Patent ID: 6262544
Filing Date: 2001-07-17
Classification: H02P

Abstract:
A method of recreating actual motor current from sensed bus current information in a four quadrant motor, comprising the steps of:(a) monitoring a motor voltage magnitude request signal which varies between zero and a maximum value;(b) monitoring a motor direction request input;(c) based upon the request signal and input monitored in steps (a) and (b), establishing a voltage request reference signal which varies in magnitude between zero and a maximum reference value, the voltage request reference signal having an offset zero point such that a signal magnitude above said offset zero point represents a positive motor voltage request and a signal magnitude below said offset zero point represents a negative motor voltage request;(d) monitoring a current magnitude request signal which varies between zero and a maximum current request value;(e) establishing a first current request reference signal and a second current request reference signal based upon the signal monitored in step (d), where each of the first and second current request reference signals have a similar offset zero point and the first and second current request reference signals diverge in opposite directions from the offset zero point as the current magnitude request signal diverges from zero;(f) monitoring a voltage across a current sense resistor of a bus connected for powering the motor;(g) offsetting of the voltage monitored in step (f) to establish a sense resistor reference signal having an offset sense resistor zero point, where a signal magnitude above the offset sense resistor zero point represents a positive signal across the sense resistor and a signal magnitude below the offset sense resistor zero point represents a negative signal across the sense resistor;(h) comparing the first current request reference signal with a feedback current signal;(i) comparing the second current request reference signal with the feedback current signal;(j) providing the sense resistor reference signal to a controllable amplifier;(k) controlling a positive/negative gain of the controllable amplifier based upon the voltage request reference signal, the first current request reference signal, the second current request reference signal, and the current feedback signal; and(l) sampling a signal output of the controllable amplifier to generate the current feedback signal which represents the actual current of the four quadrant motor.