High performance control of /spl pi//4-multiple-pitched linear hybrid stepping motor with ripple force compensator

A linear hybrid stepping motors (LHSMs) have been widely used owing to its simple structure and ripple-free holding force at aligned position. Despite its attractive features, the LHSM delivers the significant thrust vibrations during position-to-position movement, that are the dominant cause of the positioning error, mechanical stress, and acoustic noise. In order to overcome this defect, we propose an active control scheme to damp the vibration for /spl pi//4-multiple-pitched LHSM by the feed-forward compensation signal. Utilizing a reluctance network and FEM analysis that incorporate the factors of non-uniform air gap, manufacturing tolerance, and nonlinear material properties, the LHSM with force ripple components is modeled as a nonlinear position-dependent function. The damping force signal is estimated from the Jacobian linearization observer and the positioning accuracy is significantly improved through a closed-loop control scheme for restraining the thrust ripple.