A novel large thrust-weight ratio V-shaped linear ultrasonic motor with a flexible joint.

A novel large thrust-weight ratio V-shaped linear ultrasonic motor with a flexible joint is proposed in this paper. The motor is comprised of a V-shaped transducer, a slider, a clamp, and a base. The V-shaped transducer consists of two piezoelectric beams connected through a flexible joint to form an appropriate coupling angle. The V-shaped motor is operated in the coupled longitudinal-bending mode. Longitudinal and bending movements are transferred by the flexible joint between the two beams. Compared with the coupled longitudinal-bending mode of the single piezoelectric beam or the symmetrical and asymmetrical modes of the previous V-shaped transducer, the coupled longitudinal-bending mode of the V-shaped transducer with a flexible joint provides higher vibration efficiency and more convenient mode conformance adjustment. A finite element model of the V-shaped transducer is created to numerically study the influence of geometrical parameters and to determine the final geometrical parameters. In this paper, three prototypes were then fabricated and experimentally investigated. The modal test results match well with the finite element analysis. The motor mechanical output characteristics of three different coupling angles θ indicate that V-90 (θ = 90°) is the optimal angle. The mechanical output experiments conducted using the V-90 prototype (Size: 59.4 mm × 30.7 mm × 4 mm) demonstrate that the maximum unloaded speed is 1.2 m/s under a voltage of 350 Vpp, and the maximum output force is 15 N under a voltage of 300 Vpp. The proposed novel V-shaped linear ultrasonic motor has a compact size and a simple structure with a large thrust-weight ratio (0.75 N/g) and high speed.