Control device, electric power steering device, and control method

Patent metadata

Field	Value
Publication number	US-12195107-B2
Application number	US-202218086285-A
Country	US
Kind code	B2
Filing date	Dec 21, 2022
Priority date	Dec 28, 2021
Publication date	Jan 14, 2025
Grant date	Jan 14, 2025

Abstract

A control device that controls a control target including at least a motor in a steering mechanism including an input shaft to which a steering wheel is connected, an output shaft connected to the input shaft via a torsion bar, and the motor connected to the output shaft. The control device includes a reaction force controller to generate an input torque input to the control target based on a torsion bar torque generated in the torsion bar and to control a reaction force transmitted from the steering wheel to the steering person, and an assist controller to generate a correction torque to correct the input torque based on an output of the control target and a nominal model. The assist controller is configured or programmed such that a transfer function of the control target is constrained by a transfer function of the nominal model in a frequency band.

First claim

What is claimed is:

1. A control device that controls a control target including at least a motor in a steering mechanism including an input shaft to which a steering wheel steered by a steering person is connected, an output shaft connected to the input shaft via a torsion bar, and the motor connected to the output shaft, the control device comprising:
a reaction force controller to generate an input torque input to the control target based on a torsion bar torque generated in the torsion bar and to control a reaction force transmitted from the steering wheel to the steering person; and
an assist controller to generate a correction torque to correct the input torque based on an output of the control target and a nominal model; wherein
the assist controller is configured or programmed such that a transfer function of the control target is constrained by a transfer function of the nominal model in a frequency band where a gain in a gain characteristic of a complementary sensitivity function with respect to a modeling error between the control target and the nominal model is approximately 1; and
the nominal model is a model in which mechanical characteristics when the steering person steers the steering wheel are considered.

2. The control device according to claim 1 , wherein an order of the transfer function of the nominal model is 3 or more.

3. The control device according to claim 1 , wherein the nominal model is a model having a frequency characteristic between a one-inertia system and a two-inertia system.

4. The control device according to claim 1 , wherein
the assist controller includes:
a high-pass filter having a first cutoff frequency; and
a low-pass filter having a second cutoff frequency higher than the first cutoff frequency; and

when a transfer function of the low-pass filter is Q(s) and a transfer function of the high-pass filter is HPF(s), the complementary sensitivity function is Q(s)·HPF(s).

5. The control device according to claim 1 , wherein an expression representing the transfer function of the nominal model is an expression obtained by adding an attenuation term to an expression representing a two-inertia system.

6. The control device according to claim 5 , wherein a transfer function P n (s) of the nominal model is expressed by a following Expression:

P
n

(
s
)

=

1

J

STG
n

⁢
s

+

B

STG
n

⁢

s
2

+

2
⁢

ζ

1
⁢
n

⁢

ω

1
⁢
n

⁢
s

+

ω

1
⁢
n

2

s
2

+

2
⁢

ζ

2
⁢
n

⁢

ω

2
⁢
n

⁢
s

+

ω

2
⁢
n

2

where s is a Laplace transformer, J STGn is a parameter representing inertia moment of the nominal model, B STGn is a parameter representing a viscous friction coefficient of the nominal model, ω 1n is a frequency at a zero point of the transfer function P n (s), ω 2n is a frequency of a pole of the transfer function P n (s), ζ 1n is a damping ratio at a zero point of the transfer function P n (s), and ζ 2n is a damping ratio at a pole of the transfer function P n (s).

7. The control device according to claim 1 , further comprising a state feedback circuit to feed back a state compensation value to the input torque based on the output of the control target so that an apparent transfer function of the control target approaches a transfer function of the nominal model.

8. The control device according to claim 7 , wherein the state feedback circuit is operable to feed back the state compensation value to the input torque after the state compensation value is corrected by the correction torque and before the state compensation value is input to the control target.

9. The control device according to claim 7 , wherein the state compensation value includes a compensation value that compensates at least a portion of an inertial force generated in the control target, a viscous force generated in the control target, and a frictional force generated in the control target.

10. The control device according to claim 7 , wherein the assist controller is configured or programmed to generate the correction torque based on a difference between a torque calculated using the nominal model based on an output of the control target and the input torque before the state compensation value is fed back after being corrected by the correction torque.

11. The control device according to claim 1 , wherein the assist controller is configured or programmed to generate the correction torque based on a rotation angle of the input shaft.

12. The control device according to claim 1 , wherein
the assist controller includes a disturbance compensation value calculator to calculate a disturbance compensation value to compensate at least a portion of a self-aligning torque generated in the control target; and
the correction torque includes the disturbance compensation value.

13. The control device according to claim 12 , wherein the disturbance compensation value includes a compensat

Assignees

• Nidec Corp

Inventors

• Endo Shuji
• Miyake Sohei
• Ishikawa Masaya
• Notsu Daisuke

Classifications

• B62D5/0421

  Electric motor acting on or near steering gear · CPC title

• H02P23/0022

  Model reference adaptation, e.g. MRAS or MRAC, useful for control or parameter estimation · CPC title

• H02P6/34

  Modelling or simulation for control purposes · CPC title

• H02P6/04

  Arrangements for controlling or regulating the speed or torque of more than one motor (H02P6/10 takes precedence) · CPC title

• B62D5/0463 Primary

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