Exploiting solid state ultrasonic motors for robotics

The authors describe the design and implementation of a small parallel jaw gripper driven by a resonant structure ultrasonic motor. The motor is capable of generating 10 oz of force in linear motion and has a static holding force greater than 10 oz in the power-off state due to the high-friction nature of the design. The manipulator designed to utilize these properties is a precision-machined module requiring 0.5 in ³. Based on a parametric model of the motor, a position controller was designed and tested. The closed-loop step responses show that the gripper behaves asymmetrically with respect to opening and closing. The fact that different sets of piezoelectrics are responsible for each direction of motion is most likely responsible for this asymmetry. Nevertheless, the feasibility of a linear-motion actuator driven by a compact resonance-mode ultrasonic motor was demonstrated