Patent ES-8601036-A1 (ES)
Title: A method of operating electric power steering.
IPC: B62D6/10
Filed: 1984-10-11
Abstract: A torque transducer senses the operator exerted steering torque and provides an output signal which varies in magnitude from a low 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. The controller develops a zero torque reference which has an initial value corresp. to the mean value of the torque transducer output signal, and steering torque assist is developed in relation to the difference between the zero torque reference and the transducer output signal. - In operation, the zero torque reference is shifted according to a predetermined time response characteristic in a direction to reduce the difference between it and the transducer output signal. Over a period of time, the shifting of the zero torque difference due to operator exerted steering torque tends to cancel out and the remaining shifting adaptively compensates the zero torque reference for drift and other like sources of error affecting the magnitude of the transducer output signal. EPAB- EP-138467 B A method of operating a motor vehicle electric power steering system including a torque transducer (40) 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 (32) energizable to produce a steering assist torque, and a motor controller (36) for variably energizing such motor to produce steering assist torque in direct relation to a control signal applied thereto, characterised in that the method of operation comprises 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 transucder output signal thereby to cause the value of the zero torque reference to more nearly correspons to the actual value of the transducer output signal for which no steering torque is exerted by the operator of the vehicle. (16pp) - EP-138467 B A method of operating a motor vehicle electric power steering system including a torque transducer (40) 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 (32) energizable to produce a steering assist torque, and a motor controller (36) for variably energizing such motor to produce steering assist torque in direct relation to a control signal applied thereto, characterised in that the method of operation comprises 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 transucder output signal thereby to cause the value of the zero torque reference to more nearly correspons to the actual value of the transducer output signal for which no steering torque is exerted by the operator of the vehicle. (16pp)