Object detection device

Abstract

To provide an object detection device capable of suppressing erroneous detection of an obstacle.SOLUTION: An object detection device detects an obstacle present in the vicinity of a moving body based on time-series changes in the intensity of a reflected wave generated when a transmission wave transmitted from the moving body is reflected by an object. The object detection device includes a threshold calculation unit that calculates a variable threshold that varies in accordance with the movement of the moving body based on a moving average value of the intensity of the reflected wave, and a determination unit that determines that an obstacle is present when the intensity of the reflected wave is greater than a predetermined fixed threshold and the variable threshold.SELECTED DRAWING: Figure 4

Description

Technical Field

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

Background Art

[0002] In a moving body such as a vehicle, an object detection device that detects obstacles existing around the moving body based on information such as TOF (Time Of Flight) and Doppler shift obtained by transmitting and receiving ultrasonic waves or the like is used. In such an object detection device, CFAR (Constant False Alarm Rate) processing is used as a technique for suppressing the influence of noise from objects that are not detection targets (for example, road surfaces and the like). According to CFAR processing, a threshold value for determining whether the object that is the reflection source of the reflected wave is an obstacle is optimized according to the state of the road surface and the like based on the moving average value of the intensity of the reflected wave that changes over time.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] According to the above-described CFAR processing, basically, the influence of noise can be suppressed, but depending on the situation, there is a possibility of being easily affected by noise. For example, if the road surface on which the moving body is traveling is in a smooth state, the threshold value will be set low. Therefore, if a non-obstacle such as a small step suddenly appears on the road surface in such a state, the intensity of the reflected wave from the non-obstacle is likely to exceed the threshold value. In such a case, there is a high possibility of being erroneously determined that an obstacle exists even though there is no obstacle.

[0005] The present invention has been made in view of the above, and provides an object detection device capable of suppressing false detection of obstacles. [Means for solving the problem]

[0006] An object detection device according to one aspect of the present invention is an object detection device that detects obstacles present around a moving object based on the time-series change in the intensity of reflected waves generated when transmitted waves from a moving object are reflected by an object, and comprises a threshold calculation unit that calculates a fluctuation threshold that changes according to the movement of the moving object based on the moving average value of the intensity of the reflected waves, and a determination unit that determines that an obstacle is present when the intensity of the reflected waves is greater than a predetermined fixed threshold and a fluctuation threshold. [Effects of the Invention]

[0007] According to the present invention, it is possible to provide an object detection device that can suppress false detection of obstacles. [Brief explanation of the drawing]

[0008] [Figure 1] Figure 1 shows an example of the configuration of a vehicle according to the first embodiment. [Figure 2] Figure 2 shows an example of the configuration of a vehicle control system according to the first embodiment. [Figure 3] Figure 3 shows an example of a distance calculation method using the TOF method according to the first embodiment. [Figure 4] Figure 4 shows an example of the functional configuration of the object detection device according to the first embodiment. [Figure 5] Figure 5 shows an example of CFAR processing according to the first embodiment. [Figure 6] Figure 6 shows an example of a fixed threshold according to the first embodiment. [Figure 7] Figure 7 shows an example of the CFAR threshold in the first embodiment when an obstacle is present. [Figure 8] Figure 8 shows an example of a CFAR threshold in the first embodiment when no obstacles are present. [Figure 9] Figure 9 shows an example of the relationship between the envelope, fixed threshold, and CFAR threshold when an obstacle is present in the first embodiment. [Figure 10] Figure 10 shows an example of the relationship between the envelope, fixed threshold, and CFAR threshold in the first embodiment when no obstacles are present. [Figure 11] Figure 11 is a flowchart showing an example of processing in the object detection device according to the first embodiment. [Figure 12] Figure 12 shows an example of the relationship between the envelope, fixed threshold, and CFAR threshold in the second embodiment when an obstacle is present. [Figure 13] Figure 13 shows an example of the relationship between the envelope, fixed threshold, and CFAR threshold in the second embodiment when no obstacles are present. [Figure 14] Figure 14 is a flowchart showing an example of processing in the object detection device according to the second embodiment. [Figure 15] Figure 15 shows an example of the functional configuration of an object detection device according to the third embodiment. [Figure 16] Figure 16 shows an example of the relationship between the envelope, fixed threshold, and CFAR threshold in the third embodiment when an obstacle is present. [Figure 17] Figure 17 is a flowchart showing an example of processing in the object detection device according to the third embodiment. [Modes for carrying out the invention]

[0009] Embodiments of the present invention will be described below with reference to the drawings. The configurations of the embodiments described below, as well as the functions and effects brought about by such configurations, are examples only, and the present invention is not limited to the contents described below.

[0010] (First Embodiment) FIG. 1 is a diagram showing an example of the configuration of a vehicle 1 according to the first embodiment. The vehicle 1 is an example of a moving body on which the object detection device according to the present embodiment is mounted. The object detection device according to the present embodiment is a device that detects obstacles existing around the vehicle 1 based on information such as TOF (Time Of Flight) and Doppler shift obtained by transmitting and receiving ultrasonic waves.

[0011] The object detection device according to the present embodiment includes a plurality of transmission / reception units 21A to 21L. Hereinafter, when it is not necessary to distinguish the plurality of transmission / reception units 21A to 21L, they may be described as the transmission / reception unit 21. Each transmission / reception unit 21 is installed on the vehicle body 2 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 existing outside the vehicle body 2. Hereinafter, the ultrasonic wave transmitted from the transmission / reception unit 21 may be described as a transmission wave, and the ultrasonic wave generated by the reflection of the transmission wave by an object may be described as a reflected wave.

[0012] In the example shown in FIG. 1, four transmission / reception units 21A to 21D are arranged at the front end portion of the vehicle body 2, four transmission / reception units 21E to 21H are arranged at the rear end portion, two transmission / reception units 21I and 21J are arranged on the right side surface, and two transmission / reception units 21K and 21L are arranged on the left side surface. Note that the number and installation positions of the transmission / reception units 21 are not limited to this example.

[0013] FIG. 2 is a diagram showing an example of the configuration of a vehicle control system 10 according to the first embodiment. The vehicle control system 10 performs processing for controlling the vehicle 1 based on information output from the object detection device 11. The vehicle control system 10 according to the present embodiment includes the object detection device 11 and the ECU 12.

[0014] The object detection device 11 includes a plurality of transmitting / receiving units 21 and a control unit 22. Each transmitting / receiving unit 21 includes a transducer 31 constructed using a piezoelectric element, an amplifier, etc., and transmits and receives ultrasonic waves by the vibration of the transducer 31. Specifically, each transmitting / receiving unit 21 transmits ultrasonic waves generated in response to the vibration of the transducer 31 as a transmitted wave, and detects the vibration of the transducer 31 caused by the reflected wave when the transmitted wave is reflected by an object such as an obstacle O or the road surface G. The obstacle O is an object that is to be detected among the objects present around the vehicle 1, and may be, for example, another vehicle, road fixtures, a wall, a person, a curb, a wheel stop, etc. The vibration of the transducer 31 is converted into an electrical signal, and based on the electrical signal, the time-of-flight (TOF) corresponding to the distance from the transmitting / receiving unit 21 to the obstacle O, the Doppler shift corresponding to the relative speed between the vehicle 1 and the obstacle O, etc., can be obtained.

[0015] In the example shown in Figure 2, a configuration is illustrated in which both the transmission of the transmitted wave and the reception of the reflected wave are performed using a single oscillator 31. However, the configuration of the transmitting and receiving unit 21 is not limited to this. For example, the transmitting side and the receiving side may be separated, such as a configuration in which an oscillator for transmitting the transmitted wave and an oscillator for receiving the reflected wave are provided separately.

[0016] The control unit 22 includes an input / output device 41, a storage device 42, and a processor 43. The input / output device 41 is an interface device that enables the transmission and reception of information between the control unit 22 and external devices (transmit / receive unit 21, ECU 12, etc.). The storage device 42 includes main memory such as ROM (Read Only Memory) and RAM (Random Access Memory), and auxiliary storage such as HDD (Hard Disk Drive) and SSD (Solid State Drive). The processor 43 is an integrated circuit that performs various processes to realize the functions of the control unit 22, and can be configured using, for example, a CPU (Central Processing Unit), ASIC (Application Specific Integrated Circuit), FPGA (Field Programmable Gate Array), etc. that operate according to a program. The processor 43 performs various arithmetic and control processes by reading and executing programs stored in the storage device 42.

[0017] The ECU 12 is a unit that performs various processes for controlling the vehicle 1 based on information acquired from the object detection device 11, etc. The ECU 12 has an input / output device 51, a storage device 52, and a processor 53. The input / output device 51 is an interface device that enables the transmission and reception of information between the ECU 12 and external mechanisms (object detection device 11, drive mechanism, braking mechanism, steering mechanism, transmission mechanism, in-vehicle display, speaker, various sensors, etc.). The storage device 52 includes main memory such as ROM and RAM, and auxiliary storage such as HDD and SSD. The processor 53 is an integrated circuit that performs various processes to realize the functions of the ECU 12, and can be configured using, for example, a CPU, ASIC, FPGA, etc. The processor 53 reads the program stored in the storage device 52 and performs various arithmetic and control processes.

[0018] Figure 3 shows an example of a distance calculation method using the TOF method according to the first embodiment. Figure 3 illustrates an envelope L showing the change over time in the intensity (signal level) of the ultrasonic waves transmitted and received by the transmitting / receiving unit 21. In the graph shown in Figure 3, the horizontal axis corresponds to time (TOF), and the vertical axis corresponds to the intensity of the ultrasonic waves transmitted and received by the transmitting / receiving unit 21 (magnitude of vibration of the transducer 31).

[0019] The envelope L shows the change in intensity over time, which indicates the magnitude of the vibration of the oscillator 31. From the envelope L illustrated in Figure 3, it can be seen that the oscillator 31 is driven and vibrates for time Ta from timing t0, so that the transmission of the transmitted wave is completed at timing t1, and then the vibration of the oscillator 31 due to inertia continues to decay for time Tb until timing t2. Therefore, in the graph shown in Figure 3, time Tb corresponds to the so-called reverberation time.

[0020] The envelope L reaches a peak at timing t4, which is time Tp after the start of transmission of the transmitted wave at timing t0, when the amplitude of the oscillator 31's vibration reaches a threshold Th or greater. This threshold Th is a value set to distinguish whether the vibration of the oscillator 31 is caused by the reception of reflected waves from an obstacle O or by the reception of reflected waves from an object other than the obstacle O (e.g., the road surface G). Although the threshold Th is shown as a constant value here, the threshold Th may be a variable value that changes depending on the situation. Vibrations with a peak greater than or equal to the threshold Th can be considered to be caused by the reception of reflected waves from the obstacle O.

[0021] In this example, the envelope L shows that the oscillation of oscillator 31 is attenuated after timing t4. Therefore, timing t4 corresponds to the timing when the reception of the reflected wave from the obstacle O is completed, or in other words, the timing when the last transmitted wave sent at timing t1 returns as a reflected wave.

[0022] Furthermore, in the envelope L, timing t3, which is the starting point of the peak at timing t4, corresponds to the timing when the reception of the reflected wave from the obstacle O begins, in other words, the timing when the transmitted wave initially sent 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.

[0023] From the above, in order to determine the distance from the transmitting / receiving unit 21, which is the source of the ultrasonic waves, to the obstacle O using TOF, it is necessary to determine the time Tf between the timing t0 when the transmitted wave begins to be sent and the timing t3 when the reflected wave begins to be received. This time Tf can be determined by subtracting a time ΔT, which is equal to the transmission time Ta of the transmitted wave, from the time Tp, which is the difference between timing t0 and timing t4 when the intensity of the reflected wave exceeds the threshold Th and reaches its peak.

[0024] The timing t0 at which the transmitted wave begins to be sent can be easily identified as the timing at which the object detection device 200 starts operating, and the transmission time Ta of the transmitted wave is predetermined by settings, etc. Therefore, by identifying the timing t4 at which the intensity of the reflected wave reaches a peak above the threshold Th, the distance from the vehicle 1 (the transmitting / receiving unit 21, which is the source of the ultrasonic waves) to the obstacle O can be determined. Note that the above calculation method is an example, and the distance from the vehicle 1 to the obstacle O can be calculated using any known or novel method as appropriate.

[0025] Figure 4 shows an example of the functional configuration of the object detection device 11 according to the first embodiment. The control unit 22 of the object detection device 11 according to this embodiment includes an echo information generation unit 101, a threshold calculation unit 102, a determination unit 103, and an output unit 104. These functional units can be realized, for example, through the cooperation of the hardware and software (program, etc.) of the object detection device 11 as shown in Figure 2. In addition, at least a part of these functional units may be realized by dedicated hardware (circuits).

[0026] The echo information generation unit 101 generates echo information showing the time-series change in the intensity of the reflected wave based on the information acquired from the transmitting / receiving unit 21. The echo information may include data of the envelope L, as illustrated in Figure 3.

[0027] The threshold calculation unit 102 calculates a CFAR threshold (an example of a fluctuating threshold) that changes according to the movement of the vehicle 1 by performing CFAR processing on the echo information. The threshold calculation unit 102 calculates a moving average value of the intensity of the reflected wave based on the echo information and calculates the CFAR threshold based on the moving average value.

[0028] The determination unit 103 determines whether or not an obstacle exists around the vehicle 1 based on the echo information, a predetermined fixed threshold, and a CFAR threshold calculated by the threshold calculation unit 102. In this embodiment, the determination unit 103 determines that an obstacle exists if the intensity of the reflected wave is greater than the fixed threshold and the CFAR threshold. If the determination unit 103 determines that an obstacle exists, it generates obstacle information related to the obstacle. The obstacle information may include, for example, the distance from the vehicle 1 (transmitting / receiving unit 21) to the obstacle, the relative speed of the obstacle, etc.

[0029] The output unit 104 outputs the obstacle information generated by the determination unit 103 to a predetermined mechanism (for example, the ECU 12).

[0030] Figure 5 shows an example of CFAR processing according to the first embodiment. In the CFAR processing illustrated here, first, a received signal indicating the intensity of the reflected wave is sampled from the echo information at predetermined time intervals. Then, the first sum Σ1 is calculated, which is the sum of the intensity values ​​of N samples of reflected waves received in the first period Δt1 before a certain detection timing t. Also, the second sum Σ2 is calculated, which is the sum of the intensity values ​​of N samples of reflected waves received in the second period Δt2 after the detection timing t. Then, the sum Σ obtained by adding the first sum Σ1 and the second sum Σ2 is divided by 2N, which is the sum of the number of samples N in the first period Δt1 and the number of samples N in the second period Δt2, to calculate the moving average value A. Then, the CFAR threshold Thc is calculated by applying predetermined integration processing, addition processing, etc., to the moving average value A. Integration processing is the process of integrating a predetermined constant with the moving average value A. Addition processing is the process of adding a predetermined constant with the moving average value A. Then, using a difference signal that shows the difference between the intensity value corresponding to the detection timing t and the CFAR threshold Thc, it is determined whether or not an obstacle exists at the distance corresponding to the detection timing t.

[0031] The method for calculating the CFAR threshold Thc is not limited to the above. For example, the above description explains the CA (Cell Averaging)-CFAR process, in which the moving average A is the average of all values ​​corresponding to the periods Δt1 and Δt2 before and after the detection timing t. However, the CFAR threshold Thc may also be calculated by GO (Greatest Of)-CFAR process or SO (Smallest Of)-CFAR process, etc. GO-CFAR process calculates the moving average A using the larger of the first sum Σ1 and the second sum Σ2. SO-CFAR process calculates the moving average A using the smaller of the first sum Σ1 and the second sum Σ2.

[0032] Figure 6 shows an example of a fixed threshold Thf according to the first embodiment. In Figure 6, the envelope L and the fixed threshold Thf are illustrated in the case of an obstacle. The peak P1 in the envelope L is due to a reflected wave from an obstacle located at a distance D1 from the vehicle 1 (transceiver 21).

[0033] The fixed threshold Thf is a fixed value uniquely determined for the distance from vehicle 1. The fixed threshold Thf may be pre-stored in a suitable memory device (e.g., memory device 42) installed in vehicle 1. The specific method for setting the fixed threshold Thf should be determined appropriately according to the specifications of vehicle 1 and the performance of the transmitting / receiving unit 21, but the fixed threshold Thf can be set, for example, based on statistical values ​​(e.g., lower limit) of the intensity of reflected waves from obstacles for each distance. Since the intensity of reflected waves from obstacles decreases as the distance from vehicle 1 increases, the fixed threshold Thf is usually set to decrease as the distance from vehicle 1 increases. Here, a fixed threshold Thf that decreases linearly with increasing distance is given as an example, but the form of the fixed threshold Thf is not limited to this.

[0034] Figure 7 shows an example of the CFAR threshold Thc in the first embodiment when an obstacle is present. In Figure 7, the envelope L, the moving average value A of the envelope L, and the CFAR threshold Thc are illustrated when an obstacle is present.

[0035] The CFAR threshold Thc exemplified here is a value obtained by integrating it with the moving average value A of the envelope L (intensity of reflected waves). The moving average value A and the CFAR threshold Thc fluctuate according to the undulations of the road surface, etc., when vehicle 1 is driving. The intensity of reflected waves from obstacles (peak P1) is usually greater than the CFAR threshold Thc.

[0036] By using the CFAR threshold Thc described above, the effects of noise caused by road surface irregularities and other factors can generally be suppressed, but there is a possibility that the system may become more susceptible to noise in certain situations.

[0037] Figure 8 shows an example of the CFAR threshold Thc in the first embodiment when no obstacles are present. In Figure 8, the envelope L, the moving average value A of the envelope L, and the CFAR threshold Thc are illustrated when no obstacles are present. The peak P2 in the envelope L is due to reflected waves from a non-obstacle object (e.g., a small bump on the road surface) located at a distance D2 from the vehicle 1. The CFAR threshold Thc illustrated here is a value obtained by integrating the moving average value A of the envelope L, similar to Figure 7.

[0038] The CFAR threshold Thc is low when the road surface remains smooth for a certain period of time. However, when a small bump or other non-obstacle appears on such a road surface, the intensity of the reflected wave from that non-obstacle (peak P2) may become higher than the low-set CFAR threshold Thc, as shown in Figure 8.

[0039] As described above, if the presence or absence of an obstacle is determined using only the CFAR threshold Thc, it may be susceptible to noise depending on the road surface conditions, potentially leading to false detection of obstacles. Therefore, in this embodiment, the presence or absence of an obstacle is determined using both a fixed threshold Thf and a CFAR threshold Thc.

[0040] Figure 9 shows an example of the relationship between the envelope L, the fixed threshold Thf, and the CFAR threshold Thc in the presence of an obstacle in the first embodiment. In Figure 9, a state is illustrated in which the peak P1 corresponding to the intensity of the reflected wave from the obstacle exceeds both the fixed threshold Thf and the CFAR threshold Thc.

[0041] In this embodiment, as illustrated in Figure 9, an obstacle is determined to be present when the intensity of the reflected wave is greater than the fixed threshold Thf and the CFAR threshold Thc.

[0042] Figure 10 shows an example of the relationship between the envelope L, the fixed threshold Thf, and the CFAR threshold Thc in the absence of obstacles in the first embodiment. In Figure 10, the peak P2 corresponding to the intensity of the reflected wave from the non-obstructive source is shown to be greater than the CFAR threshold Thc but less than the fixed threshold Thf.

[0043] In this embodiment, as illustrated in Figure 10, if the intensity of the reflected wave is less than at least one of the fixed threshold Thf or the CFAR threshold Thc, the presence of an obstacle is not determined.

[0044] Figure 11 is a flowchart showing an example of processing in the object detection device 11 according to the first embodiment. In step S101, when the transmitting / receiving unit 21 starts transmitting and receiving ultrasonic waves, in step S102, the echo information generation unit 101 generates echo information showing the time-series change in the intensity of reflected waves from objects present around the vehicle 1. In step S103, the threshold calculation unit 102 calculates the CFAR threshold Thc based on the echo information.

[0045] In step S104, the determination unit 103 determines whether the intensity I of the reflected wave obtained from the echo information is greater than the fixed threshold Thf (I>Thf) and whether the intensity I is greater than the CFAR threshold Thc (I>Thc).

[0046] In step S104, if I > Thf and I > Thc are not met (S104: No), that is, if the intensity I of the reflected wave is less than at least one of the fixed threshold Thf or the CFAR threshold Thc, it is determined that no obstacle exists and this routine terminates.

[0047] In step S104, if I > Thf and I > Thc (S104: Yes), in step S105, the determination unit 103 determines that an obstacle exists and generates obstacle information related to that obstacle. In step S106, the output unit 104 outputs the obstacle information to a mechanism such as the ECU 12.

[0048] As described above, according to this embodiment, an obstacle is determined to be present when the intensity of the reflected wave is greater than both the fixed threshold and the CFAR threshold. This makes it possible to reduce the possibility of false detection of obstacles when the CFAR threshold is set low.

[0049] Other embodiments will be described below with reference to the drawings, but descriptions of parts that are the same as or similar to those in the first embodiment will be omitted as appropriate.

[0050] (Second Embodiment) In the second embodiment, the object detection device 11 determines that an obstacle is present if the intensity of the reflected wave is greater than a fixed threshold within a predetermined short-range area, and determines that an obstacle is present if the intensity of the reflected wave is greater than both the fixed threshold and the CFAR threshold within a range farther than the short-range area.

[0051] Figure 12 shows an example of the relationship between the envelope L, the fixed threshold Thf, and the CFAR threshold Thc in the second embodiment when an obstacle is present. Figure 13 shows an example of the relationship between the envelope L, the fixed threshold Thf, and the CFAR threshold Thc in the second embodiment when no obstacle is present. In Figures 12 and 13, the short-range range Rn is exemplified. The short-range range Rn should be set appropriately according to the specifications of the vehicle 1 and the performance of the transmitting / receiving unit 21, but it may be, for example, within 1 m from the vehicle 1 (transmitting / receiving unit 21).

[0052] In this embodiment, within the short-range range Rn, the CFAR threshold Thc is not considered, and the presence or absence of an obstacle is determined based on whether the intensity of the reflected wave is greater than or equal to the fixed threshold Thf. In the example shown in Figure 12, since the peak P1 appearing within the short-range range Rn exceeds the fixed threshold Thf, it is determined that an obstacle is present.

[0053] Furthermore, in this embodiment, in regions farther than the short-range Rn, the presence or absence of an obstacle is determined based on both the fixed threshold Thf and the CFAR threshold Thc, similar to the first embodiment. In the example shown in Figure 13, the peak P2 appearing in the region farther than the short-range Rn exceeds the CFAR threshold Thc, but does not exceed the fixed threshold Thf, so it is determined that no obstacle exists.

[0054] Figure 14 is a flowchart showing an example of processing in the object detection device 11 according to the second embodiment. In step S201, when the transmitting / receiving unit 21 starts transmitting and receiving ultrasonic waves, in step S202, the echo information generation unit 101 generates echo information showing the time-series change in the intensity of reflected waves from objects present around the vehicle 1. In step S203, the threshold calculation unit 102 calculates the CFAR threshold Thc based on the echo information.

[0055] In step S204, the determination unit 103 determines whether the intensity I of the reflected wave obtained from the echo information is greater than the fixed threshold Thf (I>Thf). In step S204, if I>Thf is not present (S204:No), it is determined that no obstacle exists, and this routine terminates.

[0056] In step S204, if I > Thf (S204: Yes), in step S205, the determination unit 103 determines whether the distance corresponding to the peak determined to be I > Thf is within the short-range range Rn. In step S205, if the distance is not within the short-range range Rn (S205: No), in step S206, the determination unit 103 determines whether the intensity I of the reflected wave is greater than the CFAR threshold Thc (I > Thc). In step S206, if I > Thc is not present (S206: No), it is determined that no obstacle exists, and this routine terminates.

[0057] In step S205, if it is determined that the distance is within the short-range range Rn (S205:Yes), or in step S206, if it is determined that I > Thc (S206:Yes), in step S207, the determination unit 103 determines that an obstacle exists and generates obstacle information regarding the obstacle. In step S208, the output unit 104 outputs the obstacle information to a mechanism such as the ECU 12.

[0058] As described above, according to this embodiment, within a predetermined short-range area, an obstacle is determined to be present if the intensity of the reflected wave is greater than a fixed threshold, and in areas farther than the short-range area, an obstacle is determined to be present if the intensity of the reflected wave is greater than both the fixed threshold and the CFAR threshold. This is because, within the short-range area, the fixed threshold can be set with relatively high accuracy, and there is little need to use the CFAR threshold. In this way, by limiting the range in which the CFAR threshold is used, the processing load required for calculating the CFAR threshold can be reduced.

[0059] (Third embodiment) Figure 15 shows an example of the functional configuration of the object detection device 11 according to the third embodiment. As shown in Figure 15, the control unit 22 of the object detection device 11 in this embodiment includes a reliability determination unit 201 in addition to the echo information generation unit 101, threshold calculation unit 102, determination unit 103, and output unit 104 described above.

[0060] The reliability determination unit 201 determines the reliability of the determination result (obstacle information) from the determination unit 103 based on the difference between the intensity of the reflected wave corresponding to the obstacle and a fixed threshold Thf, and generates reliability information indicating the reliability.

[0061] In this embodiment, the output unit 104 associates the obstacle information generated by the determination unit 103 with the reliability information generated by the reliability determination unit 201 and outputs it to a mechanism such as the ECU 12.

[0062] Figure 16 shows an example of the relationship between the envelope L, the fixed threshold Thf, and the CFAR threshold Thc in the third embodiment when an obstacle is present. In Figure 16, the difference ΔI between the intensity of the reflected wave of peak P1 corresponding to the obstacle and the fixed threshold Thf is illustrated.

[0063] The reliability determination unit 201 of this embodiment determines the reliability of the obstacle information relating to the obstacle corresponding to peak P1 based on the difference ΔI between the intensity of peak P1 that satisfies the conditions for being determined to be an obstacle (in this case, the intensity of the reflected wave being greater than the fixed threshold Thf and the CFAR threshold Thc) and the fixed threshold Thf. This reliability can be determined such that, for example, it increases as the difference ΔI increases.

[0064] Figure 17 is a flowchart showing an example of processing in the object detection device 11 according to the third embodiment. In step S301, when the transmitting / receiving unit 21 starts transmitting and receiving ultrasonic waves, in step S302, the echo information generation unit 101 generates echo information showing the time-series change in the intensity of reflected waves from objects present around the vehicle 1. In step S303, the threshold calculation unit 102 calculates the CFAR threshold Thc based on the echo information.

[0065] In step S304, the determination unit 103 determines whether the intensity I of the reflected wave obtained from the echo information is greater than the fixed threshold Thf (I>Thf) and whether the intensity I is greater than the CFAR threshold Thc (I>Thc).

[0066] In step S304, if I > Thf and I > Thc are not met (S304: No), that is, if the intensity I of the reflected wave is less than at least one of the fixed threshold Thf or the CFAR threshold Thc, it is determined that no obstacle exists and this routine terminates.

[0067] In step S304, if I > Thf and I > Thc (S304: Yes), in step S305, the determination unit 103 determines that an obstacle exists and generates obstacle information regarding the obstacle. In step S306, reliability information indicating the reliability of the obstacle information (obstacle information generated in step S305) is generated based on the difference ΔI between the intensity I (intensity of the reflected wave satisfying the conditions in step S304) and the fixed threshold Thf. In step S306, the output unit 104 outputs the obstacle information and reliability information to a device such as the ECU 12.

[0068] As described above, according to this embodiment, reliability information indicating the reliability of obstacle information is generated based on the difference between the intensity of the reflected wave and a fixed threshold. By utilizing such reliability information, it becomes possible to control the vehicle 1 based on obstacle information with higher accuracy.

[0069] (modified version) In the embodiments described above, a configuration using ultrasound as the wave transmitted and received to detect obstacles was illustrated, but the configuration of the object detection device is not limited to this. For example, a configuration using millimeter-wave radar, LiDAR (Light Detection And Ranging) sensors, etc., may also be used.

[0070] Furthermore, while the above-described embodiment assumes that the reflected wave is a direct wave transmitted and received by the same transmitting / receiving unit 21, the reflected wave may be an indirect wave in which a transmitted wave transmitted from one transmitting / receiving unit 21 (e.g., transmitting / receiving unit 21E) is received by another transmitting / receiving unit 21 (e.g., transmitting / receiving unit 21F). In this case, at least one of the fixed threshold or the CFAR threshold may be changed depending on whether the reflected wave is a direct wave or an indirect wave.

[0071] The program that causes a computer (e.g., processor 43) to execute the processing necessary to realize the functions of the object detection device described above can be provided as an installable or executable file recorded on a computer-readable recording medium such as a CD (Compact Disc)-ROM, flexible disk (FD), CD-R (Recordable), or DVD (Digital Versatile Disk). Furthermore, the program may be provided or distributed via a network such as the Internet.

[0072] Although embodiments of the present invention have been described above, the embodiments and their modifications described herein are merely examples and are not intended to limit the scope of the invention. The novel embodiments and modifications described herein can be implemented in various forms, and various omissions, substitutions, and modifications can be made without departing from the spirit of the invention. The embodiments and modifications described herein are included in the scope and spirit of the invention, as well as in the claims of the invention and its equivalents. [Explanation of symbols]

[0073] 1...Vehicle (moving object), 11...Object detection device, 21, 21A~21L...Transmitting / receiving unit, 102...Threshold calculation unit, 103...Determination unit, 201...Reliability determination unit, O...Obstacle, Thc...CFAR threshold (variable threshold), Thf...Fixed threshold

Claims

1. An object detection device for detecting obstacles present around a moving object based on the time-series change in the intensity of reflected waves generated when transmitted waves from a moving object are reflected by an object, A threshold calculation unit calculates a fluctuation threshold that changes according to the movement of the moving body based on the moving average value of the intensity of the reflected wave, A determination unit that determines the presence of an obstacle when the intensity of the reflected wave is greater than a predetermined fixed threshold and a variable threshold, An object detection device equipped with the following features.

2. The determination unit determines that an obstacle exists if the intensity of the reflected wave is greater than the fixed threshold within a predetermined short-range area, and determines that an obstacle exists if the intensity of the reflected wave is greater than both the fixed threshold and the variable threshold within a range greater than the short-range area. The object detection device according to claim 1.

3. A reliability determination unit that determines the reliability of the determination result by the determination unit based on the difference between the intensity of the reflected wave and the fixed threshold, The object detection device according to claim 1 or 2, further comprising:

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