A step motor phase locking control system and it's velocity errordamping method is presented in this paper. A convenient method for engineering design is also given.
By introducing nonlinear damping term, it is proved that all signals in the closed-loop system are globally stable, and the tracking error and the parameter (estimation) error converge to zero.
The concept of roll energy decay function is put forward, and the nonlinear damping coefficients are solved based on the minor error between actual energy function and evaluated energy function.