Electric power steering apparatus, control device used in electric power steering apparatus, and control method

Patent metadata

Field	Value
Publication number	US-12084125-B2
Application number	US-202017632836-A
Country	US
Kind code	B2
Filing date	Aug 6, 2020
Priority date	Aug 9, 2019
Publication date	Sep 10, 2024
Grant date	Sep 10, 2024

Abstract

A processor acquires a steering torque detected by a steering torque sensor and a vehicle speed detected by a vehicle speed sensor, changes a gain and a phase to be applied to the steering torque in accordance with a steering frequency when a driver steers a steering wheel, determines a magnitude of an assist torque based on the steering torque to which the gain and the phase have been applied and the vehicle speed, and generates a torque command value to be used to control driving of the motor based on the determined assist torque.

First claim

The invention claimed is:

1. A control device usable in an electric power steering apparatus including a motor to control driving of the motor, the control device comprising:
a processor; and
a memory to store a program to control an operation of the processor; wherein
the program when executed by the processor causes the processor to:

acquire a steering torque detected by a steering torque sensor and a vehicle speed detected by a vehicle speed sensor;
change a gain and a phase to be applied to the steering torque in accordance with a steering frequency when a driver steers a steering wheel;
determine a magnitude of an assist torque based on the steering torque to which the gain and the phase have been applied and the vehicle speed; and
generate a torque command value to be used to control driving of the motor based on the determined assist torque;
a vehicle on which the electric power steering apparatus is mounted allows settings of different types of travel modes; and
the processor is programmed to perform control to vary each degree of change in the gain and the phase in accordance with the steering frequency depending on one of the types of the travel modes selected by the driver.

2. The control device according to claim 1 , wherein the types of travel modes include a first travel mode and a second travel mode; and the processor is programmed to:
perform control to increase the gain and lead the phase as the steering frequency increases when the first travel mode is selected; and
perform control to reduce the gain and delay the phase as the steering frequency increases when the second travel mode is selected.

3. The control device according to claim 1 , wherein
when f 1 is a frequency of a zero point and f 2 is a frequency of a pole, the processor is programmed to calculate first-order compensation (C(s)) in accordance with:

C
⁡
(
s
)

=

1

ω
1

⁢
s

+
1

1

ω
2

⁢
s

+
1

ω
1

=

1

2
⁢
π
⁢

f
1

⁢

ω
2

=

1

2
⁢
π
⁢

f
2

;

 and
change the gain and the phase using the first-order compensation C(s).

4. The control device according to claim 3 , wherein the processor is programmed to change values of the frequency f 1 of the zero point and the frequency f 2 of the pole in accordance with the vehicle speed.

5. The control device according to claim 3 , wherein the processor is programmed to change values of the frequency f 1 of the zero point and the frequency f 2 of the pole in accordance with the vehicle speed using a table that defines a relationship among the vehicle speed, the frequency f 1 of the zero point, and the frequency f 2 of the pole.

6. The control device according to claim 1 , wherein the processor is programmed to perform control to change the gain and the phase in accordance with the steering frequency when the steering frequency is about 0.1 to about 5.0 Hz.

7. The control device according to claim 1 , wherein the processor is programmed to perform stabilization compensation on the determined assist torque to generate a stabilization compensation torque.

8. An electric power steering apparatus comprising:
a motor;
a steering torque sensor; and
the control device according to claim 1 .

9. A control method, usable in an electric power steering apparatus including a motor to control driving of the motor, the control method comprising:
acquiring a steering torque detected by a steering torque sensor and a vehicle speed detected by a vehicle speed sensor;
changing a gain and a phase to be applied to the steering torque in accordance with a steering frequency when a driver steers a steering wheel;
determining a magnitude of an assist torque based on the steering torque to which the gain and the phase have been applied and the vehicle speed; and
generating a torque command value to be used to control driving of the motor based on the determined assist torque; wherein
a vehicle on which the electric power steering apparatus is mounted allows settings of different types of travel modes; and
the control method performs control to vary each degree of change in the gain and the phase in accordance with the steering frequency depending on one of the types of the travel modes selected by the driver.

Assignees

• Nidec Corp

Inventors

• Endo Shuji
• Ishimura Hiroyuki

Classifications

• B62D5/0424

  the axes of motor and final driven element of steering gear, e.g. rack, being parallel · CPC title

• B62D5/0409

  Electric motor acting on the steering column · CPC title

• B62D6/10

  characterised by means for sensing {or determining} torque · CPC title

• B62D6/007 Primary

  adjustable by the driver, e.g. sport mode · CPC title

• B62D5/0463 Primary

  calculating assisting torque from the motor based on driver input · CPC title