Vehicle control device

Abstract

Driving control device (70) for a vehicle, which is to be applied to a vehicle with a front wheel steering angle adjustment device (10) configured to control a cornering condition variable, which is a condition variable relating to cornering of the vehicle, by adjusting a steering angle of a front wheel, a cornering control device provided and configured separately from the front wheel steering angle adjustment device (10) to control the cornering condition variable, and a steering device (20) comprising a steering wheel to which a steering torque is applied and which is connected to the front wheel, wherein the driving control device for a vehicle comprises: a cornering control unit (72) configured to perform cornering assistance control which causes the cornering condition variable to follow a target cornering condition variable, which is a target value of the cornering condition variable,by causing the front wheel steering angle adjustment device (10) and / or the cornering control device to operate; and a steering instruction unit (73) configured to obtain a holding torque, which is a torque that holds a steering wheel angle at a neutral point, when no steering is performed during the execution of the steering assistance control, and to instruct the steering device (20) to apply the holding torque to the steering wheel, wherein the cornering control unit (72) is configured to cause the cornering control device to operate, and to cause the front wheel steering angle adjustment device not to operate during cornering assistance control when steering is not performed, and to cause the front wheel steering angle adjustment device (10) to operate during cornering assistance control when steering is performed.

Description

Technical field The present invention relates to a driving control device for a vehicle. State of the art JP 2012-006506A describes an example of a vehicle control device that performs a cornering assistance control to support cornering of a vehicle traveling in a lane. According to this vehicle control device, when the vehicle is cornering in a situation where the driver is not steering, cornering is performed by automatically adjusting the steering angle of the front wheels connected to a steering device. Furthermore, DE 11 2010 006 048 T5 discloses a vehicle motion control device, wherein a behavior control device controls a front wheel steering angle change device or a rear wheel steering angle change device that is not in a functional restriction state, such that a selected quantity has a selected setpoint, and the functional restriction state includes a fault state.Furthermore, DE 11 2016 004 578 T5 discloses a device for controlling vehicle behavior, wherein a drive force control element is designed to control the vehicle in such a way that a reduction in the drive force for the vehicle gradually increases with an increase in the yaw rate and in such a way that the reduction in the drive force is stopped, provided that a yaw rate-related quantity is greater than a predetermined threshold value and the steering angle of the vehicle increases and the yaw rate-related quantity increases, and provided that the yaw rate-related quantity is less than or equal to the threshold value. Summary of the invention Technical problem When the vehicle is automatically steered by the cornering assist control system, or is undergoing a turn, it is possible to maintain the steering angle of the steering wheel at a neutral point. The neutral point is a steering angle at which the steered angle of the front wheels is "0 (zero)." When the steering angle is held at the neutral point, a holding torque, which is the torque required to maintain the steering angle at the neutral point, is applied to the steering mechanism. The magnitude of the holding torque varies depending on the vehicle's slip angle and the steering angle of the front wheels. Therefore, it is necessary to update the holding torque sequentially according to changes in the body's slip angle and the steering angle of the front wheels. In this case, a first torque, corresponding to the body's slip angle, and a second torque, corresponding to the steering angle of the front wheels, are derived or obtained individually from the holding torque. Obtaining the first and second torques in this way increases the computational effort of the vehicle control unit. Solution to the problem A vehicle control device for solving the above problems is applied to a vehicle comprising a front wheel steering angle adjustment device configured to control a cornering condition variable, which is a condition variable relating to the cornering of the vehicle, by adjusting a steering angle of a front wheel, a cornering control device provided separately from the front wheel steering angle adjustment device and configured to control the cornering condition variable, and a steering device comprising a steering wheel into which a steering torque is input and which is connected to the front wheel.The driving control device comprises: a cornering control unit configured to perform cornering assistance control, which causes the cornering state variable to follow a target cornering state variable, which is a target value of the cornering state variable, by causing the front wheel steering angle adjustment device and / or the cornering control device to operate; and a steering instruction unit configured to obtain a holding torque, which is a torque that holds a steering wheel angle at a neutral point, if no steering is performed during the execution of the cornering assistance control, and to instruct the steering device to apply the holding torque to the steering wheel.Furthermore, the cornering control unit causes the cornering control device to operate and causes the front wheel steering angle adjustment device not to operate in cornering support control when steering is not performed, and causes the front wheel steering angle adjustment device to operate in cornering support control when steering is performed. According to the configuration described above, the front wheel steering angle adjustment device is not operated when steering is not performed during the execution of the power steering control, and therefore the front wheel steering angle is held at "0 (zero)." Consequently, when obtaining the holding torque, it is necessary to obtain a torque component corresponding to the body slip angle, and not a torque component corresponding to the front wheel steering angle. Since it is not necessary to obtain the torque component corresponding to the front wheel steering angle, the steering wheel angle can be held at the neutral point, while reducing the increase in the computational load on the vehicle control device. Brief description of the drawings Fig. 1 is a diagram showing a functional configuration of a vehicle control device according to an exemplary embodiment and a schematic configuration of a vehicle with the vehicle control device. Fig. 2 is a flowchart illustrating a processing routine that is executed when it is determined whether steering is performed. Fig. 3 is a flowchart illustrating a processing routine that is executed when cornering assistance control is activated. Fig. 4 is a flowchart illustrating a processing routine that is executed when a steering device is controlled. Description of exemplary implementations The following describes an embodiment of a vehicle control device with reference to Fig. 1, Fig. 2, Fig. 3 to Fig. 4. Fig. 1 schematically shows a vehicle with a driving control device 70 according to the present embodiment. The vehicle comprises a front wheel steering angle adjustment device 10, which sets a steering angle θF of a plurality of front wheels FL and FR, a steering device 20, which is connected to each of the front wheels FL and FR, and a rear wheel steering angle adjustment device 30, which sets a steering angle θR of a plurality of rear wheels RL and RR. The steered angle θF of the front wheels FL and FR is referred to as the "front wheel steering angle θF", and the steered angle θR of the rear wheels RL and RR is referred to as the "rear wheel steering angle θR". The vehicle further comprises a braking device 40, which sets a braking force of the vehicle, and a drive device 50, which sets a driving force of the vehicle. The front steering angle adjustment device 10 comprises an actuator for the front steering 11 and a control unit for the front steering 16, which controls the front steering actuator 11. The front steering actuator 11 is connected to each of the front wheels FL and FR via a tie rod 13. The front steering actuator 11 is equipped with a front wheel motor 12 as a power source, and the front wheel motor 12 is controlled by the control unit for the front steering 16. Furthermore, the front steering angle adjustment device 10 sets the front steering angle θF by transmitting a drive torque from the front wheel motor 12 to each of the front wheels FL and FR via the tie rod 13. The steering device 20 comprises a steering wheel 21, a steering actuator 22, and a steering control unit 26, which controls the steering actuator 22. Since the steering wheel 21 is operated by a driver, a steering torque TQIn caused by steering is input into the steering wheel 21. The steering actuator 22 is connected to the steering wheel 21 via a steering shaft 23 and to the front wheel steering actuator 11 via an intermediate shaft 24. That is, the steering actuator 22 is connected to each of the front wheels FL and FR via the intermediate shaft 24, the front wheel steering actuator 11, and the tie rod 13. When the front wheels FL and FR are steered, the steering torque TQIn applied by the driver to the steering wheel 21 is transmitted via the steering actuator 22 to the front wheel steering actuator 11. Accordingly, the front wheel steering angle θF is changed in accordance with a change in the steering angle of the steering wheel 21. That is, when steering is performed, there is a correlation between an actual steering angle Str and the front wheel steering angle θF. The steering angle Str correlated with the front wheel steering angle θF is called the "reference steering angle StrB". When the front wheels FL and FR are steered, the actual steering angle Str at that point is essentially the same as the reference steering angle StrB. The reference steering angle StrB at which the front wheel steering angle θF is "0 (zero)" is called the "neutral point StrC". The steering actuator 22 comprises an actuation angle control mechanism 221, which sets a difference between the actual steering angle Str and the reference steering angle StrB, and a steering motor 222, which is a power source for the actuation angle control mechanism 221. The difference between the steering angle Str and the reference steering angle StrB can be generated by controlling the operation of the actuation angle control mechanism 221 by the steering control unit 26. When the front wheels FL and FR are steered by the steering system, the actuation angle control mechanism 221 is operated so that the difference is "0 (zero)." Accordingly, the actual steering angle Str is essentially the same as the reference steering angle StrB at that time. Furthermore, the steering device 20 is equipped with a steering angle sensor 101, which detects the steering angle Str, and a torque sensor 102, which detects the steering torque TQIn introduced into the steering wheel 21 by the steering mechanism. The steering angle sensor 101 outputs a signal corresponding to the steering angle Str as a detection signal to the steering control unit 26 and the vehicle control device 70. The torque sensor 102 outputs a signal corresponding to the steering torque TQIn as a detection signal to the steering control unit 26 and the vehicle control device 70. The rear steering angle adjustment device 30 comprises an actuator 31 and a rear steering control unit 36, which controls the rear steering actuator 31. The rear steering actuator 31 is connected to each of the rear wheels RL and RR via a tie rod 33. The rear steering actuator 31 is equipped with a rear wheel motor 32 as a power source, and the rear wheel motor 32 is controlled by the rear steering control unit 36. Furthermore, the rear steering angle adjustment device 30 sets the rear steering angle θR by transmitting a drive torque from the rear wheel motor 32 to each of the rear wheels RL and RR via the tie rod 33. When the rear steering angle θR is changed in this way while the vehicle is in motion, the magnitude of the vehicle's yaw moment changes.When the magnitude of the yaw moment changes, a cornering state variable such as the yaw rate Yr and the lateral acceleration Gy of the vehicle changes. The cornering state variable is a state variable that relates to the vehicle's cornering behavior. Therefore, in the present embodiment, the rear wheel steering angle adjustment device 30 is an example of a "cornering control device". The braking device 40 comprises a brake actuator 41 and a brake control unit 46, which controls the brake actuator 41. The brake actuator 41 can individually adjust the braking force for each of the wheels FL, FR, RL, and RR. When the vehicle is moving, the yaw moment in the vehicle can be generated by creating a braking force differential between the right front wheel FR and the left front wheel FL; that is, the magnitude of the cornering condition can be varied. Therefore, in the present embodiment, the braking device 40 is also an example of a "cornering control device". The drive device 50 comprises a power unit 51 and a drive control unit 56, which controls the power unit 51. The power unit 51 is equipped with a power source from the vehicle, such as an internal combustion engine or an electric motor. Since the rear wheels RL and RR are drive wheels, in the example shown in Fig. 1, a drive torque output by the drive device 50 is transmitted to each of the rear wheels RL and RR. The driving control device 70 supports automatic driving of the vehicle along a defined route TR by controlling various on-board devices. In the present embodiment, for example, information about the route TR, which is intended to cause the vehicle to travel in the lane, is input into the driving control device 70 from another device. The driving control device 70 comprises, as functional units to support the steering or cornering of the vehicle, a steering determination unit 71, a cornering control unit 72, a steering instruction unit 73, a setpoint specification unit 74, a setpoint specification unit 75 and a setpoint acquisition unit 76 for the cornering driving condition. The steering control unit 71 determines whether the driver is steering. For example, the steering control unit 71 determines whether steering is taking place based on the steering torque TQIn, which is obtained from the detection signal of the torque sensor 102. The processing of the steering control determination is described later. The cornering control unit 72 performs the cornering assistance control, which causes a cornering state variable TSQ to follow a target cornering state variable TSQTr, which is a target value of the cornering state variable TSQ, by operating the front wheel steering angle adjustment device 10, the rear wheel steering angle adjustment device 30, and / or the braking device 40. The cornering state variable TSQ is a state variable capable of generating a greater yaw moment when its value is greater than a certain value. Examples of the cornering state variable TSQ are the vehicle's yaw rate Yr, obtained from a detection signal by a yaw rate sensor 103, and the vehicle's lateral acceleration Gy, obtained from a detection signal by a lateral acceleration sensor 104. When the steering determination unit 71 determines that steering is being performed, the cornering control unit 72 executes the steering-is-being-performed cornering assistance control as cornering assistance control when steering is performed. Conversely, when the steering determination unit 71 determines that steering is not being performed, the cornering control unit 72 executes the steering-is-not-being-performed cornering assistance control as cornering assistance control when steering is not performed. In the steering-is-being-performed cornering assistance control, the cornering control unit 72 causes the front wheel steering angle adjustment device 10 to operate and at least one of the rear wheel steering angle adjustment device 30 and the brake device 40 to operate.On the other hand, in the case of steering-is-not-executed cornering support control, the cornering control unit 72 causes at least one of the rear wheel steering angle adjustment devices 30 and the brake device 40 to be operated, but the front wheel steering angle adjustment device 10 to not be operated. When the steering-is-executed cornering assist control is executed, the front-wheel steering control unit 16 controls the front-wheel steering actuator 11 to change the front-wheel steering angle θF. Conversely, when the steering-is-not-executed cornering assist control is executed, the front-wheel steering control unit 16 controls the front-wheel steering actuator 11 so that the front-wheel steering angle θF is "0 (zero)". This occurs because no driving instruction is input to the front-wheel steering angle adjustment device 10. This means that the front-wheel steering angle adjustment device 10 is not operated during the execution of the steering-is-executed cornering assist control, which means that the front-wheel steering angle θF is maintained at "0 (zero)". When the cornering control unit 72 is instructed to actuate the rear steering angle adjustment device 30 in a situation where cornering assistance control is active, the rear steering control unit 36 ​​controls the rear steering actuator 31 to change the rear steering angle θR. Conversely, when the cornering control unit 72 is instructed not to actuate the rear steering angle adjustment device 30 in a situation where cornering assistance control is active, the rear steering control unit 36 ​​controls the rear steering actuator 31 so that the rear steering angle θR is maintained at "0". That is to say, acting on the rear steering angle adjustment device 30 during cornering assistance control means cornering the vehicle by adjusting the rear steering angle θR.On the other hand, not activating the rear wheel steering angle adjustment device 30 in the cornering assistance control means that the rear wheel steering angle θR is kept at “0 (zero)”. When the cornering control unit 72 is instructed to actuate the brake device 40 in the situation where cornering assistance control is executed, the brake control unit 46 controls the brake actuator 41 so that the braking force differential between the right front wheel FR and the left front wheel FL is generated. Conversely, the brake control unit 46 does not generate a braking force differential between the right front wheel FR and the left front wheel FL if the cornering control unit 72 is instructed not to actuate the brake device 40 in the situation where cornering assistance control is executed. That is, actuating the brake device 40 during cornering assistance control means that the vehicle is turned by adjusting the braking force differential between the right wheel and the left wheel.If the braking device 40 is not operated during cornering assistance control, the braking force difference is kept at “0 (zero)”. When the braking force is applied to the right front wheel FR and / or the left front wheel FL by the drive of the brake device 40, the vehicle may decelerate. Therefore, when the brake device 40 is operated by executing the cornering assist control, the cornering control unit 72 can instruct the drive control unit 56 to increase the vehicle's drive force to counteract the deceleration caused by the application of the braking force to the right front wheel FR and / or the left front wheel FL. In this case, upon receiving the instruction, the drive control unit 56 controls the drive unit 51 to increase the vehicle's drive force by an amount corresponding to the instruction. The steering instruction unit 73 controls the steering device 20 when the steering assistance control is executed by the cornering control unit 72. That is, when the steering-not-executed cornering assistance control is executed, the steering instruction unit 73 instructs the steering device 20 to maintain the steering angle at the neutral point StrC. Conversely, the steering instruction unit 73 instructs the steering device 20 to assist the driver's steering when the steering-is-executed cornering assistance control is executed. The processing content of the steering instruction unit 73 when the steering-not-executed cornering assistance control is executed, and the processing content of the steering instruction unit 73 when the steering-is-executed cornering assistance control is executed, are described later. The required cornering condition setting unit 74 detects a steering-related value and sets a corresponding value as the required cornering condition. Examples of steering-related values ​​are the steering angle Str and the steering torque TQIn. For example, if the steering angle Str is set as the steering-related value, the required cornering condition setting unit 74 sets a required cornering condition TSQR such that the value of the required cornering condition TSQR increases with increasing steering angle Str. If the steering determination unit 71 detects that no steering is taking place, the required cornering condition setting unit 74 sets the required cornering condition TSQR to "0 (zero)."If the cornering condition parameter TSQ is the yaw rate Yr of the vehicle, the yaw rate Yr corresponding to the steering-related value is set as the required cornering condition parameter TSQR. The setting unit for Target Automatic Cornering Condition Size 75 sets a Target Automatic Cornering Condition Size TSQATr, which is a target value for the cornering condition for cornering the vehicle along the specified route TR. For example, the setting unit for Target Automatic Cornering Condition Size 75 sets the Target Automatic Cornering Condition Size TSQATr such that a value of the Target Automatic Cornering Condition Size TSQATr increases when the curve radius of the route TR decreases. If the cornering condition size TSQ is the yaw rate Yr of the vehicle, the yaw rate Yr corresponding to the curve radius of the route TR and a vehicle ramp-up speed is set as the Target Automatic Cornering Condition Size TSQATr.The acquisition unit 76 derives the target cornering state variable TSQTr; that is, if the steering determination unit 71 determines that steering is not being performed, the acquisition unit 76 sets the target automatic cornering state variable TSQATr as the target cornering state variable TSQTr. Conversely, if the steering determination unit 71 determines that steering is being performed, the acquisition unit of target cornering state variable 76 derives the target cornering state variable TSQTr based on a parameter that has a larger absolute value than both the required cornering state variable TSQR and the target automatic cornering state variable TSQATr. In particular, the acquisition unit of target curve driving state variable 76 derives the target curve driving state variable TSQTr such that a value of the target curve driving state variable TSQTr increases when the parameter increases.For example, the acquisition unit of target curve driving state variable 76 sets the parameter with the larger absolute value of the required curve driving state variable TSQR and the target automatic curve driving state variable TSQATr than the target curve driving state variable TSQTr. Furthermore, the acquisition unit of target cornering state variable 76 also derives a target angle βTr, which is a target of the vehicle body's slip angle. For example, the acquisition unit of target cornering state variable 76 derives the target rotation angle βTr for the cornering state based on the acquired target cornering state variable TSQTr. Next, a processing routine is described that is executed by the steering control unit 71 to determine whether steering is being performed (see Fig. 2). This processing routine is executed repeatedly for each predetermined steering cycle when the power steering control is performed. In the present processing routine, step S11 determines whether an absolute value of the steering torque TQIn is equal to or greater than a target steering torque TQInTh. The target steering torque TQInTh is a criterion for determining whether the driver intends to turn the steering wheel 21. If the absolute value of the steering torque |TQIn| is equal to or greater than that of the target steering torque TQInTh, steering occurs. If the absolute value of the steering torque |TQIn| is equal to or greater than that of the determined steering torque TQInTh (S11: YES), the process continues to the next step S12. In step S12, a steering offset flag FLG1 is set to ON. The steering offset flag FLG1 is a flag that is set to ON when steering is performed during the execution of the power steering control, and to OFF when steering is not performed during the execution of the power steering control. The current processing routine then terminates temporarily. Conversely, in step S11, if the absolute value of the steering torque |TQIn| is less than that of the determined steering torque TQInTh (NO), the processing continues to the next step S13. In step S13, the steering offset flag FLG1 is set to OFF. The current processing routine then terminates temporarily. Next, a processing routine is described that is executed by the curve control unit 72 to perform the yaw control (see Fig. 3). This processing routine is executed repeatedly for each predetermined control cycle when the execution conditions of the curve control are met. These conditions include that the travel route TR is defined and that the execution of vehicle control along the travel route TR is permitted. In the present processing routine, step S21 determines whether the steering assist flag FLG1 is set to OFF. If the steering assist flag FLG1 is set to OFF (S21: YES), it is determined that steering is not being performed, and therefore the steering-not-performed cornering assist control, which comprises steps S22 to S26, is executed. Specifically, in step S22 of the steering-not-performed cornering assist control, it is determined whether the vehicle is approaching a lane marking. The lane marking is a line located at one lateral end of the lane. Determining whether the vehicle is approaching the lane marking can be done by analyzing an image obtained from an imaging device that captures an image of the area in front of the vehicle.As the vehicle approaches the boundary line, there is a risk that the vehicle will deviate from the lane. If it is determined that the vehicle is not approaching the boundary line (S22: NO), processing continues with the next step, S23. In step S23, a control variable DRR of the rear steering angle adjustment device 30 is obtained based on a deviation between the target cornering condition variable TSQTr, obtained by the target cornering condition acquisition unit 76, and the cornering condition variable TSQ. Next, in step S24, output processing is performed to output the control variable to each control unit. In this case, the control variable DRR obtained in step S23 is output to the rear steering control unit 36. Furthermore, "0 (zero)" is output to the brake control unit 46 as the control variable DRBa of the brake device 40, and "0 (zero)" is output to the front steering control unit 16 as the control variable DRF of the front steering angle adjustment device 10.The current processing routine will then be temporarily terminated. In this case, the rear steering angle adjustment device 30 controls the rear steering actuator 31 based on the input control variable DRR. Therefore, the rear steering angle θR becomes a steering angle corresponding to the control variable DRR. Since, on the other hand, the control variable DRBa input to the brake device 40 is "0 (zero)," the brake device 40 does not generate the braking force differential between the right front wheel FR and the left front wheel FL. Since the control variable DRF input to the front steering angle adjustment device 10 is "0 (zero)," the front steering angle adjustment device 10 maintains the front steering angle θF at "0 (zero)." That is, while the rear steering angle adjustment device 30 is operating, the front steering angle adjustment device 10 and the brake control unit 46 are not operating. If, on the other hand, it is determined in step S22 that the vehicle is approaching the lane marking (YES), processing continues with the next step S25. In step S25, the control variable DRR of the rear wheel steering angle adjustment device 30 and the control variable DRBa of the brake device 40 are obtained based on the deviation between the target cornering condition variable TSQTr obtained by the acquisition unit 76 and the cornering condition variable TSQ. This example describes a case where the vehicle is detected as approaching the lane marking, even though it is detected that the vehicle is not approaching the lane marking in an initial stage of the cornering assist control. In this case, when it is detected that the vehicle is not approaching the lane marking, a value corresponding to the deviation between the target cornering condition variable TSQTr and the cornering condition variable TSQ is set as the control variable DRR of the rear wheel steering angle adjustment device 30. Then, when a state in which the vehicle is detected as not approaching the lane marking is changed to a state in which the vehicle is detected as approaching the lane marking, the control variable DRR of the rear wheel steering angle adjustment device 30 is held at a value prior to the change.On the other hand, the control parameter DRBa of the brake device 40 is obtained based on the deviation between the target cornering condition parameter TSQTr and the parameter TSQ of the cornering condition. Accordingly, the control parameter DRBa of the brake device 40 is set to a value that can correct a deviation between the center of gravity of the vehicle in a lateral direction and the center of gravity of the lane in the same lateral direction. Once the control variables DRR and DRBa are obtained, processing continues with the next step S26. In step S26, output processing is performed to output the control variable to each control unit. In this case, the control variable DRR obtained in step S25 is output to the rear-wheel steering control unit 36, and the control variable DRBa is output to the brake control unit 46. Furthermore, "0 (zero)" is output to the front-wheel steering control unit 16 as the control variable DRF of the front-wheel steering angle adjustment device 10. The current processing routine then terminates temporarily. In this case, the rear steering angle adjustment device 30 controls the rear steering actuator 31 based on the input control variable DRR. Therefore, the rear steering angle θR becomes the steering angle corresponding to the control variable DRR. Furthermore, the brake actuator 41 in the brake device 40 is controlled based on the input control variable DRBa. Therefore, a braking force differential corresponding to the control variable DRBa is generated between the right front wheel FR and the left front wheel FL. On the other hand, since the control variable DRF input to the front steering angle adjustment device 10 is "0 (zero)," the front steering angle adjustment device 10 maintains the front steering angle θF at "0 (zero)." That is, while the rear steering angle adjustment device 30 and the brake device 40 are actuated, the front steering angle adjustment device 10 is not actuated. On the other hand, in step S21, if the steering monitoring flag FLG1 is set to ON (NO), it is determined that steering is being performed, and thus the steering-is-being-performed cornering assist control, which comprises steps S27 to S29, is executed. This means that during the steering-is-being-performed cornering assist control in step S27, a slip angle β of the vehicle is achieved. The slip angle β can be obtained, for example, based on the front wheel steering angle θF and the rear wheel steering angle θR. That is, the slip angle β of the vehicle can be controlled by adjusting the front wheel steering angle θF and the rear wheel steering angle θR. In a next step S28, the control variable DRF of the front wheel steering angle adjustment device 10, the control variable DRR of the rear wheel steering angle adjustment device 30 and the control variable DRBa of the brake device 40 are obtained on the basis of the target cornering condition variable TSQTr obtained by the acquisition unit of target cornering condition variable 76, a deviation between the target vehicle body slip angle βTr and the vehicle body slip angle β and the steering angle Str. For example, a value corresponding to the steering angle Str is set as the control variable DRF of the front steering angle adjustment device 10. Furthermore, a value corresponding to the deviation between the target slip angle βTr and the slip angle β of the vehicle is set as the control variable DRR of the rear steering angle adjustment device 30. A value corresponding to a deviation between a predicted value of the cornering condition variable and the target cornering condition variable TSQTr, when the front steering angle adjustment device 10 and the rear steering angle adjustment device 30 are controlled based on the control variables DRF and DRR, is obtained as the control variable DRBa of the brake device 40. Therefore, if the deviation between the predicted value of the cornering condition variable and the target cornering condition variable TSQTr is "0", "0" can be set as the control variable DRBa. Then, in step S29, the output processing is executed to output the control variable to each control unit. In this case, the control variable DRF obtained in step S28 is output to the front-wheel steering control unit 16, the control variable DRR to the rear-wheel steering control unit 36, and the control variable DRBa to the brake control unit 46. The current processing routine is then temporarily terminated. In this case, the front steering angle adjustment device 10 controls the front steering actuator 11 based on the input control variable DRF. Therefore, the front steering angle θF becomes a steering angle corresponding to the control variable DRF. Furthermore, in the rear steering angle adjustment device 30, the actuator 31 for the rear steering is controlled based on the input control variable DRR. Therefore, the rear steering angle θR becomes the steering angle corresponding to the control variable DRR. Furthermore, in the brake device 40, the brake actuator 41 is controlled based on the input control variable DRBa. Therefore, a braking force differential corresponding to the control variable DRBa is generated between the right front wheel FR and the left front wheel FL.Accordingly, by controlling the front wheel steering angle adjustment device 10, the rear wheel steering angle adjustment device 30 and the brake device 40, it can be ensured that the cornering condition variable TSQ follows the target cornering condition variable TSQTr and that the body slip angle β follows the target body slip angle βTr. Next, a processing routine executed by the steering instruction unit 73 for controlling the steering device 20 is described with reference to Fig. 4. This processing routine is executed during each predetermined control cycle when the steering assistance control is performed. In the present processing routine, step S41 determines whether the steering monitoring flag FLG1 is set to OFF. If the steering deflection flag FLG1 is set to OFF (S41: YES), it is determined that steering is not being performed, and the processing therefore proceeds to the next step S42. In step S42, a self-aligning torque TQsat is obtained based on the vehicle's body speed VS, yaw rate Yr, and similar parameters. Next, in step S42, the self-aligning torque TQsat is set as the reaction force suppression torque TQS. In the following step S43, an output processing operation is performed, in which the steering control unit 26 is informed that the reaction force suppression torque TQS obtained in step S42 is applied to the steering wheel 21. In this embodiment, the reaction force suppression torque TQS obtained in step S42 corresponds to the holding torque, which is a torque for maintaining the steering angle Str at the neutral point StrC. That is, obtaining the reaction force suppression torque TQS and outputting it to the steering control unit 26 correspond to the instruction to the steering device 20 to maintain the steering angle Str at the neutral point StrC. The current processing routine is then temporarily terminated. In this case, the steering actuator 22 in the steering device 20 is controlled such that the input reaction force suppression torque TQS is applied to the steering wheel 21. Therefore, the steering angle Str is maintained at the neutral point StrC. On the other hand, in step S41, if the steering monitoring flag FLG1 is set to ON (NO), it is determined that steering is taking place, and thus the processing continues to the next step S45. In step S45, an auxiliary torque TQAs is obtained, which is a torque to assist the driver when steering. That is, a value corresponding to the steering torque TQIn input into the steering wheel 21 is set as the auxiliary torque TQAs. The absolute value of the auxiliary torque TQAs increases with the absolute value of the steering torque TQIn. In the next step S46, output processing is performed, in which a message is sent to the steering control unit 26 indicating that the auxiliary torque TQAs obtained in step S45 should be applied to the steering wheel 21.This means that obtaining the support torque TQAs and outputting the support torque TQAs to the steering control unit 26 correspond to the instruction to the steering device 20 to assist the driver in steering. Afterwards, the current processing routine is temporarily terminated. In this case, the steering actuator 22 in the steering device 20 is controlled so that the input support torque TQAs acts on the steering wheel 21. This allows the driver to be assisted when steering. The functions and effects of the present embodiment are then described. If steering is not performed during the execution of the steering assistance control, the front wheel steering angle θF is held at "0 (zero)." Therefore, when the reaction force suppression torque TQS corresponding to the holding torque is obtained, it is necessary to obtain a torque component corresponding to the slip angle β, and not a torque component corresponding to the front wheel steering angle θF. Since it is not necessary to obtain the torque component corresponding to the front wheel steering angle θF, the steering angle Str can be maintained at the neutral point StrC, while reducing the increase in the computational load of the vehicle control device 70. If steering is not performed during the execution of the cornering assistance control, the braking device 40 is also driven if there is a possibility that the vehicle may deviate from the lane, since only the rear-wheel steering angle adjustment device 30 is operated. By driving the braking device 40 in this way in addition to the rear-wheel steering angle adjustment device 30, the controllability when assisting the vehicle's automatic lane keeping can be improved. When steering is performed during the execution of the power steering control, the front wheel steering angle θF is adjusted in accordance with the change in the steering angle Str by actuating the front wheel steering angle adjustment device 10. Accordingly, in contrast to the case where the front wheel steering angle θF is held at “0 (zero)” even when steering is performed, the calculation of the magnitude of the torque applied by the steering actuator 22 to the steering wheel 21 is expected to be less complicated. When steering is performed during the execution of the power steering control, the front wheel steering angle θF and the rear wheel steering angle θR are also adjusted. Therefore, in addition to the cornering condition parameter TSQ, the body slip angle β can also be controlled. Consequently, the controllability of the vehicle's steering behavior during the steering maneuver can be improved. When steering is performed while the power steering control is active, a scenario is considered in which the target cornering condition variable TSQTr is set as the sum of a value prior to steering initiation and the value corresponding to the steering angle Str. In this case, the target value TSQTr can increase rapidly at the start of steering, and the vehicle's yaw moment can also increase rapidly. This sudden change in the vehicle's yaw moment may be perceived as unpleasant by the driver. In contrast, in the present embodiment, when steering is performed during the execution of the power steering control, the target cornering state parameter TSQTr is obtained based on the parameter with the larger absolute value of the required cornering state parameter TSQR and the target automatic cornering state parameter TSQATr. Accordingly, a sudden increase in the target cornering state parameter TSQTr at the start of steering can be prevented. That is, the vehicle's yaw moment can be prevented from increasing abruptly at the start of steering. This makes it less likely that the driver will perceive the vehicle's steering behavior at the beginning of the steering process as unpleasant. The embodiment described above can be modified and implemented as follows. The embodiment described above and the following modifications can be implemented in combination, provided that the embodiment and the modifications do not exhibit any technical contradictions. When the steering-is-executed cornering support control is executed, the target cornering state variable TSQTr can be a different value than the parameter with the larger absolute value, as long as the target cornering state variable TSQTr is obtained based on the parameter with the larger absolute value of the required cornering state variable TSQR and the target automatic cornering state variable TSQATr. For example, a value obtained by adding a predefined offset value to the parameter with the larger absolute value can be obtained as the target cornering state variable TSQTr.- When the steering-is-executed cornering assist control is executed, a sum of the target value for the steering state before steering begins and the value corresponding to the steering angle Str can be set as the target cornering state value TSQTr. - When the braking device 40 is operated by executing the steering assist control, the yaw moment in the vehicle can be generated by producing the braking force differential between the right rear wheel RR and the left rear wheel RL. - When the steering-is-not-executed cornering assist control is executed, the rear wheel steering angle adjustment device 30 can be operated without operating the braking device 40. In this case, when it is determined that steering is being executed, i.e.,When the steering-is-executed cornering assist control is activated, the front-wheel steering angle adjustment device 10 and the rear-wheel steering angle adjustment device 30 can be operated, and the braking device 40 cannot be operated. When the steering-is-not-executed cornering assist control is activated, the rear-wheel steering angle adjustment device 30 must not be operated, and the braking device 40 may be operated. In this case, if it is determined that steering is being executed, i.e., when the steering-is-executed cornering assist control is activated, the front-wheel steering angle adjustment device 10 and the braking device 40 can be operated, and the rear-wheel steering angle adjustment device 30 cannot be operated. In this case, the driving control device can be applied to a vehicle that does not have the rear-wheel steering angle adjustment device 30.An example of a vehicle is one with a drive motor for a right wheel and a drive motor for a left wheel. In this case, the drive of the motor assigned to the right wheel and the drive of the motor assigned to the left wheel generates a difference between the drive torque supplied to the right wheel and the drive torque supplied to the left wheel, and a yaw moment equal to this difference can be generated in the vehicle. Therefore, when the vehicle control device 70 is applied to such a vehicle, a drive device comprising each drive motor and a control unit controlling each drive motor can be made to function as the yaw control device. The following describes the technical ideas that can be derived from the preceding embodiment and the modifications. (A) In the cornering assist control, when steering is performed, the cornering control unit preferably derives the control variable of the front wheel steering angle adjustment device and the control variable of the rear wheel steering angle adjustment device based on the deviation between the target cornering condition variable and the cornering condition variable and the deviation between the body slip angle and the target slip angle, which is the vehicle's target body slip angle, outputs the control variable of the front wheel steering angle adjustment device to the front wheel steering angle adjustment device, and outputs the control variable of the rear wheel steering angle adjustment device to the rear wheel steering angle adjustment device.

Claims

Driving control device (70) for a vehicle, which is to be applied to a vehicle with a front wheel steering angle adjustment device (10) configured to control a cornering condition variable, which is a condition variable relating to cornering of the vehicle, by adjusting a steering angle of a front wheel, a cornering control device provided and configured separately from the front wheel steering angle adjustment device (10) to control the cornering condition variable, and a steering device (20) comprising a steering wheel to which a steering torque is applied and which is connected to the front wheel, wherein the driving control device for a vehicle comprises: a cornering control unit (72) configured to perform cornering assistance control which causes the cornering condition variable to follow a target cornering condition variable, which is a target value of the cornering condition variable,by causing the front wheel steering angle adjustment device (10) and / or the cornering control device to operate; and a steering instruction unit (73) configured to obtain a holding torque, which is a torque that holds a steering wheel angle at a neutral point, when no steering is performed during the execution of the steering assistance control, and to instruct the steering device (20) to apply the holding torque to the steering wheel, wherein the cornering control unit (72) is configured to cause the cornering control device to operate, and to cause the front wheel steering angle adjustment device not to operate during cornering assistance control when steering is not performed, and to cause the front wheel steering angle adjustment device (10) to operate during cornering assistance control when steering is performed. Driving control device (70) for a vehicle according to claim 1, wherein the vehicle comprises as a cornering control device a rear wheel steering angle adjustment device (30) configured to adjust the cornering condition size by adjusting a steering angle of a rear wheel of the vehicle, and the cornering control unit (72) is configured to cause the front wheel steering angle adjustment device (10) and the rear wheel steering angle adjustment device (30) to operate during cornering support control when steering is performed. Driving control device (70) for a vehicle according to claim 2, wherein the vehicle comprises, as the cornering control device, a braking device (40) configured to control the cornering condition size by adjusting a braking force difference between a right wheel and a left wheel of the vehicle, and the cornering control unit (72) is configured to cause the rear wheel steering angle adjustment devices (30) and / or the braking device (40) to operate, and to cause the front wheel steering angle adjustment device (10) not to operate during cornering support control when steering is not performed. The driving control device (70) for a vehicle according to one of claims 1 to 3, further comprising: an adjustment unit of a required cornering condition parameter (74) configured to reference a steering-related value with respect to steering and to set a value corresponding to the steering-related value as a required cornering condition parameter, which is a required value of the cornering condition parameter; an adjustment unit of a target automatic cornering condition parameter (75) configured to set a target automatic cornering condition parameter, which is a target value of the cornering condition parameter for automatic cornering of the vehicle according to a set driving route;and a target cornering state variable (76) that is configured to obtain the target cornering state variable based on a state variable with a larger absolute value, from the required cornering state variable and the automatic target automatic cornering state variable.

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