 to a predetermined level. The envelope detection circuit 32 performs envelope detection on the received signal amplified by the amplifier circuit 31. The comparator 33 compares the level of the signal output from the envelope detection circuit 32 with a predetermined level, and outputs a high-level detection signal when the level of the signal exceeds the predetermined level.

  The gate circuit 34 passes only the detection signal input within a predetermined period of the detection signal output from the comparator 33. Specifically, the gate circuit 34 calculates a logical product of the detection signal output from the comparator 33 and the gate signal provided from the control unit 4. In the gate circuit 34, the logical product of the detection signal and the gate signal is 1 only for a predetermined period when the gate signal is at a high level, and the detection signal is input to the control unit 4.

  The control unit 4 is composed of, for example, a microcomputer, and transmits ultrasonic waves at a predetermined interval from the ultrasonic transducer 1 by giving the drive unit 2 a pulse-like control signal for switching on / off of the switch as described above. Let At this time, the control unit 4 stores the timing at which the control signal is given to the driving unit 2 as the transmission timing of the ultrasonic transducer 1. In addition, the control unit 4 passes only a detection signal within a predetermined period of the detection signal output from the comparator 33 by applying a pulsed gate signal to the gate circuit 34 as described above.

  Here, since the ultrasonic transducer 1 has a high Q value, the vibration cannot be stopped immediately even when the driving by the driving unit 2 is stopped, and the vibration gradually attenuates. This is the reverberation vibration of the ultrasonic vibrator 1, and this reverberation vibration lasts for a certain period of time. Therefore, the reverberation vibration may be erroneously detected as a reflected wave from the object A1. Therefore, as shown in FIG. 1B, the control unit 4 determines that the detection signal is a gate circuit during a period from time T0 when the ultrasonic wave is transmitted to time T1 when the output value of the detection signal falls below a predetermined threshold. The mask period G 0 is set so as not to pass through 34. That is, in the mask period G0, since the gate signal is at a low level, the logical product with the detection signal output from the comparator 33 is always 0, and the detection signal is not input to the control unit 4.

  Further, as shown in FIG. 1B, the control unit 4 sets a period from time T1 to time T2 as a first gate period G1, and a period after time T2 as a second gate period G2. . These gate periods G1 and G2 correspond to the above-mentioned predetermined period. Since the gate signal is at a high level in each of the gate periods G1 and G2, the logical product with the detection signal output from the comparator 33 becomes 1, and control is performed. A detection signal is input to the unit 4.

  The control unit 4 stores the timing at which the high-level detection signal from the processing unit 3 (comparator 33) is input as the ultrasonic wave reception timing. And the control part 4 calculates | requires the propagation time required for the transmission / reception of an ultrasonic wave from the transmission timing already memorize | stored and the reception timing acquired from the process part 3, and to object A1 based on this propagation time Calculate the distance. This calculation result is given to a device such as a buzzer. When given to the buzzer, it is conceivable that a warning sound is generated when the distance to the object A1 becomes a predetermined threshold value or less. A configuration in which the calculation result is displayed on the display and the driver is notified of the distance to the object A1 is also conceivable.

  In the present embodiment, when a detection signal is input to the control unit 4 before time T2, that is, in the first gate period G1, the control unit 4 determines that the object A1 exists at a short distance, and the buzzer described above. A warning sound is sounded to inform the outside. Note that when the detection signal is input to the control unit 4 after the time T2, that is, in the second gate period G2, the control unit 4 determines that the object A1 exists at a long distance.

  Hereinafter, detection of the object A1 existing at a very short distance in the present embodiment will be described. Note that “very close distance” means “a distance that the object A1 is approaching so that the reflected wave is buried in the reverberation vibration of the ultrasonic transducer 1”. First, as shown in FIG. 1B, ultrasonic waves are transmitted from the ultrasonic transducer 1 at time T0, and reflected from the object A1 between time T1 and time T2, that is, in the first gate period G1. Assume that a wave has been received. Here, when the object A1 is located near the ultrasonic transducer 1, multiple reflections are repeated between the object A1 and the ultrasonic transducer 1 as shown in FIG. Happens. Therefore, as shown in FIG. 1B, the ultrasonic transducer 1 receives a reflected wave due to multiple reflection after time T2, that is, in the second gate period. In the following description, the first reflected wave from the object A1 is referred to as “first reflected wave W1,” and the second reflected wave from the object A1 due to multiple reflection is referred to as “second reflected wave W2.” And

  In the case shown in FIG. 1B, the time required to receive the first reflected wave W1 from the time T0 when the ultrasonic wave is transmitted, and the second time after receiving the first reflected wave W1. The time required to receive the reflected wave W2 is equal. Therefore, in this case, the control unit 4 determines that the reflected wave from the object A1 is not buried in the reverberation vibration of the ultrasonic transducer 1. In addition, since the first reflected wave W1 is received in the first gate period G1, the control unit 4 determines that the object A1 exists at a short distance, and notifies the outside using a buzzer or the like. .

  Next, FIG. 1 (c) shows a case where the object A1 further approaches after a lapse of time since the ultrasonic wave is transmitted at time T0, and the ultrasonic wave is transmitted again from the ultrasonic transducer 1 at time T3. Show. In the figure, the period from time T3 to time T4 is equal to the period from time T0 to time T1, and the period from time T4 to time T5 is equal to the period from time T1 to time T2. . That is, in the figure, the period from time T3 to time T4 is the mask period G0, the period from time T4 to time T5 is the first gate period G1, and the period after time T5 is the second gate period G2. .

  In this case, the ultrasonic transducer 1 does not receive the ultrasonic wave in the first gate period G1, and receives the first reflected wave W1 in the second gate period G2. Here, if the first reflected wave W1 is simply received, it cannot be determined whether the first reflected wave W1 is the first reflected wave from the object A1 or a reflected wave due to multiple reflection. If it exists at a long distance, the control unit 4 may erroneously determine.

  Therefore, in the present embodiment, when the state in which the reflected wave is received in both the gate periods G1 and G2 shifts to the state in which the reflected wave is received only in the second gate period G2, the control unit 4 It is determined that the reflected wave W0 from the object A1 is buried in one reverberation vibration. Thereby, the control unit 4 can determine that the object A1 exists at a position closer to the position detected in the first gate period G1, that is, the closest distance, and can continue the notification.

  As described above, in the present embodiment, the control unit 4 can determine that there is a reflected wave buried in the reverberation vibration of the ultrasonic transducer 1 and can detect the object A1 existing at a very short distance. . Therefore, in the present embodiment, it is not necessary to use the high-performance ultrasonic transducer 1, and it is possible to use the ultrasonic transducer 1 having a long reverberation vibration, so that an increase in cost can be suppressed.

(Embodiment 2)
Hereinafter, Embodiment 2 of the object detection device according to the present invention will be described with reference to the drawings. However, since the circuit configuration of the present embodiment is the same as the circuit configuration shown in FIG. 1A of the first embodiment, common portions are denoted by the same reference numerals and description thereof is omitted. First, as shown in FIG. 2, it is assumed that the ultrasonic transducer 1 has received a first reflected wave W1, which is the first reflected wave. Here, simply receiving the first reflected wave W1 cannot determine whether the first reflected wave W1 is the first reflected wave from the object A1 or a reflected wave due to multiple reflection. In addition, as shown in FIG. 2, even if the second reflected wave W2 due to multiple reflection is received, the reflected wave from another object (not shown) different from the object A1 is received almost simultaneously. If the reflected waves overlap, the second reflected wave W2 cannot be distinguished from other reflected waves.

  Therefore, the control unit 4 according to the present embodiment calculates the propagation time τ1 required for transmitting and receiving the ultrasonic wave when the first reflected wave W1, that is, the first reflected wave is received. And the control part 4 determines the presence or absence of the detection signal from the process part 3 when the time ((tau) 1/2) of the said propagation time (tau) 1 passed after receiving the 1st reflected wave. Then, it is determined whether or not there is a reflected wave at that time.

  If it is determined that the reflected wave is not received at the time point, the control unit 4 determines that multiple reflection due to the first reflected wave W1 has not occurred, and the object A1 based on the first reflected wave W1. The position of is detected. On the other hand, when it is determined that the reflected wave is received at the time point, the control unit 4 determines that the reflected wave is the second reflected wave W2 due to the multiple reflection of the first reflected wave W1. Then, the control unit 4 has a reflected wave at a time that is half the propagation time τ1 behind the first reflected wave W1, that is, the reverberation vibration of the ultrasonic vibrator 1 from the object A1. It is determined that the reflected wave W0 is buried. Thereby, the control part 4 can determine with the object A1 existing in the position nearer than the position detected with the 1st reflected wave W1, ie, the very near distance.

  As described above, in the present embodiment, the control unit 4 can determine that there is a reflected wave buried in the reverberation vibration of the ultrasonic transducer 1 and can detect the object A1 existing at a very short distance. . Therefore, in the present embodiment, it is not necessary to use the high-performance ultrasonic transducer 1, and it is possible to use the ultrasonic transducer 1 having a long reverberation vibration, so that an increase in cost can be suppressed.

(Embodiment 3)
Hereinafter, Embodiment 3 of the object detection device according to the present invention will be described with reference to the drawings. However, since the circuit configuration of the present embodiment is the same as the circuit configuration shown in FIG. 1A of the first embodiment, common portions are denoted by the same reference numerals and description thereof is omitted. First, as shown in FIG. 3, it is assumed that the ultrasonic transducer 1 receives three reflected waves W1 to W3. Here, simply receiving the three reflected waves W1 to W3 cannot determine whether the first reflected wave W1 is the first reflected wave from the object A1 or the reflected wave due to multiple reflection.

  Therefore, the control unit 4 of the present embodiment receives the time P1 required from the time when the first reflected wave W1 is received until the time when the second reflected wave W2 is received, and the second reflected wave W2. And the time P2 required from the time of receiving to the time of receiving the third reflected wave W3. Then, the control unit 4 compares the times P1 and P2, and if these times P1 and P2 are equal, the reflected wave exists at a time that is earlier than the first reflected wave W1 by the time P1, that is, It is determined that the reflected wave W0 from the object A1 is buried in the reverberation vibration of the acoustic wave vibrator 1. Thereby, the control part 4 can determine with the object A1 existing in the position nearer than the position detected with the 1st reflected wave W1, ie, the very near distance.

  As described above, in the present embodiment, the control unit 4 can determine that there is a reflected wave buried in the reverberation vibration of the ultrasonic transducer 1 and can detect the object A1 existing at a very short distance. . Therefore, in the present embodiment, it is not necessary to use the high-performance ultrasonic transducer 1, and it is possible to use the ultrasonic transducer 1 having a long reverberation vibration, so that an increase in cost can be suppressed.

(Embodiment 4)
Hereinafter, Embodiment 4 of the object detection apparatus according to the present invention will be described with reference to the drawings. However, since the circuit configuration of the present embodiment is the same as the circuit configuration shown in FIG. 1A of the first embodiment, common portions are denoted by the same reference numerals and description thereof is omitted. In the present embodiment, as shown in FIG. 4, a wave transmitting / receiving unit is configured by a plurality (four in the figure) of ultrasonic transducers 10 to 13, and each ultrasonic transducer 10 to 13 is connected to the vehicle B <b> 1. It is arranged at a certain distance D1 at the front part or the rear part. In this embodiment, each ultrasonic transducer | vibrator 10-13 shall be arrange | positioned at the bumper (not shown) of the front part of vehicle B1.

  Here, when the object A1 exists in the space C1 in front of each of the ultrasonic transducers 10 to 13, the object A1 exists at a very close distance of the vehicle B1 by adopting any of the above embodiments. Can be detected. On the other hand, as shown in FIG. 4, when the object A1 exists in the space C2 between the adjacent ultrasonic transducers 10 to 13, the following problem occurs.

  For example, when the object A1 is detected by the ultrasonic transducer 10, since the object A1 is located at a position away from the space C1, the reflected wave from the object A1 is received in the second gate period G2, The control unit 4 determines that the object A1 exists at a long distance. However, the object A1 exists at a long distance when viewed from the ultrasonic transducer 10, but exists at a very short distance when viewed from the vehicle B1. For this reason, with only one ultrasonic transducer 10, the control unit 4 cannot determine that the object A1 existing in the space C2 exists at a very close distance of the vehicle B1.

  In the present embodiment, the control unit determines that the object A1 existing in the space C2 exists at a very close distance of the vehicle B1 by transmitting and receiving ultrasonic waves between two adjacent ultrasonic transducers 10 to 13. It is characterized in that the determination can be made at 4.

  Hereinafter, detection of the object A1 existing at a very short distance of the vehicle B1 in the present embodiment will be described. In the following description, the ultrasonic transducer 10 is “first ultrasonic transducer 10”, the ultrasonic transducer 11 is “second ultrasonic transducer 11”, and the ultrasonic transducer 12 is “third”. The ultrasonic transducer 12 ”and the ultrasonic transducer 13 are referred to as“ fourth ultrasonic transducer 13 ”. Further, each of the ultrasonic transducers 10 to 13 is individually provided with a drive unit 2 and a processing unit 3, and exchange of signals with each of the drive units 2 and each processing unit 3 is performed by one control unit 4. And

  First, the control unit 4 detects the presence or absence of the object A1 in the space C1 in front of the first ultrasonic transducer 10 by causing the first ultrasonic transducer 10 to transmit and receive ultrasonic waves. . As this detection method, any one of Embodiments 1 to 3 may be adopted.

  Next, the control unit 4 transmits ultrasonic waves from the first ultrasonic transducer 10 and stores the transmission timing. Thereafter, the ultrasonic wave transmitted from the first ultrasonic transducer 10 is reflected by the object A1, and the reflected wave is received by the second ultrasonic transducer 11 adjacent to the first ultrasonic transducer 10. Then, the control unit 4 stores this reception timing. And the control part 4 calculates | requires the propagation time required for the transmission / reception of an ultrasonic wave from the transmission timing of the 1st ultrasonic transducer | vibrator 10 and the reception timing of the 2nd ultrasonic transducer | vibrator 11. FIG. The control unit 4 calculates the sum of the distance between the object A1 and the first ultrasonic transducer 10 and the distance between the object A1 and the second ultrasonic transducer 11 from the propagation time.

  Here, if the sum of the distances between the ultrasonic transducers 10 and 11 and the object A1 is constant, the object A1 focuses on the first ultrasonic transducer 10 and the second ultrasonic transducer 11. It will be located on the ellipse. For this reason, the distance between the object A1 and the bumper of the vehicle B1 can be estimated by determining the circumference of the ellipse where the object A1 is located. Therefore, the control unit 4 compares the sum of the distances between the ultrasonic transducers 10 and 11 and the object A1 with a predetermined threshold, and if the sum of the distances falls below the predetermined threshold, the adjacent ultrasonic waves It can be determined that the object A1 exists at a very short distance in the space C2 between the vibrators 10 and 11. When the control unit 4 determines that the object A1 exists at a very short distance, the control unit 4 notifies the outside using a buzzer or the like.

  Thereafter, the control unit 4 sequentially ultrasonicates the second ultrasonic transducer 11, the adjacent second ultrasonic transducer 11, the third ultrasonic transducer 12, and the third ultrasonic transducer 12. Let's send and receive. Therefore, in the present embodiment, not only the space C1 in front of each of the ultrasonic transducers 10 to 13 but also the object A1 that is present at a close distance in the space C2 between the adjacent ultrasonic transducers 10 to 13 is detected. can do.

  By the way, when ultrasonic waves are transmitted and received between adjacent ultrasonic transducers 10 to 13, the propagation time of the ultrasonic waves becomes longer than the mask period G0 of the ultrasonic transducers 10 to 13 on the reception side. For this reason, since the ultrasonic transducers 10 to 13 on the receiving side receive the reflected wave from the object A1 after the mask period G0, they are present at a very short distance without being affected by the reverberation vibration. The object A1 can be detected.

  In the present embodiment, signals are exchanged with the drive units 2 and the processing units 3 of all the ultrasonic transducers 10 to 13 by the single control unit 4, but the ultrasonic transducers 10 to 13 are used. You may provide the control part 4 for every.

1 Ultrasonic transducer (wave transmitter / receiver)
4 Control Unit A1 Object G1 First Gate Period G2 Second Gate Period

Claims (2)

A transmission / reception unit for transmitting / receiving ultrasonic waves, and a control unit for detecting the object based on time required for reception of the reflected wave from the object, wherein the control unit receives the first reflected wave If a reflected wave is not received at the time when half of the time required for receiving the wave has elapsed, it is determined that multiple reflection due to the first reflected wave has not occurred, and two When receiving a reflected wave of an eye, it is determined that the object is present at a position closer to a position detected by the first reflected wave . The transmission / reception unit includes a plurality of ultrasonic transducers provided at regular intervals, and transmits ultrasonic waves transmitted from one ultrasonic transducer among the adjacent ultrasonic transducers to the other ultrasonic oscillation. claim child and reception, the control unit, characterized in that for detecting the object based the the transmission timing of one of the ultrasonic vibrator and reception timing of the other ultrasonic transducers The object detection device according to 1 .

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