This chapter discusses the dynamic characteristics of ultrasonic motors (USMs) with special attention to a bar-type USM that is one of the traveling wave type USMs. The USMs are known to possess nonlinearities caused by the frictional interface between the stator and the rotor, as well as the amplitudedependent nonlinearity in the dynamics of the stator. Therefore, the transient dynamics of a bar-type ultrasonic motor, such as starting-up and stopping, can be quite complicated due to such nonlinearities. The transient response of the bartype ultrasonic motor at starting-up and stopping is discussed in detail by using experimental results measured by a Laser Doppler Velocimeter (LDV), and results of numerical simulations with a second-order nonlinear oscillator model.
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