Object detection device

Abstract

To provide an object detection device capable of accurately detecting an obstacle even when only either a direct wave or an indirect wave can be detected.SOLUTION: The object detection device is configured to correct a first direct wave distance and a second direct wave distance on the basis of the relative velocity between a moving body and an obstacle, calculate an obstacle distance using triangulation on the basis of the corrected first and second direct wave distances, correct a first indirect wave distance and a second indirect wave distance on the basis of the relative velocity, and calculate an obstacle distance using triangulation on the basis of the corrected first and second indirect wave distances.SELECTED DRAWING: Figure 4

Description

[Technical Field]

[0001] FIELD An embodiment of the present invention relates to an object detection device. [Background technology]

[0002] An object detection device that uses ultrasonic waves to detect obstacles around a vehicle employs a technology in which multiple transceivers that transmit and receive ultrasonic waves are installed on the vehicle body, and the distance from the vehicle to the obstacle is calculated based on the timing of transmission and reception of the ultrasonic waves at each transceiver. In such a configuration with multiple transceivers, the reflected waves received by each transceiver (ultrasound generated when ultrasonic waves (transmitted waves) transmitted from the transceiver are reflected by an object) include direct waves and indirect waves. A direct wave is a reflected wave corresponding to a transmitted wave transmitted from a certain transceiver and received by the same transceiver that transmitted the transmitted wave. An indirect wave is a reflected wave corresponding to a transmitted wave transmitted from a certain transceiver and received by a transceiver different from the transceiver that transmitted the transmitted wave. As a technology that utilizes such direct and indirect waves, a technology for estimating the position of an obstacle by combining two direct waves and two indirect waves has been disclosed (Patent Document 1). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2016-80648 Summary of the Invention [Problem to be solved by the invention]

[0004] However, in the conventional technology, it is necessary to detect both direct waves and indirect waves, and therefore it is not possible to improve detection accuracy in a situation where only direct waves or indirect waves can be detected.

[0005] One of the problems to be solved by the embodiments of the present invention is to provide an object detection device that can detect an obstacle with high accuracy even when only direct waves or indirect waves can be detected. [Means for solving the problem]

[0006] An object detection device according to one embodiment of the present invention is an object detection device that is mounted on a moving body and detects obstacles present around the moving body, and includes a plurality of transceivers that transmit and receive ultrasonic waves, and a calculation unit that calculates an obstacle distance, which is the distance from the moving body to the obstacle, based on the timing of transmission and reception of ultrasonic waves by each transceiver. When a reflected wave of a transmission wave transmitted from a first transceiver that is one of the plurality of transceivers is received by the first transceiver, and a reflected wave of a transmission wave transmitted from a second transceiver that is different from the first transceiver is received by the second transceiver, the calculation unit calculates a first direct wave distance based on the timing at which the transmission wave was transmitted from the first transceiver and the timing at which the reflected wave of the transmission wave was received by the first transceiver, and a second direct wave distance based on the timing at which the transmission wave was transmitted from the second transceiver and the timing at which the reflected wave of the transmission wave was received by the second transceiver, thereby calculating the distance between the moving body and the obstacle. The first direct wave distance and the second direct wave distance are corrected based on the relative speed, and the obstacle distance is calculated by trilateration based on the corrected first direct wave distance and the corrected second direct wave distance. When a reflected wave of a transmission wave transmitted from a third transceiver unit that is one of the multiple transceivers is received by a fourth transceiver unit different from the third transceiver unit, and the reflected wave of the transmission wave transmitted from the fourth transceiver unit is received by the third transceiver unit, a first indirect wave distance based on the timing when the transmission wave was transmitted from the third transceiver unit and the timing when the reflected wave of the transmission wave was received by the fourth transceiver unit, and a second indirect wave distance based on the timing when the transmission wave was transmitted from the fourth transceiver unit and the timing when the reflected wave of the transmission wave was received by the third transceiver unit are calculated, and the first indirect wave distance and the second indirect wave distance are corrected based on the relative speed, and the obstacle distance is calculated by trilateration based on the corrected first indirect wave distance and the corrected second indirect wave distance.

[0007] According to the above configuration, when direct waves are detected by two transmitters / receivers, two direct wave distances are calculated based on the direct waves, these direct wave distances are corrected based on the relative velocity, and the obstacle distance is calculated by trilateration based on the corrected direct wave distances. Also, when indirect waves are detected by two transmitters / receivers, two indirect wave distances are calculated based on the indirect waves, these indirect wave distances are corrected based on the relative velocity, and the obstacle distance is calculated by trilateration based on the corrected indirect wave distances. This allows for highly accurate obstacle detection by trilateration even when only direct waves or indirect waves can be detected.

[0008] In the above configuration, the relative velocity may be calculated based on a Doppler shift between the frequency of a transmitted wave and the frequency of a reflected wave corresponding to the transmitted wave.

[0009] According to the above configuration, the relative velocity can be calculated using information acquired from the transmitting and receiving unit.

[0010] In the above configuration, the calculation unit may discard the obstacle distance calculated by trilateration when the obstacle distance is greater than a predetermined threshold value.

[0011] According to the above configuration, it is possible to use only obstacle distances that are within a distance range where sufficient accuracy can be obtained, thereby improving the reliability of the obstacle distances.

[0012] In addition, in the above configuration, the calculation unit may discard the current obstacle distance if the difference between the current obstacle distance and the previous obstacle distance calculated a predetermined time before the time the current obstacle distance was calculated is greater than a predetermined threshold value.

[0013] Since obstacle distances that fluctuate significantly in a short period of time are likely to be noise, the above configuration can improve the reliability of the obstacle distance. [Brief explanation of the drawings]

[0014] [Figure 1] FIG. 1 is a diagram illustrating an example of the configuration of a vehicle according to an embodiment. [Figure 2] FIG. 2 is a diagram illustrating an example of the configuration of a vehicle control system according to the embodiment. [Figure 3] FIG. 3 is a diagram showing an example of a method for calculating distance using the TOF method. [Figure 4] FIG. 4 is a diagram illustrating an example of a functional configuration of the object detection device according to the embodiment. [Figure 5] FIG. 5 is a diagram illustrating an example of a first direct wave distance and a second direct wave distance according to the embodiment. [Figure 6] FIG. 6 is a diagram illustrating an example of the corrected first direct wave distance and the corrected second direct wave distance according to the embodiment. [Figure 7] FIG. 7 is a diagram illustrating an example of a first indirect wave distance and a second indirect wave distance according to the embodiment. [Figure 8] FIG. 8 is a diagram illustrating an example of the corrected first indirect wave distance and the corrected second indirect wave distance according to the embodiment. [Figure 9] FIG. 9 is a flowchart illustrating an example of processing in the object detection device according to the embodiment. [Figure 10] FIG. 10 is a flowchart showing an example of processing when outputting an obstacle distance in the object detection device according to the embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0015] Hereinafter, embodiments of the present disclosure will be described with reference to the drawings. The configurations of the embodiments described below and the actions and effects brought about by the configurations are merely examples, and the present invention is not limited to the following description.

[0016] 1 is a diagram showing an example of the configuration of a vehicle 1 according to an embodiment. The vehicle 1 is an example of a moving body on which an object detection device according to the embodiment is mounted. The object detection device according to the embodiment is a device that detects obstacles present around the vehicle 1 based on information such as TOF (Time Of Flight) and Doppler shift acquired by transmitting and receiving ultrasonic waves.

[0017] The object detection device according to this embodiment includes a plurality of transceivers 21A to 21L. Hereinafter, when there is no need to distinguish between the plurality of transceivers 21A to 21L, they may be referred to as transceivers 21. Each transceiver 21 is installed on the vehicle body 2, which is the exterior of the vehicle 1, transmits ultrasonic waves toward the outside of the vehicle body 2, and receives ultrasonic waves generated when the ultrasonic waves are reflected by an object present outside the vehicle body 2. Hereinafter, ultrasonic waves transmitted from the transceiver 21 may be referred to as transmitted waves, and ultrasonic waves generated when the transmitted waves are reflected by an object may be referred to as reflected waves.

[0018] 1, four transceivers 21A to 21D are arranged at the front end of the vehicle body 2, four transceivers 21E to 21H are arranged at the rear end, two transceivers 21I and 21J are arranged on the right side, and two transceivers 21K and 21L are arranged on the left side. Note that the number and installation positions of the transceivers 21 are not limited to this example.

[0019] 2 is a diagram showing an example of the configuration of a vehicle control system 50 according to an embodiment. The vehicle control system 50 performs processing for controlling the vehicle 1 based on information output from the object detection device 200. The vehicle control system 50 according to this embodiment includes an ECU 100 and the object detection device 200.

[0020] The object detection device 200 includes a plurality of transmitter / receivers 21 and a control unit 220. Each transmitter / receiver 21 includes a vibrator 211 configured using a piezoelectric element or the like, an amplifier, etc., and realizes transmission and reception of ultrasonic waves by the vibration of the vibrator 211. Specifically, each transmitter / receiver 21 transmits ultrasonic waves generated in response to the vibration of the vibrator 211 as a transmission wave, and detects the vibration of the vibrator 211 caused by a wave reflected from the transmission wave by an object such as an obstacle O or the road surface. The vibration of the vibrator 211 is converted into an electrical signal, and based on the electrical signal, it is possible to obtain, for example, a time of flight (TOF) corresponding to the distance from the transmitter / receiver 21 to the obstacle O and Doppler shift information corresponding to the relative speed between the vehicle 1 and the obstacle O.

[0021] 2 illustrates a configuration in which both transmission of the transmission wave and reception of the reflected wave are performed using a single oscillator 211, but the configuration of the transmitter / receiver 21 is not limited to this. For example, the transmitter and receiver may be separated, such as a configuration in which an oscillator for transmitting the transmission wave and an oscillator for receiving the reflected wave are separately provided.

[0022] The control unit 220 includes an input / output device 221, a storage device 222, and a processor 223. The input / output device 221 is an interface device that enables transmission and reception of information between the control unit 220 and external devices (such as the transceiver unit 21 and the ECU 100). The storage device 222 includes a main storage device such as a read-only memory (ROM) or a random access memory (RAM), and an auxiliary storage device such as a hard disk drive (HDD) or a solid state drive (SSD). The processor 223 is an integrated circuit that executes various processes to realize the functions of the control unit 220, and may be configured using, for example, a central processing unit (CPU), an application specific integrated circuit (ASIC), a field programmable gate array (FPGA), or the like that operates according to a program. The processor 223 executes various arithmetic and control processes by reading and executing programs stored in the storage device 222.

[0023] The ECU 100 is a unit that executes various processes for controlling the vehicle 1 based on information acquired from the object detection device 200 and the like. The ECU 100 includes an input / output device 110, a storage device 120, and a processor 130. The input / output device 110 is an interface device that enables transmission and reception of information between the ECU 100 and external mechanisms (such as the object detection device 200, drive mechanism, braking mechanism, steering mechanism, transmission mechanism, in-vehicle display, speakers, and various sensors). The storage device 120 includes a main storage device such as a ROM or RAM, and an auxiliary storage device such as an HDD or SSD. The processor 130 is an integrated circuit that executes various processes for realizing the functions of the ECU 100, and may be configured using, for example, a CPU, an ASIC, an FPGA, or the like. The processor 130 reads programs stored in the storage device 120 and executes various arithmetic and control processes.

[0024] Fig. 3 is a diagram showing an example of a distance calculation method using the TOF method. Fig. 3 illustrates an envelope L11 (echo information) that indicates a change over time in the intensity (signal level) of the ultrasonic waves transmitted and received by the transmitting and receiving unit 21. In the graph shown in Fig. 3, the horizontal axis corresponds to time (TOF), and the vertical axis corresponds to the intensity of the ultrasonic waves transmitted and received by the transmitting and receiving unit 21 (the magnitude of vibration of the transducer 211).

[0025] Envelope L11 shows the change over time in intensity, which indicates the magnitude of vibration of oscillator 211. From envelope L11 shown in Fig. 3, it can be seen that oscillator 211 is driven to vibrate for time Ta from time t0, completing transmission of the transmission wave at time t1, and then the vibration of oscillator 211 due to inertia continues while attenuating for time Tb until time t2. Therefore, in the graph shown in Fig. 3, time Tb corresponds to the so-called reverberation time.

[0026] The envelope L11 reaches a peak at time t4, which is a time Tp after time t0 when the transmission of the transmission wave starts, at which time the magnitude of the vibration of the vibrator 211 reaches or exceeds the detection threshold Ith. This detection threshold Ith is a value set to distinguish whether the vibration of the vibrator 211 is caused by the reception of a reflected wave from an obstacle O (another vehicle, a structure, a pedestrian, etc.) or by the reception of a reflected wave from an object other than the obstacle O (for example, the road surface, etc.). Note that although the detection threshold Ith is shown as a constant value here, the detection threshold Ith may also be a variable value that changes depending on the situation. Vibrations having a peak equal to or greater than the detection threshold Ith can be considered to be caused by the reception of a reflected wave from the obstacle O.

[0027] The envelope L11 in this example shows that the vibration of the vibrator 211 attenuates after timing t4. Therefore, timing t4 corresponds to the timing at which reception of the reflected wave from the obstacle O is completed, in other words, the timing at which the transmission wave last transmitted at timing t1 returns as a reflected wave.

[0028] Furthermore, in envelope L11, timing t3, which is the start point of the peak at timing t4, corresponds to the timing when reception of the reflected wave from obstacle O begins, in other words, the timing when the transmitted wave first transmitted at timing t0 returns as a reflected wave. Therefore, the time ΔT between timing t3 and timing t4 is equal to the time Ta, which is the transmission time of the transmitted wave.

[0029] From the above, in order to use TOF to find the distance from the transmitter / receiver unit 21, which is the source of the ultrasonic waves, to the obstacle O, it is necessary to find the time Tf between the time t0 when the transmission of the transmitted wave begins and the time t3 when the reflected wave begins to be received. This time Tf can be found by subtracting the time ΔT, which is equal to the time Ta as the transmission time of the transmitted wave, from the time Tp, which is the difference between the time t0 and the time t4 when the intensity of the reflected wave exceeds the detection threshold Ith and reaches its peak.

[0030] The time t0 when the transmission wave starts to be transmitted can be easily identified as the time when the object detection device 200 starts to operate, and the time Ta as the transmission time of the transmission wave is determined in advance by settings, etc. Therefore, by identifying the time t4 when the intensity of the reflected wave reaches a peak equal to or exceeds the detection threshold Ith, the distance from the vehicle 1 (the transmitter / receiver 21, which is the source of the ultrasonic wave transmission and reception) to the obstacle O can be calculated.

[0031] The above calculation method is merely an example, and the distance from the vehicle 1 to the obstacle O may be calculated using any known or new method as appropriate.

[0032] FIG. 4 is a diagram showing an example of the functional configuration of object detection device 200 according to the embodiment. Object detection device 200 according to the present embodiment includes a calculation unit 301. The calculation unit 301 includes a direct wave distance calculation unit 311, an indirect wave distance calculation unit 312, a correction unit 313, and a trilateration calculation unit 314. These functional units can be realized, for example, by cooperation between hardware and software (programs, etc.) of object detection device 200 as shown in FIG. 2. Furthermore, at least some of these functional units may be realized by dedicated hardware (circuits).

[0033] The calculation unit 301 calculates the obstacle distance, which is the distance from the vehicle 1 to the obstacle O, based on the timing of transmission and reception of ultrasonic waves by each transceiver unit 21. The reflected waves received by each transceiver unit 21 according to this embodiment include direct waves and indirect waves. A direct wave is a reflected wave corresponding to a transmission wave transmitted from a certain transceiver unit 21 (e.g., transceiver unit 21A) and received by the same transceiver unit 21 (e.g., transceiver unit 21A) as the transceiver unit 21 that transmitted the transmission wave. An indirect wave is a reflected wave corresponding to a transmission wave transmitted from a certain transceiver unit 21 (e.g., transceiver unit 21A) and received by a transceiver unit 21 (e.g., transceiver unit 21B) different from the transceiver unit 21 that transmitted the transmission wave. The calculation unit 301 according to this embodiment calculates the obstacle distance using both the reception timing of the direct wave and the reception timing of the indirect wave.

[0034] The calculation unit 301 according to this embodiment includes a direct wave distance calculation unit 311 , an indirect wave distance calculation unit 312 , a correction unit 313 , and a trilateration calculation unit 314 .

[0035] When a reflected wave of a transmission wave transmitted from a first transceiver unit (e.g., 21A) that is one of the multiple transceivers 21 is received by the first transceiver unit, the direct wave distance calculation unit 311 calculates a first direct wave distance based on the timing at which the transmission wave was transmitted from the first transceiver unit and the timing at which the reflected wave (direct wave) of the transmission wave was received by the first transceiver unit. Also, when a reflected wave of a transmission wave transmitted from a second transceiver unit (e.g., 21B) different from the first transceiver unit is received by the second transceiver unit, the direct wave distance calculation unit 311 calculates a second direct wave distance based on the timing at which the transmission wave was transmitted from the second transceiver unit and the timing at which the reflected wave (direct wave) of the transmission wave was received by the second transceiver unit. That is, the first direct wave distance is calculated based on the direct wave received by the first transceiver unit, and the second direct wave distance is calculated based on the direct wave received by the second transceiver unit.

[0036] When a reflected wave of a transmission wave transmitted from a third transceiver unit (e.g., 21A) that is one of the multiple transceivers 21 is received by a fourth transceiver unit (e.g., 21B) different from the third transceiver unit, the indirect wave distance calculation unit 312 calculates a first indirect wave distance based on the timing at which the transmission wave was transmitted from the third transceiver unit and the timing at which the reflected wave (indirect wave) of the transmission wave was received by the fourth transceiver unit. Also, when a reflected wave of a transmission wave transmitted from the fourth transceiver unit is received by the third transceiver unit, the indirect wave distance calculation unit 312 calculates a second indirect wave distance based on the timing at which the transmission wave was transmitted from the fourth transceiver unit and the timing at which the reflected wave (indirect wave) of the transmission wave was received by the third transceiver unit. That is, the first indirect wave distance is calculated based on the indirect wave transmitted from the third transceiver unit and received by the fourth transceiver unit, and the second direct wave distance is calculated based on the indirect wave transmitted from the fourth transceiver unit and received by the third transceiver unit.

[0037] The correction unit 313 corrects the first direct wave distance and the second direct wave distance and the second direct wave distance and the second indirect wave distance based on the relative speed between the vehicle 1 and the obstacle O.

[0038] The trilateration calculation unit 314 calculates the obstacle distance by trilateration based on the corrected first direct wave distance and the corrected second direct wave distance. The trilateration calculation unit 314 also calculates the obstacle distance by trilateration based on the corrected first indirect wave distance and the corrected second indirect wave distance. The obstacle distance calculated by the trilateration calculation unit 314 is output to the ECU 100, etc., and is used for various vehicle controls, etc.

[0039] According to the above configuration, when direct waves are detected by the two transmitting / receiving units 21, two direct wave distances are calculated based on the direct waves, these direct wave distances are corrected based on the relative velocity, and the obstacle distance is calculated by trilateration based on the corrected direct wave distances. Also, when indirect waves are detected by the two transmitting / receiving units 21, two indirect wave distances are calculated based on the indirect waves, these indirect wave distances are corrected based on the relative velocity, and the obstacle distance is calculated by trilateration based on the corrected indirect wave distances. As a result, even if only direct waves or indirect waves are detected, obstacles can be detected with high accuracy by trilateration.

[0040] Fig. 5 is a diagram showing an example of a first direct wave distance Dd1 and a second direct wave distance Dd2 according to the embodiment. Fig. 5 illustrates a situation in which two transceivers 21G and 21H installed at the rear of the vehicle 1 are designated as a first transceiver and a second transceiver, respectively, and an obstacle O is present behind the vehicle 1. Fig. 5 also illustrates a first transmission wave Wt1 transmitted from the first transceiver 21G and a first direct wave Wd1 that is the first transmission wave Wt1 reflected by the obstacle O and received by the first transceiver 21G. Fig. 5 also illustrates a second transmission wave Wt2 transmitted from the second transceiver 21H and a second direct wave Wd2 that is the second transmission wave Wt2 reflected by the obstacle O and received by the second transceiver 21H.

[0041] The first direct wave distance Dd1 is calculated based on the timing when the first transmission wave Wt1 is transmitted from the first transceiver 21G and the timing when the first direct wave Wd1 is received by the first transceiver 21G. The second direct wave distance Dd2 is calculated based on the timing when the second transmission wave Wt2 is transmitted from the second transceiver 21H and the timing when the second direct wave Wd2 is received by the second transceiver 21H.

[0042] 6 is a diagram illustrating an example of the corrected first direct wave distance Dd1′ and the corrected second direct wave distance Dd2′ according to the embodiment. In FIG. 6, the corrected first direct wave distance Dd1′ and the corrected second direct wave distance Dd2′ are illustrated when the vehicle 1 is gradually moving backward.

[0043] The corrected first direct wave distance Dd1' illustrated here is calculated by subtracting a distance change amount ΔD1 based on the relative speed between the vehicle 1 and the obstacle O from the first direct wave distance Dd1 calculated as described above. The corrected second direct wave distance Dd2' is calculated by subtracting a distance change amount ΔD2 based on the relative speed between the vehicle 1 and the obstacle O from the second direct wave distance Dd2 calculated as described above. The relative speed may be calculated using any appropriate method. For example, the relative speed may be calculated based on the Doppler shift between the first transmission wave Wt1 and the first direct wave Wd1 and the Doppler shift between the second transmission wave Wt2 and the second direct wave Wd2. Multiplying the calculated relative speed by a predetermined time allows estimation of virtual positions P1 and P2 of the obstacle O after the predetermined time has elapsed, and distance changes ΔD1 and ΔD2 can be calculated based on the current position of the obstacle O and the virtual positions P1 and P2. In addition, when the vehicle 1 is moving forward, the value obtained by adding the distance change amount ΔD1 to the first direct wave distance Dd1 before correction becomes the first direct wave distance Dd1' after correction, and the value obtained by adding the distance change amount ΔD2 to the second direct wave distance Dd2 before correction becomes the second direct wave distance Dd2' after correction.

[0044] Then, the obstacle distance is calculated by trilateration calculation based on the corrected first direct wave distance Dd1', the corrected second direct wave distance Dd2', and the installation distance D0 between the first transceiver 21G and the second transceiver 21H.

[0045] Fig. 7 is a diagram showing an example of a first indirect wave distance Di1 and a second indirect wave distance Di2 according to the embodiment. Fig. 7 illustrates a situation in which two transceivers 21G and 21H installed at the rear of the vehicle 1 are respectively a third transceiver and a fourth transceiver, and an obstacle O is present behind the vehicle 1. Note that, here, a case is illustrated in which the first transceiver and the third transceiver are the same transceiver 21G, and the second transceiver and the fourth transceiver are the same transceiver 21H, but the present invention is not limited to this.

[0046] 7 illustrates a situation in which the fourth transceiver 21H receives the first indirect wave Wi1 and the third transceiver 21G receives the second indirect wave Wi2. The first indirect wave Wi1 is a reflected wave generated when the first transmission wave Wt1 transmitted from the third transceiver 21G is reflected by an obstacle O. The second indirect wave Wi2 is a reflected wave generated when the second transmission wave Wt2 transmitted from the fourth transceiver 21H is reflected by the obstacle O.

[0047] The first indirect wave distance Di1 is calculated based on the timing when the third transmission wave Wt1 is transmitted from the first transceiver 21G and the timing when the first indirect wave Wi1 is received by the fourth transceiver 21H. The second indirect wave distance Di2 is calculated based on the timing when the second transmission wave Wt2 is transmitted from the fourth transceiver 21H and the timing when the second indirect wave Wi2 is received by the third transceiver 21G.

[0048] 8 is a diagram illustrating an example of the corrected first indirect wave distance Di1' and the corrected second indirect wave distance Di2' according to the embodiment. Similar to FIG. 6, FIG. 8 illustrates the corrected first indirect wave distance Di1' and the corrected second indirect wave distance Di2' when the vehicle 1 is gradually moving backward.

[0049] The corrected first indirect wave distance Di1' illustrated here is calculated by subtracting the distance change amount ΔD1 based on the relative speed between the vehicle 1 and the obstacle O from the first indirect wave distance Di1 calculated as described above. The corrected second indirect wave distance Di2' is calculated by subtracting the distance change amount ΔD2 based on the relative speed between the vehicle 1 and the obstacle O from the second indirect wave distance Di2 calculated as described above. Then, as described above, the virtual positions P1, P2 of the obstacle O after the lapse of the predetermined time can be estimated by multiplying the calculated relative speed by a predetermined time, and the distance change amounts ΔD1, ΔD2 can be calculated based on the current position of the obstacle O and the virtual positions P1, P2. When the vehicle 1 is moving forward, the value obtained by adding the distance change amount ΔD1 to the first indirect wave distance Di1 before correction becomes the corrected first indirect wave distance Di1', and the value obtained by adding the distance change amount ΔD2 to the second indirect wave distance Di2 before correction becomes the corrected second indirect wave distance Di2'.

[0050] Then, the obstacle distance is calculated by trilateration calculation based on the corrected first indirect wave distance Di1', the corrected second indirect wave distance Di2', and the installation distance D0.

[0051] 9 is a flowchart showing an example of processing in the object detection device 200 according to the embodiment. First, the direct wave distance calculation unit 311 determines whether or not the two transmission / reception units 21 have received the direct waves Wd1 and Wd2, respectively (S101). The determination of whether or not the direct waves Wd1 and Wd2 have been received may be realized by appropriately using publicly known or new technology, and may be realized, for example, by adjusting the detection cycle of each transmission / reception unit 21 (the period from transmitting a transmission wave once to waiting for reception of a reflected wave).

[0052] If the two transmitter / receivers 21 receive direct waves Wd1 and Wd2, respectively (S101: Yes), the direct wave distance calculation unit 311 calculates the first direct wave distance Dd1 and the second direct wave distance Dd2 for each of the two transmitter / receivers 21 based on the timing at which the transmission waves Wt1 and Wt2 were transmitted and the timing at which the direct waves Wd1 and Wd2 were received (S102).

[0053] Thereafter, the correction unit 313 corrects the first direct wave distance Dd1 and the second direct wave distance Dd2 based on the relative speed between the vehicle 1 and the obstacle O (S103), and the trilateration calculation unit 314 calculates the obstacle distance by trilateration based on the corrected first direct wave distance Dd1' and the corrected second direct wave distance Dd2' (S104).The calculated obstacle distance is then output to the ECU 100, etc. (S105).

[0054] On the other hand, if the two transceivers 21 have not received the direct waves Wd1 and Wd2 (S101: No), the indirect wave distance calculation unit 312 determines whether the two transceivers 21 have received the indirect waves Wi1 and Wi2 (S106). The determination of whether the indirect waves Wi1 and Wi2 have been received may be realized by appropriately using publicly known or new technology, and may be realized, for example, by adjusting the detection cycle of each transceiver 21.

[0055] If the two transmitting / receiving units 21 have not received the indirect waves Wi1 and Wi2, respectively (S106: No), this routine ends. If the two transmitting / receiving units 21 have received the indirect waves Wi1 and Wi2, respectively (S106: Yes), the indirect wave distance calculation unit 312 calculates the first indirect wave distance Di1 and the second indirect wave distance Di2 for each of the two transmitting / receiving units 21 based on the timing at which the transmission waves Wt1 and Wt2 were transmitted and the timing at which the indirect waves Wt1 and Wt2 were received (S107).

[0056] Thereafter, the correction unit 313 corrects the first indirect wave distance Di1 and the second indirect wave distance Di2 based on the relative speed between the vehicle 1 and the obstacle O (S108), and the trilateration calculation unit 314 calculates the obstacle distance by trilateration based on the corrected first indirect wave distance Di1' and the corrected second indirect wave distance Di2' (S109).Then, the calculated obstacle distance is output to the ECU 100, etc. (S105).

[0057] The obstacle distance calculated as described above may contain noise. The obstacle distance may be used for vehicle control such as brake control in ECU 100, so high reliability is required. Therefore, the calculation unit 301 according to this embodiment has a function for improving the reliability of the obstacle distance to be output.

[0058] The calculation unit 301 (trilateration calculation unit 314) determines whether the current obstacle distance calculated as described above is equal to or less than a threshold value (S201), and if the current obstacle distance is not equal to or less than the threshold value (S201: No), discards (does not output) the current obstacle distance (S204). The threshold value should be set appropriately depending on the specifications of the vehicle control system 50, and may be, for example, an upper limit distance that is determined to provide substantially sufficient accuracy based on prior verification. The threshold value may be a fixed value or may be a value that varies depending on predetermined conditions.

[0059] If the current obstacle distance is equal to or less than the threshold (S201: Yes), the calculation unit 301 determines whether the difference between the current obstacle distance and the previous obstacle distance is equal to or less than the threshold (S202). The previous obstacle distance is, for example, the obstacle distance calculated based on the direct wave or indirect wave detected in the previous detection cycle. If the difference is not equal to or less than the threshold (S202: No), the current obstacle distance is discarded (S204). If the difference is equal to or less than the threshold (S202: Yes), the current obstacle distance is output to the ECU 100, etc. (S203). This allows the obstacle distance that changes by more than the threshold in a short period of time to be discarded as noise.

[0060] By the above-described processing, only the obstacle distance with high reliability can be output to the ECU 100 or the like.

[0061] As described above, according to this embodiment, when direct waves are detected by the two transmitting / receiving units 21, two direct wave distances are calculated based on the direct waves, these direct wave distances are corrected based on the relative velocity, and the obstacle distance is calculated by trilateration based on the corrected direct wave distances. Also, when indirect waves are detected by the two transmitting / receiving units 21, two indirect wave distances are calculated based on the indirect waves, these indirect wave distances are corrected based on the relative velocity, and the obstacle distance is calculated by trilateration based on the corrected indirect wave distances. As a result, even when only direct waves or indirect waves are detected, obstacles can be detected with high accuracy by trilateration.

[0062] A program that causes a computer (such as processor 223) to execute processing for realizing the functions of object detection device 200 can be provided by being recorded in an installable or executable file format on a computer-readable recording medium such as a CD (Compact Disc)-ROM, a flexible disk (FD), a CD-R (Recordable), or a DVD (Digital Versatile Disk). The program may also be provided or distributed via a network such as the Internet.

[0063] Although the embodiments of the present disclosure have been described above, the above-described embodiments and their modifications are merely examples and are not intended to limit the scope of the invention. The novel embodiments and modifications described above can be implemented in various forms, and various omissions, substitutions, and modifications can be made without departing from the spirit of the invention. The above-described embodiments and modifications are included within the scope and spirit of the invention, and are also included in the inventions and their equivalents as defined in the claims. [Explanation of symbols]

[0064] 1...vehicle, 2...vehicle body, 21, 21A to 21L...transmitter / receiver unit, 50...vehicle control system, 100...ECU, 200...object detection device, 211...transducer, 220...control unit, 221...input / output device, 222...storage device, 223...processor, 301...calculation unit, 311...direct wave distance calculation unit, 312...indirect wave distance calculation unit, 313...correction unit, 314...trilateration calculation unit, D0...installation distance, Dd1...first direct wave distance , Dd1'...corrected first direct wave distance, Dd2...second direct wave distance, Dd2'...corrected second direct wave distance, Di1...first indirect wave distance, Di2...second indirect wave distance, Di1'...corrected first indirect wave distance, Di2'...corrected second indirect wave distance, Wd1...first direct wave, Wd2...second direct wave, Wt1...first transmitted wave, Wt2...second transmitted wave, O...obstacle, P1, P2...virtual position, ΔD1, ΔD2...distance change amount

Claims

1. An object detection device mounted on a moving body and detecting an obstacle present around the moving body, a plurality of transmitting and receiving units for transmitting and receiving ultrasonic waves; a calculation unit that calculates an obstacle distance, which is the distance from the moving object to the obstacle, based on the timing of transmission and reception of ultrasonic waves by each of the transmission and reception units; Equipped with The calculation unit When a reflected wave of a transmission wave transmitted from a first transceiver unit that is one of the plurality of transceivers is received by the first transceiver unit, and a reflected wave of a transmission wave transmitted from a second transceiver unit different from the first transceiver unit is received by the second transceiver unit, the method calculates a first direct wave distance based on the timing at which the transmission wave was transmitted from the first transceiver unit and the timing at which the reflected wave of the transmission wave was received by the first transceiver unit, and a second direct wave distance based on the timing at which the transmission wave was transmitted from the second transceiver unit and the timing at which the reflected wave of the transmission wave was received by the second transceiver unit, corrects the first direct wave distance and the second direct wave distance based on the relative speed between the moving body and the obstacle, and calculates the obstacle distance by trilateration based on the corrected first direct wave distance and the corrected second direct wave distance, when a reflected wave of a transmission wave transmitted from a third transceiver that is one of the plurality of transceivers is received by a fourth transceiver that is different from the third transceiver, and the reflected wave of the transmission wave transmitted from the fourth transceiver is received by the third transceiver; calculating a first indirect wave distance based on a timing at which the transmission wave was transmitted from the third transceiver and a timing at which the reflected wave of the transmission wave was received by the fourth transceiver, and a second indirect wave distance based on a timing at which the transmission wave was transmitted from the fourth transceiver and a timing at which the reflected wave of the transmission wave was received by the third transceiver; correcting the first indirect wave distance and the second indirect wave distance based on the relative velocity; and calculating the obstacle distance by trilateration based on the corrected first indirect wave distance and the corrected second indirect wave distance; Object detection device.

2. The relative velocity is calculated based on a Doppler shift between a frequency of the transmitted wave and a frequency of the reflected wave corresponding to the transmitted wave. The object detection device according to claim 1 .

3. When the obstacle distance calculated by the trilateration is greater than a predetermined threshold, the calculation unit discards the obstacle distance. The object detection device according to claim 1 .

4. the calculation unit discards the current obstacle distance when a difference between the current obstacle distance and a previous obstacle distance calculated a predetermined time before the current obstacle distance is calculated is greater than a predetermined threshold value; The object detection device according to claim 1 .

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