# US 2014/0195122 A1 · Electric power steering device

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- Number: US 2014/0195122 A1
- Document ID: US20140195122A1
- Status: Published application
- Kind: A1
- Application number: 14/236,239
- Filed: 2012-05-22
- Published: 2014-07-10
- Earliest claimed: 2011-08-04
- Assignees: Honda Motor Co., Ltd.
- Inventors: Yoshihiro Oniwa; Yasuo Shimizu; Atsuhiko Yoneda
- Web page: https://patentgrep.com/patent/US20140195122A1

## CPC

- B62D 5/0463: {calculating assisting torque from the motor based on driver input}
- G05D 17/02: characterised by the use of electric means
- B62D: MOTOR VEHICLES; TRAILERS (steering, or guiding on a desired track, of agricultural machines or implements A01B69/00; wheels, castors, axles, increasing wheel adhesion B60B; vehicle tyres, tyre inflation or tyre changing B60C; connections between vehicles of a train or the like B60D; vehicles for use on rail and road, amphibious or convertible vehicles B60F; suspension arrangements B60G; heating, cooling, ventilating or other air treating devices B60H; windows, windscreens, non-fixed roofs, doors or similar devices, protective coverings for vehicles not in use B60J; propulsion plant arrangements, auxiliary drives, transmissions, controls, instrumentation or dashboards B60K; electric equipment or propulsion of electrically-propelled vehicles B60L; power supply for electrically-propelled vehicles B60M; passenger accommodation not otherwise provided for B60N; adaptations for load transportation or to carry special loads or objects B60P; arrangement of signalling or lighting devices, the mounting or supporting thereof or circuits therefor, for vehicles in general B60Q; vehicles, vehicle fittings or vehicle parts not otherwise provided for B60R; servicing, cleaning, repairing, supporting, lifting, or manoeuvring, not otherwise provided for, B60S; brake arrangements, brake control systems or parts thereof B60T; air-cushion vehicles B60V; motor-cycles, accessories therefor B62J, B62K; testing of vehicles G01M)
- G05D: SYSTEMS FOR CONTROLLING OR REGULATING NON-ELECTRIC VARIABLES

## Abstract

Provided is an electric power steering device in which the operation feeling is improved without a decrease in commercial value. A phase compensation unit performs a frequency shift on a compensation frequency band compensated by the phase compensation unit. The phase compensation unit performs phase-shift in the compensation frequency band through a frequency shift process, instead of an increase in compensation gain. Therefore, it is possible to minimize occurrences of minute vibrations and abnormal noise in the steering system including the motor that accompany an increase in gain, and to improve the operation feeling and commercial value.

## Claims

### Claim 1

An electric power steering apparatus for controlling an electric motor depending on a steering torque applied to an operating member, and transmitting a drive force generated by the electric motor to a steering mechanism to assist in steering a vehicle, comprising:
a steering torque sensor for detecting the steering torque;
a phase compensator for phase-compensating a torque signal output by the steering torque sensor; and
an assistive current determiner for determining an assistive current that flows through the electric motor based on at least the torque signal, which is phase-compensated by the phase compensator,
wherein the phase compensator performs a frequency shifting process for frequency-shifting both a pole of a minimum frequency and a zero point of a minimum frequency toward higher frequencies, or for frequency-shifting both a pole of a minimum frequency and a zero point of a minimum frequency toward lower frequencies, for thereby changing a compensation frequency band that is compensated by the phase compensator.

### Claim 2 (depends on 1)

The electric power steering apparatus according to claim 1, further comprising:
a vehicle speed detector for detecting a vehicle speed,
wherein the phase compensator changes, toward higher frequencies, the compensation frequency band that is compensated by the phase compensator according to the frequency shifting process, as the vehicle speed detected by the vehicle speed detector becomes higher.

### Claim 3 (depends on 1)

The electric power steering apparatus according to claim 1, wherein the phase compensator changes, toward lower frequencies, the compensation frequency band that is compensated by the phase compensator according to the frequency shifting process, as the torque signal detected by the steering torque sensor becomes greater.

### Claim 4 (depends on 1)

The electric power steering apparatus according to claim 1, wherein the phase compensator changes, toward lower frequencies, the compensation frequency band that is compensated by the phase compensator according to the frequency shifting process, as the assistive current determined by the assistive current determiner becomes greater.

### Claim 5 (depends on 1)

The electric power steering apparatus according to claim 1, wherein the phase compensator calculates an assistive gain as a ratio of the assistive current determined by the assistive current determiner to the torque signal detected by the steering torque sensor, and changes, toward lower frequencies, the compensation frequency band that is compensated by the phase compensator according to the frequency shifting process, as the calculated assistive gain becomes greater.