Dual control of closed-loop stepping motor precision servo

Stepping motors when commuted by feedback of rotor position have controllable ripple characteristics via varying both magnitude and lead angle of the driving voltage waveform. This paper describes how the two control parameters, magnitude and lead angle, may be used together in a dual control strategy to help minimize torque ripple at high speed as well as at low speed for improved position tracking accuracy. Experimental results of motor characteristics under dual control are presented. Characteristic of this dual control strategy is further demonstrated by its application in a positioning servo on an X-Y table. The positioning and profile tracking results have shown its capability for many high precision motion control applications beyond the resolution of stepping motors.