Steering control system

• US 20060200289A1
• Filed: 02/28/2006
• Published: 09/07/2006
• Est. Priority Date: 03/01/2005
• Status: Active Grant

• Current Assignee: Nissan Motor Co., Ltd.
• Original Assignee: Nissan Motor Co., Ltd.
• Inventors: Eguchi, Takaaki, Kubokawa, Noriki, Chino, Naotaka, Suzuki, Taku
• Granted Patent: US 7,664,584 B2
• Time in Patent Office: Days
• US Class Current: 701/41
• CPC Class Codes: B62D 5/003 Backup systems, e.g. for manual steering B62D5/30 takes precedence
• CPC Class Codes: B62D 5/006 power actuated
• CPC Class Codes: B62D 5/0463 calculating assisting torque from the motor based on driver input
• CPC Class Codes: B62D 6/008 Control of feed-back to the steering input member, e.g. simulating road feel in steer-by-wire applications

Abstract

In a steering control system comprising a steering component having a steering wheel and a steering reaction force actuator, a turning component having vehicle turning wheels and a turning actuator, and a backup mechanism for alternately mechanically separating and linking the steering and turning components, there is provided a steer-by-wire control unit selectively separated from the backup mechanism for executing steer-by-wire control of the turning actuator to a turning angle corresponding to the steering condition and control of the steering reaction force actuator for imparting steering reaction force corresponding to the turning condition, a steering assistance control unit selectively linked to the backup mechanism for executing steering assistance control for at least one of the steering reaction force actuator and the turning actuator, and a control switching unit for controlling a shift, upon attainment of predetermined conditions, between control by the steer-by-wire control unit and control by the steering assistance control unit. The control switching unit, upon the shift of control, between the time of a separation/linkage command to the backup mechanism and the time of completion of separation/linkage, selectively sets as the correction amount the variation equivalence of the turning torque to be applied to the turning wheels of a vehicle after the completion and selectively executes correction of turning torque.

Claims

1. A steering apparatus comprising:

a steering wheel;

turning wheels that are selectively turned according to a steering angle of the steering wheel;

a backup mechanism for alternately mechanically separating and linking the steering wheel and the turning wheels;

a turning actuator, linked to the turning wheels, that turns the turning wheels according to the steering angle of the steering wheel;

a steering reaction force actuator, linked to the steering wheel, for assigning a reaction torque to the steering wheel according to a turning torque assigned to the turning wheels by the turning actuator; and

a control unit configured to control the backup mechanism, the steering reaction force actuator, and the turning actuator,

wherein the control unit carries out a steer-by wire control, in which when the steering wheel and the turning wheels are mechanically separated from each other by the backup mechanism so that the turning wheels are turned by the turning actuator according to the steering angle, the reaction force torque is assigned to the steering wheel by the steering reaction force actuator according to the turning torque,

a steering assistance control in which when the steering wheel and the turning wheels are mechanically linked by the backup mechanism so that a steering torque inputted from the steering wheel is transferred to the turning wheels via the backup mechanism, an assistance force is assigned so as to assist turning of the turning wheels according to steering torque inputted from the steering wheel by at least one of the steering reaction force actuator and the turning actuator,

a switching control in which the steer-by wire control and the steering assistance control are alternatively switched over when a predetermined condition is met, and

a correction control in which the turning torque assigned to the turning wheels by the turning actuator is corrected according to the steering torque transferred to the turning wheels via the backup mechanism, when the steer-by wire control is switched to the steering assistance control, or the steering assistance control is switched to the steer-by wire control.

2. The steering apparatus according to claim 1, wherein when the steer-by wire control is switched to the steering assistance control, the turning actuator carries out the correction control so as to reduce the turning torque assigned to the turning wheels by the turning actuator.

3. The steering apparatus according to claim 1, further including a steering angular velocity sensor that detects a steering angular velocity of the steering wheel, wherein the control unit is configured so that a correction amount to the turning torque applied to the turning wheels by the turning actuator is reduced as the steering angular velocity detected by the steering angular velocity sensor is larger.

4. The steering apparatus according to claim 1, wherein the control unit is configured so that the turning torque applied to the turning wheels by the turning actuator is increased according to the steering torque transferred to the turning wheels via the backup mechanism.

5. The steering apparatus according to claim 4, wherein the control unit is configured so that the reaction torque applied to the steering wheel by the steering reaction actuator is increased when the steering assistance control is switched to the steer-by wire control, according to the correction amount to the turning torque applied to the turning wheel by the turning actuator.

6. The steering apparatus according to claim 5, further including a steering angular velocity sensor that detects a steering angular velocity of the steering wheel, wherein the control unit is configured so that a correction amount to the turning torque applied to the turning wheels is increased as the steering angular velocity detected by the steering angular velocity sensor is larger.

7. The steering apparatus according to claim 1, wherein the steering reaction force actuator includes a steering angle sensor, an encoder, a torque sensor, a Hall IC and a reaction force motor.

8. The steering apparatus according to claim 7, wherein the steering angle sensor is provided in a duplex system of two torque sensors.

9. The steering apparatus according to claim 8, wherein the two torque sensors are disposed between the steering wheel and the torque sensor.

10. The steering apparatus according to claim 7, wherein the steering angle sensor employs an absolute-type resolver.

11. The steering apparatus according to claim 7, wherein the torque sensor is provided in a duplex system of first and second torque sensors.

12. The steering apparatus according to claim 7, wherein the torque sensor is arranged between the steering angle sensor and the reaction force motor.

13. The steering apparatus according to claim 1, further including a steering torque sensor for detecting steering torque input from the steering wheel, and wherein the correction control includes a steering torque correction component for setting a greater steering torque reduction correction value to the extent that the detected steering torque increases.

14. The steering apparatus according to claim 13, further including a rack axial force change sensor for detecting rack axial force change of the steering torque reduction correction value to the extent that the rack axial force change is in the increasing direction, and increases the steering torque reduction correction value to the extent that the rack axial force change value is in the decreasing direction.

15. The steering apparatus according to claim 14, including a steering angle detection sensor for detecting the steering angle of the steering component, and wherein the turning torque correction component selectively decreases the steering torque reduction correction value to the extent that the steering angle detection value increases.