COLLISION AVOIDANCE ASSISTANCE DEVICE

Abstract

A collision avoidance assistance device is disclosed that can execute an automatic braking process and an automatic steering process to avoid a collision with an obstacle. If the magnitude of a steering angle exceeds a predetermined threshold, the collision avoidance assistance device determines that a driver intends to avoid the collision by a steering operation and stops the automatic braking and steering processes. However, in such a case, the automatic braking and steering processes can be stopped if the steering angle exceeds the threshold as a result of the execution of the automatic steering process.Considering that, if both the automatic braking process and the automatic steering process are being executed, the collision avoidance assistance device continues the automatic braking process and the automatic steering process even if the amount of the steering angle is greater than the predetermined threshold.

Description

BACKGROUND OF THE INVENTION Area of ​​the invention

[0001] The present invention relates to a collision avoidance assistance device that controls a braking device and a steering device of a vehicle in order to avoid a collision of the vehicle with an obstacle. Description of the state of the art

[0002] A conventional known collision avoidance assistance device of this type (hereinafter also referred to as the “conventional device”) initiates an automatic braking process or automatic braking process of generating a braking force to avoid a collision of a vehicle with an obstacle when a predetermined time until the collision with the obstacle is less than a predetermined value.

[0003] Additionally, if the collision with the obstacle cannot be avoided by the automatic braking process alone, the conventional device performs an “automatic steering process or automatic steering process of automatically changing the steering angle of the vehicle” in addition to the automatic braking process (see Japanese patent publication JP 2017 - 27 292 A).

[0004] Furthermore, DE 10 2016 210 848 A1 discloses a driver assistance system for avoiding a collision with an object, wherein at least one object located in the vehicle's vicinity is detected by sensors and assessed with regard to a collision risk with the vehicle. Subsequently, depending on this assessment, an automatic intervention in the vehicle's movement is initiated, which includes the execution of automatic braking of the vehicle depending on the assessment of the collision risk, whereby steering input from the driver is permitted to perform an evasive maneuver. If the driver intervenes with steering input, the automatic braking is terminated and automatic steering assistance from the driver is possible.Furthermore, DE 10 2004 056 027 A1 discloses a method for preventing collisions or reducing the severity of a collision involving a vehicle, wherein the current and future position of objects relative to the vehicle is assessed, and a warning is issued to the driver or an automatic steering and / or braking intervention is carried out by a vehicle assistance system depending on the preceding assessment, if a collision with an object is unavoidable without system intervention according to the preceding assessment. Further prior art in this field is known from WINNER, H. [et al.] (eds.): “Handbook of Driver Assistance Systems”, 3rd ed. Wiesbaden, Springer, 2015, pp. 898-900.

[0005] Furthermore, the driver may perform a steering operation to avoid a collision while the automatic braking process is running. In such a case, it may be appropriate not to initiate the automatic braking process in order to prioritize the driver's collision avoidance operation. Accordingly, the automatic braking process can be stopped if the steering angle, corresponding to the steering wheel's movement, exceeds a predetermined angle threshold.

[0006] However, in the case where the automatic steering process is executed in addition to the automatic braking process, it is possible that even if the extent of the steering angle exceeds the angle threshold, it cannot be determined whether this occurred as a result of the steering operation by the driver or as a result of the automatic steering process. SUMMARY OF THE INVENTION

[0007] The present invention was made to solve the problem described above. Specifically, it is an object of the present invention to provide a collision avoidance assistance device that can suitably determine whether the execution of the automatic braking process should be stopped when the steering angle increases during the execution of the automatic braking process. According to the invention, this object is achieved by a collision avoidance assistance device according to claim 1. Further features and advantageous embodiments are shown in the dependent claims.

[0008] A collision avoidance assistance device according to the present invention, which achieves the above-described objective (hereinafter also referred to as the "device of the present invention") comprises an obstacle detection section, a steering angle sensor and a collision avoidance control section.

[0009] The obstacle detection section (a millimeter wave radar 41 and a front camera 42) detects an obstacle in one direction of travel of a vehicle (10).

[0010] The steering angle sensor (68) detects, as a steering angle (θs), the rotation angle of a steering wheel (51) of the vehicle.

[0011] The collision avoidance control section (a collision avoidance ECU 20) performs an “automatic braking process” of reducing the vehicle’s speed (vehicle speed Vs) by controlling a braking device (a brake ECU 32 and a brake actuator 66) of the vehicle when it is determined that the vehicle will collide with the detected obstacle (a “yes” determination in step 425 of Fig. 4) ( Fig. 5).

[0012] Additionally, the collision avoidance control section executes an “automatic steering process” in addition to the automatic braking process if it is determined that the vehicle cannot be stopped by the automatic braking process at a time before the vehicle reaches the obstacle (a “yes” determination in step 525 of Fig. 5), wherein the automatic steering process changes the steering angles of steerable wheels of the vehicle by controlling a steering device of the vehicle comprising the steering wheel ( Fig. 6).

[0013] Furthermore, if the collision avoidance control section executes the automatic braking process but not the automatic steering process, the collision avoidance control section stops the execution of the automatic braking process (steps 555 to 560 of Fig. 5) if the magnitude of the detected steering angle becomes greater than a predetermined “first angle threshold (θth1)” (a “no” determination in step 510 of Fig. 5); and In the case where the collision avoidance control section performs both the automatic braking process and the automatic steering process, the collision avoidance control section continues both the automatic braking process and the automatic steering process even if the magnitude of the detected steering angle becomes greater than the first angle threshold.

[0014] If the steering angle exceeds the first angle threshold, the device of the present invention determines whether the automatic braking process should be stopped, based on whether the automatic steering process is being executed or not. Therefore, it is possible to avoid the phenomenon of the automatic braking process being stopped when the steering angle increases as a consequence of the automatic steering process. Consequently, the device of the present invention can suitably determine whether the automatic braking process should be stopped if the steering angle increases during the execution of the automatic braking process.

[0015] According to the device of the present invention, in the case where the collision avoidance control section executes both the automatic braking process and the automatic steering process, the collision avoidance control section stops the execution of the automatic braking process and the execution of the automatic steering process (steps 630 to 645 of Fig. 6) if the magnitude of the detected steering angle becomes greater than a predetermined “second angle threshold (θth2)” which is greater than the first angle threshold (a “no” determination in step 610 of Fig. 6).

[0016] If the steering angle exceeds the second angle threshold, it is clear that the driver is attempting to avoid a collision with the obstacle by steering. Therefore, the system in the current mode can stop the automatic braking and steering processes if the driver is attempting to avoid a collision with the obstacle by steering.

[0017] Furthermore, in the present mode, the collision avoidance control section is preferably configured to control the steering device in such a way that the magnitude of the steering angle does not exceed a predetermined maximum steering angle (θmax) when the collision avoidance control section performs the automatic steering process; and the collision avoidance control section applies a value that is less than the maximum steering angle as the first angle threshold value, and a value that is greater than the maximum steering angle as the second angle threshold value.

[0018] In this case, if the steering angle exceeds the second angle threshold, it is clearer that the driver is attempting to avoid a collision with the obstacle by steering, and therefore the automatic braking and steering processes are stopped. However, if the automatic steering process is not executed but the automatic braking process is, the automatic braking process is stopped when the steering angle exceeds the first angle threshold (i.e., before the steering angle exceeds the second angle threshold). Therefore, the current mode's device can more effectively determine whether to stop the automatic braking and steering processes when the driver is attempting to avoid a collision with the obstacle by steering.

[0019] According to another mode of the device of the present invention, the collision avoidance control section is configured to estimate, as a “collision time (TTC)”, a time that elapses until the vehicle collides with the obstacle, and to determine that the vehicle collides with the obstacle if the estimated collision time is shorter than a predetermined time threshold (Tth) (a “no” determination in step 425 of Fig. 4).

[0020] The magnitude of the collision time can be obtained, for example, by dividing the "distance between the vehicle and the obstacle (obstacle distance)" by the "rate of change of the obstacle distance per unit of time (relative speed)." Therefore, the device in the current mode can determine whether the vehicle will collide with the obstacle or not by performing a simple process.

[0021] Furthermore, in the current mode, the collision avoidance control section is preferably configured such that If the estimated collision time is shorter than the time threshold, the collision avoidance control section determines a "required delay (Dcreq)" that is necessary to avoid a collision with the obstacle; If the magnitude of the required deceleration is less than or equal to the magnitude of a "maximum deceleration (Dcmax)", the collision avoidance control section uses the required deceleration as a "target deceleration (Dctgt)" (step 565 of Fig. 5), and if the required deceleration is greater than the maximum deceleration, the collision avoidance control section uses the "maximum deceleration" as the "target deceleration" (step 530 of Fig. 5); where the collision avoidance control section executes the automatic braking process in such a way that the actual deceleration of the vehicle equals the target deceleration (steps 545 to 550 of Fig. 5); and If the required deceleration is greater than the maximum deceleration, the collision avoidance control section determines that the vehicle cannot be stopped by the automatic braking process at a time before the vehicle reaches the obstacle (a "yes" determination in step 525 of Fig. 5).

[0022] The vehicle's braking system achieves braking, for example, by preventing the wheels from rotating through frictional forces (braking friction forces). The greater the braking friction forces, the greater the deceleration (negative acceleration) of the vehicle. However, if the braking friction forces become excessively high, wheel slip occurs between the wheels and the road surface. Therefore, a deceleration slightly less than the point at which wheel slip begins is defined as the maximum deceleration. The maximum deceleration can be predetermined. Alternatively, if the braking system includes an anti-lock braking mechanism, the maximum deceleration can be defined as the maximum frictional braking force that does not cause wheel slip during braking.The device of the current mode can reduce the time required to stop the vehicle by the automatic braking process to a possible extent, and can appropriately determine whether the collision with the obstacle can be avoided by the automatic braking process alone or not.

[0023] According to another mode of the device of the present invention, the collision avoidance control section is configured such that when the collision avoidance control section performs the automatic steering process, the collision avoidance control section controls the steering device in such a way as to cause the vehicle to travel along an evasive path, which is a route for the vehicle to avoid a collision with the obstacle.

[0024] The evasive steering path is a route designed to avoid a collision with an obstacle where a collision with the vehicle is highly likely, and can also be a route to avoid collisions with other obstacles. This mode can reliably avoid collisions with obstacles by executing the automatic steering process.

[0025] It should be noted that, in order to facilitate understanding of the present invention, the components of the invention in the preceding description are identified by names and / or symbols in parentheses corresponding to those of an embodiment of the invention described later; however, the components of the invention are not limited to those in the embodiment defined by the names and / or symbols. Further objects, features, and associated advantages of the present invention will become apparent from the following description of the embodiment of the invention, which refers to the accompanying drawings. Brief description of the drawings Fig. Figure 1 is a schematic representation of the vehicle (present vehicle) on which a collision avoidance assistance device (present assistance device) according to an embodiment of the present invention is mounted; Fig. Figure 2 is a block representation of the current assistance device; Fig. Figure 3 is an illustration showing an example of collision avoidance control with respect to an obstacle with which a collision with the current vehicle is likely to occur; Fig. Figure 4 is a flowchart representing a collision avoidance control start process routine executed by the current assistance device; Fig. Figure 5 is a flowchart representing an automatic braking process routine executed by the current assistance device; and Fig. Figure 6 is a flowchart representing an automatic steering process routine executed by the current assistance device. Description of preferred embodiments

[0026] A collision avoidance assistance device according to an embodiment of the present invention (hereinafter also referred to as the "present assistance device") will now be described with reference to the drawings. The present assistance device is mounted on a Fig. Vehicle 10 shown was applied. Fig. Figure 2 shows a block diagram of the current assistance device. The current assistance device comprises "a collision avoidance ECU 20, a machine ECU 31, a brake ECU 32, and an EPS ECU 33", each of which is an electronic control unit (ECU).

[0027] The collision avoidance ECU20 comprises a CPU, a ROM, and a RAM. The CPU performs data reading, numerical calculations, and the calculation of output results, etc., by repeatedly executing predefined programs (routines). The ROM stores the programs executed by the CPU, lookup tables (maps), etc. The RAM temporarily starts the program.

[0028] Like the collision avoidance ECU 20, each of the machine ECU 31, brake ECU 32, and EPS ECU 33 comprises a CPU, a ROM, and a RAM. These ECUs can communicate (exchange) data with each other via a CAN (control unit network) 34. Additionally, each ECU can receive output values ​​from sensors connected to other ECUs via the CAN 34.

[0029] The collision avoidance ECU 20 is connected to a millimeter wave radar 41, a front camera 42, a vehicle speed sensor 43, a yaw rate sensor 44, an accelerometer 45, an input / output device 46, and speakers 47.

[0030] The millimeter-wave radar 41 transmits a millimeter wave (an electromagnetic wave with a frequency in the range of 30 GHz to 300 GHz) towards a region in front of the vehicle 10 and receives its reflected wave. Based on the transmitted and reflected waves, the millimeter-wave radar 41 receives the following target information: the position (relative position) of a target located in front of the vehicle 10 with respect to the vehicle 10, the speed (relative speed) of the target with respect to the vehicle 10, the angle of the left end of the target with respect to the vehicle 10, and the angle of the right end of the target with respect to the vehicle 10. The millimeter-wave radar 41 outputs the received target information to the collision avoidance ECU 20.The search area of ​​the millimeter wave radar 41 in the horizontal direction is equal to an area defined by a line between a straight line ML and a straight line MR, which is in . Fig. 1 are shown, formed at an angle (acute angle) is represented.

[0031] The front camera 42 is mounted near an interior rearview mirror (not shown) located at an upper position within the passenger compartment of the vehicle 10. The front camera 42 captures an image of a region in front of the vehicle 10 (hereinafter also referred to as the "frontal image") and outputs a signal representing the frontal image to the collision avoidance ECU 20. The horizontal viewing angle (field of view) of the front camera 42 is equal to an area defined by a line drawn between a straight line OL and a straight line OR, which is Fig. Figure 1 shows the formed angle (acute angle).

[0032] The vehicle speed sensor 43 detects the vehicle speed Vs of the vehicle 10 and outputs a signal representing the vehicle speed Vs to the collision avoidance ECU 20.

[0033] The yaw rate sensor 44 detects the yaw rate YR of the vehicle 10 and outputs a signal representing the yaw rate YR to the collision avoidance ECU 20.

[0034] The acceleration sensor 45 detects the acceleration As of the vehicle 10 in the longitudinal direction (the rate of change of the vehicle speed Vs per unit of time).

[0035] The input / output unit 46 is mounted on the dashboard of the vehicle 10. The input / output unit 46 includes a display unit (liquid crystal display). Letters, drawings, etc., displayed on the display unit of the input / output unit 46 are controlled by the collision avoidance ECU 20. The display unit of the input / output unit 46 also functions as a touch-sensitive panel. Therefore, a driver can send instructions to the collision avoidance ECU 20 by touching the display unit.

[0036] The loudspeakers are located inside the left and right front doors (not shown in vehicle 10, inside the passenger compartment). The loudspeakers 47 can produce sounds, such as a warning tone and a voice message, according to instructions from the collision avoidance ECU 20.

[0037] The machine ECU 31 is connected to a variety of machine sensors 61 and receives detection signals from these sensors. The machine sensors 61 detect the operating state variables of the machine 62, which is a drive source for the vehicle 10. The machine sensors 61 include an accelerator pedal actuation extent sensor, a throttle valve opening sensor, a machine speed sensor, an intake air volume sensor, etc.

[0038] Furthermore, the machine ECU 31 is connected to machine actuators 63, such as a throttle valve actuator and a fuel injector, and to a transmission 64. The machine ECU 31 modifies the drive torque Tq generated by the machine 62 of the vehicle 10 and the gear ratio of the transmission 64 by controlling the machine actuators 63 and the transmission 64. Therefore, the machine ECU 31 adjusts the drive force of the vehicle 10 to control the acceleration As. Additionally, the collision avoidance ECU 20 controls the machine actuators 63 and the transmission 64 by sending instructions to the machine ECU 31 to modify the drive force of the vehicle 10.

[0039] The brake ECU 33 is connected to a multitude of brake sensors 64 and receives detection signals from these sensors. The brake sensors 65 detect parameters used to control a brake (hydraulic friction brake) mounted on the vehicle 10 (not illustrated). The brake sensors 65 include an actuation extent sensor for detecting the actuation extent of a brake pedal (not shown), wheel speed sensors for detecting the wheels, etc.

[0040] Furthermore, the brake ECU 32 is connected to a brake actuator 66. The brake actuator 66 is a hydraulic control actuator. The brake actuator 66 is located in a hydraulic circuit extending between a master cylinder, which pressurizes hydraulic oil by utilizing the downward force applied to the brake pedal, and the friction brake, which comprises known wheel cylinders provided in the wheels. The hydraulic circuit, the master cylinder, and the friction brake are not shown in the drawings. The brake actuator 66 controls the oil pressure supplied to the wheel cylinders. The brake ECU 32 generates braking forces (friction braking forces) Bf, which are applied to the wheels, by driving or controlling the brake actuator 66, thereby controlling the acceleration As (in this case, a negative acceleration; specifically, a deceleration) of the vehicle 10.Furthermore, the collision avoidance ECU 20 controls the brake actuator 66 by sending an instruction to the brake ECU 32 in order to change the braking forces Bf.

[0041] The EPS-ECU 33 is connected to a torque sensor 67 and a steering angle sensor 68 and receives detection signals from these sensors. The torque sensor 67 and the steering angle sensor 68 are connected to a steering shaft (not shown) connected to a steering wheel 51. The torque sensor 67 outputs a signal representing a steering torque Ts applied to the steering wheel 51 by the driver. The steering angle sensor 68 outputs a signal representing a steering angle θs, which is the rotation angle of the steering shaft of the steering wheel 51. The steering angle θs is "0" when the steering wheel 51 is in its neutral position, assumes a positive value when the steering wheel 51 is turned clockwise from the neutral position, and assumes a negative value when the steering wheel 51 is turned counterclockwise from the neutral position.

[0042] Furthermore, the EPS-ECU 33 is connected to a drive circuit 69. The drive circuit 69 supplies electrical energy to a motor 71. The motor 71 generates a motor torque Tm to rotate the steering shaft of the steering wheel 51. To assist the driver's steering operation of the steering wheel 51, the EPS-ECU 33 controls the drive circuit 69 so that the motor torque Tm becomes equal to a "target assistance torque Ta determined on the basis of the steering torque Ts, the steering angle θs, the vehicle speed Vs, etc." Additionally, the collision avoidance ECU 20 drives the motor 71 by sending a command to the EPS-ECU 33, thereby changing the steering angles of the steerable wheels of the vehicle 10. (Collision avoidance control, overview)

[0043] Next, a collision avoidance control system, executed by the collision avoidance ECU 20 to prevent a collision with an obstacle, is described. The collision avoidance control system includes an automatic braking process and an automatic steering process. The automatic braking process is executed when it is highly likely that the vehicle 10 will collide with the obstacle. Its purpose is to adjust a target deceleration Dctgt, which is the required deceleration (i.e., negative acceleration) to avoid the collision, and the actual acceleration As of the vehicle 10 to match the target deceleration Dctgt.

[0044] The automatic steering process is executed when the probability of avoiding a collision with an obstacle is high, and not solely due to the automatic braking process. Its purpose is to determine an evasive path (Rd) to avoid the collision and to adjust the actual path of the vehicle 10 to match this evasive path. The driver of the vehicle 10 can switch the request state of the collision avoidance control by actuating the input / output device 46 between an ON state to allow the collision avoidance control to be executed and an OFF state to prevent its execution. Because this collision avoidance control is a known control system, described, for example, in Japanese patent application publication no. JP 2017-27292 A, it is briefly described below. (Collision avoidance control automatic braking process)

[0045] First, the automatic braking process is described. The collision avoidance ECU 20 uses a lateral distance (distance in the side direction) Dy(n) of a target (n) located in a region of the front vehicle 10, a longitudinal distance (inter-vehicle distance) Dx(n) of the target (n), a relative lateral velocity Vy(n) of the target (n), a relative longitudinal velocity Vx(n) of the target (n), and a lateral width We(n) of the target (n), based on the target information received from the millimeter-wave radar 41 and the image received from the front camera 43 in the front direction. The relative lateral velocity Vy(n) is the rate of change of the lateral distance Dy(n) per unit time, and the relative longitudinal velocity Vx(n) is the rate of change of the longitudinal distance Dx(n) per unit time.

[0046] In particular, as in Fig. As shown in Figure 1, the longitudinal direction of vehicle 10 is defined as an x-axis, and the lateral direction of vehicle 10 is defined as a y-axis. The lateral center of a front end of vehicle 10 is the origin, where x = 0 and y = 0. The x-coordinate takes a positive value in the front direction of vehicle 10 and a negative value in the rear direction of vehicle 10. The y-coordinate takes a positive value in the right direction of vehicle 10 and a negative value in the left direction of vehicle 10. The symbol (n) is an identifier added to each target. In the present embodiment, “n” is a natural number.

[0047] Based on the moving position of the target (n), the collision avoidance ECU 20 estimates an approach time distance Dyr(n), which is the lateral distance Dy(n) at the time when the lateral distance Dx(n) of the target (n) becomes zero, assuming that the vehicle speed Vs and steering angle θs do not change and that the speed, direction of travel, etc., of the target (n) do not change. If the following equation (1) regarding the approach lateral distance Dyr(n) is satisfied, the collision avoidance ECU 20 determines that the target (n) is an obstacle (a) with which a collision with the vehicle 10 is highly probable. The symbol (a) is the identifier of the target determined to be an obstacle (therefore, "a" is a natural number). The target determined to be an obstacle is referred to as the "obstacle (a)" for simplicity. |Dyr(n)| <Wo / 2+Wd(n) / 2+Lm

[0048] Here, Wo is the width (length in the lateral direction) of the vehicle 10, and Lm is a predetermined length (collision determination tolerance).

[0049] In other words, the collision avoidance ECU 20 determines that the target (n) is the obstacle (a) in the case when the longitudinal distance Dx(n) of the target (n) becomes zero, the left end of the target (n) is on the left side of a "position offset to the right from the right end of the vehicle 10 by the collision determination tolerance Lm", and the right end of the target (n) is on the right side of a "position offset to the left from the vehicle end of the vehicle 10 by the collision determination tolerance Lm".

[0050] Fig. Figure 3 is a top view showing the case where vehicle 81 is the obstacle (a) with respect to vehicle 10. For simplicity, the identifier of vehicle 81 is set to (1). In the example of Fig. 3. The longitudinal distance Dx(1) between vehicle 10 and vehicle 81 is Dx1. Additionally, the lateral distance Dy(1) between vehicle 10 and vehicle 81 is a negative value, and the magnitude of the lateral distance Dy(1) is Dy(1). A portion with a solid line L1 represents the path of motion of the central section of the front end of vehicle 10.

[0051] A in Fig. Vehicle 82, shown in Figure 3, is an oncoming vehicle with respect to vehicle 10 (a vehicle traveling in an oncoming lane with respect to the lane in which vehicle 10 is traveling). An arrow with a solid line L2 represents the path of movement of the central section of the front end of vehicle 82.

[0052] In the Fig. In example 3, vehicle 10 is moving (traveling straight ahead), and vehicle 81 is stopped. Therefore, the relative longitudinal velocity Vx(1) is a negative value, the magnitude of the relative longitudinal velocity Vx(1) is equal to the vehicle speed Vs, and the relative lateral velocity Vy(1) is zero.

[0053] The length Dy1 is less than half the width of vehicle 10 (specifically, |Dy(1)| < Wo / 2). Additionally, because vehicle 10 is moving straight ahead and vehicle 81 is stopped, the approach lateral distance Dyr(1) is equal to Dy1 (the magnitude of the lateral distance Dy(1) does not change with the length Dy1). Consequently, the relationship in equation (1) holds true. Therefore, the collision avoidance ECU 20 determines that vehicle 81 is an obstacle.

[0054] Once the obstacle is specified, the collision avoidance ECU 20 calculates a collision time TTC, which is the expected time until the vehicle 10 collides with the obstacle (a), based on the longitudinal distance Dx(a) and the relative longitudinal velocity Vx(a) of the obstacle (a). Specifically, the collision time TTC is obtained by reversing the sign of a value obtained by dividing the longitudinal distance Dx(a) by the relative longitudinal velocity Vx(a) (namely, TTC = -Dx(a) / Vx(a)).

[0055] In the Fig. In example 3, the collision time TTC is equal to a value obtained by dividing the length Dx1 by the vehicle speed Vs (namely, TTC = D×1 / Vs).

[0056] If the collision time TTC is less than a predetermined time threshold Tth (specifically, if the collision time TTC is a positive value and the absolute value of the collision time TTC is less than the time threshold Tth), the collision avoidance ECU 20 initiates the automatic braking process. The time threshold Tth is set to a time determined such that, even if the driver becomes aware of the obstacle and performs a normal braking operation, the driver will not be able to stop the vehicle 10 in a position before the obstacle if the collision time TTC is less than the time threshold Tth.

[0057] During an execution of the automatic braking process, the collision avoidance ECU 20 determines a target deceleration Dctgt. In particular, a required deceleration Dcreq, which is an acceleration As necessary to stop the vehicle 10 after traveling a distance Dd, is calculated according to the following equation (2). Dcreq=−(1 / 2)⋅Vs2 / Dd

[0058] The collision avoidance ECU 20 calculates the required deceleration Dcreq by substituting the difference between the longitudinal distance Dx(a) of the obstacle (a) and a predetermined length (stop position tolerance) Lv in equation (2) as a travel distance Dd (namely, Dd = Dx(a) - Lv).

[0059] In the case where the required deceleration |Dcreq| is greater than the maximum deceleration |Dcmax|, which is the maximum deceleration of vehicle 10, the collision avoidance ECU 20 sets the target deceleration Dctgt to the maximum deceleration Dcmax. Conversely, in the case where the required deceleration |Dcreq| is less than or equal to the maximum deceleration |Dcmax|, the collision avoidance ECU 20 sets the target deceleration Dctgt to the required deceleration Dcreq. The maximum deceleration Dcmax is set such that no wheel slip occurs between the wheels (not shown) of vehicle 10 and a road surface as a result of generating the braking forces Bf to decelerate the vehicle speed Vs.

[0060] The collision avoidance ECU 20 sends request signals to the engine ECU 31 and the brake ECU 32 so that the actual acceleration As equals the target deceleration Dctgt. Specifically, the collision avoidance ECU 20 sends a request signal to the brake ECU 32 to generate the braking force Bf such that the actual acceleration As equals the target deceleration Dctgt. Additionally, the collision avoidance ECU 20 sends a request signal to the engine ECU 31 to reduce the drive torque Tq to zero. As a consequence, the vehicle speed Vs decreases and eventually becomes zero. (Collision avoidance control automatic steering process)

[0061] Next, the automatic steering process is described. In the case where the required deceleration |Dcreq| is greater than the maximum deceleration |Dcmax|, which is the maximum deceleration of vehicle 10, the probability that the collision with the obstacle (a) cannot be avoided solely by the automatic braking process is high. In such a case, the collision avoidance ECU 20 attempts to obtain an evasive driving path Rd, which is a path for vehicle 10 that allows vehicle 10 to avoid the collision with the obstacle (a) and does not cause a collision with any other target (n).

[0062] The alternative route Rd is a route that satisfies the following conditions (A) and (B). (A) If vehicle 10 travels along the alternative route Rd, vehicle 10 will not collide with targets encompassing the obstacle (a). (B) The maximum value of the magnitude |θs| of the steering angle θs at the time when the vehicle 10 is traveling along the evasive route Rd is less than a predetermined maximum steering angle θmax. In the present embodiment, the maximum steering angle θmax is 130°.

[0063] In the example of Fig. In Figure 3, the evasive path Rd is represented by an arrow with a dashed line L3. If vehicle 10 travels along the evasive path Rd, it can avoid the collision with vehicle 81 and does not collide with vehicle 82. Additionally, the maximum value of the steering angle θs at the time vehicle 10 travels along the evasive path Rd is smaller than the maximum steering angle θmax.

[0064] In the event that the collision avoidance ECU 20 has successfully obtained the evasive path Rd, the collision avoidance ECU 20 adjusts the steering angle θs using the engine torque Tm generated by the motor 71, so that the vehicle 10 travels along the evasive path Rd. Specifically, the collision avoidance ECU 20 executes the automatic steering process while the automatic braking process is being carried out. A vehicle 10a that is in Fig. The position of vehicle 10, represented by dashed lines, is shown after it was stopped, while a collision with vehicle 81 was prevented by the automatic braking process and the automatic steering process.

[0065] In particular, the collision avoidance ECU 20 calculates an angular difference θy between the direction of travel of vehicle 10 and the direction of extension of the evasive path Rd at the current position of vehicle 10 on the evasive path Rd. Additionally, the collision avoidance ECU 20 calculates a midpoint distance Dh, which is the distance (in the lateral direction) between the evasive path Rd and the midpoint of the front end of vehicle 10 (the difference in driving position). Furthermore, the collision avoidance ECU 20 calculates a path curvature v, which is the reciprocal of the radius of curvature of the evasive path Rd at the current position of vehicle 10 on the evasive path Rd.

[0066] Next, the collision avoidance ECU 20 calculates the angular difference θy and the path curvature v of a target yaw rate YRtgt based on the center distance Dh according to the following equation (3) at predetermined calculation intervals. The target yaw rate YRtgt is a yaw rate set such that the vehicle 10 travels along the evasive path Rd. YRtgt=K1⋅Dh+K2⋅θy+K3⋅v

[0067] Here, K1, K2 and K3 are predetermined control gains.

[0068] Based on the target yaw rate YRtgt and the actual yaw rate YR, the collision avoidance ECU 20 determines a target motor torque Tmtgt of motor 71, which is required to achieve the target yaw rate YRtgt, at predetermined calculation intervals. Specifically, the collision avoidance ECU 20 calculates a yaw rate difference ΔYR, which is the difference between the target yaw rate YRtgt and the actual yaw rate YR (namely, ΔYR = YRtgt - YR). Additionally, the collision avoidance ECU 20 determines the target motor torque Tmtgt by applying the yaw rate difference ΔYR to a "lookup table" that contains the pre-stored relationship between the yaw rate difference ΔYR and the target motor torque Tmtgt.

[0069] Furthermore, the collision avoidance ECU 20 sends a request signal to the EPS ECU 33, so that the actual engine torque Tm equals the target engine torque Tmtgt. As described above, when the vehicle 10 travels along the evasive path Rd, the maximum value of the magnitude |θs| of the steering angle θs does not exceed the maximum steering angle θmax. (Avoidance control stop process)

[0070] Furthermore, in some cases, the driver of vehicle 10 attempts to avoid the collision with the obstacle by turning the steering wheel 51 during a period between when the collision avoidance control was initiated and when vehicle 10 stops. In such a case, the collision avoidance control must be stopped to give priority to the collision avoidance operation of vehicle 10 by the driver. Therefore, if the magnitude |θs| of the steering angle θs becomes greater than the predetermined threshold during an execution of the collision avoidance control, the collision avoidance ECU 20 determines that the driver of vehicle 10 is attempting to avoid the collision with the obstacle by turning the steering wheel 51 and stops the execution of the collision avoidance control.

[0071] In particular, if only the automatic braking process is executed out of the automatic braking and steering processes, the collision avoidance ECU 20 stops the execution of the collision avoidance control if the magnitude |θs| of the steering angle θs is greater than a first angle threshold θth1 (specifically, |θs| > θth1). Specifically, the collision avoidance ECU 20 stops the execution of the automatic braking process. In the current embodiment, the first angle threshold θth1 is 50°. However, no restriction is specified regarding the first angle threshold θth1, as long as it is set to a value less than the "maximum steering angle θmax, which is the maximum value of the magnitude |θs| of the steering angle θs that is changed in the automatic steering process."

[0072] However, in the case where both the automatic braking process and the automatic steering process are executed, the magnitude |θs| of the steering angle θs can increase to the maximum steering angle θmax (130° in the present embodiment) as a consequence of the automatic steering operation. Therefore, even if the magnitude |θs| of the steering angle θs becomes greater than the "first angle threshold θth1, which is smaller than the maximum steering angle θmax", the collision avoidance ECU 20 cannot determine whether the current state is one in which the driver is operating the steering wheel 51, or one in which the magnitude |θs| of the steering angle θs is greater than the first angle threshold θth1 due to the automatic steering process.

[0073] In light of the foregoing, if the magnitude |θs| of the steering angle θs is greater than a "second angle threshold θth2, which is greater than the maximum steering angle θmax" (namely |θs| > θth2 > θmax > θth1), the collision avoidance ECU 20 determines that the driver is attempting to avoid the collision with the obstacle by turning the steering wheel 51 and stops the execution of the collision avoidance control. Specifically, if the magnitude |θs| of the steering angle θs is greater than the second angle threshold θth2, the collision avoidance ECU 20 stops the execution of the automatic braking process and the execution of the automatic steering process. In the present embodiment, the second angle threshold θth2 is 150°. (Specific operation)

[0074] Next, a specific operation of the collision avoidance ECU 20 is described. The CPU of the collision avoidance ECU 20 (hereinafter also referred to as the "CPU" for simplicity) executes a "collision avoidance control start process routine", an "automatic braking process routine", and an "automatic steering process routine" each time a predetermined time elapses.

[0075] First, the collision avoidance control start process routine is described. The collision avoidance control start process routine is illustrated by a flowchart in Fig. 4 represents. When a suitable time is reached, the CPU starts the process from step 400 of Fig. 4, and proceeds to step 405 to determine whether the state of a collision avoidance control request is the ON state or not.

[0076] In the event that the state of a collision avoidance control request is set to the OFF state by the operator of the input / output device 46, the CPU makes a "no" determination in step 405 and proceeds to step 495 to terminate the current routine.

[0077] However, if the state of a collision avoidance control request is set to the ON state, the CPU makes a “Yes” determination in step 405 and proceeds to step 410 to determine whether the value of an automatic braking process execution flag or marker character XpcsB is “0” or not.

[0078] The automatic braking process execution flag XpcsB is set to "1" when the automatic braking process is executed (see step 430, step 560 of Fig. 5 and step 635 of Fig. 6, which will be described later). The automatic braking process execution flag XpcsB is set to “0” in an (not shown) output routine executed by the CPU when the collision avoidance ECU 20 is started (specifically, when an ignition switch of the vehicle 10, not illustrated, is moved from its OFF position to its ON position).

[0079] In the case where the value of the automatic braking process execution flag XpcsB is “0”, the CPU makes a “yes” determination in step 410 and proceeds to step 415 to determine whether or not a target identified as an obstacle is present.

[0080] If a target identified as an obstacle is present, the CPU makes a "yes" determination in step 415 and proceeds to step 420 to calculate the collision time TTC. The CPU then proceeds to step 425 to determine whether the collision time TTC is less than the time threshold Tth.

[0081] If the collision time TTC is less than the time threshold Tth, the CPU makes a "yes" determination in step 425 and proceeds to step 430 to set the value of the automatic braking process execution flag XpcsB to "1". The CPU then proceeds to step 495.

[0082] If the condition for step 410 is not met (specifically, if the value of the automatic braking process execution flag XpcsB is "1"), the CPU makes a "no" decision in step 410 and proceeds directly to step 495. Similarly, if the condition for step 415 is not met (specifically, if a target identified as an obstacle is not present), the CPU makes a "no" decision in step 415 and proceeds directly to step 495. Furthermore, if the condition for step 425 is not met (specifically, if the collision time TTC is greater than or equal to the time threshold Tth), the CPU makes a "no" decision in step 425 and proceeds directly to step 495.

[0083] Next, the automatic braking process routine is described. The automatic braking process routine is illustrated by a flowchart in Fig. 5 represents. When a suitable time has arrived, the CPU starts the process from step 500 of Fig. 5, and proceeds to step 505 to determine whether the condition that the value of the automatic braking process execution flag XpcsB is “1” and the value of the automatic steering process execution flag XpcsS is “0” is met or not.

[0084] The automatic steering process execution flag XpcsS is set to "1" when the automatic steering process is executed (see step 540 of Fig. 5 and step 645 of Fig. 6, which will be described later). The automatic steering process execution flag XpcsS is set to "0" in the aforementioned output routine.

[0085] In the case where the condition that the value of the automatic braking process execution flag XpcsB is "1" and the value of the automatic steering process execution flag XpcsS is "0" is not met (namely, in the case where the value of the automatic braking process execution flag XpcsB is "0" or the value of the automatic steering process execution flag XpcsS is "1"), the CPU makes a "no" determination in step 505 and proceeds directly to step 595 to terminate the current routine.

[0086] However, if the condition that the value of the automatic braking process execution flag XpcsB is "1" and the value of the automatic steering process execution flag XpcsS is "0" is met, the CPU makes a "yes" determination in step 505 and proceeds to step 510 to determine whether the magnitude |θs| of the steering angle θs is less than or equal to the first angle threshold θth1 or not.

[0087] In the case where the magnitude |θs| of the steering angle θs is less than or equal to the first angle threshold θth1, the CPU makes a "yes" determination in step 510 and proceeds to step 515 to determine whether an end condition for terminating collision avoidance control is unmet. The end condition is a condition that is met when the vehicle speed Vs is zero.

[0088] If the end condition for terminating collision avoidance control is not met, the CPU makes a "yes" determination in step 515 and proceeds to step 520 to calculate the required delay Dcreq. The CPU then proceeds to step 525 to determine whether the magnitude |Dcreq| of the required delay Dcreq is greater than the magnitude |Dcmax| of the maximum delay Dcmax.

[0089] In the case where the amount |Dcreq| of the required delay Dcreq is less than or equal to the amount |Dcmax| of the maximum delay Dcmax, the CPU makes a "no" determination in step 525 and proceeds to step 565 to set the value of the target delay Dctgt to the required delay Dcreq.

[0090] Next, the CPU proceeds to step 545 and sends the target deceleration Dctgt to the brake ECU 32 via CAN 34. As a consequence, the brake ECU 32 controls the brake actuator 66 by executing a routine (not illustrated) so that the actual acceleration As equals the target deceleration Dctgt, thereby generating the required braking force Bf.

[0091] The CPU then proceeds to step 550. In step 550, the CPU sets the target drive torque Tqtgt to "0" and sends this target drive torque Tqtgt to the machine ECU 31 via CAN 34. As a result, the machine ECU 31 controls the machine actuators 63 and the gearbox 64 by executing a routine (not illustrated) so that the actual drive torque Tq equals the target drive torque Tqtgt. The CPU then proceeds to step 595.

[0092] However, if the determination condition of step 525 is met (namely, if the amount |Dcreq| of the required delay Dcreq is greater than the amount |Dcmax| of the maximum delay Dcmax), the CPU makes a "yes" determination in step 525 and proceeds to step 530 to set the value of the target delay Dctgt to the maximum delay Dcmax.

[0093] The CPU then proceeds to step 535 and attempts to obtain the evasive path Rd to determine whether the evasive path Dr is present. If Rd is present, the CPU makes a "yes" determination in step 535 and proceeds to step 540 to set the value of the automatic steering process execution flag XpcsS to "1". As a result, the automatic steering process is initiated by the automatic steering process routine. Fig. Step 6, which will be described later, is executed. The CPU then proceeds to step 545.

[0094] However, if the condition for determining step 510 is not met (namely, if the steering angle θs is greater than the first angle threshold θth1), the CPU makes a "no" determination in step 510 and proceeds to step 555 to stop the automatic braking process. Specifically, the CPU determines that the driver is operating the steering wheel 51 of vehicle 10 and stops the automatic braking process.

[0095] Specifically, the CPU sets the target deceleration value Dctgt to "0" and sends this value to the brake ECU 32. Specifically, if the vehicle speed Vs is zero during the execution of step 555, the CPU, as a value of the target braking force Bftgt, sets a braking force Bf necessary to keep the vehicle 10 in a stopped state and sends this target braking force Bftgt to the brake ECU 32. In this case, the brake ECU 32 ensures that the actual braking force Bf matches the target braking force Bftgt by controlling the brake actuator 66. Next, the CPU proceeds to step 560 and sets the value of the automatic brake process execution flag XpcsB to "0". The CPU then proceeds to step 595.

[0096] Specifically, if the determination condition of step 515 is not met (i.e., if the end condition for terminating the collision avoidance control is met), the CPU makes a "no" determination in step 515 and proceeds to step 555. Additionally, if the determination condition of step 535 is not met (i.e., if the evasive path Rd is not present), the CPU makes a "no" determination in step 535 and proceeds directly to step 545. In this case, because the value of the automatic steering process execution flag XpcsS is retained at "0", the automatic steering process is not executed.

[0097] Next, the automatic steering process routine is described. The automatic steering process routine is illustrated by a flowchart in Fig. 6 represents. When a suitable time has arrived, the CPU starts the process from step 600 of Fig.6, and proceeds to step 605 to determine whether the value of the automatic steering process execution flag XpcsS is “1” or not.

[0098] In the case where the value of the automatic steering process execution flag XpcsS is not "1" (specifically, where the value of the automatic steering process execution flag XpcsS is "0"), the CPU makes a "no" determination in step 605 and proceeds directly to step 695 to terminate the current routine.

[0099] However, if the value of the automatic steering process execution flag XpcsS is “1”, the CPU makes a “YES” determination in step 605 and proceeds to step 610 to determine whether the magnitude |θs| of the steering angle θs is less than or equal to the second angle threshold θth2 or not.

[0100] If the magnitude |θs| of the steering angle θs is less than or equal to the second angle threshold θth2, the CPU makes a "YES" determination in step 610 and proceeds to step 615 to determine whether the end condition for terminating the collision avoidance control described above is not met. If the end condition for terminating the collision avoidance control is not met, the CPU makes a "YES" determination in step 615 and proceeds to step 620 to determine the target motor torque Tmtgt such that the vehicle 10 travels along the evasive path Rd.

[0101] The CPU then proceeds to step 625 and sends the target motor torque Tmtgt to the EPS-ECU 33 via CAN 34. As a result, the EPS-ECU 33 controls the control circuit 69 by executing a routine (not illustrated) so that the motor torque Tm actually generated by motor 71 equals the target motor torque Tmtgt. Consequently, vehicle 10 travels along the alternative route Rd. The CPU then proceeds to step 695.

[0102] However, if the determination condition of step 610 is not met (specifically, if the magnitude |θs| of the steering angle θs is greater than the second angle threshold θth2), the CPU makes a "NO" determination in step 610, then executes the processes of steps 630 to 645, and subsequently proceeds to step 695. In this case, the CPU determines that the driver operates the steering wheel 51 of the vehicle 10.

[0103] Step 630: The CDU stops the automatic braking process by executing a process identical to that of step 552.

[0104] Step 635: The CPU sets the value of the automatic braking process execution flag XpcsB to "0".

[0105] Step 640: The CPU stops the automatic steering process. Specifically, the CPU sets the target motor torque value Tmtgt to "0" and sends the target motor torque Tmtgt to the EPS-ECU 33. In this case, the EPS-ECU 33 controls the control circuit 69 such that the motor 71 generates a "torque equal to a target support torque Ta to assist the steering operation of the steering wheel 51 by the driver".

[0106] Step 645: The CPU sets the value of the automatic steering process execution flag XpcsS to "0".

[0107] In particular, if the determination condition of step 615 is not met (namely, if the termination condition to end the collision avoidance control is met), the CPU makes a "NO" determination in step 615, then executes the processes of steps 630 to 645, and then proceeds to step 695.

[0108] As described above, if only the automatic braking process is executed as the collision avoidance control, the collision avoidance ECU 20 stops the execution of the collision avoidance control (specifically the automatic braking process) if the magnitude |θs| of the steering angle θs is greater than the first angle threshold θtht1. However, if both the automatic braking process and the automatic steering process are executed as the collision avoidance control, the collision avoidance ECU 20 stops the execution of the collision avoidance control (specifically both the automatic braking process and the automatic steering process) if the magnitude |θs| of the steering angle θs is greater than the second angle threshold θth2.Therefore, the present assistance device can more appropriately determine whether the automatic braking process and the automatic steering process should be stopped in the case where the driver is attempting to avoid a collision with an obstacle by means of a steering operation.

[0109] An embodiment of the collision avoidance assistance device according to the present invention has been described; however, the present invention is not limited to the embodiment described above, and various modifications are possible without departing from the scope of the invention. For example, according to the present embodiment, the vehicle 10 has the millimeter-wave radar 41 and the front camera 42 for obtaining target information. However, the millimeter-wave radar 41 or the front camera 42 can be omitted. Furthermore, instead of or in addition to the millimeter-wave radar 41 and the front camera 42, the vehicle 10 can have an ultrasonic wave sonar and / or a laser radar.

[0110] Additionally, the time threshold Tth is a fixed value in the present embodiment. However, the time threshold Tth can vary according to the positional relationship between the vehicle 10 and an obstacle. For example, the time threshold Tth can be set such that its value increases with an overlap ratio calculated as the ratio of the length (in the lateral direction of the vehicle 10) of a section of the vehicle 10 that comes into contact with an obstacle when the vehicle 10 collides with the obstacle to the width Wo of the vehicle 10.

[0111] Alternatively, in the case where the obstacle is a continuous structure such as a side wall, guardrail or the like of a road, and the obstacle is inclined relative to the lateral direction of the vehicle 10, the time threshold Tth can be set such that its value increases with the angle (peak angle) between the direction of travel of the vehicle 10 and the "intersection point between a road surface and a surface of the obstacle facing the vehicle 10" (namely, the extent of an operation of the steering wheel 51 required to avoid the collision with the obstacle).

[0112] Additionally, the maximum deceleration Dcmax is a fixed value in the present embodiment. However, the maximum deceleration Dcmax can vary depending on the conditions. For example, if wheel slip occurs between the wheels of vehicle 10 and a road surface, and the target deceleration Dctgt gradually increases, the collision avoidance ECU 20 may apply a value as the maximum deceleration Dcmax that is slightly larger than the acceleration As at that time (the acceleration As has a negative value in this case); that is, a negative value whose absolute value is less than that of the acceleration As at that time.

[0113] Alternatively, if the slip that occurred between the wheels of vehicle 10 and the road surface ends as a result of a gradual reduction of the target deceleration Dctgt, the collision avoidance ECU 20 may apply a value slightly larger than the acceleration As at that time as the maximum deceleration Dcmax; that is, a negative value whose absolute value is less than that of the acceleration As at that time. In other words, vehicle 10 may include an anti-lock braking system. In such a case, the target deceleration of vehicle 10, determined when the anti-lock braking system is operating, is applied as the maximum deceleration Dcmax.

[0114] Additionally, in the present embodiment, the end condition for terminating the collision avoidance control is a condition that is met when the vehicle speed Vs is zero. However, the end condition can be a different condition. For example, the end condition can be a condition that is met when the vehicle speed Vs is zero and, additionally, when the collision time TTC exceeds the time threshold Tth due to movement of a target identified as an obstacle. In other words, in this case, the end condition is met either when the vehicle speed Vs is zero or when the collision time TTC exceeds the time threshold Tth due to movement of a target identified as an obstacle.

[0115] Additionally, when the collision avoidance ECU 20 executes the automatic steering process according to the present embodiment, the collision avoidance ECU 20 sets the target deceleration value Dctgt to the maximum deceleration Dcmax. However, when the collision avoidance ECU 20 executes the automatic steering process, the collision avoidance ECU 20 can set the target deceleration value Dctgt to a value greater than the maximum deceleration Dcmax; that is, a negative value whose absolute value is less than that of the maximum deceleration Dcmax.For example, in the case where it is determined that the driving distance of the vehicle 10 is preferably increased before stopping in order to avoid a collision with a target that differs from the target identified as an obstacle, the collision avoidance ECU 20 can set the amount |Dctgt | of the target deceleration Dctgt to a value that is less than the amount |Dcmax | of the maximum deceleration Dcmax when it performs the automatic steering process.

[0116] In the present embodiment, the second angle threshold θth2 is set to a larger value than the maximum steering angle θmax. However, the second angle threshold θth2 can be set to a value less than or equal to the maximum steering angle θmax, as long as the value is greater than the first angle threshold θth1.

[0117] In the present embodiment, the motor 71 generates a motor torque for rotating the steering shaft of the steering wheel 51. However, the motor 71 can generate a torque for moving back and forth a "rack, wherein a rack engages with a pinion connected to the steering shaft for an integrated rotation in between, and which changes the steering angles of the steerable wheels of the vehicle 10".

[0118] A collision avoidance assistance device is disclosed that can execute an automatic braking process and an automatic steering process to avoid a collision with an obstacle. If the magnitude of a steering angle exceeds a predetermined threshold, the collision avoidance assistance device determines that a driver intends to avoid the collision by a steering operation and stops the automatic braking and steering processes. However, in such a case, the automatic braking and steering processes can be stopped if the steering angle exceeds the threshold as a result of the execution of the automatic steering process.Considering that, if both the automatic braking process and the automatic steering process are being executed, the collision avoidance assistance device continues the automatic braking process and the automatic steering process even if the amount of the steering angle is greater than the predetermined threshold.

Claims

[1] Collision avoidance assistance device (20), comprising: an obstacle detection section for detecting an obstacle in a traveling direction of a vehicle (10); a steering angle sensor (68) for detecting, as a steering angle, the angle of rotation of a steering wheel (51) of the vehicle; and a collision avoidance control section that executes an automatic braking process of reducing the speed of the vehicle by controlling a braking device (66) of the vehicle when it is determined that the vehicle collides with the detected obstacle, and executes an automatic steering process in addition to the automatic braking process when it is determined that the vehicle cannot be stopped by the automatic braking process at a time before the vehicle reaches the obstacle, wherein the automatic steering process changes the steering angles of steerable wheels of the vehicle by controlling a steering device of the vehicle, which includes the steering wheel, wherein the collision avoidance control section is configured such that in the case where the collision avoidance control section executes the automatic braking process and does not execute the automatic steering process, the collision avoidance control section stops the execution of the automatic braking process when the magnitude of the detected steering angle becomes greater than a predetermined first angle threshold value; and in the case where the collision avoidance control section executes both the automatic braking process and the automatic steering process, the collision avoidance control section continues both the automatic braking process and the automatic steering process even if the magnitude of the detected steering angle becomes greater than the first angle threshold, and stops the execution of the automatic braking process and the execution of the automatic steering process when the magnitude of the detected steering angle becomes greater than a predetermined second angle threshold that is greater than the first angle threshold. [2] Collision avoidance assist device according to claim 1, wherein the collision avoidance control section is configured to control the steering device such that the amount of the steering angle does not become greater than a predetermined maximum steering angle when the collision avoidance control section executes the automatic steering process; and the collision avoidance control section applies a value smaller than the maximum steering angle as the first angle threshold and applies a value larger than the maximum steering angle as the second angle threshold. [3] The collision avoidance assist device according to claim 1 or 2, wherein the collision avoidance control section is configured to estimate, as a collision time, a time elapsed until the vehicle collides with the obstacle, and to determine that the vehicle collides with the obstacle when the estimated collision time is shorter than a predetermined time threshold. [4] A collision avoidance assist device according to claim 3, wherein the collision avoidance control section is configured such that if the estimated collision time is shorter than the time threshold, the collision avoidance control section determines a required deceleration necessary to avoid a collision with the obstacle; when the amount of required deceleration is less than or equal to the amount of maximum deceleration, the collision avoidance control section uses the required deceleration as a target deceleration, and when the amount of required deceleration is greater than the amount of maximum deceleration, the collision avoidance control section uses the maximum deceleration as the target deceleration; the collision avoidance control section executes the automatic braking process such that the actual deceleration of the vehicle becomes equal to the target deceleration; and When the amount of required deceleration is greater than the amount of maximum deceleration, the collision avoidance control section determines that the vehicle cannot be stopped by the automatic braking process at a time point before the vehicle reaches the obstacle. [5] The collision avoidance assist device according to claim 1 or 2, wherein the collision avoidance control section is configured such that, when the collision avoidance control section executes the automatic steering process, the collision avoidance control section controls the steering device to cause the vehicle to travel along an avoidance travel path that is a travel path of the vehicle for avoiding a collision with the obstacle.

Images