Vehicle control device

Abstract

A vehicle control device according to the present invention, in one embodiment thereof: generates a reference trajectory on the basis of a travelable range in front of a vehicle and a predetermined constraint condition when the vehicle travels in the travelable range; on the basis of a physical quantity related to the motion of the vehicle, a physical quantity related to a vehicle driving operation performed by the driver, and reference information acquired on the basis of the reference trajectory, obtains an assist amount for bringing the vehicle travel caused by the driver close to the reference information; and outputs the assist amount to a travel actuator of the vehicle. Thus, vehicle comfort and safety when the driver operates the vehicle can be improved.

Description

Vehicle control device

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

[0002] The driving assistance device of Patent Document 1 includes a route target acquisition means for acquiring targets requested by the driver when setting a driving route, a route selection means for selecting a driving route in accordance with the acquired targets, a route information acquisition means for acquiring route information for the selected route, a target trajectory calculation means for calculating a target trajectory of the vehicle on the selected route, and a variable area calculation means for determining a variable area, which is the range within which the trajectory calculated based on the route information can be changed.

[0003] International Publication No. 2011 / 080830

[0004] However, when a driver operates a vehicle, if the driver's skill level is low, for example, the driver may not be able to take an appropriate course on a mountain road with a series of curves, which may result in large lateral acceleration due to sharp turns or make it difficult to maintain stability in the lane.

[0005] The present invention has been made in consideration of the current situation, and its purpose is to provide a vehicle control device that can improve the comfort and safety of a vehicle when a driver operates the vehicle.

[0006] In one aspect, the vehicle control device of the present invention includes a vehicle momentum acquisition unit that acquires physical quantities related to the motion of the vehicle, a driving operation quantity acquisition unit that acquires physical quantities related to the driving operation of the vehicle by the driver, a trajectory generation unit that generates a reference trajectory based on a driving range ahead of the vehicle and predetermined constraints when the vehicle drives within the driving range, and an assist unit that calculates an assist amount that brings the driving of the vehicle by the driver closer to the reference information based on the physical quantities related to the motion of the vehicle, the physical quantities related to the driving operation of the vehicle, and reference information acquired based on the reference trajectory, and outputs the assist amount to a driving actuator of the vehicle.

[0007] According to the present invention, it is possible to improve the comfort and safety of a vehicle when a driver operates the vehicle.

[0008] 1 is a block diagram showing a vehicle control system. FIG. 1 is a block diagram showing an assist control function of a vehicle control device. FIG. 1 is a block diagram showing a vehicle control device having a function for predicting a driving trajectory. FIG. 2 is a diagram illustrating an example of a drivable range and a reference trajectory on a curved road. FIG. 3 is a diagram showing a trajectory expressed by a difference equation. FIG. 4 is a diagram showing the closest point on the reference trajectory. FIG. 5 is a diagram showing how to determine a forward gaze point. FIG. 6 is a flowchart showing a first steering angle assist pattern. FIG. 7 is a diagram showing changes in the actual steering angle, etc. in the first steering angle assist pattern. FIG. 8 is a diagram showing differences in the steering angle assist direction depending on the position of the reference trajectory. FIG. 9 is a diagram showing differences in the steering angle assist direction depending on the position of the reference trajectory. FIG. 10 is a diagram showing changes in the trajectory due to assist control based on a predicted driving trajectory. FIG. 11 is a diagram showing changes in lateral acceleration due to assist control based on a predicted driving trajectory. FIG. 12 is a diagram showing a driving trajectory when changing lanes. FIG. 13 is a diagram showing lateral acceleration generated when changing lanes. FIG. 14 is a diagram showing a driving trajectory due to a reference trajectory, a predicted driving trajectory, and assist control. FIG. 15 is a flowchart showing a second steering angle assist pattern. FIG. 16 is a diagram showing changes in the actual steering angle, etc. in the second steering angle assist pattern. FIG. 17 is a diagram showing changes in the steering assist force, etc. in the second steering angle assist pattern. FIG. 18 is a flowchart showing a third steering angle assist pattern. FIG. 19 is a diagram showing changes in the curvature, steering angle, etc. in the third steering angle assist pattern. 1 is a diagram showing a trajectory according to a third steering angle assist pattern; FIG. 2 is a diagram showing a change in steering angle according to the third steering angle assist pattern; FIG. 3 is a flowchart showing a fourth steering angle assist pattern; FIG. 4 is a diagram showing trajectories outside and inside a reference trajectory; FIG. 5 is a diagram showing the steering angle when traveling outside the reference trajectory; FIG. 6 is a diagram showing the steering angle when traveling inside the reference trajectory; FIG. 7 is a flowchart showing a fifth steering angle assist pattern; FIG. 8 is a flowchart showing assist control according to trajectory direction; FIG. 9 is a flowchart showing assist control according to the presence or absence of an obstacle; FIG. 10 is a diagram explaining assist control when driver priority is given; FIG. 11 is a diagram explaining assist control when safety priority is given; FIG. 12 is a flowchart showing assist control according to grip force; FIG. 13 is a diagram showing a reference trajectory for bypassing an obstacle on a curved road; FIG. 14 is a diagram explaining assist control for suppressing saturation of tire force;1 is a diagram showing assist control for driving inside a driving range. FIG. 2 is a flowchart showing a first target vehicle speed creation pattern. FIG. 3 is a diagram illustrating a reference trajectory for a curved road. FIG. 4 is a diagram illustrating a steering angle and a target vehicle speed corresponding to the curvature of the reference trajectory. FIG. 5 is a diagram showing differences in driving trajectories on a curved road. FIG. 6 is a time chart showing differences in actual steering angle, vehicle speed, and lateral acceleration on a curved road. FIG. 7 is a diagram showing differences in driving trajectories at a curve exit. FIG. 8 is a time chart showing differences in lateral acceleration and vehicle speed at a curve exit. FIG. 9 is a flowchart showing a second target vehicle speed creation pattern. FIG. 10 is a time chart showing differences in deceleration amount before a curve. FIG. 11 is a flowchart showing a first braking / driving assist pattern. FIG. 12 is a flowchart showing a third braking / driving assist pattern. FIG. 13 is a flowchart showing a fourth braking / driving assist pattern. FIG. 14 is a flowchart showing a fifth braking / driving assist pattern. FIG. 15 is a flowchart showing assist control for notifying the driver. FIG. 16 is a flowchart showing assist control for controlling a steering reaction force. FIG. 17 is a diagram for explaining the action of assist control for controlling a steering reaction force.

[0009] An embodiment of a vehicle control device according to the present invention will now be described with reference to the drawings. Fig. 1 is a block diagram showing a vehicle driving system 100 mounted on a vehicle 10. The vehicle 10 is a four-wheeled automobile equipped with a pair of left and right front wheels 11, 12 and a pair of left and right rear wheels 13, 14.

[0010] The vehicle driving system 100 includes an external environment recognition unit 200, a vehicle momentum detection unit 300, a driving operation detection unit 400, a vehicle control device 500, and a driving actuator 600. Here, the vehicle driving system 100 is a system that electronically controls the driving actuator 600 to assist the driving operation by the driver.

[0011] The external environment recognition unit 200 is a device that recognizes external information of the vehicle 10, in other words, senses the surrounding conditions of the vehicle 10. The external environment recognition unit 200 includes, for example, a GPS (Global Positioning System) receiving unit 210, a map database 220, a road-to-vehicle communication device 230, a camera 240, a radar 250, and a LiDAR (Light Detection and Ranging, Laser Imaging Detection and Ranging) 260. The GPS receiving unit 210 and the map database 220 constitute a car navigation system.

[0012] Vehicle motion quantity detection unit 300 is a device for detecting physical quantities related to the motion of vehicle 10, and includes wheel speed sensor 310, acceleration sensor 320, etc. Wheel speed sensor 310 is a sensor that detects the rotational speed of each of wheels 11-14 of vehicle 10, and the detection result of wheel speed sensor 310 is used to estimate the speed of vehicle 10. In addition, acceleration sensor 320 detects the longitudinal acceleration, lateral acceleration, up and down acceleration, yaw rate, pitch rate, roll rate, lateral jerk, etc. of vehicle 10.

[0013] The driving operation amount detection unit 400 is a device for detecting physical quantities related to the driving operation of the vehicle 10 by the driver, specifically, the accelerator operation amount, the brake operation amount, and the steering operation amount. In detail, the driving operation amount detection unit 400 has an accelerator pedal sensor 410 that detects the accelerator operation amount, which is the operation amount of an accelerator pedal (not shown), a brake pedal sensor 420 that detects the brake operation amount, which is the operation amount of a brake pedal (not shown), and a steering operation amount sensor 430 that detects the steering operation amount (in other words, the steering operation amount), which is the operation amount of a steering wheel (not shown), which is a steering operation input member.

[0014] The traveling actuator 600 is an actuator for driving the vehicle 10, and includes a steering device 610, a drive device 620, and a braking device 630. The steering device 610 is a steer-by-wire system (SBW system) that steers the steered wheels (front wheels 11, 12) of the vehicle 10 that are mechanically separated from the steering wheel.

[0015] The steering device 610, which is a steer-by-wire system, includes a road wheel actuator that applies a steering force to the steered wheels and a steering reaction force actuator that applies a steering reaction force to the steering wheel. The road wheel actuator is electronically controlled in response to a signal indicating the amount of operation of the steering wheel, thereby controlling the steering angle of the steered wheels.

[0016] The steering device 610 is not limited to a steer-by-wire system, but may be, for example, an electric power steering device (EPS) in which the steering wheel and the steered wheels (specifically, the front wheels 11 and 12) of the vehicle 10 are mechanically connected, and which includes an electric motor (hereinafter also referred to as a power steering motor) that generates a steering assist force that assists the movement of a rack bar and pinion gear connected to the steering wheel.

[0017] The drive device 620 has an internal combustion engine, a motor, etc., and is a device in which the drive force applied to at least one of the front wheels 11, 12 and the rear wheels 13, 14 is electronically controlled in response to a signal indicating the amount of accelerator operation. The braking device 630 has a hydraulic brake capable of controlling the increase / decrease of the supplied hydraulic pressure, an electric caliper, a regeneratively operated motor, etc., and is a device in which the braking force applied to the wheels 11-14 is electronically controlled in response to a signal indicating the amount of brake operation.

[0018] The vehicle control device 500 is an electronic control device equipped with a microcomputer 500A that performs calculations based on acquired information and outputs the calculation results, and the microcomputer 500A functions as a driving assist controller that assists the driver in driving the vehicle 10. Figure 2 is a block diagram showing the assist control function of the vehicle control device 500 (microcomputer 500A). The vehicle control device 500 has the following functional units: a vehicle momentum acquisition unit 501, a driving operation amount acquisition unit 502, a trajectory generation unit 503, an index generation unit 504, and an assist unit 505.

[0019] The vehicle momentum acquisition unit 501 acquires physical quantities related to the motion of the vehicle 10. The vehicle momentum acquisition unit 501 acquires physical quantities related to the motion of the vehicle 10, such as vehicle speed, longitudinal acceleration, lateral acceleration, vertical acceleration, yaw rate, pitch rate, roll rate, and lateral jerk, from the vehicle momentum detection unit 300, specifically, the wheel speed sensor 310 and the acceleration sensor 320.

[0020] The driving operation amount acquisition unit 502 acquires physical amounts related to the driving operation of the vehicle 10 by the driver. The driving operation amount acquisition unit 502 acquires physical amounts related to the driving operation of the vehicle 10 by the driver, such as the accelerator operation amount, the brake operation amount, and the steering operation amount, from the driving operation amount detection unit 400, specifically, the accelerator pedal sensor 410, the brake pedal sensor 420, and the steering operation amount sensor 430.

[0021] The trajectory generation unit 503 generates a reference trajectory for assisting the driver in driving the vehicle 10 based on the drivable range ahead of the vehicle 10 and predetermined constraints when the vehicle 10 travels within the drivable range. As will be described in detail later, the drivable range is set as the area ahead of the vehicle 10 in the lane on which the vehicle 10 is traveling, for example, based on the recognition results of lane markers, etc. Then, the trajectory generation unit 503 uses the route, speed, and vehicle behavior of the vehicle 10 when traveling within the drivable range, as well as the road surface conditions within the drivable range and the travel trajectory of the preceding vehicle, as constraints, and generates a reference trajectory that passes through the drivable range while taking into account such constraints.

[0022] The index generating unit 504 acquires information about the reference trajectory generated by the trajectory generating unit 503, and acquires the position of the reference trajectory, the curvature of the reference trajectory, the differential value of the curvature of the reference trajectory, the target speed based on the curvature of the reference trajectory, the target longitudinal acceleration, the target longitudinal jerk, etc. as reference information for assist control that assists the driver in driving the vehicle 10. The assisting unit 505 calculates an assist amount that brings the driver's driving of the vehicle 10 closer to the reference information, based on the physical quantities related to the motion of the vehicle 10 acquired by the vehicle momentum acquiring unit 501, the physical quantities related to the driver's driving operation of the vehicle 10 acquired by the driving operation quantity acquiring unit 502, and the reference information acquired by the index generating unit 504 based on the reference trajectory.

[0023] The assist unit 505 then outputs the assist amount to the steering device 610, the drive device 620, and the brake device 630 that constitute the travel actuator 600, thereby assisting the driver in steering, accelerating, and braking operations. In other words, the assist unit 505 calculates the assist amount related to steering, the assist amount related to driving force, and the assist amount related to braking force, and outputs these assist amounts to the steering device 610, the drive device 620, and the brake device 630, thereby assisting the driver in operations to change the direction of travel of the vehicle 10, to accelerate the vehicle 10, and to decelerate the vehicle 10.

[0024] 1, the vehicle control device 500 has a function of predicting the future traveling trajectory and driving state of the vehicle 10, and can generate a reference trajectory by adding the prediction results. Furthermore, the vehicle control device 500 can calculate the amount of assist based on a comparison between reference information acquired based on the reference trajectory and the predicted traveling trajectory.

[0025] Fig. 3 is a block diagram showing a vehicle control device 500 to which a function for predicting the future traveling trajectory and driving state of the vehicle 10 has been added. In Fig. 3, the vehicle control device 500 includes a past trajectory information acquisition unit 506 and a vehicle state prediction unit 507 (in other words, a vehicle traveling trajectory prediction unit or a vehicle motion state prediction unit) in addition to the vehicle momentum acquisition unit 501, driving operation amount acquisition unit 502, trajectory generation unit 503, index generation unit 504, and assist unit 505 described above.

[0026] The past trajectory information acquisition unit 506 acquires information about the past traveling trajectory of the vehicle 10 from a car navigation system provided in the vehicle 10 or an external cloud (server). Then, the vehicle state prediction unit 507 predicts the future motion state and / or traveling trajectory of the vehicle 10 based on physical quantities related to the motion of the vehicle 10, such as speed, acceleration, yaw rate, and jerk, physical quantities related to the driving operation of the vehicle 10, such as steering operation amount (steering angle of steered wheels), and the past traveling trajectory of the vehicle 10. Note that, hereinafter, the traveling trajectory predicted by the vehicle state prediction unit 507 is also referred to as a predicted traveling trajectory.

[0027] Here, the trajectory generation unit 503 acquires information on the motion state and traveling trajectory predicted by the vehicle state prediction unit 507, and generates a reference trajectory by adding the motion state and / or traveling trajectory predicted by the vehicle state prediction unit 507 to the travelable range ahead of the vehicle 10 and predetermined constraints when the vehicle 10 travels within the travelable range. Also, the index generation unit 504 acquires information on the motion state and traveling trajectory predicted by the vehicle state prediction unit 507 in addition to the information on the reference trajectory, and acquires reference information. Then, the assist unit 505 calculates, for example, an assist amount that brings the reference trajectory closer to the predicted traveling trajectory.

[0028] The process of generating a reference trajectory in the trajectory generation unit 503 will be described in detail below. The vehicle control device 500 sets a driving range ahead of the vehicle 10 based on external environment information of the vehicle 10 recognized by the external environment recognition unit 200. For example, the vehicle control device 500 sets the driving range as the area between left and right lane markers (white lines) on the road, or between left and right road edges on the road. In other words, the vehicle control device 500 sets the area within the lane recognized from lane markers or the like as the basic driving range.

[0029] Furthermore, if any object is present in the lane, the vehicle control device 500 can set the driving range as an area excluding the object. Examples of the object include a stopped vehicle, a preceding vehicle, an oncoming vehicle, a fallen object, an installed object, a tree, a utility pole, a pedestrian, a sign, etc.

[0030] Furthermore, the vehicle control device 500 is alert to vehicles, pedestrians, and the like jumping out from behind an object and sets the shadow of the object as a collision risk area, and can set the area obtained by excluding the collision risk area from the basic drivable range as the drivable range. Furthermore, if there is an area ahead of the vehicle 10 that cannot be recognized, the area obtained by excluding the unrecognized area from the basic drivable range can be set as the drivable range.

[0031] Then, the trajectory generating unit 503 generates, as a reference trajectory, for example, a trajectory that passes through the travelable range and that minimizes the absolute value of the lateral acceleration and / or lateral jerk of the vehicle 10. In other words, the trajectory generating unit 503 can generate a reference trajectory based on a constraint condition that minimizes the absolute value of the lateral acceleration within the travelable range (in other words, suppresses the generation of lateral acceleration as much as possible) and a constraint condition that minimizes the absolute value of the lateral jerk within the travelable range (in other words, suppresses the generation of lateral jerk as much as possible).

[0032] Furthermore, the trajectory generating unit 503 can generate a reference trajectory so as not to deviate from constraints such as the maximum speed, minimum speed, maximum absolute value of lateral acceleration, and maximum absolute value of lateral jerk for each predetermined point. For example, the maximum speed is the legal maximum speed, and the minimum speed is the legal minimum speed or a predetermined minimum speed for not disrupting traffic flow. For example, the maximum absolute value of lateral acceleration is a value set based on the ride comfort of the vehicle 10 and the lateral acceleration allowable for autonomous driving, and the maximum absolute value of the lateral jerk of the vehicle 10 is a value set based on the ride comfort of the vehicle 10, etc.

[0033] Furthermore, if there are objects such as other vehicles, pedestrians, obstacles, fallen objects, or signs within the drivable area, the trajectory generating unit 503 can generate a reference trajectory using the objects as constraints. That is, the trajectory generating unit 503 can determine a trajectory along which the vehicle 10 travels while avoiding the objects as a reference trajectory, and can further generate a reference trajectory that minimizes the absolute value of the lateral acceleration and / or lateral jerk while avoiding the objects.

[0034] Furthermore, the trajectory generation unit 503 can acquire road surface information such as the road friction coefficient μ, road cant, road slope, road undulation, road unevenness, speed bumps, and potholes as constraint conditions, and set a reference trajectory using these constraint conditions. In particular, the trajectory generation unit 503 can set a reference trajectory that avoids areas with a low road friction coefficient μ and road unevenness. Furthermore, when adopting a trajectory that passes through areas with a low road friction coefficient μ or road unevenness, the trajectory generation unit 503 can set the vehicle speed on the reference trajectory so as to decelerate and pass through areas with a low road friction coefficient μ or road unevenness.

[0035] 4 is a diagram illustrating an example of a driving range and a reference trajectory on a curved road. In FIG. 4, the shaded area is the driving range. In FIG. 4, the driving range of the vehicle 10 is set as the area within the lane excluding the area of ​​the object OB indicated by the triangle in the figure and avoiding oncoming vehicles 180.

[0036] Then, the trajectory generating unit 503 generates a reference trajectory within the driving range that minimizes the absolute values ​​of, for example, lateral acceleration and lateral jerk. In other words, the trajectory generating unit 503 appropriately selects, as the reference trajectory, a trajectory that can maintain safety based on the object information within the driving range and that provides a comfortable ride by minimizing the generation of lateral acceleration and lateral jerk.

[0037] Here, as an example of a trajectory design method, an example in which trajectory points are expressed by a difference equation will be described. The expression of trajectory points by a difference equation is, for example, as shown in Equation 1. Figure 5 shows that in the difference equation expression, trajectory point x[n+1] at time n+1 can be obtained by adding a time change to trajectory point x[n] at time n.

[0038]

[0039] Then, the trajectory generation unit 503 can generate a reference trajectory of the vehicle 10 by determining the input sequence u[0], u[1], ..., u[N-1]. Here, the trajectory generation unit 503 determines the input sequence u[0], u[1], ..., u[N-1] that minimizes the evaluation function J(x, u) shown in Equation 2. The above evaluation function J(x, u) is designed so that the objective is achieved when it is minimized.

[0040] For example, when the traveling of the preceding vehicle is taken into consideration (in other words, when the trajectory of the preceding vehicle is used as a constraint), the evaluation function J(x, u) is designed to have a smaller value as the trajectory passes closer to the position of the preceding vehicle. Note that the microcomputer 500A can appropriately select and use a method for determining the input sequence u[0], u[1], ..., u[N-1] from known methods such as the steepest descent method, conjugate gradient method, Newton's method, and quasi-Newton's method.

[0041] The assist unit 505 determines the amount of assistance to bring the driving of the vehicle 10 by the driver closer to the reference information based on the reference trajectory, and the reference point on the reference trajectory can be determined by using the closest point on the reference trajectory as the reference point, or by using a predetermined point on the reference trajectory ahead in the direction of travel of the vehicle 10 as the reference point. Fig. 6 shows a case where the closest point on the reference trajectory is used as the reference point, and in this case, the assist unit 505 determines the amount of assistance by referring to the closest point, which is the point on the reference trajectory that is closest to the vehicle 10.

[0042] Furthermore, when a predetermined point on a reference trajectory ahead of the vehicle 10 in the traveling direction is used as the reference point, the assist unit 505 determines the amount of assistance by referring to a forward gaze point on the reference trajectory that is a forward gaze distance Lp away from the vehicle 10. Here, the forward gaze distance Lp can be the total distance traveled along the reference trajectory or the distance in the traveling direction of the vehicle 10. Furthermore, the forward gaze distance Lp can be a fixed value, or can be set as Lp = Tp * V based on the vehicle speed V and the forward gaze time Tp, which is a constant value. Figure 7 shows the reference point when the forward gaze distance Lp is set as the distance in the traveling direction of the vehicle 10 and when the forward gaze distance Lp is set as Lp = Tp * V.

[0043] Among the assist controls performed by the vehicle control device 500, the assist control of the steering angle (steered amount) will be described in detail below. As the pattern of the assist control of the steering angle in the vehicle control device 500, for example, any of the following five types of steering angle assist patterns can be adopted. First steering angle assist pattern: The steering angle is assisted according to the difference between the position of the reference trajectory and the position of the predicted traveling trajectory. Second steering angle assist pattern: The steering angle is assisted according to the curvature of the reference trajectory. Third steering angle assist pattern: The steering angle is assisted according to the differential value of the curvature of the reference trajectory. Fourth steering angle assist pattern: The steering angle is assisted according to the difference between the curvature of the reference trajectory and the curvature of the predicted traveling trajectory. Fifth steering angle assist pattern: The steering angle is assisted according to the difference between the differential value of the curvature of the reference trajectory and the differential value of the curvature of the predicted traveling trajectory.

[0044] Here, the first steering angle assist pattern, the fourth steering angle assist pattern, and the fifth steering angle assist pattern use a predicted driving trajectory, and are therefore steering angle assist patterns that can be implemented by the vehicle control device 500 shown in Fig. 3. On the other hand, the second steering angle assist pattern and the third steering angle assist pattern do not use a predicted driving trajectory, and are therefore steering angle assist patterns that can be implemented by the vehicle control device 500 shown in Fig. 2.

[0045] The processing content for each steering angle assist pattern will be described in detail below. "First steering angle assist pattern" The flowchart in Figure 8 shows the control process of the first steering angle assist pattern, which assists the steering angle in accordance with the difference between the position of a reference trajectory as reference information and the position of a predicted traveling trajectory. In step S701, the vehicle control device 500 generates a reference trajectory using the current position of the vehicle 10 as a starting point.

[0046] In step S701, the vehicle control device 500 can generate a reference trajectory that leads to the predicted travel trajectory or a part of it, instead of generating the reference trajectory starting from the current position of the vehicle 10, and can also generate a reference trajectory that leads to the predicted vehicle motion state (yaw rate, yaw rate derivative, acceleration, jerk) (in other words, so that the vehicle motion state changes continuously). In other words, the trajectory generation unit 503 can generate a reference trajectory by adding the predicted value of the predicted travel trajectory or the vehicle motion state to the driving range and constraint conditions.

[0047] In step S702, the vehicle control device 500 determines a predicted travel trajectory of the vehicle 10. Next, in step S703, the vehicle control device 500 determines whether the driver has performed a steering operation, that is, whether the steering wheel has been turned. If the driver has not performed a steering operation, the vehicle control device 500 returns to step S701 without performing assist control. On the other hand, if the driver has performed a steering operation, the vehicle control device 500 proceeds to step S704.

[0048] In step S704, the vehicle control device 500 determines the amount of lateral positional deviation between the reference trajectory and the predicted travel trajectory. Thereafter, if the steering device 610 is a steer-by-wire system, the vehicle control device 500 proceeds to step S705, and if the steering device 610 is an electric power steering device, the vehicle control device 500 proceeds to step S706.

[0049] In step S705, the vehicle control device 500 reflects the assist amount (steering angle correction amount) corresponding to the lateral positional deviation amount between the reference trajectory and the predicted traveling trajectory calculated in step S704 in the actual steering angle of the steered wheels (front wheels 11, 12) in the steer-by-wire system. That is, in step S705, the vehicle control device 500 corrects the actual steering angle in response to the operation of the steering wheel by the driver based on the lateral positional deviation amount between the reference trajectory and the predicted traveling trajectory so as to bring the predicted traveling trajectory closer to the reference trajectory.

[0050] Meanwhile, in step S706, vehicle control device 500 reflects an assist amount (steering assist force correction amount) corresponding to the lateral positional deviation amount between the reference trajectory and the predicted traveling trajectory calculated in step S704 in the steering assist force generated by the power steering motor of the electric power steering device. In other words, in step S706, if the driver tends to steer excessively in response to changes in the steering angle along the reference trajectory, vehicle control device 500 reduces the steering assist force to make the steering wheel operation heavier, and conversely, if the driver tends to steer insufficiently in response to changes in the steering angle along the reference trajectory, it increases the steering assist force to make the steering wheel operation lighter.

[0051] 9 is a diagram showing the traveling trajectory, actual steering angle, and steering operation torque when the control process shown in the flowchart of FIG. 8 is applied to a steer-by-wire system. The vehicle control device 500 periodically updates the reference trajectory using the current position of the vehicle 10 as a starting point, and compares the reference trajectory with the predicted traveling trajectory. The vehicle control device 500 then corrects the actual steering angle in a direction that brings the predicted traveling trajectory closer to the reference trajectory.

[0052] Here, the vehicle control device 500 corrects the actual steering angle in a direction that brings the predicted traveling trajectory closer to the reference trajectory, but the steering reaction torque applied to the steering wheel in the steer-by-wire system is maintained at the same normal value as when assist control is not implemented. In other words, in the assist control for the steer-by-wire system, the vehicle control device 500 calculates the assist amount for steering the front wheels 11, 12 without rotating the steering wheel. Therefore, because the steering operation torque by the driver does not change due to the assist control, it is possible to guide the vehicle 10 to traveling on a traveling trajectory that is close to the reference trajectory while preventing the driver from feeling uncomfortable.

[0053] 10 and 11 are diagrams for explaining the difference in the direction of correction of the actual steering angle depending on the positional relationship between the predicted traveling trajectory and the reference trajectory. Fig. 10 shows the case where the reference trajectory is on the same side as the steering direction by the driver and ahead of the steering direction. In this case, the vehicle control device 500 calculates the assist amount so as to increase the actual steering angle (the steering amount of the steered wheels). In other words, when the reference trajectory and the predicted traveling trajectory turn in the same direction, if the reference trajectory is located on the inner side of the turn than the predicted traveling trajectory, the vehicle control device 500 increases the actual steering angle so that the vehicle 10 passes more on the inner side of the turn, bringing the traveling trajectory of the vehicle 10 closer to the reference trajectory.

[0054] 11 shows a case where the reference trajectory is on the same side as the steering direction by the driver and is ahead of the steering direction, and in this case the vehicle control device 500 calculates the assist amount so as to reduce or maintain the actual steering angle (the amount of steering of the steered wheels). In other words, when the reference trajectory and the predicted traveling trajectory are paths that turn in the same direction, if the reference trajectory is located on the outer side of the turn than the predicted traveling trajectory, the vehicle control device 500 reduces the actual steering angle so that the vehicle 10 passes closer to the outer side of the turn, or maintains the actual steering angle to prevent the vehicle 10 from turning to the inner side of the turn, thereby bringing the traveling trajectory of the vehicle 10 closer to the reference trajectory.

[0055] 12 and 13 are diagrams for explaining the effect of implementing control (first steering angle assist pattern) that brings the predicted travel trajectory of the vehicle 10 closer to the reference trajectory on a curved road. Fig. 12 shows the reference trajectory on a curved road, the travel trajectory without assist control, and the travel trajectory with assist control. Fig. 13 shows the lateral acceleration that occurs when traveling on a curved road without assist control and when traveling with assist control.

[0056] When the reference trajectory is set so as to minimize the occurrence of lateral acceleration and lateral jerk within the driving range, the reference trajectory is set, for example, as an out-in-out driving trajectory. Here, if assist control is implemented to bring the trajectory closer to the reference trajectory when the driver performs a steering operation to drive on a trajectory that maintains the center of the lane, the trajectory on which the vehicle 10 drives approaches the out-in-out trajectory, thereby suppressing the lateral acceleration that occurs during cornering and improving the ride comfort of the vehicle 10.

[0057] 14 and 15 are diagrams for explaining the effect of implementing control to bring the predicted travel trajectory of the vehicle 10 closer to the reference trajectory when the vehicle 10 changes lanes on a straight road such as a highway. Fig. 14 shows the reference trajectory, the travel trajectory without assist control, and the travel trajectory with assist control when the vehicle 10 changes lanes on a straight road. Fig. 15 shows the lateral acceleration that occurs when changing lanes without assist control and when changing lanes with assist control.

[0058] By setting the reference trajectory so as to minimize the lateral acceleration and lateral jerk that occur when changing lanes, the assist control reduces the steering speed, providing a sense of security to the occupants of the vehicle 10. In contrast, if the driver's skill level is low, the steering speed for changing lanes will be high, resulting in the generation of large lateral acceleration and lateral jerk. In other words, if the assist control is implemented so that the predicted traveling trajectory of the vehicle 10 approaches the reference trajectory, the steering speed is reduced and the generation of lateral acceleration and lateral jerk is suppressed, thereby enabling a lane change that provides a sense of security to the occupants of the vehicle 10.

[0059] 16 shows a process for changing the steering timing depending on the traveling location. Fig. 16 illustrates a case where the steering timing of the reference trajectory is earlier than that of the predicted traveling trajectory. In this case, the assist unit 505 can perform assist control to bring the timing of the vehicle 10 starting to turn closer to the reference trajectory, even if the predicted traveling trajectory does not involve steering.

[0060] "Second Steering Angle Assist Pattern" The flowchart in Figure 17 shows the control process of the second steering angle assist pattern that assists the steering angle depending on the magnitude of the curvature of the reference trajectory. The vehicle control device 500 generates a reference trajectory in step S711. In generating the reference trajectory in step S711, it is not necessary to use the position of the vehicle 10 as the starting point, and the vehicle control device 500 can generate an ideal driving trajectory as the reference trajectory regardless of the actual driving position of the vehicle 10.

[0061] Next, in step S712, the vehicle control device 500 obtains the curvature of the reference trajectory as reference information, and further calculates the steering angle when tracing the reference trajectory. The vehicle control device 500 can convert the curvature of the reference trajectory into a steering angle using Equation 3. In Equation 3, δ is the steering angle, κ is the curvature, V is the vehicle speed, A is the stability factor, and L is the wheelbase.

[0062] Then, in step S713, the vehicle control device 500 determines whether the driver has performed a steering operation, that is, whether the steering wheel has been turned. If the driver has not performed a steering operation, the vehicle control device 500 returns to step S711 without performing assist control. On the other hand, if the driver has performed a steering operation, the vehicle control device 500 proceeds to step S714.

[0063] In step S714, the vehicle control device 500 calculates the amount of steering assist based on the curvature of the reference trajectory calculated in step S713 or the steering angle when tracing the reference trajectory. Then, the vehicle control device 500 proceeds to step S715 if the steering device 610 is a steer-by-wire system, or proceeds to step S716 if the steering device 610 is an electric power steering device.

[0064] In step S715, the vehicle control device 500 reflects the assist amount (steering angle correction amount) calculated in step S714 in the actual steering angle of the steered wheels (front wheels 11, 12) in the steer-by-wire system. In other words, while the driver is steering, the vehicle control device 500 changes the actual steering angle in the steer-by-wire system in accordance with the curvature (steering angle) of the reference trajectory.

[0065] Meanwhile, in step S716, the vehicle control device 500 reflects the assist amount (steering assist force correction amount) calculated in step S714 in the steering assist force generated by the power steering motor of the electric power steering device. In other words, while the driver is steering, the vehicle control device 500 changes the steering assist force of the electric power steering device in accordance with the curvature (steering angle) of the reference trajectory.

[0066] Fig. 18 is a diagram showing changes in each trajectory, curvature (steering angle), actual steering angle, and steering operation torque according to the longitudinal distance when the control process of the second steering angle assist pattern shown in the flowchart of Fig. 17 is applied to a steer-by-wire system. Fig. 18 shows a case where the road on which the vehicle 10 is traveling turns to the left at an obtuse angle, the reference trajectory is generated so that the turning starts before the corner of the road, and the steering operation by the driver is delayed with respect to the reference trajectory.

[0067] To cope with such a delay in the steering operation, the vehicle control device 500 increases the actual steering angle by an amount corresponding to the difference between the actual steering angle at the start of the steering operation and the curvature (steering angle) of the reference trajectory while the curvature (steering angle) of the reference trajectory is larger than the actual steering angle at the start of the steering operation. After that, when the curvature (steering angle) of the reference trajectory becomes smaller than the actual steering angle at the start of the steering operation, the vehicle control device 500 decreases the actual steering angle by an amount corresponding to the difference between the actual steering angle at the start of the steering operation and the curvature (steering angle) of the reference trajectory.

[0068] Here, the vehicle control device 500 maintains the steering reaction torque at the normal value, the same as when assist control is not implemented, and the steering operation torque and steering wheel operation angle by the driver are not affected by assist control. Therefore, it is possible to travel along a trajectory with a curvature close to that of the reference trajectory while suppressing the driver from feeling any discomfort. Furthermore, assist control that brings the curvature of the trajectory actually traveled by the vehicle 10 closer to the curvature of the reference trajectory does not provide assistance to reduce the positional deviation between the reference trajectory and the trajectory of the vehicle 10. Therefore, as shown in FIG. 18 , even if the trajectory of the vehicle 10 deviates from the reference trajectory, unnatural vehicle behavior due to the correction of the positional deviation does not occur.

[0069] Fig. 19 is a diagram showing changes in each trajectory, curvature (steering angle), steering operation torque, and steering assist force according to the longitudinal distance when the control process of the second steering angle assist pattern shown in the flowchart of Fig. 17 is applied to an electric power steering device. Note that Fig. 19 is different from Fig. 18 in that the road shape, reference trajectory, and steering operation by the driver are the same, but the steering device 610 is an electric power steering device.

[0070] In the case of an electric power steering device, an increase in the steering assist force increases the steering angle, and conversely, a decrease in the steering assist force decreases the steering angle. Therefore, the vehicle control device 500 performs an increase correction of the steering assist force in a situation where an increase correction of the steering angle is performed in the assist control of the steer-by-wire system shown in Fig. 18, and performs a decrease correction of the steering assist force in a situation where a decrease correction of the steering angle is performed in the assist control of the steer-by-wire system shown in Fig. 18. This makes it possible to travel along a trajectory with a curvature close to that of the reference trajectory, with almost no effect on the steering operation torque by the driver.

[0071] "Third Steering Angle Assist Pattern" The flowchart in Figure 20 shows the control process of the third steering angle assist pattern that assists the steering angle in accordance with the magnitude of the differential value (time differential value) of the curvature of the reference trajectory. The vehicle control device 500 generates a reference trajectory in step S721. Next, in step S722, the vehicle control device 500 calculates the curvature of the reference trajectory, and further calculates the steering angle when tracing the reference trajectory based on the above-mentioned equation 3. Furthermore, in step S723, the vehicle control device 500 calculates, as reference information, the differential value of the curvature of the reference trajectory calculated in step S722 and the steering angle speed, which is the differential value (time differential value) of the steering angle when tracing the reference trajectory.

[0072] Then, in step S724, the vehicle control device 500 determines whether the driver has performed a steering operation. If the driver has not performed a steering operation, the vehicle control device 500 returns to step S721 without performing assist control. On the other hand, if the driver has performed a steering operation, the vehicle control device 500 proceeds to step S725.

[0073] In step S725, the vehicle control device 500 calculates the amount of steering assist based on the differential value of the curvature of the reference trajectory calculated in step S713 or the steering angular velocity when tracing the reference trajectory. Then, the vehicle control device 500 proceeds to step S726 if the steering device 610 is a steer-by-wire system, or proceeds to step S727 if the steering device 610 is an electric power steering device.

[0074] In step S726, the vehicle control device 500 reflects the assist amount (steering angle correction amount) determined in step S725 in the actual steering angle of the steered wheels (front wheels 11, 12) in the steer-by-wire system. Meanwhile, in step S727, the vehicle control device 500 reflects the assist amount (steering assist force correction amount) determined in step S725 in the steering assist force generated by the power steering motor of the electric power steering device.

[0075] Fig. 21 is a diagram showing the changes in each trajectory, curvature (steering angle), curvature differential (steering angular velocity), and actual steering angle according to the distance in the longitudinal direction when the control process of the third steering angle assist pattern shown in the flowchart of Fig. 20 is applied to a steer-by-wire system. Note that Fig. 21 uses the same road shape and reference trajectory as Fig. 18, and also the same steering operation by the driver.

[0076] Here, while the driver is steering, the vehicle control device 500 changes the actual steering angle in the steer-by-wire system in accordance with the differential value of the curvature (steering angle) of the reference trajectory. In other words, while the driver is steering, during a period when the differential value of the curvature of the reference trajectory is negative and the curvature (steering angle) of the reference trajectory is decreasing, the vehicle control device 500 reduces the actual steering angle, thereby minimizing the change in curvature of the trajectory on which the vehicle 10 travels. In this application, a decrease in the steering angle refers to a change in the steering angle in a direction approaching the neutral position (straight-ahead position), and an increase in the steering angle refers to a change in the steering angle in a direction away from the neutral position.

[0077] Furthermore, during a period when the driver is steering and the differential value of the curvature of the reference trajectory is positive and the curvature (steering angle) of the reference trajectory is increasing, the vehicle control device 500 increases the actual steering angle to speed up the turning response. Here, the vehicle control device 500 maintains the steering reaction torque at the normal value, the same as when assist control is not being implemented, and the steering operation torque and steering wheel operation angle by the driver are not affected by assist control. Therefore, it is possible to prevent the driver from feeling uncomfortable and to make the vehicle 10 travel on a trajectory whose curvature changes close to the differential value of the curvature of the reference trajectory.

[0078] 22 and 23 are diagrams for explaining the effects of the control process of the third steering angle assist pattern. If the driver's skill level is low, for example, the driver will not be able to take an appropriate course on a curve, and will make many corrective steering movements, as shown by "without assist control" in Fig. 22 and 23. In contrast, if assist control is implemented to assist the steering angle according to the differential value of the curvature of the reference trajectory, even a driver with a low skill level can stabilize the actual steering angle during cornering, providing a sense of security and stability on curves.

[0079] "Fourth Steering Angle Assist Pattern" The flowchart in Figure 24 shows the control process of the fourth steering angle assist pattern that assists the steering angle in accordance with the difference between the curvature of the reference trajectory and the curvature of the predicted traveling trajectory. In step S731, the vehicle control device 500 generates a reference trajectory. Next, in step S732, the vehicle control device 500 calculates the curvature (steering angle) of the reference trajectory.

[0080] In step S733, the vehicle control device 500 determines a predicted travel trajectory of the vehicle 10. Then, in step S734, the vehicle control device 500 calculates the curvature (steering angle) of the predicted travel trajectory.

[0081] Next, in step S735, the vehicle control device 500 determines whether the driver has performed a steering operation. If the driver has not performed a steering operation, the vehicle control device 500 returns to step S731 without performing assist control. On the other hand, if the driver has performed a steering operation, the vehicle control device 500 proceeds to step S736.

[0082] In step S736, the vehicle control device 500 calculates an assist amount for the steering angle based on the difference between the curvature (steering angle) of the reference trajectory and the curvature (steering angle) of the predicted traveling trajectory. Then, if the steering device 610 is a steer-by-wire system, the vehicle control device 500 proceeds to step S737, and if the steering device 610 is an electric power steering device, the vehicle control device 500 proceeds to step S738.

[0083] In step S737, the vehicle control device 500 reflects the assist amount (steering angle correction amount) calculated in step S736 in the actual steering angle of the steered wheels (front wheels 11, 12) in the steer-by-wire system. In other words, when the steering device 610 is a steer-by-wire system, the vehicle control device 500 corrects the actual steering angle by a correction amount according to the difference between the curvature of the reference trajectory and the curvature of the predicted traveling trajectory, thereby bringing the curvature of the predicted traveling trajectory closer to the curvature of the reference trajectory.

[0084] Furthermore, in step S738, the vehicle control device 500 reflects the assist amount (steering assist force correction amount) calculated in step S736 in the steering assist force of the electric power steering device. That is, when the steering device 610 is an electric power steering device, the vehicle control device 500 corrects the steering assist force by a correction amount corresponding to the difference between the curvature of the reference trajectory and the curvature of the predicted trajectory, thereby bringing the curvature of the predicted trajectory closer to the curvature of the reference trajectory. Specifically, the vehicle control device 500 increases the steering assist force when the curvature of the reference trajectory is greater than that of the predicted trajectory, and conversely decreases the steering assist force when the curvature of the reference trajectory is smaller than that of the predicted trajectory.

[0085] In addition, in the assist control (fourth steering angle assist pattern) that brings the curvature of the predicted traveling trajectory closer to the curvature of the reference trajectory, the vehicle control device 500 can perform assist control related to steering (hereinafter also referred to as offset traveling assist control) so that the vehicle 10 travels along a trajectory that runs parallel to the reference trajectory and is inside or outside the reference trajectory. Below, an overview of the offset traveling assist control will be given with reference to Figures 25 to 27.

[0086] Figure 25 shows a travel path A that runs parallel to the reference path and outside the reference path on a curved road, and a travel path B that runs parallel to the reference path and outside the reference path. Figure 26 illustrates an example of a change in the actual steering angle when the vehicle 10 runs along the travel path A that is outside the reference path shown in Figure 25, and a change in the actual steering angle when the vehicle 10 runs along the reference path. When the vehicle 10 runs along the travel path A, the vehicle control device 500 can assist the vehicle 10 in running along the travel path A that is outside the reference path by delaying the steering timing and increasing the actual steering angle compared to when the vehicle 10 runs along the reference path.

[0087] 27 illustrates an example of a change in the actual steering angle when the vehicle 10 travels along a travel path B that is more inward than the reference path shown in FIG. 25 , and a change in the actual steering angle when the vehicle 10 travels along the reference path. When the vehicle 10 travels along the travel path B, the vehicle control device 500 can assist the vehicle 10 in traveling along the travel path B that is more inward than the reference path by making the steering timing earlier and reducing the actual steering angle compared to when the vehicle 10 travels along the reference path. In other words, the vehicle control device 500 can calculate an assist amount related to the steering angle so that the timing of intervention of the steering angle of the vehicle 10 (the amount of steering of the steered wheels) differs between when the vehicle 10 is traveling on the inside of a turn and when it is traveling on the outside of a turn with respect to the reference path.

[0088] "Fifth Steering Angle Assist Pattern" The flowchart in Figure 28 shows the control process of a fifth steering angle assist pattern that assists the steering angle in accordance with the difference between the differential value of the curvature of the reference trajectory and the differential value of the curvature of the predicted traveling trajectory. In step S741, the vehicle control device 500 generates a reference trajectory. Next, in step S742, the vehicle control device 500 calculates the curvature (steering angle) of the reference trajectory. Then, in step S743, the vehicle control device 500 calculates the differential value of the curvature of the reference trajectory (steering angular velocity).

[0089] Next, in step S744, the vehicle control device 500 determines a predicted travel trajectory of the vehicle 10. Then, in step S745, the vehicle control device 500 calculates the curvature (steering angle) of the predicted travel trajectory. Furthermore, in step S746, the vehicle control device 500 determines a differential value (steering angular velocity) of the curvature of the predicted travel trajectory.

[0090] Next, in step S747, the vehicle control device 500 determines whether the driver has performed a steering operation. If the driver has not performed a steering operation, the vehicle control device 500 returns to step S741 without performing assist control. On the other hand, if the driver has performed a steering operation, the vehicle control device 500 proceeds to step S748.

[0091] In step S748, the vehicle control device 500 calculates an assist amount for the steering angle based on the difference between the differential value of the curvature (steering angle) of the reference trajectory and the differential value of the curvature (steering angle) of the predicted traveling trajectory. Then, the vehicle control device 500 proceeds to step S749 if the steering device 610 is a steer-by-wire system, and proceeds to step S750 if the steering device 610 is an electric power steering device.

[0092] In step S749, the vehicle control device 500 reflects the assist amount (steering angle correction amount) calculated in step S748 in the actual steering angle of the steered wheels (front wheels 11, 12) in the steer-by-wire system. In other words, when the steering device 610 is a steer-by-wire system, the vehicle control device 500 corrects the actual steering angle by a correction amount according to the difference between the differential value of the curvature (steering angle) of the reference trajectory and the differential value of the curvature (steering angle) of the predicted traveling trajectory, thereby making the differential value of the curvature (steering angle) of the reference trajectory approach the differential value of the curvature (steering angle) of the predicted traveling trajectory.

[0093] Furthermore, in step S750, the vehicle control device 500 reflects the assist amount (steering assist force correction amount) calculated in step S748 in the steering assist force of the electric power steering device. That is, when the steering device 610 is an electric power steering device, the vehicle control device 500 corrects the steering assist force by a correction amount corresponding to the difference between the differential value of the curvature (steering angle) of the reference trajectory and the differential value of the curvature (steering angle) of the predicted trajectory, thereby bringing the curvature (steering angle) of the predicted trajectory closer to the differential value of the curvature (steering angle) of the reference trajectory. Specifically, the vehicle control device 500 increases the steering assist force when the differential value of the curvature (steering angle) of the reference trajectory is greater than the differential value of the curvature (steering angle) of the predicted trajectory, and conversely, decreases the steering assist force when the differential value of the curvature (steering angle) of the reference trajectory is smaller than the differential value of the curvature (steering angle) of the predicted trajectory.

[0094] In the following, a control process derived from the above-mentioned first steering angle assist pattern, that is, a steering angle assist pattern that assists the steering angle in accordance with the difference between the position of the reference trajectory and the position of the predicted traveling trajectory, will be described. "First Derivation of First Steering Angle Assist Pattern" Fig. 29 is a flowchart showing a first example of a control process derived from the first steering angle assist pattern. The control process shown in Fig. 29 differs from the basic control process of the first steering angle assist pattern shown in the flowchart of Fig. 8 in that it adds a measure to deal with the case where the direction of the reference trajectory is opposite to the steering direction of the driver.

[0095] In steps S761 to S763, S765, S766, and S767 of the flowchart in FIG. 29, the same processing as in steps S701 to S706 of the flowchart in FIG. 8 is performed, and therefore detailed description thereof will be omitted here.

[0096] After determining the reference trajectory and the predicted travel trajectory, if the vehicle control device 500 determines that the driver is performing a steering operation, the process proceeds to step S764. In step S764, the vehicle control device 500 determines whether the steering direction along the reference trajectory and the steering direction along the predicted travel trajectory are the same at a position a predetermined distance ahead of the vehicle 10.

[0097] If the steering direction along the reference trajectory and the steering direction along the predicted travel trajectory are the same, the vehicle control device 500 proceeds to step S765 and subsequent steps to implement steering-related assist control. On the other hand, if the steering direction along the reference trajectory is opposite to the steering direction along the predicted travel trajectory, the vehicle control device 500 returns to step S761 and postpones the implementation of steering-related assist control (in other words, sets the steering assist amount to zero). In other words, if the steering direction along the reference trajectory and the steering direction along the predicted travel trajectory are opposite directions, the driver's steering operation is prioritized, and the control to approach the reference trajectory is canceled.

[0098] "Second Derivation of First Steering Angle Assist Pattern" The flowchart in Fig. 30 shows a second example of a control process derived from the first steering angle assist pattern. The control process shown in Fig. 30 differs from the basic control process of the first steering angle assist pattern shown in the flowchart in Fig. 8 in that it adds a measure to deal with the case where the direction of the reference trajectory and the steering direction of the driver are opposite, and further differs from the control process shown in the flowchart in Fig. 29 in that it is configured to perform assist control to prioritize safety when an obstacle is present.

[0099] In steps S771 to S773, S776, S777, and S778 in the flowchart of FIG. 30, the same processing as in steps S701 to S706 in the flowchart of FIG. 8 is performed, and therefore detailed description thereof will be omitted here.

[0100] After determining the reference trajectory and the predicted travel trajectory, if the vehicle control device 500 determines that the driver is performing a steering operation, the process proceeds to step S774. In step S774, the vehicle control device 500 determines whether the steering direction along the reference trajectory and the steering direction along the predicted travel trajectory are the same direction at a position a first predetermined distance forward from the vehicle 10.

[0101] If the steering direction along the reference trajectory and the steering direction along the predicted travel trajectory are the same, the vehicle control device 500 proceeds to step S776 and subsequent steps to execute assist control related to steering. On the other hand, if the steering direction along the reference trajectory and the steering direction along the predicted travel trajectory are opposite directions, the vehicle control device 500 proceeds to step S775. In step S775, the vehicle control device 500 determines whether or not an obstacle that will hinder the travel of the vehicle 10 when the vehicle 10 travels along the predicted travel trajectory has been detected on the predicted travel trajectory a second predetermined distance ahead of the vehicle 10.

[0102] If there is no obstacle on the predicted travel trajectory, the vehicle control device 500 returns to step S771 and postpones the implementation of steering-related assist control (in other words, sets the steering-related assist amount to zero). In other words, if there is no obstacle on the predicted travel trajectory, the vehicle control device 500 prioritizes the driver's steering operation and causes the vehicle 10 to travel along a route corresponding to the driver's steering operation, even if the steering direction along the reference trajectory and the steering direction along the predicted travel trajectory are opposite directions.

[0103] On the other hand, if an obstacle is present on the predicted driving trajectory, the vehicle control device 500 proceeds to step S776 and subsequent steps, and performs assist control related to steering to bring the driving trajectory of the vehicle 10 closer to the reference trajectory. In other words, if an obstacle is present on the predicted driving trajectory, there is a possibility that the vehicle 10 will come into contact with the obstacle if the vehicle 10 is caused to drive along a trajectory according to the driver's steering operation. Therefore, the vehicle control device 500 prioritizes the driving safety of the vehicle 10 by performing assist control to bring the driving trajectory of the vehicle 10 closer to the reference trajectory (a route that bypasses the obstacle), even though this goes against the driver's steering intention.

[0104] 31 and 32 show assist control when the steering direction along the reference trajectory is opposite to the steering direction along the predicted travel trajectory. Fig. 31 shows assist control when the control process shown in the flowchart of Fig. 29 is executed or when the control process shown in the flowchart of Fig. 30 is executed, and there is no obstacle on the predicted travel trajectory, i.e., driver-priority assist control (driver-priority mode). In this case, even if the steering direction along the reference trajectory is opposite to the steering direction along the predicted travel trajectory, the vehicle control device 500 cancels the assist control that would bring the travel trajectory of the vehicle 10 closer to the reference trajectory, in other words, sets the amount of assistance related to the steering angle to zero, thereby avoiding assistance in a direction contrary to the driver's steering intention.

[0105] On the other hand, Figure 32 shows assist control (in other words, safety-priority assist control, safety-priority mode) when the control process shown in the flowchart of Figure 30 is executed and an obstacle is present on the predicted travel trajectory. In this case, since an obstacle is present on the predicted travel trajectory, assist control intervenes to bring the travel trajectory of the vehicle 10 closer to a reference trajectory that bypasses the obstacle, thereby preventing the vehicle 10 from contacting the obstacle. Note that the assist control (driver-priority mode) shown in the flowchart of Figure 29 and the assist control (safety-priority mode) shown in Figure 30 can be configured to be arbitrarily changeable, and for example, the driver can be configured to select either the driver-priority mode or the safety-priority mode by operating a switch.

[0106] "Third Derivation of First Steering Angle Assist Pattern" The flowchart in Fig. 33 shows a third example of a control process derived from the first steering angle assist pattern. In this third example, a process for suppressing assist when the tire grip force exceeds its limit (in other words, when the tire force is saturated), specifically a process for setting the assist amount to zero or a process for reducing the assist amount, is added to the basic control process of the first steering angle assist pattern shown in the flowchart in Fig. 8. Note that in steps S781 to S786 of the flowchart in Fig. 33, the same processes as in steps S701 to S706 of the flowchart in Fig. 8 are performed, and therefore detailed description thereof will be omitted here.

[0107] After the vehicle control device 500 performs processing in steps S781 to S786 to reflect the amount of assist corresponding to the positional deviation between the reference trajectory and the predicted traveling trajectory in the actual steering angle or steering assist force of the steered wheels (front wheels 11, 12), the process proceeds to step S787. In step S787, the vehicle control device 500 determines whether the tire force will saturate while assist control is being implemented, or more specifically, whether the tire grip force is about to exceed its limit or whether the tire grip force has exceeded its limit, based on the longitudinal force and lateral force (cornering force) of the tire.

[0108] If the vehicle control device 500 determines in step S787 that the tire force is saturated, it proceeds to step S788 if the steering device 610 is a steer-by-wire system, or to step S789 if the steering device 610 is an electric power steering device. In step S788 or step S789, the vehicle control device 500 cancels the reflection of the assist amount corresponding to the positional deviation between the reference trajectory and the predicted traveling trajectory, that is, it sets the assist amount to zero, or it performs processing to correct the assist amount to a value closer to zero than the assist amount set in step S784 (hereinafter referred to as processing to reduce the assist amount). In other words, the vehicle control device 500 adjusts the assist amount by steering-related assist control so that the tire force does not become saturated (in other words, so that the tire grip force does not exceed its limit).

[0109] Here, the operation of the assist control shown in the flowchart of Fig. 33 will be described with reference to Fig. 34 and Fig. 35. Fig. 34 shows a reference trajectory set to detour around an obstacle on a curved road where an obstacle is present. Fig. 35 is a tire friction circle with the longitudinal force (driving / braking force) of the tire on the vertical axis and the cornering force (right and left turning force) on the horizontal axis, and shows the tire grip force when the vehicle 10 travels along the reference trajectory, and the tire grip force when accelerator control is canceled to set the assist amount to zero.

[0110] Here, the reference trajectory is a trajectory in which a sudden right turn to avoid an obstacle would cause the tire grip force to exceed its limit. Therefore, the vehicle control device 500 controls the traveling trajectory of the vehicle 10 to approach the reference trajectory, and when the tire grip force exceeds its limit, the vehicle control device 500 sets the assist amount to zero or performs processing to reduce the assist amount, thereby preventing tire slippage due to assist control.

[0111] Next, a description will be given of a control process derived from the above-mentioned second steering angle assist pattern, that is, a steering angle assist pattern that assists the steering angle in accordance with the curvature of the reference trajectory. "First Derivation of Second Steering Angle Assist Pattern" Figure 36 is a flowchart showing a first example of a control process derived from the second steering angle assist pattern, which differs from the basic control process of the second steering angle assist pattern shown in the flowchart of Figure 17 in that it adds a measure to deal with the case where the direction of the reference trajectory is opposite to the steering direction of the driver.

[0112] The vehicle control device 500 generates a reference trajectory in step S791, and calculates a predicted travel trajectory of the vehicle 10 in step S792. Then, the vehicle control device 500 determines in step S793 whether or not the driver has performed a steering operation, and if the driver has performed a steering operation, proceeds to step S794.

[0113] In step S794, the vehicle control device 500 determines whether the steering direction along the reference trajectory and the steering direction along the predicted travel trajectory are the same at a position a first predetermined distance forward from the vehicle 10. If the steering direction along the reference trajectory and the steering direction along the predicted travel trajectory are the same, the vehicle control device 500 proceeds to steps S796 to S798, and performs assist control based on the curvature of the reference trajectory, similar to steps S714 to S716 in the flowchart of FIG.

[0114] On the other hand, if the steering direction along the reference trajectory and the steering direction along the predicted travel trajectory are opposite directions, the vehicle control device 500 proceeds to step S795. In step S795, the vehicle control device 500 determines whether the predicted travel trajectory is likely to go outside the travelable range of the reference trajectory.

[0115] If the predicted travel trajectory passes through the drivable range and does not go beyond the drivable range, the vehicle control device 500 prioritizes the steering operation by the driver by returning to step S791 without performing assist control. On the other hand, if the predicted travel trajectory is likely to go beyond the drivable range, the vehicle control device 500 proceeds to step S796 and subsequent steps and performs assist control based on the curvature of the reference trajectory.

[0116] In other words, by proceeding from step S795 to step S796 and thereafter, the vehicle control device 500 brings the trajectory of the vehicle 10 closer to the reference trajectory so that the vehicle 10 travels inside the drivable range. In this way, when the predicted travel trajectory is likely to go outside the drivable range, the vehicle control device 500 brings the trajectory closer to the curvature of the reference trajectory, even if it is opposite to the direction of the steering operation by the driver, thereby guiding the vehicle 10 to travel within the drivable range, and giving priority to safe travel of the vehicle 10.

[0117] Fig. 37 is a diagram for explaining the action and function of the steering angle assist pattern shown in the flowchart of Fig. 36. The state shown in Fig. 37 is a state in which the turning direction of the reference trajectory and the turning direction of the predicted travel trajectory are opposite to each other, and it is predicted that the vehicle 10 will go outside the drivable range when traveling along the predicted travel trajectory.

[0118] In this case, even if the turning direction of the reference trajectory and the turning direction of the predicted travel trajectory are opposite, the vehicle control device 500 performs assist control to move the vehicle 10 closer to the reference trajectory, thereby performing assist so that the vehicle 10 passes within the drivable range. Conversely, even if the turning direction of the reference trajectory and the turning direction of the predicted travel trajectory are opposite, if it is predicted that the vehicle 10 will pass within the drivable range, the vehicle control device 500 cancels the assist control, in other words, sets the assist amount to zero.

[0119] Next, the braking / driving force assist control by the vehicle control device 500 will be described in detail. The vehicle control device 500 can create a target vehicle speed in braking / driving force assist control using, for example, one of the following two patterns. First target vehicle speed creation pattern: The target vehicle speed is created based on the curvature of the reference trajectory. Second target vehicle speed creation pattern: The target vehicle speed is created based on the curvature derivative of the reference trajectory.

[0120] 38 shows a braking / driving force assist pattern that employs the first target vehicle speed creation pattern and sets the amount of braking / driving force assistance based on the magnitude of the target longitudinal acceleration. In step S801, the vehicle control device 500 generates a reference trajectory, and in step S802, calculates the curvature of the reference trajectory.

[0121] Furthermore, in step S803, the vehicle control device 500 calculates a target vehicle speed for the traveling of the vehicle 10 based on the curvature of the reference trajectory. Then, in the next step S804, the vehicle control device 500 differentiates the target vehicle speed to calculate a target longitudinal acceleration.

[0122] After calculating the target longitudinal acceleration, the vehicle control device 500 determines in step S805 whether the driver has operated the brake pedal, in other words, whether the driver has performed a brake operation. If the driver has not operated the brake pedal, the vehicle control device 500 returns to step S801 and cancels the assist control related to the braking force.

[0123] On the other hand, if the driver is operating the brake pedal, the vehicle control device 500 proceeds to step S806, where it calculates an assist amount for the braking force based on the target longitudinal acceleration. Then, in the next step S807, the vehicle control device 500 reflects the assist amount in the braking force generated by the braking device 630. That is, in step S807, the vehicle control device 500 reflects the assist amount in the brake fluid pressure, regenerative braking force, electric caliper pressing force, etc.

[0124] After calculating the target longitudinal acceleration, the vehicle control device 500 determines in step S808 whether the driver has operated the accelerator pedal, in other words, whether the driver has operated the accelerator pedal. If the driver has not operated the accelerator pedal, the vehicle control device 500 returns to step S801 and cancels the assist control related to the driving force.

[0125] On the other hand, if the driver is operating the accelerator pedal, the vehicle control device 500 proceeds to step S809, where it calculates an assist amount related to the driving force based on the target longitudinal acceleration. Then, in the next step S810, the vehicle control device 500 reflects the assist amount in the driving force generated by the drive device 620. That is, in step S810, the vehicle control device 500 reflects the assist amount in the accelerator opening, motor torque, engine torque, etc.

[0126] Fig. 39 illustrates a reference trajectory generated for a curved road, and Fig. 40 illustrates a steering angle and a target vehicle speed corresponding to the curvature of the reference trajectory in Fig. 39. As shown in Figs. 39 and 40, the vehicle control device 500 can set the target vehicle speed so that the vehicle decelerates before the reference trajectory turns, i.e., before the curve, and starts to accelerate before exiting the curve (in other words, before the reference trajectory becomes straight).

[0127] Furthermore, Figure 41 shows a driving trajectory when the steering angle is assisted under the first steering angle assist pattern and the braking force assist control shown in Figure 38 is also implemented. Furthermore, Figure 42 is a time chart showing the differences in actual steering angle, vehicle speed, and lateral acceleration depending on whether or not assist control is implemented. When driving without assist control as exemplified in Figures 41 and 42, the driver's steering operation before the curve is initiated late, causing the vehicle 10 to veer into the oncoming lane, resulting in a sudden turn and large lateral acceleration. Furthermore, when driving without assist control, unnecessary lateral acceleration occurs because the vehicle enters the curve without decelerating.

[0128] In contrast, when assist control is implemented, steering is assisted according to the difference between the position of the reference trajectory and the position of the predicted traveling trajectory, and the target vehicle speed is set based on the curvature of the reference trajectory, so even if the driver's start timing of steering operation before the curve is delayed, the vehicle 10 can enter the curve on a trajectory suitable for curve driving. Furthermore, when assist control is implemented, the vehicle decelerates to an appropriate speed before the curve, so the generation of unnecessary lateral acceleration is suppressed.

[0129] Furthermore, Figure 43 shows the traveling trajectory at the curve exit when the steering angle is assisted using the first steering angle assist pattern and the braking force assist control shown in Figure 38 is implemented. Furthermore, Figure 44 is a time chart showing the difference in lateral acceleration and vehicle speed depending on whether assist control is implemented. When traveling without assist control at the curve exit as shown in Figures 43 and 44, the vehicle 10 does not accelerate even after exiting the curve, causing it to slow down on the curve. Furthermore, even at the curve exit, the vehicle 10 travels along the inside of the curve, making the turn sharp and increasing the lateral acceleration generated in the vehicle 10. In contrast, when assist control is implemented, acceleration begins at the end of the curve, preventing the vehicle 10 from slowing down on the curve. Furthermore, the vehicle 10 is driven on the outside of the lane at the curve exit, reducing the lateral acceleration generated in the vehicle 10.

[0130] 45 shows a control pattern that employs a second target vehicle speed generation pattern that generates a target vehicle speed based on a curvature differential value of a reference trajectory, and sets the amount of assist in braking / driving force based on the magnitude of the target longitudinal acceleration. In step S821, the vehicle control device 500 generates a reference trajectory, and in step S822, calculates the curvature of the reference trajectory.

[0131] Furthermore, in step S823, the vehicle control device 500 calculates the differential value of the curvature of the reference trajectory. Then, in step S824, the vehicle control device 500 calculates the target vehicle speed for the traveling of the vehicle 10 based on the differential value of the curvature of the reference trajectory, and in the next step S825, differentiates the target vehicle speed to calculate the target longitudinal acceleration. Thereafter, the processing from step S826 to step S831 is the same as step S805 to step S810 in the flowchart of FIG. 38, and therefore detailed description thereof will be omitted here.

[0132] Fig. 46 is a time chart showing how the deceleration amount before a curve is varied in accordance with the differential value of the curvature (steering angular velocity) and the steering timing when traveling on a curve such as that shown in Fig. 39. Fig. 46 also illustrates an intermediate assist control characteristic between assist control in which the steering is started slowly but the steering is performed quickly to stay on track, and assist control in which the steering is started quickly but the steering speed is slowed to stay on track.

[0133] Here, the vehicle control device 500 varies the deceleration amount before the curve in accordance with the differential value of the curvature (steering angular velocity) and the steering timing in accordance with the steering assist control. In other words, if the steering starts late but the assist control is performed to turn quickly and get the vehicle on track, the timing of the start of deceleration before the curve will also be delayed, and the acceleration of deceleration (negative acceleration) will be fast. Conversely, if the steering starts early but the assist control is performed to turn slowly and get the vehicle on track, the timing of the start of deceleration before the curve will also be advanced, and the acceleration of deceleration will be slow.

[0134] Next, a control pattern for determining the amount of braking / driving force assistance based on a target speed (in other words, a reference speed as reference information) will be described. As described above, there are two patterns for determining the target speed: one that determines the target speed based on the curvature of the reference trajectory, and one that determines the target speed based on the differential value of the curvature of the reference trajectory.

[0135] The vehicle control device 500 can employ, for example, any of the following five patterns as a control pattern for determining the amount of braking / driving force assistance based on the target speed. First braking / driving assist pattern: Assists braking / driving force according to the difference between the target speed and the vehicle speed predicted from the predicted driving trajectory (hereinafter referred to as predicted vehicle speed). Second braking / driving assist pattern: Assists braking / driving force according to the acceleration of the target vehicle speed. Third braking / driving assist pattern: Assists braking / driving force according to the jerk of the target vehicle speed (differential value of acceleration). Fourth braking / driving assist pattern: Assists braking / driving force according to the difference between the acceleration of the target vehicle speed and the acceleration of the predicted vehicle speed. Fifth braking / driving assist pattern: Assists braking / driving force according to the difference between the jerk of the target vehicle speed and the jerk of the predicted vehicle speed.

[0136] Here, the first braking / driving assist pattern, the fourth braking / driving assist pattern, and the fifth braking / driving assist pattern use a predicted driving trajectory (a predicted driving state including vehicle speed, acceleration, and jerk), and are therefore braking / driving assist patterns that can be implemented by the vehicle control device 500 shown in Fig. 3. On the other hand, the second braking / driving assist pattern and the third braking / driving assist pattern do not use a predicted driving trajectory (a predicted driving state), and are therefore braking / driving assist patterns that can be implemented by the vehicle control device 500 shown in Fig. 2.

[0137] The processing content for each braking / driving assist pattern will be explained in detail below. "First braking / driving assist pattern" The flowchart in Figure 47 shows the control process of the first braking / driving assist pattern, which assists braking / driving force in accordance with the difference between a target speed as reference information and a predicted vehicle speed. In step S841, the vehicle control device 500 generates a reference trajectory using the current position of the vehicle 10 as a starting point.

[0138] Then, the vehicle control device 500 calculates the curvature of the reference trajectory in step S842, and calculates a target speed based on the curvature of the reference trajectory in the next step S843. The vehicle control device 500 also calculates a predicted traveling trajectory in step S844, and calculates the curvature of the predicted traveling trajectory in step S845. Furthermore, the vehicle control device 500 calculates a predicted vehicle speed based on the curvature of the predicted traveling trajectory in step S846.

[0139] After the vehicle control device 500 calculates the target speed and predicted vehicle speed in steps S841 to S846, the vehicle control device 500 proceeds to step S847 to determine whether the driver has operated the brake pedal. If the driver has not operated the brake pedal, the vehicle control device 500 returns to step S841 to cancel assist control related to braking force.

[0140] On the other hand, if the driver is operating the brake pedal, the vehicle control device 500 proceeds to step S848, where it calculates an assist amount for braking force based on the difference between the target speed and the predicted vehicle speed. For example, the vehicle control device 500 sets the assist amount so that the braking force increases the higher the predicted vehicle speed is compared to the target speed. Then, in the next step S849, the vehicle control device 500 reflects the assist amount in the braking force generated by the braking device 630.

[0141] After determining the target speed and predicted vehicle speed in steps S841 to S846, the vehicle control device 500 determines whether the driver has operated the accelerator pedal in step S850. If the driver has not operated the accelerator pedal, the vehicle control device 500 returns to step S841 and cancels the assist control related to the driving force.

[0142] On the other hand, if the driver is operating the accelerator pedal, the vehicle control device 500 proceeds to step S851, where it calculates an assist amount related to the driving force based on the difference between the target speed and the predicted vehicle speed. For example, the vehicle control device 500 sets the assist amount so that the driving force is increased the more the predicted vehicle speed is lower than the target speed. Then, in the next step S852, the vehicle control device 500 reflects the assist amount in the driving force generated by the drive device 620.

[0143] "Second braking / driving assist pattern" The control process shown in the flowchart of Figure 38, which was previously described as a pattern for creating a target vehicle speed, corresponds to a second braking / driving assist pattern that assists braking / driving force in accordance with the acceleration of the target vehicle speed, which is reference information. Therefore, as the flowchart of Figure 38 shows the control process of the second braking / driving assist pattern that assists braking / driving force in accordance with the acceleration of the target vehicle speed, a detailed description will be omitted here.

[0144] "Third braking / driving assist pattern" The flowchart in Fig. 48 shows the control process of a third braking / driving assist pattern that assists braking / driving force in accordance with the jerk of the target vehicle speed (target longitudinal jerk), which is reference information. Here, the processing from generation of the reference trajectory in steps S861 to S864 in the flowchart in Fig. 48 to determination of the target longitudinal acceleration is the same as the processing in steps S801 to S804 in the flowchart in Fig. 38, and therefore detailed description thereof will be omitted.

[0145] After the vehicle control device 500 calculates the target longitudinal acceleration in step S864, the process proceeds to step S865, where it calculates the target longitudinal jerk, which is the time differential value of the target longitudinal acceleration. After calculating the target longitudinal jerk in step S865, the vehicle control device 500 proceeds to step S866, where it determines whether or not the driver has operated the brake pedal. If the driver has not operated the brake pedal, the vehicle control device 500 returns to step S861, thereby canceling the assist control related to the braking force.

[0146] On the other hand, if the driver is operating the brake pedal, the vehicle control device 500 proceeds to step S867, where it calculates an assist amount related to braking force based on the target longitudinal jerk. Here, the vehicle control device 500 determines whether the deceleration rate is increasing or decreasing based on the target longitudinal jerk, and determines whether to increase or decrease the braking force in the assist control related to braking force based on the result of this determination. Furthermore, the vehicle control device 500 can variably set the magnitude of the assist amount based on the magnitude of the target longitudinal jerk. Then, in the next step S868, the vehicle control device 500 reflects the assist amount in the braking force generated by the brake device 630.

[0147] After calculating the target longitudinal jerk in step S865, the vehicle control device 500 proceeds to step S869 to determine whether the driver has operated the accelerator pedal. If the driver has not operated the accelerator pedal, the vehicle control device 500 returns to step S861 to cancel the assist control related to the driving force.

[0148] On the other hand, if the driver is operating the accelerator pedal, the vehicle control device 500 proceeds to step S870 and calculates an assist amount related to driving force based on the target longitudinal jerk. Here, the vehicle control device 500 determines whether the acceleration rate is tending to increase or decrease based on the target longitudinal jerk, and determines whether to increase or decrease the driving force in the assist control related to driving force based on the determination result. Furthermore, the vehicle control device 500 can variably set the magnitude of the assist amount based on the magnitude of the target longitudinal jerk. Then, in the next step S871, the vehicle control device 500 reflects the assist amount in the driving force generated by the drive device 620.

[0149] "Fourth Braking / Drive Assist Pattern" The flowchart in Figure 49 shows the control process of a fourth braking / driving assist pattern that assists braking / driving force in accordance with the difference between the acceleration of the target vehicle speed and the acceleration of the predicted vehicle speed. In steps S881 to S884, the vehicle control device 500 calculates the target longitudinal acceleration, similar to steps S861 to S864 of the flowchart in Figure 48. Furthermore, in steps S885 to S887, the vehicle control device 500 calculates the predicted speed, similar to steps S844 to S846 of the flowchart in Figure 47. Then, in step S888, the vehicle control device 500 calculates the predicted longitudinal acceleration by differentiating the predicted speed with respect to time.

[0150] After calculating the target longitudinal acceleration and the predicted longitudinal acceleration, the vehicle control device 500 proceeds to step S889 to determine whether the driver has operated the brake pedal. If the driver has not operated the brake pedal, the vehicle control device 500 returns to step S881 to cancel the assist control related to the braking force.

[0151] On the other hand, if the driver is operating the brake pedal, the vehicle control device 500 proceeds to step S890, where it calculates an assist amount for braking force based on the difference between the target longitudinal acceleration and the predicted longitudinal acceleration so that the predicted longitudinal acceleration approaches the target longitudinal acceleration. Then, in the next step S891, the vehicle control device 500 reflects the assist amount in the braking force generated by the brake device 630.

[0152] After calculating the target longitudinal acceleration and the predicted longitudinal acceleration, the vehicle control device 500 proceeds to step S892 to determine whether the driver has operated the accelerator pedal. If the driver has not operated the accelerator pedal, the vehicle control device 500 returns to step S881 to cancel the assist control related to the driving force.

[0153] On the other hand, if the driver is operating the accelerator pedal, the vehicle control device 500 proceeds to step S893, where it calculates an assist amount for the driving force based on the difference between the target longitudinal acceleration and the predicted longitudinal acceleration so that the predicted longitudinal acceleration approaches the target longitudinal acceleration. Then, in the next step S894, the vehicle control device 500 reflects the assist amount in the driving force generated by the drive device 620.

[0154] "Fifth Braking / Drive Assist Pattern" The flowchart in Figure 50 shows the control process of a fifth braking / driving assist pattern that assists braking / driving force in accordance with the difference between the jerk of the target vehicle speed, which is reference information, and the jerk of the predicted vehicle speed. In steps S901 to S904, the vehicle control device 500 calculates the target longitudinal acceleration in the same manner as steps S881 to S884 of the flowchart in Figure 49. Then, in the next step S905, the vehicle control device 500 calculates the target longitudinal jerk by time-differentiating the target longitudinal acceleration.

[0155] Furthermore, in steps S906 to S909, the vehicle control device 500 calculates the predicted longitudinal acceleration in the same manner as in steps S885 to S888 of the flowchart in Fig. 49. Then, in the next step S910, the vehicle control device 500 calculates the predicted longitudinal jerk by time-differentiating the predicted longitudinal acceleration.

[0156] After calculating the target longitudinal jerk and the predicted longitudinal jerk, the vehicle control device 500 proceeds to step S911 and determines whether the driver has operated the brake pedal. If the driver has not operated the brake pedal, the vehicle control device 500 returns to step S901 and cancels the assist control related to the braking force.

[0157] On the other hand, if the driver is operating the brake pedal, the vehicle control device 500 proceeds to step S912, where it calculates an assist amount related to the braking force based on the difference between the target longitudinal jerk and the predicted longitudinal jerk so that the predicted longitudinal jerk approaches the target longitudinal jerk. Then, in the next step S913, the vehicle control device 500 reflects the assist amount in the braking force generated by the braking device 630.

[0158] After calculating the target longitudinal jerk and the predicted longitudinal jerk, the vehicle control device 500 proceeds to step S914 to determine whether the driver has operated the accelerator pedal. If the driver has not operated the accelerator pedal, the vehicle control device 500 returns to step S901 to cancel the assist control related to the driving force.

[0159] On the other hand, if the driver is operating the accelerator pedal, the vehicle control device 500 proceeds to step S915, where it calculates an assist amount related to the driving force based on the difference between the target longitudinal jerk and the predicted longitudinal jerk so that the predicted longitudinal jerk approaches the target longitudinal jerk. Then, in the next step S916, the vehicle control device 500 reflects the assist amount in the driving force generated by the drive device 620.

[0160] Incidentally, when the driver performs a steering operation in a direction away from the reference trajectory, the vehicle control device 500 can cancel the steering angle assist control and notify the driver that the driving operation is an undesirable steering operation in a direction away from the reference trajectory. The flowchart in Figure 51 shows, as a derivative of the second steering angle assist pattern, assist control in which the steering angle assist control is canceled for a steering operation in a direction away from the reference trajectory and a notification (warning) is given to the driver.

[0161] In steps S921 to S923, the vehicle control device 500 generates a reference trajectory, calculates the curvature of the reference trajectory, and determines whether or not the driver is performing a steering operation, similar to steps S711 to S713 in the flowchart of Fig. 17. If the vehicle control device 500 determines in step S923 that the driver is performing a steering operation, the process proceeds to step S924.

[0162] In step S924, the vehicle control device 500 determines whether the direction of the curvature of the reference trajectory is the same as or opposite to the direction of the steering operation by the driver. If the direction of the curvature of the reference trajectory is the same as the direction of the steering operation by the driver, the vehicle control device 500 proceeds to steps S926 and S927, where it reflects the amount of assist based on the curvature of the reference trajectory in the steering angle of the steer-by-wire system, as in steps S714 and S715.

[0163] On the other hand, if the direction of the curvature of the reference trajectory is opposite to the direction of the steering operation by the driver, in other words, if the steering direction included in the physical quantity related to the driving operation is a direction in which the vehicle 10 moves away from the reference trajectory included in the reference information, the vehicle control device 500 proceeds to step S925 and outputs a notification command to notify the driver of the steering operation to a notification unit included in the vehicle 10. As the notification unit, a head-up display (HUD), a liquid crystal screen, a lamp, a buzzer, or the like may be used.

[0164] Furthermore, in a vehicle 10 equipped with a steer-by-wire system, a warning can be given to the driver by vibrating the steering wheel with a steering reaction force actuator. In this case, the steer-by-wire system, specifically, the combination of the steering reaction force actuator and the steering wheel, functions as a warning unit. The vehicle control device 500 can also warn the driver by operating multiple warning units in parallel. When the driver receives a warning from a warning unit, the driver can recognize that a steering operation has been performed in a direction away from the reference trajectory, and the driver's steering operation can be guided in a direction that improves vehicle comfort and safety, i.e., in a direction along the reference trajectory.

[0165] Furthermore, in the vehicle 10 equipped with the steer-by-wire system, the vehicle control device 500 (assist unit 505) can calculate the assist amount as a control amount of the steering reaction force applied to the steering wheel. In other words, by adjusting the steering reaction force applied to the steering wheel, the vehicle control device 500 can make the driving of the vehicle 10 by the driver approach the reference information acquired based on the reference trajectory.

[0166] The flowchart in Fig. 52 illustrates an example of assist control in which the steering reaction force applied to the steering wheel is controlled in a vehicle 10 equipped with a steer-by-wire system. The control process shown in the flowchart in Fig. 52 is based on the second steering angle assist pattern, and instead of directly adjusting the steering angle, the vehicle control device 500 assists the driver's operation of the steering wheel in a direction in which the traveling trajectory of the vehicle 10 approaches the reference trajectory by adjusting the steering reaction force applied to the steering wheel.

[0167] In steps S931 to S933, the vehicle control device 500 generates a reference trajectory, calculates the curvature of the reference trajectory, and determines whether or not the driver is performing a steering operation, similar to steps S711 to S713 in the flowchart of FIG. 17. Then, in step S934, the vehicle control device 500 determines whether the direction of the curvature of the reference trajectory and the direction of the driver's steering operation are the same or opposite. Here, if the direction of the curvature of the reference trajectory and the direction of the driver's steering operation are opposite, the vehicle control device 500 cancels the assist control related to the steering angle by returning to step S931.

[0168] On the other hand, if the direction of the curvature of the reference trajectory and the direction of the steering operation by the driver are the same, the vehicle control device 500 proceeds to step S935 and subsequent steps to perform assist control related to the steering angle. In step S935, the vehicle control device 500 applies a stronger steering reaction force to the steering wheel than usual, making it more difficult for the driver to turn the steering wheel. In other words, the vehicle control device 500 calculates the assist amount as a control amount for the steering reaction force applied to the steering wheel. Then, in step S936, the vehicle control device 500 changes the actual steering angle in accordance with the steering operation of the steering wheel.

[0169] Next, in step S937, the vehicle control device 500 determines whether the trajectory resulting from the driver's driving operation has approached the reference trajectory. If the trajectory resulting from the driver's driving operation has not approached the reference trajectory, the vehicle control device 500 returns to step S935 and continues the process of increasing the steering reaction force applied to the steering wheel. On the other hand, if the trajectory resulting from the driver's driving operation has approached the reference trajectory, the vehicle control device 500 proceeds to step S938 and reduces the steering reaction force applied to the steering wheel to return it to a normal value.

[0170] Figure 53 is a diagram for explaining the operation of the assist control shown in Figure 52, which controls the steering reaction force applied to the steering wheel. The upper part shows the steering wheel operation angle (steering wheel angle), and the lower part shows the traveling trajectory of the vehicle 10 relative to the steering wheel operation angle. When traveling on a curved road, if the driver's skill level is low, the timing at which the driver starts steering will be late, and the driver will panic and make a large steering operation, causing the actual steering angle to overshoot and resulting in steering back. When such a steering operation is performed, the vehicle 10 will travel on a trajectory that suddenly cuts from the outside to the inside of the curve, reducing the comfort and safety of the vehicle 10.

[0171] In contrast, if the steering reaction force applied to the steering wheel is strengthened (increased) as an assist control, it becomes more difficult for the driver to suddenly turn the steering wheel, thereby suppressing excessive steering operation. As a result, the traveling trajectory of the vehicle 10 is prevented from overshooting the reference trajectory, and convergence to the reference trajectory is improved, thereby improving the comfort and safety of the vehicle 10.

[0172] 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.

[0173] For example, the microcomputer having the function of the trajectory generating unit 503 and the microcomputer having the function of the assist unit 505 can be separate microcomputers. Furthermore, the vehicle control device 500 can control the steering reaction force applied to the steering wheel while directly adjusting the steering angle as an assist control related to the steering angle.

[0174] 10... Vehicle, 100... Vehicle driving system, 200... External environment recognition unit, 300... Vehicle momentum detection unit, 400... Driving operation amount detection unit, 500... Vehicle control device, 600... Driving actuator

Claims

1. A vehicle control device comprising: a vehicle motion quantity acquisition unit that acquires physical quantities related to the motion of the vehicle; a driving operation quantity acquisition unit that acquires physical quantities related to the driving operation of the vehicle by a driver; a trajectory generation unit that generates a reference trajectory based on a driving range ahead of the vehicle and predetermined constraint conditions when the vehicle drives within the driving range; and an assist unit that calculates an assist amount that brings the driving of the vehicle by the driver closer to the reference information based on the physical quantities related to the motion of the vehicle, the physical quantities related to the driving operation of the vehicle, and reference information acquired based on the reference trajectory, and outputs the assist amount to a driving actuator of the vehicle.

2. A vehicle control device as described in claim 1, wherein the assist unit determines the assist amount to increase the steering amount of the steered wheels of the vehicle when the reference trajectory included in the reference information is on the same side as the steering direction included in the physical quantity related to the driving operation of the vehicle and ahead of the steering direction, determines the assist amount to reduce or maintain the steering amount when the reference trajectory included in the reference information is on the same side as the steering direction included in the physical quantity related to the driving operation of the vehicle and ahead of the steering direction, and sets the assist amount to zero when the reference trajectory included in the reference information is on the opposite side of the steering direction included in the physical quantity related to the driving operation of the vehicle and priority is given to the driving operation by the driver.

3. A vehicle control device according to claim 1, wherein the assist unit determines the steering amount of the steered wheels of the vehicle or the vehicle speed as the assist amount based on the curvature of a reference trajectory included in the reference information.

4. A vehicle control device according to claim 1, wherein the assist unit determines the steering speed of the steered wheels of the vehicle or the vehicle speed as the amount of assist based on a differential value of the curvature of a reference trajectory included in the reference information.

5. A vehicle control device as described in claim 1, wherein the assist unit determines the amount of assistance related to the steering amount so that the timing of intervention in the steering amount of the steered wheels of the vehicle differs between when the vehicle is traveling on the inside of a turn and when the vehicle is traveling on the outside of a turn, with respect to a reference trajectory included in the reference information.

6. A vehicle control device as claimed in claim 1, wherein the assist unit sets the amount of assistance to zero if the tire force of the vehicle becomes saturated when the vehicle approaches a reference trajectory included in the reference information.

7. A vehicle control device according to claim 1, wherein the assist unit brings the vehicle closer to a reference trajectory included in the reference information so that the vehicle travels within the driving range.

8. A vehicle control device as described in claim 1, wherein the assist unit determines the amount of assist based on the closest point of a reference trajectory included in the reference information for the vehicle, or a specified point on the reference trajectory ahead in the traveling direction of the vehicle.

9. A vehicle control device as described in claim 1, wherein the assist unit determines the assist amount that brings the predicted driving trajectory of the vehicle, which is predicted based on physical quantities related to the motion of the vehicle, physical quantities related to the driving operation of the vehicle, and the past driving trajectory of the vehicle, closer to a reference trajectory included in the reference information.

10. A vehicle control device as described in claim 1, further comprising a vehicle driving trajectory prediction unit that predicts a predicted driving trajectory of the vehicle based on physical quantities related to the motion of the vehicle, physical quantities related to the driving operation of the vehicle, and a past driving trajectory of the vehicle, and the trajectory generation unit generates the reference trajectory by adding the predicted driving trajectory.

11. A vehicle control device as described in claim 1, comprising a vehicle motion state prediction unit that predicts the motion state of the vehicle based on physical quantities related to the motion of the vehicle, physical quantities related to the driving operation of the vehicle, and the past driving trajectory of the vehicle, and the trajectory generation unit generates the reference trajectory by adding the predicted motion state of the vehicle.

12. A vehicle control device as described in claim 1, wherein the assist unit outputs a command to the notification unit of the vehicle to notify the driver of the driving operation when the steering direction included in the physical quantity related to the driving operation of the vehicle is a direction in which the vehicle moves away from the reference trajectory included in the reference information.

13. A vehicle control device according to claim 1, wherein the vehicle has, as the travel actuator, a steer-by-wire system that steers steered wheels of the vehicle that are mechanically separated from a steering wheel.

14. A vehicle control device according to claim 13, wherein the assist unit determines the amount of assist for turning the steered wheels without rotating the steering wheel.

15. A vehicle control device according to claim 13, wherein the assist unit determines the amount of assist as a control amount of the steering reaction force applied to the steering wheel.

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