Research On Micro Coiled Stator Ultrasonic Motor

The ultrasonic motor (USM) is a new type micro motor which utilizes inverse piezoelectric effect of piezoelectric materials and ultrasonic vibration of elastic materials to obtain output force. Due to its new driving principle, ultrasonic motors have many advantages, such as compact structure, large energy density, fast response, high control accuracy, no electromagnetic interference, no noise pollution and so on. USMs have a broad application prospect in the field of micro electro mechanical system. The miniature USMs whose structure parameters are under millimeter magnitude, have special advantages in micro scale field. The coiled stator ultrasonic motor (CSUSM) is a new micro motor using a spring as its stator. It has the simplest structure among the reported micro motors so far and can be minimized further.Two methods to excite traveling wave in coiled stator are introduced in this thesis, and motion equation of the driving points of the stators corresponding to the above two methods is deduced, which theoretically verifies the methods mentioned above can drive ultrasonic motor. Based on the methods mentioned above, two types of CSUSM are proposed:ring beam type and overhanging beam type.Ring beam type CSUSM is driven by a flexural traveling wave instead of the Lamb wave; therefore the problems such as multi-mode compound, complex theoretical analysis and overlength waveguide can be effectively solved. Owing to the closed loop structure, unidirectional traveling wave can be excited without a mechanical absorber, thus improving the utilization rate of the vibration energy. Based on the vibration model of Bernoulli-Euler beam, calculation formula of the ring beam structure parameters is deduced, and rationality of the design and calculation is verified by simulation. Using ANSYS, the influence of the stator cross sectional dimensions and excited frequency on the traveling wave and elliptical motion is deeply researched.Overhanging beam type CSUSM is driven by a flexural traveling wave generated by superimposing two bending vibration modes. An overhanging beam is fixed on both tips of the coiled stator to bond piezoelectric ceramics and in this way, the problem of unreliable pasting between the stator and piezoelectric ceramics can be solved. The stator is optimized with the goal of frequency degeneration by orthogonal test design method. Using ANSYS, dynamic analysis of optimized stator is done to obtain displacement response of selected driving points which can be used to analyze the vibration characteristics of the stator and verify the rationality of structure design.