A novel robotic arm driven by sandwich piezoelectric transducers

In this work, a novel robotic arm driven by sandwich piezoelectric transducers is proposed. The proposed robotic arm is composed of three arms and four joints. Each arm consists of a sandwich piezoelectric transducer and an H-shaped hollow frame. The sandwich piezoelectric transducer utilizes frictional force to drive the joints on its both sides to rotate simultaneously. The joint between two arms can be driven to rotate in two perpendicular directions by two sandwich piezoelectric transducers. The rotation of joints results in the arm motion. Utilizing the finite element method, the optimized geometrical parameters of the sandwiched piezoelectric transducer are obtained, and the operating principle is demonstrated. A prototype of the robotic arm is also fabricated and assembled, it is 573 g in weight and 412 mm in length, and the maximum rotation angle of each joint is 160°. The mechanical characteristics of the robotic arm prototype are investigated by experiments. The results indicate that, when the excitation frequency of one sandwich piezoelectric transducer is 37.4 kHz, the arms on its two sides rotate in opposite directions with an average rotational velocity of 320 deg/s at 330 V_pp, a resolution of 100 μrad at 230 V_pp, and a startup and shutdown response time of 40 ms and 30 ms at 230 V_pp, respectively.