Object detection device

Abstract

To provide an object detection device widening an object detection range and increasing object detection efficiency by including at least three sonars, transmitting ultrasonic waves simultaneously by two sonars and receiving direct waves, and receiving indirect waves by the remaining sonar.SOLUTION: An object detection device (100) includes a driving support ECU 10 for controlling sonars A-C disposed apart from one another on an outer peripheral part of a vehicle 102. The sonars A and C transmit sonic waves and receive direct waves, which is the sonic waves reflected by an object. The sonar B receives indirect waves, which is the sonic waves reflected by the object. The driving support ECU 10 estimates a distance between the object and the vehicle, and a direction of the object relative to the vehicle based on flight time of the direct waves and the indirect waves. In a situation where the sonars A and C transmit the sonic waves (S20), when the sonars A and C receive the direct waves and the sonar B does not receive the indirect waves (S60), only one of the sonars A and C transmits the sonic waves (S90).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 distance between the object that reflected the direct wave and the indirect wave 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 a plurality of reflected waves reflected by an object and the plurality of reflected waves overlap 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, Patent Document 1 below describes an object detection device in which the code discrimination performance of the reflected wave is improved by ultrasonic waves encoded by frequency modulation and pulse compression processing.

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 out of phase or nearly out of phase, the two indirect waves will cancel each other out. As a result, the peak value of the received voltage of the two indirect waves will be low, which may lead to a false determination that no object is present. Conventional object detection devices, such as the object detection device described in Patent Document 1, cannot resolve the above problem caused by the cancellation of the two indirect waves.

[0007] The present invention provides an improved object detection device that can determine the presence or absence of an object even when indirect waves, which are reflected waves transmitted simultaneously by two sonars and reflected by an object, cancel each other out. [Means for solving the problem and the effects of the invention]

[0008] According to the present invention, an object detection device (100) is provided which includes 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) that controls the first to third sonars, wherein the first and second sonars are configured to transmit sound waves and receive direct waves, which are sound waves reflected by an object, and 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 distance between the object that reflected the direct and indirect waves and the vehicle, and the direction of the object relative to the vehicle, based on the flight time of the direct and indirect waves (S30).

[0009] Each sonar (A-C) is configured to output a signal indicating the peak value of the received sound wave to the control unit (driving support ECU 10). The control unit is configured to determine that the corresponding sonar is receiving a sound wave when the peak value is above a reference value, and to determine that the corresponding sonar is not receiving a sound wave when the peak value is below the reference value. The control unit (driving support ECU10) is, FurthermoreWhen the operating mode is set to dual mode and sound waves are being transmitted by the first and second sonars (S20), if the first and second sonars receive direct waves and the third sonar does not receive indirect waves (S60), the operating mode is set to single mode (S70) and sound waves are transmitted by only one of the first and second sonars (S90).

[0010] According to the above configuration, when the first and second sonars receive direct waves and the third sonar does not receive indirect waves, the operating mode is set to single mode, and sound waves are transmitted by only one of the first and second sonars. Therefore, by transmitting sound waves by only one of the first and second sonars, the cancellation of indirect waves is eliminated, and the presence or absence of an object can be determined based on the direct and indirect waves of the sound waves transmitted by only one of the sonars.

[0012] [Aspects of the Invention] This invention one In one embodiment, the control unit (driving support ECU 10) sets the reliability of object detection based on the peak value of the sound waves received by each sonar (A to C), and in a situation where the operating mode is set to single mode (S10), when one sonar receives a direct wave (S110) and the third sonar receives an indirect wave of the sound wave transmitted by the first sonar (S130), the control unit (driving support ECU 10) is configured to set the same reliability of object detection as when the operating mode is set to dual mode and the third sonar receives an indirect wave of the sound waves transmitted by the first and second sonars (S60) (S150).

[0013] Furthermore, in another embodiment of the present invention, the control unit (clearance CU10) is configured to return to dual mode (S140) when the operating mode is set to single mode (S10), and one sonar receives a direct wave (S110) and the third sonar does not receive an indirect wave of sound waves transmitted by the first sonar (S1320).

[0014] Furthermore, in another embodiment of the present invention, the control unit (driving support ECU 10) is configured to use the sonar that is closer to the object among the first and second sonars (A, C) as one of the sonars (S90).

[0015] Other objects, features, and associated advantages of the present invention will be readily apparent from the description of embodiments of the present invention, which will be described with reference to the following drawings. [Brief explanation of the drawing]

[0016] [Figure 1] This is a schematic diagram showing an object detection device according to an embodiment. [Figure 2] This figure shows the operation sequence of sonars A to D on the front end of the embodiment. [Figure 3] This diagram shows the cancellation of indirect waves in the case of one obstacle (A) and the case of two obstacles (B). [Figure 4] This figure shows the peak values ​​of two indirect waves (A, B) and the peak value (C) when the indirect waves cancel each other out. [Figure 5] This is a flowchart showing the first half of the object detection control routine in the embodiment. [Figure 6] This flowchart shows the latter half of the object detection control routine in the embodiment. [Modes for carrying out the invention]

[0017] The object detection device according to an embodiment of the present invention will be described in detail below with reference to the attached figures.

[0018] 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. An ECU means an electronic control unit (Electronic Control Unit) having a microcomputer as a main part.

[0019] The microcomputer of each ECU includes a CPU, a ROM, a RAM, a readable and writable non-volatile memory (N / M), an interface (I / F), and the like. The CPU realizes various functions by executing instructions (programs, routines) stored in the ROM. Further, these ECUs are connected to each other via a CAN (Controller Area Network) 104 so as to be able to exchange data (communicate). Therefore, detection values of sensors (including switches) connected to a specific ECU are also transmitted to other ECUs.

[0020] The driving support ECU 10 detects objects such as walls, guardrails, and other vehicles around the vehicle 102, and estimates the distance between the vehicle and the object 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.

[0021] 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 disposed 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 disposed 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.

[0022] Furthermore, a front-end side switch 12F and a rear-end side switch 12R are connected to the driving support ECU 10. When the front-end side switch 12F is on, the driving support ECU 10 controls the front-end side sonars A to D, and when the rear-end side switch 12R is on, the driving support ECU 10 controls the rear-end side sonars E to H. Note that the front-end side switch 12F and the rear-end side switch 12R may be integrated into one switch. In this case, when the one switch is on, the driving support ECU 10 controls the front-end side sonars A to D and the rear-end side sonars E to H.

[0023] Each sonar transmits ultrasonic waves in a direction away from the vehicle 102, and is configured to receive the ultrasonic waves transmitted by its own sonar and reflected by an object, that is, the direct wave, and also receive the ultrasonic waves transmitted by other sonars and reflected by an object, that is, the indirect wave. Further, each sonar is configured to output a signal indicating the peak value of the received voltage corresponding to the received ultrasonic waves, that is, a signal indicating the peak value of the received ultrasonic waves, to the driving support ECU 10.

[0024] The driving support ECU 10 determines that the corresponding sonar is receiving ultrasonic waves when the peak value is greater than or equal to the reference value. Furthermore, if the wave height is below the standard value, the corresponding sonar determines that it is not receiving sound waves. Therefore, the driving support ECU 10 can clearly determine whether a sonar is receiving ultrasonic waves. Also, the driving support ECU 10 estimates the distance between the object that reflected the direct wave and the indirect wave and the vehicle 102 and the direction of the object with respect to the vehicle based on the flight times of the direct wave and the indirect wave. Further, the driving support ECU 10 sets the reliability of detecting an object based on the peak values of the direct wave and the indirect wave received by each sonar. By determining whether the wave height value is above the standard value,

[0025] In this embodiment, to improve 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, in addition to differentiating the ultrasonic frequencies, other means known in the art, such as frequency modulation, may be used to determine which sonar transmitted the ultrasonic wave to which sonar the receiving sonar is receiving.

[0026] 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.

[0027] 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.

[0028] 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.

[0029] 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.

[0030] 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.

[0031] 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.

[0032] 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.

[0033] 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.

[0034] 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 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 for the indirect wave is as shown in Figure 4(B).

[0035] When the time of failure (TOF) at which the peak value of the ultrasonic indirect waves transmitted by sonars A and C reaches its peak is the same, and the phase difference between the two indirect waves is 180 degrees or close to it, the two indirect waves cancel each other out. 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 not to have received any indirect waves, so the obstacle 50 is not detected.

[0036] Cancellation of indirect waves can occur even when there are multiple obstacles. As shown in Figure 3(B), assume that ultrasonic waves transmitted by sonar A are reflected by obstacle 52, and sonar B receives the reflected wave, i.e., the indirect wave, and the relationship between the peak value of the received voltage and the time-of-flight (TOF) for that indirect wave is as shown in Figure 4(A). Also assume that ultrasonic waves transmitted by sonar C are reflected by obstacle 54, and sonar B receives the reflected wave, i.e., the indirect wave, and the relationship between the peak value of the received voltage and the TOF for that indirect wave is as shown in Figure 4(B).

[0037] In this case as well, when the phase difference between the two indirect waves is 180 degrees or close to it, the two indirect waves cancel each other out. 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 not to be receiving any indirect waves, so obstacles 52 and 54 are not detected.

[0038] The ROM of the driver assistance ECU 10 stores an obstacle detection control program corresponding to the flowcharts shown in Figures 5 and 6, 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 in order to resolve the problem that, when the operating mode is set to dual mode, indirect waves cancel each other out, and obstacles may not be detected.

[0039] <Obstacle Detection Control Program> Next, the obstacle detection control program in the embodiment will be described with reference to the flowcharts shown in Figures 5 and 6. The obstacle detection control according to the flowcharts shown in Figures 5 and 6 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 flags Fac and Fbd, described later, are reset to off so that the operating mode is set to dual mode.

[0040] First, in step S10, the CPU determines whether the flag Fac is off, that is, whether the operating mode is dual mode. If the CPU determines it is negative, it proceeds to step S90; if it determines it is positive, it proceeds to step S20.

[0041] In step S20, the CPU controls sonars A through C in the first transmit / receive mode so that sonars A and C simultaneously transmit ultrasonic waves as the first and second sonars, respectively, and sonar B functions as the third sonar.

[0042] In step S30, the CPU estimates the distance between one or more obstacles and the vehicle 102, and the direction of the obstacles relative to the vehicle, based on the TOF of the direct waves received by sonars A and C and the TOF of the indirect waves received by sonar B, in a manner known in the art. In this case, if the wave height of the direct or indirect waves is less than a reference value, the distance and direction are not estimated.

[0043] In step S40, the CPU determines whether the wave height of the direct wave received by sonars A and C is equal to or greater than a reference value (a positive constant). If the CPU determines that it is correct, it proceeds to step S60; if it determines that it is incorrect, it proceeds to step S50.

[0044] In step S50, if the CPU has detected an obstacle whose distance and direction were estimated in step S30 up to the previous cycle, it reduces the confidence level of the detection of that obstacle by subtracting 1. Conversely, if there are no obstacles whose distance and direction were estimated in step S30 up to the previous cycle, no reduction in confidence level is performed.

[0045] In step S60, the CPU determines whether the peak value of the received voltage of the indirect wave received by sonar B is equal to or greater than a reference value. If the CPU determines that it is not true, in step S70, it sets the flag Fac to on; if it determines that it is true, it proceeds to step S80.

[0046] In step S80, the CPU increases the detection confidence by adding 1 to the distance and direction of the obstacle estimated in step S30.

[0047] In step S90, the CPU controls one of the sonars A and C so that only one of them transmits ultrasonic waves, and sonar B functions as a receiving sonar. In this case, the one of the sonars is determined to be the one between sonars A and C that is closer to the obstacle, based on the estimated distance.

[0048] In step S100, the CPU estimates the distance between the obstacle and the vehicle 102 and the direction of the obstacle relative to the vehicle, based on the TOF of the direct wave received by one sonar and the TOF of the indirect wave received by sonar B, in a manner known in the art. As in step S30, if the wave height of the direct or indirect wave is less than a reference value, the distance and direction are not estimated.

[0049] In step S110, the CPU determines whether the wave height of the direct wave received by one of the sonars is equal to or greater than a reference value. If the CPU determines that it is true, it proceeds to step S130; if it determines that it is false, it proceeds to step S120.

[0050] In step S120, if the CPU has detected an obstacle whose distance and direction were estimated in step S30 or S100 in the previous cycle, it reduces the confidence level of the detection of that obstacle by subtracting 1. Conversely, if there are no obstacles whose distance and direction were estimated in step S30 or S100 in the previous cycle, no reduction in confidence level is performed.

[0051] In step S130, the CPU, similar to step S60, determines whether the wave height of the indirect wave received by sonar B is equal to or greater than the reference value. If the CPU determines it is negative, in step S140, it resets the flag Fac to off; if it determines it is positive, it proceeds to step S150.

[0052] In step S150, the CPU increases the reliability of the obstacle detection, whose distance and direction were estimated in step S30 or S100, by adding 1. However, in step S150, which is executed immediately after the operating mode changes from dual mode to single mode, the CPU adds 2 to the reliability of the obstacle detection.

[0053] In step S160, the CPU updates the distance and direction based on the distance between the obstacle and the vehicle 102 and the direction of the obstacle relative to the vehicle, which were estimated in step S30 or S100. The cumulative value of the added or subtracted confidence level of the obstacle detection is also checked.

[0054] Next, the CPU executes steps S210 to S370 shown in Figure 6. As can be seen from comparing Figure 6 with Figure 5, steps S210 to S360 are executed in the same way as steps S10 to S160. Therefore, a detailed explanation of steps S210 to S360 is omitted.

[0055] In steps S210 to S360, the flag Fac is replaced with the flag Fbd, and sonars A and C are replaced with sonars B and D, respectively. Also, sonar B is replaced with sonar C, and one of the sonars is replaced with the sonar closer to the obstacle between sonars B and D. In step S280, the CPU increases the confidence level of the obstacle whose distance and direction were estimated in step S230 by adding 1.

[0056] Furthermore, in step S350, the CPU increases the reliability of the obstacle detection, whose distance and direction were estimated in step S230 or S300, by adding 1. In step S350, which is executed immediately after the operating mode changes from dual mode to single mode, the CPU adds 2 to the reliability of the obstacle detection.

[0057] Upon completing step S360, the CPU, in step S370, determines the presence or absence of an obstacle and the necessity of an alarm based on the distance and direction updated in steps S160 and S360, and the confirmed reliability of the obstacle detection, in a manner known in the art. If the CPU determines that an alarm is necessary, it activates the alarm device 42 and issues an alarm by outputting a command signal to the meter ECU 40. The alarm may be adjusted so that its intensity increases as the distance between the vehicle and the obstacle decreases.

[0058] 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 to reduce the output of the drive unit 22 to zero, and outputs a command signal to the brake ECU 30 to activate the brake unit 32 and brake the vehicle. Note that the reduction of the output of the drive unit 22 and / or braking of the vehicle may be omitted.

[0059] <Operation of the Embodiment> As described above, steps S210 to S360 are performed in the same manner as steps S10 to S160, so only steps S10 to S160 will be described in relation to the operation of the embodiment.

[0060] C1: When there are no obstacles within the detection range of vehicle 102. In step S10, a positive determination is made, and in step S20, ultrasonic waves are transmitted simultaneously by sonars A and C. However, since the wave height of the direct waves received by sonars A and C is below the reference value, the distance between the obstacle and the vehicle 102 and the direction of the obstacle relative to the vehicle are not estimated in step S30.

[0061] In step S40, a negative determination is made, in step S50, no deduction is made to the reliability of obstacle detection, and in step S160, the cumulative value of the deduction to the reliability of obstacle detection is confirmed. Therefore, in step S370, it is determined that the reliability of obstacle detection is below the standard value, and thus it is determined that there are no obstacles within the detectable range.

[0062] C2: If there is an obstacle within the detectable range of vehicle 102. C2-1: In the case of indirect wave cancellation In step S10, a positive determination is made, and in step S20, ultrasonic waves are transmitted simultaneously by sonars A and C. Since the peak value of the received voltage of the direct waves received by sonars A and C is equal to or greater than the reference value, in step S30, the distance between the obstacle and the vehicle 102 and the direction of the obstacle relative to the vehicle are estimated.

[0063] In step S40, a positive determination is made, and the wave height of the indirect wave received by sonar B is also above the standard value. Therefore, in step S60, a positive determination is made again, and in step S80, the reliability of obstacle detection is increased by 1. This process is repeated, and in step S160, the cumulative value of the added reliability of obstacle detection is confirmed.

[0064] Therefore, in step S370, it is determined that there is an obstacle within the detectable range because the reliability of the obstacle detection is determined to be above a standard value. If it is determined that an alarm is necessary, the alarm device 42 is activated and an alarm is issued. Also, if it is determined that there is a risk of the vehicle 102 colliding with an obstacle, the output of the drive unit 22 is reduced to zero and the braking unit 32 is activated to brake the vehicle.

[0065] Thus, under normal conditions where flag Fac is off, the operating mode is set to dual mode, and ultrasonic waves are simultaneously transmitted by sonars A and C, acting as the first and second sonars. The presence or absence of obstacles is determined based on the direct and indirect waves of these ultrasonic waves. Therefore, compared to the case where ultrasonic waves are transmitted by only one sonar and the presence or absence of obstacles is determined based on the direct and indirect waves of that ultrasonic wave, the obstacle detection range can be widened and the obstacle detection efficiency can be increased.

[0066] Furthermore, if the vehicle 102 moves away from the obstacle, or if the obstacle is another vehicle and moves away from the vehicle 102, causing the obstacle to move out of the detection range, the wave height of the direct wave received by sonars A and C will fall below the reference value. Therefore, in step S30, the distance between the obstacle and the vehicle 102 and the direction of the obstacle relative to the vehicle will no longer be estimated.

[0067] Furthermore, in step S40, a negative determination is made, in step S50, the reliability of obstacle detection is reduced by 1, and in step S160, the cumulative value of the addition or subtraction of the reliability of obstacle detection is confirmed. Therefore, similar to the case of C1 above, in step S370, it is determined that there are no obstacles within the detectable range because the reliability of obstacle detection is determined to be less than the standard value.

[0068] C2-2: In cases where indirect waves cancel each other out. In step S10, a positive determination is made, and in step S20, ultrasonic waves are transmitted simultaneously by sonars A and C. The wave height of the direct waves received by sonars A and C is above the reference value, but the wave height of the indirect waves received by sonar B is below the reference value, so in step S30, the distance between the obstacle and the vehicle 102 and the direction of the obstacle relative to the vehicle are not estimated.

[0069] In step S40, an affirmative determination is made, but in step S60, a negative determination is made, so in step S70, the flag Fac is set to on, and in step S10 of the next control cycle, a negative determination is made. In step S90, ultrasonic waves are transmitted by only one of sonars A and C, and in step S100, the distance between the obstacle and the vehicle 102 and the direction of the obstacle relative to the vehicle are estimated.

[0070] Since the wave height of the direct wave received by either sonar A or C is above the reference value, and the wave height of the indirect wave received by sonar B is also above the reference value, a positive determination is made in steps S110 and S130. In step S150, the confidence level of the obstacle detection, whose distance and direction were estimated in steps S30 and S100, is increased by 1, and in step S160, the cumulative value of the added or subtracted confidence level of the obstacle detection is confirmed. As mentioned above, in step S150, which is executed immediately after the operating mode changes from dual mode to single mode, the confidence level of the obstacle detection is increased by 2.

[0071] Therefore, as in the case of C2-1 above, in step S370, it is determined that there is an obstacle within the detectable range when it is determined that the reliability of the obstacle detection is equal to or greater than the standard value. If it is determined that an alarm is necessary, the alarm device 42 is activated and an alarm is issued. Also, if it is determined that there is a risk of the vehicle 102 colliding with an obstacle, the output of the drive unit 22 is reduced to zero and the braking unit 32 is activated to brake the vehicle.

[0072] Thus, in a situation where ultrasonic waves are being transmitted by sonars A and C, if sonar C, acting as a third sonar, does not receive indirect waves from the two ultrasonic waves, the flag Fac is set to on, and the operating mode is set to single mode. Therefore, by transmitting ultrasonic waves using only one of the first and second sonars, sonars A and C, the cancellation of indirect waves is eliminated, and the presence or absence of obstacles can be determined based on the direct and indirect waves of ultrasonic waves transmitted by only one of the sonars.

[0073] When sonar C receives indirect ultrasonic waves, it is thought that cancellation of the indirect waves occurred when the operating mode was set to dual mode. In this case, the reliability of obstacle detection is increased by 2 in step S150. Therefore, the same reliability of obstacle detection is set as when the operating mode is set to dual mode and sonar C receives indirect ultrasonic waves from two sources. Consequently, even if cancellation of indirect waves occurs, the presence or absence of an obstacle can be determined in the same way as when no cancellation of indirect waves occurs.

[0074] Furthermore, when the operating mode is set to single mode, if one sonar receives a direct wave and the third sonar, sonar C, does not receive an indirect wave of ultrasound transmitted by the other sonar, the operating mode is returned to dual mode. Therefore, when sonar C stops receiving indirect waves, the operating mode can be returned to dual mode.

[0075] In particular, in this embodiment, in step S90, the sonar closer to the obstacle is selected as one of sonars A and C. Therefore, compared to the case where the sonar further from the obstacle is selected as one of the sonars, the presence or absence of the obstacle can be determined more accurately.

[0076] Furthermore, if vehicle 102 moves outside the detection range, the wave height of the direct wave received by either sonar A or C will fall below the reference value. Therefore, in step S100, the distance between the obstacle and vehicle 102 and the direction of the obstacle relative to the vehicle are no longer estimated.

[0077] Furthermore, in step S110, a negative determination is made, in step S120, the reliability of obstacle detection is reduced by 1, and in step S160, the cumulative value of the addition or subtraction of the reliability of obstacle detection is confirmed. Therefore, similar to the case of C1 above, in step S370, it is determined that there are no obstacles within the detectable range because the reliability of obstacle detection is determined to be less than the standard value.

[0078] Furthermore, in step S140, the flag Fac is reset to off, so in step S10 of the next control cycle, a positive determination is made, and steps S20 to S80 and step S160 are executed.

[0079] 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.

[0080] For example, in this embodiment, in step S90, the sonar closer to the obstacle is selected as one of sonars A and C. However, the sonar further from the obstacle may also be selected as one of the sonars. Furthermore, based on the distance between the vehicle 102 and the obstacle and the change in the direction of the obstacle relative to the vehicle, the speed at which the positions where sonars A and C are installed on the vehicle 102 approach the obstacle is determined, and the sonar with the higher speed may be selected.

[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 periphery 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 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 reflected by an object from the sound waves transmitted by the first and second sonars; and the control unit is configured to estimate the distance between the object that reflected the direct waves and the indirect waves and the vehicle, and the direction of the object relative to the vehicle, based on the flight time of the direct waves and the indirect waves. Each sonar is configured to output a signal indicating the peak value of the received sound wave to the control unit, and the control unit is configured to determine that the corresponding sonar is receiving a sound wave when the peak value is equal to or greater than a reference value, and to determine that the corresponding sonar is not receiving a sound wave when the peak value is less than the reference value. The control unit is further configured to transmit sound waves using only one of the first and second sonars when the operation mode is set to dual mode and the first and second sonars are transmitting sound waves, and the first and second sonars are receiving direct waves and the third sonar is not receiving indirect waves, thereby setting the operation mode to single mode and transmitting sound waves using only one of the first and second sonars.

2. An object detection device according to claim 1, wherein the control unit sets the reliability of object detection based on the peak value of the sound wave received by each sonar, and when the operating mode is set to the single mode, the control unit is configured to set the same reliability of object detection as when the operating mode is set to the dual mode, in which case the control unit sets the reliability of object detection as when the third sonar receives the indirect wave of the sound wave transmitted by the first and second sonars.

3. An object detection device according to claim 1 or 2, wherein the control unit is configured to return the operating mode to the dual mode when the operating mode is set to the single mode and one of the sonars receives a direct wave and the third sonar does not receive an indirect wave of sound waves transmitted by the one of the sonars.

4. An object detection device according to claim 1, wherein the control unit is configured to designate the sonar that is closer to the object among the first and second sonars as the one sonar.

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