Object detection device

Abstract

To provide an object detection device which is modified so as to be capable of estimating positions of two objects even when the strength of indirect waves which are reflected waves of waves having been simultaneously transmitted by two sonars and reflected by objects is intensified in a state where two objects to be detected exist.SOLUTION: Provided is an object detection device in which, among sonars A to C disposed in an outer circumferential section of a vehicle 102 while spaced apart from each other, the sonars A and C transmit sound waves simultaneously and receive direct waves reflected by objects, and the sonar B receives an indirect wave reflected by an object. In a state where the sonars A and C receive direct waves and the sonar B receives an indirect wave, positions of objects present in a detection range of each of the sonars A and C are estimated on the basis of a flight time of the direct waves received by the sonars A and C and a flight time of the indirect wave received by the sonar B when a peak value of the indirect wave received by the sonar B is greater than or equal to a predetermined magnification Yamax with respect to peak values of the direct waves received by the sonars A and C.SELECTED DRAWING: Figure 5

Description

Technical Field

[0001] The present invention relates to an object detection device for vehicles such as automobiles.

Background Art

[0002] An object detection device for vehicles such as automobiles includes at least two sonars and a control unit that controls those sonars. A direct wave, which is ultrasonic waves transmitted by one sonar and reflected by an object, is received by one sonar, and an indirect wave, which is ultrasonic waves reflected by the object, is received by the other sonar. The control unit estimates the position of the object that reflected the direct wave and the indirect wave, that is, the distance between the object and the vehicle and the direction of the object with respect to the vehicle, based on the flight times of the direct wave and the indirect wave.

[0003] When there are multiple reflected waves reflected by an object and the multiple reflected waves overlap with each other with their phases shifted, the wave height value of the indirect wave decreases due to the cancellation of the reflected waves, and the object cannot be detected. As one of the object detection devices for dealing with this problem, for example, in Patent Document 1 below, an object detection device in which the symbol discrimination performance of the reflected wave is improved by ultrasonic waves encoded by frequency modulation and pulse compression processing is described.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

[0005] 〔Problems to be Solved by the Invention〕 In order to widen the detection range of an object and improve the detection efficiency of the object, it is conceivable to provide at least three sonars, transmit ultrasonic waves simultaneously by two sonars to receive the direct wave, and receive the indirect wave by the remaining sonar.

[0006] However, if the flight times of the two ultrasonic waves transmitted by two sonars and received by the remaining sonar are the same, and the phases of the two indirect waves when the remaining sonar receives them are in phase or nearly in phase, constructive interference between the two indirect waves occurs. As a result, only one indirect wave is received by the remaining sonar, and even if there are two objects to be detected, only the position of one object may be detected. Conventional object detection devices, such as the object detection device described in Patent Document 1, cannot resolve the above problem caused by the constructive interference between the two indirect waves.

[0007] The present invention provides an improved object detection device that can estimate the positions of two objects even when constructive interference occurs between indirect waves, which are reflected waves transmitted simultaneously by two sonars and reflected by the objects, in a situation where two objects to be detected are present.

[0008] [Means for solving the problem and the effects of the invention] According to the present invention, an object detection device (100) is provided, comprising: first to third sonars arranged spaced apart from each other on the outer periphery of a vehicle (102) such that a third sonar (B) is positioned between first and second sonars (A, C); and a control unit (driving support ECU 10) for controlling the first to third sonars, wherein the first and second sonars are configured to simultaneously transmit sound waves and receive direct waves, which are sound waves reflected by an object; the third sonar is configured to receive indirect waves, which are sound waves transmitted by the first and second sonars and reflected by an object; and the control unit is configured to estimate the position of an object that reflected the direct and indirect waves based on the time of flight of the direct and indirect waves.

[0009] The control unit (driving support ECU 10) is configured such that, in a situation where the first and second sonars (A, C) receive direct waves and the third sonar (B) receives indirect waves, if the wave height of the indirect waves received by the third sonar is greater than or equal to a predetermined multiplier (Yamax) of the wave height of the direct waves received by the first and second sonars (S40), it estimates the position of an object within the detection range of the first sonar based on the flight time of the direct waves received by the first sonar (A) and the flight time of the indirect waves received by the third sonar (B) (S60), and also estimates the position of an object within the detection range of the second sonar based on the flight time of the direct waves received by the second sonar (C) and the flight time of the indirect waves received by the third sonar (S60).

[0010] According to the above configuration, in a situation where the first and second sonars receive direct waves and the third sonar receives indirect waves, if the wave height of the indirect waves received by the third sonar is greater than or equal to a predetermined multiplier of the wave height of the direct waves received by the first and second sonars, the position of the object is estimated as follows: That is, the position of the object within the detection range of the first sonar is estimated based on the flight time of the direct waves received by the first sonar and the flight time of the indirect waves received by the third sonar. Also, the position of the object within the detection range of the second sonar is estimated based on the flight time of the direct waves received by the second sonar and the flight time of the indirect waves received by the third sonar.

[0011] Therefore, in a situation where there are two objects to be detected, even if the two indirect waves transmitted by the first and second sonars and received by the third sonar combine into one due to constructive interference, the positions of the two objects can still be estimated.

[0012] [Aspects of the Invention] In one embodiment of the present invention, the control unit (driving support ECU 10) is configured such that, in a situation where the first and second sonars (A, C) receive direct waves and the third sonar (B) receives indirect waves, if the wave height of the indirect waves received by the third sonar is less than a predetermined multiplier (Yamax) of the wave height of the direct waves received by the first and second sonars, the control unit (driving support ECU 10) estimates which of the first and second sonars corresponds to the indirect waves received by the third sonar (S80, S110), and estimates the position of an object within the detection range of the estimated sonar based on the flight time of the direct waves received by the estimated sonar and the flight time of the indirect waves received by the third sonar (S90, S120).

[0013] In another embodiment of the present invention, the first and second sonars (A, C) are configured to transmit sound waves encoded into different codes by frequency modulation, and the control unit (driving support ECU 10) is configured to estimate the sonar corresponding to the indirect wave received by the third sonar (B) based on the code of the indirect wave received by the third sonar (S80, S110).

[0014] Furthermore, in another embodiment of the present invention, the control unit (driving support ECU 10) is configured to estimate the position of an object within the detection range of one sonar based on the flight time of the direct wave received by one sonar and the flight time of the indirect wave received by the third sonar (S70, S100) when only one of the first and second sonars receives a direct wave and the third sonar receives an indirect wave (S90, S120).

[0015] Furthermore, in another embodiment of the present invention, the overlapping area (S) is defined as the range in which the detection area by direct waves received by the first sonar (A) and the detection area by indirect waves received by the third sonar (B) overlap, and the ratio of the distance between any point (X) located within the overlapping area and the first sonar to the distance between any point and the third sonar is defined as a predetermined ratio, where the predetermined magnification is the maximum value of the predetermined ratio.

[0016] Other objects, other features, and attendant advantages of the present invention will be readily understood from the description of embodiments of the present invention described while referring to the following drawings.

Brief Description of the Drawings

[0017] [Figure 1] It is a schematic configuration diagram showing an object detection device according to an embodiment. [Figure 2] It is a diagram showing the order of operation of sonars A to D on the front end side of the embodiment. [Figure 3] It is a diagram showing the situation of reinforcement of indirect waves in the case of two obstacles (A) and the case of one obstacle (B). [Figure 4] It is a diagram showing the wave height values (A, B) of two indirect waves and the wave height value (C) when the indirect waves reinforce each other. [Figure 5] It is a diagram showing case X1 (case 1) where the indirect waves of the ultrasonic waves simultaneously transmitted by sonars A and C reinforce each other and case X2 (case 2) where only the indirect wave of the ultrasonic wave transmitted by one of sonars A and C is received by sonar B. [Figure 6] It is a flowchart showing the first half of the object detection control routine of the embodiment. [Figure 7] It is a flowchart showing the second half of the object detection control routine of the embodiment.

Modes for Carrying Out the Invention

[0018] Hereinafter, an object detection device according to an embodiment of the present invention will be described in detail while referring to the attached drawings.

[0019] As shown in FIG. 1, an object detection device 100 according to an embodiment of the present invention is applied to a vehicle 102 and includes a driving support ECU 10. The vehicle 102 may be a vehicle capable of autonomous driving and includes a driving ECU 20, a braking ECU 30, and a meter ECU 40. ECU means an electronic control unit (Electronic Control Unit) having a microcomputer as a main part.

[0020] The microcomputers of each ECU include a CPU, a ROM, a RAM, a readable and writable non-volatile memory (N / M), and an interface (I / F), etc. The CPU realizes various functions by executing the instructions (programs, routines) stored in the ROM. Further, these ECUs are connected to each other so that data can be exchanged (communication is possible) via a CAN (Controller Area Network) 104. Therefore, the detection values of sensors (including switches) connected to a specific ECU are also transmitted to other ECUs.

[0021] The driving support ECU 10 detects objects such as walls, guardrails, and other vehicles around the vehicle 102, and estimates the position of the object, that is, the distance between the object and the vehicle and the direction of the object with respect to the vehicle. In the embodiment, when the driving support ECU 10 determines in cooperation with other ECUs that the vehicle has approached an object excessively, it issues an alarm indicating that, and controls the driving force and braking force of the vehicle 102 as necessary to prevent the vehicle from colliding with the object.

[0022] Sensors A to D and sensors E to H are connected to the driving support ECU 10, and these sensors are controlled by the driving support ECU 10. As shown in FIG. 2, sensors A to D are arranged on the outer peripheral portion of the front end of the vehicle 102. Sensor B is located between sensor A and sensor C, and sensor C is located between sensor B and sensor D. Although not shown in the figure, sensors E to H are arranged on the outer peripheral portion of the rear end of the vehicle 102. Sensor F is located between sensor E and sensor G, and sensor G is located between sensor F and sensor H.

[0023] Furthermore, the driver assistance ECU 10 is connected to a front-end switch 12F and a rear-end switch 12R. When the front-end switch 12F is ON, the driver assistance ECU 10 controls the front-end sonars A to D, and when the rear-end switch 12R is ON, it controls the rear-end sonars E to H. Note that the front-end switch 12F and the rear-end switch 12R may be integrated into a single switch, in which case the driver assistance ECU 10 controls the front-end sonars A to D and the rear-end sonars E to H when that single switch is ON.

[0024] Each sonar is configured to transmit ultrasonic waves away from the vehicle 102, receive ultrasonic waves transmitted by its own sonar and reflected by objects (i.e., direct waves), and receive ultrasonic waves transmitted by other sonars and reflected by objects (i.e., indirect waves). Each sonar is also configured to output a signal indicating the peak value of the received voltage corresponding to the received ultrasonic waves, and therefore a signal indicating the peak value of the received ultrasonic waves, to the driver assistance ECU 10.

[0025] The driver assistance ECU 10 determines that the corresponding sonar is receiving ultrasonic waves when the wave height value is above a reference value. Therefore, the driver assistance ECU 10 can clearly determine whether or not the sonar is receiving ultrasonic waves. In addition, the driver assistance ECU 10 estimates the distance between the object that reflected the direct and indirect waves and the vehicle 102, as well as the direction of the object relative to the vehicle, based on the flight times of the direct and indirect waves.

[0026] In this embodiment, in order to improve the object detection efficiency, the driver assistance ECU 10 controls the sonars so that in each of the sonar groups A to D on the front end and E to H on the rear end, two sonars simultaneously transmit ultrasonic waves of different frequencies. The operating mode in which two sonars transmit ultrasonic waves simultaneously is called dual mode, and the operating mode in which only one sonar transmits ultrasonic waves is called single mode. When the operating mode is dual mode, as a means of determining which sonar transmitted the ultrasonic waves to which sonar the receiving sonar is receiving indirect waves, means known in the art other than making the frequencies of the ultrasonic waves different by encoding them into different codes by frequency modulation coding may be employed.

[0027] In particular, in the embodiment shown in Figure 2, the driver assistance ECU 10 controls the front-end sonars A to D so that the first and second transmission / reception modes alternate when the front-end switch 12F is ON. In the first transmission / reception mode, sonars A and C simultaneously transmit ultrasonic waves as the first and second sonars, respectively, and receive direct waves, while sonars B and D receive indirect waves, and sonar B functions as a third sonar. In the second transmission / reception mode, sonars B and D simultaneously transmit ultrasonic waves as the first and second sonars, respectively, and receive direct waves, while sonars A and C receive indirect waves, and sonar C functions as a third sonar.

[0028] Similarly, when the rear-end switch 12R is ON, the driver assistance ECU 10 controls the rear-end sonars E to H so that the third and fourth transmission / reception modes alternately repeat. In the third transmission / reception mode, sonars E and G simultaneously transmit ultrasonic waves as the first and second sonars, respectively, and receive direct waves, while sonars F and H receive indirect waves, with sonar F functioning as the third sonar. In the fourth transmission / reception mode, sonars F and H simultaneously transmit ultrasonic waves as the first and second sonars, respectively, and receive direct waves, while sonars E and G receive indirect waves, with sonar G functioning as the third sonar.

[0029] In any of the first to fourth transmission / reception modes, the first and second sonars determine whether the ultrasonic waves reflected by the object are direct or indirect based on their frequencies. The third sonar then determines, based on the frequency of the indirect waves it receives, which sonar transmitted the ultrasonic waves.

[0030] The drive ECU 20 is connected to a drive unit 22, which accelerates the vehicle 102 by applying driving force to the drive wheels, which are not shown in Figure 1. Under normal circumstances, the drive ECU 20 controls the drive unit 22 so that the driving force generated by the drive unit 22 changes in accordance with the driver's driving operation, and when it receives a command signal from the driver assistance ECU 10, it controls the drive unit 22 based on the command signal.

[0031] Furthermore, the drive unit 22 is not limited to a combination of an internal combustion engine and an automatic transmission. That is, the drive unit 22 may be any drive unit known in the art, such as a combination of an internal combustion engine and a continuously variable transmission, a so-called hybrid system consisting of an internal combustion engine and a motor, a so-called plug-in hybrid system, a combination of a fuel cell and a motor, or a motor.

[0032] The braking ECU 30 is connected to a braking device 32 that decelerates the vehicle 102 by applying braking force to the wheels, which are not shown in Figure 1. Under normal circumstances, the braking ECU 30 controls the braking device so that the braking force generated by the braking device 32 changes in accordance with the driver's braking operation. When it receives a command signal from the driver assistance ECU 10, it controls the braking force of each wheel by controlling the braking device 32 based on the command signal.

[0033] A warning device 42 is connected to the meter ECU 40. The warning device 42 is activated when it is determined that the vehicle 102 is approaching an obstacle too closely and is at risk of collision, and issues a warning, that is, a warning that the vehicle 102 is approaching an obstacle too closely and is at risk of collision. The warning device 42 may be any of the following: a visual warning device such as a display or warning lamp, an auditory warning device such as a warning buzzer, or a tactile warning device such as seat vibration, or any combination thereof.

[0034] As described above, the rear-end sonars E through H are controlled in the same way as the front-end sonars A through D, so from here on, only the front-end sonars A through D will be explained.

[0035] As shown in Figure 3(A), the ultrasonic waves transmitted by sonar A are reflected by obstacle 50, and sonar B receives the reflected wave, i.e., the indirect wave. The relationship between the peak value of the received voltage and the TOF (Time of Flight) for the indirect wave is as shown in Figure 4(A). Also, the ultrasonic waves transmitted by sonar C are reflected by obstacle 52, and sonar B receives the reflected wave, i.e., the indirect wave. The relationship between the peak value of the received voltage and the TOF for the indirect wave is as shown in Figure 4(B).

[0036] When sonars A and C simultaneously transmit ultrasonic waves, and the time of flight (TOF) at which the peak value of the indirect wave reaches its peak is the same, and the phase difference between the two indirect waves is 0 degrees or close to it, the two indirect waves reinforce each other. Therefore, the relationship between the peak value of the received voltage of sonar B and the TOF is as shown in Figure 4(C), and sonar B is determined to have received only one indirect wave.

[0037] If one indirect wave is estimated to be an indirect wave of ultrasound transmitted by sonar A, the position of obstacle 50 can be estimated by triangulation based on the time of flight (TOF) of the direct wave received by sonar A and the time of flight of one indirect wave received by sonar B. However, since sonar B is determined not to have received an indirect wave of ultrasound transmitted by sonar C, the position of obstacle 52 cannot be estimated.

[0038] In contrast, if one indirect wave is estimated to be an indirect wave of ultrasound transmitted by sonar C, the position of obstacle 52 can be estimated by triangulation based on the TOF of the direct wave received by sonar C and the TOF of one indirect wave received by sonar B. However, since sonar B is determined not to have received an indirect wave of ultrasound transmitted by sonar A, it cannot estimate the position of obstacle 50.

[0039] [Principle of the present invention] The case in which sonars A and C simultaneously transmit ultrasonic waves, and sonar B receives only one indirect wave, is one of the following cases 1 or 2.

[0040] Case 1 is a case where the indirect ultrasonic waves transmitted simultaneously by sonars A and C reinforce each other, and sonar B receives only one indirect wave (Figure 5(X1)).

[0041] In contrast, Case 2 is a case where only the indirect ultrasonic waves transmitted by one of sonars A and C are received by sonar B, and the obstacle is located outside the detection area of ​​the other sonar A or C. (Figure 5(X2))

[0042] Let S be the range where the detection area of ​​the direct wave received by sonar A and the detection area of ​​the indirect wave received by sonar B overlap. Let X be any point within range S as shown in equation (1) below, and let Ya be the ratio of the distance between point X and sonar B to the distance between point X and sonar A. That is, for ultrasonic waves reflected at point X, the maximum value of the ratio of the wave height of the indirect wave to the wave height of the direct wave is determined in advance as the maximum value of ratio Ya, Yamax, and this is set as the predetermined ratio. Ya = Distance between point X and sonar B / Distance between point X and sonar A …(1)

[0043] If the ratio of the wave height of the indirect wave received by sonar B to the wave height of the direct wave received by sonar A and the wave height of the direct wave received by sonar C are both greater than or equal to a predetermined magnification of Yamax, then it is determined to be Case 1, not Case 2.

[0044] In particular, in this embodiment, if sonars A and C simultaneously transmit direct ultrasonic waves, and sonars A and C receive them respectively, while sonar B receives only one indirect wave, then it is estimated as follows whether the two indirect waves reinforced each other to form a single indirect wave.

[0045] If the wave height of the indirect wave received by sonar B is greater than or equal to a predetermined multiplier (Yamax) of the wave height of the direct wave received by sonars A and C, it is determined that constructive interference of the indirect waves is occurring (Case 1). Then, as shown in Figure 5(X1), the position of obstacle P is estimated based on the TOF of the direct wave received by sonar A and the TOF of the indirect wave received by sonar B. Furthermore, the position of obstacle Q is estimated based on the TOF of the direct wave received by sonar C and the TOF of the indirect wave received by sonar B.

[0046] In contrast, if the wave height of the indirect wave received by sonar B is less than a predetermined magnification Yamax relative to at least one of the wave heights of the direct waves received by sonars A and C, it is determined that no constructive interference of indirect waves is occurring (Case 2). Then, as shown in Figure 5(X2), it is determined, based on the code encoded by frequency modulation, whether the indirect wave received by sonar B is the indirect wave of the ultrasonic wave transmitted by sonar A or C. Then, based on the TOF of the direct wave of the determined sonar and the TOF of the indirect wave received by sonar B, the position of obstacle P is estimated.

[0047] The ROM of the driver assistance ECU 10 stores an obstacle detection control program corresponding to the flowcharts shown in Figures 6 and 7, as an embodiment of the object detection control program. The CPU of the driver assistance ECU 10 executes obstacle detection control according to this obstacle detection program to resolve the problem that when the operating mode is set to dual mode, constructive interference of indirect waves occurs, making it impossible to estimate the position of one of two obstructing objects.

[0048] <Obstacle Detection Control Program> Next, the obstacle detection control program in the embodiment will be described with reference to the flowcharts shown in Figures 6 and 7. The obstacle detection control according to the flowcharts shown in Figures 6 and 7 is repeatedly executed by the CPU of the driver assistance ECU 10 when the front end switch 12F is ON. At the start of the obstacle detection control, the operating mode is set to dual mode.

[0049] First, in step S10, the CPU controls sonars A and C so that they transmit ultrasonic waves simultaneously.

[0050] In step S20, the CPU controls sonars A through D so that sonars A and C receive direct waves, and sonars B and D receive indirect waves.

[0051] In step S30, the CPU determines whether sonars A and C are receiving direct waves. If the CPU determines that it is not receiving direct waves, that is, if at least one of sonars A and C is not receiving direct waves, the control proceeds to step S70. If the CPU determines that it is not receiving direct waves, the control proceeds to step S40.

[0052] In step S40, the CPU determines whether the wave height of the indirect wave received by sonar B is greater than or equal to a predetermined multiplier Yamax relative to the wave height of the direct wave received by sonars A and C. If the CPU determines that this is not the case, i.e., if the wave height of the indirect wave received by sonar B is less than the predetermined multiplier Yamax relative to at least one of the wave heights of the direct wave received by sonars A and C, the control proceeds to step S70. Conversely, if the CPU determines that this is the case, the control proceeds to step S50.

[0053] In step S50, the CPU determines that the indirect wave received by sonar B is the indirect wave of the ultrasonic waves received by sonars A and C, and that the two indirect waves are reinforcing each other.

[0054] In step S60, the CPU estimates the position of obstacle P based on the TOF of the direct wave received by sonar A and the TOF of the indirect wave received by sonar B. Furthermore, the CPU estimates the position of obstacle Q based on the TOF of the direct wave received by sonar C and the TOF of the indirect wave received by sonar B.

[0055] In step S70, the CPU determines whether sonar B is receiving an indirect wave. If the CPU determines it is not receiving an indirect wave, it proceeds to step S100; if it determines it is receiving an indirect wave, it proceeds to step S80.

[0056] In step S80, the CPU estimates whether sonar A or sonar C transmitted the ultrasonic waves that formed the indirect waves, based on the sign of the indirect waves received by sonar B. However, if it is determined in step S30 that sonar C did not receive direct waves, then sonar A may be estimated to be the sonar that transmitted the ultrasonic waves that formed the indirect waves.

[0057] In step S90, the CPU estimates the location of the obstacle based on the TOF of the direct wave received by the estimated sonar and the TOF of the indirect wave received by sonar B. For example, when the estimated sonar is sonar A, the CPU estimates the location of the obstacle based on the TOF of the direct wave received by sonar A and the TOF of the indirect wave received by sonar B.

[0058] In step S100, the CPU determines whether or not sonar D is receiving an indirect wave. If the CPU determines that it is not receiving an indirect wave, it proceeds to step S210; if it determines that it is receiving an indirect wave, it proceeds to step S110.

[0059] In step S110, the CPU estimates whether sonar A or sonar C transmitted the ultrasonic waves that formed the indirect waves, based on the sign of the indirect waves received by sonar D. In step S30, if it is determined that sonar A did not receive direct waves, it may be estimated that sonar C transmitted the ultrasonic waves that formed the indirect waves.

[0060] In step S120, the CPU estimates the position of the obstacle based on the TOF of the direct wave received by the estimated sonar and the TOF of the indirect wave received by sonar B, similar to step S90 described above.

[0061] Next, the CPU executes steps S210 to S330 shown in Figure 7. As can be seen from comparing Figure 7 with Figure 6, steps S210 to S320 are executed in the same way as steps S10 to S120. Therefore, a detailed explanation of steps S210 to S320 is omitted.

[0062] Furthermore, in steps S210, S230 to S260, sonars A and C are replaced by sonars B and D, and in steps S240 to S260, S270, and S290, sonar B is replaced by sonar C. In addition, in steps S300 and S320, sonar D is replaced by sonar A.

[0063] Furthermore, although not shown in the diagram, S is defined as the overlapping range between the detection area of ​​the direct wave received by sonar B and the detection area of ​​the indirect wave received by sonar C. As shown in equation (2) below, any point within range S is denoted as X, and Yb is defined as the ratio of the distance between point X and sonar C to the distance between point X and sonar B. The maximum value of the ratio Yb, Ybmax, is determined in advance and is defined as the predetermined magnification. Yb = Distance between point X and sonar C / Distance between point X and sonar B …(2)

[0064] Furthermore, in step S290, the CPU estimates the position of the obstacle based on the TOF of the direct wave received by the sonar and the TOF of the indirect wave received by sonar C, which were estimated in step S280.

[0065] Furthermore, in step S320, the CPU estimates the position of the obstacle based on the TOF of the direct wave received by the sonar and the TOF of the indirect wave received by sonar A, which were estimated in step S310.

[0066] When the CPU completes steps S260, S290, or S320, in step S330 it outputs information about the location of the obstacle estimated in steps S60, S90, or S120 and S260, S290, or S320 for use in collision detection control, warning control, etc. If a negative determination is made in steps S100 and S300, it is considered that there is no obstacle in the detection area of ​​sonar A to D, so a signal indicating that the presence or absence of an obstacle could not be determined may be output.

[0067] Furthermore, the CPU determines, in a manner known in the art, whether or not there is a risk of the vehicle 102 colliding with an obstacle. If the CPU determines that there is a risk of the vehicle colliding with an obstacle, it outputs a command signal to the drive ECU 20, thereby reducing the output of the drive unit 22 to zero, and outputs a command signal to the brake ECU 30, thereby activating the brake unit 32 to brake the vehicle. Note that the warning device 42 may also be activated, and the reduction of the output of the drive unit 22 and / or braking of the vehicle may be omitted.

[0068] <Operation of the embodiment> As described above, steps S210 to S320 are performed in the same manner as steps S10 to S120, so only steps S10 to S120 will be described in relation to the operation of the embodiment.

[0069] C1: When sonars A and C receive direct waves and the two indirect waves reinforce each other. In steps S30 and S40, a positive determination is made. Therefore, in step S60, the position of the obstacle is estimated based on the TOF of the direct wave received by sonars A and C and the TOF of the indirect wave received by sonar B. Thus, even if there are two obstacles and the indirect waves are combined into one due to constructive interference, the positions of the two obstacles can be estimated.

[0070] C2: Sonars A and C are receiving direct waves, but the two indirect waves are not reinforcing each other. In step S30, an affirmative judgment is made, but in step S40, a negative judgment is made. Therefore, the steps from step S70 onward are executed.

[0071] C3: When at least one of sonars A and C is not receiving a direct wave. In step S30, a negative determination is made. Therefore, in this case as well, the steps from step S70 onward are executed.

[0072] In the case of C2 or C3 above, if sonar B is receiving an indirect wave, a positive determination is made in step S70. Therefore, in step S80, based on the sign of the indirect wave received by sonar B, it is estimated whether sonar A or sonar C is the sonar that transmitted the ultrasonic waves that formed the indirect wave. Furthermore, in step S90, the position of the obstacle is estimated based on the TOF of the direct wave received by the estimated sonar and the TOF of the indirect wave received by sonar B.

[0073] In the case of C2 or C3 above, if sonar B has not received the indirect wave but sonar D has, a negative determination is made in step S70 and an affirmative determination is made in step S100. Therefore, in step S110, based on the sign of the indirect wave received by sonar D, it is estimated whether sonar A or sonar C transmitted the ultrasonic waves that formed the indirect wave. Furthermore, in step S120, the position of the obstacle is estimated based on the TOF of the direct wave received by the estimated sonar and the TOF of the indirect wave received by sonar B.

[0074] Furthermore, in the case of C2 or C3 described above, if sonars B and D are not receiving indirect waves, a negative determination is made in steps S70 and S100. Therefore, it is considered that there are no obstacles in the detection area of ​​sonars A to D, and the location of the obstacle is not estimated.

[0075] In particular, in the embodiment, the maximum values ​​Yamax and Ybmax of the ratios Ya and Yb expressed by equations (1) and (2) are set to a predetermined magnification. Therefore, when an obstacle is present in the detection area of ​​sonar A to D, the position of that obstacle can be estimated.

[0076] Furthermore, constructive interference between the two indirect waves can also occur when there is only one obstacle, for example, as shown in Figure 3(B), when ultrasonic waves transmitted by sonars A and C are reflected by obstacle 54 and received as indirect waves by sonar B. In this case as well, for example, in steps S30 and S40, a positive determination is made and step S60 is executed, but in step S60 the position of the obstacle is estimated to be the same.

[0077] Although the present invention has been described in detail above with respect to specific embodiments, it will be apparent to those skilled in the art that the present invention is not limited to the embodiments described above, and that various other embodiments are possible within the scope of the present invention.

[0078] For example, in this embodiment, the maximum values ​​Yamax and Ybmax of the ratios Ya and Yb expressed by equations (1) and (2) are set as predetermined magnifications. However, the predetermined magnification may be set to values ​​other than the maximum values ​​Yamax and Ybmax.

[0079] In this embodiment, if an affirmative determination is made in step S30, step S40 is executed. However, if an affirmative determination is made in step S30, a determination may be made as to whether or not there is only one indirect wave received by sonar B. If an affirmative determination is made, step S40 is executed, and if a negative determination is made, step S70 is executed.

[0080] Similarly, if a positive determination is made in step S230, a determination is made as to whether or not sonar C receives only one indirect wave. If a positive determination is made, step S240 is executed, and if a negative determination is made, step S270 may be executed.

[0081] Furthermore, in this embodiment, sonars A to D on the front end and sonars E to H on the rear end are received, but sonars A to D on the front end or sonars E to H on the rear end may be omitted.

[0082] Furthermore, in this embodiment, when the front-side switch 12F is ON, the front-side sonars A to D are controlled, and when the rear-side switch 12R is ON, the rear-side sonars E to H are controlled. However, when the vehicle 102 is in a preset driving state, the sonars may be controlled without requiring any switch operation.

[0083] Furthermore, in this embodiment, each sonar is configured to transmit ultrasonic waves, but the transmitted sound waves may have a lower frequency than ultrasonic waves. [Explanation of Symbols]

[0084] 10...Driving assistance ECU, A~H...Sonar, 22...Drive system, 32...Brake system, 42...Warning system, 100...Object detection system, 102...Vehicle

Claims

1. An object detection device comprising: first to third sonars arranged spaced apart from each other on the outer perimeter of a vehicle such that the third sonar is positioned between the first and second sonars; and a control unit for controlling the first to third sonars, wherein the first and second sonars are configured to simultaneously transmit sound waves and receive direct waves, which are sound waves reflected by an object; the third sonar is configured to receive indirect waves, which are sound waves transmitted by the first and second sonars and reflected by an object; and the control unit is configured to estimate the position of an object that reflected the direct waves and indirect waves based on the flight time of the direct waves and indirect waves, An object detection device configured such that, in a situation where the first and second sonars receive direct waves and the third sonar receives indirect waves, the control unit estimates the position of an object within the detection range of the first sonar based on the flight time of the direct waves received by the first sonar and the flight time of the indirect waves received by the third sonar, when the wave height of the indirect waves received by the third sonar is greater than or equal to a predetermined multiplier of the wave height of the direct waves received by the first and second sonars, and estimates the position of an object within the detection range of the second sonar based on the flight time of the direct waves received by the second sonar and the flight time of the indirect waves received by the third sonar.

2. An object detection device according to claim 1, wherein the control unit is configured such that, in a situation where the first and second sonars receive direct waves and the third sonar receives indirect waves, when the wave height of the indirect waves received by the third sonar is less than the predetermined multiplier to the wave height of the direct waves received by the first and second sonars, the control unit estimates which of the first and second sonars corresponds to the indirect waves received by the third sonar, and estimates the position of an object within the detection range of the estimated sonar based on the flight time of the direct waves received by the estimated sonar and the flight time of the indirect waves received by the third sonar.

3. An object detection device according to claim 2, wherein the first and second sonars are configured to transmit sound waves encoded into different codes by frequency modulation, and the control unit is configured to estimate the sonar corresponding to the indirect wave received by the third sonar based on the code of the indirect wave received by the third sonar.

4. An object detection device according to claim 1, wherein the control unit is configured to estimate the position of an object within the detection range of the first sonar when only one of the first and second sonars receives direct waves and the third sonar receives indirect waves, based on the flight time of the direct waves received by the first sonar and the flight time of the indirect waves received by the third sonar.

5. An object detection device according to any one of claims 1 to 4, wherein the overlapping area is defined as the range in which the detection area by direct waves received by the first sonar and the detection area by indirect waves received by the third sonar B overlap, and the ratio of the distance between any point in the overlapping area and the first sonar to the distance between any point and the third sonar is defined as a predetermined ratio, and the predetermined magnification is the maximum value of the predetermined ratio.

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