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Determination of optimal contact position of a standing wave ultrasonic motor with funnel-shaped vibrator

The mechanical performances of standing wave ultrasonic motors are strongly dependent on contact positions. To determine the optimal contact position of standing wave ultrasonic motor with complicated vibrator, a single mode standing wave ultrasonic motor with funnel-shaped vibrator and small rotor was proposed and investigated. The intermittent push between the vibrator and the rotor is modeled as node-to-surface contact which also takes the asymmetric contact pressure distribution into consideration. The product of displacements in normal direction and circumferential direction is derived as the main factor that determining the relative driving abilities of different contact points, experimental results show that using this product to determine the optimal contact position, the motor can obtain the largest stall torque among the nodes along the circumferential edge of contact surface.