Object detection device

Abstract

The present application provides an object detection device capable of effectively utilizing road surface information. The object detection device detects an object existing around a moving body moving on a road surface by a TOF method. The object detection device includes a first acquisition unit that acquires object information containing distance information of a detection target based on a comparison result of a signal level of a reflected wave and a first threshold value; a second acquisition unit that acquires road surface information containing distance information of a road surface based on a comparison result of the signal level of the reflected wave and a second threshold value; and a setting unit that sets the second threshold value so that an information amount of the distance information acquired within a prescribed period does not exceed a prescribed amount.

Description

Technical Field

[0001] This invention relates to an object detection device. Background Technology

[0002] In vehicle-mounted driving assistance systems, devices utilize the Time-of-Flight (TOF) method to detect objects around the vehicle. The TOF method detects the presence or distance of an object by measuring the time it takes for a transmitted wave (ultrasound, electromagnetic wave, etc.) sent towards the object to reflect back from the object.

[0003] For example, in a device for detecting objects by means of Time of Flight (TOF), a technique is disclosed that uses a moving average of the signal level of the reflected wave to reduce the impact of noise caused by reflected waves from the road surface (Patent Document 1).

[0004] Patent Document 1: Japanese Patent Application Publication No. 2006-292597

[0005] In driving assistance systems, road condition information (TOF) corresponding to the road surface is sometimes used to monitor road conditions. The acquired road information is typically transmitted via a data bus or other transmission path to external devices such as the ECU (Electronic Control Unit) that analyzes the road information. However, if the amount of road information is too large relative to the transmission capacity of the transmission path, the road information may not be effectively utilized. Summary of the Invention

[0006] Therefore, one of the objectives of this invention is to provide an object detection device that can effectively utilize road surface information.

[0007] As an example of the present invention, an object detection device detects objects around a moving object moving on a road surface using a Time-of-Flight (TOF) method. The device is characterized by comprising: a first acquisition unit that acquires object information containing distance information of the detected object based on a comparison between the signal level of a reflected wave and a first threshold; a second acquisition unit that acquires road surface information containing distance information of the road surface based on a comparison between the signal level of a reflected wave and a second threshold; and a setting unit that sets the second threshold to ensure that the amount of distance information acquired within a specified period does not exceed a predetermined amount.

[0008] Based on the above structure, the amount of road surface information can be controlled within an appropriate range. Therefore, road surface information can be used effectively.

[0009] Alternatively, the object detection device may also be configured to include an output unit that outputs road surface information to an external device via a transmission path, with the specified amount set to not exceed the transmission capacity of the transmission path.

[0010] Based on the above structure, the amount of information about the road surface can be adapted to the transmission capacity of the transmission path.

[0011] Alternatively, the first threshold can be set based on road surface information.

[0012] Based on the above structure, a first threshold for detecting the target object can be appropriately set according to the road conditions and other information obtained based on road surface information.

[0013] Alternatively, the second acquisition unit may acquire road surface information when the first acquisition unit does not process the acquisition object information.

[0014] Based on the above structure, the first threshold can be appropriately set based on road surface information without processing the acquisition of object information.

[0015] Alternatively, the second threshold can be configured to alternate between an upper value and a lower value that is less than the upper value over time, so that road surface information is not obtained during the period corresponding to the upper value, but during the period corresponding to the lower value.

[0016] As described above, the wave shape of the second threshold is alternating between upper and lower values, thereby adjusting the amount of information obtained from the road surface.

[0017] Alternatively, the specified period can be configured to correspond to a strong reflection range where the signal level of the reflected wave from the road surface is relatively high within the detectable distance range.

[0018] The strong reflection range is determined by the design conditions of the object detection device (e.g., the setting angle of the signal transceiver, the directivity of the transmitted wave, etc.) and can be predetermined. By setting the specified period for acquiring road surface information to correspond to this strong reflection range, road surface information can be acquired efficiently. Attached Figure Description

[0019] Figure 1 This is a top view showing an example of the appearance of a vehicle equipped with the vehicle control system according to the implementation method.

[0020] Figure 2 This is a block diagram illustrating an example of the hardware structure of the ECU and object detection device involved in the implementation.

[0021] Figure 3 This is a diagram illustrating an example of an object detection method based on the TOF method described in the implementation.

[0022] Figure 4 This is a block diagram illustrating an example of the functional structure of the ECU and object detection device involved in the implementation.

[0023] Figure 5 This is a diagram illustrating an example of a method for setting a road surface threshold according to an implementation method.

[0024] Figure 6 This is a flowchart illustrating an example of the processing of the ECU and object detection device involved in the implementation.

[0025] Explanation of reference numerals in the attached figures

[0026] 1…Vehicle; 2…Vehicle body; 3F…Front wheel; 3R…Rear wheel; 100…ECU; 200, 201-204…Object detection device; 110…Input / output device; 120…Storage device; 130…Processor; 210…Signal transceiver; 211…Oscillator; 220…Control unit; 221…Input / output device; 222…Storage device; 223…Processor; 300…Data bus (transmission path); 501…Envelope processing unit; 502… 503… Object threshold setting unit; 504… Road surface threshold setting unit (setting unit); 505… Object information acquisition unit (first acquisition unit); 506… Road surface information acquisition unit (second acquisition unit); 511… Output unit; 512… Input unit; 513… Threshold control unit; L11, L31… Envelope; L21… Object threshold; L41… Road surface threshold; O… Obstacle; RS… Road surface; Ts… Specified period; V1… Upper value; V2… Lower value Detailed Implementation

[0027] The embodiments of this disclosure will now be described with reference to the accompanying drawings. The structure of the embodiments described below, and the functions and effects produced by such structure, are merely examples, and the present invention is not limited to the following description.

[0028] Figure 1 This is a top view showing an example of the appearance of a vehicle 1 equipped with the vehicle control system according to the embodiment. Vehicle 1 is an example of a moving body moving on a road surface. The vehicle control system illustrated below is a system that uses a time-of-flight (TOF) method with ultrasonic waves to detect objects present around vehicle 1 and controls the vehicle based on the detection results.

[0029] like Figure 1 As shown, the vehicle control system includes: an ECU 100, which is installed inside a vehicle 1 having a pair of front wheels 3F and a pair of rear wheels 3R; and object detection devices 201 to 204 installed on the exterior of the vehicle 1.

[0030] exist Figure 1 In the example shown, the object detection devices 201 to 204 are installed at different positions on the rear end of the vehicle body 2, which is an external component of the vehicle 1 (e.g., the rear bumper).

[0031] In this embodiment, the object detection devices 201 to 204 have the same hardware structure and function. Therefore, for the sake of simplicity, the object detection devices 201 to 204 will sometimes be collectively referred to as object detection device 200.

[0032] Furthermore, in this embodiment, the placement location of the object detection device 200 is not limited to [specific location]. Figure 1 The example shown illustrates this. The object detection device 200 can also be installed at the front end of the vehicle body 2 (e.g., the front bumper), on the side of the vehicle body 2, or at two or more locations selected from the rear end, front end, and side. Furthermore, the number of object detection devices 200 is not limited to [specific number missing]. Figure 1 The example shown.

[0033] Figure 2 This is a block diagram illustrating an example of the hardware structure of the ECU100 and the object detection device 200 involved in the implementation.

[0034] like Figure 2 As shown, the ECU 100 has the same hardware structure as a typical computer. Specifically, the ECU 100 includes an input / output device 110, a storage device 120, and a processor 130.

[0035] Input / output device 110 enables communication between ECU 100 and external devices (in... Figure 1 The example shown illustrates the interface for information transmission and reception between the object detection device 200 and the ECU 100. The input / output device 110 transmits and receives information via the data bus 300 (transmission path) that electrically connects the ECU 100 and the object detection device 200.

[0036] Storage device 120 includes main storage devices such as ROM (Read Only Memory) and RAM (Random Access Memory), and / or auxiliary storage devices such as HDD (Hard Disk Drive) and SSD (Solid State Drive).

[0037] The processor 130 controls various processes executed in the ECU 100. The processor 130 contains a computing device such as a CPU (Central Processing Unit). The processor 130 reads and executes programs stored in the storage device 120 to implement various functions such as automatic operation and alarm output.

[0038] The object detection device 200 includes a signal transceiver unit 210 and a control unit 220.

[0039] The signal transceiver unit 210 includes a piezoelectric element or similar vibrator 211, through which ultrasonic waves are transmitted and received. Specifically, the signal transceiver unit 210 transmits ultrasonic waves generated by the vibration of the vibrator 211 as transmitted waves, and receives the vibration of the vibrator 211 as reflected waves, resulting from the reflection of the transmitted ultrasonic waves from an external object. Figure 2 In the example, an obstacle O set on the road surface RS is shown as the object to be detected.

[0040] In addition, Figure 2 The example illustrates a structure in which a single signal transceiver unit 210 having a single oscillator 211 transmits a transmitted wave and receives a reflected wave, but the implementation is not limited to this. For example, it could be a structure in which a first oscillator for transmitting a transmitted wave and a second oscillator for receiving a reflected wave are separately provided, thus separating the transmitting side structure and the receiving side structure.

[0041] The control unit 220 has the same hardware structure as a typical computer. Specifically, the control unit 220 includes an input / output device 221, a storage device 222, and a processor 223.

[0042] Input / output device 221 is used to connect the control unit 220 to external devices (in...) Figure 2 The example shown is the interface for information transmission and reception between ECU100 and signal transceiver 210. Input / output device 221 transmits and receives information via data bus 300.

[0043] Storage device 222 includes main storage devices such as ROM and RAM, and / or auxiliary storage devices such as HDD and SSD.

[0044] The processor 223 controls various processes executed in the control unit 220. The processor 223 includes an arithmetic unit such as a CPU. The processor 223 reads and executes programs stored in the storage device 333 to implement various functions.

[0045] The object detection device 200 of this embodiment detects the distance to objects (e.g., other vehicles, road obstacles, people, etc.) existing around the vehicle 1 using the Time-of-Flight (TOF) method. The TOF method is a technique that calculates the distance to an object based on the difference between the time point when the transmitted wave is sent (more specifically, the start of transmission) and the time point when the reflected wave is received (more specifically, the start of reception).

[0046] Figure 3 This diagram illustrates an example of an object detection method based on the Time-of-Flight (TOF) approach described in the implementation. More specifically, Figure 3This is a graph illustrating, in chart form, the time-varying changes in the signal level (e.g., amplitude) of the ultrasonic waves transmitted and received by the object detection device 200. Figure 3 In the chart shown, the horizontal axis corresponds to time, and the vertical axis corresponds to the signal level of the signals transmitted and received by the object detection device 200 via the signal transceiver unit 210 (oscillator 211).

[0047] exist Figure 3 In the diagram shown, the envelope L11, represented by a solid line, illustrates an example of the time-varying signal level of the signals transmitted and received by the object detection device 200, i.e., the degree of vibration of the oscillator 211. From this envelope L11, it can be read that the oscillator 211 is driven to vibrate for a time Ta starting from time point t0, completes the transmission of the transmitted wave at time point t1, and then continues to vibrate based on inertia during the time period Tb up to time point t2. Therefore, in Figure 3 In the chart shown, time Tb corresponds to the so-called reverberation time.

[0048] For envelope L11, at time point t4 after time Tp from the start of wave transmission t0, the vibration of oscillator 211 reaches a peak exceeding (or exceeding) the object threshold L21 (first threshold) indicated by the dotted line. This object threshold L21 is a value set to distinguish whether the vibration of oscillator 211 is caused by receiving reflected waves from a detected object (e.g., obstacle O) or by receiving reflected waves from an object outside the detected object (e.g., road surface RS).

[0049] In addition, Figure 3 The example shown is that the object threshold L21 is set as a constant value that does not change over time. The object threshold L21 can also be set as a value that changes with the passage of time.

[0050] Here, vibrations with a peak value exceeding (or greater than) the object threshold L21 can be considered as generated by receiving reflected waves from the detected object. On the other hand, vibrations with a peak value below (or less than) the object threshold L21 can be considered as generated by receiving reflected waves from an object other than the detected object. Therefore, the vibration of oscillator 211 at time point t4 can be read from the envelope L11 as generated by receiving reflected waves from the detected object.

[0051] Furthermore, in the envelope L11, the vibration of oscillator 211 decays after time point t4. Therefore, time point t4 corresponds to the time point at which the reception of the reflected wave from the detected object is completed, in other words, the time point at which the transmitted wave last sent at time point t1 returns as a reflected wave.

[0052] Furthermore, in envelope L11, time point t3, which is the starting point of the peak value in time point t4, corresponds to the time point at which the reflected wave from the detected object begins to be received; in other words, it corresponds to the time point at which the transmitted wave initially sent at time point t0 returns as a reflected wave. Therefore, in envelope L11, the time ΔT between time point t3 and time point t4 is equal to the time Ta, which is the transmission time of the transmitted wave.

[0053] Based on the above, in order to determine the distance to the detected object using the Time-of-Flight (TOF) method, it is necessary to calculate the time Tf between the time point t0 when the transmitted wave begins to be sent and the time point t3 when the reflected wave begins to be received. This time Tf can be obtained by subtracting the time ΔT, which is equal to the transmission time Ta, from the time Tp, which is the difference between time point t0 and the peak time t4 when the signal level of the received reflected wave exceeds the threshold.

[0054] The time point t0 at which the transmitted wave begins can be easily determined as the time point at which the object detection device 200 starts operating, and the transmission time Ta of the transmitted wave is predetermined by setting, etc. Therefore, in order to calculate the distance to the detected object using the TOF method, it is only necessary to determine the time point t4 at which the signal level of the reflected wave exceeds the object threshold L21 and reaches its peak.

[0055] Figure 4 This is a block diagram illustrating an example of the functional structure of the ECU100 and the object detection device 200 involved in the implementation.

[0056] The object detection device 200 includes an envelope processing unit 501, an object threshold setting unit 502, a road surface threshold setting unit 503 (setting unit), an object information acquisition unit 504 (first acquisition unit), a road surface information acquisition unit 505 (second acquisition unit), and an output unit 506. These functional units 501 to 506 are comprised of... Figure 2 The control unit 220 shown is configured by the cooperation of its hardware structure and the program stored in the storage device 222.

[0057] The envelope processing unit 501 generates an envelope representing the time-varying signal level of the reflected wave based on the signal obtained from the signal transceiver unit 210.

[0058] The object threshold setting unit 502 sets an object threshold (e.g., envelope L11) for obtaining object information containing distance information (TOF) of the detected object (e.g., obstacle O) based on the envelope (e.g., envelope L11) generated by the envelope processing unit 501. Figure 3 The object threshold L21 shown is the first threshold.

[0059] The road surface threshold setting unit 503 sets a road surface threshold (second threshold) for obtaining road surface information containing distance information corresponding to the road surface based on the envelope generated by the envelope processing unit 501. The method for setting the road surface threshold will be described later.

[0060] The object information acquisition unit 504 acquires object information containing distance information of the detected object based on the comparison result between the signal level of the reflected wave represented by the envelope (e.g., envelope L11) generated by the envelope processing unit 501 and the object threshold (e.g., object threshold L21) set by the object threshold setting unit 502.

[0061] The road surface information acquisition unit 505 acquires road surface information containing road surface distance information based on the comparison result between the signal level of the reflected wave represented by the envelope (shown later) generated by the envelope processing unit 501 and the road surface threshold (shown later) set by the road surface threshold setting unit 503.

[0062] The output unit 506 outputs object information obtained by the object information acquisition unit 504 and road information obtained by the road information acquisition unit 504 to the ECU 100 via the data bus 300.

[0063] ECU 100 includes an input unit 511, a threshold control unit 512, and a driving control unit 513. These functional units 511 to 513 are comprised of... Figure 2 The ECU100 shown is constructed by the combination of its hardware structure and the program stored in the storage device 120.

[0064] The input unit 511 inputs object information and road surface information output from the output unit 506 of the object detection device 200 via the data bus 300.

[0065] The threshold control unit 512 performs processing to control the object threshold setting unit 502 and the road surface threshold setting unit 503 based on the object information and road surface information input by the input unit 511. The threshold control unit 512 also performs processing to set an object threshold L21 adapted to road surface conditions (e.g., gradient, road surface roughness, etc.) based on the road surface information. The threshold control unit 512 outputs control signals for controlling the object threshold setting unit 502 and for controlling the road surface threshold setting unit 503 via the data bus 300.

[0066] The driving control unit 513 performs processing to control the vehicle 1 based on the object information and road information input by the input unit 511.

[0067] Figure 5 This diagram illustrates an example of a method for setting the road surface threshold L41 according to the implementation method. Figure 5The diagram illustrates the time-varying envelope L31 representing the signal level of the reflected wave from the road surface RS, and the road surface threshold L41.

[0068] Road surface information is acquired when the signal level of envelope L31 exceeds (or becomes higher than) the road surface threshold L41. In this embodiment, the road surface threshold L41 is set such that the amount of road surface information acquired within a specified period Ts does not exceed a specified amount.

[0069] The aforementioned specified amount is set to not exceed the transmission capacity of the data bus 300 (e.g., the amount of information that can be transmitted per unit time). That is, road surface information is obtained within the range not exceeding the transmission capacity of the data bus 300. As a result, the road surface information can be appropriately transmitted to the ECU 100 and utilized effectively.

[0070] The road surface threshold L41 in this embodiment varies in a wave shape (rectangular wave) by alternately repeating the upper value V1 and the lower value V2 according to time elapsed within a specified period Ts. Road surface information is not obtained within the period corresponding to the upper value V1, but within the period corresponding to the lower value V2. In this embodiment, 8 pieces of road surface information are obtained within the specified period Ts. Furthermore, the upper value V1 and the lower value V2 may not be fixed values. For example, in environments with high noise levels, the lower value V2 can be arbitrarily set so that the lower value V2 can be set to be greater than the noise level. In addition, echoes from distant sources with small reflections from obstacles can be regarded as noise data, and the lower value V2 can be adaptively varied based on the average value or the average value + α.

[0071] The preferred specified period Ts is a period corresponding to a strong reflection range where the signal level of the reflected wave from the road surface RS increases relatively within the distance range where the object detection device 200 can detect the object. The strong reflection range is determined by the design conditions of the object detection device 200 (e.g., the setting angle of the signal transceiver unit 210, the directivity of the transmitted wave, etc.) and can be predetermined. By setting the specified period Ts for acquiring road surface information to a period corresponding to the strong reflection range, road surface information can be acquired efficiently. Furthermore, the specified period Ts can also be variable.

[0072] Figure 6 This is a flowchart illustrating an example of the processing of the ECU100 and object detection device 200 according to the embodiment. The threshold control unit 512 determines whether obstacle detection for detecting the object is being performed (S101). If obstacle detection is being performed (S101: Yes), the object information acquisition unit 504 acquires object information based on the object threshold L21 (S107), and then executes step S101 again.

[0073] If obstacle detection is not in progress (S101: No), the threshold control unit 512 outputs an indication signal to the road surface threshold setting unit 503, and the road surface threshold setting unit 503 sets the road surface threshold L41 according to the indication signal (S102). Then, the road surface information acquisition unit 505 acquires road surface information based on the set road surface threshold L41 (S103), and the output unit 506 outputs the acquired road surface information to the ECU 100 via the data bus 300 (S104). The threshold control unit 512 sets the object threshold L21 based on the road surface conditions (gradient, road surface roughness, etc.) inferred from the road surface information to reduce the influence of the road surface RS (S105). Then, step S101 is executed again.

[0074] The programs that enable processors 130, 223, etc., to perform various functions in the above embodiments can be provided as installable or executable files recorded on computer-readable recording media such as CD (Compact Disc)-ROM, floppy disk (FD), CD-R (Recordable), and DVD (Digital Versatile Disk). Alternatively, the program can also be provided or distributed via a network such as the Internet.

[0075] According to the above implementation method, the amount of road surface information and the transmission capability of the data bus 300 can be integrated, and the road surface information can be effectively utilized.

[0076] The embodiments of this disclosure have been described above, but these embodiments are merely examples and are not intended to limit the scope of the invention. The new embodiments described above can be implemented in various ways, and various omissions, substitutions, and changes can be made without departing from the spirit of the invention. The embodiments described above are included within the scope and spirit of the invention, and are also included within the scope of the invention as described in the claims and its equivalents.

Claims

1. An object detection device that uses Time-of-Flight (TOF) to detect objects around a moving object on a road surface, characterized in that, Possessing: a first acquisition section that acquires object information containing distance information of a detection object based on a comparison result of a signal level of a reflected wave and a first threshold value; a second acquisition section that acquires road surface information containing distance information of a road surface based on a comparison result of a signal level of a reflected wave and a second threshold value; a setting section that sets the second threshold value so that an information amount of the distance information acquired within a prescribed period does not exceed a prescribed amount; and an output section that outputs the road surface information to an external device via a transmission path, the prescribed amount is set so as not to exceed a transmission capacity of the transmission path.

2. The object detection device according to claim 1, characterized in that the first threshold value is set based on the road surface information.

3. The object detection device according to claim 2, characterized in that the second acquisition section acquires the road surface information in a case where the first acquisition section does not perform processing of acquiring the object information.

4. The object detection device according to any one of claims 1 to 3, characterized in that the second threshold value is varied in a manner that alternately repeats an upper value and a lower value that is smaller than the upper value over time, the road surface information is not acquired within a period corresponding to the upper value, and is acquired within a period corresponding to the lower value.

5. The object detection device according to any one of claims 1 to 3, characterized in that the prescribed period is a period corresponding to a strong reflection range in which the signal level of the reflected wave from the road surface within a detectable distance range becomes high.

6. The object detection device according to claim 4, characterized in that the prescribed period is a period corresponding to a strong reflection range in which the signal level of the reflected wave from the road surface within a detectable distance range becomes high.

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