Vehicle control devices

Abstract

The present invention provides a vehicle control device that stabilizes vehicle behavior and reduces the driver's sense of discomfort when the driver overrides the steering operation during automatic steering control. The vehicle control device is configured to include a steering device that steers the vehicle's front wheels via an actuator, a steering control unit that automatically steers the vehicle by controlling the steering device based on a target driving trajectory, a steering input unit to which the driver inputs the steering operation, a front-rear driving force distribution unit that can change the distribution ratio of driving force transmitted from the front and rear wheels to the road surface, and, when the steering control unit performs automatic steering, predicts the behavior of the vehicle after the steering operation corresponding to the steering operation based on the steering input unit, and, when oversteer behavior exceeding a predetermined magnitude is predicted, changes the distribution ratio of driving force by the front-rear driving force distribution unit to be biased toward the front wheels compared to a case where no oversteer behavior is predicted.

Description

Technical Field

[0001] The present invention relates to a vehicle control device for controlling the steering and driving force distribution of a vehicle. Background Art

[0002] In vehicles such as four-wheeled automobiles, a steering angle is applied to the front wheels according to the amount of operation of a steering wheel or the like input by a driver, and a slip angle and a turning force are generated in the tires to steer the vehicle.

[0003] In addition, in driving assistance controls such as lane keeping assist control and automatic driving control in which the vehicle drives autonomously, which have become popular in recent years, the environment around the vehicle (road shape and / or obstacles, etc.) is identified to set a target driving trajectory, and the vehicle is automatically steered in such a way that it tracks the target driving trajectory.

[0004] Among vehicles that perform such driving assistance control and automatic driving control, there are vehicles that are configured to accept steering operations performed by the driver as override (manual intervention in automatic control) even during automatic steering control, for example, to avoid sudden obstacles, and the driver can arbitrarily correct the driving trajectory.

[0005] In a vehicle that performs steering control, as a prior art related to control when the driver overrides the steering operation, for example, Patent Document 1 describes a steering assist device that calculates an auxiliary control amount of the steering angle based on information such as road shape acquired in advance and performs steering control based on the auxiliary control amount.

[0006] Cited document 1 states that when the driver performs a sudden steering operation to avoid an obstacle, etc., and the driver wants to cope with a situation that was not taken into account in the calculation of the auxiliary control amount, in order to prevent the driver's steering operation from being hindered by the steering control, when the steering direction based on the control and the steering direction input from the steering wheel are in opposite directions, the auxiliary control amount is adjusted so that it is smaller than when they are in the same direction.

[0007] Prior art literature

[0008] Patent Literature

[0009] Patent Document 1: Japanese Patent Application Laid-Open No. 2018-20586 Summary of the Invention

[0010] Technical issues

[0011] For example, when performing automatic steering based on steering control as in autonomous driving, if the driver operates the steering wheel or the like to perform steering operations beyond the control, the vehicle may sometimes exhibit unstable behavior such as oversteering or understeering due to the steering operations.

[0012] In contrast, for example, in the case of automatic steering, it is also possible to consider slowing down the steering gear ratio to suppress manual steering, or prohibiting steering operations that override the control (so that the steering angle does not exceed the indicated steering angle indicated by the automatic steering control). However, in this case, although the operation is input, it is not reflected in the actual steering angle (tire toe angle), so there is a concern that it will cause a sense of discomfort to the driver.

[0013] In view of the above problems, an object of the present invention is to provide a vehicle control device that stabilizes vehicle behavior when a driver overrides the steering control during automatic steering control and reduces the driver's sense of discomfort.

[0014] Technical Solution

[0015] The present invention solves the above-mentioned problems through the following technical solutions.

[0016] In the first embodiment of the present invention, the vehicle control device is characterized in that it comprises: a steering device for steering the front wheels of the vehicle through an actuator; a steering control unit for controlling the steering device according to the target driving trajectory of the vehicle to automatically steer the vehicle; a steering input unit for inputting steering operation by the driver; a front and rear drive force distribution unit for changing the distribution ratio of the drive force transmitted from the front wheels and the rear wheels to the road surface respectively; and a behavior control unit for predicting the behavior of the vehicle after steering corresponding to the steering operation when the steering operation is performed using the steering input unit when steering is automatically performed by the steering control unit, and when the occurrence of oversteering behavior of a predetermined magnitude or greater is predicted, changing the distribution ratio of the drive force based on the front and rear drive force distribution unit to be biased towards the front wheel side relative to the case where the occurrence of the oversteering behavior is not predicted.

[0017] Accordingly, when the driver overrides the input of steering operation during the automatic steering control process and the occurrence of oversteering behavior caused by this is predicted, the distribution ratio of the driving force between the front wheels and the rear wheels is changed to be biased towards the front wheels, thereby enhancing the understeering tendency caused by the driving force and preventing the occurrence of oversteering behavior that makes the vehicle unstable.

[0018] Furthermore, since the front wheels are steered in accordance with the driver's steering operation at this time, the driver does not feel a sense of discomfort due to steering not being performed in accordance with the steering operation.

[0019] In the first embodiment of the present invention, the vehicle control device can be configured to further include left and right driving force distribution units, which can change the distribution ratio of the driving force transmitted from the left and right front wheels or the left and right rear wheels to the road surface respectively. When the occurrence of the oversteering behavior is predicted, the behavior control unit will change the distribution ratio of the driving force based on the left and right driving force distribution units to be biased towards the inner wheel side of the turn relative to the case where the occurrence of the oversteering behavior is not predicted.

[0020] In the second embodiment of the present invention, the vehicle control device is characterized in that it comprises: a steering device for steering the front wheels of the vehicle through an actuator; a steering control unit for controlling the steering device according to the target driving trajectory of the vehicle to automatically steer the vehicle; a steering input unit for inputting steering operation by the driver; a left and right driving force distribution unit for changing the distribution ratio of the driving force transmitted from the left and right front wheels or the left and right rear wheels to the road surface respectively; and a behavior control unit for predicting the behavior of the vehicle after steering corresponding to the steering operation when the steering operation is performed using the steering input unit when steering is automatically performed by the steering control unit, and when the occurrence of oversteering behavior of a predetermined magnitude or greater is predicted, changing the distribution ratio of the driving force based on the left and right driving force distribution units to be biased towards the inner wheel side of the turning relative to the case where the occurrence of the oversteering behavior is not predicted.

[0021] According to these inventions, when the driver overrides the input of a steering operation during the automatic steering control process and the occurrence of oversteering behavior caused by this is predicted, the distribution ratio of the driving force between the inner turning wheel and the outer turning wheel is changed to be biased towards the inner turning wheel, thereby generating a yaw moment in a direction that suppresses the oversteering tendency, thereby preventing the occurrence of oversteering behavior and destabilizing the vehicle.

[0022] Furthermore, since the front wheels are steered in accordance with the driver's steering operation at this time, the driver does not feel a sense of discomfort due to steering not being performed in accordance with the steering operation.

[0023] In the third embodiment of the present invention, the vehicle control device is characterized in that it comprises: a steering device for steering the front wheels of the vehicle through an actuator; a steering control unit for controlling the steering device according to the target driving trajectory of the vehicle to automatically steer the vehicle; a steering input unit for inputting steering operation by the driver; a front and rear drive force distribution unit for changing the distribution ratio of the drive force transmitted from the front wheels and the rear wheels to the road surface respectively; and a behavior control unit for predicting the behavior of the vehicle after steering corresponding to the steering operation when the steering operation is performed using the steering input unit when steering is automatically performed by the steering control unit, and when the occurrence of understeering behavior of a predetermined magnitude or greater is predicted, changing the distribution ratio of the drive force based on the front and rear drive force distribution unit to be biased towards the rear wheel side relative to the case where the occurrence of the understeering behavior is not predicted.

[0024] Accordingly, when the driver overrides the input of steering operation during the automatic steering control process and predicts the occurrence of understeering behavior caused by this, the distribution ratio of the driving force between the front wheels and the rear wheels is changed to be biased towards the front wheels, thereby enhancing the oversteering tendency caused by the driving force and preventing the occurrence of understeering behavior that makes the vehicle unstable.

[0025] Furthermore, since the front wheels are steered in accordance with the driver's steering operation at this time, the driver does not feel a sense of discomfort due to steering not being performed in accordance with the steering operation.

[0026] In the third embodiment of the present invention, the vehicle control device can be configured to further include left and right driving force distribution units, which can change the distribution ratio of the driving force transmitted from the left and right front wheels or the left and right rear wheels to the road surface respectively. When the occurrence of the understeering behavior is predicted, the behavior control unit will change the distribution ratio of the driving force based on the left and right driving force distribution units to be biased towards the turning outer wheel side relative to the case where the occurrence of the understeering behavior is not predicted.

[0027] In the fourth embodiment of the present invention, the vehicle control device is characterized in that it comprises: a steering device for steering the front wheels of the vehicle through an actuator; a steering control unit for controlling the steering device according to the target driving trajectory of the vehicle to automatically steer the vehicle; a steering input unit for inputting steering operation by the driver; a left and right driving force distribution unit for changing the distribution ratio of the driving force transmitted from the left and right front wheels or the left and right rear wheels to the road surface respectively; and a behavior control unit for predicting the behavior of the vehicle after steering corresponding to the steering operation when the steering operation is performed using the steering input unit when steering is automatically performed by the steering control unit, and when the occurrence of understeering behavior of a predetermined size or greater is predicted, the distribution ratio of the driving force based on the left and right driving force distribution units is changed to be biased towards the turning outer wheel side relative to the case where the occurrence of the understeering behavior is not predicted.

[0028] According to these inventions, if the driver overrides the input of a steering operation during the automatic steering control process and the occurrence of understeer behavior caused by this is predicted, the distribution ratio of the driving force between the inner turning wheel and the outer turning wheel is changed to be biased towards the outer turning wheel, thereby generating a yaw moment in a direction that suppresses the understeer tendency, thereby preventing the occurrence of understeer behavior and destabilizing the vehicle.

[0029] Furthermore, since the front wheels are steered in accordance with the driver's steering operation at this time, the driver does not feel a sense of discomfort due to steering not being performed in accordance with the steering operation.

[0030] Technical Effects

[0031] As described above, according to the present invention, it is possible to provide a vehicle control device that stabilizes the vehicle behavior when the driver overrides the steering operation during automatic steering control and reduces the driver's sense of discomfort. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] Figure 1 It is a diagram schematically showing the configuration of a vehicle including a first embodiment of the vehicle control device to which the present invention is applied.

[0033] Figure 2 It is a diagram schematically showing the configuration of a steering device of a vehicle including the vehicle control device according to the first embodiment.

[0034] Figure 3 This is a flowchart showing control during automatic steering in the vehicle control device according to the first embodiment.

[0035] Figure 4 This is a diagram showing an example of changes in the steering angle, yaw rate, and front-rear drive force distribution ratio of a vehicle equipped with the vehicle control device according to the first embodiment.

[0036] Figure 5 1 is a diagram schematically showing a state of a vehicle equipped with the vehicle control device according to the first embodiment after an override steering operation is performed.

[0037] Figure 6 1 is a diagram schematically showing another state of the vehicle including the vehicle control device according to the first embodiment after the overriding steering operation is performed.

[0038] Figure 7 It is a diagram schematically showing a state of a vehicle having a second embodiment of a vehicle control device to which the present invention is applied, after an override steering operation is performed.

[0039] Figure 8 1 is a diagram schematically showing another state of the vehicle including the vehicle control device according to the second embodiment after the overriding steering operation is performed.

[0040] Explanation of symbols

[0041] 1: Vehicle 10: Engine

[0042] 20: Torque converter 30: Speed ​​change mechanism

[0043] 40: AWD transfer case 41: Center differential

[0044] 42: Transfer clutch 50: Front differential

[0045] 51: right front wheel 52: left front wheel

[0046] 60: Rear differential 61: Right rear wheel

[0047] 62: Left rear wheel 70: Braking device

[0048] 71: Brake pedal 72: Master cylinder

[0049] 73: Hydraulic Control Unit (HCU)

[0050] 74: Brake FR 75: Brake FL

[0051] 76: Brake RR 77: Brake RL

[0052] 110: Engine control unit 120: Transmission control unit

[0053] 130: Steering control unit 140: Braking control unit

[0054] 150: Automatic driving control unit 151: Driving trajectory setting unit

[0055] 152: Target steering angle setting unit 153: Behavior prediction unit

[0056] 160: Environmental Identification Unit

[0057] 200: Steering device 210: Steering wheel

[0058] 211: Steering shaft 212: Steering angle sensor

[0059] 213: Torque sensor 220: Reaction force generating device

[0060] 230: Rack shaft 231: Rack gear

[0061] 240: Rack housing 241: Rack protection cover

[0062] 250: Tie rod 251: Ball joint

[0063] 252: Ball joint 260: Housing

[0064] 270: Actuator unit 271: Motor

[0065] 272: Gearbox 273: Pinion shaft DETAILED DESCRIPTION

[0066] <First embodiment>

[0067] Hereinafter, a first embodiment of a vehicle control device to which the present invention is applied will be described.

[0068] The vehicle control device according to the first embodiment is provided in, for example, an automobile such as an all-wheel drive (AWD) four-wheel passenger car with the front wheels serving as steerable wheels.

[0069] Figure 1 It is a diagram schematically showing the configuration of a vehicle including the vehicle control device according to the first embodiment.

[0070] like Figure 1 As shown, the vehicle 1 includes an engine 10 , a torque converter 20 , a speed change mechanism 30 , an AWD transfer case 40 , a front differential 50 , a rear differential 60 , and the like.

[0071] The engine 10 is a driving power source for the vehicle 1 , and is, for example, an internal combustion engine such as a gasoline engine.

[0072] The torque converter 20 is a fluid connector that transmits the output of the engine 10 to the speed change mechanism 30 , and functions as a starting device that enables the vehicle to start from zero vehicle speed.

[0073] The torque converter 20 includes a lock-up clutch that directly connects the input side and the output side.

[0074] The transmission mechanism 30 is, for example, a continuously variable transmission (CVT) having a transmission composed of a pair of variable pulleys, a chain, and a belt, or a stepped automatic transmission having a multi-row planetary gear set, and accelerates or decelerates the output of the engine 10 input from the torque converter 20. The transmission mechanism 30 and the torque converter 20 cooperate to form a transmission.

[0075] The AWD transfer case 40 is a driving force transmission device that distributes the driving force input from the speed change mechanism portion 30 and transmits the distributed driving force to the front differential 50 and the rear differential 60 .

[0076] The AWD transfer case 40 is configured to include a center differential 41 , a transfer clutch 42 , and the like.

[0077] The center differential 41 is configured, for example, with a compound planetary gear set, and serves as a driving force distribution mechanism that distributes torque between the front differential 50 and the rear differential 60 so that the torque distribution ratio is approximately 35:65. Furthermore, the center differential 41 also functions as a differential mechanism that absorbs rotational differences between the front differential 50 and the rear differential 60 caused by, for example, differences in front and rear wheel tracks during cornering.

[0078] The transfer clutch 42 is a differential limiting mechanism that limits the differential between the front and rear wheel output portions of the center differential 41. The transfer clutch 42 comprises, for example, a wet multi-plate clutch driven by hydraulic pressure or electromagnetic force, and its engagement force (clutch contact force), i.e., differential limiting torque, is controlled by the transmission control unit 120, described below.

[0079] The AWD transfer case 40 can adjust the driving force distribution ratio between the front and rear wheels from, for example, 35:65 (most rear-wheel-biased state) to 50:50 (most front-wheel-biased state) by adjusting the engagement force of the transfer case clutch 42.

[0080] As for the driving force distribution ratio between the front wheel side and the rear wheel side, under normal circumstances (when the oversteer suppression control and understeer suppression control described later are not intervened), the transmission control unit 120 uses the intermediate value of the above-mentioned distributions (as an example, 45:55, etc.) as the basic value, and performs corrections based on the vehicle's acceleration state, climbing state, turning state, etc.

[0081] The front differential 50 is a device that finally reduces the front wheel driving force transmitted from the AWD transfer case 40 and transmits it to the right front wheel 51 and the left front wheel 52. The front differential 50 also functions as a differential mechanism that absorbs the rotational difference between the right front wheel 51 and the left front wheel 52.

[0082] The rear differential 60 is a device that finally reduces the rear wheel drive force transmitted from the AWD transfer case 40 and transmits it to the right rear wheel 61 and the left rear wheel 62. The rear differential 60 also functions as a differential mechanism that absorbs the rotational difference between the right rear wheel 61 and the left rear wheel 62.

[0083] Furthermore, the vehicle is provided with a brake device 70 as a brake device.

[0084] The brake device 70 includes a brake pedal 71 , a master cylinder 72 , a hydraulic control unit (HCU) 73 , a brake FR 74 , a brake FL 75 , a brake RR 76 , a brake RL 77 , and the like.

[0085] The brake pedal 71 is an input unit for the driver to perform a brake operation.

[0086] The master cylinder 72 is connected to the brake pedal 71 and pressurizes the brake fluid in response to depression of the brake pedal 71. The master cylinder 72 is provided with a vacuum booster that amplifies the input from the brake pedal 71 using the negative pressure of the intake pipe of the engine 10.

[0087] The hydraulic control unit 73 is a device that individually increases or decreases the hydraulic pressure of the brake fluid supplied to the wheel cylinder of each wheel in order to perform, for example, anti-lock brake control, yaw control, automatic brake control, and the like.

[0088] The hydraulic control unit 73 is configured to include an electric pump for pressurizing the brake fluid, a control valve for individually adjusting the hydraulic pressure of each wheel cylinder, and the like.

[0089] Brakes FR74, FL75, RR76, and RL77 are installed on the right front wheel 51, left front wheel 52, right rear wheel 61, and left rear wheel 62, respectively. Each brake includes a disc-shaped rotor that rotates with the wheel, and a caliper that pressurizes pads to bring them into contact with the rotor. The caliper includes a wheel cylinder that presses the pads using the hydraulic pressure of brake fluid supplied from the hydraulic control unit 73.

[0090] The vehicle 1 includes an engine control unit 110 , a transmission control unit 120 , a steering control unit 130 , a brake control unit 140 , an automatic driving control unit 150 , an environment recognition unit 160 , and the like.

[0091] Each unit includes, for example, an information processing unit such as a CPU, a storage unit such as a RAM and / or a ROM, an input / output interface, and a bus connecting them.

[0092] In addition, each unit is connected so as to be communicable via an in-vehicle LAN such as a CAN communication system or directly.

[0093] The engine control unit 110 centrally controls the engine 10 and its auxiliary equipment.

[0094] The engine control unit 110 has a function of adjusting the output of the engine 10 .

[0095] The transmission control unit 120 performs speed change control in the speed change mechanism 30 , forward / reverse switching control, engagement force (limiting force) control of the lockup clutch in the torque converter 20 , and the like.

[0096] The transmission control unit 120 also has a function of controlling the driving force distribution ratio between the front wheels and the rear wheels by changing the engagement force of the transfer clutch 42 of the AWD transfer 40 .

[0097] The steering control unit 130 integrally controls a steer-by-wire steering device 200 to be described later, and controls the steering angle of the vehicle.

[0098] The functions of the steering control unit 130 will be described in detail later.

[0099] The brake control unit 140 has a function of controlling the hydraulic pressure control unit 73 to individually control the wheel cylinder hydraulic pressures (related to the braking force) of the brake FR74 , the brake FL75 , the brake RR76 , and the brake RL77 .

[0100] The brake control unit 140 has functions such as anti-lock braking control and / or behavior control. The anti-lock braking control is a control that periodically reduces the hydraulic pressure of the wheel cylinder of the wheel to restore rotation when wheel lock caused by braking occurs. The behavior control is a control that generates a braking force difference between the left and right wheels to generate a yaw moment in the direction of suppressing each behavior when oversteering behavior or understeering behavior occurs.

[0101] In order to perform these controls, the brake control unit 140 is connected to a vehicle speed sensor that detects the rotation speed of each wheel individually, a yaw rate sensor that detects the yaw rate and lateral acceleration of the vehicle body, an acceleration sensor, and the like.

[0102] The automatic driving control unit 150 performs automatic driving control by issuing instructions to the engine control unit 110 , the transmission control unit 120 , the steering control unit 130 , the brake control unit 140 , and the like so that the vehicle 1 automatically and autonomously travels.

[0103] The automatic driving control unit 150 includes a driving track setting unit 151 , a target steering angle setting unit 152 , a behavior prediction unit 153 , and the like.

[0104] The driving trajectory setting unit 151 generates an automatic driving scenario including a target driving trajectory of the host vehicle, a target vehicle speed history, and the like, based on the information provided from the environment recognition unit 160 .

[0105] During the execution of automatic driving control, the target steering angle setting unit 152 calculates the target steering angle for the vehicle to track the target driving trajectory based on the relative position of the vehicle relative to the target driving trajectory, the speed of the vehicle, the estimated friction coefficient of the road surface, etc., and instructs the steering control unit 130.

[0106] Feedback control is performed on the target steering angle in sequence according to the deviation of the vehicle from the target driving trajectory, etc.

[0107] The target steering angle setting unit 152 cooperates with the steering control unit 130 to function as a steering control unit of the present invention.

[0108] The behavior prediction unit 153 predicts the behavior that the vehicle 1 may perform during the execution of the automatic driving control.

[0109] In addition, the automatic driving control unit 150 has the function of serving as a behavior control unit, which predicts the subsequent behavior of the vehicle when the driver manually overrides the steering operation during the automatic driving control process, and changes the distribution ratio of the driving force when oversteering behavior or understeering behavior is predicted.

[0110] The environment recognition unit 160 recognizes the environment around the vehicle using various sensors and provides information on lane shape, obstacles, etc. to the automatic driving control unit 150 .

[0111] The environment recognition unit 160 is connected to various sensors such as a stereo camera, a millimeter wave radar device, a 3D laser scanning device (LIDAR), and / or a navigation device having 3D high-precision map data and a positioning device such as GPS.

[0112] The vehicle includes a steering device 200 described below in order to steer the right front wheel 51 and the left front wheel 52 serving as steerable wheels.

[0113] The steering device 200 is an electric and steer-by-wire steering device including a steering wheel 210 , a reaction force generating device 220 , a rack shaft 230 , a rack housing 240 , a tie rod 250 , a housing 260 , an actuator unit 270 , and the like.

[0114] The steering wheel 210 is an annular operating member (steering input unit) that is rotated by the driver to input a steering operation.

[0115] The steering wheel 210 is arranged facing the driver's seat in the vehicle cabin.

[0116] The steering wheel 210 is provided with a steering shaft 211 , a steering angle sensor 212 , and a torque sensor 213 .

[0117] The steering shaft 211 is a rotating shaft having one end attached to the steering wheel 210 .

[0118] The steering angle sensor 212 is provided at a middle portion of the steering shaft 211 and is a steering operation amount detection unit that detects the rotational angle position of the steering shaft 211 .

[0119] The torque sensor 213 is provided in the middle portion of the steering shaft 211 and in a region on the reaction force generating device 220 side relative to the steering angle sensor 212 , and detects torque applied to the steering shaft 211 (operating force or holding force of the steering wheel 11 by the driver).

[0120] Outputs from the steering angle sensor 212 and the torque sensor 213 are transmitted to the steering control unit 130 .

[0121] The steering control unit 130 controls the output of the motor 271 of the actuator unit 270 based on the outputs of the steering angle sensor 212 and the torque sensor 213 .

[0122] The reaction force generating device 220 includes an actuator that applies torque to the steering shaft 211 in response to a command from the steering control unit 130 and generates an approximate self-aligning torque.

[0123] The output shaft portion of the reaction force generating device 220 is connected to the end portion of the steering shaft 211 on the opposite side to the steering wheel 210 side.

[0124] The rack shaft 230 is a columnar member disposed such that its longitudinal direction (axial direction) extends along the vehicle width direction.

[0125] The rack shaft 230 is supported so as to be movable in the vehicle width direction relative to the vehicle body.

[0126] A rack gear 231 that meshes with the pinion gear of the pinion shaft 273 is formed at a portion of the rack shaft 230 .

[0127] The rack shaft 230 drives the rack gear 231 via the pinion gear in accordance with the rotation of the steering shaft 211 , and the vehicle moves (advances) in the vehicle width direction.

[0128] The rack housing 240 is a substantially cylindrical member that supports and accommodates the rack shaft 230 so as to be relatively displaceable in the vehicle width direction.

[0129] The rack housing 240 cooperates with the rack shaft 230 , the pinion shaft 273 , and the like to constitute a steering gear box.

[0130] Rack guards 241 are provided at both ends of the rack housing 240 .

[0131] The rack protection cover 241 is a component that allows the tie rod 250 to be displaced relative to the rack housing 240 and prevents foreign matter such as dust from entering the rack housing 240 .

[0132] The rack guard 241 is formed of a resin material such as elastomer into a flexible bellows shape.

[0133] The tie rod 250 is a shaft-shaped linkage member that connects the end of the rack shaft 230 to the knuckle arm 261 of the housing 260 and rotates the housing 260 about the kingpin axis in conjunction with the translational movement of the rack shaft 230 .

[0134] An inner end portion of the tie rod 250 in the vehicle width direction is swingably connected to an end portion of the rack shaft 230 via a ball joint 251 .

[0135] The outer end portion of the tie rod 250 in the vehicle width direction is connected to the knuckle arm 261 of the housing 260 via a ball joint 252 .

[0136] A turnbuckle mechanism (not shown) for toe adjustment is provided at a connection portion between the tie rod 250 and the ball joint 252 .

[0137] The housing (knuckle) 260 is a member that houses a hub bearing that supports the hubs to which the right front wheel 51 and the left front wheel 52 are mounted so as to be rotatable around the axle.

[0138] The housing 260 includes a knuckle arm 261 formed to protrude forwardly with respect to the axle.

[0139] The housing 260 is supported so as to be rotatable about a kingpin axis serving as a predetermined rotation center axis.

[0140] The kingpin axis is a virtual axis that connects the center of the bearing of the strut top bracket to the center of the ball joint connecting the lower portion of the housing 260 and the lower arm, for example, when the front suspension of the vehicle is a MacPherson strut type. This will be described in detail later.

[0141] The housing 260 is pushed and pulled in the vehicle width direction by the rack shaft 230 via the tie rod 250 , thereby rotating about the kingpin axis to steer the right front wheel 51 and the left front wheel 52 .

[0142] The actuator unit 270 is a driving device that drives the pinion shaft 273 to rotate, thereby generating a rack thrust and performing a steering operation.

[0143] The actuator unit 270 is configured to include a motor 271 , a gear box 272 , a pinion shaft 273 , and the like.

[0144] The motor 271 is an electric actuator that generates a driving force to be applied to the pinion shaft 273 .

[0145] The rotation direction and output torque of the motor 271 are controlled by the steering control unit 130 .

[0146] The output shaft angular position (rotation angle) of the motor 271 is configured to be fed back to the steering control unit 130 .

[0147] The gear box 272 includes a reduction gear train that reduces the speed of the rotation output of the motor 271 (amplifies the torque) and transmits the result to the pinion shaft 273 .

[0148] The pinion shaft 273 is a rotating shaft that is rotationally driven by the motor 271 via the gear box 272 .

[0149] A pinion gear that meshes with the rack gear 231 of the rack shaft 230 and drives the rack shaft 230 is formed at the front end portion of the pinion shaft 273 .

[0150] Hereinafter, the operation of the vehicle control device according to the first embodiment will be described.

[0151] Figure 3 This is a flowchart showing control during automatic steering in the vehicle control device according to the first embodiment.

[0152] The following describes the steps in sequence.

[0153] <Step S01: Automatic Driving Turning Determination>

[0154] The automatic driving control unit 150 determines whether the vehicle 1 is currently performing automatic driving control for autonomous steering and is turning.

[0155] Whether the vehicle is turning can be determined based on, for example, the shape of the target driving trajectory set by the driving trajectory setting unit 151 , the steering angle, yaw rate, lateral acceleration, and the like of the vehicle 1 .

[0156] When the vehicle is in a turning state based on automatic driving control (automatic steering), the process proceeds to step S02 , and in other cases, the series of processes is terminated (returned).

[0157] <Step S02: Determining whether the driver has overridden control>

[0158] The automatic driving control unit 150 communicates with the steering control unit 130 and determines whether a steering operation that overrides the driver's control (a steering operation that overlaps with the steering control by the automatic driving) is performed from the steering wheel 210 .

[0159] If an overriding steering operation has been performed, the process proceeds to step S03 , and otherwise, the series of processes ends.

[0160] <Step S03: Predicting Vehicle Behavior After Turning>

[0161] The behavior prediction unit 153 of the automatic driving control unit 150 predicts the vehicle behavior when the front wheels are turned in accordance with the over-control steering operation detected in step S02, when the driving force distribution is normal (hereinafter, normal means when the over-steering suppression control or under-steering suppression control is not intervened (a situation where an over-steering behavior or under-steering behavior of a predetermined magnitude or greater is not predicted).).

[0162] The prediction of vehicle behavior can be performed by, for example, inputting various parameters such as the current vehicle speed, steering angle, yaw rate, lateral acceleration, and estimated friction coefficient of the road surface into a numerical analysis model of the vehicle prepared in advance.

[0163] Afterwards, proceed to step S05.

[0164] <Step S04: Oversteering Determination>

[0165] When the absolute value of the yaw rate (predicted yaw rate) in the vehicle behavior predicted in step S03 by the automatic driving control unit 150 is above the predetermined oversteering suppression control intervention threshold, it is determined that there is a high possibility that oversteering behavior of a predetermined magnitude or above will occur on the vehicle 1 due to the over-controlled steering operation, and the process proceeds to step S05; in other cases, the process proceeds to step S08.

[0166] <Step S05: Oversteering Suppression Control>

[0167] The automatic driving control unit 150 issues a command to the transmission control unit 120 to perform oversteering suppression control for increasing the engagement force of the transfer clutch 42 of the AWD transfer 40 relative to the normal state.

[0168] As a result, the driving force distribution between the front and rear wheels becomes more biased towards the front wheels than usual (in the case of this embodiment, the front and rear driving force distribution tends to be close to 50:50), the understeering tendency of the vehicle 1 is enhanced, and the vehicle 1 is prevented from actually oversteering.

[0169] Afterwards, proceed to step S06.

[0170] <Step S06: Oversteering Suppression Control Ending Judgment>

[0171] When the most recently detected yaw angular velocity is below the predetermined oversteering suppression control end threshold, the automatic driving control unit 150 sets the possibility of oversteering behavior of a predetermined magnitude or greater occurring to be low even if the oversteering suppression control is ended, and enters step S07. In other cases, it returns to step S05 and repeats subsequent processing.

[0172] Note that, in order to impart hysteresis characteristics and prevent control hunting, the oversteering suppression control end threshold value may be set smaller than the oversteering suppression control intervention threshold value.

[0173] <Step S07: Normal Control Resumption>

[0174] The automatic driving control unit 150 issues a command to the transmission control unit 120 to reduce the engagement force of the transfer clutch 42 to the normal engagement force.

[0175] After that, a series of processing ends.

[0176] <Step S08: Understeer Determination>

[0177] When the absolute value of the predicted yaw angular velocity is below the predetermined understeer suppression control intervention threshold, the automatic driving control unit 150 determines that there is a high possibility that the vehicle 1 will experience understeer behavior of a magnitude greater than a predetermined magnitude due to the over-controlled steering operation, and enters step S09. In other cases, the series of processing is terminated.

[0178] <Step S09: Understeer Suppression Control>

[0179] The automatic driving control unit 150 issues a command to the transmission control unit 120 to perform understeer suppression control for reducing the engagement force of the transfer clutch 42 of the AWD transfer 40 relative to a normal state.

[0180] As a result, the driving force distribution between the front and rear wheels becomes more biased towards the rear wheels than usual (in the case of this embodiment, the front and rear driving force distribution tends to be close to 35:65), suppressing the understeering tendency of the vehicle 1 and suppressing the vehicle 1 from actually understeering.

[0181] Afterwards, proceed to step S10.

[0182] <Step S10: Understeer Suppression Control Ending Determination>

[0183] When the most recently detected yaw angular velocity is below the predetermined understeer suppression control termination threshold, the automatic driving control unit 150 sets the possibility of understeer behavior exceeding a predetermined magnitude occurring even if the understeer suppression control is terminated to be low, and enters step S11. In other cases, it returns to step S09 and repeats subsequent processing.

[0184] Note that, in order to impart hysteresis characteristics and prevent control hunting, the understeering suppression control end threshold value may be set larger than the understeering suppression control intervention threshold value.

[0185] <Step S11: Normal Control Resumption>

[0186] The automatic driving control unit 150 issues a command to the transmission control unit 120 to increase the engagement force of the transfer clutch 42 to the normal engagement force.

[0187] After that, a series of processing ends.

[0188] Figure 4 This is a diagram showing an example of changes in the steering angle, yaw rate, and front-rear drive force distribution ratio of a vehicle equipped with the vehicle control device according to the first embodiment.

[0189] exist Figure 4 In the figure, the horizontal axis represents time, and the vertical axis represents the steering angle (larger on the upper side), the driving force distribution (the upper side is biased towards the front wheel), and the yaw rate (larger on the upper side).

[0190] exist Figure 4 In the example shown, the steering angle is initially increased at a predetermined steering speed by the automatic driving and is then maintained at the predetermined steering angle.

[0191] This steering imparts a slip angle to the front wheels, generating a turning force, and the vehicle 1 starts turning, generating a yaw angular velocity.

[0192] Figure 4 This indicates a state where the driver subsequently performs an overriding steering operation in the direction of increasing the steering angle (increasing the rotation). As a result, the predicted yaw rate increases and eventually diverges, indicating a high possibility that the vehicle 1 falls into the rotation mode.

[0193] Therefore, in Figure 4 In the illustrated case, the oversteer suppression control intervenes to shift the front-rear driving force distribution toward the front wheels compared to normal, thereby increasing the understeer tendency of the vehicle 1 and converging the actual yaw rate to stabilize the vehicle behavior.

[0194] Figure 5 1 is a diagram schematically showing a state of a vehicle equipped with the vehicle control device according to the first embodiment after an override steering operation is performed.

[0195] exist Figure 5 In the middle, it shows the state when the vehicle enters a left corner (curved road) through automatic driving (automatic steering) and then the driver performs an overriding steering operation.

[0196] The length of the arrows marked in front of each wheel indicates the magnitude of the driving force. Figures 6 to 8 (same as in [ ].

[0197] When the vehicle 1 is traveling at the position P1 by automatic steering (for example, in a steady circular turn), if the steering angle increases due to a driver's operation, the yaw rate may increase rapidly due to the generation of an excessive yaw moment.

[0198] If such an increase in yaw rate is ignored, the vehicle may oversteer, and in extreme cases, may fall into a rotation mode as in the state at position P2.

[0199] Therefore, when the predicted yaw rate immediately after the override becomes equal to or greater than the oversteer suppression control intervention threshold, the driving force distribution is changed to be more weighted toward the front wheels than usual, thereby suppressing the oversteer tendency of the vehicle 1 .

[0200] In the state shown at position P3 , the driving force distribution is changed to be more weighted toward the front wheels compared to the normal state (the state of driving force indicated by the length of the arrow at position P1 ).

[0201] By changing the driving force distribution in this way, the basic characteristics of the vehicle 1 tend to understeer, the generation of yaw rate is suppressed, and the behavior of the vehicle 1 is stabilized to prevent the vehicle 1 from shifting to the turning mode.

[0202] Figure 6 1 is a diagram schematically showing another state of the vehicle including the vehicle control device according to the first embodiment after the overriding steering operation is performed.

[0203] If the driver increases the steering angle while the front wheel force is insufficient to meet the friction circle limit, the front wheel may drift outward even if the steering angle is increased. Furthermore, due to the excessive slip angle, the tire cornering force decreases, resulting in a decrease in yaw moment and understeer. (Position P2)

[0204] Therefore, when the predicted yaw rate immediately after the override becomes equal to or less than the understeer suppression control intervention threshold, the driving force distribution is changed to be more weighted toward the rear wheels than usual, thereby suppressing the understeer tendency of the vehicle 1 .

[0205] In the state shown at position P3 , the driving force distribution is changed to be more weighted toward the rear wheels compared to the normal state (the state shown at position P1 ).

[0206] By changing the driving force distribution in this way, the basic characteristics of the vehicle 1 tend to oversteer and the generation of yaw rate is promoted, thereby stabilizing the behavior of the vehicle 1 and improving the course following performance.

[0207] As described above, according to the first embodiment, the following effects can be obtained.

[0208] (1) In a case where the driver overrides the input of a steering operation during the automatic steering control process and the occurrence of oversteering behavior exceeding a predetermined magnitude caused by the operation is predicted, the distribution ratio of the driving force between the front wheels and the rear wheels is changed to be biased towards the front wheels relative to the case where the occurrence of oversteering behavior exceeding a predetermined magnitude is not predicted, thereby enhancing the understeering tendency caused by the driving force and preventing the occurrence of oversteering behavior that would make the vehicle 1 unstable.

[0209] Furthermore, since the front wheels are steered in accordance with the driver's steering operation at this time, the driver does not feel a sense of discomfort due to steering not being performed in accordance with the steering operation.

[0210] (2) In the case where the driver overrides the input of a steering operation during the automatic steering control process and the occurrence of understeering behavior exceeding a predetermined magnitude caused by the operation is predicted, the distribution ratio of the driving force between the front wheels and the rear wheels is changed to be biased towards the rear wheels relative to the case where the occurrence of understeering behavior exceeding a predetermined magnitude is not predicted, thereby enhancing the oversteering tendency caused by the driving force and preventing the occurrence of understeering behavior that makes the vehicle 1 unstable.

[0211] Furthermore, since the front wheels are steered in accordance with the driver's steering operation at this time, the driver does not feel a sense of discomfort due to steering not being performed in accordance with the steering operation.

[0212] <Second embodiment>

[0213] Next, a second embodiment of a vehicle control device to which the present invention is applied will be described.

[0214] In each embodiment described below, the same reference numerals are given to the same parts as those in the previous embodiment, and the description thereof is omitted, and the description will be mainly focused on the differences.

[0215] In the vehicle control device of the second embodiment, in the above-mentioned oversteer suppression control (step S05) and understeer suppression control (step S09), in addition to the change in the front and rear driving force distribution similar to the first embodiment, the driving force distribution on the turning inner wheel side and the turning outer wheel side is also changed.

[0216] Figure 7 1 is a diagram schematically showing a state of a vehicle equipped with the vehicle control device according to the second embodiment after an override steering operation is performed.

[0217] exist Figure 7In the state shown in position P3, based on the prediction of oversteering behavior, in addition to changing the front and rear driving force distribution to be biased towards the front wheel side as in the first embodiment, the driving force of the left front wheel 52, which is the inner wheel side of the turn, is relatively increased compared to the right front wheel 51, and the driving force of the left rear wheel 62 is relatively increased compared to the right rear wheel 61, so that the left and right driving force distribution is biased towards the inner wheel side of the turn.

[0218] Such a change in the left and right driving force distribution can be performed, for example, by using the hydraulic control unit 73 to generate braking force on the brake FR74 and the brake RR76 on the turning outer wheel side while driving force is applied to each wheel (accelerator is on).

[0219] For example, in a vehicle that does not normally perform torque vectoring control on the left and right front wheels or the left and right rear wheels (a vehicle in which the driving force is evenly distributed on the left and right sides), braking force is applied to the front and rear wheels on the turning outer wheel side, and control is performed so that the driving force on the turning inner wheel side is greater than the driving force on the turning outer wheel side.

[0220] In the case of a vehicle that normally performs torque vector control to apply a driving force difference to the left and right front wheels and the left and right rear wheels, the normal torque vector control is controlled so that the driving force on the turning inner wheel becomes relatively larger than the driving force on the turning outer wheel.

[0221] For example, the driving force of each wheel can be set in the order of the front inner wheel (left front wheel 52), the front outer wheel (right front wheel 51), the rear inner wheel (left rear wheel 62), and the rear outer wheel (right rear wheel 61) (from large to small).

[0222] Figure 8 1 is a diagram schematically showing another state of the vehicle including the vehicle control device according to the second embodiment after the overriding steering operation is performed.

[0223] exist Figure 8 In the state shown in position P3, based on the prediction of understeer behavior, in addition to changing the front and rear driving force distribution to be biased towards the rear wheel side as in the first embodiment, the driving force of the right front wheel 51, which is the turning outer wheel side, is relatively increased compared to the left front wheel 52, and the driving force of the right rear wheel 61 is relatively increased compared to the left rear wheel 62, so that the left and right driving force distribution is biased towards the turning outer wheel side.

[0224] Such a change in the left and right driving force distribution can be performed, for example, by using the hydraulic control unit 73 to generate braking force on the brake FL75 and the brake RL77 on the inner turning wheel side while driving force is applied to each wheel (accelerator is on).

[0225] For example, in a vehicle that does not normally perform torque vectoring control on the left and right front wheels or the left and right rear wheels (a vehicle in which the driving force is evenly distributed on the left and right sides), braking force is applied to the front and rear wheels on the inner turning wheel side, and control is performed so that the driving force on the outer turning wheel side is greater than the driving force on the inner turning wheel side.

[0226] In the case of a vehicle that normally performs torque vector control to apply a driving force difference to the left and right front wheels and the left and right rear wheels, the normal torque vector control is controlled so that the driving force on the turning outer wheel becomes relatively larger than the driving force on the turning inner wheel.

[0227] For example, the driving force of each wheel can be set in the order of rear outer wheel (right rear wheel 61), rear inner wheel (left rear wheel 62), front outer wheel (right front wheel 51), and front inner wheel (left front wheel 52) (from large to small).

[0228] According to the second embodiment described above, in addition to the same effects as those of the first embodiment described above, the following effects can be obtained.

[0229] (1) When the driver overrides the steering input during the automatic steering control process and the occurrence of oversteering behavior is predicted, the distribution ratio of the driving force between the inner turning wheel and the outer turning wheel is changed to be biased towards the inner turning wheel compared to the normal state, thereby generating a yaw moment in a direction that suppresses the oversteering tendency, thereby further preventing the occurrence of oversteering behavior and the destabilization of the vehicle.

[0230] (2) When the driver overrides the input of a steering operation during the automatic steering control process and the occurrence of understeering behavior caused by this is predicted, the distribution ratio of the driving force between the inner steering wheel and the outer steering wheel is changed to be biased towards the outer steering wheel relative to the normal state, thereby generating a yaw moment in a direction that suppresses the understeering tendency, thereby further preventing the occurrence of understeering behavior and making the vehicle unstable.

[0231] (Variation)

[0232] The present invention is not limited to the above-described embodiments, and various modifications and changes are possible, and these modifications and changes are also within the technical scope of the present invention.

[0233] (1) The configurations of the vehicle and the vehicle control device are not limited to the above-described embodiments, and can be modified as appropriate.

[0234] For example, in each embodiment, the front and rear driving force of the vehicle is distributed by a center differential including a front and rear unequal torque distribution mechanism having planetary gears and a transfer clutch provided in the center differential, but other methods may also be used.

[0235] For example, one of the front wheel side and rear wheel side drive mechanisms may be directly connected to the output of the transmission mechanism, and a clutch mechanism with variable engagement force may be provided between the transmission mechanism and the other of the front wheel side and rear wheel side drive mechanisms.

[0236] Alternatively, the front and rear wheels may be driven by independent power sources. For example, one of the front and rear wheels may be driven by the engine, while the other may be driven by an electric motor. Alternatively, the front and rear wheels may be driven by independent electric motors, or each wheel may be driven independently by an independent electric motor.

[0237] (2) In the second embodiment, a driving force difference is generated by applying a braking force to one of the turning inner wheel and the outer wheel. However, the method of generating a driving force difference between the turning inner wheel and the outer wheel is not limited to this.

[0238] For example, the vehicle may be configured to include a speed-increasing mechanism for increasing the speed of one of the left and right wheels relative to the other.

[0239] Alternatively, the vehicle may be configured so that the left and right wheels are driven by independent electric motors.

[0240] In the second embodiment, a driving force difference between the inner and outer wheels during turning is generated in both the front and rear wheels. However, a driving force difference may be generated in only one of the front and rear wheels.

[0241] Furthermore, in the second embodiment, while the driving force distribution between the front and rear wheels is changed, a driving force difference is generated between the inner and outer wheels during a turn. However, it is also possible to change only the driving force distribution between the inner and outer wheels during a turn without changing the driving force distribution between the front and rear wheels. In this case, the vehicle's drive system is not limited to AWD (all-wheel drive) and can also be front-wheel drive (FWD) or rear-wheel drive (RWD).

[0242] (3) In each embodiment, the state of automatic driving control in which the vehicle automatically and autonomously travels is described as an example, but the present invention is not limited to this. For example, it can also be applied to driving assistance controls such as lane keeping assist control and lane departure prevention control.

[0243] (4) In each embodiment, the steering device is, for example, a so-called steer-by-wire structure in which the steering wheel and the steering mechanism are not mechanically connected, but the present invention is not limited to this and can also be applied to an electric power steering device in which the steering wheel and the steering mechanism are mechanically connected and an electric motor for generating an auxiliary force (steering force) is added.

[0244] (5) It may also be configured so that, when a steering operation is inputted in an overriding manner during automatic steering such as autonomous driving control and it is predicted that the behavior of the vehicle becomes unstable, in addition to the above-mentioned change in the driving force distribution, the actual steering amount (steering amount) relative to the steering operation amount is suppressed (equivalent to increasing (slowing down) the steering gear ratio).

Claims

1. A vehicle control device, characterized in that: have: A steering device that steers the vehicle's front wheels via an actuator; a steering control unit, which controls the steering device according to a target driving trajectory of the vehicle to automatically steer the vehicle; A steering input unit, for inputting steering operation by a driver; a front-rear driving force distribution unit capable of changing the distribution ratio of the driving force transmitted from the front wheels and the rear wheels to the road surface; a left and right driving force distribution unit capable of changing the distribution ratio of the driving force transmitted from the left and right front wheels or the left and right rear wheels to the road surface; and a behavior control unit that, when steering is automatically performed by the steering control unit, performs a first driving force distribution ratio control in the absence of a steering operation by the driver using the steering input unit, and performs a second driving force distribution ratio control in the absence of a steering operation by the driver using the steering input unit, In the first driving force distribution ratio control, the driving force distribution ratio of the wheels is corrected according to the acceleration state, climbing state, and turning state of the vehicle. In the second driving force distribution ratio control, the behavior of the vehicle after turning corresponding to the driver's steering operation is predicted. When the absolute value of the predicted yaw angular velocity is above a predetermined oversteering suppression control intervention threshold, it is predicted that oversteering behavior of a predetermined magnitude or above will occur, and the driving forces of the front inner wheel, the front outer wheel, the rear inner wheel, and the rear outer wheel are set in descending order.

2. A vehicle control device, characterized in that: have: A steering device that steers the vehicle's front wheels via an actuator; a steering control unit, which controls the steering device according to a target driving trajectory of the vehicle to automatically steer the vehicle; A steering input unit, for inputting steering operation by a driver; a front-rear driving force distribution unit capable of changing the distribution ratio of the driving force transmitted from the front wheels and the rear wheels to the road surface; a left and right driving force distribution unit capable of changing the distribution ratio of the driving force transmitted from the left and right front wheels or the left and right rear wheels to the road surface; and a behavior control unit that, when steering is automatically performed by the steering control unit, performs a first driving force distribution ratio control in the absence of a steering operation by the driver using the steering input unit, and performs a third driving force distribution ratio control in the absence of a steering operation by the driver using the steering input unit, In the first driving force distribution ratio control, the driving force distribution ratio of the wheels is corrected according to the acceleration state, climbing state, and turning state of the vehicle. In the third driving force distribution ratio control, the behavior of the vehicle after turning corresponding to the driver's steering operation is predicted. When the absolute value of the predicted yaw angular velocity is below a predetermined understeer suppression control intervention threshold, it is predicted that understeer behavior of a predetermined magnitude or greater will occur, and the driving forces of the rear outer wheel, the rear inner wheel, the front outer wheel, and the front inner wheel are set in descending order.

Images