# US 2014/0207335 A1 · Electric power steering system

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- Number: US 2014/0207335 A1
- Document ID: US20140207335A1
- Status: Published application
- Kind: A1
- Application number: 14/152,444
- Filed: 2014-01-10
- Published: 2014-07-24
- Earliest claimed: 2013-01-18
- Assignees: Jtekt Corporation
- Applicants: Jtekt Corporation
- Inventors: Satoru MIKAMO; Kenichiro AOKI
- Web page: https://patentgrep.com/patent/US20140207335A1

## CPC

- B62D 5/0463: {calculating assisting torque from the motor based on driver input}
- B62D 5/046: {Controlling the motor}
- B62D 5/0481: {monitoring the steering system, e.g. failures}
- 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)

## Abstract

There is provided a drive control method for a motor including multiple sets of coils and drive circuits in an electric power steering system. In order to reduce computational load when sensorless control is executed, an electrical angle estimator includes an α-axis voltage component adder and a β-axis voltage component adder that add together voltage vectors of a first coil and a second coil expressed in a two-phase fixed coordinate system, an α-axis current component adder and a β-axis current component adder that add together current vectors of the first coil and the second coil expressed in a two-phase fixed coordinate system, and an induced voltage computing unit that computes an induced voltage based on an added voltage vector and an added current vector.

## Claims

### Claim 1

An electric power steering system comprising:
a permanent magnet synchronous motor disposed in a steering mechanism to generate steering assist torque, and including a motor stator provided with multiple sets of three-phase coils with different drive systems;
a motor drive unit that includes drive circuits provided so as to respectively correspond to the multiple sets of three-phase coils, and that energizes the multiple sets of three-phase coils independently through the respective drive circuits to drive the permanent magnet synchronous motor;
an electrical angle estimator that computes an estimated electrical angle of the permanent magnet synchronous motor; and
a motor control unit that controls the drive circuits of the motor drive unit based on the estimated electrical angle computed by the electrical angle estimator to drive the permanent magnet synchronous motor,
wherein the electrical angle estimator includes
multiple three phase-two phase voltage vector converters each of which converts a voltage vector of voltages supplied to the three-phase coils, the voltage vector being expressed in a three-phase fixed coordinate system, into a voltage vector expressed in a two-phase fixed coordinate system, and which are provided respectively for the multiple sets of three-phase coils,
multiple three phase-two phase current vector converters each of which converts a current vector of currents passed through the three-phase coils, the current vector being expressed in a three-phase fixed coordinate system, into a current vector expressed in a two-phase fixed coordinate system, and which are provided respectively for the multiple sets of three-phase coils,
multiple voltage vector adders each of which adds together the voltage vectors of the multiple sets of three-phase coils, the voltage vectors being expressed in the two-phase fixed coordinate system,
multiple current vector adders each of which adds together the current vectors of the multiple sets of three phase coils, the voltage vectors being expressed in the two-phase fixed coordinate system, and
an induced voltage computing unit that computes an induced voltage generated at the permanent magnet synchronous motor based on an added voltage vector computed by the voltage vector adders and an added current vector computed by the current vector adders,
wherein the electrical angle estimator estimates an electrical angle of the permanent magnet synchronous motor based on the computed induced voltage.

### Claim 2 (depends on 1)

An electric power steering system according to claim 1, wherein, the motor includes a motor stator provided with two sets of three-phase coils with different drive systems.

### Claim 3 (depends on 1)

An electric power steering system according to claim 1, further comprising:
a estimated electrical angle computing unit that computes an estimated electrical angle of the motor by computing an arc tangent of the induced voltage vector.

### Claim 4 (depends on 1)

An electric power steering system according to claim 1, further comprising:
a rotation direction estimator that estimates the direction in which the motor rotates.

### Claim 5 (depends on 4)

An electric power steering system according to claim 4, wherein, the rotation direction estimator estimates the direction of the motor rotation from the direction of a steering torque detected by a torque sensor.

### Claim 6 (depends on 4)

An electric power steering system according to claim 4, further comprising:
a yaw rate sensor that detects a yaw rate of a vehicle body, wherein, the rotation direction estimator estimates the direction of the motor rotation from the direction of the yaw rate detected by the yaw rate sensor.

### Claim 7 (depends on 4)

An electric power steering system according to claim 4, further comprising:
a lateral acceleration sensor that detects a lateral acceleration of a vehicle body, wherein, the rotation direction estimator estimates the direction of the motor rotation from the direction of the lateral acceleration detected by the lateral acceleration sensor.