Nonlinear control of permanent magnet stepper motors

Abstract

The nonlinear dynamics of a permanent magnet stepper motor is studied by means of modern nonlinear theories such as bifurcation and chaos. A three-phase stepper motor is considered as a case study in this paper. The study shows that the system experiences a dynamic bifurcation (Hopf bifurcation) at high frequencies. Since this kind of motors is widely used in some important applications such as printers, disk drives, process control systems, X– Y records, and robotics, controlling such instabilities is the main concern of this paper. A nonlinear robust model-reference controller is introduced. The study shows how to stabilize the system, while having a satisfactory performance, even in the case when some of the motor parameters were uncertain.