Improvements relating to electrical power assisted steering systems
AssigneeTRW Inc.
InventorsDavid Julian Moule, Andrew James Stephen Williams, Jeffrey Ronald Coles
Life of this patent
Estimating the term…
Abstract
An electric power assisted steering system comprises a motor adapted to apply an assistance torque to a portion of a steering shaft in response to a motor drive signal from a drive circuit, in which the motor comprises a synchronous wound field motor of the kind comprising a stator and a rotor, in which the rotor includes at least one pole and at least one coil winding associated with the pole and the stator comprises a number of phase windings, and in which the drive circuit which is configured to provide current in the coils of the stator and rotor during operation of the motor.
Claims16
An electric power assisted steering system comprising a motor adapted to apply an assistance torque to a portion of a steering shaft in response to a motor drive signal from a drive circuit, in which the motor comprises a synchronous wound field motor of the kind comprising a stator and a rotor and wherein the synchronous wound field motor does not contain any permanent magnets, in which the rotor includes at least one pole and at least one coil winding associated with the at least one pole and the stator comprises a number of phase windings, and in which the drive circuit which is configured to provide current in coils of the stator and rotor during operation of the motor.
A method of determining an angular position of a rotor of a motor adapted to apply an assistance torque to a portion of a steering shaft in response to a motor drive signal from a drive circuit, in which the motor comprises a synchronous wound field motor of the kind comprising a stator and a rotor and wherein the synchronous wound field motor does not contain any permanent magnets, in which the rotor includes at least one pole and at least one coil winding associated with the at least one pole and the stator comprises a number of phase windings, and in which the drive circuit which is configured to provide current in coils of the stator and rotor during operation of the motor, the method comprising:
- applying a change in voltage to the rotor winding and measuring a current flowing in the rotor winding;
- determining a rate of change of current in response to the application of the change in voltage and from the rate of change estimating an inductance of the rotor;
- and
- estimating a rotor position by correlating the estimated inductance with stored information indicative of a variation of inductance with position.
Dependencies are inferred from the claim text.