ABSTRACT
AC motors include mainly permanent magnet synchronous motors (PMSM) and induction motors (IM). Due to the rapid improvement in power electronics and microprocessors, the performances of AC servo systems have reached and even exceeded that of traditional DC servo systems. This chapter examines the control of AC motors, including PMSMs and IMs. The design of the velocity controller is more challenging, mainly since mechanical resonances, backlash, and friction influence the performance and the stability of the velocity loop. The filter in the velocity loop is used to suppress mechanical resonance in the servo systems. The task of the control system design for a PMSM is to design the three controllers: the position controller, the velocity controller, and the current controller, with a filter in the velocity loop. The vector-control method and PI controllers are widely used in the PMSM speed-control system. In order to achieve high-performance in PMSMs, a vector-control strategy and a rotor position sensor are typically required.
