Active damping control of linear hybrid stepping motor for cogging force compensation

Linear hybrid stepping motors (LHSMs) have a simple structure and provide ripple-free holding force at the aligned position. Despite these attractive features, however, an LHSM delivers strong 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 have developed an active control scheme to damp the vibration of a pi/4-multiple-pitched LHSM by a feed-forward compensation signal. Utilizing an elaborate reluctance network based on the finite-element analysis to take the nonlinear magnetic properties into account, we model the LHSM with force ripple components as a nonlinear position-dependent function. We estimate the damping force signal from the Jacobian linearization observer. The positioning accuracy is significantly improved through a closed-loop control scheme for restraining the thrust ripple.