Load characteristics of ultrasonic motors with a longitudinal-torsional converter and various nonlinear springs for inducing static pressure

The vibration and load characteristics of ultrasonic motors that use a longitudinal-torsional vibration converter and various nonlinear springs were studied. Ultrasonic motors have one-dimensional longitudinal-torsional converters with a diagonally slitted part. The vibration characteristics were markedly improved using nonlinear springs for inducing static pressure on the driving surface. Using a nonlinear static pressure source, the frictional driving force of a rotor increases during the forward duty cycle, and that during the opposite retracting cycle decreases, resulting in small frictional loss. The nonlinear static and dynamic characteristics of various material springs were measured. The nonlinear static pressure source may be applied to any types of ultrasonic motor.