Object detection device

Abstract

An object detection device according to an embodiment is mounted on a mobile body and detects an object present around the mobile body, the object detection device comprising: a plurality of transmission / reception units for transmitting / receiving ultrasonic waves; and a computation unit for calculating an object distance which is a distance from the mobile body to the object on the basis of timing of transmission / reception of ultrasonic waves in the transmission / reception units, wherein the computation unit calculates the distance from the mobile body to the object by a plurality of methods on the basis of the timing of transmission / reception of ultrasonic waves in the plurality of transmission / reception units.

Description

Object detection device

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

[0002] In an object detection device that uses ultrasonic waves to detect obstacles 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 the 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 using such direct waves 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). Also, a technology for estimating the distance to an obstacle by combining a distance calculated based on direct waves and a distance calculated based on indirect waves has been disclosed (Patent Document 2, for example).

[0005] JP 2016-085041 A JP 2016-80648 A

[0006] 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.

[0007] 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.

[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 the 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 the distance from the moving body to the object using a plurality of methods based on the timing of transmission and reception of ultrasonic waves at the plurality of transmitter-receivers.

[0009] According to an object detection device according to an embodiment of the present invention, for example, an obstacle can be detected with high accuracy.

[0010] FIG. 1 is a diagram illustrating an example of the configuration of a vehicle according to the first embodiment. FIG. 2 is a diagram illustrating an example of the configuration of a vehicle control system according to the first embodiment. FIG. 3 is a diagram illustrating an example of a distance calculation method using a TOF method. FIG. 4 is a diagram illustrating an example of the functional configuration of an object detection device according to the first embodiment. FIG. 5 is a diagram illustrating an example of a first direct wave distance and a second direct wave distance according to the first embodiment. FIG. 6 is a diagram illustrating an example of a corrected first direct wave distance and a corrected second direct wave distance according to the first embodiment. FIG. 7 is a flowchart illustrating an example of an object detection process according to the first embodiment. FIG. 8 is a flowchart illustrating an example of an obstacle distance calculation process according to the first embodiment. FIG. 9 is a flowchart illustrating an example of a process when an obstacle distance is output according to the first embodiment. FIG. 10 is a diagram illustrating an example of the functional configuration of an object detection device according to the second embodiment. FIG. 11 is a diagram illustrating an example of a first direct wave distance and a second direct wave distance according to the second embodiment. FIG. 12 is a diagram illustrating an example of a corrected first direct wave distance and a corrected second direct wave distance according to the second embodiment. FIG. 13 is a diagram illustrating an example of a first indirect wave distance and a second indirect wave distance according to the second embodiment. Fig. 14 is a diagram illustrating an example of a corrected first indirect wave distance and a corrected second indirect wave distance according to the second embodiment. Fig. 15 is a flowchart illustrating an example of processing in the object detection device according to the second embodiment.

[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 a first embodiment. The vehicle 1 is an example of a moving body on which an object detection device according to this embodiment is mounted. The object detection device according to this embodiment is a device that detects obstacles (an example of objects) present around the vehicle 1 based on information such as time of flight (TOF) 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 a transceiver 21. Each transceiver 21 is installed on a vehicle body 2 that serves as 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 a transmitted wave, and ultrasonic waves generated when the transmitted wave is reflected by an object may be referred to as a reflected wave.

[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 the first 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 transmits and receives 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 reflected wave of the transmission wave reflected 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, the transmitter / receiver 21 can obtain, for example, TOF corresponding to the distance 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 ultrasound transmitted and received by the transmitter / receiver 21. In the graph shown in Fig. 3, the horizontal axis corresponds to time (TOF), and the vertical axis corresponds to the intensity of ultrasound transmitted and received by the transmitter / receiver 21 (the magnitude of vibration of the transducer 211).

[0021] The envelope L11 shows the change over time in the intensity, which indicates the magnitude of the vibration of the vibrator 211. From the envelope L11 shown in Fig. 3, it can be seen that the vibrator 211 is driven to vibrate for a period of time Ta from time t0, completing the transmission of the transmission wave at time t1, and then the vibration of the vibrator 211 due to inertia continues while attenuating for a period of time Tb until time t2. Therefore, in the graph shown in Fig. 3, the period of time Tb corresponds to the so-called reverberation time.

[0022] The envelope L11 reaches a peak at time t4, a time Tp after time t0 when the transmission of the transmission wave starts, where the magnitude of the vibration of the vibrator 211 is equal to or greater than the detection threshold Ith. This detection threshold Ith is a value set to distinguish whether the vibration of the vibrator 211 is caused by reception of a reflected wave from an obstacle O (another vehicle, a structure, a pedestrian, etc.) or reception of a reflected wave from an object other than the obstacle O (e.g., 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 reception of a reflected wave from the obstacle O.

[0023] The envelope L11 in this example shows that the vibration of the vibrator 211 is attenuated 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 transmitted wave last transmitted at timing t1 returns as a reflected wave.

[0024] Furthermore, in the 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 the obstacle O begins, in other words, the timing when the transmitted wave, which was 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 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 transmission 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 transmission 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 value 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 the object detection device 200 according to the first embodiment. The object detection device 200 according to this 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 the 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 an obstacle distance (an example of an object distance), which is the distance from the vehicle 1 to the obstacle O, based on the timing of transmission and reception of ultrasonic waves in each of the transmission and reception units 21. That is, the calculation unit 301 calculates the distance from the vehicle 1 (moving body) to the obstacle O (object) using a plurality of methods, based on the timing of transmission and reception of ultrasonic waves in the plurality of transmission and reception units 21.

[0030] The reflected waves received by each transceiver 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 21 (e.g., transceiver 21A) and received by the same transceiver 21 (e.g., transceiver 21A) as the transceiver 21 that transmitted the transmission wave. An indirect wave is a reflected wave corresponding to a transmission wave transmitted from a certain transceiver 21 (e.g., transceiver 21A) and received by a transceiver 21 (e.g., transceiver 21B) different from the transceiver 21 that transmitted the transmission wave. The calculation unit 301 according to this embodiment calculates the obstacle distance using the reception timing of the direct wave.

[0031] The direct wave distance calculation unit 311A, the correction unit 313A, and the trilateration calculation unit 314A calculate the distance to an 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).

[0032] 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.

[0033] The direct wave distance calculation unit 311C, the correction unit 313C, and the 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, the correction unit 313C, and the 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.

[0034] 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.

[0035] 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.

[0036] 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.

[0037] The direct wave distance calculation unit 311A ​​similarly calculates the first direct wave distance and the second direct wave distance, using the transceiver unit 21C on the left front end and the transceiver unit 21D at the left corner as a pair of transceivers.

[0038] 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.

[0039] 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.

[0040] The direct wave distance calculation unit 311B similarly calculates the first direct wave distance and the second direct wave distance using the transceiver units 21K and 21L on the left side surface as a pair of transceivers.

[0041] When a reflected wave of a transmission wave transmitted from the transceiver unit 21A at the right corner, which is one of the multiple transceivers 21, is received by the transceiver unit 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 unit 21A and the timing at which the reflected wave (direct wave) of the transmission wave was received by the transceiver unit 21A. Also, when a reflected wave of a transmission wave transmitted from the transceiver unit 21I at the right side is received by the transceiver unit 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 unit 21I and the timing at which the reflected wave (direct wave) of the transmission wave was received by the transceiver unit 21I.

[0042] 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.

[0043] The direct wave distance calculation unit 311C similarly calculates the first direct wave distance and the second direct wave distance, using the transceiver unit 21D at the left corner and the transceiver unit 21K on the left side as a pair of transceivers.

[0044] 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.

[0045] 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.

[0046] 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.

[0047] 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 first embodiment. Fig. 5 illustrates a situation in which the transceiver unit 21B installed on the right 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 ahead of the vehicle 1. That is, the example of 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.

[0048] 5 also illustrates a first transmission wave Wt1 transmitted from the first transceiver 21B, a first direct wave Wd1 resulting from the first transmission wave Wt1 being reflected by the obstacle O and received by the first transceiver 21B, and a second transmission wave Wt2 transmitted from the second transceiver 21A, and a second direct wave Wd2 resulting from the second transmission wave Wt2 being reflected by the obstacle O and received by the second transceiver 21A.

[0049] 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.

[0050] 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 first 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 forward.

[0051] 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.

[0052] 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 21B and the second transceiver unit 21A.

[0053] In addition, when the second distance is calculated using the direct wave distance calculation unit 311B, the correction unit 313B, and the trilateration calculation unit 314B, the same process is performed when the third distance is calculated using the direct wave distance calculation unit 311C, the correction unit 313C, and the trilateration calculation unit 314C.

[0054] 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.

[0055] Specifically, the obstacle distance determiner 315 determines the obstacle distance by calculating 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 locations of the pair of transceivers 21. For example, the third distance calculated using the transceiver 21A at the right corner and the transceiver I 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.

[0056] 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.

[0057] 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.

[0058] 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.

[0059] Next, the object detection process according to the present embodiment configured as described above will be described. Fig. 7 is a flowchart showing an example of the procedure of the object detection process according to the first embodiment. First, each of the multiple transmitter / receivers 21 transmits ultrasonic waves in a predetermined sequence (S101). Next, the direct wave distance calculation unit 311A, the correction unit 313A, and the trilateration calculation unit 314A perform distance detection processing (S102A). In parallel with this, the direct wave distance calculation unit 311B, the correction unit 313B, and the trilateration calculation unit 314B perform distance detection processing (S102B), and the direct wave distance calculation unit 311C, the correction unit 313C, and the trilateration calculation unit 314C perform distance detection processing (S102C).

[0060] 8 is a flowchart showing an example of the procedure of the distance detection process according to the first embodiment. The procedure shown in FIG. 8 is common to the distance detection processes of S102A, S102B, and S102C.

[0061] First, the direct wave distance calculation unit 311 determines whether or not the direct waves Wd1 and Wd2 have been received by the two transmitter / receivers 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, for example, by adjusting the detection cycle of each transmitter / receiver 21 (the period during which the transmitter / receiver waits to receive a reflected wave after transmitting a transmitted wave once).

[0062] If the two transmitter / receivers 21 have not received the direct waves Wd1 and Wd2 (S201: No), the process returns to the caller.

[0063] 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).

[0064] Then, 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.

[0065] 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.

[0066] 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, so high reliability is required. 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).

[0067] 9 is a flowchart showing an example of the procedure for reliability improvement processing according to the first 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 vary depending on predetermined conditions.

[0068] If the current obstacle distance is equal to or less than the threshold value 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 value (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 value (S302: No), the obstacle distance determination unit 315 discards the current obstacle distance (S304).

[0069] 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 by more than the threshold value in a short period of time to be discarded as noise.

[0070] 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.

[0071] According to this embodiment, the object detection device 200 comprises 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 hypothetical 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 hypothetical distances.

[0072] Therefore, according to this embodiment, the distance to an object such as an obstacle is estimated by multiple detection processes using multiple pairs of transmitter / receiver units 21, thereby improving the accuracy of estimating the position of the obstacle.

[0073] 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 the 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.

[0074] 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.

[0075] 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.

[0076] 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.

[0077] 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, 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.

[0078] In this embodiment, object detection is performed using three pairs of transceivers 21: a transceiver at the front end, a transceiver at a corner, two transceivers 21 at the side, and a transceiver at a corner and a transceiver at a side, but this is not limitative. Transceivers 21 at any position can be used for object detection in this embodiment.

[0079] In the present embodiment, three pairs of transceivers 21 have been described as an example of the multiple pairs of transceivers 21. However, 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 transceivers 21 or four or more pairs of transceivers 21.

[0080] In this embodiment, the calculation unit 301 determines the tentative distance to the obstacle using direct waves, but if indirect waves can be received, the calculation unit 301 may be configured to calculate the tentative distance to the obstacle using direct waves and indirect waves.

[0081] In the present 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.

[0082] In the present embodiment, the frequencies of the 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 of different frequencies, for example, different ultrasonic waves may be used that are different in terms of up and down chirp signals or different coding by changing the amplitude, 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.

[0083] [Second Embodiment] In the first embodiment, the obstacle distance is calculated using the reception timing of the direct wave, but in this second embodiment, the obstacle distance is calculated using both the reception timing of the direct wave and the reception timing of the indirect wave.

[0084] The configuration of the vehicle 1, the configuration of the vehicle control system 50, and the method of calculating distance using the TOF method in the second embodiment are the same as those in the first embodiment described using Figures 1 to 3, so their explanation will be omitted.

[0085] 10 is a diagram showing an example of the functional configuration of an object detection device 1200 according to the second embodiment. The object detection device 1200 according to this embodiment includes a calculation unit 1301. The calculation unit 1301 includes a direct wave distance calculation unit 1311, an indirect wave distance calculation unit 1312, a correction unit 1313, and a trilateration calculation unit 1314. These functional units can be realized, for example, by cooperation between hardware and software (programs, etc.) of the object detection device 1200 as shown in FIG. 2. Furthermore, at least some of these functional units may be realized by dedicated hardware (circuits).

[0086] The calculation unit 1301 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 in each of the transmission and reception units 21. That is, the calculation unit 301 calculates the distance from the vehicle 1 (moving body) to the obstacle O (object) using multiple methods based on the timing of transmission and reception of ultrasonic waves in the multiple transmission and reception units 21.

[0087] The reflected waves received by each transmitter / receiver 21 according to this embodiment include direct waves and indirect waves. The definitions of direct waves and indirect waves are the same as those in the first embodiment, and therefore will not be explained further. The calculation unit 1301 according to this embodiment calculates the obstacle distance using both the reception timing of the direct waves and the reception timing of the indirect waves.

[0088] The calculation unit 1301 according to this embodiment includes a direct wave distance calculation unit 1311 , an indirect wave distance calculation unit 1312 , a correction unit 1313 , and a trilateration calculation unit 1314 .

[0089] Similar to the direct wave distance calculation units 311A, 311B, and 311C according to the first embodiment, 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 1311 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, similar to the direct wave distance calculation units 311A, 311B, and 311C according to the first embodiment, 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 1311 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, and the second direct wave distance is calculated based on the direct wave received by the second transceiver.

[0090] 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) that is different from the third transceiver unit, the indirect wave distance calculation unit 1312 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 of the transmission wave (indirect wave) was received by the fourth transceiver unit. Furthermore, 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 1312 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 of the transmission wave (indirect 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.

[0091] The correction unit 1313 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.

[0092] The trilateration calculation unit 1314 calculates the obstacle distance by trilateration based on the corrected first direct wave distance and the corrected second direct wave distance, similar to the trilateration calculation units 314A, 314B, and 314C according to the first embodiment. The trilateration calculation unit 1314 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 1314 is output to the ECU 100 and used for various vehicle controls.

[0093] According to the above configuration, when direct waves are detected by each of the two transmission / reception 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 each of the two transmission / reception 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.

[0094] Fig. 11 is a diagram showing an example of the first direct wave distance Dd1 and the second direct wave distance Dd2 according to the second embodiment. Fig. 11 illustrates a situation in which two transceivers 21G and 21H installed at the rear of the vehicle 1 are designated as the first transceiver and the second transceiver, respectively, and an obstacle O is present behind the vehicle 1. Fig. 11 also illustrates a first transmission wave Wt1 transmitted from the first transceiver 21G and a first direct wave Wd1 resulting from the first transmission wave Wt1 being reflected by the obstacle O and received by the first transceiver 21G. Fig. 11 also illustrates a second transmission wave Wt2 transmitted from the second transceiver 21H and a second direct wave Wd2 resulting from the second transmission wave Wt2 being reflected by the obstacle O and received by the second transceiver 21H.

[0095] 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.

[0096] 12 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 second embodiment. In FIG. 12, 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.

[0097] 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.

[0098] 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 unit 21G and the second transceiver unit 21H.

[0099] Fig. 13 is a diagram showing an example of the first indirect wave distance Di1 and the second indirect wave distance Di2 according to the second embodiment. Fig. 13 illustrates a situation in which two transceivers 21G and 21H installed at the rear of the vehicle 1 are the third transceiver and the fourth transceiver, respectively, 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.

[0100] 13 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.

[0101] 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.

[0102] 14 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. 12, FIG. 14 illustrates the corrected first indirect wave distance Di1′ and the corrected second indirect wave distance Di2′ when the vehicle 1 is gradually moving backward.

[0103] 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. Also, 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, by multiplying the calculated relative speed by a predetermined time, it is possible to estimate the virtual positions P1, P2 of the obstacle O after the predetermined time has elapsed, and it is possible to calculate the distance change amounts ΔD1, ΔD2 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'.

[0104] 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.

[0105] 15 is a flowchart showing an example of processing in the object detection device 1200 according to the second embodiment. First, the direct wave distance calculation unit 1311 determines whether or not the two transmitter / receivers 21 have received the direct waves Wd1 and Wd2 (S1101). 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 transmitter / receiver 21 (the period from transmitting a transmission wave once to waiting for reception of a reflected wave).

[0106] When two transmitter / receivers 21 receive direct waves Wd1 and Wd2, respectively (S1101: Yes), the direct wave distance calculation unit 1311 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 (S1102).

[0107] Thereafter, the correction unit 1313 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 (S1103), and the trilateration calculation unit 1314 calculates the obstacle distance by trilateration based on the corrected first direct wave distance Dd1′ and the corrected second direct wave distance Dd2′ (S1104).The calculated obstacle distance is then output to the ECU 100, etc. (S1105).

[0108] On the other hand, if the two transmitter-receivers 21 have not received the direct waves Wd1 and Wd2 (S1101: No), the indirect wave distance calculation unit 1312 determines whether the two transmitter-receivers 21 have received the indirect waves Wi1 and Wi2 (S1106). 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 transmitter-receiver 21.

[0109] If the two transmitter-receivers 21 have not received the indirect waves Wi1 and Wi2 (S1106: No), this routine ends. If the two transmitter-receivers 21 have received the indirect waves Wi1 and Wi2 (S1106: Yes), the indirect wave distance calculation unit 1312 calculates the first indirect wave distance Di1 and the second indirect wave distance Di2 for each of the two transmitter-receivers 21 based on the timings at which the transmission waves Wt1 and Wt2 were transmitted and the timings at which the indirect waves Wt1 and Wt2 were received (S1107).

[0110] Thereafter, the correction unit 1313 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 (S1108), and the trilateration calculation unit 1314 calculates the obstacle distance by trilateration based on the corrected first indirect wave distance Di1′ and the corrected second indirect wave distance Di2′ (S1109).The calculated obstacle distance is then output to the ECU 100, etc. (S1105).

[0111] 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, so high reliability is required. Therefore, the calculation unit 1301 according to this embodiment has a function for improving the reliability of the obstacle distance to be output.

[0112] Here, the process for improving the reliability of the obstacle distance is the same as the process for outputting the obstacle distance according to the first embodiment described with reference to FIG. 9, and therefore will not be described here.

[0113] As described above, according to this embodiment, when direct waves are detected by the two transmitter-receivers 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 transmitter-receivers 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.

[0114] A program that causes a computer (such as processor 223) to execute processing for realizing the functions of object detection device 200, 1200 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.

[0115] 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.

[0116] [Summary of the Present Embodiment] The object detection device (200, 1200) of the present embodiment has at least the following configuration.

[0117] That is, the object detection device (200, 1200) according to the embodiment is an object detection device (200, 1200) mounted on a moving body and detecting objects present in the vicinity of the moving body, and comprises: a plurality of transmitter-receivers (21) that transmit and receive ultrasonic waves; and a calculation unit (301, 1301) 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 in each of the transmitter-receivers (21), and the calculation unit (301, 1301) calculates the distance from the moving body to the object using a plurality of methods based on the timing of transmission and reception of ultrasonic waves in the plurality of transmitter-receivers (21).

[0118] This configuration, for example, makes it possible to detect obstacles with high accuracy.

[0119] Furthermore, in the object detection device (200) according to the embodiment, the calculation unit (301) calculates a hypothetical distance from the moving body to the object based on the timing of transmission and reception of ultrasonic waves in each pair of transmission and reception units (21) among the plurality of transmission and reception units (21), and determines the object distance based on the plurality of hypothetical distances.

[0120] With this configuration, for example, the distance to an object such as an obstacle is estimated by a plurality of detection processes using a plurality of pairs of transmitter / receiver units 21, thereby improving the accuracy of estimating the position of the obstacle.

[0121] In addition, in the object detection device (200) according to the embodiment, when a reflected wave of a transmission wave transmitted from one of the pairs of transmission / reception units (21) of the multiple pairs of transmission / reception units (21) 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 (21) is received by the other transmission / reception unit, the calculation unit (301) calculates a first direct wave distance 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 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, corrects the first direct wave distance and the second direct wave distance based on the relative velocity between the moving body and the object, and calculates the provisional distance by trilateration based on the corrected first direct wave distance and the corrected second direct wave distance.

[0122] With this configuration, for example, the obstacle distance is determined based on a direct wave, which can further improve the accuracy of estimating the position of the obstacle.

[0123] In the object detection device (200) according to the embodiment, the calculation unit (301) determines the object distance by taking a weighted average of the plurality of provisional distances.

[0124] With this configuration, for example, it is possible to weight each pair of transmitter / receiver units (21) taking into consideration their reliability, thereby further improving the accuracy of estimating the position of an obstacle.

[0125] In the object detection device (200) according to the embodiment, the weight values ​​in the weighted average are determined based on the positions at which the plurality of pairs of transmitter-receivers are provided.

[0126] With this configuration, for example, it is possible to weight each pair of transmitter / receiver units 21 taking into consideration the reliability based on the position, thereby further improving the accuracy of estimating the position of an obstacle.

[0127] In the object detection device (200) according to the embodiment, the frequencies of the ultrasonic waves transmitted by at least some different pairs of the plurality of pairs of the transmitting and receiving units are different from each other.

[0128] With this configuration, for example, each transmitting / receiving unit (21) can receive direct waves more reliably, and the accuracy of estimating the position of an obstacle can be further improved.

[0129] Furthermore, in the object detection device (200) according to the embodiment, of the multiple pairs of transmitter-receivers (21), one transmitter-receiver of a first pair of transmitter-receivers is provided at the front end portion on the forward moving side of the moving body, and the other transmitter-receiver of the first pair of transmitter-receivers is provided at a corner portion from the front end portion to the side portion of the moving body, a second pair of transmitter-receivers of the multiple pairs of transmitter-receivers (21) is provided at the side portion, and one transmitter-receiver of a third pair of transmitter-receivers of the multiple pairs of transmitter-receivers (21) is provided at the corner portion, and the other transmitter-receiver is provided at the side portion.

[0130] With this configuration, for example, pairs of transmitter / receivers (21) located at different positions are used for object detection, so that the accuracy of estimating the position of an obstacle can be further improved.

[0131] Moreover, in the object detection device (1200) according to the embodiment, when a reflected wave of a transmission wave transmitted from a first transceiver unit that is one of the plurality of transceivers (21) 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 calculation unit (1301) 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 object, and calculates the object 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 unit, which is one of the plurality of transceivers (21), 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 at which the transmission wave was transmitted from the third transceiver unit and the timing at which the reflected wave of the transmission wave was received by the fourth transceiver unit, and 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 of the transmission wave was received by the third transceiver unit are calculated, the first indirect wave distance and the second indirect wave distance are corrected based on the relative velocity, and the object distance is calculated by trilateration based on the corrected first indirect wave distance and the corrected second indirect wave distance.

[0132] With this configuration, as an example, when direct waves are detected by each of the two transmitters and 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 each of the two transmitters and 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 obstacles to be detected with high accuracy by trilateration, even when only direct waves or indirect waves can be detected.

[0133] In addition, in the object detection device (1200) according to the embodiment, the relative velocity is calculated based on a Doppler shift between the frequency of the transmitted wave and the frequency of the reflected wave corresponding to the transmitted wave.

[0134] With this configuration, for example, the relative velocity can be calculated using information acquired from the transmitting / receiving unit (21).

[0135] In the object detection device (1200) according to the embodiment, the calculation unit (1301) discards the obstacle distance when the object distance calculated by the trilateration is greater than a predetermined threshold value.

[0136] With this configuration, for example, it is possible to use only object distances that are within a distance range where sufficient accuracy can be obtained, thereby improving the reliability of obstacle distances.

[0137] Furthermore, in the object detection device (1200) according to the embodiment, the calculation unit (1301) discards the current object distance if the difference between the current object distance and a previous object distance calculated a predetermined time before the time the current object distance was calculated is greater than a predetermined threshold.

[0138] As an example, since an object distance that fluctuates significantly in a short period of time is likely to be noise, the above configuration can improve the reliability of the object distance.

[0139] 1...vehicle, 2...vehicle body, 21, 21A to 21L...transmitter / receiver unit, 50...vehicle control system, 100...ECU, 200, 1200...object detection device, 211...vibrator, 220...control unit, 221...input / output device, 222...storage device, 223...processor, 301, 1301...computation unit, 311, 311A, 311B, 311C, 1311...direct wave distance calculation unit, 313, 313A, 313B, 313 C, 1313...correction unit, 314, 314A, 314B, 314C, 1314...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 to detect objects present in the vicinity of the moving body, comprising: a plurality of transmitter / receivers that transmit and receive ultrasonic waves; and a calculation unit that calculates the 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, wherein the calculation unit calculates the distance from the moving body to the object using a plurality of methods based on the timing of transmission and reception of ultrasonic waves at the plurality of transmitter / receivers.

2. The object detection device of claim 1, wherein the calculation unit calculates a virtual distance from the moving body to the object based on the timing of transmission and reception of ultrasonic waves in each pair of transceivers among the plurality of transceivers, and determines the object distance based on the multiple virtual distances.

3. The object detection device described in claim 2, wherein, when a reflected wave of a transmission wave transmitted from one of the multiple pairs of transmission / reception units is received by that 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, the calculation unit calculates a first direct wave distance based on the timing at which the transmission wave is transmitted from the one transmission / reception unit and the timing at which the reflected wave of the transmission wave is received by the one transmission / reception unit, and a second direct wave distance based on the timing at which the transmission wave is transmitted from the other transmission / reception unit and the timing at which the reflected wave of the transmission wave is received by the other transmission / reception unit, corrects the first direct wave distance and the second direct wave distance based on the relative speed between the moving body and the object, and calculates the provisional distance by trilateration based on the corrected first direct wave distance and the corrected second direct wave distance.

4. The object detection device according to claim 2, wherein the calculation unit determines the object distance by taking a weighted average of the plurality of provisional distances.

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

6. The object detection device according to claim 2, wherein the frequencies of ultrasonic waves transmitted by at least some different pairs of transmitting and receiving units among the plurality of pairs of transmitting and receiving units are different from each other.

7. An object detection device as described in claim 2, wherein, of the multiple pairs of transmitter-receivers, one transmitter-receiver of a first pair is provided at the front end portion on the forward moving side of the moving body, and the other transmitter-receiver of the first pair is provided at a corner from the front end portion to a side portion of the moving body; a second pair of transmitter-receivers of the multiple pairs of transmitter-receivers are provided at the side portion; and one transmitter-receiver of a third pair of transmitter-receivers of the multiple pairs of transmitter-receivers is provided at the corner portion, and the other transmitter-receiver is provided at the side portion.

8. When a reflected wave of a transmission wave transmitted from a first transmission / reception unit that is one of the plurality of transmission / reception units is received by the first transmission / reception unit and a reflected wave of a transmission wave transmitted from a second transmission / reception unit different from the first transmission / reception unit is received by the second transmission / reception unit, the calculation unit calculates a first direct wave distance based on the timing at which the transmission wave was transmitted from the first transmission / reception unit and the timing at which the reflected wave of the transmission wave was received by the first transmission / reception unit, and a second direct wave distance based on the timing at which the transmission wave was transmitted from the second transmission / reception unit and the timing at which the reflected wave of the transmission wave was received by the second transmission / reception unit, corrects the first direct wave distance and the second direct wave distance based on the relative speed between the moving body and the object, and calculates the object distance by trilateration based on the corrected first direct wave distance and the corrected second direct wave distance, 2. The object detection device according to claim 1, wherein, 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, the device calculates a first indirect wave distance based on a timing at which the transmission wave is transmitted from the third transceiver and a timing at which the reflected wave of the transmission wave is received by the fourth transceiver, and a second indirect wave distance based on a timing at which the transmission wave is transmitted from the fourth transceiver and a timing at which the reflected wave of the transmission wave is received by the third transceiver; corrects the first indirect wave distance and the second indirect wave distance based on the relative velocity; and calculates the object distance by trilateration based on the corrected first indirect wave distance and the corrected second indirect wave distance.

9. The object detection device according to claim 8, wherein the relative velocity is calculated based on a Doppler shift between the frequency of the transmitted wave and the frequency of the reflected wave corresponding to the transmitted wave.

10. The object detection device according to claim 8, wherein the calculation unit discards the object distance calculated by the trilateration if the object distance is greater than a predetermined threshold value.

11. The object detection device according to claim 8, wherein the calculation unit discards the current object distance if the difference between the current object distance and a previous object distance calculated a predetermined time before the current object distance is calculated is greater than a predetermined threshold.

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