Traveling Wave Ultrasonic Motor Research Articles

Linear motor using a quasi-travelling wave in a rectangular plate

Usually, ultrasonic motors generate a rotating movement, particularly motors using a travelling wave. Due to axial symmetry, production of this type of wave in a circular shape is easier than in others shapes. In this paper, we show that it is possible to generate a linear movement using a quasi-travelling wave in a rectangular plate. If the dimensions of the plate are well adjusted, the combination of two resonant modes, for example 2-1 and 1–3 modes, which have the same frequency, will, with suitable excitation, produce a quasi-travelling wave. A linear motor using a rectangular plate has been made to demonstrate the principle. This type of actuator will of course present the same advantages as in the usual travelling wave ultrasonic motors. In addition, the use of rectangular shapes is suitable for miniaturisation, for example, in the case of chemically etched silicon membranes.

Two‐dimensional finite element analysis of a synthetically loaded stator in a piezoelectrically driven ultrasonic motor

Ultrasonic motors have attractive properties which compare favourably with electromagnetic motors for certain applications. Their operation is based on piezoelectrically exciting bending waves in the stator and transferring energy to the rotor via friction. Prototypes are typically constructed by trial and error; theoretical studies have proved to be difficult. Describes a two‐dimensional model for the stator of a travelling wave ultrasonic motor. The authors have developed a finite element program that is capable of modelling piezoelectric driven systems in the time domain, and their objective is to simulate the excitation of the travelling waves in the stator. They are in fact able to simulate travelling waves. Although the plane strain model cannot account for all excitation modes, they observe the elliptical motion of the material particles on the surface, implying that rotor motion can be mechanically induced.

Adjustable Compliant Motion of Ultrasonic Motor

As actuators for a prosthetic arm, we used traveling wave ultrasonic motors. The arm must move in compliance with the environmental force around every joint of it as in the human arm. In order to realize the compliant arm, it is desired that the actuator have an adjustable compliance and damping characteristics without interaction force control. However, the traveling wave ultrasonic motors have no compliant characteristic in itself. Then, we developed an adjustable compliance and damping system. for the motor. The system was realized by a phase difference control loop of two-phase driving signals of the motor within the PD control loop of the shaft angle. This system acts much like an adjustable spring with an adjustable damper.

Travelling wave ultrasonic motors, Part I: Working principle and mathematical modelling of the stator

Travelling wave ultrasonic motors have recently been attracting considerable attention: they may possibly soon replace—at least in certain areas—small electromagnetic motors. This development has been made possible by recent advances in power electronics, material research and digital control, which allow utilization of the piezoelectric effect for low power motors. In these motors the mechanical energy is generated with frequencies of the order of 40 kHz via piezo-elements producing bending waves in a stator, which has approximately the form of a circular plate. The rotor is then driven by the stator via contact forces, and with an extremely simple mechanism frequency reductions of 1:40 000 and more are obtained between the stator vibration and the rotor motion. As a consequence, one can work in the 40 kHz range on the electrical side, while a low frequency rotation is obtained on the mechanical side, as is desirable for many applications. In the present paper, which is the first of a series, the working principle of travelling wave ultrasonic motors is reviewed, and the main phenomena are mathematically modelled. In further papers a detailed mathematical description of the stator vibration and a first model of the contact problem will be given.

Estimation Of The Tangential Stresses In The Stator/Rotor Contact Of Travelling Wave Ultrasonic MotorsUsing Visco-elastic Foundation Models

A new stator/rotor contact model of travelling wave ultrasonic motors is developed, in which the stick/slip behavior within the contact area is taken into account. The distributions of displacement and velocity and normal and tangential interface forces between rotor and stator are calculated. The results allow to estimate motor performance like e.g. the torque-speed curves as a function of the motor's parameters. Furthermore, the influence of main material and geometrical parameters and different operating conditions are investigated. The mathematical model developed in this paper can be used as a design tool for optimizing motor performance with the flexibility for a wide variety of geometries and materials.