Linkage-driven manipulator with embedded ultrasonic motors

This paper proposes a linkage-driven manipulator having linear ultrasonic motors inside of an elongated shaft. The manipulator can be divided into a driving rod module and wrist joint module. The driving rod module consists of several ultrasonic motors and driving rods. Flexible leaf springs between the ultrasonic motors and the driving rods enable synchronized motion of the driving rod by compensating mechanical clearance and different characteristics of ultrasonic motors. Two driving rods operate 2-DOF wrist module by linear motion. The wrist joint module is composed by two non-closing rotation joints, serially connected sliders and intermediate linkages, and designed to rotate from +60° to -60° in yaw and pitch directions respectively. The wrist parameters are determined by parametric studies of the motion range and torque characteristic, and the effect of the flexible leaf spring is studied by simulation. Experiments are performed in order to evaluate the velocity-force characteristic of the rod module.