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Adaptive controller for electric power steering

  • US 4,509,611 A
  • Filed: 10/13/1983
  • Issued: 04/09/1985
  • Est. Priority Date: 10/13/1983
  • Status: Expired due to Term
First Claim
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1. In a motor vehicle electric power steering system including a torque transducer responsive to steering torque exerted by the operator of the vehicle for generating an electrical output signal variable in magnitude from a lower limit value representative of a large operator exerted steering torque in one direction through a mean value representative of no operator exerted steering torque to an upper limit value representative of a large operator exerted steering torque in the opposite direction, an electric motor energizable to produce a steering assist torque, and a motor controller for variably energizing such motor to produce steering assist torque in direct relation to a control signal applied thereto, a method of operation, comprising the steps of:

  • generating a zero torque reference having an initial value which corresponds to the mean value of the torque transducer output signal;

    developing a control signal for said motor controller according to the magnitude of the difference between the zero torque reference and the transducer output signal, such difference being attributable to operator exerted steering torque, to sources of error which affect the magnitude of the transducer output signal, or to both; and

    shifting the zero torque reference in a direction to reduce the difference between it and the transducer output signal in accordance with a predetermined time response characteristic so that over a period of time shifting of the zero torque reference due to operator exerted steering torque tends to cancel out and the remaining net shift tends to adaptively compensate the zero torque reference for sources of error which affect the magnitude of the transducer output signal thereby to cause the value of the zero torque reference to more nearly correspond to the actual value of the transducer output signal for which no steering torque is exerted by the operator of the vehicle.

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