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EP-4506223-B1 - TRAVEL ASSISTANCE METHOD AND TRAVEL ASSISTANCE DEVICE

EP4506223B1EP 4506223 B1EP4506223 B1EP 4506223B1EP-4506223-B1

Inventors

  • Tsuda, Fumiya

Dates

Publication Date
20260506
Application Date
20220405

Claims (9)

  1. A travel assistance method comprising: detecting (S1) vehicle speed (V) of a vehicle (1); detecting (S1) a steering angle (θs(s)) of a steering wheel; setting (S1) a required braking/driving force according to an operation amount (Br, Ac) of an accelerator pedal or a brake pedal operated by a driver; setting (S2) a target value of a vehicle body slip angle (β), the vehicle body slip angle (β) being an angle from a longitudinal direction (db) of a vehicle body to a travel direction (dd) of the vehicle (1), as a target slip angle (βt(s)), based on the vehicle speed (V) and the steering angle (θs(s)); estimating (S3) or detecting an actual slip angle (βa(s)) based on at least the vehicle speed (V) and the steering angle (θs(s)), the actual slip angle (βa(s)) being an actual vehicle body slip angle (β); setting (S4 - S6) a target braking/driving force by, when a sign of the vehicle body slip angle (β) rotating in a turning direction of the vehicle (1) is defined as positive and a sign of the vehicle body slip angle (β) rotating in an opposite direction to the turning direction is defined as negative, correcting the required braking/driving force in such a manner as to increase a braking force for both of a rear right wheel and a rear left wheel or increase a driving force for both of the rear right wheel and the rear left wheel or reduce a braking force generated on both of a front right wheel and a front left wheel or reduce a driving force generated on both of the front right wheel and the front left wheel when the actual slip angle (βa(s)) is larger than the target slip angle (βt(s)), and correcting the required braking/driving force in such a manner as to reduce a braking force for both of the rear right wheel and the rear left wheel or reduce a driving force for both of the rear right wheel and the rear left wheel or increase a braking force generated on both of the front right wheel and the front left wheel or increase a driving force generated on both of the front right wheel and the front left wheel when the actual slip angle (βa(s)) is smaller than the target slip angle (βt(s)); and generating the target braking/driving force in the vehicle (1); characterized by detecting a lateral acceleration of the vehicle (1), wherein the target value of the vehicle body slip angle (β) is set (S2) further based on the lateral acceleration such that the target slip angle (βt(s)) is set to be smaller when the lateral acceleration is large than when the lateral acceleration is small.
  2. The travel assistance method according to claim 1, wherein the travel assistance method sets the target braking/driving force by correcting the required braking/driving force in such a manner as to increase a braking force for both of the rear right wheel and the rear left wheel or increase a driving force for both of the rear right wheel and the rear left wheel and reduce a braking force generated on both of the front right wheel and the front left wheel or reduce a driving force generated on both of the front right wheel and the front left wheel when the actual slip angle (βa(s)) is larger than the target slip angle (βt(s)), and correcting the required braking/driving force in such a manner as to reduce a braking force for both of the rear right wheel and the rear left wheel or reduce a driving force for both of the rear right wheel and the rear left wheel and increase a braking force generated on both of the front right wheel and the front left wheel or increase a driving force generated on both of the front right wheel and the front left wheel when the actual slip angle (βa(s)) is smaller than the target slip angle (βt(s)).
  3. The travel assistance method according to claim 2, wherein when a sign of the required braking/driving force, the required braking/driving force being a driving force, is defined as positive and a sign of the required braking/driving force, the required braking/driving force being a braking force, is defined as negative, the travel assistance method sets a smaller value of the target slip angle (βt(s)) when the required braking/driving force is large than when the required braking/driving force is small.
  4. The travel assistance method according to claim 3, wherein the travel assistance method sets a smaller value of the target slip angle (βt(s)) when the required braking/driving force is a driving force than when the required braking/driving force is a braking force.
  5. The travel assistance method according to any one of claims 1 to 4, wherein the travel assistance method sets a larger value of the target slip angle (βt(s)) when the vehicle speed (V) is high than when the vehicle speed (V) is low.
  6. The travel assistance method according to any one of claims 1 to 5 comprising: changing a response characteristic of the vehicle (1) responding to driving operation performed by the driver, based on a selection input from driver; and setting a larger value of the target slip angle (βt(s)) when the response characteristic is high than when the response characteristic is low.
  7. The travel assistance method according to any one of claims 1 to 6 comprising: calculating a target slip angular velocity, the target slip angular velocity being a differential value of the target slip angle (βt(s)), and an actual slip angular velocity, the actual slip angular velocity being a differential value of the actual slip angle (βa(s)); and correcting the required braking/driving force in such a manner as to increase a braking force for both of the rear right wheel and the rear left wheel or increase a driving force for both of the rear right wheel and the rear left wheel or reduce a braking force generated on both of the front right wheel and the front left wheel or reduce a driving force generated on both of the front right wheel and the front left wheel when the actual slip angular velocity is larger than the target slip angular velocity and correcting the required braking/driving force in such a manner as to reduce a braking force for both of the rear right wheel and the rear left wheel or reduce a driving force for both of the rear right wheel and the rear left wheel or increase a braking force generated on both of the front right wheel and the front left wheel or increase a driving force generated on both of the front right wheel and the front left wheel when the actual slip angular velocity is smaller than the target slip angular velocity.
  8. The travel assistance method according to any one of claims 1 to 6 comprising: setting a target yaw rate, based on the steering angle (θs(s)) and the vehicle speed (V); detecting an actual yaw rate, the actual yaw rate being an actual yaw rate generated in the vehicle (1); and setting a target braking/driving force by correcting the required braking/driving force in such a manner as to increase a braking force for both of the rear right wheel and the rear left wheel or increase a driving force for both of the rear right wheel and the rear left wheel or reduce a braking force generated on both of the front right wheel and the front left wheel or reduce a driving force generated on both of the front right wheel and the front left wheel when the actual yaw rate is smaller than the target yaw rate.
  9. A travel assistance device (10) comprising: a vehicle speed sensor (11) configured to detect vehicle speed (V) of a vehicle (1); a steering angle sensor (12) configured to detect a steering angle (θs(s)) of a steering wheel; a controller (18) configured to set a required braking/driving force according to an operation amount of an accelerator pedal or a brake pedal operated by a driver, set a target value of a vehicle body slip angle (β), the vehicle body slip angle (β) being an angle from a longitudinal direction (db) of a vehicle body to a travel direction (dd) of the vehicle (1), as a target slip angle (βt(s)), based on the vehicle speed (V) and the steering angle (θs(s)), estimate or detect an actual slip angle (βa(s)) based on at least the vehicle speed (V) and the steering angle (θs(s)), the actual slip angle (βa(s)) being an actual vehicle body slip angle (β), and set a target braking/driving force by, when a sign of the vehicle body slip angle (β) rotating in a turning direction of the vehicle (1) is defined as positive and a sign of the vehicle body slip angle (β) rotating in an opposite direction to the turning direction is defined as negative, correcting the required braking/driving force in such a manner as to increase a braking force for both of a rear right wheel and a rear left wheel or increase a driving force for both of the rear right wheel and the rear left wheel or reduce a braking force generated on both of a front right wheel and a front left wheel or reduce a driving force generated on both of the front right wheel and the front left wheel when the actual slip angle (βa(s)) is larger than the target slip angle (βt(s)), and correcting the required braking/driving force in such a manner as to reduce a braking force for both of the rear right wheel and the rear left wheel or reduce a driving force for both of the rear right wheel and the rear left wheel or increase a braking force generated on both of the front right wheel and the front left wheel or increase a driving force generated on both of the front right wheel and the front left wheel when the actual slip angle (βa(s)) is smaller than the target slip angle (βt(s)); and a driving force source (23) or a braking device (22) configured to generate the target braking/driving force in the vehicle (1); characterized in that the travel assistant device (10) further comprising: an acceleration sensor (15) configured to detect lateral acceleration of the vehicle), wherein the set target value of the vehicle body slip angle (β) is further based on the lateral acceleration such that the target slip angle (βt(s)) is set to be smaller when the lateral acceleration is large than when the lateral acceleration is small.

Description

The present invention relates to a travel assistance method and a travel assistance device. In PTL 1 described below, a torque control device that, in order to increase turning performance, increases a torque distribution to the front wheel side when an actual yaw rate is larger than a target yaw rate and increases a torque distribution to the rear wheel side when the actual yaw rate is smaller than the target yaw rate is described. CN 112 752 691 A describes a centroid slip angle used to assess vehicle stability during turning, and a corrective yaw moment generated based on a comparison between a target and an actual centroid slip angle. The yaw moment being applied by adjusting front-to-rear driving torque distribution to improve steering stability. Document US 2022/080838 A1 also discloses a method for calculating and applying a motor control amount in consideration of handling performance of an electric vehicle. PTL1: JP H03-70633 A Although a driver can achieve a desired yaw rate by operating a steering wheel, the driver cannot simultaneously achieve a desired yaw rate and a desired vehicle body slip angle. When the vehicle body slip angle becomes excessive or insufficient, the driver is influenced by a difference of a line of sight from a travel direction of a vehicle. Thus, there are some cases where the driver steers the steering wheel more than necessary or the amount of steering is insufficient. As a result, it sometimes becomes difficult to perform steering operation to cause the vehicle to turn along a desired travel line. An object of the present invention is to facilitate steering operation to cause a vehicle to turn along a desired travel line. This is achieved by the independent claims. The dependent claims describe advantageous embodiments. According to an aspect of the present invention, it is possible to facilitate steering operation to cause a vehicle to turn along a desired travel line. The object and advantages of the invention will be realized and attained by means of the elements and combinations particularly pointed out in the claims. It is to be understood that both the foregoing general description and the following detailed description are exemplary and explanatory and are not restrictive of the invention. Brief Description of Drawings FIG. 1 is a schematic configuration diagram of an example of a travel assistance device of an embodiment;FIGS. 2A to 2D are explanatory diagrams of a vehicle body slip angle;FIGS. 3A to 3D are schematic diagrams illustrative of examples of a target slip angle and an actual slip angle when a vehicle turns to the left;FIGS. 4A to 4D are schematic diagrams illustrative of examples of the target slip angle and the actual slip angle when the vehicle turns to the right;FIG. 5 is a block diagram of an example of a functional configuration of a controller in FIG. 1;FIG. 6 is a block diagram of an example of a functional configuration of a braking/driving force correction value calculation unit;FIG. 7 is a flowchart of an example of a travel assistance method of the embodiment; andFIG. 8 is a block diagram of a variation of the functional configuration of the braking/driving force correction value calculation unit. Description of Embodiments (Configuration) FIG. 1 is a schematic configuration diagram of an example of a travel assistance device of an embodiment. A travel assistance device 10 adjusts a vehicle body slip angle of a vehicle 1 by controlling a braking/driving force for at least one of front wheels 2F (a front left wheel 2FL and a front right wheel 2FR) and rear wheels 2R (a rear left wheel 2RL and a rear right wheel 2RR) of the vehicle 1 and assists steering operation of the vehicle 1 performed by a driver. The travel assistance device 10 includes a wheel speed sensor 11, a steering angle sensor 12, a switch (SW) 13, a yaw rate sensor 14, an acceleration sensor 15, a brake sensor 16, an accelerator opening sensor 17, a controller 18, a drive controller 19, actuators 20, a turning device 21, a braking device 22, and a drive source 23. The wheel speed sensor 11 detects wheel speed Vw of the vehicle 1. For example, the wheel speed sensor 11 may detect an average value of wheel speeds of the front left wheel 2FL, the front right wheel 2FR, the rear left wheel 2RL, and the rear right wheel 2RR as the wheel speed Vw. The steering angle sensor 12 detects a steering angle θs(s) of a steering wheel. Herein, a sign of a steering angle θs(s) rotating leftward (counterclockwise) is defined as positive (plus), and a sign of a steering angle θs(s) rotating rightward (clockwise) is defined as negative (minus). The switch (SW) 13 is an operation element for accepting a selection input that a passenger (for example, the driver) of the vehicle 1 inputs to select a response characteristic of the vehicle 1 responding to driving operation performed by the driver. For example, the switch 13 may be a switch to switch driving modes that represent driving characteristic