Object detection device

Abstract

To provide an object detection device with improved object detection accuracy.SOLUTION: An object detection device is provided, comprising a transmission unit, reception unit, detection unit, and control unit. The transmission unit transmits a transmission wave. The reception unit receives reception waves caused when the transmission wave is reflected by objects. The detection unit uses the reception waves to detect objects existing in the surroundings of a mobile vehicle. When two objects are detected in a traveling direction of the mobile vehicle, and distances between the mobile vehicle and the objects become less than a predetermined distance, the control unit controls the transmission unit such that a first time period, including a transmission time period of the transmission wave and a reverberation time period corresponding to a period of reverberation of the transmission unit associated with the transmission of the transmission wave, becomes less than that when the distances between the mobile vehicle and the objects are equal to or greater than the predetermined distance.SELECTED DRAWING: Figure 6

Description

[Technical Field]

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

[0002] In vehicle control systems and the like, object detection devices are used that detect objects present around the vehicle by transmitting transmission waves such as ultrasonic waves from the vehicle and receiving reception waves (reflected waves) generated when the transmission waves are reflected by the object. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2014-234057 Summary of the Invention [Problem to be solved by the invention]

[0004] One of the problems that the present disclosure aims to solve is to improve the accuracy of object detection in an object detection device. [Means for solving the problem]

[0005] An example of an object detection device of the present disclosure is an object detection device mounted on a moving body, and includes: a transmitting unit that transmits a transmission wave; a receiving unit that receives a reception wave generated when the transmission wave is reflected by an object; a detecting unit that detects the object present in the vicinity of the moving body based on the reception wave; and a control unit that, when two objects are detected in the direction of travel of the moving body and the distance between the moving body and the objects becomes shorter than a specified distance, controls the transmitting unit so that a first time period including a transmission time of the transmission wave and a reverberation time which is the reverberation time of the transmitting unit associated with transmitting the transmission wave becomes shorter than when the distance between the moving body and the objects is equal to or greater than the specified distance.

[0006] According to the above configuration, when two objects are detected in the traveling direction of the moving body and the distance between the moving body and the objects is shorter than a specified distance, the first time period including the transmission time of the transmitted wave and the reverberation time is shorter than when the distance between the moving body and the objects is equal to or greater than the specified distance. Therefore, when two objects are detected in the traveling direction of the moving body and the distance between the moving body and the objects is shorter than the specified distance, the accuracy of object detection can be improved compared to a configuration in which the first time period is not changed.

[0007] In the object detection device, for example, when the distance between the moving body and the object becomes shorter than the specified distance, the control unit reduces the number of pulses of the transmission wave compared to when the distance between the moving body and the object is equal to or greater than the specified distance.

[0008] According to the above configuration, the first time period can be shortened by making the number of pulses of the transmission wave shorter than when the distance between the moving body and the object is equal to or greater than a specified distance, so that the first time period can be shortened relatively easily.

[0009] The object detection device includes, for example, a plurality of transmitting units and a change unit that changes the transmitting unit among the plurality of transmitting units that transmits the transmission wave depending on the distance between the moving body and the object.

[0010] According to the above configuration, the transmitter can be changed depending on the distance between the moving body and the object. [Brief explanation of the drawings]

[0011] [Figure 1] FIG. 1 is a top view illustrating an example of a configuration of a vehicle according to an embodiment. [Figure 2] FIG. 2 is a block diagram illustrating an example of a hardware configuration of the 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 block 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 situation when a vehicle is moved in the parking assistance process according to the embodiment. [Figure 6] FIG. 6 is a flowchart illustrating an example of a part of the object detection process according to the embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0012] 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.

[0013] 1 is a top view 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 this embodiment is mounted. The object detection device according to this embodiment is a device that detects objects present around the vehicle 1 based on information such as TOF (Time Of Flight) and Doppler shift acquired by transmitting a transmission wave from the vehicle 1 and receiving a reception wave (reflected wave) generated when the transmission wave is reflected by an object.

[0014] The object detection device according to this embodiment includes a plurality of transceivers 21A to 21L (hereinafter, referred to simply as transceivers 21 when there is no need to distinguish between the plurality of transceivers 21A to 21L). Each transceiver 21 is installed on a vehicle body 2, which is the exterior of a vehicle 1, and transmits ultrasonic waves (an example of a transmitted wave) toward the outside of the vehicle body 2 and receives reflected waves from objects outside the vehicle body 2 as received waves. In the example shown in FIG. 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 locations of the transceivers 21 are not limited to those in this example.

[0015] 2 is a block diagram showing an example of a hardware 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 an 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 multiple 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 (received wave) of the transmission wave reflected by an object such as an obstacle O or a road surface RS. 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 of the obstacle O. The obstacle O is an example of an object.

[0017] 2 illustrates a configuration in which both transmission of transmission waves and reception of reception waves 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 transmission waves and an oscillator for receiving reception waves 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 the outside (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) that operates according to a program, an application-specific integrated circuit (ASIC) designed for a specific application, or the like. 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 various 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, 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 ultrasonic waves transmitted and received by the transmitting and receiving unit 210. In the graph shown in Fig. 3, the horizontal axis corresponds to time (TOF), and the vertical axis corresponds to the intensity of ultrasonic waves transmitted and received by the transmitting and receiving unit 210 (the magnitude of vibration of the transducer 211).

[0021] The envelope L11 indicates the change over time in the intensity, which indicates the magnitude of the vibration of the oscillator 211. From the envelope L11 illustrated in FIG. 3, it can be seen that the oscillator 211 is driven and vibrates for a time Ta from time t0, completing the transmission of the transmission wave at time t1. Then, for a time Tb until time t2, the oscillation of the oscillator 211 due to inertia continues while attenuating. Therefore, in the graph shown in FIG. 3, the time Ta corresponds to the transmission time, and the time Tb corresponds to the reverberation time of the transmitter 301. The reverberation time is the time from the completion of transmission of the transmission wave until the oscillation due to inertia of the oscillator 211 subsides below the reverberation threshold. The reverberation threshold is smaller than the detection threshold Ith. Hereinafter, the time Ta will also be referred to as the transmission time Ta, and the time Tb will also be referred to as the reverberation time Tb. The time constituted by the transmission time Ta and the reverberation time Tb will be referred to as a first time Tc.

[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 reception wave from an obstacle O (another vehicle, a structure, a pedestrian, etc.) or by the reception of a reception wave from an object other than the obstacle O (for example, a road surface RS, 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 reception 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 reception 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 reception 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 received wave from obstacle O begins, in other words, the timing when the transmitted wave first transmitted at timing t0 returns as a received 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 source of transmission and reception of ultrasonic waves to the obstacle O, it is necessary to find the time Tf between the time t0 when the transmission wave begins and the time t3 when the reception wave begins. This time Tf can be found by subtracting the time ΔT, which is equal to the time Ta for transmission 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 received wave reaches 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 received wave reaches a peak and becomes equal to or greater than the detection threshold Ith, the distance from the source of transmission and reception to the obstacle O can be obtained.

[0027] 4 is a block 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 transmission unit 301, a reception unit 302, a preprocessing unit 303, a detection unit 304, a mode setting unit 305, and a transmission unit control unit 306. These functional components 301 to 306 can be realized, for example, by cooperation between hardware components of object detection device 200 as shown in FIG. 2 and software components such as firmware and programs. Transmission unit control unit 306 is an example of a control unit.

[0028] The transmitting unit 301 transmits a transmission wave to the outside by vibrating the above-mentioned vibrator 211. In addition to the vibrator 211, the transmitting unit 301 can be configured using, for example, a circuit that generates a carrier wave, a circuit that generates a pulse signal corresponding to identification information to be assigned to the carrier wave, a multiplier that modulates the carrier wave in accordance with the pulse signal, an amplifier that amplifies the transmission signal output from the multiplier, and the like.

[0029] The receiving unit 302 receives a received wave generated when the transmitted wave transmitted from the transmitting unit 301 is reflected by an object. The receiving unit 302 can be configured using, in addition to the vibrator 211, for example, an AD converter or the like.

[0030] The preprocessing unit 303 performs preprocessing to generate echo information (e.g., an envelope as shown in Fig. 3) that indicates changes in the intensity of the received wave over time. The preprocessing may include, for example, an amplification process that amplifies the received signal corresponding to the received wave, a filtering process that reduces noise contained in the amplified received signal, and a correlation process that obtains a correlation value that indicates the similarity between the transmitted signal and the received signal.

[0031] The detection unit 304 detects an obstacle O present around the vehicle 1 based on the received wave. Specifically, it generates object information indicating the result of object detection based on the echo information generated by the pre-processing unit 303. For example, the detection unit 304 generates object information indicating the presence or absence of an obstacle O, the distance to the obstacle O, etc., based on the TOF when the intensity of the envelope L11 as illustrated in FIG. 3 exceeds a predetermined threshold (for example, a detection threshold Ith).

[0032] The mode setting unit 305 switches between multiple distance modes depending on the situation. A distance mode is determined for each target distance range. For example, a short-distance mode that targets a predetermined short-distance range, a long-distance mode that targets a long-distance range that is farther than the short-distance range, and the like can be set as distance modes. Note that a medium-distance mode that targets a medium-distance range that is a portion between the short-distance range and the long-distance range may also be provided. The mode setting unit 305 according to this embodiment sets the distance mode based on vehicle state information, driving assistance information, and the like acquired from the ECU 100, etc. The vehicle state information may be information indicating the driving state of the vehicle 1 (e.g., whether the ignition power is on or off, whether the accessory power is on or off, etc.), the traveling state (e.g., vehicle speed, acceleration, deceleration, etc.), etc. The driving assistance information is information related to processing for assisting the driving of the vehicle 1. The driving assistance information may include, for example, information related to parking assistance processing for automatically (including semi-automatically) parking the vehicle 1 in a parking area, information related to steering control for automatically operating a steering mechanism such as a steering wheel, and the like.

[0033] Furthermore, the mode setting unit 305 changes the transmitting unit 301 that transmits the transmission wave from among the plurality of transmitting units 301 in accordance with the distance between the vehicle 1 and the obstacle O.

[0034] The transmission unit control unit 306 sets (changes) the first time Tc according to the distance mode set by the mode setting unit 305. For example, when two obstacles O are detected in the traveling direction of the vehicle 1 and the distance between the vehicle 1 and the obstacles O becomes shorter than a specified distance, the transmission unit control unit 306 controls the transmission unit 301 so that the first time Tc becomes shorter than when the distance between the vehicle 1 and the obstacles OA, OB is equal to or greater than the specified distance.

[0035] Specifically, the transmitter control unit 306 changes the first time Tc by changing the number of pulses of the transmission wave transmitted from the transmitter 301 according to the distance mode set by the mode setting unit 305. The transmitter control unit 306 according to this embodiment sets the number of pulses of the transmission wave in the short-distance mode to be smaller than the number of pulses of the transmission wave in other distance modes (e.g., long-distance mode) that target a range farther than the short-distance range. The number of pulses here refers to the number of pulses of the transmission wave in one detection cycle, which corresponds to, for example, the number of pulses of the transmission wave transmitted during time Ta in FIG. 3 . The smaller the number of pulses, the shorter the detection cycle (waiting time for the reception wave), making it easier to detect an object in the short distance. The transmitter control unit 306 may shorten the reverberation time Tb by oscillating an ultrasonic wave in the opposite phase to the transmission wave after completing transmission of the transmission wave, thereby shortening the first time Tc. The transmitter control unit 306 may also modulate the transmission wave.

[0036] Next, an object detection process in the object detection device 200 will be described. Fig. 5 is a diagram showing an example of a situation when a vehicle is moved in the parking assistance process according to the embodiment. Fig. 6 is a flowchart showing an example of a part of the object detection process according to the embodiment.

[0037] Here, as shown in Fig. 5, object detection processing will be described in a situation where there are two obstacles OA and OB in the traveling direction of the vehicle 1, and the vehicle is to be parked between them or pass between them. In the parking assistance processing, the distance D1 between the end points Oa (end points) of each of the two obstacles OA and OB is detected from echo information based on ultrasonic waves transmitted and received by the transmitter / receiver 21 of the vehicle 1. In this case, the long distance mode is used. In the parking assistance processing, when the vehicle 1 approaches the two obstacles OA and OB, the distance mode of the object detection device 200 is set to the short distance mode.

[0038] When the parking control button is operated, as shown in Fig. 7, the mode setting unit 305 sets the distance mode to the long distance mode (S11). The mode setting unit 305 also sets the transmission unit group to be used. Specifically, the mode setting unit 305 sets the first transmission unit group as the transmission unit group to be used. The first transmission unit group includes the transceivers 21A to 21D, 21E to 21H, 21J, and 21L.

[0039] The transmission unit control unit 306 transmits transmission waves (ultrasound waves) from the transmission units 301 of the first transmission unit group (transmission / reception units 21A to 21D, 21E to 21H, 21J, and 21L) (S12). The reception unit 302 receives the reception waves (ultrasound waves) (S13). The detection unit 304 acquires the TOF (S14) and estimates the positions of obstacles OA and OB in the traveling direction of the vehicle 1 based on the TOF (S15).

[0040] The detection unit 304 determines whether there are two obstacles OA and OB in the traveling direction of the vehicle (S16). If the detection unit 304 determines that there are two obstacles OA and OB in the traveling direction of the vehicle (S16: Yes), the detection unit 304 determines whether the distance between the two obstacles OA and OB (distance D1) is greater than the width of the vehicle 1 (S17).

[0041] If the detection unit 304 determines that the distance (distance D1) between the two obstacles OA and OB is greater than the width of the vehicle 1 (S17: Yes), it determines whether the distance between the obstacles OA and OB and the vehicle 1 is shorter than a specified distance (S18).

[0042] If the detection unit 304 determines that the distance between the obstacles OA, OB and the vehicle 1 is shorter than the specified distance (S18: Yes), the mode setting unit 305 sets the distance mode to the short distance mode (S19). At this time, the mode setting unit 305 changes the transmitting unit group to be used to the second transmitting unit group. The second transmitting unit group is the transceivers 21A to 21L.

[0043] On the other hand, if the detection unit 304 determines that there are no two obstacles OA and OB in the direction of travel of the vehicle 1 (S16: No), if it determines that the distance between the two obstacles OA and OB is not greater than the width of the vehicle 1 (S17: No), or if it determines that the distance between the obstacles OA and OB and the vehicle 1 is not shorter than the specified distance (S18: No), it returns to S11.

[0044] In the above process, if the vehicle 1 moves between the obstacles OA and OB (objects), the first time period Tc may be further shortened. That is, the first time period Tc may be shortened as the distance between the vehicle and the obstacles OA and OB (objects) becomes shorter.

[0045] As described above, the object detection device 200 of this embodiment is mounted on a vehicle 1 (mobile body). The object detection device 200 includes a transmitter 301, a receiver 302, a detector 304, and a transmitter controller 306. The transmitter 301 transmits a transmission wave. The receiver 302 receives a reception wave generated when the transmission wave is reflected by an obstacle O (object). The detector 304 detects an obstacle O (obstacles OA, OB) present around the vehicle 1 based on the reception wave. When two obstacles OA and OB (objects) are detected in the traveling direction of the vehicle 1 (moving body) and the distance between the vehicle 1 and the obstacles OA and OB becomes shorter than a specified distance, the transmission unit control unit 306 controls the transmission unit 301 so that the first time Tc, which includes the transmission time Ta of the transmission wave and the reverberation time Tb, which is the reverberation time of the transmission unit 301 associated with the transmission of the transmission wave, becomes shorter than when the distance between the vehicle 1 and the obstacles OA and OB is equal to or greater than the specified distance.

[0046] According to the above configuration, when two obstacles OA, OB are detected in the traveling direction of the vehicle 1 (moving object) and the distance between the vehicle 1 and the obstacles OA, OB becomes shorter than a specified distance, the first time Tc becomes shorter than when the distance between the vehicle 1 and the obstacles OA, OB is equal to or greater than the specified distance. Therefore, when two obstacles OA, OB are detected in the traveling direction of the vehicle 1 and the distance between the vehicle 1 and the obstacles OA, OB becomes shorter than the specified distance, the accuracy of detecting the obstacles OA, OB can be improved compared to a configuration in which the first time Tc is not changed.

[0047] In addition, when the distance between the vehicle 1 and the obstacle O (obstacles OA, OB) becomes shorter than a specified distance, the transmission unit control unit 306 shortens the number of pulses of the transmission wave compared to when the distance between the vehicle 1 and the obstacle O (obstacles OA, OB) is equal to or greater than the specified distance.

[0048] According to the above configuration, the first time Tc is shortened by making the number of pulses of the transmission wave shorter than when the distance between the vehicle 1 and the obstacle O (obstacles OA, OB) is equal to or greater than a specified distance, so that the first time Tc can be shortened relatively easily.

[0049] The object detection device 200 also includes, for example, a plurality of transmitting units 301 and a mode setting unit 305 (changing unit) that changes which of the plurality of transmitting units 301 transmits a transmission wave depending on the distance between the vehicle 1 and the obstacles OA and OB.

[0050] According to the above configuration, the transmitter 301 can be changed depending on the distance between the vehicle 1 and the obstacles OA and OB.

[0051] A program that causes a computer (for example, processor 223 of control unit 220, processor 130 of ECU 100, etc.) to execute processes for realizing the various functions in the above-described embodiments 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.

[0052] Although the embodiments of the present disclosure have been described above, the above-described embodiments and their modifications are merely examples and are not intended to limit the scope of the invention. The novel embodiments and modifications described above can be implemented in various forms, and various omissions, substitutions, and modifications can be made without departing from the spirit of the invention. The above-described embodiments and modifications are included within the scope and spirit of the invention, and are also included in the inventions and their equivalents as defined in the claims. [Explanation of symbols]

[0053] 1...vehicle, 2...vehicle body, 21, 21A to 21L...transmitter / receiver unit, 50...vehicle control system, 100...ECU, 110...input / output device, 120...storage device, 130...processor, 200...object detection device, 211...vibrator, 220...control unit, 221...input / output device, 222...storage device, 223...processor, 301...transmitter unit, 302...receiver unit, 303...preprocessing unit, 304...detection processing unit, 305...mode setting unit, 306...control unit, O, OA, OB...obstacle

Claims

1. An object detection device mounted on a moving body, a transmitting unit that transmits a transmission wave; a receiving unit that receives a received wave generated when the transmitted wave is reflected by an object; a detection unit that detects the object present around the moving object based on the received wave; a control unit that controls the transmitting unit when two objects are detected in the moving direction of the moving body and the distance between the moving body and the objects becomes shorter than a specified distance, so that a first time period including a transmission time of the transmission wave and a reverberation time that is a time period for reverberation in the transmitting unit accompanying transmission of the transmission wave becomes shorter than when the distance between the moving body and the objects is equal to or greater than the specified distance; An object detection device comprising:

2. when the distance between the moving body and the object becomes shorter than the specified distance, the control unit reduces the number of pulses of the transmission wave compared to when the distance between the moving body and the object is equal to or greater than the specified distance. The object detection device according to claim 1 .

3. A plurality of the transmitters; a change unit that changes the transmitter that transmits the transmission wave among the plurality of transmitters in accordance with the distance between the moving body and the object; The object detection device according to claim 1 , comprising:

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