Control system for transducer positioning motor
 A control system for a stepper motor utilized in positioning a transducer in relationship to a plurality of parallel tracks on a record media. Dual closed loop feedback systems are provided. A current control circuit is provided having a high output impedance and a voltage control circuit is provided having a low output impedance. A switch may select the control sensor when the transducer is making coarse adjustments in position and may select the voltage control sensor when the transducer is making fine adjustments in position. A seamless switchover may be achieved where the voltage control sensor has a time constant which matches the time constant of the stepper motor. Performance is further improved by providing an impedance cancellation circuit which eliminates the internal resistance of the motor in order to quickly damp motionally induced emf of the motor. 
Minnesota Mining and Manufacturing Company
G
G11B
inventional
Martyn A.
Lewis