Analysis and control of the permanent-magnet stepper motor

A stepper motor has the ability to translate digital signals into angular shaft positions. This paper deals with the dynamic characteristics of a 90° permanent magnet motor, when used to switch a load through a sequence of angular steps. The non-linear system equations are derived, and linearized versions of these equations are used to estimate the dynamic response for single-step operation. Multi-step performance is computed directly from the non-linear equations. The effect on performance of a constant current or constant voltage supply is considered, and it is shown that the transient response can be modified with a negative impedance converter.