An efficient performance evaluation method of the traveling wave rotary ultrasonic motor's flexible rotor.

For a traveling wave rotary ultrasonic motor, matching the stator with a proper flexible rotor can be challenging because of the actual contact mechanism's complexity. Due to the lack of effective evaluation and prediction means in the rotor design process, the prototype test is usually needed to truly measure how well it performs, leading to high cost and long design cycle. In order to solve this problem, an efficient performance evaluation method of the flexible rotor based on equivalent contact pressure is proposed. By the key parameters of the flexible rotor's contact surface (area and pressure), an equivalent pressure model of the contact surface is established, which reveals the influence law of the flexible rotor's structural parameters on the motor's output performance. It is doubly verified by dynamics simulation and experiments. The advantage of this method is that without dynamics computation and prototype test, only statics analysis can evaluate the matching score of flexible rotor and target stator quickly and accurately. This study is expected to provide support for the structure design and performance prediction of the traveling wave rotary ultrasonic motor's rotor, in which significant time and cost savings can be achieved.

Design and Dynamic Simulation of a Novel Traveling Wave Linear Ultrasonic Motor.

To overcome the problem of frequency consistency and simplify the design process of linear ultrasonic motor, a novel traveling wave linear ultrasonic motor with a ring-type stator is proposed in this paper. The combination of two orthogonal bending vibration modes with the same order is selected as the operating mode of the motor. A traveling wave along the side of the stator is utilized to drive the slider to move linearly. The stator adopts a ring symmetrical structure, which can effectively ensure that the resonance frequencies of the two vibration modes are consistent. Thus, we do not need to tune the frequencies of the two vibrations by constantly adjusting the shape of the stator or designing complex clamping parts to fix the stator without making any influence on the vibrations. Meanwhile, a three-dimensional finite element model of the motor is built. Using the model, we obtain the elliptical motion trajectories of the stator driving surface, the output performance of the motor, the sticking-slipping-separation contact characteristic between the stator and the slider and fabricate and measure a prototype of the proposed motor.

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.