A detailed analysis of the nonlinear dynamics of the electric step motor

The electric step motor is an electromechanical device which converts electrical pulses into discrete mechanical movements. The shaft of the motor rotates in discrete increments when command pulses are applied in the proper sequence. The dynamic behavior of this motor is of great importance, since instabilities lead to velocity fluctuations that are unacceptable in many applications. It is a major limitation to the development of high performance open-loop step motor system. The dynamics of a hybrid step motor is studied by using the tools of chaos theory and time series analysis. Lyapunov exponents, fractal dimension and other empirical quantities are determined from experimental data. Particular attention is paid to issues of stationarity in the system. We show that the electric step motor may function as a low-dimensional chaotic system. As such, chaotic control techniques may be applied that allow this motor to operate effectively within the chaotic regime.