Collision avoidance support device and collision avoidance support program

Abstract

To provide a collision avoidance support device capable of preventing the behavior of a vehicle from becoming unstable attributed to automatic steering for avoiding a collision with an obstacle in a situation in which both stabilizers on the front and rear sides are in a non-connection state.SOLUTION: A collision avoidance support device is applied to a vehicle 102 equipped with clutch type front wheel side and rear wheel side stabilizers 62 and 64 controlled into a connection state and a non-connection state, and includes a control unit configured to calculate a target steering angle θt for causing the vehicle to travel along a target locus for avoiding a collision with an obstacle when there is an obstacle in front of the vehicle, and control an automatic steering device 44 for automatically steer steering wheels with the target steering angle. When both stabilizers on the front wheel side and rear wheel side are in the non-connection state, the control unit does not control the automatic steering device even when it determines that it is necessary to avoid the collision with the obstacle.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present invention relates to a collision avoidance assistance device and a collision avoidance assistance program for a vehicle. [Background technology]

[0002] A collision avoidance assist system using automatic steering is known as one type of driving assist system for vehicles such as automobiles. When it is necessary to avoid a collision with an obstacle ahead of the vehicle, the collision avoidance assist system calculates a target steering angle for driving the vehicle along a target trajectory for avoiding the collision with the obstacle, and controls the automatic steering device so that the steering angle becomes the target steering angle.

[0003] Vehicles such as automobiles are equipped with front and rear stabilizers to ensure the vehicle's roll rigidity. When the left and right wheels bounce and rebound in opposite phases, the stabilizer's torsion bar, which extends laterally across the vehicle, is twisted to generate an anti-roll moment, thereby ensuring the vehicle's handling stability.

[0004] One type of stabilizer is a clutch-type stabilizer in which a torsion bar portion is divided into left and right torsion bar portions, and the left and right torsion bar portions are connected and disconnected by an actuator. For example, Patent Document 1 listed below describes that the ride comfort of a vehicle when traveling on rough roads is improved by disconnecting the left and right torsion bar portions and controlling the torsion bar to a disconnected state. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Application Publication No. 07-186683 Summary of the Invention

[0006] [Problem to be solved by the invention] In a vehicle equipped with a clutch-type stabilizer, as will be described in detail later, the steering characteristics of the vehicle change depending on whether the stabilizer is engaged. When the steering characteristics of the vehicle change, the relationship between the steering angle and the vehicle's turning radius also changes. In particular, when both the front and rear stabilizers are disengaged, the vehicle's roll stiffness, and therefore its handling stability, decreases. Therefore, if automatic steering is performed in this situation to avoid a collision with an obstacle, the vehicle's traveling direction changes without relying on the driver's steering operation, which can easily cause the vehicle's behavior to become unstable.

[0007] The present invention aims to provide an improved collision avoidance assistance device that can prevent the vehicle's behavior from becoming unstable due to automatic steering being performed to avoid a collision with an obstacle when both the front and rear stabilizers are in a disconnected state.

[0008] [Means for solving the problems and effects of the invention] According to the present invention, there is provided a collision avoidance assistance device (100) that is applied to a vehicle (102) equipped with clutch-type front and rear wheel stabilizers (62, 64) that are controlled to be in a connected state and a disconnected state, and an automatic steering device (44) that automatically steers steering wheels (106FL, 106FR), and that includes a control unit (driving assistance ECU10) configured to, when it is determined (S10) that it is necessary to avoid a collision with an obstacle (108) in front of the vehicle, calculate (S20, S50, S60, S80, S90) a target control amount (target steering angle θt) for causing the vehicle to travel along a target trajectory (110) for avoiding a collision with the obstacle, and control (S110) the automatic steering device with the target control amount.

[0009] The control unit is configured not to control the automatic steering device (S120) when the front and rear wheel stabilizers (62, 64) are in a disconnected state (S30, S70), even if it determines that it is necessary to avoid a collision with an obstacle in front of the vehicle (S10).

[0010] Generally, the steering characteristics of a vehicle are set to a weak understeer characteristic (normal steer characteristic) by setting the roll stiffness toward the front wheels. That is, the roll stiffness provided by the stabilizer on the front wheels is set higher than the roll stiffness provided by the stabilizer on the rear wheels. Also, the center of gravity of the vehicle is located closer to the front wheels than the midpoint between the front and rear wheels. Therefore, when the stabilizers on the front and rear wheels are disconnected, the roll stiffness shifts toward the rear wheels compared to when the stabilizers on the front and rear wheels are connected, and it is thought that the steering characteristics of the vehicle change to a weak oversteer characteristic.

[0011] According to the present invention, the control unit is configured not to control the automatic steering device when the stabilizers on the front and rear wheels are in a disconnected state, even if it determines that it is necessary to avoid a collision with an obstacle in front of the vehicle.

[0012] With this configuration, it is possible to avoid the vehicle's direction of travel changing and vehicle behavior becoming unstable without relying on the driver's steering operation due to automatic steering being performed when the stabilizers on the front and rear wheels are in a disconnected state and the vehicle's roll rigidity, and therefore its handling stability, is reduced.

[0013] [Mode of the Invention] In one aspect of the present invention, when the stabilizers (62, 64) on the front and rear wheels are in a disconnected state (S30, S70), the control unit (driving assistance ECU 10) is configured not to calculate a target control amount for causing the vehicle to travel along a target trajectory even if it determines (S10) that it is necessary to avoid a collision with an obstacle in front of the vehicle.

[0014] According to the above aspect, when the stabilizers on the front and rear wheels are in a disconnected state and the automatic steering device is not controlled, it is possible to prevent the target control amount for driving the vehicle along the target trajectory from being calculated unnecessarily.

[0015] Furthermore, in another aspect of the present invention, when the stabilizers (62, 64) on the front and rear wheels are in a disconnected state (S30, S70), if the control unit (driving assistance ECU10) determines (S10) that it is necessary to avoid a collision with an obstacle (108) in front of the vehicle, it is configured to issue a warning (S120) that automatic steering to avoid a collision with the obstacle will not be performed.

[0016] According to the above aspect, an alarm is issued to inform the driver that automatic steering will not be performed to avoid a collision with an obstacle, so the driver is aware of this and can recognize that he or she must avoid a collision with an obstacle through his or her own driving operations.

[0017] Other objects, other features and attendant advantages of the present invention will be readily apparent from the following description of the preferred embodiments of the present invention, which is given with reference to the accompanying drawings. [Brief explanation of the drawings]

[0018] [Figure 1] 1 is a schematic configuration diagram showing a collision avoidance assistance device according to first to third embodiments; [Figure 2] FIG. 2 is a diagram showing stabilizers and an automatic steering device on the front and rear wheel sides. [Figure 3] 4 is a flowchart showing a collision avoidance assist control routine according to the first embodiment. [Figure 4] 10 is a flowchart showing a main part of a collision avoidance assist control routine according to a second embodiment. [Figure 5] 10 is a flowchart showing a collision avoidance assist control routine according to a third embodiment. [Figure 6] FIG. 10 is a diagram showing a target trajectory for avoiding a collision with an obstacle for various steering characteristics of a vehicle. DETAILED DESCRIPTION OF THE INVENTION

[0019] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A collision avoidance assistance device according to an embodiment of the present invention will be described in detail below with reference to the accompanying drawings.

[0020] As shown in Fig. 1, a collision avoidance assistance device 100 according to first to third embodiments of the present invention is applied to a vehicle 102 and includes a driving assistance ECU 10. The vehicle 102 may be an autonomous vehicle, and includes a drive ECU 20, a braking ECU 30, an electric power steering ECU 40, a meter ECU 50, and a stabilizer ECU 60. ECU refers to an electronic control unit that includes a microcomputer as its main component. In the following description, the electric power steering will be referred to as EPS.

[0021] The microcomputer of each ECU includes a CPU, ROM, RAM, read / write non-volatile memory (N / M), and an interface (I / F). The CPU performs various functions by executing instructions (programs, routines) stored in the ROM. Furthermore, these ECUs are interconnected via a Controller Area Network (CAN) 104 to enable data exchange (communication). Therefore, the detected values ​​of sensors (including switches) connected to a specific ECU are transmitted to other ECUs.

[0022] The driving assistance ECU 10 is a central control device that performs driving assistance control for a vehicle, such as collision avoidance assistance control, lane keeping control, etc. In the embodiment, the driving assistance ECU 10 executes collision avoidance assistance control in cooperation with other ECUs, as will be described in detail later.

[0023] The driving assistance ECU 10 is connected to a camera sensor 12 and a radar sensor 14. The camera sensor 12 and the radar sensor 14 each include a plurality of camera devices and a plurality of radar devices. The camera sensor 12 and the radar sensor 14 function as a target information acquisition device 16 that acquires information about targets around the vehicle 102.

[0024] Although not shown in the figure, each camera device of the camera sensor 12 includes a camera unit that captures images of the surroundings of the vehicle 102 and a recognition unit that analyzes image data captured by the camera unit to recognize targets such as white lines on the road and other vehicles. The recognition unit supplies information about the recognized targets to the driving assistance ECU 10 at predetermined time intervals.

[0025] Each radar device of the radar sensor 14 includes a radar transmitting / receiving unit and a signal processing unit (not shown). The radar transmitting / receiving unit emits millimeter-wave radio waves (hereinafter referred to as "millimeter waves") and receives millimeter waves reflected by a three-dimensional object (e.g., another vehicle, a bicycle, etc.) within the emission range (i.e., reflected waves). The signal processing unit acquires information indicating the relative distance and relative speed between the vehicle and the three-dimensional object, and the relative position (direction) of the three-dimensional object with respect to the vehicle at predetermined time intervals based on the phase difference between the emitted millimeter waves and the received reflected waves, the attenuation level of the reflected waves, and the time from when the millimeter waves are emitted until when the reflected waves are received, and supplies the information to the driving assistance ECU 10. Note that a LiDAR (Light Detection and Ranging) may be used instead of the radar sensor 14.

[0026] Furthermore, a setting operator 18 is connected to the driving assistance ECU 10, and the setting operator 18 is provided in a position where it can be operated by the driver. Although not shown in Fig. 1, the setting operator 18 includes a collision avoidance assist switch, and the driving assistance ECU 10 executes collision avoidance assist control when the collision avoidance assist switch is on. Note that the collision avoidance assist control may be executed regardless of whether the collision avoidance assist switch is on or not.

[0027] A drive unit 22 that accelerates the vehicle 102 by applying drive force to drive wheels not shown in Fig. 1 is connected to the drive ECU 20. Under normal circumstances, the drive ECU 20 controls the drive unit 22 so that the drive force generated by the drive unit 22 changes in response to the driving operation by the driver, and when a command signal is received from the driving assistance ECU 10, the drive ECU 20 controls the drive unit 22 based on the command signal.

[0028] The brake ECU 30 is connected to a brake device 32 that applies braking force to wheels (not shown in Fig. 1) to decelerate the vehicle 102. Normally, the brake ECU 30 controls the brake device 32 so that the braking force generated by the brake device 32 changes in response to the braking operation by the driver, and when a command signal is received from the driving assistance ECU 10, the brake ECU 30 controls the brake device 32 based on the command signal to perform automatic braking.

[0029] An EPS device 42 is connected to the EPS-ECU 40. The EPS-ECU 40 controls the steering assist torque and reduces the driver's steering burden by controlling the EPS device 42 in a manner known in the art based on the steering torque Ts and vehicle speed V detected by a driving operation sensor 70 and a vehicle state sensor 80 (described below). In addition, the EPS-ECU 40 can steer the steered wheels as needed by controlling the EPS device 42. Therefore, the EPS-ECU 40 and the EPS device 42 function as an automatic steering device 44 that automatically steers the steered wheels as needed.

[0030] An alarm device 52 is connected to the meter ECU 50. The alarm device 52 is activated when it is determined that the vehicle 102 needs to steer to avoid a collision with an obstacle ahead, and issues an alarm to the effect that steering to avoid a collision with the obstacle is necessary. The alarm device 52 may be any of an alarm device that issues a visual alarm such as a display or an alarm lamp, an alarm device that issues an auditory alarm such as an alarm buzzer, or an alarm device that issues a tactile alarm such as seat vibration, or any combination thereof.

[0031] The stabilizer ECU 60 is connected to a front stabilizer 62, a rear stabilizer 64, and a mode switch 66. The front stabilizer 62 and the rear stabilizer 64 include actuators 62A and 64A, respectively, which are controlled by the stabilizer ECU 60.

[0032] 2, the front stabilizer 62 is provided between the left and right front wheels 106FL and 106FR, and the rear stabilizer 64 is provided between the left and right rear wheels 106RL and 106RR. The front stabilizer 62 and the rear stabilizer 64 may be clutch-type stabilizers of any configuration known in the art, such as the stabilizer described in Japanese Patent Laid-Open No. 2000-289427.

[0033] The front stabilizer 62 includes a pair of torsion bar portions 62TL and 62TR extending coaxially in the lateral direction of the vehicle 102, and a pair of arm portions 62AL and 62AR integrally connected to the outer ends of the torsion bar portions 62TL and 62TR, respectively. The torsion bar portions 62TL and 62TR are supported by the vehicle body (not shown) via brackets (not shown) so as to be rotatable about their own axes. The arm portions 62AL and 62AR extend inclined in the longitudinal direction of the vehicle relative to the lateral direction of the vehicle so as to intersect with the torsion bar portions 62TL and 62TR, respectively. The outer ends of the arm portions 62AL and 62AR are connected to suspension members 49FL and 49FR, such as suspension arms, of the left and right front wheels 106FL and 106FR, via connecting links (not shown), respectively.

[0034] The actuator 62A is disposed between the torsion bar portions 62TL and 62TR, and functions as a clutch, controlled by the stabilizer ECU 60 in accordance with the position of the mode switch 66. When the mode switch 66 is in the connected position (standard position), the actuator 62A connects the torsion bar portions 62TL and 62TR (connected state). On the other hand, when the mode switch 66 is in the unconnected position, the actuator 62A does not connect the torsion bar portions 62TL and 62TR (unconnected state).

[0035] When the stabilizer 62 is in the disconnected state, the torsion bar portions 62TL and 62TR can rotate freely relative to each other, so no anti-roll moment is generated and the stabilizer does not function. Therefore, the roll rigidity of the front wheel side is reduced compared to when the stabilizer 62 is in the connected state. The actuator 62A supplies a signal indicating whether the stabilizer 62 is in the connected state or the disconnected state to the stabilizer ECU 60.

[0036] Each member of the rear stabilizer 64 is designated by 64 instead of 62. For example, torsion bar portions corresponding to the torsion bar portions 62TL and 62TR are designated by the reference numerals 64TL and 64TR. The rear stabilizer 64 is configured similarly to the front stabilizer 62 and operates similarly. When the stabilizer 64 is in the uncoupled state, the roll rigidity on the rear wheel side is reduced compared to when the stabilizer 64 is in the coupled state.

[0037] When the mode switch 66 is changed from the coupled position to the uncoupled position, the front stabilizer 62 and the rear stabilizer 64 are switched from the coupled state to the uncoupled state by the actuators 62A and 64A, respectively. However, even when the mode switch 66 is changed from the uncoupled position to the coupled position, the stabilizers 62 and 64 do not return from the uncoupled state to the coupled state until the magnitudes of bounce and rebound of the left and right wheels become the same, that is, until the relative rotation of the left and right torsion bar portions becomes zero. Therefore, in the state before returning to the coupled state, the stabilizers 62 and 64 do not generate an anti-roll moment, just like in the uncoupled state.

[0038] The driving operation sensor 70 and the vehicle condition sensor 80 are connected to the CAN 104. Information detected by the driving operation sensor 70 and the vehicle condition sensor 80 (referred to as sensor information) is transmitted to the CAN 104. The sensor information transmitted to the CAN 104 can be used appropriately in each ECU. Note that the sensor information may be information from a sensor connected to a specific ECU and transmitted to the CAN 104 from that specific ECU.

[0039] The driving operation sensors 70 include a driving operation amount sensor and a braking operation amount sensor. The driving operation sensors 70 also include a steering angle sensor, a steering torque sensor, etc. The vehicle state sensors 80 include a vehicle speed sensor, a longitudinal acceleration sensor, a lateral acceleration sensor, a yaw rate sensor, etc.

[0040] In the first to third embodiments, the ROM of the driving assistance ECU 10 stores programs for collision avoidance assistance control corresponding to the flowcharts shown in Figures 3 to 5, respectively. The CPU executes the collision avoidance assistance control according to the first to third embodiments in accordance with these programs.

[0041] <Collision Avoidance Assistance Control Routine in the First Embodiment> The collision avoidance assist control according to the flowchart shown in FIG. 3 is executed by the CPU of the driving assist ECU 10 when a collision avoidance assist switch (not shown in FIG. 1) of the setting operation unit 18 is turned on.

[0042] First, in step S10, the CPU determines, in a manner known in the art, whether an obstacle has been detected ahead of the vehicle 102 by the target information acquisition device 16 and whether automatic steering is necessary to avoid a collision with the obstacle. If the CPU makes a negative determination, it temporarily terminates this control, and if the CPU makes a positive determination, it proceeds to step S20.

[0043] In step S20, the CPU sets a target trajectory for the vehicle 102 to travel while avoiding a collision with the obstacle, based on the positional relationship and relative speed between the vehicle 102 and the obstacle, in a manner known in the art. Note that step S20 may be skipped if the time elapsed since the previous target trajectory was set is less than a reference value (a positive constant). Furthermore, when the target trajectory cannot be set, such as when the target trajectory is unavoidably going outside the lane in a lane where lane departure is prohibited, the warning device 52 may be activated to issue a warning that the target trajectory cannot be set and automatic steering to avoid a collision will not be performed.

[0044] In step S30, the CPU determines whether the front stabilizer 62 is in the coupled state. If the CPU makes a negative determination, it proceeds to step S70, and if the CPU makes a positive determination, it proceeds to step S40. Note that if the mode switch 66 has changed from the uncoupled position to the coupled position but the stabilizer 62 has not yet returned from the uncoupled state to the coupled state, a negative determination is made.

[0045] In step S40, the CPU determines whether the rear stabilizer 64 is in the coupled state. If the CPU makes a negative determination, the control proceeds to step S60. If the CPU makes a positive determination, the control proceeds to step S50. Note that if the mode switch 66 has changed from the uncoupled position to the coupled position but the stabilizer 64 has not yet returned from the uncoupled state to the coupled state, a negative determination is made. The same applies to step S70, which will be described later.

[0046] In step S50, the CPU calculates a target steering angle θt for causing the vehicle 102 to travel along the target trajectory from the present until a predetermined time has elapsed, based on the normal steering characteristics of the vehicle. The normal steering characteristics of the vehicle are the steering characteristics when the front stabilizer 62 and the rear stabilizer 64 are in a coupled state.

[0047] In step S60, the CPU calculates a target steering angle θt for causing the vehicle 102 to travel along the target trajectory from the present until a predetermined time has elapsed, based on the understeer characteristics of the vehicle. The understeer characteristics of the vehicle are steering characteristics when the front stabilizer 62 is in the coupled state and the rear stabilizer 64 is in the uncoupled state.

[0048] In step S70, similarly to step S40, the CPU determines whether or not the rear stabilizer 64 is in the connected state. If the CPU makes a negative determination, the control proceeds to step S90, and if the CPU makes a positive determination, the control proceeds to step S80.

[0049] In step S80, the CPU calculates a target steering angle θt for causing the vehicle 102 to travel along the target trajectory from the present until a predetermined time has elapsed, based on the oversteer characteristics of the vehicle. The oversteer characteristics of the vehicle are steering characteristics when the front stabilizer 62 is in the uncoupled state and the rear stabilizer 64 is in the coupled state.

[0050] In step S90, the CPU calculates a target steering angle θt for causing the vehicle 102 to travel along the target trajectory from the present until a predetermined time has passed, based on the weak oversteer characteristic of the vehicle. The weak oversteer characteristic of the vehicle is the steering characteristic when the front stabilizer 62 and the rear stabilizer 64 are in a non-connected state.

[0051] When step S50, S60, S80, or S90 is completed, the CPU advances this control to step S110. In step S110, the CPU activates the warning device 52 to issue a warning, and outputs a command signal to the EPS-ECU 40 so that the steering angle θ becomes the target steering angle θt. The warning may be a warning that there is an obstacle ahead and that automatic steering will be performed to avoid a collision with the obstacle.

[0052] In steps S50, S60, S80, and S90, for example, the turning radius of the target trajectory from the present until a predetermined time later may be calculated as the target turning radius, and the target steering angle θt may be calculated as the steering angle for making the turning radius of the vehicle 102 the target turning radius. Therefore, the steering characteristics in these steps may be the relationship between the turning radius and the steering angle θ of the vehicle 102 when the front stabilizer 62 and the rear stabilizer 64 are in the corresponding coupled state or uncoupled state. This relationship is determined by the vehicle specifications, and may be obtained in advance for each vehicle specification.

[0053] As can be seen from the above explanation, according to the first embodiment, when it is determined that it is necessary to avoid a collision with an obstacle ahead of the vehicle (S10) and it is determined that at least one of the stabilizers is in a non-connected state (S30, S40, S70), a target steering angle θt is calculated as a target control amount for causing the vehicle to travel along a target trajectory based on the steering characteristics of the vehicle when at least one of the stabilizers is in a non-connected state (S60, S80, S90).

[0054] Therefore, even if at least one of the stabilizers is in the disconnected state and the steering characteristics of the vehicle differ from the steering characteristics of the vehicle when both stabilizers are in the connected state, the target steering angle θt can be calculated to be the steering angle for making the vehicle travel along the target trajectory. Therefore, even when at least one of the front and rear stabilizers is in the disconnected state, the vehicle can travel along the target trajectory to avoid a collision with an obstacle.

[0055] <Collision Avoidance Assistance Control Routine in the Second Embodiment> 4 and 3, the CPU executes steps S10 to S40, S70, and S110 in the same manner as in the first embodiment. However, in step S40, if the CPU makes a positive determination, the control proceeds to step S100, and if the CPU makes a negative determination, the control proceeds to step S65. Also, in step S70, if the CPU makes a negative determination, the control proceeds to step S95, and if the CPU makes a positive determination, the control proceeds to step S85.

[0056] In step S65, the CPU modifies the target trajectory set in step S20 based on the understeer characteristics of the vehicle. As in step S60, the understeer characteristics of the vehicle are the steering characteristics when the front stabilizer 62 is in the connected state and the rear stabilizer 64 is in the disconnected state.

[0057] For example, the solid line in Fig. 6 indicates a target trajectory 110 for the vehicle to avoid a collision with an obstacle 108 such as a motorcycle when the front stabilizer 62 and the rear stabilizer 64 are coupled and the steering characteristics of the vehicle 102 are normal steering characteristics. When the steering characteristics of the vehicle 102 are understeer characteristics, the turning radius of the vehicle becomes larger compared to when the steering characteristics of the vehicle are normal steering characteristics. Therefore, in step S65, the target trajectory is corrected so that it starts to change earlier than the target trajectory 110 and the amount of change is larger than that of the target trajectory 110, as shown by the dashed line in Fig. 6.

[0058] In step S85, the CPU modifies the target trajectory set in step S20 based on the oversteer characteristics of the vehicle, which are the steering characteristics when the front stabilizer 62 is in the uncoupled state and the rear stabilizer 64 is in the coupled state.

[0059] When the steering characteristics of the vehicle 102 are oversteer characteristics, the turning radius of the vehicle is smaller than when the steering characteristics of the vehicle are normal steer characteristics. Therefore, in step S85, the target trajectory is corrected so that it starts to change later than the target trajectory 110, and the amount of change is smaller than that of the target trajectory 110, as shown by the dashed dotted line in Figure 6.

[0060] In step S95, the CPU modifies the target trajectory set in step S20 based on the weak oversteer characteristics of the vehicle. The weak oversteer characteristics of the vehicle are the steering characteristics when the front stabilizer 62 and the rear stabilizer 64 are in a disconnected state.

[0061] When the steering characteristics of the vehicle 102 are weak oversteer characteristics, the turning radius of the vehicle is slightly smaller than when the steering characteristics of the vehicle are normal steer characteristics. Therefore, in step S95, the target trajectory is corrected so that it starts to change slightly later than the target trajectory 110, and the amount of change is slightly smaller than the target trajectory 110, as shown by the two-dot chain line in Figure 6.

[0062] When step S65, S85, or S95 is completed, the CPU advances this control to step S100. In step S100, the CPU calculates a target steering angle θt for causing the vehicle 102 to travel along the corrected target trajectory from the present until a predetermined time has elapsed, based on the normal steering characteristics of the vehicle. Note that if a positive determination is made in step S40, the target trajectory is not corrected, and therefore the target steering angle θt is calculated using the target trajectory set in step S20 as the corrected target trajectory.

[0063] As can be seen from the above description, according to the second embodiment, when at least one stabilizer is in a non-coupled state, the target trajectory 110 is corrected based on the steering characteristics of the vehicle 102 at that time (S65, S85, S95). Furthermore, the target steering angle θt for causing the vehicle to travel along the corrected target trajectories 110A to 110C is calculated (S100), whereby the target steering angle θt for causing the vehicle to travel along the target trajectory is calculated based on the steering characteristics of the vehicle when at least one stabilizer is in a non-coupled state.

[0064] Therefore, similar to the first embodiment in which the target steering angle θt for causing the vehicle to travel along the target trajectory is calculated based on the steering characteristics of the vehicle 102 when at least one of the stabilizers is in the uncoupled state, the target steering angle θt for causing the vehicle to travel along the target trajectory can be calculated based on the steering characteristics of the vehicle. Therefore, even when at least one of the front and rear stabilizers 62, 64 is in the uncoupled state, the vehicle 102 can be caused to travel along the target trajectory 110 for avoiding a collision with the obstacle 108.

[0065] <Collision Avoidance Assistance Control Routine in the Third Embodiment> As can be seen from a comparison between Fig. 5 and Fig. 3, the CPU executes steps S10 to S80 and S110 in the same manner as in the first embodiment, except that in step S70, if the CPU makes a positive determination, the control proceeds to step S80, and if the CPU makes a negative determination, the control proceeds to step S120.

[0066] In step S120, the CPU activates the warning device 52 to issue a warning, but does not calculate the target steering angle θt for driving the vehicle along the target trajectory or control the steering angle based on the target steering angle, and therefore does not perform automatic steering to avoid a collision. The warning may be a warning that there is an obstacle ahead, but automatic steering to avoid a collision with the obstacle will not be performed. Furthermore, when the front and rear stabilizers 62, 64 are in a disconnected state due to a malfunction, the warning may include a warning that the stabilizers are malfunctioning.

[0067] As can be seen from the above explanation, according to the third embodiment, when the stabilizers 62, 64 on the front and rear wheels are in a non-connected state, even if it is determined that it is necessary to avoid a collision with an obstacle 108 in front of the vehicle 102, the target steering angle θt is not calculated and the automatic steering device is not controlled at the target steering angle θt. Therefore, automatic steering is performed in a situation where both stabilizers are in a non-connected state and the roll rigidity of the vehicle, and therefore the handling stability, is reduced, and it is possible to prevent the vehicle's traveling direction from changing and the vehicle's behavior from becoming unstable without relying on the driver's steering operation.

[0068] In addition, when the stabilizers on the front and rear wheels are in a disconnected state and the automatic steering device is not controlled, the target control amount for driving the vehicle along the target trajectory is not calculated, so that it is possible to prevent the target control amount from being calculated in vain. Furthermore, since an alarm is issued to inform the driver that automatic steering to avoid a collision with an obstacle will not be performed, the driver is made aware of this and can recognize that he or she must avoid a collision with the obstacle by driving the vehicle himself or herself.

[0069] Although the present invention has been described in detail above with reference to specific embodiments, it will be apparent to those skilled in the art that the present invention is not limited to the above-described embodiments, and that various other embodiments are possible within the scope of the present invention.

[0070] For example, the target control amount for driving the vehicle along a target trajectory to avoid a collision with an obstacle may be a target steering angle of the steering wheels, and the steering angle of the steering wheels may be controlled to be the target steering angle in step S110.

[0071] Furthermore, if a negative determination is made in step S70 of the second embodiment, step S120 of the third embodiment may be executed (a modified example of the second embodiment). According to this modified example, when the front stabilizer 62 and the rear stabilizer 64 are in a non-connected state, the same effects as those of the third embodiment can be obtained.

[0072] Furthermore, the deterioration of steering stability in a state in which the front and rear stabilizers 62, 64 are in a disconnected state becomes more pronounced as the steering angle increases and the vehicle speed increases. Therefore, even if a negative determination is made in step S70, step S90 or S95 may be executed when the vehicle speed is equal to or less than a reference value (a positive constant), and step S120 may be executed when the vehicle speed exceeds the reference value. [Explanation of symbols]

[0073] 10... Driving assistance ECU, 16... Target information acquisition device, 44... Automatic steering device, 60... Stabilizer ECU, 62... Front stabilizer, 64... Rear stabilizer, 70... Driving operation sensor, 80... Vehicle state sensor, 100... Collision avoidance assistance device, 102... Vehicle (host vehicle), 108... Obstacle, 110... Target trajectory, 110A to 110C... Corrected target trajectory

Claims

1. A collision avoidance support device that is applied to a vehicle equipped with clutch-type front and rear wheel stabilizers that are controlled to be in a connected state and a disconnected state, and an automatic steering device that automatically steers the steering wheels, and that includes a control unit that, when it is determined that it is necessary to avoid a collision with an obstacle in front of the vehicle, calculates a target control amount for causing the vehicle to travel along a target trajectory for avoiding a collision with the obstacle, and controls the automatic steering device with the target control amount, A collision avoidance assistance device configured so that the control unit does not control the automatic steering device when the stabilizers on the front and rear wheels are in a disconnected state, even if it determines that it is necessary to avoid a collision with an obstacle in front of the vehicle.

2. 2. The collision avoidance assistance device according to claim 1, wherein the control unit is configured not to calculate a target control amount for causing the vehicle to travel along the target trajectory when the stabilizers on the front wheel side and the rear wheel side are in a non-connected state, even if it determines that it is necessary to avoid a collision with an obstacle in front of the vehicle.

3. 2. A collision avoidance assistance device according to claim 1, wherein the control unit is configured to issue a warning that automatic steering to avoid a collision with an obstacle will not be performed when the control unit does not control the automatic steering device.

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