STEERING SYSTEM AND CONTROL METHOD FOR STEERING SYSTEM

• US 20200130728A1
• Filed: 10/24/2019
• Published: 04/30/2020
• Est. Priority Date: 10/30/2018
• Status: Active Grant

• Current Assignee: Jtekt Corporation (Toyota Motor Corporation)
• Original Assignee: Toyota Jidosha Kabushiki Kaisha (Toyota Motor Corporation)
• Inventors: TAKASHIMA, Toru, NAKANO, Yusuke
• Granted Patent: US 11,518,431 B2
• Time in Patent Office: Days
• CPC Class Codes: B62D 15/021 Determination of steering angle
• CPC Class Codes: B62D 5/0457 characterised by control features of the drive means as such
• CPC Class Codes: B62D 6/002 computing target steering angles for front or rear wheels B62D7/159 takes precedence

Abstract

A steering system is configured such that a ratio of a turning angle change amount with respect to a steering angle change amount in a first steering angle area is larger than the ratio of the turning angle change amount with respect to the steering angle change amount in a second steering angle area, and a steering angle in the second steering angle is smaller than the steering angle of the first steering angle area. An electronic control unit of the steering system sets a delay degree of a change in turning angle with respect to a change in steering angle in the first steering angle area to be larger than the delay degree of the change in turning angle with respect to the change in steering angle in the second steering angle area regardless of a turning-over operation or a turning-back operation.

Claims

1. A steering system comprising

an electronic control unit configured to:

set a ratio of a turning angle change amount with respect to a steering angle change amount in a first steering angle area to be larger than the ratio of the turning angle change amount with respect to the steering angle change amount in a second steering angle area, a steering angle of the second steering angle area being smaller than the steering angle of the first steering angle area; and

perform a first process of setting a delay degree of a change in turning angle with respect to a change in steering angle in the first steering angle area to be larger than the delay degree of the change in turning angle with respect to the change in steering angle in the second steering angle area regardless of a turning-over operation or a turning-back operation.

2. The steering system according to claim 1, wherein

the steering system is configured such that the ratio of the turning angle change amount with respect to the steering angle change amount continuously changes from the second steering angle area to the first steering angle area, and

the electronic control unit is configured such that the delay degree of the change in turning angle with respect to the change in steering angle continuously changes from the second steering angle area to the first steering angle area in the first process.

3. The steering system according to claim 2, wherein

the steering system is configured such that the ratio of the turning angle change amount with respect to the steering angle change amount continuously increases from the second steering angle area to the first steering angle area, and

the electronic control unit is configured such that the delay degree of the change in turning angle with respect to the change in steering angle continuously increases from the second steering angle area to the first steering angle area in the first process.

4. The steering system according to claim 1, wherein

the steering system is configured such that the ratio of the turning angle change amount with respect to the steering angle change amount in a first vehicle speed area is larger than the ratio of the turning angle change amount with respect to the steering angle change amount in a second vehicle speed area, a vehicle speed of the second vehicle speed area being higher than the vehicle speed of the first vehicle speed area, and

the electronic control unit is configured to further perform a second process of setting the delay degree of the change in turning angle with respect to the change in steering angle in the first vehicle speed area to be larger than the delay degree of the change in turning angle with respect to the change in steering angle in the second vehicle speed area.

5. The steering system according to claim 4, wherein

the steering system is configured such that the ratio of the turning angle change amount with respect to the steering angle change amount continuously changes from the second vehicle speed area to the first vehicle speed area, and

the electronic control unit is configured such that the delay degree of the change in turning angle with respect to the change in steering angle continuously changes from the second vehicle speed area to the first vehicle speed area in the second process.

6. The steering system according to claim 5, wherein

the steering system is configured such that the ratio of the turning angle change amount with respect to the steering angle change amount continuously increases from the second vehicle speed area to the first vehicle speed area, and

the electronic control unit is configured such that the delay degree of the change in turning angle with respect to the change in steering angle continuously increases from the second vehicle speed area to the first vehicle speed area in the second process.

7. The steering system according to claim 1, further comprising:

a steering mechanism that turns a steered wheel by a turning motor while not being mechanically connected to a steering member, wherein

the electronic control unit is configured to perform a process of converting the steering angle of the steering member into a target turning angle, a process of obtaining a correction target turning angle by passing the target turning angle through a low-pass filter, and a process of controlling the turning motor according to the correction target turning angle, and

the first process includes a process of setting a cut-off frequency of the low-pass filter in the first steering angle area to be smaller than the cut-off frequency of the low-pass filter in the second steering angle area.

8. The steering system according to claim 1, further comprising:

a steering mechanism that turns a steered wheel by a turning motor while not being mechanically connected to a steering member, wherein

the electronic control unit is configured to perform a process of converting the steering angle of the steering member into a target turning angle, a process of obtaining a correction target turning angle by passing the target turning angle through a rate limiter, and a process of controlling the turning motor according to the correction target turning angle, and

the first process includes a process of setting a limitation of the rate limiter in the first steering angle area to be weaker than the limitation of the rate limiter in the second steering angle area.

9. The steering system according to claim 4, further comprising:

a steering mechanism that turns a steered wheel by a turning motor while not being mechanically connected to a steering member, wherein

the electronic control unit is configured to perform a process of converting the steering angle of the steering member into a target turning angle, a process of obtaining a correction target turning angle by passing the target turning angle through a low-pass filter, and a process of controlling the turning motor according to the correction target turning angle, and

the second process includes a process of setting a cut-off frequency of the low-pass filter in the first vehicle speed area to be smaller than the cut-off frequency of the low-pass filter in the second vehicle speed area.

10. The steering system according to claim 4, further comprising:

a steering mechanism that turns a steered wheel by a turning motor while not being mechanically connected to a steering member, wherein

the electronic control unit is configured to perform a process of converting the steering angle of the steering member into a target turning angle, a process of obtaining a correction target turning angle by passing the target turning angle through a rate limiter, and a process of controlling the turning motor according to the correction target turning angle, and

the second process includes a process of setting a limitation of the rate limiter in the first vehicle speed area to be weaker than the limitation of the rate limiter in the second vehicle speed area.

11. A control method for a steering system comprising:

setting a ratio of a turning angle change amount with respect to a steering angle change amount in a first steering angle area to be larger than the ratio of the turning angle change amount with respect to the steering angle change amount in a second steering angle area by an electronic control unit, a steering angle in the second steering angle area being smaller than the steering angle in the first steering angle area; and

setting a delay degree of a change in turning angle with respect to a change in steering angle in the first steering angle area to be larger than a delay degree of a change in turning angle with respect to a change in steering angle in the second steering angle area by the electronic control unit regardless of a turning-over operation or a turning-back operation.