Closed loop torque angle control of synchronous motor

Claim 1

In a closed loop motor system having a motor with a plurality of poles and motor windings associated therewith, said poles defining full step motor output positions, said system of the type that assigns intermediated current values to the motor windings for fine step positions of the motor output between motor poles, the improvement comprising a motor output position encoder for generating an integral and fixed number of encoder pulses as the motor moves between any two motor poles, said pulses being equally spaced and at least some corresponding to the fine step positions, means for assigning intermediate current values comprising a counter for counting the encoder pulses, function means for converting the count to digital sine and cosine values, digital-to-analog means for converting the digital sine and cosine values to analog sine and cosine values, means for controlling electrical current to the motor windings associated with the poles in response to the analog sine and cosine values, means for setting the torque angle comprising means for adding or subtracting a torque angle value from the count applied to the function means, and initializing means comprising means for applying full step current values to motor windings for a time interval in which the motor output is assumed to align with a full step position, and means for zeroing the count in the counter and assigning the torque angle value, whereby the encoder does not require mechanical alignment relative to the motor.