Averaged model of inverter-fed ultrasonic motors

An averaged model for the most advanced traveling wave type ultrasonic motor drive is presented using a generalized averaging method. The modeling approach reflects the interesting dynamic behavior of the drive's ultrasonic vibrations by time-varying fundamental Fourier coefficients and coincides with the realized measurement system. Hence, the novel model is predestined for optimized control schemes of the drive using two-phase vector-modulation concepts for the feeding resonant converter. Since the describing function method is applied for the nonlinear blocks of inverter and stator/rotor-contact, first the switching behavior is eliminated reducing the simulation time compared with the original drive model and second an appropriate contact model is derived combining the partial models of stator and rotor.