Patent ID: 8058824

Claim:
A control system for an electric motor comprising: a control unit adapted to be connected to an electric motor and arranged to determine the position of the motor from at least one electrical parameter by means of a position determining algorithm which is included in the control unit, the algorithm being reliant on movement of the motor to determine a motor position, and to start up the motor from rest by applying voltages to the motor that are independent of the position of the motor, the position determining algorithm defining a model of the motor which includes a motor position state and which is arranged to estimate the motor position from at least one model input; the position determining algorithm including a corrector arranged to monitor an output of the model and compare it to a measured parameter thereby to determine a correction factor that can be input to the model, the correction factor being arranged to correct the motor position state of the model with the control unit being arranged to limit the sign of the correction factor at low motor speeds thereby to control the direction in which the motor will turn.