Driving assistance method and driving assistance device

Abstract

The present invention provides a driver assistance method and a driver assistance device that can increase or decrease the steering angle while ensuring the vehicle's trajectory during autonomous driving. [Solution] A steering angle control device controls the steering angle of the vehicle, and a braking force control device controls the braking force of the front and rear wheels of the vehicle. When the driver assistance controller 13 calculates the target steering angle for the steering angle control device and the target braking force for the front and rear wheels for the braking force control device, it calculates the target yaw rate γ from the half-radius of curvature R of the road, calculates the target vehicle body slip angle β that aligns the forward gaze position with a position on the turning trajectory obtained from the target yaw rate γ and the driving speed V, calculates the target braking force for the front and rear wheels according to the target vehicle body slip angle β, and calculates the target front wheel tire force F that satisfies the balance between the translational direction and the rotational direction of the rigid body from the target yaw rate γ and the target vehicle body slip angle β. YF The target steering wheel tire force F is calculated. YF This calculates the target steering angle θ that satisfies the steering wheel tire force of the two-wheeled model.

Description

[Technical Field]

[0001] The present invention relates to a driver assistance method and a driver assistance device. [Background technology]

[0002] The driver assistance system described in Patent Document 1 below relates to a control device for a vehicle equipped with an autonomous driving function, and in a vehicle equipped with variable braking force means that generates a difference in braking force between the left and right front and rear wheels, the yaw rate and body slip angle that define the turning behavior of the vehicle are controlled to desired values. [Prior art documents] [Patent Documents]

[0003] [Patent Document 1] Japanese Patent Publication No. 2011-207314 [Overview of the project] [Problems that the invention aims to solve]

[0004] However, the driver assistance system described in Patent Document 1 above is only achievable in vehicles capable of controlling the distribution of torque to the front, rear, left, and right wheels. The desired yaw rate and vehicle slip angle cannot be achieved with torque distribution control of only the front and rear wheels, or only the left and right wheels. Furthermore, even in vehicles capable of controlling the distribution of torque to the front, rear, left, and right wheels, the desired yaw rate and vehicle slip angle may not be achievable depending on the suspension geometry. The present invention aims to provide a driving assistance method and a driving assistance device that can increase or decrease the steering angle while ensuring the vehicle's driving trajectory during autonomous driving in a vehicle equipped with front and rear wheel braking and driving force control devices. [Means for solving the problem]

[0005] One aspect of the present invention is, when automatically controlling the steering angle of a vehicle, a steering angle control device that controls the steering angle of the vehicle, a driving and braking force control device that controls the driving and braking forces of the front and rear wheels of the vehicle, and a controller that calculates a target steering angle for the steering angle control device and target driving and braking forces for the front and rear wheels for the driving and braking force control device. The controller calculates a target yaw rate from the turning radius of the vehicle according to the shape of the traveling road ahead of the vehicle, calculates a target vehicle body slip angle that makes the forward gaze position calculated from the forward gaze time and the traveling speed of the vehicle coincide with the position on the turning trajectory obtained from the target yaw rate and the traveling speed, calculates the target driving and braking forces of the front and rear wheels according to the target vehicle body slip angle, calculates a target steered wheel tire force that satisfies the balance between the translational direction and the rotational direction of the rigid body from the target yaw rate and the target vehicle body slip angle, and calculates a target steering angle such that the target steered wheel tire force satisfies the steered wheel tire force of the two-wheel model. This is the gist of the invention.

Advantages of the Invention

[0006] According to one aspect of the present invention, it becomes possible to increase or decrease the steering angle during automatic driving while ensuring the traveling trajectory of the vehicle during automatic driving. The objects and advantages of the present invention are embodied and achieved by using the elements shown in the claims and their combinations. It should be understood that both the foregoing general description and the following detailed description are merely illustrative and explanatory and do not limit the present invention like the claims.

Brief Description of the Drawings

[0007] [Figure 1] It is a schematic configuration diagram of the vehicle of the embodiment. [Figure 2] It is a block diagram of a functional configuration example of the motor controller. [Figure 3] It is a flowchart showing an example of arithmetic processing performed by the driving support controller. [Figure 4] It is a flowchart of a subprogram performed in the arithmetic processing of FIG. 3. [Figure 5] It is an explanatory diagram of the vehicle body slip angle gain set in the arithmetic processing of FIG. 4. [Figure 6] It is an explanatory diagram of the operation by the arithmetic processing in FIG. 3.

Embodiments of the Invention

[0008] Hereinafter, embodiments of the present invention will be described with reference to the drawings. Note that each drawing is schematic and may differ from the actual one. The vehicle in the embodiment shown in FIG. 1 is a vehicle capable of autonomous driving, and includes a front motor 2F that drives the front wheels 1FL, 1FR (front axle 10F) and a rear motor 2R that drives the rear wheels 1RL, 1RR (rear axle 10R). Both the front motor 2F and the rear motor 2R are three-phase AC motors. Therefore, the vehicle in this embodiment is an electric four-wheel drive vehicle that drives the front wheels 1FL, 1FR and the rear wheels 1RL, 1RR with individual electric motors. The operating states of these front motor 2F and rear motor 2R are controlled according to a command signal from the motor controller 11. These front motor 2F and rear motor 2R are power-operated by converting DC power from a driving battery (not shown) into three-phase AC power by an inverter (not shown) and applying it, whereby driving forces (driving torques) are applied to the front wheels 1FL, 1FR and the rear wheels 1RL, 1RR. Further, when the front motor 2F and the rear motor 2R are regeneratively operated, braking forces (braking torques) are applied to the front wheels 1FL, 1FR and the rear wheels 2RL, 2RR. By adjusting the applied power or regenerative power to the front motor 2F and the rear motor 2R with an inverter, the operating states of the front motor 2F and the rear motor 2R, for example, the driving torque and the braking torque can be adjusted. The driving torque and the braking torque of the front motor 2F and the rear motor 2R by the inverter can be controlled according to a command signal from the motor controller 11. That is, the front motor 2F and the rear motor 2R can respectively control the driving force or the braking force of each of the front wheels 1FL, 1FR and the rear wheels 1RL, 1RR according to a command signal from the motor controller 11. Note that the driving force or the braking force is collectively referred to as the driving and braking force. Therefore, the front motor 2F, the rear motor 2R, and the motor controller 11 constitute a driving and braking force control device for the front and rear wheels.

[0009] On the other hand, the front wheels 1FL and 1FR, which are the steering wheels, are configured to be steerable by an electric steering system 3. This electric steering system 3 has an electric motor 4 as an actuator, and for example, by rotating the steering shaft in both directions with the rotational driving force of this electric motor 4, it is possible to adjust the steering angle of the front wheels 1FL and 1FR and perform steering. Similar to a power steering system, the electric steering system 3 assists the steering force of the driver, and in autonomous driving, for example, it automatically controls the steering angle according to the shape of the road to ensure the vehicle's trajectory. In this electric steering system 3, the steering shaft is rotated by the electric motor 4, so the steering wheel is rotated when autonomous driving is performed. The steering force assistance and autonomous driving steering by this electric steering system 3 are controlled by command signals from the steering controller 12. For example, when a target steering angle θ is commanded from the driver assistance controller 13 (described later), a drive signal is applied to the electric motor 4 to achieve this target steering angle θ, and the steering shaft (steering wheel) is rotated while the front wheels 1FL and 1FR are steered to achieve this target steering angle θ. In other words, the electric steering device 3 and the steering controller 12 constitute a steering angle control device that automatically controls the steering angle of the vehicle.

[0010] This vehicle is equipped with an accelerator pedal position sensor 5 for detecting the amount the accelerator pedal is pressed, and a brake pedal force sensor 6 for detecting the amount the brake pedal is pressed (pressure). The vehicle is also equipped with a steering angle sensor 7 for detecting the amount of steering wheel movement (including direction of movement). Furthermore, the vehicle is equipped with a yaw rate sensor 8 for detecting the yaw rate occurring in the vehicle, and wheel speed sensors 16 for detecting the rotational speed (wheel speed) of the front wheels 1FL, 1FR and the rear wheels 1RL, 1RR. In addition, the vehicle is equipped with an automatic driving switch 9 for selecting the aforementioned automatic driving mode. When this automatic driving switch 9 is turned on and the vehicle enters automatic driving mode, the vehicle's control devices operate in response to control commands from the driver assistance controller 13, thereby realizing automatic driving. To enable this automatic driving, the vehicle is equipped with at least an environmental detection device 14 for detecting the road ahead of the vehicle, and an environmental recognition device 15 for calculating the shape of the road by detecting, for example, white lines from the road ahead detected by at least the environmental detection device 14. Examples of environmental detection devices 14 include cameras, radar, and various sensors as imaging devices. The environmental recognition device 15 is a controller that calculates the environmental conditions near the vehicle through computational processing based on the environmental information detected by the environmental detection device 14. Therefore, the environmental recognition device 15 is assigned to perform some of the functions of the automatic driving control described later, for example, the front wheel steering angle δ according to the shape of the road. adas It is also possible to have it calculate the result.

[0011] The driver assistance controller 13 is an electronic control unit (ECU) that outputs control commands to assist driving using detection signals from various sensors as described above. Therefore, this driver assistance controller 13 is equipped with a computer system that has advanced computing capabilities. This computer system, like well-known computer systems, is configured to include a processor 13a that exhibits advanced computing capabilities and a storage device 13b that stores information such as programs and sensor signals. The processor 13a is composed of, for example, a CPU (Central Processing Unit) or an MPU (Micro-Processing Unit). The storage device 13b is composed of a semiconductor storage device, a magnetic storage device, and an optical storage device. The storage device 13b may further include registers, cache memory, and memory used as main memory. The computing processes performed by the driver assistance controller 13 are realized, for example, by the processor 13a executing a computer program stored in the storage device 13b of the driver assistance controller 13. Alternatively, the computing processes performed by the driver assistance controller 13 may be executed by functional logic circuits set in a general-purpose semiconductor integrated circuit. For example, the driver assistance controller 13 may have programmable logic devices such as a field-programmable gate array. The various controllers mentioned above are also equipped with a computer system similar to that of the driver assistance controller 13. Furthermore, in this embodiment, the following automated driving logic is executed by the driver assistance controller 13, but as mentioned above, for example, a portion of the automated driving logic may be executed by individual controllers.

[0012] Figure 2 shows the logic of the calculation process performed by the motor controller 11, which calculates the command values ​​for the front motor torque and rear motor torque to be requested from the front motor 2F and rear motor 2R, and outputs a command signal. In this calculation process, the target front motor torque and target rear motor torque are calculated by the target front and rear motor torque calculation unit 17. On the other hand, when the driver assistance controller 13 outputs a front motor torque correction value and a rear motor torque correction value during autonomous driving, the front motor torque command value is output as the value obtained by adding the front motor torque correction value to the target front motor torque, and the rear motor torque command value is output as the value obtained by adding the rear motor torque correction value to the target rear motor torque. Therefore, the target front motor torque and target rear motor torque are reference values ​​that take into account the front motor torque correction value and the rear motor torque correction value. In this embodiment, the driver-requested driving force requested by the driver is calculated based on the amount of accelerator pedal depression detected by the accelerator pedal opening sensor 5 and the amount of brake pedal depression (pitch force) detected by the brake pedal force sensor 6. Filtering may be applied as appropriate during the calculation. The driving force portion of this driver-required braking force corresponds to the driving torque obtained by operating the front motor 2F and rear motor 2R in power mode. Similarly, the braking force portion of this driver-required braking force corresponds to the braking torque obtained by operating the front motor 2F and rear motor 2R in regenerative mode. The driver-required braking force calculated and set in this manner is distributed to the front axle 10F and rear axle 10R, for example, according to a predetermined braking force distribution ratio between the front and rear wheels, and the target front motor torque for the front motor 2F to achieve the front axle braking force and the target rear motor torque for the rear motor 2R to achieve the rear axle braking force are calculated and set. The braking force distribution ratio between the front and rear wheels can be set to, for example, 50:50 so that the driver-required braking force is equally divided between the front axle 10F and the rear axle 10R. If the sum of the braking torques obtained by operating each motor in regenerative mode is less than the driver-required braking force, the deficiency may be compensated for by a hydraulic brake system or an electric brake system according to individual calculation processes not shown.

[0013] Next, an example of the calculation process performed within the driver assistance controller 13 will be explained using the flowchart in Figure 3. This calculation process is performed, for example, at a predetermined sampling period. First, in step S1, it is determined whether the automatic driving switch has been turned on and the system is in automatic driving mode. If it is in automatic driving mode, the system proceeds to step S2; otherwise, it returns to the previous step. In step S2, the system acquires the road information in front of the vehicle recognized by the environmental recognition device 15. Next, the system proceeds to step S3, where the wheel speeds Vw of the front wheels 1FL, 1FR and the rear wheels 1RL, 1RR detected by the wheel speed sensor 16 are read. Next, the system proceeds to step S4, where the vehicle's driving speed V is calculated using the wheel speeds Vw read in step S3, and the white lines are detected from the road information in front of the vehicle acquired in step S2 to calculate the radius of curvature R of the road. The driving speed V may be calculated, for example, from the average value of the wheel speeds Vw of all wheels, or from the average value of the remaining wheel speeds Vw after excluding wheel speeds Vw that deviate significantly from other wheel speeds Vw, i.e., wheel speeds Vw with a large slip ratio. Other calculation methods are also applicable. Next, proceed to step S5, where the target yaw rate γ is calculated from the travel speed V and the radius of curvature R of the travel path obtained in step S4. In this calculation of the target yaw rate, the lateral acceleration A is obtained by the following equation 1. Y Using this, the target yaw rate γ is calculated according to the following two equations. Next, proceeding to step S6, the target vehicle slip angle β is calculated according to the following three equations using the target yaw rate γ obtained in step S5. In the equations, m is the vehicle mass, I is the yaw radius of inertia, L is the wheelbase, L F L is the distance from the vehicle's center of gravity to the front axle 10F. R This is the distance from the vehicle's center of gravity to the rear axle 10R, K F This is the equivalent cornering power of the front wheel 1FL, 1FR, K R This represents the equivalent cornering power for the rear wheels 1RL and 1RR. Furthermore, the stability factor A in equations 6 and 7 is given by equation 8 below. Also, α in equation 3 is the compatibility constant.

[0014]

number

[0015] Note that, as described above, when the front wheel steering angle δ adas is given by the environment recognition device 15, the target yaw rate γ is calculated according to the following formula (9) using this front wheel steering angle δ adas , and the target vehicle body slip angle β may be calculated according to the following formula (10) using the same front wheel steering angle δ adas . Note that d in formula (10) is a fitting constant.

Equation

Equation

[0016] Next, proceed to step S8, subtract the current vehicle body slip angle β R from the target vehicle body slip angle β to calculate the vehicle body slip angle difference Δβ. Next, proceed to step S9, and calculate the front motor torque correction value and the rear motor torque correction value according to individual arithmetic processing (not shown) using the vehicle body slip angle difference Δβ obtained in step S8. Specifically, first, determine whether the current vehicle body slip angle β R is outward (or inward) with respect to the target vehicle body slip angle β. That the current vehicle body slip angle β R is outward with respect to the target vehicle body slip angle β can be determined, for example, by the fact that the value obtained by subtracting the absolute value of the current vehicle body slip angle β R (absolute value) from the absolute value of the target vehicle body slip angle β is a positive value. And, with respect to the target vehicle body slip angle β, the current vehicle body slip angle β RIf the slip angle is outward, the reduction in front wheel braking force and the increase in rear wheel braking force are calculated according to the difference in vehicle body slip angle Δβ. These reductions in front wheel braking force and increases in rear wheel braking force should be set according to the so-called friction circle theory. This allows for the calculation of a front motor torque (decrease) correction value corresponding to the reduction in front wheel braking force and a rear motor torque (increase) correction value corresponding to the increase in rear wheel braking force. Furthermore, the current vehicle body slip angle β is used in relation to the target vehicle body slip angle β. R If the front wheel is facing inward, the increase in front wheel braking force and decrease in rear wheel braking force are calculated according to the vehicle body slip angle difference Δβ. These increases and decreases in front wheel braking force are also set according to the friction circle theory. This allows for the calculation of a front motor torque (increase) correction value corresponding to the increase in front wheel braking force and a rear motor torque (decrease) correction value corresponding to the decrease in rear wheel braking force. Note that either the front motor torque increase / decrease correction or the rear motor torque decrease / increase correction may be applied individually or both.

[0017] Next, we move to step S10 and determine the target front wheel (steering wheel) tire force (lateral force) F that satisfies the balance between the translational and rotational directions of a rigid body, assuming the vehicle body is a rigid body. YF The target front tire force F is calculated according to the following 15 formulas. YF and target rear tire force F YR The lateral (translational) force F of the vehicle is expressed as the sum of the following values. Y This is expressed by the following 13 equations using the target yaw rate γ and the target vehicle slip angle β. Furthermore, the moment M around the vertical axis (Z axis) (in the direction of rotation), which is the product of the yaw radius of inertia I and the yaw angular acceleration γ', is given by the target front wheel tire force F. YF and target rear tire force F YR These are expressed by the following 14 equations. These are used to express the target front wheel tire force F. YF Solving for this gives the following 15 equations, and substituting the target yaw rate γ and target vehicle slip angle β into this gives the target front tire force F YF You can obtain this.

number

[0018]

number

[0019] Next, the calculation process of the subprogram executed in step S12 of the calculation process in Figure 3 will be explained using the flowchart in Figure 4. In this calculation process, first, in step S21, it is determined whether the vehicle is traveling in a straight line and at a predetermined speed or higher. If the vehicle is traveling in a straight line and at a predetermined speed or higher, the process proceeds to step S22; otherwise, it proceeds to step S23. In step S22, the target steering angle θ is increased and the front motor torque is increased before proceeding to step S23. In step S23, it is determined whether the vehicle is turning and traveling at a predetermined speed or higher. If the vehicle is turning and at a predetermined speed or higher, the process proceeds to step S24; otherwise, it proceeds to step S25. In step S24, the target steering angle θ is decreased before proceeding to step S25. In step S25, it is determined whether the vehicle is steering to the outside of the turn on the road. If the vehicle is steering to the outside of the turn on the road, the process proceeds to step S26; otherwise, it returns to the starting position. In step S26, the target steering angle θ is increased before returning to the starting position. Furthermore, in steps S25 and S26, it is determined whether the vehicle is steering towards the inside of the turn on the road, and if it is steering towards the inside of the turn on the road, the target steering angle θ may be corrected to be smaller. In this calculation process, when the vehicle is traveling in a straight line and at a speed above a predetermined speed, the front motor torque is increased and the target steering angle θ is corrected to be larger. As a result, the vehicle tends to understeer slightly, while the steering wheel is turned significantly. Therefore, for example, when the vehicle is blown sideways by a crosswind and this must be corrected by autonomous driving, the large movement of the steering wheel makes it clear that the autonomous driving system is making a correction, increasing the sense of security. It is also possible to correct the target steering angle θ to be smaller at low speeds. In addition, when the vehicle is turning and traveling at a speed above a predetermined speed, the target steering angle θ is corrected to be smaller. As a result, when the vehicle is turning, the movement of the steering wheel by the autonomous driving system is reduced, making it less bothersome. Also, steering during minute trajectory corrections becomes less noticeable. Furthermore, when steering outwards during a turn, the target steering angle θ is significantly corrected, resulting in a smaller actual outward movement of the vehicle during the turn, thus increasing a sense of security.Similarly, when steering inward during a turn, the target steering angle θ is corrected to be smaller, causing the vehicle to orient itself in the direction of movement, thus increasing the sense of security.

[0020] Figure 5 shows the time-dependent changes in the vehicle slip angle (target vehicle slip angle β) and steering angle (target steering angle θ) when the target vehicle slip angle β during a turn is set small in the calculation process shown in Figure 3, and consequently the target steering angle θ is also set small. The dashed lines in the figure show the time-dependent changes in the target vehicle slip angle β that aligns the forward gaze position with the turning trajectory, and the target steering angle θ corresponding to that target vehicle slip ratio β. In both cases, the vehicle transitioned from a state of straight-line driving at 50 km / h under automatic driving to turning with a radius of curvature of 80 m after a predetermined time (1 second). As is clear from the figure, the target steering angle θ is set small because the target vehicle slip angle β shown by the solid line is set small. However, as mentioned above, because the target vehicle slip angle β is set small, the current vehicle slip angle β is smaller than the target vehicle slip angle β. R Because the steering is outward, for example, the rear motor torque is greatly corrected, causing the vehicle to have an oversteer tendency and correcting it inward. As a result, the forward gaze position coincides with the turning trajectory, and the target yaw rate γ is achieved. From this, it can be seen that frequent lateral movements of the steering wheel are suppressed when repeatedly making small left and right turns, reducing annoyance.

[0021] The above describes a driver assistance (autonomous driving) system according to an embodiment. However, the present invention is not limited to the configuration described in the above embodiment, and various modifications are possible within the scope of the gist of the present invention. For example, in the above embodiment, the slip angle that makes the vehicle position at the forward-looking position coincide with the position on the turning trajectory is set as the target vehicle body slip angle, and the front and rear motor torques are corrected or the target steering angle θ is set to achieve this target vehicle body slip angle. Alternatively, the target vehicle body slip angle may be set inward when the vehicle speed is in the low-speed range and outward when it is in the high-speed range. That is, in a typical vehicle, as shown by the dashed line in Figure 6, the actual vehicle body slip angle that occurs in the vehicle is outward (+) in the low-speed range and inward (-) in the high-speed range, and this actual vehicle body slip angle is the deviation from the turning trajectory of the vehicle at the forward-looking position. Therefore, as shown by the solid line in Figure 6, by setting the target vehicle slip angle inward in the low-speed range and outward in the high-speed range, it is possible to return the vehicle position at the forward-looking position to the turning trajectory. In this case, for example, by increasing the inward amount of the target vehicle slip angle as the vehicle speed decreases and increasing the outward amount as the vehicle speed increases, the positional deviation can be corrected more accurately. Also, if the actual vehicle slip angle is known in advance, the same effect can be obtained by setting the target vehicle slip angle so that the actual vehicle slip angle is small (in absolute value).

[0022] Furthermore, in the above embodiment, the braking and driving forces of the front and rear wheels were controlled by the front wheel motor torque and the rear wheel motor torque (including powering and regenerative braking). However, the braking and driving force control method and control device of the present invention can also be applied to vehicles in which the engine's driving force is transmitted to the front and / or rear wheels, and the braking force of the front and rear wheels is adjusted by a brake system using fluid pressure (hydraulic pressure) or a motor. Of these, the driving force corresponds to the motor torque during powering, and the braking force corresponds to the motor torque during regenerative braking, so the driving force can be controlled by the engine and the braking force by the brake system. Furthermore, the turning radius of the vehicle, depending on the shape of the road in front of the vehicle, may be any physical quantity that represents the target trajectory of the vehicle, such as the target yaw rate, target yaw rate deviation, target curvature, yaw angle deviation, or lateral position deviation, in addition to the actual radius of curvature R of the road.

[0023] Thus, in this embodiment, the system includes a steering angle control device for controlling the steering angle of the vehicle, a braking force control device for controlling the braking force of the front and rear wheels of the vehicle, and a driving support controller 13 that calculates a target steering angle for the steering angle control device and target braking forces for the front and rear wheels for the braking force control device. The driving support controller 13 calculates a target yaw rate γ from the half-curve radius R of the road according to the shape of the road in front of the vehicle, calculates a target vehicle body slip angle β that matches the forward gaze position calculated from the forward gaze time and the vehicle's speed V to a position on the turning trajectory obtained from the target yaw rate γ and the speed V, calculates a front motor torque correction value and a rear motor torque correction value (target braking force of the front and rear wheels) according to the target vehicle body slip angle β, and calculates a target front wheel (steering wheel) tire force F that satisfies the balance between the translational direction and the rotational direction of the rigid body from the target yaw rate γ and the target vehicle body slip angle β. YF The target steering wheel tire force F is calculated. YF This calculates the target steering angle θ that satisfies the tire force of the steering wheel in a two-wheeled model. This makes it possible to increase or decrease the steering angle during autonomous driving while ensuring the vehicle's trajectory is maintained.

[0024] Furthermore, the target steering angle is set larger when the target vehicle slip angle is larger than the actual slip angle, and smaller when the target vehicle slip angle is smaller than the actual slip angle. This allows the steering angle (target steering angle) to be increased or decreased while maintaining the driving trajectory using the braking and driving force control device during autonomous driving. Furthermore, by significantly correcting the target steering angle when the driving speed is above a predetermined value and the vehicle is traveling in a straight line, the large movement of the steering wheel indicates that the autonomous driving system is correcting the driving trajectory, which increases the sense of security. Furthermore, by correcting the target steering angle to a smaller value when the driving speed is above a predetermined value and the vehicle is turning, the movement of the steering wheel by the autonomous driving system is reduced when the vehicle is turning, making it less irritating to the driver, and also making it harder to detect steering during minute trajectory corrections. Furthermore, when steering towards the outside of a turn, the target steering angle is corrected to be larger than when steering towards the inside of the turn. This reduces the actual outward movement of the vehicle during the turn, and also directs the vehicle's body in the direction of movement towards the inside of the turn, both of which increases the sense of security. [Explanation of Symbols]

[0025] 1FL, 1FR…Front wheels, 1RL, 1RR…Rear wheels, 2F…Front motor, 2R…Rear motor, 3…Electric steering system, 4…Electric motor, 5…Accelerator position sensor, 6…Brake pedal force sensor, 7…Steering angle sensor, 8…Yaw rate sensor, 9…Automatic driving switch, 11…Motor controller, 12…Steering controller, 13…Driver assistance controller (controller), 14…Environment detection device, 15…Environment recognition device, 16…Wheel speed sensor

Claims

1. A driver assistance method that automatically controls the steering angle of a vehicle, A steering angle control device for controlling the steering angle of the vehicle, A braking and driving force control device that controls the braking and driving forces of the front and rear wheels of the vehicle, The system includes a controller that calculates a target steering angle for the steering angle control device and target braking and driving forces for the front and rear wheels for the braking and driving force control device, The controller is characterized by calculating a target yaw rate from the turning radius of the vehicle according to the shape of the road in front of the vehicle, calculating a target vehicle slip angle that makes the forward gaze position, calculated from the forward gaze time and the vehicle's travel speed, coincide with a position on the turning trajectory obtained from the target yaw rate and the travel speed, calculating target braking and driving forces for the front and rear wheels according to the target vehicle slip angle, calculating a target steering wheel tire force that satisfies the balance between the translational and rotational directions of a rigid body from the target yaw rate and the target vehicle slip angle, and calculating a target steering angle that satisfies the target steering wheel tire force for a two-wheel model.

2. The driving assistance method according to claim 1, characterized in that the target steering angle is calculated to be large when the target vehicle slip angle is large compared to the actual slip angle, and the target steering angle is calculated to be small when the target vehicle slip angle is small compared to the actual slip angle.

3. The driving assistance method according to claim 1, characterized in that the target steering angle is greatly corrected when the driving speed is above a predetermined value and the vehicle is moving in a straight line.

4. The driving assistance method according to claim 1, characterized in that the target steering angle is corrected to be smaller when the driving speed is above a predetermined value and the vehicle is turning.

5. The driving assistance method according to claim 1, characterized in that when the steering is directed toward the outside of the turn on the aforementioned road, the target steering angle is corrected to be larger than when the steering is directed toward the inside of the turn.

6. A driver assistance method that automatically controls the steering angle of a vehicle, A steering angle control device for controlling the steering angle of the vehicle, A braking and driving force control device that controls the braking and driving forces of the front and rear wheels of the vehicle, A driver assistance device comprising: a controller for calculating a target steering angle for the steering angle control device and target braking and driving forces for the front and rear wheels for the braking and driving force control device, the controller calculating a target yaw rate from the turning radius of the vehicle according to the shape of the road in front of the vehicle, calculating a target vehicle body slip angle that makes the forward gaze position, calculated from the forward gaze time and the vehicle's travel speed, coincide with a position on the turning trajectory obtained from the target yaw rate and the travel speed, calculating the target braking and driving forces for the front and rear wheels according to the target vehicle body slip angle, calculating a target steering wheel tire force that satisfies the balance between the translational direction and the rotational direction of a rigid body from the target yaw rate and the target vehicle body slip angle, and calculating a target steering angle that satisfies the target steering wheel tire force to satisfy the steering wheel tire force of a two-wheel model.

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