Stabilization of unstable periodic orbits in DC drives

Drive using dc shunt motor or permanent magnet dc (PMDC) motor as prime mover, exhibits bifurcation and chaos. The characteristics of dc shunt and PMDC motors are linear in nature. These motors are controlled by pulse width modulation (PWM) technique with the help of semiconductor switches. These switches are nonlinear elements that introduce nonlinear characteristics in the drive. Any nonlinear system can exhibits bifurcation and chaos. DC shunt or PMDC drives show normal period-1 behavior for certain range of parameter values. It is also observed that these drives show chaos for significantly large ranges of parameter values. Control of chaos helps to use the whole domain of parameters space of the drive so that the drive shows normal period-1 behavior for whole range of parameter space. In this paper we present a method for controlling chaos applicable to dc shunt and PMDC drives.