Object detection device, object detection method and control device

Abstract

The detection waves of each ultrasonic sensor in the plurality of ultrasonic sensors (2) have different characteristics that can be identified from each other. A transmission timing setting unit (31) sets the transmission timing of the detection waves of each ultrasonic sensor in the plurality of ultrasonic sensors so that each ultrasonic sensor in the plurality of ultrasonic sensors transmits the detection waves at different transmission timings. The transmission timing setting unit sets a delay time determined based on the positional relationship between the first ultrasonic sensor and the second ultrasonic sensor between a first transmission timing (Tt1) of the transmission timing of the first ultrasonic sensor and a second transmission timing (Tt2) of the transmission timing of the second ultrasonic sensor when one of the plurality of ultrasonic sensors is set as a first ultrasonic sensor and another one of the plurality of ultrasonic sensors is set as a second ultrasonic sensor.

Description

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS

[0002] This application is based on Japanese Patent Application No. 2019-118736 filed on June 26, 2019, the contents of which are incorporated herein by reference. Technical Field

[0003] The present invention relates to an object detection device and an object detection method. In addition, the present invention relates to a device for controlling the operation of each of a plurality of ultrasonic sensors. Background Art

[0004] The obstacle detection device disclosed in Patent Document 1 includes a control device and a plurality of ultrasonic sensors. The control device uses a plurality of ultrasonic sensors to simultaneously transmit and receive ultrasonic waves to detect the position of an obstacle. Specifically, the control device sequentially switches two or more specific ultrasonic sensors that have detected an obstacle to transmit, and uses all ultrasonic sensors to receive. Furthermore, the control device continues to detect the obstacle until the obstacle cannot be detected in the detection area of ​​the specific ultrasonic sensor that has detected the obstacle. Thus, the responsiveness to obstacles approaching at high speed can be improved.

[0005] Patent Document 1: International Publication No. 2010 / 146619

[0006] As in the obstacle detection device disclosed in Patent Document 1, by using a plurality of ultrasonic sensors to transmit and receive ultrasonic waves simultaneously, the detection cycle of the entire device can be shortened to speed up the detection. However, in the obstacle detection device disclosed in Patent Document 1, it takes time until two or more ultrasonic sensors that detect an obstacle are identified. In addition, when the ultrasonic sensor that transmits is limited to a specific ultrasonic sensor among the plurality of ultrasonic sensors, the detectable range is limited. Summary of the invention

[0007] The present invention has been made in view of the above-mentioned exemplified circumstances, etc. Specifically, the present invention provides a structure and method that can satisfactorily realize high-speed detection by shortening the detection cycle in object detection using a plurality of ultrasonic sensors, for example.

[0008] According to one aspect of the present invention, an object detection device comprises:

[0009] a plurality of ultrasonic sensors, each of which detects the object by transmitting a detection wave as an ultrasonic wave and receiving a reflection wave of the detection wave from a surrounding object; and

[0010] a control unit for controlling the operation of each of the plurality of ultrasonic sensors;

[0011] The plurality of ultrasonic sensors are arranged so that the detection waves of the respective ultrasonic sensors have different characteristics that can be identified from each other.

[0012] The control unit has:

[0013] a transmission timing setting unit that sets a transmission timing of the detection wave of each of the plurality of ultrasonic sensors; and

[0014] a transmission instruction unit for instructing each of the plurality of ultrasonic sensors to start transmission of the detection wave based on the transmission timing set by the transmission timing setting unit;

[0015] The transmission timing setting unit sets a delay time determined based on a positional relationship between the first ultrasonic sensor and the second ultrasonic sensor between the transmission timing of the first ultrasonic sensor, i.e., the first transmission timing, and the transmission timing of the second ultrasonic sensor, i.e., the second transmission timing, when one of the plurality of ultrasonic sensors is set as the first ultrasonic sensor and the other is set as the second ultrasonic sensor.

[0016] The plurality of ultrasonic sensors are configured such that each of the plurality of ultrasonic sensors transmits the detection wave at the transmission timings different from each other.

[0017] According to another aspect of the present invention, the control device is configured to control the operation of each of the ultrasonic sensors in an object detection device having a plurality of ultrasonic sensors. Each of the plurality of ultrasonic sensors is configured to detect the object by transmitting a detection wave as an ultrasonic wave having different characteristics that can identify each other and receiving a reflection wave of the detection wave from a surrounding object.

[0018] The control device has:

[0019] a transmission timing setting unit that sets a transmission timing of the detection wave of each of the plurality of ultrasonic sensors; and

[0020] a transmission instruction unit for instructing each of the plurality of ultrasonic sensors to start transmission of the detection wave based on the transmission timing set by the transmission timing setting unit;

[0021] The transmission timing setting unit sets a delay time determined based on a positional relationship between the first ultrasonic sensor and the second ultrasonic sensor between the transmission timing of the first ultrasonic sensor, i.e., the first transmission timing, and the transmission timing of the second ultrasonic sensor, i.e., the second transmission timing, when one of the plurality of ultrasonic sensors is set as the first ultrasonic sensor and the other is set as the second ultrasonic sensor.

[0022] The plurality of ultrasonic sensors are configured such that each of the plurality of ultrasonic sensors transmits the detection wave at the transmission timings different from each other.

[0023] According to another aspect of the present invention, an object detection method is a method performed by an object detection device, the object detection device comprising:

[0024] a plurality of ultrasonic sensors, each of which detects the object by transmitting a detection wave as an ultrasonic wave and receiving a reflection wave of the detection wave from a surrounding object; and

[0025] a control unit for controlling the operation of each of the plurality of ultrasonic sensors;

[0026] In the above object detection method,

[0027] Each of the plurality of ultrasonic sensors transmits the detection wave having different characteristics that can identify each other.

[0028] setting a transmission timing of the detection wave of each of the plurality of ultrasonic sensors;

[0029] Based on the set transmission timing, each of the plurality of ultrasonic sensors is instructed to start the transmission operation of the detection wave,

[0030] In the above setting of sending timing,

[0031] When one of the plurality of ultrasonic sensors is set as a first ultrasonic sensor and another one is set as a second ultrasonic sensor, a delay time determined based on a positional relationship between the first ultrasonic sensor and the second ultrasonic sensor is set between the transmission timing of the first ultrasonic sensor, i.e., the first transmission timing, and the transmission timing of the second ultrasonic sensor, i.e., the second transmission timing,

[0032] The plurality of ultrasonic sensors are configured such that each of the plurality of ultrasonic sensors transmits the detection wave at the transmission timings different from each other.

[0033] In addition, in each column of the application form, each element is sometimes marked with a reference symbol in brackets. However, the reference symbol is only an example of the correspondence between the element and the specific unit described in the embodiment described later. Therefore, the present invention is not limited in any way by the description of the above reference symbols. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] Figure 1 This is a block diagram showing a schematic configuration of an object detection device and a control unit according to an embodiment.

[0035] Figure 2 Yes means Figure 1 A conceptual diagram showing an overview of a method for setting transmission timing of an object detection device and a control unit shown.

[0036] Figure 3 Yes means Figure 1 A timing chart showing an example of the transmission and reception operation of the object detection device shown.

[0037] Figure 4 Yes means Figure 1 FIG. 2 is a timing chart showing another example of the transmission and reception operation of the object detection device shown.

[0038] Figure 5 Yes means Figure 1 A timing chart showing another example of the transmission and reception operation of the object detection device shown.

[0039] Figure 6 Yes means Figure 1 A timing chart showing another example of the transmission and reception operation of the object detection device shown.

[0040] Figure 7 Yes means Figure 1 A flowchart of an operation example of the object detection device shown.

[0041] Figure 8 Yes means Figure 7 A flowchart of an example of the transmission condition setting operation shown.

[0042] Fig. 9 Yes means Figure 7 A flowchart of another example of the transmission condition setting operation is shown.

[0043] Fig.10 Yes means Figure 7 A flowchart of another example of the transmission condition setting operation is shown. DETAILED DESCRIPTION

[0044] (Implementation Method)

[0045] Hereinafter, embodiments of the present invention will be described based on the accompanying drawings. In addition, if various modifications that can be applied to an embodiment are inserted in the middle of a series of descriptions related to the embodiment, it is possible to hinder the understanding of the embodiment. Therefore, the modifications are summarized and recorded after the description of the embodiment.

[0046] (Overall structure)

[0047] If you refer to Figure 1 The object detection device 1 is configured to be mounted on a vehicle (not shown) and detect an object B around the vehicle. The vehicle on which the object detection device 1 is mounted is hereinafter referred to as a "host vehicle". The vehicle (not shown) is, for example, a car.

[0048] The object detection device 1 includes a plurality of ultrasonic sensors 2 and a control unit 3 that controls the operation of each of the plurality of ultrasonic sensors 2. Each of the plurality of ultrasonic sensors 2 is configured to detect an object B by transmitting a detection wave as an ultrasonic wave and receiving a reflection wave of the detection wave from the object B.

[0049] The ultrasonic sensor 2 includes a transducer 21, a transmitting circuit 22, a receiving circuit 23, a drive signal generating unit 24, and a receiving signal processing unit 25. The transducer 21 has a function as a transmitter for transmitting detection waves to the outside and a function as a receiver for receiving reflected waves, and is electrically connected to the transmitting circuit 22 and the receiving circuit 23. That is, the ultrasonic sensor 2 has a so-called transmitting and receiving integrated structure.

[0050] Specifically, the transducer 21 is configured as an ultrasonic microphone having an electromechanical energy conversion element such as a piezoelectric element built in. The transducer 21 is arranged at a position facing the outer surface of the vehicle so as to be able to transmit detection waves to the outside of the vehicle and receive reflected waves from the outside of the vehicle.

[0051] The transmitting circuit 22 is configured to drive the transducer 21 based on the input drive signal, so that the transducer 21 transmits the detection wave. Specifically, the transmitting circuit 22 has a digital / analog conversion circuit, etc. That is, the transmitting circuit 22 is configured to generate an element input signal by performing signal processing such as digital / analog conversion on the drive signal output from the drive signal generating unit 24. The element input signal is an AC voltage signal for driving the transducer 21. Moreover, the transmitting circuit 22 is configured to excite the electromechanical energy conversion element of the transducer 21 by applying the generated element input signal to the transducer 21, thereby generating a detection wave.

[0052] The receiving circuit 23 is configured to generate a receiving signal corresponding to the reception result of the receiving wave based on the transducer 21 and output it to the receiving signal processing unit 25. Specifically, the receiving circuit 23 has an amplifier circuit and an analog / digital conversion circuit. That is, the receiving circuit 23 is configured to generate a receiving signal including information related to the amplitude and frequency of the receiving wave by performing signal processing such as amplification and analog / digital conversion on the element output signal output by the transducer 21. The element output signal is an AC voltage signal generated by the electromechanical energy conversion element provided in the transducer 21 by receiving the receiving wave.

[0053] The drive signal generating unit 24 is provided to generate a drive signal and output the drive signal to the transmitting circuit 22. The drive signal is a signal for driving the transducer 21 and transmitting the detection wave from the transducer 21.

[0054] The plurality of ultrasonic sensors 2 are arranged so that the detection waves of the respective ultrasonic sensors 2 have different characteristics that can identify each other. That is, the drive signal generating unit 24 is configured to generate a drive signal that imparts a characteristic that can identify a transmission source to the detection wave. Specifically, in the present embodiment, the drive signal generating unit 24 generates a drive signal corresponding to a frequency modulation state in a detection wave having a predetermined frequency modulation state.

[0055] The prescribed frequency modulation state includes, for example, an uplink or a downlink. The uplink is a frequency modulation state in which the frequency increases monotonically over time. The downlink is a frequency modulation state in which the frequency decreases monotonically over time. Specifically, for example, the drive signal generating unit 24 is configured to be able to assign a multi-bit code that is a combination of an uplink signal corresponding to the code "01", a downlink signal corresponding to the code "10", and a CW signal corresponding to the code "11" to the detection wave. The CW signal is a constant frequency signal whose frequency does not change over time. CW is the abbreviation of continuous waveform. The "constant frequency" state corresponding to the CW signal is also included in the "frequency modulation state". The CW signal is also called a CF signal. CF is the abbreviation of continuous frequency.

[0056] The drive signal generating unit 24 of each of the plurality of ultrasonic sensors 2 is configured to generate and output drive signals corresponding to different coding states. Specifically, for example, the drive signal generating unit 24 in one ultrasonic sensor 2 generates a drive signal corresponding to a 3-bit code such as "01, 10, 11". In addition, the drive signal generating unit 24 in another ultrasonic sensor 2 generates a drive signal corresponding to a 3-bit code such as "10, 01, 11".

[0057] The receiving signal processing unit 25 is configured to generate an amplitude signal and a receiving frequency signal by performing processing such as FFT on the receiving signal. FFT is the abbreviation of Fast Fourier Transform. The amplitude signal is a signal corresponding to the amplitude of the received wave. The receiving frequency signal is a frequency signal in the received wave, that is, a signal corresponding to the receiving frequency. In other words, the receiving frequency signal is a signal in the received signal that corresponds to the coding state. In addition, the receiving signal processing unit 25 is configured to output the generated amplitude signal and receiving frequency signal to the control unit 3.

[0058] (Control device)

[0059] The control unit 3 is connected to the plurality of ultrasonic sensors 2 via an in-vehicle communication line so as to be able to communicate information. The control unit 3 , which corresponds to the control device of the present invention, is configured to control the transmission and reception operations of each of the plurality of ultrasonic sensors 2 .

[0060] The control unit 3 is configured as a so-called sonar ECU, and has an on-board microcomputer having a CPU, ROM, RAM, non-volatile rewritable memory, etc., which are not shown in the figure. ECU is the abbreviation of Electronic Control Unit. Non-volatile rewritable memory is, for example, EEPROM, flash ROM, etc. EEPROM is the abbreviation of Electronically Erasable and Programmable Read Only Memory. Hereinafter, the CPU, ROM, RAM, and non-volatile rewritable memory of the control unit 3 are referred to as "CPU", "ROM", "RAM", and "non-volatile RAM". As a functional structure implemented by the on-board microcomputer, the control unit 3 has a sending timing setting unit 31, a sending instruction unit 32, and a detection result acquisition unit 33.

[0061] The transmission timing setting unit 31 is configured to set the transmission timing of the detection wave of each ultrasonic sensor 2 in the plurality of ultrasonic sensors 2. In the present embodiment, the transmission timing setting unit 31 is configured to set the delay time based on the mutual positional relationship of each ultrasonic sensor 2 in the plurality of ultrasonic sensors 2 so that each ultrasonic sensor 2 in the plurality of ultrasonic sensors 2 transmits the detection wave at a mutually different transmission timing. Specifically, the transmission timing setting unit 31 includes a basic timing setting unit 311 and a delay time setting unit 312.

[0062] The basic timing setting unit 311 is configured to set a basic timing for each of the plurality of ultrasonic sensors 2. The basic timing is a transmission timing set to arrive at the same cycle in each of the plurality of ultrasonic sensors 2. That is, the basic timing is the transmission timing before correction by the delay time setting unit 312.

[0063] The delay time setting unit 312 is configured to set a delay time for each of the plurality of ultrasonic sensors 2 so that the transmission timing arriving at a predetermined period is time-shifted from the basic timing. That is, the delay time setting unit 312 is configured to set the delay time for the basic timing based on the mutual positional relationship of each of the plurality of ultrasonic sensors 2. Specifically, the delay time setting unit 312 delays the transmission timing of the detection wave in other ultrasonic sensors 2 that are different from the ultrasonic sensor 2 that transmits the detection wave at a constant period at the basic timing by the amount of the delay time from the basic timing. A specific example of the setting of the delay time will be described later.

[0064] The transmission instruction unit 32 is configured to instruct each of the plurality of ultrasonic sensors 2 to start the transmission of the detection wave based on the transmission timing set by the transmission timing setting unit 31. Specifically, the transmission instruction unit 32 sends a control signal to the ultrasonic sensor 2 whose transmission timing arrives, thereby causing the ultrasonic sensor 2 to start the transmission of the detection wave.

[0065] The detection result acquisition unit 33 is configured to acquire the amplitude signal and the reception frequency signal from the reception signal processing unit 25, and detect the object B based on the acquired amplitude signal and the reception frequency signal. Specifically, the detection result acquisition unit 33 compares the acquired reception frequency signal with a predetermined reference signal pre-stored in a ROM or a non-volatile RAM and decodes the reception frequency signal to determine the code included in the corresponding reception wave. In addition, when the code determination is successful, the detection result acquisition unit 33 specifies the corresponding transducer 21, and specifies the distance from the transducer 21 to the object B based on the amplitude signal.

[0066] (Action Overview)

[0067] The following describes the operation overview of the structure of this embodiment and the effects achieved by the structure while referring to the attached drawings. Figure 1 While explaining.

[0068] In an object detection device 1 having a plurality of ultrasonic sensors 2 and an object detection method performed by the object detection device 1, it is required to shorten the detection cycle as much as possible to speed up the detection. In this regard, if the plurality of ultrasonic sensors 2 can transmit the detection waves simultaneously without setting a time difference in the transmission timing of the detection waves, the overall detection cycle of the object detection device 1 can be minimized.

[0069] However, if multiple ultrasonic sensors are used to transmit and receive ultrasonic waves simultaneously, the reflections of multiple detection waves from different transmission sources from object B overlap with each other, thereby generating an insensitive zone that cannot be detected. Specifically, for example, due to the overlap of multiple reflections, the code used to identify the transmission source fails to be determined.

[0070] On the other hand, it is conceivable to adopt a structure and method in which a plurality of ultrasonic sensors 2 are used to transmit and receive simultaneously, and two or more specific ultrasonic sensors that detect the obstacle, i.e., the object B, are sequentially switched to transmit, as in the apparatus and method disclosed in Patent Document 1. However, in this structure and method, it takes time until two or more ultrasonic sensors 2 that detect the object B are specifically detected. In addition, in a state where the ultrasonic sensor 2 that transmits is limited to a specific ultrasonic sensor among the plurality of ultrasonic sensors 2, the detectable range is limited.

[0071] Therefore, in the present embodiment, the control unit 3 controls the transmission timing of each ultrasonic sensor 2 among the plurality of ultrasonic sensors 2 so that each ultrasonic sensor 2 among the plurality of ultrasonic sensors 2 transmits the detection wave at a different transmission timing. That is, the transmission timing setting unit 31 sets a delay time for each ultrasonic sensor among the plurality of ultrasonic sensors 2 based on the relative position of each ultrasonic sensor 2 among the plurality of ultrasonic sensors 2.

[0072] One side reference Figure 1 to Figure 4 , while explaining the overview of the delay time setting. Figure 1 In the embodiment, one of the plurality of ultrasonic sensors 2 is set as the first ultrasonic sensor SS1, and the other is set as the second ultrasonic sensor SS2. The propagation path between the transducer 21 in the first ultrasonic sensor SS1 and the object B is called the first propagation path P1, and the propagation path between the transducer 21 in the second ultrasonic sensor SS2 and the object B is called the second propagation path P2.

[0073] Figure 2The overview of the positional relationship between the first ultrasonic sensor SS1, the second ultrasonic sensor SS2, the first detection range DR1, and the second detection range DR2 in the top view of the vehicle from directly above is shown. The first detection range DR1 is a detection range based on the first ultrasonic sensor SS1. The second detection range DR2 is a detection range based on the second ultrasonic sensor SS2. The sensor interval DS is the interval between the first ultrasonic sensor SS1 and the second ultrasonic sensor SS2. More precisely, the sensor interval DS is the interval between the transducer 21 provided in the first ultrasonic sensor SS1 and the transducer 21 provided in the second ultrasonic sensor SS2.

[0074] Figure 3 and Figure 4 FIG. 2 shows an overview of the transmission and reception operations of the first ultrasonic sensor SS1 and the second ultrasonic sensor SS2. Figure 3 In the above, the horizontal axis represents time T, the rectangle represents the transmission waveform of the detection wave, and the triangle represents the reception waveform of the reception wave. The first detection wave W1 is the detection wave transmitted by the first ultrasonic sensor SS1, and the second detection wave W2 is the detection wave transmitted by the second ultrasonic sensor SS2. The first transmission timing Tt1 is the transmission timing of the first detection wave W1 in the first ultrasonic sensor SS1, that is, the transmission start timing. The second transmission timing Tt2 is the transmission timing of the second detection wave W2 in the second ultrasonic sensor SS2, that is, the transmission start timing.

[0075] In addition, Figure 3 In the above, the first direct wave R11 is the received wave when the first ultrasonic sensor SS1 receives the reflected wave of the first detection wave W1 from the object B as the received wave. The first indirect wave R12 is the received wave when the second ultrasonic sensor SS2 receives the reflected wave of the first detection wave W1 from the object B as the received wave. The second indirect wave R21 is the received wave when the first ultrasonic sensor SS1 receives the reflected wave of the second detection wave W2 from the object B as the received wave. The second direct wave R22 is the received wave when the second ultrasonic sensor SS2 receives the reflected wave of the second detection wave W2 from the object B as the received wave.

[0076] The transmission timing setting unit 31, i.e., the delay time setting unit 312, sets the delay time ΔT determined based on the positional relationship between the first ultrasonic sensor SS1 and the second ultrasonic sensor SS2 between the first transmission timing Tt1 and the second transmission timing Tt2. In addition, when the delay time ΔT is positive, it is the time interval between the transmission timing of the first detection wave W1 and the transmission timing of the second detection wave W2 that arrives immediately thereafter. On the other hand, when the delay time ΔT is negative, it is the time interval between the transmission timing of the first detection wave W1 and the transmission timing of the second detection wave W2 that arrives immediately thereafter.

[0077] Specifically, the delay time setting unit 312 sets the delay time ΔT to a value greater than or equal to the value obtained by dividing the maximum propagation path difference in the overlapping range DRM by the speed of sound. The overlapping range DRM is a range in which the first detection range DR1 overlaps the second detection range DR2. The first detection range DR1 can be approximately represented by a rough teardrop shape obtained by joining the bottom surface of an elliptical cone with the transducer 21 in the first ultrasonic sensor SS1 as the vertex and a semi-rotated ellipsoid having a bottom surface of the same shape as the bottom surface at their respective bottom surfaces. The above-mentioned bottom surface is an ellipse having a major axis parallel to the horizontal direction and a minor axis parallel to the height direction. Similarly, the second detection range DR2 can be approximately represented by a rough teardrop shape obtained by joining the bottom surface of an elliptical cone with the transducer 21 in the second ultrasonic sensor SS2 as the vertex and a semi-rotated ellipsoid having a bottom surface of the same shape as the bottom surface at their respective bottom surfaces. The overlapping range DRM can be represented by a three-dimensional range in which the two rough teardrop shapes overlap each other.

[0078] The maximum propagation path difference is Figure 2 The difference between the first reference propagation path P1X and the second reference propagation path P2X shown, i.e., |P1X-P2X|. The first reference propagation path P1X is the propagation path between the transducer 21 in the first ultrasonic sensor SS1 and the reference point BX. The second reference propagation path P2X is the propagation path between the transducer 21 in the second ultrasonic sensor SS2 and the reference point BX. The reference point BX is a coordinate point included in the overlapping range DRM, and is the point where the difference between the first propagation path P1 and the second propagation path P2, i.e., the propagation path difference, becomes the maximum. Figure 3 This indicates the case where the delay time ΔT is set to a value obtained by dividing the maximum propagation path difference by the speed of sound. That is, Figure 3 It shows the lower limit value of the delay time ΔT determined based on the positional relationship between the first ultrasonic sensor SS1 and the second ultrasonic sensor SS2.

[0079] The delay time setting unit 312 sets the delay time ΔT to be equal to or smaller than a value obtained by dividing the sensor interval DS by the speed of sound. Figure 4This indicates the case where the delay time ΔT is set to a value obtained by dividing the sensor interval DS by the speed of sound. Figure 4 It shows the upper limit value of the delay time ΔT determined based on the positional relationship between the first ultrasonic sensor SS1 and the second ultrasonic sensor SS2.

[0080] By setting the delay time ΔT as described above, the overlap between the first direct wave R11 and the second indirect wave R21 in the first ultrasonic sensor SS1 can be avoided as much as possible. Similarly, the overlap between the second direct wave R22 and the first indirect wave R12 in the second ultrasonic sensor SS2 can be avoided as much as possible. Therefore, according to this embodiment, a device structure and an object detection method that can well realize high-speed detection based on a shortened object detection cycle are provided.

[0081] Even if only the delay time ΔT is set as described above, interference caused by overlapping of received waves or overlapping of received waves and reverberation may occur. Therefore, in the structure and method of this embodiment, the delay time setting unit 312 changes the delay time ΔT during the execution of the transmission processing based on the plurality of ultrasonic sensors 2.

[0082] Specifically, for example, the delay time setting unit 312 changes the delay time ΔT each time the first transmission timing Tt1 arrives, thereby making it possible to make the delay time ΔT from the previous first transmission timing Tt1 to the immediately following second transmission timing Tt2 different from the delay time from the current first transmission timing Tt1 to the immediately following second transmission timing Tt2.

[0083] Figure 5 and Figure 6 This shows an example in which the delay time ΔT is switched between the first delay time ΔT1 and the second delay time ΔT2 every time the first transmission timing Tt1 arrives. Figure 5 In the example shown, the first delay time ΔT1 = ΔT, and the second delay time ΔT2 = -ΔT. Figure 5 In the example shown, the absolute value of the delay time ΔT is constant and switches between positive and negative alternately.

[0084] On the other hand, Figure 6 In the example shown, the first delay time ΔT1 and the second delay time ΔT2 are both positive values, and their absolute values ​​are different from each other. The change amount ΔT1-ΔT2 of the delay time ΔT is, for example, the time width of the received signal of the reflected wave, that is, the received wave time width BW or more. The received wave time width BW is, for example, the time width corresponding to the length of the bottom side when the received wave is approximated as a triangular wave.

[0085] Alternatively, the change amount ΔT1-ΔT2 of the delay time ΔT is, for example, greater than the reverberation time. As is well known, the "reverberation time" is the time from the end of the driving time to the convergence of the reverberation (i.e., the amplitude in the amplitude waveform corresponding to the reverberation reaches a predetermined threshold). In this embodiment, as the predetermined threshold for the predetermined reverberation time, the same value as the threshold for determining the presence or absence of reception of the received wave, i.e., the threshold for distinguishing between road surface reflected waves and noise and received waves can be used. Figure 6 In the figure, the rectangle representing the transmission waveform of the detection wave in the first detection wave W1 and the second detection wave W2 represents the driving time of the ultrasonic sensor 2, that is, the driving time of the transducer 21. The driving time corresponds to the output period of the driving signal. In addition, after the rectangle representing the driving time, the waveform representing the reverberation is represented in a simplified form. It is more preferred that the change amount ΔT1-ΔT2 of the delay time ΔT is, for example, greater than the insensitive zone time, which includes the driving time and reverberation time of the ultrasonic sensor 2 for transmitting the detection wave.

[0086] use Figure 7 and Figure 8 , an example of switching the delay time ΔT between the first delay time ΔT1 and the second delay time ΔT2 each time the transmission timing arrives is described. In the figure, "S" is the abbreviation of "step". When the object detection condition is met, the CPU in the control unit 3 reads and executes the object detection condition from the ROM or non-volatile RAM. Figure 7 The object detection procedure shown.

[0087] like Figure 7 The program shown is started. First, in step 701, the CPU sets a transmission condition including a delay time ΔT. The details of the transmission condition setting will be described later. Next, in step 702, the CPU executes a transmission / reception process based on the transmission condition set in step 701.

[0088] Next, in step 703, the CPU performs a code determination based on the decoding of the received signal. Finally, in step 704, the CPU determines the object detection result based on the code determination result. Specifically, when the code determination is successful, the CPU calculates the distance from the transducer 21 to the object B based on the corresponding amplitude signal. In addition, the CPU calculates the relative position of the object B relative to the vehicle based on the calculated result of the distance. In addition, for the threshold value, STC and TOF output of the detection result when determining the object detection result, the setting of the delay time ΔT must of course be considered. STC is the abbreviation of Sensitivity Time Control. TOF is the abbreviation of Time of Flight.

[0089] Figure 8The content of the transmission condition setting process of step 701 is shown. Figure 8 In step 801, the CPU determines whether the value of the counter N is 0.

[0090] When the value of counter N is 0 (ie, step 801 = "Yes"), the CPU executes the processing of steps 802 and 803 in sequence, and then proceeds to step 702. When step 801 is executed for the first time immediately after the object detection condition is satisfied, counter N is initialized to 0.

[0091] In step 802 , the CPU sets the delay time ΔT to the first delay time ΔT1. In step 803 , the CPU sets the value of counter N to 1. Therefore, when step 701 is executed next time, the value of counter N is 1, so the determination in step 801 is “No”, and the process proceeds to step 804 .

[0092] On the other hand, when the value of counter N is not 0 (i.e., step 801 = "No"), the CPU executes the processing of steps 804 and 805 in sequence, and then proceeds to step 702. In step 804, the CPU sets the delay time ΔT to the second delay time ΔT2. In step 805, the CPU sets the value of counter N to 0. Therefore, when step 701 is executed next time, the value of counter N is 0, so the determination of step 801 is "Yes", and the processing proceeds to step 802.

[0093] (Variation Example)

[0094] The present invention is not limited to the above-mentioned embodiment. Therefore, the above-mentioned embodiment can be appropriately changed. Below, a representative modification is described. In the following description of the modification, the difference from the above-mentioned embodiment is mainly described. In addition, in the above-mentioned embodiment and the modification, the same figure mark is marked for the mutually identical or equal parts. Therefore, in the description of the following modification, with respect to the constituent elements with the same figure mark as the above-mentioned embodiment, as long as there is no technical contradiction or special additional description, the description of the above-mentioned embodiment can be appropriately cited.

[0095] The object detection device 1 is not limited to being mounted on a vehicle, that is, installed on a vehicle. That is, for example, the object detection device 1 may also be installed on a ship or an aircraft.

[0096] The object detection device 1 is not limited to a configuration capable of transmitting and receiving ultrasonic waves by a single transducer 21. That is, for example, a transmitting transducer 21 electrically connected to the transmitting circuit 22 and a receiving transducer 21 electrically connected to the receiving circuit 23 may be provided in parallel.

[0097] The configurations of the ultrasonic sensor 2 and the control unit 3 are not limited to the specific examples shown in the above embodiment. That is, for example, a digital / analog conversion circuit may be provided in the drive signal generation unit 24 instead of the transmission circuit 22 .

[0098] The drive signal generation unit 24 may be provided in the control unit 3 . Similarly, the reception signal processing unit 25 may be provided in the control unit 3 .

[0099] The encoding method is not limited to chirp encoding. That is, for example, phase modulation or on-off modulation may be used for encoding.

[0100] The change method of the delay time ΔT is also not limited to the above-mentioned specific example. That is, for example, three or more fixed delay times ΔT can be applied sequentially or randomly. In addition, the predetermined threshold value that specifies the "reverberation time" when the change amount ΔT1-ΔT2 of the delay time ΔT is greater than the reverberation time may not be the same as the threshold value for distinguishing the road surface reflected wave and the noise from the received wave. Specifically, for example, the predetermined threshold value may also be a threshold value for the degree of residual reverberation that allows the degree of distinction from the received wave.

[0101] The change amount ΔT1 - ΔT2 of the delay time ΔT may be constant, or may be changed cyclically or randomly.

[0102] As long as the received reflected wave does not overlap with the reverberation, or the received reflected waves do not overlap with each other, the delay time ΔT may not be changed. In other words, the transmission timing setting unit 31, i.e., the delay time setting unit 312 may change the delay time ΔT when the received reflected wave overlaps with the reverberation, or the received reflected waves overlap with each other in the second ultrasonic sensor SS2.

[0103] Fig. 9 This shows an example of changing the delay time ΔT when the received reflected wave overlaps with the reverberation. Fig. 9 The subprocess shown replaces Figure 8 The subprocess shown.

[0104] If you refer to Fig. 9 In step 901, the CPU determines whether the received reflected wave overlaps with the reverberation. Figure 6 An example in which the reverberation in the second detection wave W2 overlaps with the first indirect wave R12 is shown.

[0105] If the received wave and the reverberation overlap (i.e., step 901 = "Yes"), the CPU sequentially executes the processing of steps 902 and 903, and then proceeds to step 702. On the other hand, if the received wave and the reverberation do not overlap (i.e., step 901 = "No"), the CPU skips the processing of steps 902 and 903, and proceeds to step 702.

[0106] In step 902, the CPU determines the correction value α according to the overlapping state of the received wave and the reverberation. Specifically, for example, the CPU determines the correction value α according to the reverberation time. In step 903, the CPU changes the delay time ΔT by correcting the delay time ΔT using the correction value α.

[0107] Fig.10 This shows an example of changing the delay time ΔT when the received reflected waves overlap and the code determination fails. Fig.10 In step 1001, the CPU determines whether the received reflected waves overlap with each other.

[0108] When the received reflected waves overlap with each other (i.e., step 1001 = "Yes"), the CPU sequentially executes the processing of steps 1002 and 1003, and then proceeds to step 702. On the other hand, when the received reflected waves do not overlap with each other (i.e., step 1001 = "No"), the CPU skips the processing of steps 1002 and 1003, and proceeds to step 702.

[0109] In step 1002, the CPU determines the correction value α according to the overlapping state of the received waves. In step 1003, the CPU changes the delay time ΔT by correcting the delay time ΔT using the correction value α.

[0110] Fig. 9 Examples with Fig.10 That is, for example, when the determination at step 901 is "No", the processing at steps 1001 to 1003 can be executed.

[0111] The above-mentioned functional structures and methods can also be implemented by a dedicated computer as follows, which is provided by a processor and a memory programmed to perform one or more functions embodied by a computer program. Alternatively, the above-mentioned functional structures and methods can also be implemented by a dedicated computer as follows, which is provided by a processor composed of one or more dedicated hardware logic circuits. Alternatively, the above-mentioned functional structures and methods can also be implemented by one or more dedicated computers as follows, which are composed of a processor and a memory programmed to perform one or more functions and a processor composed of one or more hardware logic circuits. Specifically, the control unit 3 is not limited to a well-known microcomputer having a CPU, etc. That is, all or part of the control unit 3 can also be a digital circuit, such as an ASIC or FPGA, that can realize the above-mentioned functions. ASIC is the abbreviation of Application Specific Integrated Circuit. FPGA is the abbreviation of Field Programmable Gate Array. In addition, a computer program can also be stored in a computer-readable non-migrating physical storage medium as an instruction executed by a computer. That is, the apparatus or method of the present invention can be expressed as a computer program including a procedure for realizing the above-mentioned functions or methods, or a non-migrating physical storage medium storing the program.

[0112] Regarding the elements constituting the above-mentioned embodiments, except for the cases that are specifically indicated as necessary and the cases that are clearly considered to be necessary in principle, etc., they are of course not necessarily necessary. In addition, when referring to the numerical values ​​of the number, value, amount, range, etc. of the constituent elements, except for the cases that are specifically indicated as necessary and the cases that are clearly limited to a specific number in principle, etc., the present invention is not limited to the specific number. Similarly, when referring to the shape, direction, positional relationship, etc. of the constituent elements, etc., except for the cases that are specifically indicated as necessary and the cases that are limited to a specific shape, direction, positional relationship, etc. in principle, the present invention is not limited to the shape, direction, positional relationship, etc.

[0113] The modification examples are not limited to the above-mentioned examples. In addition, a plurality of modification examples can be combined with each other. Furthermore, all or part of the above-mentioned embodiment and all or part of the modification examples can be combined with each other.

[0114] In this specification, the following devices are disclosed in the broadest sense.

[0115] The object detection device (1) comprises:

[0116] A plurality of ultrasonic sensors (2), each of which detects the object by transmitting a detection wave as an ultrasonic wave and receiving a reflection wave of the detection wave from a surrounding object (B); and

[0117] A control unit (3) controls the operation of each of the plurality of ultrasonic sensors.

[0118] The plurality of ultrasonic sensors are arranged so that the detection waves of the respective ultrasonic sensors have different characteristics that can be identified from each other.

[0119] The control unit includes a transmission timing setting unit (31) for setting the transmission timing of the detection wave of each of the plurality of ultrasonic sensors.

[0120] The transmission timing setting unit sets a delay time determined based on the positional relationship between the first ultrasonic sensor and the second ultrasonic sensor between the transmission timing of the first ultrasonic sensor, i.e., the first transmission timing (Tt1), and the transmission timing of the second ultrasonic sensor, i.e., the second transmission timing (Tt2), when one of the plurality of ultrasonic sensors is set as the first ultrasonic sensor and the other is set as the second ultrasonic sensor.

[0121] The plurality of ultrasonic sensors are configured such that each of the plurality of ultrasonic sensors transmits the detection wave at the transmission timings different from each other.

[0122] A control device (3) is configured to control the operation of each ultrasonic sensor in an object detection device (1) having a plurality of ultrasonic sensors (2). Each of the plurality of ultrasonic sensors is configured to detect the object by transmitting a detection wave as an ultrasonic wave having different characteristics that can identify each other and receiving a reflection wave of the detection wave from a surrounding object (B).

[0123] The control device comprises a transmission timing setting unit (31) for setting the transmission timing of the detection wave of each of the plurality of ultrasonic sensors.

[0124] The transmission timing setting unit sets a delay time determined based on the positional relationship between the first ultrasonic sensor and the second ultrasonic sensor between the transmission timing of the first ultrasonic sensor, i.e., the first transmission timing (Tt1), and the transmission timing of the second ultrasonic sensor, i.e., the second transmission timing (Tt2), when one of the plurality of ultrasonic sensors is set as the first ultrasonic sensor and the other is set as the second ultrasonic sensor.

[0125] The plurality of ultrasonic sensors are configured such that each of the plurality of ultrasonic sensors transmits the detection wave at the transmission timings different from each other.

Claims

1. An object detection device, comprising: a plurality of ultrasonic sensors, each of which detects an object by transmitting a detection wave as an ultrasonic wave and receiving a reflection wave of the detection wave from a surrounding object; and a control unit that controls the operation of each of the plurality of ultrasonic sensors; The plurality of ultrasonic sensors are arranged so that the detection waves of the respective ultrasonic sensors have different characteristics that can be identified from each other. The control unit comprises: a transmission timing setting unit that sets a transmission timing of the detection wave of each of the plurality of ultrasonic sensors; and a transmission instruction unit for instructing each of the plurality of ultrasonic sensors to start a transmission operation of the detection wave based on the transmission timing set by the transmission timing setting unit; When one of the plurality of ultrasonic sensors is set as a first ultrasonic sensor and another one is set as a second ultrasonic sensor, the transmission timing setting unit sets a delay time between the transmission timing of the first ultrasonic sensor, that is, a first transmission timing, and the transmission timing of the second ultrasonic sensor, that is, a second transmission timing, The sending timing setting unit sets the delay time to a value greater than the maximum value of the difference between the propagation path of the detection wave from the first ultrasonic sensor and the propagation path of the detection wave from the second ultrasonic sensor, i.e., the propagation path difference, in the overlapping range where the detection range based on the first ultrasonic sensor, i.e., the first detection range, overlaps with the detection range based on the second ultrasonic sensor, i.e., the second detection range, divided by the speed of sound.

2. The object detection device according to claim 1, wherein: The transmission timing setting unit sets the delay time to be equal to or less than a value obtained by dividing a sensor interval, which is an interval between the first ultrasonic sensor and the second ultrasonic sensor, by a speed of sound.

3. The object detection device according to claim 1 or 2, wherein: The transmission timing setting unit changes the delay time each time the first transmission timing arrives so that the delay time from the previous first transmission timing to the immediately subsequent second transmission timing is different from the delay time from the current first transmission timing to the immediately subsequent second transmission timing.

4. The object detection device according to claim 1 or 2, wherein: The transmission timing setting unit changes the delay time when superposition of the received reflected wave and reverberation or superposition of the received reflected waves occurs in the second ultrasonic sensor.

5. The object detection device according to claim 3, wherein: The transmission timing setting unit sets the change amount of the delay time to be equal to or greater than the time width of the reception signal of the reflected wave.

6. The object detection device according to claim 4, wherein: The transmission timing setting unit sets the change amount of the delay time to be equal to or greater than the time width of the reception signal of the reflected wave.

7. The object detection device according to claim 3, wherein: The transmission timing setting unit sets the change amount of the delay time to be equal to or greater than the reverberation time.

8. The object detection device according to claim 4, wherein: The transmission timing setting unit sets the change amount of the delay time to be equal to or greater than the reverberation time.

9. A control device for controlling the operation of each of a plurality of ultrasonic sensors in an object detection device having a plurality of ultrasonic sensors, wherein each of the ultrasonic sensors detects an object by transmitting a detection wave as an ultrasonic wave having different characteristics that can identify each other and receiving a reflection wave of the detection wave from a surrounding object, The control device comprises: a transmission timing setting unit that sets a transmission timing of the detection wave of each of the plurality of ultrasonic sensors; and a transmission instruction unit for instructing each of the plurality of ultrasonic sensors to start a transmission operation of the detection wave based on the transmission timing set by the transmission timing setting unit; When one of the plurality of ultrasonic sensors is set as a first ultrasonic sensor and another one is set as a second ultrasonic sensor, the transmission timing setting unit sets a delay time between the transmission timing of the first ultrasonic sensor, that is, a first transmission timing, and the transmission timing of the second ultrasonic sensor, that is, a second transmission timing, The sending timing setting unit sets the delay time to a value greater than the maximum value of the difference between the propagation path of the detection wave from the first ultrasonic sensor and the propagation path of the detection wave from the second ultrasonic sensor, i.e., the propagation path difference, in the overlapping range where the detection range based on the first ultrasonic sensor, i.e., the first detection range, overlaps with the detection range based on the second ultrasonic sensor, i.e., the second detection range, divided by the speed of sound.

10. The control device according to claim 9, wherein: The transmission timing setting unit sets the delay time to be equal to or less than a value obtained by dividing a sensor interval, which is an interval between the first ultrasonic sensor and the second ultrasonic sensor, by a speed of sound.

11. The control device according to claim 9 or 10, wherein: The transmission timing setting unit changes the delay time each time the first transmission timing arrives so that the delay time from the previous first transmission timing to the immediately subsequent second transmission timing is different from the delay time from the current first transmission timing to the immediately subsequent second transmission timing.

12. The control device according to claim 9 or 10, wherein: The transmission timing setting unit changes the delay time when superposition of the received reflected wave and reverberation or superposition of the received reflected waves occurs in the second ultrasonic sensor.

13. The control device according to claim 11, wherein: The transmission timing setting unit sets the change amount of the delay time to be equal to or greater than the time width of the reception signal of the reflected wave.

14. The control device according to claim 12, wherein: The transmission timing setting unit sets the change amount of the delay time to be equal to or greater than the time width of the reception signal of the reflected wave.

15. The control device according to claim 11, wherein: The transmission timing setting unit sets the change amount of the delay time to be equal to or greater than the reverberation time.

16. The control device according to claim 12, wherein: The transmission timing setting unit sets the change amount of the delay time to be equal to or greater than the reverberation time.

17. An object detection method, performed by an object detection device, the object detection device comprising: a plurality of ultrasonic sensors, each of which detects an object by transmitting a detection wave as an ultrasonic wave and receiving a reflection wave of the detection wave from a surrounding object; and a control unit that controls the operation of each of the plurality of ultrasonic sensors; In the object detection method, Each of the plurality of ultrasonic sensors transmits the detection wave having different characteristics that can identify each other. setting a transmission timing of the detection wave of each of the plurality of ultrasonic sensors, Based on the set transmission timing, instructing each of the plurality of ultrasonic sensors to start the transmission operation of the detection wave, In the setting of the sending timing, When one of the plurality of ultrasonic sensors is set as a first ultrasonic sensor and another one is set as a second ultrasonic sensor, a delay time is set between the first transmission timing of the first ultrasonic sensor and the second transmission timing of the second ultrasonic sensor. The delay time is set to a value greater than the value obtained by dividing the maximum value of the difference between the propagation path of the detection wave from the first ultrasonic sensor and the propagation path of the detection wave from the second ultrasonic sensor, that is, the propagation path difference, in the overlapping range where the detection range based on the first ultrasonic sensor, that is, the first detection range, overlaps with the detection range based on the second ultrasonic sensor, that is, the second detection range, by the speed of sound.

18. The object detection method according to claim 17, wherein: In the setting of the transmission timing, the delay time is set to be equal to or less than a value obtained by dividing a sensor interval, which is an interval between the first ultrasonic sensor and the second ultrasonic sensor, by a speed of sound.

19. The object detection method according to claim 17 or 18, wherein: In the setting of the sending timing, the delay time is changed each time the first sending timing arrives so that the delay time from the last first sending timing to the second sending timing immediately thereafter is different from the delay time from the first sending timing this time to the second sending timing immediately thereafter.

20. The object detection method according to claim 17 or 18, wherein: In the setting of the transmission timing, when superposition of the received reflected wave and reverberation or superposition of the received reflected waves occurs in the second ultrasonic sensor, the delay time is changed.

21. The object detection method according to claim 19, wherein: In the setting of the transmission timing, the amount of change in the delay time is set to be equal to or greater than the time width of the reception signal of the reflected wave.

22. The object detection method according to claim 20, wherein: In the setting of the transmission timing, the amount of change in the delay time is set to be equal to or greater than the time width of the reception signal of the reflected wave.

23. The object detection method according to claim 19, wherein: In the setting of the transmission timing, the amount of change in the delay time is set to be equal to or greater than the reverberation time.

24. The object detection method according to claim 20, wherein: In the setting of the transmission timing, the amount of change in the delay time is set to be equal to or greater than the reverberation time.

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