Control device and control method for use in electric power steering device, and motor module

Patent metadata

Field	Value
Publication number	US-11807315-B2
Application number	US-202117192887-A
Country	US
Kind code	B2
Filing date	Mar 5, 2021
Priority date	Mar 9, 2020
Publication date	Nov 7, 2023
Grant date	Nov 7, 2023

Abstract

Both responsiveness and stability of a power assist control system are satisfied. A processor executes, in accordance with a program, determining base assist gain based on steering torque and base assist torque, generating stabilizing compensation torque based on the base assist torque, with use of a stabilizing compensator that has a second-order or higher transfer function in which a frequency characteristic is variable in accordance with the base assist gain and which is expressed using a responsiveness parameter ω and a damping parameter ζ, and generating a current command value for use in control of the motor based on the stabilizing compensation torque.

First claim

What is claimed is:

1. A control device for use in an electric power steering device including a motor and for controlling the motor, the control device comprising:
a processor; and
a memory that stores a program that controls operation of the processor, wherein
the processor executes, in accordance with the program,
determining base assist gain based on steering torque and base assist torque,
generating stabilizing compensation torque based on the base assist torque, with use of a stabilizing compensator that has a second-order or higher transfer function in which a frequency characteristic is variable in accordance with the base assist gain and which is expressed using a responsiveness parameter w and a damping parameter ζ, and
generating a current command value for use in control of the motor based on the stabilizing compensation torque, and

the transfer function is expressed as Formula 1,

C

S
⁢
C
⁢
2

(
s
)

=

s
2

+

2
⁢

ζ
1

⁢

ω
1

⁢
s

+

ω
1
2

s
2

+

2
⁢

ζ
2

(

ω
2

⁢
s

+

ω
2
2

⁢

(

ω
2
2

ω
1
2

)

where s is a Laplace transformer, ω 1 is a zero point frequency, ω 2 is a pole frequency, ζ 1 is zero point damping, and ζ 2 is pole damping.

2. The control device according to claim 1 , wherein the zero point damping ζ 1 and the pole damping ζ 2 in the Formula 1 are respectively variable in accordance with the base assist gain.

3. The control device according to claim 1 , wherein the stabilizing compensator decreases the zero point damping ζ 1 as the base assist gain increases.

4. The control device according to claim 1 , wherein the stabilizing compensator increases the pole damping ζ 2 as the base assist gain increases and decreases the pole damping ζ 2 as the base assist gain decreases.

5. The control device according to claim 1 , wherein the processor determines the base assist torque based on the steering torque and a vehicle speed with reference to a table, and determines the base assist gain based on a slope defined by a ratio of a change amount in the base assist torque to a fluctuation amount in the steering torque.

6. The control device according to claim 5 , wherein, in a case in which the steering torque is equal to or higher than a threshold value, the processor employs, as the base assist gain, a value for a base assist gain corresponding to the threshold value for the steering torque.

7. A motor module comprising:
a motor; and
a control device for use in an electric power steering device including the motor and for controlling the motor, the control device comprising:
a processor, and
a memory that stores a program that controls operation of the processor, wherein the processor executes, in accordance with the program,
determining base assist gain based on steering torque and base assist torque,
generating stabilizing compensation torque based on the base assist torque, with use of a stabilizing compensator that has a second-order or higher transfer function in which a frequency characteristic is variable in accordance with the base assist gain and which is expressed using a responsiveness parameter w and a damping parameter ζ, and
generating a current command value for use in control of the motor based on the stabilizing compensation torque, and

the transfer function is expressed as Formula 1,

C

S
⁢
C
⁢
2

(
s
)

=

s
2

+

2
⁢

ζ
1

⁢

ω
1

⁢
s

+

ω
1
2

s
2

+

2
⁢

ζ
2

⁢

ω
2

⁢
s

+

ω
2
2

⁢

(

ω
2
2

ω
1
2

)

Assignees

• Nidec Corp
• Nidec Elesys Corp

Inventors

• Endo Shuji
• Ishimura Hiroyuki

Classifications

• B62D5/0472 Primary

  for damping vibrations · CPC title

• B62D5/0463

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

• B62D5/0481

  monitoring the steering system, e.g. failures · CPC title

• B62D5/0421 Primary

  Electric motor acting on or near steering gear · CPC title