Suppression of Rotor Oscillation in Microstepping of a Stepping Motor by Pre-Compensator

Abstract

In the drive of an open-loop-controlled stepping motor, it is well known that the natural oscillation of the motor causes harmful phenomena like the low-frequency resonance, the increase of the settling time and the acoustic noise. Microstepping is known as a method for suppression of rotor oscillation; it is effective especially in the constant-speed drive. However, the rotor oscillation occurs in the transient region even in the case of microstepping, provided that the dynamic property of the system is not taken into account.In the present work, the authors suggest to use a pre-compensator to suppress the natural oscillation of the microstepped stepping motor. In the design of the compensator, guarantee of robustness to the variation of the inertial load which causes the variation of oscillatory characteristic is regarded as the main point. In addition, prevention of phase lag to the reference signal which has a harmful influence on the case of path following control is also taken into consideration. The adoption of a preview type FIR low-pass filter is shown to be suitable for the above purpose through the analysis of the system in the frequency domain. The effectiveness of this method is evaluated by the experiment, and it is confirmed that the rotor oscillation is suppressed excellently.