Piecewise modeling and optimal commutation of switched reluctance motors

A piecewise modeling approach to characterize the nonlinearities of switched reluctance machines is presented. In particular, the phase torque function, which is a highly nonlinear function of phase current and rotor position, is shown to be modeled by simple, yet accurate, piecewise analytic expressions. Consequently, implementation of instantaneous torque control by on-line computation, rather than by look-up tables is a feasible option using the piecewise model. Another feature of the piecewise modeling approach is that it simplifies the formulation and solution of various optimization problems. Two optimal commutation methods are presented for instantaneous torque control: the first minimizes copper losses, whereas the second minimizes the rates-of-change of phase currents