Microstepping with PI feedback and feedforward for permanent magnet stepper motors

In this paper, the stability of microstepping is investigated via Lyapunov method. Microstepping with proportional integral (PI) feedback and feedforward is proposed for the position tracking of a Permanent Magnet (PM) stepper motor. Given static inputs to the two phase PM stepper motor, it is proven that the stability of equilibrium points is guaranteed by LaSalle´s theorem. For position tracking, the relationships between the voltage input and current output of each phase for the position tracking are derived. From the relationships, microstepping with PI feedback and feedforward is developed for the position tracking. Experimental result shows that the position tracking performance of the proposed controller is improved compared to conventional microstepping.