Vehicle control device and vehicle control method

Abstract

This vehicle control device and this vehicle control method are configured to acquire vehicle momentum, such as lateral acceleration, generated in a vehicle and to control, when a steering device is automatically steered, the operation amount of a steering input member of the steering device on the basis of the vehicle momentum, such control being independent of the tire angle of the vehicle. As a result, during automatic steering, the operation amount of the steering input member can be safely and automatically controlled while information on the direction into which the vehicle turns is presented to a driver via a change in the operation amount of the steering input member.

Description

Vehicle control device and vehicle control method

[0001] The present invention relates to a vehicle control device and a vehicle control method.

[0002] The driving assistance system disclosed in Patent Document 1 is configured to change the steering characteristics in response to a change in the vehicle speed during the period from when automatic driving begins, between when the driver's steering ends and when the driver's steering resumes, and the change in steering characteristics includes reducing the steering angle of the vehicle's tires relative to the steering torque input by the driver in response to an increase in the vehicle speed during the period, and increasing the steering angle relative to the steering torque in response to a decrease in the vehicle speed during the period.

[0003] JP 2023-144726 A

[0004] For example, in the case of a steer-by-wire steering device in which a steering input member such as a steering wheel is mechanically separated from the steered wheels, during automatic steering (i.e., during automatic driving) that automatically controls the tire angle of the steered wheels, the operation amount of the steering input member (i.e., the operation position, steering angle, etc.) can be automatically controlled independently of the tire angle using the output of a steering reaction force actuator. Here, if the steering input member moves quickly in response to a sudden change in tire angle during automatic steering, the driver may be shocked. On the other hand, if the driver cannot obtain hints about future vehicle behavior, such as the direction the vehicle will turn, through changes in the operation amount of the steering input member, the driver may feel uneasy or distrustful of the automatic steering.

[0005] Therefore, an object of the present invention is to provide a vehicle control device and a vehicle control method that can safely automatically control the amount of operation of a steering input member while presenting future vehicle behavior to the driver through changes in the amount of operation of the steering input member during automatic steering.

[0006] In one aspect, the vehicle control device according to the present invention is a vehicle control device provided in a vehicle equipped with a steering device including a steering input member that accepts steering operation by a driver, and includes a vehicle momentum acquisition unit that acquires a vehicle momentum generated in the vehicle, and a target operation amount calculation unit that, when the steering device is automatically steered, calculates a target operation amount of the steering input member based on the vehicle momentum, independently of a tire angle of the vehicle, and outputs a signal of the target operation amount to the steering device.

[0007] Furthermore, one aspect of the vehicle control method according to the present invention is a vehicle control method executed by a control unit provided in a vehicle equipped with a steer-by-wire steering device including a steering input member that accepts steering operation by a driver, and when the steering device is automatically steered, the control unit controls the amount of operation of the steering input member based on the lateral acceleration generated in the vehicle, independently of the tire angle of the vehicle.

[0008] According to the present invention, during automatic steering, the amount of operation of the steering input member can be safely and automatically controlled while providing the driver with information on the direction in which the vehicle will turn via changes in the amount of operation of the steering input member.

[0009] 1 is a block diagram showing a vehicle control system. FIG. 1 is a block diagram showing in detail the control function of a steer-by-wire. FIG. 2 is a block diagram showing an example of a functional section for calculating a target operation amount from lateral acceleration. FIG. 3 is a diagram showing an example of a conversion table for calculating a target operation amount from lateral acceleration. FIG. 4 is a diagram showing another example of a conversion table for calculating a target operation amount from lateral acceleration. FIG. 5 is a diagram showing an example of a conversion table for calculating a target operation amount from lateral acceleration and vehicle speed. FIG. 6 is a time chart showing an example of the correlation between tire angle, vehicle speed, lateral acceleration, and target operation amount in autonomous driving. FIG. 7 is a diagram showing a state in which the operation amount of a steering input member is changed according to lateral acceleration. FIG. 8 is a time chart showing an example of a change in the correlation between tire angle and operation amount due to switching between manual driving and autonomous driving. FIG. 9 is a diagram showing an example of a conversion table for calculating a target operation amount from a combination of vehicle momentum such as lateral acceleration and lateral jerk or roll rate. FIG. 10 is a diagram showing look-ahead points for predicting vehicle momentum. FIG. 11 is a time chart showing setting of a target operation amount based on look-ahead vehicle momentum. FIG. 11 is a diagram showing a state in which the operation amount of a steering input member is changed according to look-ahead lateral acceleration. 1 is a functional block diagram of a process for calculating a target operation amount based on look-ahead vehicle momentum. FIG. 2 is a diagram illustrating a process for setting a target operation amount based on a plurality of look-ahead points. FIG. 3 is a diagram illustrating a process for setting all points on a target trajectory as look-ahead points. FIG. 4 is a diagram illustrating a process for calculating a target operation amount by definite integration. FIG. 5 is a diagram illustrating an example of a function of a weighting coefficient with a look-ahead distance as a variable. FIG. 6 is a diagram illustrating an example of a function of a weighting coefficient with a look-ahead distance as a variable. FIG. 7 is a diagram illustrating an example of a correlation between the curvature of a target trajectory, a differential value of the curvature, and a look-ahead time. FIG. 8 is a diagram illustrating an example of a correlation between a lane width and a look-ahead time. FIG. 9 is a diagram illustrating setting characteristics of the look-ahead time when the curvature of the target trajectory is small and the road width is wide. FIG. 10 is a diagram illustrating look-ahead points on continuous curves with large curvature. FIG. 11 is a diagram illustrating an example of a correlation between driving complexity and look-ahead time. FIG. 12 is a diagram illustrating setting of look-ahead points when making a vehicle follow a leading vehicle.1 is a diagram showing how to set look-ahead points when the vehicle is not allowed to follow a preceding vehicle. FIG. 2 is a diagram showing how to set look-ahead points when the vehicle is not allowed to follow a preceding vehicle. FIG. 3 is a diagram showing look-ahead points in a target trajectory for avoiding an obstacle. FIG. 4 is a diagram showing look-ahead points when a target trajectory for avoiding an obstacle is not set. FIG. 5 is a diagram showing look-ahead points in a target trajectory in emergency driving. FIG. 6 is a diagram showing setting characteristics of target operation amounts in emergency driving. FIG. 7 is a flowchart showing an adjustment process when switching from manual driving to automatic driving. FIG. 8 is a functional block diagram showing a calculation process of the adjusted target operation amount. FIG. 9 is a flowchart showing an adjustment process when switching from automatic driving to manual driving. FIG. 10 is a functional block diagram showing a calculation process of the adjusted target tire angle. FIG. 11 is a timing chart showing how the tire angle and operation amount change when switching from automatic driving to manual driving.

[0010] Hereinafter, embodiments of a vehicle control device and a vehicle control method according to the present invention will be described with reference to the drawings. Fig. 1 is a block diagram showing one aspect of a vehicle control system 200 that is mounted on a vehicle 100, such as a four-wheeled automobile, to control the motion of the vehicle 100. The vehicle control system 200 is a system that enables automatic driving (automatic steering) of the vehicle 100 to travel along a target trajectory, and includes an external environment recognition unit 300, a vehicle momentum detection unit 400, a vehicle control device 500, and a travel actuator unit 600.

[0011] The external environment recognition unit 300 includes various sensor devices for acquiring external environment information of the vehicle 100. The external environment recognition unit 300 includes sensor devices such as a GPS (Global Positioning System) receiving unit 310, a map database 320, a road-to-vehicle communication device 330, a camera 340, a radar 350, and a LiDAR (Light Detection and Ranging, Laser Imaging Detection and Ranging) 360.

[0012] The GPS receiver 310 receives signals from GPS satellites to measure the latitude and longitude of the position of the vehicle 100. The map database 320 is formed in a storage device mounted on the vehicle 100, and the map information in the map database 320 includes information such as road positions, road shapes, and intersection positions.

[0013] The road-to-vehicle communication device 330 is a device that communicates with roadside units, transmits information about the vehicle 100 to the roadside units, and receives road traffic information such as curves and intersections from the roadside units. Note that the external environment recognition unit 300 may include a vehicle-to-vehicle communication device that communicates with other vehicles to acquire road traffic information, behavior information of other companies, and the like from the other vehicles.

[0014] The camera 340 is a stereo camera, a monocular camera, a 360° camera, or the like, and captures images of the surroundings of the vehicle 100 to acquire image information of the surroundings of the vehicle 100. The radar 350 and the LiDAR 360 detect objects around the vehicle 100 and output information about the detected objects.

[0015] The vehicle momentum detection unit 400 includes a wheel speed sensor 410, an inertial measurement unit 420, etc. The wheel speed sensor 410 is a sensor that detects the rotational speed of each wheel of the vehicle 100, and the detection result of the wheel speed sensor 410 is used to estimate the speed of the vehicle 100.

[0016] In addition, the inertial measurement unit 420 detects accelerations (front-rear acceleration, lateral acceleration, and vertical acceleration) in the three axes of "front-rear," "left-right," and "up-down" of the vehicle 100, as well as angular velocities (pitch rate, roll rate, and yaw rate) in the three axes of "pitch," "roll," and "yaw" of the vehicle 100. Note that instead of the inertial measurement unit 420, an acceleration sensor and an angular velocity sensor can be separately provided in the vehicle 100. Also, instead of the inertial measurement unit 420, only an acceleration sensor can be provided in the vehicle 100.

[0017] The vehicle control device 500 is an electronic control device including a microcomputer 510 that performs calculations based on input information and outputs the calculation results, and the microcomputer 510 includes an MPU (Microprocessor Unit), a ROM (Read Only Memory), a RAM (Random Access Memory), etc. (not shown). The microcomputer 510 of the vehicle control device 500 acquires external environment recognition signals such as position information, road shape information, road surface information, and object information of the vehicle 100 from the external environment recognition unit 300, and also acquires vehicle momentum signals including wheel speed, acceleration and angular velocity applied to the vehicle 100 from the vehicle momentum detection unit 400.

[0018] The microcomputer 510 of the vehicle control device 500 then calculates a target command for autonomous driving based on the various types of information acquired, and outputs the calculated target command to the traveling actuator unit 600. The microcomputer 510 of the vehicle control device 500 includes, as software, functional units for autonomous driving, namely, a surrounding situation recognition unit 511, an action planning unit 512, a target trajectory generation unit 513, and a trajectory tracking control unit 514.

[0019] The surrounding situation recognition unit 511 recognizes the situation around the vehicle (in other words, the surrounding environment of the vehicle) based on the external environment recognition signal from the external environment recognition unit 300 and the vehicle momentum signal from the vehicle momentum detection unit 400. The situation around the vehicle recognized by the surrounding situation recognition unit 511 includes, for example, information about the road on which the vehicle 100 is traveling, such as the curvature of the road, the cant of the road surface, the gradient of the road surface, the friction coefficient μ of the road surface, the positions of the left and right lane markers, and the positions of the left and right road edges, as well as object information about moving objects and stationary objects around the vehicle 100.

[0020] The action planning unit 512 acquires the recognition result of the situation around the vehicle from the surrounding situation recognition unit 511, and creates an action plan for the vehicle 100 based on the acquired recognition result, including selection of a driving lane and selection of a traveling direction at intersections and branching points. The target trajectory generation unit 513 generates a target trajectory including commands for a trajectory and a vehicle speed when the vehicle 100 is to be automatically driven, based on the situation around the vehicle recognized by the surrounding situation recognition unit 511 and the action plan for the vehicle 100 created by the action planning unit 512. The trajectory following control unit 514 calculates control commands for causing the vehicle 100 to follow the target trajectory generated by the target trajectory generation unit 513, more specifically, a steering angle command and an acceleration or deceleration command which are control commands for controlling the traveling actuator unit 600, and outputs the calculated control commands.

[0021] The traveling actuator unit 600 includes a traveling motor 610 as a power source that generates a driving force for the vehicle 100, a braking device 620 that applies a braking force to the vehicle 100, a steering device 630 that changes the traveling direction of the vehicle 100 by changing the tire angle of the front wheels 101, 102 that are steered wheels of the vehicle 100, and an electronically controlled suspension 640 that can adjust the damping force and vehicle height. The traveling actuator unit 600 can operate the traveling motor 610 as a generator to apply a braking force (in other words, a regenerative braking force) to the vehicle 100.

[0022] Steering device 630 is of a steer-by-wire type and has a steering unit 630A and a steering unit 630B. Steering unit 630A has a steering input member 630A1 that receives a steering operation from the driver of vehicle 100, a steering reaction force actuator 630A2 that applies a steering reaction force to steering input member 630A1, and an operation amount sensor 630A3 that detects the operation amount (in other words, the steering angle) of steering input member 630A1.

[0023] The steering input member 630A1 may be a steering wheel, a dial, a stick, or the like. For example, when a steering wheel is used as the steering input member 630A1, the operation amount sensor 630A3 detects the rotation angle of the steering shaft as the operation amount (steering angle) of the steering input member 630A1. Furthermore, the steering reaction force actuator 630A2 is, for example, a steering reaction force motor, and when a steering wheel is used as the steering input member 630A1, the output of the steering reaction force motor is transmitted to the steering shaft via a reduction mechanism.

[0024] Steering unit 630B has steering actuator 630B1 that applies a steering force to front wheels 101, 102 that are steered wheels of vehicle 100, steering mechanism 630B2 that transmits the steering force generated by steering actuator 630B1 to the steered wheels, and tire angle sensor 630B3 that detects the tire angle (in other words, the steering angle) of front wheels 101, 102 that are steered wheels. For example, if a steering motor is used as steering actuator 630B1, steering mechanism 630B2 changes the tire angle of front wheels 101, 102 that are steered wheels by converting the rotational motion of the steering motor into linear motion of rack shaft 630B4 by a rack-and-pinion system. Here, steering unit 630A and steering unit 630B (in other words, steering input member 630A1 and front wheels 101, 102 that are steered wheels) are mechanically separated.

[0025] Microcomputer 510 of vehicle control device 500 has steer-by-wire control unit 515, which is a functional unit that controls steering device 630, more specifically, steering reaction force actuator 630A2 and steering actuator 630B1. Steer-by-wire control unit 515 has a function of controlling steering actuator 630B1 based on a target tire angle (target steering angle) during automatic driving (automatic steering) and manual driving (manual steering) of vehicle 100.

[0026] During automatic driving (during automatic steering), the tire angle for driving vehicle 100 along the target trajectory is set as the target tire angle, and during manual driving (during manual steering), the target tire angle is set according to the amount of operation of steering input member 630A1 by the driver. In other words, during manual driving, steering actuator 630B1 is controlled based on an electrical signal that indicates the amount of driving operation, which is the amount of operation of steering input member 630A1 by the driver, and the tire angles of front wheels 101, 102 are changed according to the steering operation of the driver.

[0027] Furthermore, during automatic driving (automatic steering) of vehicle 100, steer-by-wire control unit 515 determines a target operation amount (target steering angle) that is a target value in automatic control of the operation amount of steering input member 630A1 (for example, the rotation angle of the steering wheel) based on the vehicle momentum, independently of the tire angles of front wheels 101, 102. During automatic driving, steer-by-wire control unit 515 controls steering reaction force actuator 630A2 in accordance with the determined target operation amount, thereby having a function of automatically controlling the operation amount to set the operation amount of steering input member 630A1 to the target operation amount.

[0028] In other words, steering reaction force actuator 630A2 is used as an actuator for automatically varying the operation amount of steering input member 630A1 during automatic driving (automatic steering) of vehicle 100. As will be described in detail later, the vehicle momentum used for setting the target operation amount during automatic driving is, for example, lateral acceleration, and the target operation amount of steering input member 630A1 is determined based on the lateral acceleration generated during traveling in automatic driving. Therefore, during automatic driving, the operation amount of steering input member 630A1 is automatically controlled to a value corresponding to the vehicle momentum such as lateral acceleration generated during traveling in automatic driving.

[0029] This allows the driver to recognize the direction in which vehicle 100 will turn due to automatic driving based on a change in the amount of operation of steering input member 630A1 (such as the rotation angle of the steering wheel). This makes it possible to prevent the driver of vehicle 100 from feeling anxious or distrustful of automatic steering. Furthermore, a configuration in which the target amount of operation is set according to vehicle momentum such as lateral acceleration prevents sudden changes in the amount of operation of steering input member 630A1 compared to when the amount of operation is controlled to be proportional to the tire angle, thereby preventing shock to the driver.

[0030] 2 is a block diagram showing in detail the control functions of steer-by-wire control unit 515. Steer-by-wire control unit 515 has vehicle momentum acquisition unit 521, target tire angle calculation unit 522, driving operation amount acquisition unit 523, target operation amount calculation unit 524, and adjustment unit 525. Vehicle momentum acquisition unit 521 is a functional unit that acquires vehicle momentum such as lateral acceleration used to determine the target operation amount, and has vehicle momentum acquisition unit 521A and / or future vehicle momentum estimation unit 521B.

[0031] Vehicle momentum acquisition unit 521A acquires information about the vehicle momentum actually occurring in vehicle 100 in an autonomous driving state from the detection signal of vehicle momentum detection unit 400. Note that vehicle momentum acquisition unit 521A can acquire the vehicle momentum directly detected by vehicle momentum detection unit 400 as the vehicle momentum used to determine the target operation amount, and may also be configured to calculate the vehicle momentum used to determine the target operation amount from the vehicle momentum directly detected by vehicle momentum detection unit 400, external environment recognition information, etc.

[0032] Furthermore, future vehicle momentum estimation unit 521B determines the vehicle momentum estimated to occur in vehicle 100 at a future time point a predetermined time from the present time, based on the target trajectory for autonomous driving, more specifically, the curvature of the target trajectory, the target vehicle speed at each point on the target trajectory, etc. Here, the vehicle momentum used to set the target operation amount includes the lateral acceleration (lateral acceleration) described above, as well as lateral jerk, roll angle, roll rate, yaw rate, vehicle body sideslip angle, etc., and vehicle momentum acquisition unit 521 acquires at least one of these vehicle momentum amounts.

[0033] During automatic driving in which the steering device 630 is automatically steered, the target operation amount calculation unit 524 calculates the target operation amount of the steering input member 630A1 based on the vehicle momentum such as the lateral acceleration acquired by the vehicle momentum acquisition unit 521, independently of the tire angle of the front wheels 101, 102 (steered wheels), and outputs a signal of the calculated target operation amount. Note that the target operation amount calculation unit 524 sets the target operation amount to a value in the operation direction corresponding to the turning direction of the vehicle 100, and increases the absolute value of the target operation amount as the absolute value of the vehicle momentum increases.

[0034] Meanwhile, driving operation amount acquisition unit 523 acquires the amount of operation of steering input member 630A1 by the driver from the output of operation amount sensor 630A3. Then, target tire angle calculation unit 522 calculates a target tire angle for driving vehicle 100 along the target trajectory based on the target trajectory in autonomous driving, and also calculates a target tire angle corresponding to the amount of driving operation by the driver from the amount of operation of steering input member 630A1 by the driver (driving operation amount) and the steering gear ratio. Note that the steering gear ratio is set variably based on the vehicle speed, etc.

[0035] Adjustment unit 525 acquires information on the target operation amount calculated by target operation amount calculation unit 524 and the target tire angle calculated by target tire angle calculation unit 522. Then, when switching from manual driving to automatic driving and when switching from automatic driving to manual driving, adjustment unit 525 adjusts the target operation amount or target tire angle in order to adjust the amount of deviation between the operation amount of steering input member 630A1 and the tire angle of front wheels 101, 102 (steered wheels), and outputs the adjusted target value to steering device 630.

[0036] Here, steering reaction force actuator 630A2 is controlled so that the amount of operation of steering input member 630A1 becomes the target amount of operation output by adjustment unit 525. Also, steering actuator 630B1 is controlled so that the tire angle of front wheels 101, 102 (steered wheels) becomes the target tire angle output by adjustment unit 525. Note that in the automatic control of the amount of operation of steering input member 630A1 and the automatic control of the tire angle of front wheels 101, 102 (steered wheels), feedback control is implemented in which a control operation signal is determined based on the deviation between a target value and an actual value (a value detected by a sensor).

[0037] 3 to 6 are diagrams illustrating examples of the calculation process of the target operation amount based on lateral acceleration when the target operation amount calculation unit 524 sets the target operation amount according to the lateral acceleration that actually occurs during autonomous driving. Fig. 3 shows the calculation process in which the target operation amount calculation unit 524 obtains the target operation amount from the lateral acceleration by multiplying the lateral acceleration by a fixed ratio constant.

[0038] 4 shows a calculation process in which target operation amount calculation unit 524 has a conversion table with a characteristic that the absolute value of the target operation amount increases at a constant rate with an increase in the absolute value of the lateral acceleration, and the target operation amount is calculated from the lateral acceleration by referring to the conversion table. Note that in FIG. 4, the plus and minus signs of the lateral acceleration and the target operation amount represent the direction in which the lateral acceleration occurs (in other words, the turning direction of vehicle 100) and the operation direction (left / right steering direction) of steering input member 630A1 from the neutral position.

[0039] 5 shows a calculation process for determining a target operation amount from lateral acceleration using a conversion table, similar to the calculation process shown in Fig. 4, but in the case of the calculation process shown in Fig. 5, the calculation process determines a target operation amount from lateral acceleration using a nonlinear table in which the target operation amount does not exceed a predetermined maximum value (upper limit value) as the lateral acceleration increases, in other words, the target operation amount changes according to the lateral acceleration within a predetermined variable range including the neutral position. For example, even if automatic steering is performed to avoid danger (avoid a collision) of the vehicle 100 and the lateral acceleration acting on the vehicle 100 increases, the calculation process for the target operation amount shown in Fig. 5 limits the target operation amount to within a predetermined maximum limit value (maximum operation amount).

[0040] 5 prevents the operation amount of steering input member 630A1 from being automatically controlled to an amount greater than necessary even if the lateral acceleration acting on vehicle 100 increases. For example, even in a situation in which a lateral acceleration of about 0.2 G occurs due to danger avoidance (collision avoidance), it becomes possible to set the rotation angle of the steering wheel serving as steering input member 630A1 to be limited to 90 degrees or less.

[0041] 6 shows a calculation process for determining the target operation amount from the lateral acceleration using a nonlinear table that limits the increase in the target operation amount, similar to the calculation process shown in FIG. 5, but is configured so that the characteristic for determining the target operation amount from the lateral acceleration is changed depending on the vehicle speed at that time. Specifically, even if the lateral acceleration is the same, the characteristic (gain) for determining the target operation amount from the lateral acceleration is changed depending on the vehicle speed so that the target operation amount is set to a larger value as the vehicle speed of the vehicle 100 increases.

[0042] According to this calculation process, even in a driving situation where lateral acceleration is unlikely to occur, such as when vehicle 100 is traveling at high speed, the driver can be made aware of the direction in which vehicle 100 will move due to automatic driving (automatic steering) based on a change in the operation amount (such as the rotation angle of the steering wheel) of steering input member 630A1. Note that even in a calculation process that determines the target operation amount from the lateral acceleration using a linear characteristic, such as the calculation process shown in Figure 3 or 4, the ratio constant and gain can be increased as the vehicle speed increases.

[0043] 7 is a time chart showing changes in the tire angle, vehicle speed, lateral acceleration, and target operation amount when the operation amount of steering input member 630A1 is automatically controlled to a target operation amount corresponding to the lateral acceleration occurring in vehicle 100 during automatic driving of vehicle 100. In this case, lateral acceleration occurs according to the automatically controlled tire angle and vehicle speed, the target operation amount of steering input member 630A1 is determined according to the generated lateral acceleration using the characteristics exemplified in FIGS. 3 to 6, and steering reaction force actuator 630A2 is controlled so that the operation amount of steering input member 630A1 becomes the target operation amount.

[0044] 8 , automatic steering causes the tire angles of the front wheels 101, 102 (steered wheels) to turn left from the neutral position, generating leftward lateral acceleration. Due to this leftward lateral acceleration, the operation amount of the steering input member 630A1 (the rotation angle of the steering wheel) is automatically controlled in the leftward turning direction from the neutral position. Similarly, automatic steering causes the tire angles of the front wheels 101, 102 to turn right from the neutral position, generating rightward lateral acceleration. Due to this rightward lateral acceleration, the operation amount of the steering input member 630A1 is automatically controlled in the rightward turning direction from the neutral position. Then, when automatic steering returns the tire angles of the front wheels 101, 102 to the neutral position and the lateral acceleration ceases to be generated, the operation amount of the steering input member 630A1 is also automatically returned to the neutral position.

[0045] 9 is a time chart illustrating changes in the tire angle and the operation amount of the steering input member 630A1 when the vehicle moves from manual driving to automatic driving and back to manual driving in a configuration in which the target operation amount of the steering input member 630A1 is set based on the lateral acceleration occurring in the vehicle 100 during automatic driving. In manual driving, the tire angle is changed according to the operation amount of the steering input member 630A1, and the operation amount of the steering input member 630A1 and the tire angle are linked while maintaining a predetermined steering gear ratio.

[0046] On the other hand, in autonomous driving, the amount of operation of the steering input member 630A1 is changed in accordance with the lateral acceleration occurring in the vehicle 100, independent of the tire angle. This makes it possible to prevent a sudden or large change in the amount of operation of the steering input member 630A1 even when the vehicle 100 is avoiding danger (avoiding a collision), and the steering input member 630A1 also automatically turns in the turning direction of the vehicle 100 at approximately the same time as the driver of the vehicle 100 feels centrifugal force. This makes it possible to achieve autonomous driving (autonomous steering) that is less uncomfortable for the driver and that prevents anxiety and distrust from occurring.

[0047] Note that acquisition of the lateral acceleration occurring in vehicle 100 by vehicle momentum acquisition unit 521A is not limited to acquisition of a detection value (output value of an acceleration sensor) by inertial measurement unit 420 of vehicle momentum detection unit 400, and an estimated value of the lateral acceleration can be acquired. For example, vehicle momentum acquisition unit 521A can acquire the lateral acceleration estimated from tire angle δ and vehicle speed V according to Equation 1. Note that in Equation 1, A is the stability factor, and l (lowercase l) is the wheelbase. Furthermore, the vehicle momentum acquisition unit 521A can acquire the lateral acceleration estimated from the detection result of the vehicle position by the GPS, and the lateral acceleration estimated from the image of the camera 340.

[0048] Furthermore, the control is not limited to determining the target operation amount from the lateral acceleration, and the vehicle momentum acquisition unit 521A can acquire at least one of the lateral acceleration, lateral jerk, roll angle, roll rate, yaw rate, vehicle body sideslip angle, etc., and the target operation amount calculation unit 524 can calculate the target operation amount based on these. Here, when the vehicle momentum acquisition unit 521A acquires any one of the lateral acceleration, roll angle, yaw rate, and vehicle body sideslip angle as the vehicle momentum, the target operation amount calculation unit 524 can calculate the target operation amount with the characteristics shown in Figures 3 to 5 described above.

[0049] 3 to 5 can be interpreted as any one of the following: "roll angle," "yaw rate," and "vehicle body sideslip angle." When the target operation amount is calculated according to the roll angle, the driver can grasp the stability of the vehicle 100 when cornering or making a sudden change in direction through the operation amount of the steering input member 630A1.

[0050] Furthermore, when the target operation amount is calculated according to the yaw rate, the driver can grasp, through the operation amount of the steering input member 630A1, the possibility of slipping or sliding of the vehicle 100. Furthermore, when the target operation amount is calculated according to the vehicle body sideslip angle, the driver can grasp, through the operation amount of the steering input member 630A1, the stable running state of the vehicle 100, in which an appropriate vehicle body sideslip angle is maintained.

[0051] Furthermore, the control process may be such that the target manipulated variable is calculated from a combination of any one of lateral acceleration, roll angle, yaw rate, and vehicle body sideslip angle with the lateral jerk or roll rate. Figure 10 is a diagram illustrating an example of the characteristics of calculating the target manipulated variable from a combination of any one of lateral acceleration, roll angle, yaw rate, and vehicle body sideslip angle with the lateral jerk or roll rate.

[0052] Here, the absolute value of the target operation amount is increased as the absolute values ​​of the lateral acceleration, roll angle, yaw rate, and vehicle body sideslip angle increase, while the absolute value of the target operation amount is increased as the absolute value of the lateral jerk or roll rate decreases, even if the absolute values ​​of the lateral acceleration, roll angle, yaw rate, and vehicle body sideslip angle remain the same. If the target operation amount is changed in accordance with the lateral jerk, the driver can grasp the sudden turn of the vehicle 100 and the ride comfort through the operation amount of the steering input member 630A1. Furthermore, if the target operation amount is changed in accordance with the roll rate, the driver can grasp the effect of sudden cornering or sudden turn of the vehicle 100 on the vehicle 100 through the operation amount of the steering input member 630A1.

[0053] Incidentally, the vehicle momentum such as lateral acceleration used in the calculation of the target operation amount is not limited to the vehicle momentum occurring in vehicle 100 at the present time (in other words, the vehicle momentum in the running state of vehicle 100 due to automatic steering), but can also include the vehicle momentum at a future time point estimated from the target trajectory. In other words, when vehicle 100 is caused to run along the target trajectory, future vehicle momentum estimator 521B can estimate (look ahead) the vehicle momentum at a point on the target trajectory to be reached in the future (hereinafter also referred to as a look-ahead point) shown in Figure 11 from the curvature of the target trajectory and the target vehicle speed at the look-ahead point.

[0054] Then, based on the future vehicle momentum acquired by future vehicle momentum estimation unit 521B, target operation amount calculation unit 524 can calculate the target operation amount of steering input member 630A1 with the characteristics shown in Figures 3 to 6 or 10. The look-ahead point is a point that is a predetermined distance ahead of the current position of vehicle 100, or a point that will be reached a predetermined time from the current point in time.

[0055] Here, the distance and arrival time from the current position to the look-ahead point can be fixed or can be variable based on vehicle momentum such as vehicle speed, and preferably the higher the vehicle speed, the farther the point from the current position. Furthermore, future vehicle momentum can be calculated at each of multiple different look-ahead points, and the final target operation amount can be calculated from the multiple future vehicle momentum calculated at each look-ahead point. Note that variable control of the look-ahead point and control for calculating the final target operation amount from the multiple future vehicle momentum calculated at each of multiple look-ahead points will be described in detail later.

[0056] 12 is a time chart showing the characteristics of the future lateral acceleration and the target operation amount when the future vehicle momentum estimator 521B acquires the future lateral acceleration as the future vehicle momentum. The future lateral acceleration is an amount that advances the phase of the lateral acceleration that is actually occurring in the vehicle 100, and the target operation amount based on the future lateral acceleration is a value that advances in phase with respect to the target operation amount based on the lateral acceleration that is actually occurring in the vehicle 100.

[0057] That is, the driver can sense a change in vehicle momentum, such as lateral acceleration, through a change in the amount of operation of steering input member 630A1, before the actual change in vehicle momentum occurs. In this way, with a configuration in which the target operation amount is calculated based on future lateral acceleration, future vehicle behavior is presented to the driver through a change in the amount of operation of steering input member 630A1, so the driver can recognize in advance how vehicle 100 will next be controlled by automatic driving (automatic steering), and the driver's anxiety can be reduced.

[0058] 13 illustrates an example of a change in the operation amount of the steering input member 630A1 relative to the curvature of the target trajectory at the look-ahead point. In other words, if the look-ahead point is a left curve, the operation amount of the steering input member 630A1 (the rotation angle of the steering wheel) is automatically controlled in advance in the left turn direction from the neutral position. Similarly, if the look-ahead point is a right curve, the operation amount of the steering input member 630A1 (the rotation angle of the steering wheel) is automatically controlled in advance in the right turn direction from the neutral position. Then, when the look-ahead point returns to a straight road, the operation amount of the steering input member 630A1 is also automatically returned to the neutral position.

[0059] 14 is a time chart illustrating changes in the tire angle and the operation amount of the steering input member 630A1 when the vehicle moves from manual driving to automatic driving and back to manual driving, in a case where a configuration is used in which the target operation amount of the steering input member 630A1 is set based on vehicle momentum such as lateral acceleration estimated to occur at a look-ahead point during automatic driving. In manual driving, the tire angle is changed according to the operation amount of the steering input member 630A1, and the operation amount of the steering input member 630A1 and the tire angle are linked while maintaining a predetermined steering gear ratio.

[0060] On the other hand, in autonomous driving, the operation amount of the steering input member 630A1 is changed according to the vehicle momentum estimated to occur at the look-ahead point, independent of the tire angle. In other words, before the vehicle momentum changes due to a change in the tire angle, the operation amount of the steering input member 630A1 is changed, and the upcoming vehicle behavior is presented to the driver in advance.

[0061] The target operation amount calculation unit 524 can calculate the target operation amount using both the vehicle momentum currently occurring in the vehicle 100 acquired by the vehicle momentum acquisition unit 521A and the future vehicle momentum (read-ahead vehicle momentum at the look-ahead point) acquired by the future vehicle momentum estimation unit 521B. The flowchart in Fig. 15 illustrates an example of a calculation process for calculating the target operation amount based on both the vehicle momentum acquired by the vehicle momentum acquisition unit 521A and the future vehicle momentum acquired by the vehicle momentum estimation unit 521B.

[0062] In step S801, the microcomputer 510 of the vehicle control device 500 generates a target trajectory for the autonomous driving of the vehicle 100. Next, in step S802, the microcomputer 510 calculates a look-ahead time for identifying a look-ahead point for estimating future vehicle momentum.

[0063] The look-ahead time may be a fixed value, or as will be described later, may be variable depending on various vehicle information (trajectory curvature, lane width, complexity of the driving environment, traffic signals, obstacles, preceding vehicles, etc.) The microcomputer 510 then calculates the look-ahead distance from the look-ahead time and the vehicle speed at that time.

[0064] The look-ahead distance is a value that determines how far ahead the vehicle momentum is to be estimated, and a point that is the look-ahead distance ahead from the current position of the vehicle 100 is set as the look-ahead point for estimating the vehicle momentum. Therefore, the higher the vehicle speed, the farther ahead the look-ahead point is set from the current position of the vehicle 100.

[0065] In step S803 (future vehicle momentum estimation unit 521B), microcomputer 510 estimates vehicle momentum such as lateral acceleration at the look-ahead point specified by the look-ahead distance, i.e., vehicle momentum occurring at a point the look-ahead distance ahead. Then, in step S804 (target operation amount calculation unit 524), microcomputer 510 calculates a first target operation amount (target operation amount based on the future vehicle momentum) from the future vehicle momentum (for example, future lateral acceleration) calculated in step S803.

[0066] Meanwhile, in step S805 (target tire angle calculation unit 522), microcomputer 510 calculates a target tire angle for causing vehicle 100 to travel along the target trajectory. Then, in step S806, microcomputer 510 controls the steering force generated by steering actuator 630B1 so that the actual tire angles of front wheels 101, 102 become the target tire angles.

[0067] Furthermore, in step S807 (vehicle momentum acquisition unit 521A, target operation amount calculation unit 524), microcomputer 510 acquires vehicle momentum, such as lateral acceleration, currently occurring in vehicle 100, as a sensor detection value or an estimated value based on tire angle, vehicle speed, etc., and calculates a second target operation amount (target operation amount based on the current vehicle momentum) from the acquired vehicle momentum. Then, in step S808, microcomputer 510 weights, for example, the first target operation amount (target operation amount based on future vehicle momentum) and the second target operation amount (target operation amount based on the current vehicle momentum) to determine a final target operation amount.

[0068] Here, the weighting of each of the first target operation amount and the second target operation amount may be fixed or may be variable based on a comparison of the magnitude of the first target operation amount and the second target operation amount. For example, the larger of the first target operation amount and the second target operation amount may be set as the final target operation amount. Furthermore, either the processing of steps S802 to S804 or the processing of step S807 may be omitted, and either the first target operation amount or the second target operation amount may be set as the final target operation amount.

[0069] Once the final target operation amount is set, in step S809, microcomputer 510 controls the operation force of steering input member 630A1 generated by steering reaction force actuator 630A2 so that the actual operation amount of steering input member 630A1 becomes the target operation amount. In other words, during autonomous driving, microcomputer 510 automatically controls the operation amount of steering input member 630A1 to a value corresponding to the vehicle momentum, independent of the tire angle.

[0070] 16 shows in detail the process of estimating the lateral acceleration at a look-ahead point specified by the look-ahead distance and calculating a target operation amount from the estimated lateral acceleration (future vehicle momentum), i.e., the functions of future vehicle momentum estimator 521B and target operation amount calculator 524. Future vehicle momentum estimator 521B has a look-ahead distance calculator 521B1, a look-ahead point extractor 521B2, and a lateral acceleration estimator 521B3.

[0071] The look-ahead distance calculation unit 521B1 acquires signals of a certain look-ahead time and the vehicle speed of the vehicle 100, and calculates the distance traveled at the current vehicle speed for the look-ahead time as the look-ahead distance, which is the travel distance to the look-ahead point where lateral acceleration is estimated. In other words, the higher the vehicle speed, the farther the look-ahead point is set to a point from the current position.

[0072] The look-ahead point extraction unit 521B2 acquires information on the curvature of the target trajectory and the target vehicle speed for each travel distance from the current position of the vehicle 100 from the target trajectory generation unit 513, and also acquires information on the look-ahead distance from the look-ahead distance calculation unit 521B1. Then, the look-ahead point extraction unit 521B2 uses linear interpolation to determine the curvature and vehicle speed (look-ahead curvature, look-ahead vehicle speed) at the look-ahead point where the travel distance from the current position of the vehicle 100 is the look-ahead distance.

[0073] The lateral acceleration estimation unit 521B3 acquires information on the curvature and vehicle speed at the look-ahead point from the look-ahead point extraction unit 521B2. Then, the lateral acceleration estimation unit 521B3 estimates the lateral acceleration that will occur in the vehicle 100 at the look-ahead point (in other words, future lateral acceleration) based on the information on the curvature and vehicle speed at the look-ahead point.

[0074] Here, the lateral acceleration estimation unit 521B3 calculates the lateral acceleration α at the look-ahead point according to Equation 2, where K (tilde) is the curvature at the look-ahead point and v (tilde) is the vehicle speed at the look-ahead point. c (tilde). The target operation amount calculation unit 524 receives the lateral acceleration α at the look-ahead point from the lateral acceleration estimation unit 521B3. c (tilde), for example, the lateral acceleration α c (tilde) is converted into a signal of the target manipulated variable by multiplying it by a set constant γ.

[0075] The estimation of the future vehicle momentum by the future vehicle momentum estimator 521B is not limited to the process of estimating the vehicle momentum occurring at one look-ahead point, but can estimate the future vehicle momentum at each of a plurality of different points on the target trajectory.The target operation amount calculator 524 can then calculate the target operation amount based on the plurality of future vehicle momentums.

[0076] 17 is a diagram illustrating a processing function for calculating a target operation amount based on future vehicle momentum estimated at each of a plurality of look-ahead points. In the example shown in Fig. 17, future vehicle momentum g(x1), g(x2), such as future lateral acceleration, estimated to occur at a nearby first look-ahead point with a look-ahead distance of x1 and a distant second look-ahead point with a look-ahead distance of x2 (x1<x2) are calculated.

[0077] Then, as shown in Equation 3, the microcomputer 510 weights the future vehicle momentum g(x1) and g(x2) with weighting coefficients c1 and c2 given as fixed values ​​to determine the target operation amount θ.

[0078] Here, the microcomputer 510 can vary the weighting of the future vehicle momentum g(x1), g(x2) estimated to occur at each look-ahead point in accordance with the look-ahead distances x1, x2. That is, the microcomputer 510 uses weighting coefficients c1(x1), c2(x2) corresponding to the look-ahead distances x1, x2 to determine the target operation amount θ according to Equation 4.

[0079] 18 shows a process for determining a target operation variable θ by determining all points on the target trajectory as look-ahead points, calculating the future vehicle momentum estimated to occur at each look-ahead point, and weighting each estimated future vehicle momentum according to the look-ahead point. Here, the target operation variable θ is determined according to Equation 5, where c(k) is the weighting coefficient at each look-ahead point and gk is the future vehicle momentum estimated at each look-ahead point.

[0080] 19 shows a process for determining a target manipulated variable θ by performing definite integration on the future vehicle momentum gk estimated at the look-ahead point, weighted in accordance with the distance from the current position of the vehicle 100 to the look-ahead point, and integrating the weighted value over the range from the current position of the vehicle 100 to the length D of the target trajectory. Here, the target manipulated variable θ is determined according to Equation 6.

[0081] When the weighting of the future vehicle momentum estimated at the look-ahead point is made variable depending on the distance from the current position of the vehicle 100 to the look-ahead point, the weighting of the look-ahead point that is closer to the current position of the vehicle 100 is made greater than the weighting of the look-ahead point that is farther from the current position of the vehicle 100. In other words, the longer the distance from the current position of the vehicle 100 to the look-ahead point (look-ahead distance), the smaller the weighting of the look-ahead point.

[0082] As shown in FIGS. 20 to 22, the weighting coefficient c(x) functions with the look-ahead distance x as a variable are c(x)=-cx+b, c(x)=1 / x, and c(x)=e- x Here, when the weighting coefficient c(x) is determined according to the function "c(x) = -cx + b" shown in Fig. 20, the target manipulated variable is calculated from a nearby first look-ahead point with a look-ahead distance of x1 and a distant second look-ahead point with a look-ahead distance of x2 (x1 < x2) (see Fig. 17), as shown in Equation 7.

[0083] Furthermore, when the weighting coefficient c(x) is determined in accordance with the function "c(x)=1 / x" shown in FIG. 21, the formula for calculating the target operation amount when determining the target operation amount from a nearby first look-ahead point with a look-ahead distance of x1 and a distant second look-ahead point with a look-ahead distance of x2 (x1<x2) (see FIG. 17) is Equation 8.

[0084] Also, the function "c(x)=e-" shown in FIG. x", the formula for calculating the target manipulated variable when the target manipulated variable is found from a nearby first look-ahead point with a look-ahead distance of x1 and a distant second look-ahead point with a look-ahead distance of x2 (x1<x2) (see FIG. 17) is Formula 9.

[0085] The following describes in detail the process of variably setting the look-ahead time in accordance with vehicle information in step S802 of the flowchart in Figure 15. Figure 23 illustrates an example of the correlation between the curvature of the target trajectory, the differential value of the curvature, and the look-ahead time. Here, the microcomputer 510 shortens the look-ahead time as the curvature of the target trajectory increases and the target trajectory curves sharply.

[0086] That is, the greater the curvature of the target trajectory, the shorter the look-ahead distance, and by determining the target operation amount based on the estimated vehicle momentum at a point closer to vehicle 100, microcomputer 510 presents information about vehicle behavior at a point closer to vehicle 100 to the driver via a change in the operation amount of steering input member 630A1. Furthermore, the greater the differential value of the curvature of the target trajectory and the greater the change in curvature, microcomputer 510 shortens the look-ahead time.

[0087] In other words, when traveling on a road with successive curves, such as a mountain road, the change in curvature becomes greater, and information about the vehicle behavior at points close to the vehicle 100 is presented to the driver via a change in the amount of operation of the steering input member 630A1. In this way, by setting the look-ahead time based on the curvature or curvature differential of the target trajectory, it is possible to appropriately provide the driver with hints about the vehicle behavior via the amount of operation of the steering input member 630A1 when the vehicle 100 travels around a curve.

[0088] 24 illustrates an example of the correlation between the lane width (road width) of the road on which the vehicle 100 is traveling and the look-ahead time. Here, the narrower the lane width, the shorter the look-ahead time is set by the microcomputer 510. In other words, the narrower the lane width, the more attention should be paid to points closer to the vehicle 100, so the narrower the lane width, the closer the look-ahead point is set to the vehicle 100.

[0089] Fig. 25 shows how the look-ahead time is set long (the look-ahead point is set far away) when the vehicle 100 is traveling on a road with a small curvature of the target trajectory and a wide road width, such as when the vehicle 100 is traveling on a highway. In contrast, Fig. 26 shows how the look-ahead time is set short and the look-ahead point is set just before the vehicle 100 when the vehicle 100 is traveling on a series of curves with a large curvature.

[0090] 27 illustrates an example of the correlation between the complexity of the driving environment and the look-ahead time. Here, the more complex the driving environment, the more attention should be paid to points closer to the vehicle 100. Therefore, the more complex the driving environment, the shorter the look-ahead time the microcomputer 510 sets. The microcomputer 510 determines the complexity of the driving environment based on the external environment recognized by the camera 340, map information, etc.

[0091] A complex driving environment means a situation where there is a high possibility of repeated small steering turns or sudden steering turns. Specifically, factors that can increase the complexity of a driving environment include continuous curves, narrow roads, heavy traffic, many obstacles such as parked vehicles, steep road gradients, and rain and snow.

[0092] Therefore, when the road on which vehicle 100 is traveling is a narrow road with no sidewalks, with many pedestrians walking on the shoulders, and with many oncoming vehicles, the complexity of the traveling environment is determined to be high. Conversely, when vehicle 100 is traveling on an uncongested highway, the complexity of the traveling environment is determined to be low. In this way, by variably setting the look-ahead time according to the complexity of the traveling environment, when the traveling environment is complex, it is possible to suggest to the driver, via the amount of operation of steering input member 630A1, vehicle behavior in the short distance that requires caution.

[0093] Here, in relation to the complexity of the driving environment, it is preferable to shorten the look-ahead time on mixed roads, so that on congested roads, the driver can be informed of vehicle behavior in the short distance that requires caution via the amount of operation of the steering input member 630A1.

[0094] Furthermore, when the traffic light ahead of vehicle 100 is a stop signal (red light), it is preferable to correct the look-ahead time (look-ahead distance) so that a position before the traffic light (stop line) is set as the look-ahead point, rather than a point ahead of the traffic light (stop line). This makes it possible to prevent the steering input member 630A1 from being moved from the neutral position due to the influence of the estimated result of the vehicle momentum at a point ahead of the stop line, when it is estimated that vehicle 100 will stop at the stop line ahead because the traffic light ahead is a stop signal (red light).

[0095] Furthermore, the microcomputer 510 can variably set the look-ahead time based on information about a preceding vehicle traveling ahead of the vehicle 100. Figures 28 and 29 show how to set the look-ahead time (look-ahead point) when there is a preceding vehicle that the vehicle 100 is to follow. When the vehicle 100 is to follow the preceding vehicle, the microcomputer 510 can set a look-ahead time that uses the traveling position of the preceding vehicle that is to be followed as the look-ahead point, instead of a look-ahead point based on a look-ahead distance corresponding to the look-ahead time and vehicle speed.

[0096] In this case, as shown in Fig. 28, if the preceding vehicle is traveling straight, the vehicle momentum at the look-ahead point indicates a straight-ahead state, and the steering input member 630A1 of vehicle 100 is held in the neutral position. On the other hand, if the preceding vehicle turns right as shown in Fig. 29, an operation amount in the right turn direction is set as the target operation amount, and it is possible to present to the driver via the operation amount of steering input member 630A1 that vehicle 100 will turn right to follow the preceding vehicle.

[0097] 30 and 31 show examples of the setting of the look-ahead point and the operation amount of the steering input member 630A1 when a leading vehicle is present but vehicle 100 is not made to follow the leading vehicle. In this case, if the look-ahead time is made variable, for example, according to the curvature of the target trajectory without being restricted by the traveling position of the leading vehicle, as shown in Fig. 30, when a target trajectory for a lane change to the right lane is set and the curvature of the target trajectory increases, the look-ahead time is shortened and the look-ahead point is set to immediately before vehicle 100.

[0098] Then, based on the target trajectory of right turn for lane change, the target operation amount of the steering input member 630A1 is set in the right turn direction. This makes it possible to notify the driver that a lane change will occur even when the vehicle 100 approaches a leading vehicle ahead, giving the driver a sense of security.

[0099] 31 , when vehicle 100 travels straight but the preceding vehicle turns right on a branching road, the target operation amount is set based on a target trajectory for vehicle 100 traveling straight, which is different from the trajectory of the preceding vehicle. As a result, the target operation amount of steering input member 630A1 is held in the neutral position, and it is possible to notify the driver, via the operation amount of steering input member 630A1, that the vehicle is traveling in a state where it is not following the preceding vehicle.

[0100] Furthermore, the microcomputer 510 can variably set the look-ahead time based on the recognition information of an obstacle present ahead of the vehicle 100. When an obstacle is present ahead of the vehicle 100, the microcomputer 510 can set the look-ahead time (look-ahead distance) so that a point in front of the obstacle becomes the look-ahead point.

[0101] In this case, if a target trajectory for avoiding an obstacle is set as shown in Figure 32, the target operation amount of the steering input member 630A1 is set corresponding to the path for avoiding the obstacle (a right-turn path in the case of Figure 32) based on the target trajectory. Therefore, the driver can predict, via a change in the operation amount of the steering input member 630A1, that automatic driving for avoiding an obstacle ahead will be performed.

[0102] 33, when a target trajectory for avoiding an obstacle ahead is not set and a target trajectory for vehicle 100 traveling straight toward the obstacle is set, the operation amount of steering input member 630A1 is held in the neutral position and no movement to avoid the obstacle is exhibited. This allows the driver to sense the risk of colliding with the obstacle and perform an override (manual steering operation) to avoid the obstacle.

[0103] Furthermore, during automated driving, when emergency danger avoidance driving (hereinafter referred to as emergency driving) is performed to deal with a pedestrian jumping out into the road, as shown in Fig. 34, it is preferable to limit the target operation amount for vehicle momentum such as lateral acceleration to a smaller value than during normal driving. In other words, as shown in Fig. 35, microcomputer 510 can change the maximum limit value of the target operation amount for vehicle momentum to a smaller value during emergency driving (emergency danger avoidance driving) than during normal driving.

[0104] In other words, during emergency driving, the microcomputer 510 can change the variable range of the target operation amount relative to the vehicle momentum to a narrower range including the neutral position than during normal driving, and calculate the target operation amount so that the operation amount is closer to the neutral position than during normal driving. This prevents a sudden large change in the operation amount of the steering input member 630A1, even if the vehicle momentum, such as lateral acceleration, increases sharply due to emergency driving, and prevents a shock from being felt by the driver. Note that during emergency driving, the microcomputer 510 can set a fixed target operation amount that is smaller than the maximum limit value of the target operation amount during normal driving.

[0105] The function of the adjustment unit 525 shown in the block diagram of Fig. 2 will be described in detail below. Fig. 36 is a diagram showing changes in the tire angle and the operation amount of the steering input member 630A1 when the driving of the vehicle 100 is switched from manual driving to automatic driving and then back from automatic driving to manual driving. The upper part of Fig. 36 shows a case where no adjustment is made by the adjustment unit 525, and the lower part of Fig. 36 shows a case where adjustment is made by the adjustment unit 525.

[0106] During automatic driving, microcomputer 510 determines the target operation amount of steering input member 630A1 based on the vehicle momentum, independently of the tire angle of vehicle 100. On the other hand, during manual driving, the tire angle and the operation amount of steering input member 630A1 change in conjunction with each other so as to maintain a predetermined steering gear ratio. Therefore, if no adjustment is made when switching from manual driving to automatic driving, the operation amount of steering input member 630A1 will be switched in a stepped manner from a value commensurate with the tire angle to a value based on the vehicle momentum, as shown in the upper part of Figure 36.

[0107] Furthermore, if no adjustment is made when switching from automatic driving to manual driving, the tire angle in automatic driving will be switched in a stepped manner to a tire angle corresponding to the amount of operation of the steering input member 630A1, as shown in the upper part of Fig. 36. In this way, if the tire angle and the amount of operation of the steering input member 630A1 are not adjusted when switching between manual and automatic driving, the amount of operation of the steering input member 630A1 and the tire angle will not change continuously, which may cause the driver to feel uncomfortable or result in unintended changes in the behavior of the vehicle 100.

[0108] Therefore, when switching from manual driving to automatic driving, adjustment unit 525 gradually adjusts the operation amount of steering input member 630A1 in manual driving toward the operation amount in automatic driving that is based on the vehicle momentum independent of the tire angle, as shown in the lower part of Fig. 36. Also, when switching from automatic driving to manual driving, adjustment unit 525 gradually adjusts the tire angle in automatic driving toward the tire angle corresponding to the operation amount of steering input member 630A1.

[0109] The flowchart in Fig. 37 shows the adjustment process by microcomputer 510 (adjustment unit 525) when the driving of vehicle 100 is switched from manual driving to automatic driving. The flowchart in Fig. 37 shows a routine that is executed as an interrupt at predetermined intervals during manual driving.

[0110] In step S821, microcomputer 510 determines whether or not a command to switch from manual driving to automatic driving has been issued. If a command to continue manual driving has been issued, microcomputer 510 proceeds to step S822, where it controls the tire angle of the steered wheels in accordance with the amount of operation of steering input member 630A1 operated by the driver.

[0111] On the other hand, if a command to switch from manual driving to automatic driving (automatic steering) has been set, microcomputer 510 proceeds to step S823, where it compares the target operation amount corresponding to the vehicle momentum set for automatic driving with the operation amount of steering input member 630A1 at the time of switching, and determines whether there is a discrepancy between the two. If there is no discrepancy (the discrepancy is equal to or less than a predetermined discrepancy), microcomputer 510 proceeds to step S824, where it stores the operation amount of steering input member 630A1.

[0112] On the other hand, if there is a deviation (if the deviation amount exceeds the predetermined deviation amount), the microcomputer 510 proceeds to step S825 and controls the steering reaction force actuator 630A2 so as to gradually bring the operation amount of the steering input member 630A1 closer to the target operation amount corresponding to the vehicle momentum set for automatic driving. The microcomputer 510 then proceeds from step S825 to step S826 and determines whether the operation amount of the steering input member 630A1 matches the target operation amount corresponding to the vehicle momentum set for automatic driving (whether the deviation amount is equal to or less than the predetermined deviation amount). When the operation amount of the steering input member 630A1 matches the target operation amount corresponding to the vehicle momentum set for automatic driving (if the deviation amount is equal to or less than the predetermined deviation amount), the microcomputer 510 proceeds to step S827 and transitions to automatic driving.

[0113] The adjustment of the operation amount in step S825 is performed, for example, by determining the adjusted target operation amount φk according to Equation 10. In Equation 10, θk is the target operation amount (following target value) according to the vehicle momentum set for autonomous driving, δk is the actual operation amount of the steering input member 630A1, and α is the convergence speed gain.

[0114] 38 is a block diagram showing the calculation process of the adjusted target manipulated variable φk according to Equation 10. A comparison unit 831 calculates the deviation between the actual manipulated variable δk and the target manipulated variable θk. An absolute value calculation unit 832 calculates the absolute value of the deviation between the actual manipulated variable δk and the target manipulated variable θk.

[0115] Meanwhile, a change amount calculation unit 833 calculates the amount of change per unit time of the target operation amount θk (the rate of change of the target operation amount θk). An absolute value calculation unit 834 acquires the amount of change per unit time of the target operation amount θk calculated by the change amount calculation unit 833, and calculates the absolute value of the amount of change. A gain unit 835 multiplies the absolute value of the amount of change of the target operation amount θk calculated by the absolute value calculation unit 834 by a convergence speed gain α that is adapted to the actual steering feel.

[0116] The comparator 836 subtracts the "absolute value of the change amount per unit time of the target manipulated variable θk" * α output by the gain unit 835 from the absolute value of the deviation amount between the actual manipulated variable δk and the target manipulated variable θk output by the absolute value calculator 832. The sign function unit 837 determines whether the deviation amount between the actual manipulated variable δk and the target manipulated variable θk output by the comparator 831 is positive or negative.

[0117] Then, a multiplication unit 838 assigns a sign to the output of the comparison unit 836 based on the output signal of the SIGN function unit 837. A correction unit 839 adds the output of the multiplication unit 838 to the target manipulated variable θk and outputs it as an adjusted target manipulated variable φk.

[0118] In addition, the delay unit 840 holds the previous value of the output of the comparison unit 836. The switching unit 841 acquires a flag for switching from manual driving to automatic driving, and stores the amount of deviation (output of the comparison unit 836) at the start of automatic driving. In other words, as shown in Fig. 39 , from the point in time when the flag for switching from manual driving to automatic driving is set, the amount of deviation between the target manipulated variable θk and the adjusted target manipulated variable φk is gradually reduced, and the adjusted target manipulated variable φk is gradually converged to the target manipulated variable θk.

[0119] The flowchart in Fig. 40 shows the adjustment process by microcomputer 510 (adjustment unit 525) when the driving of vehicle 100 is switched from automatic driving to manual driving. The flowchart in Fig. 40 shows a routine that is executed as an interrupt at predetermined intervals during automatic driving.

[0120] In step S851, the microcomputer 510 determines whether or not there is a command to switch from automatic driving to manual driving. If the command to switch from automatic driving to manual driving continues, the microcomputer 510 proceeds to step S852 and controls the operation amount of the steering input member 630A1 to become the target operation amount θk.

[0121] On the other hand, if a command to switch from automatic driving (automatic steering) to manual driving has been set, microcomputer 510 proceeds to step S853, where it determines whether the amount of operation of steering input member 630A1 has changed, in other words, whether steering input member 630A1 is moving. If the amount of operation of steering input member 630A1 has not changed, microcomputer 510 proceeds to step S854, where it stores the tire angle at that time.

[0122] On the other hand, if the amount of operation of steering input member 630A1 is changing, microcomputer 510 proceeds to step S855 and controls steering actuator 630B1 so as to gradually bring the tire angle closer to the target tire angle corresponding to the amount of operation of steering input member 630A1. Microcomputer 510 then proceeds from step S855 to step S856 and determines whether the tire angle has matched the target tire angle corresponding to the amount of operation of steering input member 630A1. Then, when the tire angle comes to match the target tire angle corresponding to the amount of operation of steering input member 630A1, microcomputer 510 proceeds to step S857 and transitions to manual driving.

[0123] The tire angle adjustment in step S855 is performed, for example, by determining the adjusted target tire angle δk according to Equation 11. For the sake of simplicity, it is assumed that the steering gear ratio is 1.0 and the target tire angle in manual driving is given as the operation amount of the steering input member 630A1 = target tire angle.

[0124] Fig. 41 is a block diagram showing the calculation process of the adjusted target tire angle δk in accordance with Equation 11. The calculation process of the adjusted target tire angle δk is a process of gradually bringing the actual tire angle closer to the target tire angle corresponding to the operation amount of the steering input member 630A1, and although the controlled object differs from that in the block diagram of Fig. 38 and the input / output signals of each block differ, the control process is similar to the calculation process of the adjusted target operation amount φk.

[0125] The comparison unit 831A calculates the amount of deviation between the actual tire angle δk and the operation amount θk (the target tire angle corresponding to the operation amount θk). The absolute value calculation unit 832A calculates the absolute value of the deviation calculated by the comparison unit 831A. Meanwhile, the change amount calculation unit 833A calculates the amount of change per unit time in the operation amount θk (driving operation amount) by the driver, in other words, the amount of change per unit time in the target tire angle corresponding to the operation amount θk.

[0126] An absolute value calculation unit 834A then calculates the absolute value of the amount of change calculated by the amount-of-change calculation unit 833A. A gain unit 835A multiplies the output of the absolute value calculation unit 834A by a convergence speed gain α that is adapted to the actual steering feel. A comparison unit 836A subtracts the output of the gain unit 835A from the output of the absolute value calculation unit 832A.

[0127] A sign function unit 837A determines whether the output of the comparison unit 831A is positive or negative. A multiplication unit 838A assigns a sign to the output of the comparison unit 836A based on the output signal of the sign function unit 837A. A correction unit 839A adds the output of the multiplication unit 838A to the operation amount θk, and outputs the result as the adjusted target tire angle δk.

[0128] In addition, the delay unit 840A holds the previous value of the output of the comparison unit 836A. The switching unit 841A acquires a flag for switching from automatic driving to manual driving, and stores the amount of deviation (output of the comparison unit 836A) at the start of manual driving (at the time of override). In other words, as shown in Fig. 42, from the point in time when the flag for switching from automatic driving to manual driving is set, the amount of deviation between the actual tire angle and the target tire angle corresponding to the operation amount θk is gradually reduced, and the adjusted tire angle is gradually converged to the target tire angle corresponding to the operation amount θk.

[0129] The technical ideas described in the above embodiments can be used in appropriate combinations as long as no contradictions arise. Furthermore, although the contents of the present invention have been specifically described with reference to preferred embodiments, it is obvious that a person skilled in the art can adopt various modified embodiments based on the basic technical ideas and teachings of the present invention.

[0130] For example, when a target operation amount is set without predicting the vehicle momentum, the steering device is not limited to a steer-by-wire steering device, but may be a steering device in which a steering input member such as a steering wheel is mechanically connected to steered wheels, and which is equipped with a steering actuator that assists the driver's steering operation and a variable gear ratio mechanism that can control the change in tire angle in response to the operation amount of the steering input member. Also, in the above embodiment, one microcomputer 510 performs operations from generating the target trajectory to controlling the steer-by-wire, but a control system in which these control functions are shared and performed by multiple microcomputers may be provided.

[0131] 100... Vehicle, 200... Vehicle control system, 300... External environment recognition unit, 400... Vehicle momentum detection unit, 500... Vehicle control device, 515... Steer-by-wire control unit, 521... Vehicle momentum acquisition unit, 522... Target tire angle calculation unit, 523... Driving operation amount acquisition unit, 524... Target operation amount calculation unit, 525... Adjustment unit, 600... Travel actuator unit

Claims

1. A vehicle control device provided in a vehicle equipped with a steering device including a steering input member that accepts steering operations by a driver, comprising: a vehicle momentum acquisition unit that acquires a vehicle momentum generated in the vehicle; and a target operation amount calculation unit that, when the steering device is automatically steered, calculates a target operation amount of the steering input member based on the vehicle momentum, independent of the tire angle of the vehicle, and outputs a signal of the target operation amount to the steering device.

2. A vehicle control device according to claim 1, wherein the target operation amount calculation unit calculates the target operation amount based on the vehicle momentum in a running state of the vehicle due to the automatic steering.

3. A vehicle control device according to claim 2, wherein the target operation amount calculation unit calculates the target operation amount based on the lateral acceleration of the vehicle, which is part of the vehicle momentum when the vehicle is traveling under automatic steering.

4. A vehicle control device according to claim 1, wherein the steering device is of a steer-by-wire type.

5. A vehicle control device according to claim 4, wherein the automatic steering causes the vehicle to travel along a target trajectory, the vehicle momentum acquisition unit estimates the future vehicle momentum from the target trajectory, and the target operation amount calculation unit calculates the target operation amount based on the future vehicle momentum.

6. A vehicle control device according to claim 5, wherein the target operation amount calculation unit calculates the target operation amount based on the lateral acceleration of the vehicle among the future vehicle momentum.

7. A vehicle control device according to claim 6, wherein the vehicle momentum acquisition unit makes the point on the target trajectory at which the future vehicle momentum is estimated farther away as the speed of the vehicle increases.

8. A vehicle control device according to claim 5, wherein the vehicle momentum acquisition unit estimates the future vehicle momentum at each of a plurality of different points on the target trajectory, and the target operation amount calculation unit calculates the target operation amount based on the plurality of future vehicle momentums.

9. A vehicle control device as set forth in claim 5, wherein the vehicle momentum acquisition unit estimates the future vehicle momentum at a point on the target trajectory that is a predetermined time ahead from the present, and variably sets the predetermined time based on information about a preceding vehicle traveling ahead of the vehicle or information about an obstacle present in front of the vehicle, and the target operation amount calculation unit calculates the target operation amount based on the future vehicle momentum at a point on the target trajectory that is the predetermined time ahead from the present.

10. A vehicle control device as claimed in claim 1, wherein the target operation amount calculation unit calculates the target operation amount in automatic steering for danger avoidance of the vehicle so that the operation amount is closer to a neutral position than in automatic steering that is not for danger avoidance, or so that the operation amount is fixed at a predetermined operation amount.

11. A vehicle control device as claimed in claim 1, further comprising: a driving operation amount acquisition unit that acquires a driving operation amount, which is information relating to the amount of operation of the steering input member by the driver of the vehicle; a target tire angle calculation unit that determines a target tire angle during manual steering by the driver from the information relating to the driving operation amount, and determines a target tire angle during automatic steering that causes the vehicle to travel along a target trajectory from the target trajectory; and an adjustment unit that adjusts the amount of deviation between the operation amount of the steering input member and the tire angle based on the target operation amount, the target tire angle, and the driving operation amount when switching between the automatic steering and the manual steering.

12. A vehicle control device according to claim 11, wherein the adjustment unit adjusts the deviation amount by outputting to the steering device a signal of an adjusted target operation amount, which is obtained by adjusting the target operation amount based on the amount of change per unit time in the target operation amount, when switching from the manual steering to the automatic steering.

13. A vehicle control device according to claim 11, wherein the adjustment unit adjusts the deviation amount by outputting to the steering device a signal of an adjusted target tire angle obtained by adjusting the target tire angle based on the amount of change per unit time in the operation amount based on the driving operation amount when switching from the automatic steering to the manual steering.

14. A vehicle control method executed by a control unit provided in a vehicle equipped with a steer-by-wire steering device including a steering input member that accepts steering operation by a driver, the vehicle control method controlling the amount of operation of the steering input member based on the lateral acceleration generated in the vehicle, independently of the tire angle of the vehicle, when the steering device is automatically steered.

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