Object detection device

Abstract

To improve the accuracy of the object-position estimation.SOLUTION: An object detection device according to an embodiment, which is an object detection device that is mounted on a moving body and detects an object present around the moving body; a plurality of transmission and reception units that transmit and receive ultrasonic waves; a calculation unit that calculates an object distance, which is a distance from the moving body to the object, based on a timing of transmission and reception of ultrasonic waves in each of the transmission and reception units. The calculation unit calculates a temporary distance from the moving body to the object, based on a timing of transmission and reception of ultrasonic waves in each pair of transmission and reception units of a plurality of pairs of transmission and reception units among the plurality of transmission and reception units; and determines the object distance, based on a plurality of temporary distances.SELECTED DRAWING: Figure 4

Description

[Technical Field]

[0001] The present invention relates to an object detection device. [Background technology]

[0002] In an object detection device that uses ultrasonic waves to detect obstacles present around a vehicle, a technology is used 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 ultrasonic waves by each transceiver. In such a configuration with multiple transceivers, the reflected waves received by each transceiver (ultrasonic waves generated when ultrasonic waves transmitted from the transceiver (transmission waves) are reflected by an object) include direct waves and indirect waves.

[0003] A direct wave is a reflected wave corresponding to a transmitted wave transmitted from a certain transceiver unit and received by the same transceiver unit that transmitted the transmitted wave. An indirect wave is a reflected wave corresponding to a transmitted wave transmitted from a certain transceiver unit and received by a transceiver unit different from the transceiver unit that transmitted the transmitted wave.

[0004] As a technology that utilizes such direct waves and indirect waves, a technology has been disclosed that estimates the distance to an obstacle by combining a distance calculated based on direct waves and a distance calculated based on indirect waves (see, for example, Patent Document 1). [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Application Laid-Open No. 2016-085041 Summary of the Invention [Problem to be solved by the invention]

[0006] However, in conventional technology, the distance to an object such as an obstacle is estimated using a single method, so the reliability of the estimated distance to the object may be low, which may result in a decrease in the accuracy of estimating the object's position.

[0007] One of the problems to be solved by the embodiments of the present invention is to provide an object detection device that can improve the accuracy of estimating the position of an object. [Means for solving the problem]

[0008] An object detection device according to an embodiment of the present invention is an object detection device mounted on a moving body and detects objects present in the vicinity of the moving body, and comprises a plurality of transmitter-receivers that transmit and receive ultrasonic waves, and a calculation unit that calculates an object distance, which is the distance from the moving body to the object, based on the timing of transmission and reception of ultrasonic waves at each of the transmitter-receivers, and the calculation unit calculates a hypothetical distance from the moving body to the object based on the timing of transmission and reception of ultrasonic waves at each of a plurality of pairs of transmitter-receivers among the plurality of transmitter-receivers, and determines the object distance based on the plurality of hypothetical distances. [Effects of the Invention]

[0009] According to an object detection device according to an embodiment of the present invention, for example, it is possible to improve the accuracy of estimating the position of an object. [Brief explanation of the drawings]

[0010] [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 flowchart illustrating an example of the object detection process according to the embodiment. [Figure 8] FIG. 8 is a flowchart illustrating an example of an obstacle distance calculation process according to the embodiment. [Figure 9] FIG. 9 is a flowchart showing an example of processing when outputting an obstacle distance according to the embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0011] 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.

[0012] 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.

[0013] 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.

[0014] 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.

[0015] 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.

[0016] 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.

[0017] 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.

[0018] 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.

[0019] 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.

[0020] 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).

[0021] 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.

[0022] 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.

[0023] 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.

[0024] 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.

[0025] 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.

[0026] 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.

[0027] 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.

[0028] 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 three direct wave distance calculation units 311A to 311C, three correction units 313A to 313C, three trilateration calculation units 314A to 314C, and one obstacle distance determination unit 315. 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).

[0029] 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 transmission / reception unit 21. The reflected waves received by each transmission / reception unit 21 in this embodiment include direct waves and indirect waves. A direct wave is a reflected wave corresponding to a transmission wave transmitted from a certain transmission / reception unit 21 (e.g., transmission / reception unit 21A) and received by the same transmission / reception unit 21 (e.g., transmission / reception unit 21A) as the transmission / reception unit 21 that transmitted the transmission wave. An indirect wave is a reflected wave corresponding to a transmission wave transmitted from a certain transmission / reception unit 21 (e.g., transmission / reception unit 21A) and received by a transmission / reception unit 21 (e.g., transmission / reception unit 21B) different from the transmission / reception unit 21 that transmitted the transmission wave. The calculation unit 301 in this embodiment calculates the obstacle distance using the reception timing of the direct wave.

[0030] The direct wave distance calculation unit 311A, the correction unit 313A, and the trilateration calculation unit 314A calculate the distance to the obstacle from the direct wave corresponding to the transmission wave from the transceiver unit 21B on the right side of the front end (sometimes referred to as the front) of the vehicle 1 and the direct wave corresponding to the transmission wave from the transceiver unit 21A at the right corner that curves from the front end to the right side (sometimes referred to as the right side). This distance is referred to as the first distance. The direct wave distance calculation unit 311A, the correction unit 313A, and the trilateration calculation unit 314A also calculate the distance to the obstacle (first distance) from the direct wave corresponding to the transmission wave from the transceiver unit 21C on the left side of the front end and the direct wave corresponding to the transmission wave from the transceiver unit 21D at the left corner that curves from the left side of the front end to the left side (sometimes referred to as the left side).

[0031] The direct wave distance calculation unit 311B, the correction unit 313B, and the trilateration calculation unit 314B calculate the distance from the direct waves of the transmission waves from the transceiver units 21I and 21J on the right side of the vehicle 1 to the obstacle. This distance is referred to as the second distance. The direct wave distance calculation unit 311B, the correction unit 313B, and the trilateration calculation unit 314B also calculate the distance (second distance) from the direct waves of the transmission waves from the transceiver units 21K and 21L on the left side of the vehicle 1 to the obstacle.

[0032] The direct wave distance calculation unit 311C, correction unit 313C, and trilateration calculation unit 314C calculate the distance to the obstacle from the direct wave corresponding to the transmission wave from the transceiver unit 21A at the right corner of the vehicle 1 and the direct wave corresponding to the transmission wave from the transceiver unit 21I on the right side of the vehicle 1. This distance is referred to as the third distance. The direct wave distance calculation unit 311C, correction unit 313C, and trilateration calculation unit 314C also calculate the distance to the obstacle (third distance) from the direct wave corresponding to the transmission wave from the transceiver unit 21D at the left corner of the vehicle 1 and the direct wave corresponding to the transmission wave from the transceiver unit 21K on the left side of the vehicle 1. Here, the first distance, the second distance, and the third distance are examples of provisional distances. That is, the first distance, the second distance, and the third distance are all distances from the vehicle 1 to the obstacle, but are not the finally determined obstacle distances, and are referred to as provisional distances or tentative obstacle distances.

[0033] Here, when there is no need to distinguish between the direct wave distance calculation units 311A to 311C, they are referred to as direct wave distance calculation units 311. When there is no need to distinguish between the correction units 313A to 313C, they are referred to as correction units 313. When there is no need to distinguish between the trilateration calculation units 314A to 314C, they are referred to as trilateration calculation units 314.

[0034] When a reflected wave of a transmission wave transmitted from the transceiver 21B on the front right side, which is one of the multiple transceivers 21, is received by the transceiver 21B, the direct wave distance calculation unit 311A calculates a first direct wave distance based on the timing at which the transmission wave was transmitted from the transceiver 21B and the timing at which the reflected wave (direct wave) of the transmission wave was received by the transceiver 21B. When a reflected wave of a transmission wave transmitted from the transceiver 21A on the right corner is received by the transceiver 21A, the direct wave distance calculation unit 311A calculates a second direct wave distance based on the timing at which the transmission wave was transmitted from the transceiver 21A and the timing at which the reflected wave (direct wave) of the transmission wave was received by the transceiver 21A.

[0035] That is, the first direct wave distance is calculated based on the direct wave received by the transceiver 21B, and the second direct wave distance is calculated based on the direct wave received by the transceiver 21A. Here, the transceiver 21B and the transceiver 21A are an example of a first pair of transceivers.

[0036] Direct wave distance calculation unit 311A similarly calculates the first direct wave distance and the second direct wave distance, using transceiver unit 21C on the left side of the front end and transceiver unit 21D at the left corner as a pair of transceivers.

[0037] When a reflected wave of a transmission wave transmitted from a transmission / reception unit 21I on the right side surface, which is one of the multiple transmission / reception units 21, is received by the transmission / reception unit 21I, the direct wave distance calculation unit 311B calculates a first direct wave distance based on the timing at which the transmission wave was transmitted from the transmission / reception unit 21I and the timing at which the reflected wave (direct wave) of the transmission wave was received by the transmission / reception unit 21I. Also, when a reflected wave of a transmission wave transmitted from another transmission / reception unit 21J on the right side surface is received by the transmission / reception unit 21J, the direct wave distance calculation unit 311B calculates a second direct wave distance based on the timing at which the transmission wave was transmitted from the transmission / reception unit 21J and the timing at which the reflected wave (direct wave) of the transmission wave was received by the transmission / reception unit 21J.

[0038] That is, the first direct wave distance is calculated based on the direct wave received by the transceiver 21I, and the second direct wave distance is calculated based on the direct wave received by the transceiver 21J. Here, the transceiver 21I and the transceiver 21J are an example of a second pair of transceivers.

[0039] Direct wave distance calculation unit 311B similarly calculates the first direct wave distance and the second direct wave distance, using transceiver units 21K and 21L on the left side surface as a pair of transceivers.

[0040] When a reflected wave of a transmission wave transmitted from the transceiver 21A at the right corner, which is one of the multiple transceivers 21, is received by the transceiver 21A, the direct wave distance calculation unit 311C calculates a first direct wave distance based on the timing at which the transmission wave was transmitted from the transceiver 21A and the timing at which the reflected wave (direct wave) of the transmission wave was received by the transceiver 21A. Also, when a reflected wave of a transmission wave transmitted from the transceiver 21I at the right side is received by the transceiver 21I, the direct wave distance calculation unit 311C calculates a second direct wave distance based on the timing at which the transmission wave was transmitted from the transceiver 21I and the timing at which the reflected wave (direct wave) of the transmission wave was received by the transceiver 21I.

[0041] That is, the first direct wave distance is calculated based on the direct wave received by the transceiver 21A, and the second direct wave distance is calculated based on the direct wave received by the transceiver 21I. Here, the transceiver 21A and the transceiver 21I are an example of a third pair of transceivers.

[0042] Direct wave distance calculation unit 311C similarly calculates the first direct wave distance and the second direct wave distance, using transceiver unit 21D at the left corner and transceiver unit 21K on the left side as a pair of transceivers.

[0043] Here, the frequencies of the transmission waves transmitted from the front end transceivers 21A, 21C and the corner transceivers 21A, 21D are different from the frequencies of the transmission waves transmitted from the side transceivers 21I, 21J, 21K, 21L.

[0044] The correction unit 313A corrects the first direct wave distance and the second direct wave distance calculated by the calculation unit 311A based on the relative speed between the vehicle 1 and the obstacle O. The correction unit 313B corrects the first direct wave distance and the second direct wave distance calculated by the calculation unit 311B based on the relative speed between the vehicle 1 and the obstacle O. The correction unit 313C corrects the first direct wave distance and the second direct wave distance calculated by the calculation unit 311C based on the relative speed between the vehicle 1 and the obstacle O.

[0045] The trilateration calculation unit 314A calculates a first distance as a provisional distance by trilateration based on the first direct wave distance and the second direct wave distance after correction by the correction unit 313A. The trilateration calculation unit 314B calculates a second distance as a provisional distance by trilateration based on the first direct wave distance and the second direct wave distance after correction by the correction unit 313B. The trilateration calculation unit 314C calculates a third distance as a provisional distance by trilateration based on the first direct wave distance and the second direct wave distance after correction by the correction unit 313C.

[0046] Fig. 5 is a diagram showing an example of the first direct wave distance Dd1 and the second direct wave distance Dd2 according to the embodiment. Fig. 5 illustrates a situation in which the transceiver unit 21B installed on the right side of the front end of the vehicle 1 and the transceiver unit 21A installed at the right corner are the first transceiver unit and the second transceiver unit, respectively, and an obstacle O is present in front of the vehicle 1. That is, the example in Fig. 5 illustrates an example in which the first distance is calculated by the direct wave distance calculation unit 311A, the correction unit 313A, and the trilateration calculation unit 314A.

[0047] 5 illustrates a first transmission wave Wt1 transmitted from the first transceiver 21B and a first direct wave Wd1 that is the first transmission wave Wt1 reflected by an obstacle O and received by the first transceiver 21B. Also illustrated are a second transmission wave Wt2 transmitted from the second transceiver 21A and a second direct wave Wd2 that is the second transmission wave Wt2 reflected by an obstacle O and received by the second transceiver 21A.

[0048] The first direct wave distance Dd1 is calculated based on the timing when the first transmission wave Wt1 is transmitted from the first transceiver 21B and the timing when the first direct wave Wd1 is received by the first transceiver 21B. The second direct wave distance Dd2 is calculated based on the timing when the second transmission wave Wt2 is transmitted from the second transceiver 21A and the timing when the second direct wave Wd2 is received by the second transceiver 21A.

[0049] 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.

[0050] 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 backward, 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.

[0051] Then, a provisional distance (i.e., the first 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 unit 21G and the second transceiver unit 21H.

[0052] The same procedure is used when the second distance is calculated by the direct wave distance calculation unit 311B, the correction unit 313B, and the trilateration calculation unit 314B, and when the third distance is calculated by the direct wave distance calculation unit 311C, the correction unit 313C, and the trilateration calculation unit 314C.

[0053] Returning to Figure 4, the obstacle distance determination unit 315 determines the obstacle distance between the vehicle 1 and the obstacle O based on the first distance calculated by the trilateration calculation unit 314A, the second distance calculated by the trilateration calculation unit 314B, and the third distance calculated by the trilateration calculation unit 314C.

[0054] Specifically, the obstacle distance determination unit 315 determines the obstacle distance by taking a weighted average of the first distance, the second distance, and the third distance. Here, the weights in the weighted average can be determined based on the positions of the pair of transceivers 21. For example, the third distance calculated using the transceiver 21B at the right corner and the transceiver 21B on the right side can be considered to have high accuracy, and the weight can be set higher than the weights for the first and second distances.

[0055] Moreover, the obstacle distance determination unit 315 may determine the first distance, the second distance, or the third distance that is correctly output as the obstacle distance.

[0056] The obstacle distance determined by the obstacle distance determination unit 315 is output to the ECU 100 and the like, and is used for various vehicle controls and the like.

[0057] The obstacle distance determination unit 315 also executes a reliability improvement process, which is a process of discarding the current obstacle distance if the 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.

[0058] Next, the object detection process according to this embodiment configured as above will be described. FIG. 7 is a flowchart illustrating an example of a procedure of the object detection process according to the embodiment. First, each of the multiple transmitter / receivers 21 transmits ultrasonic waves in a predetermined sequence (S101). Next, distance detection processing is performed in the direct wave distance calculation unit 311A, the correction unit 313A, and the trilateration calculation unit 314A (S102A). In parallel with this, distance detection processing is performed in the direct wave distance calculation unit 311B, the correction unit 313B, and the trilateration calculation unit 314B (S102B), and distance detection processing is performed in the direct wave distance calculation unit 311C, the correction unit 313C, and the trilateration calculation unit 314C (S102C).

[0059] 8 is a flowchart illustrating an example of a procedure for distance detection processing according to the embodiment. The procedure shown in FIG. 8 is common to the distance detection processing of S102A, S102B, and S102C.

[0060] First, the direct wave distance calculation unit 311 determines whether or not the direct waves Wd1 and Wd2 have been received by the two transmission / reception units 21 (S201). The determination of whether or not the direct waves Wd1 and Wd2 have been received may be realized by appropriately utilizing 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).

[0061] If the two transmitting / receiving units 21 are not receiving the direct waves Wd1 and Wd2 (S201: No), the process returns to the caller.

[0062] On the other hand, if the two transmitter / receivers 21 receive direct waves Wd1 and Wd2, respectively (S201: 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 (S202).

[0063] 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 (S203), and the trilateration calculation unit 314 calculates a provisional distance by trilateration based on the corrected first direct wave distance Dd1' and the corrected second direct wave distance Dd2' (S204). Then, the trilateration calculation unit 314 outputs the calculated provisional distance to the obstacle distance determination unit 315 (S205). Here, the provisional distance calculated by the trilateration calculation unit 314A is referred to as the first distance, the provisional distance calculated by the trilateration calculation unit 314B is referred to as the second distance, and the provisional distance calculated by the trilateration calculation unit 314A is referred to as the third distance, respectively.

[0064] Returning to Figure 7, next, the obstacle distance determination unit 315 determines the obstacle distance (S103), as described above, from the first distance calculated in the detection processing (S102A) by the direct wave distance calculation unit 311A, the correction unit 313A, and the trilateration calculation unit 314A, the second distance calculated in the detection processing (S102B) by the direct wave distance calculation unit 311B, the correction unit 313B, and the trilateration calculation unit 314B, and the third distance calculated in the detection processing (S102C) by the direct wave distance calculation unit 311C, the correction unit 313C, and the trilateration calculation unit 314C.

[0065] The obstacle distance calculated as described above may contain noise. The obstacle distance may be used for vehicle control, such as brake control, in the ECU 100, and therefore requires high reliability. Therefore, the obstacle distance determination unit 315 according to this embodiment executes a reliability improvement process to improve the reliability of the obstacle distance to be output (S104).

[0066] FIG. 9 is a flowchart illustrating an example of a procedure of the reliability improvement process according to the embodiment. The obstacle distance determination unit 315 determines whether the current obstacle distance calculated as described above is equal to or less than a threshold value (S301). If the current obstacle distance is not equal to or less than the threshold value (S301: No), the obstacle distance determination unit 315 discards (does not output) the current obstacle distance (S304). 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 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.

[0067] If the current obstacle distance is equal to or less than the threshold in S301 (S301: Yes), the obstacle distance determination unit 315 determines whether the difference between the current obstacle distance and the previous obstacle distance is equal to or less than the threshold (S302). 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 (S302: No), the obstacle distance determination unit 315 discards the current obstacle distance (S304).

[0068] On the other hand, if the difference is equal to or smaller than the threshold value in S302 (S302: Yes), the current obstacle distance is output to the ECU 100, etc. (S303). This allows the obstacle distance that changes more than the threshold value in a short period of time to be discarded as noise.

[0069] By the above-described processing, only the obstacle distance with high reliability can be output to the ECU 100, etc. Returning to Fig. 7, when the reliability improvement processing is completed, the processing ends.

[0070] According to this embodiment, the object detection device 200 includes a plurality of transmitter / receivers 21 that transmit and receive ultrasonic waves, and a calculation unit 201 that calculates the object distance, which is the distance from the vehicle 1 to the obstacle, based on the timing of transmission and reception of ultrasonic waves at each transmitter / receiver 21. The calculation unit 301 calculates a tentative distance from the vehicle 1 to the obstacle based on the timing of transmission and reception of ultrasonic waves at each pair of transmitter / receiver units 21 among the plurality of transmitter / receiver units 21, and determines the obstacle distance based on the plurality of tentative distances.

[0071] Therefore, according to this embodiment, the distance to an object such as an obstacle is estimated by a plurality of detection processes using a plurality of pairs of transmitting / receiving units 21, thereby improving the accuracy of estimating the position of the obstacle.

[0072] In addition, in this embodiment, when a reflected wave of a transmission wave transmitted from one of the multiple pairs of transmission / reception units 21 is received by that one transmission / reception unit, and a reflected wave of a transmission wave transmitted from the other transmission / reception unit 21 of the pair of transmission / reception units 21 is received by the other transmission / reception unit 21, the calculation unit 301 of the object detection device 200 calculates a first direct wave distance based on the timing when the transmission wave is transmitted from one transmission / reception unit 21 and the timing when the reflected wave of the transmission wave is received by the one transmission / reception unit 21, and a second direct wave distance based on the timing when the transmission wave is transmitted from the other transmission / reception unit 21 and the timing when the reflected wave of the transmission wave is received by the other transmission / reception unit 21, corrects the first direct wave distance and the second direct wave distance based on the relative speed between the vehicle 1 and the obstacle, and calculates a provisional distance by trilateration based on the corrected first direct wave distance and the corrected second direct wave distance. Therefore, in this embodiment, the obstacle distance is determined based on the direct wave, which can further improve the accuracy of estimating the obstacle position.

[0073] Furthermore, according to this embodiment, the calculation unit 301 of the object detection device 200 determines the object distance by taking a weighted average of multiple provisional distances. Therefore, according to this embodiment, weighting can be performed taking into account the reliability of each pair of the transmitter-receiver units 21, thereby further improving the accuracy of estimating the position of an obstacle.

[0074] Furthermore, according to this embodiment, the calculation unit 301 of the object detection device 200 determines the weight values in the weighted average based on the positions of the respective pairs of transmitter-receivers 21. Therefore, according to this embodiment, weighting can be performed taking into account the reliability based on the positions of the respective pairs of transmitter-receivers 21, thereby further improving the accuracy of estimating the position of an obstacle.

[0075] Furthermore, according to this embodiment, in the object detection device 200, the frequencies of the ultrasonic waves transmitted by at least some different pairs of the transceiver units 21 are different from each other among the multiple pairs of the transceiver units 21. Therefore, in this embodiment, each transceiver unit 21 can more reliably receive direct waves, thereby further improving the accuracy of estimating the position of an obstacle.

[0076] Furthermore, according to this embodiment, in the object detection device 200, of the multiple pairs of transceivers 21, one transceiver 21 of a first pair of transceivers 21 is provided at the front end of the vehicle 1, and the other transceiver 21 of the first pair of transceivers 21 is provided at a corner, a second pair of transceivers 21 of the multiple pairs of transceivers 21 is provided at a side portion, and of the multiple pairs of transceivers 21, one transceiver 21 of a third pair of transceivers 21 is provided at a corner, and the other transceiver 21 is provided at a side portion. Therefore, according to this embodiment, each pair of transceivers 21, which are located at different positions, is used for object detection, thereby further improving the accuracy of estimating the position of an obstacle.

[0077] In this embodiment, object detection is performed using three pairs of transceivers 21: a transceiver at the front end, a transceiver at a corner 21, two transceivers 21 at the side, and a transceiver at a corner 21 and a transceiver at a side 21, but this is not limitative. Transceivers 21 at any position can be used for object detection in this embodiment.

[0078] In this embodiment, three pairs of transceiver units 21 have been described as an example of the multiple pairs of transceiver units 21, but the number of pairs is not limited to this. For example, the object detection device 200 may be configured to perform object detection using two pairs of transceiver units 21 or four or more pairs of transceiver units 21.

[0079] In this embodiment, the calculation unit 301 determines the tentative distance to the obstacle using a direct wave, but if an indirect wave can be received, the calculation unit 301 may be configured to calculate the tentative distance to the obstacle using a direct wave and an indirect wave.

[0080] In this embodiment, an obstacle has been described as an example of an object to be detected, but the object detection device 200 is not limited to this. For example, the object detection device 200 may be configured to detect an end slot as an object.

[0081] In the present embodiment, the frequencies of ultrasonic waves transmitted from at least some different pairs of the transceiver units 21 among the multiple pairs of transceiver units 21 are different from each other, but this is not limited to this. Instead of using ultrasonic waves with different frequencies, it is also possible to use different ultrasonic waves with different coding by changing, for example, up and down chirp signals, or amplitude and / or phase and / or frequency. By improving the accuracy of identifying ultrasonic waves from each transceiver unit 21, each transceiver unit 21 can further improve the accuracy of estimating the position of an obstacle.

[0082] 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.

[0083] Although several embodiments of the present invention have been described, these embodiments are presented as examples and are not intended to limit the scope of the invention. These novel embodiments can be embodied in various other forms, and various omissions, substitutions, and modifications can be made without departing from the spirit of the invention. These embodiments and their modifications are included within the scope and spirit of the invention, and are also included in the scope of the invention and its equivalents as defined in the claims. [Explanation of symbols]

[0084] 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...computing unit, 311, 311A, 311B, 311C...direct wave distance computing unit, 313, 313A, 313B, 313C... Correction unit, 314, 314A, 314B, 314C...trilateration calculation unit, 315...obstacle distance determination unit, Dd1...first direct wave distance, Dd1'...corrected first direct wave distance, Dd2...second direct wave distance, Dd2'...corrected second direct wave distance, Wd1...first direct wave, Wd2...second direct wave, Wt1...first transmitted wave, Wt2...second transmitted wave, O...obstacle (object).

Claims

1. An object detection device mounted on a moving body and detecting an object present around the moving body, a plurality of transmitting and receiving units for transmitting and receiving ultrasonic waves; a calculation unit that calculates an object distance, which is a distance from the moving body to the object, based on the timing of transmission and reception of ultrasonic waves by each of the transmission and reception units, The calculation unit calculating a virtual distance from the moving body to the object based on timings of transmission and reception of ultrasonic waves by each pair of transceivers among the plurality of transceivers, and determining the object distance based on the plurality of virtual distances; Object detection device.

2. The calculation unit When a reflected wave of a transmission wave transmitted from one of the plurality of pairs of transmission / reception units is received by the one transmission / reception unit, and a reflected wave of a transmission wave transmitted from the other of the pair of transmission / reception units is received by the other transmission / reception unit, a first direct wave distance is calculated based on the timing at which the transmission wave was transmitted from the one transmission / reception unit and the timing at which the reflected wave of the transmission wave was received by the one transmission / reception unit, and a second direct wave distance is calculated based on the timing at which the transmission wave was transmitted from the other transmission / reception unit and the timing at which the reflected wave of the transmission wave was received by the other transmission / reception unit, correcting the first direct wave distance and the second direct wave distance based on the relative speed between the moving body and the object, and calculating the provisional distance by trilateration based on the corrected first direct wave distance and the corrected second direct wave distance. The object detection device according to claim 1 .

3. The calculation unit determines the object distance by taking a weighted average of the plurality of provisional distances. The object detection device according to claim 1 .

4. weight values in the weighted average are determined based on positions at which the plurality of pairs of transmitter-receivers are provided; The object detection device according to claim 3 .

5. The frequencies of the ultrasonic waves transmitted by at least some different pairs of the transmitting and receiving units among the plurality of pairs of the transmitting and receiving units are different from each other. The object detection device according to claim 1 .

6. one transceiver of a first pair of transceivers of the plurality of pairs of transceivers is provided at a front end portion on the forward movement side of the moving body, and the other transceiver of the first pair of transceivers is provided at a corner portion from the front end portion to a side portion of the moving body, a second pair of transceivers among the plurality of pairs of transceivers is provided on the side surface portion; one transceiver of a third pair of transceivers of the plurality of pairs of transceivers is provided at the corner portion, and the other transceiver is provided at the side portion; The object detection device according to claim 1 .

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