Abstract
The objective of this thesis is to report the single vibration mode standing wave tubular piezoelectric ultrasonic motors developed. Piezoelectric motors are driven by reverse piezoelectric effects which converts an input of ultrasonic frequency of electrical energy into an output of mechanical movement. There are many advantages of piezoelectric ultrasonic motors compared to electromagnetic motors such as simple structure, high energy density, and high torque at low speed. Three prototypes are designed and fabricated. Two motors are fabricated using PZT cylindrical tube; one with PZT teeth and the other with metal teeth. A third motor using brass tube with PZT plates attached is fabricated. After design and fabrication of three prototypes, the performances of the motors are tested using a test apparatus for speed and torque.
Highlights
When pressure is applied on the piezoelectric materials, a charge density appears on the surface which generates an electric field
The generation of an electric field under stress is called direct piezoelectric effect while reverse piezoelectric effect refers to deformation of piezoelectric materials under application of an electric field
When an electric field at a frequency in ultrasonic range is applied onto the piezoelectric ceramics as the mechanical vibration source, the piezoelectric ceramics can either expand or contract according to the direction of electric field and poling direction of the piezoelectric material
Summary
The term piezoelectricity comes from Greek reference meaning electricity by pressure. When pressure is applied on the piezoelectric materials, a charge density appears on the surface which generates an electric field. This leads to a flow of free charges. The piezoelectric effect in those natural materials is very small in magnitude and improved properties in polycrystalline ferroelectric ceramic materials such as barium titanate and lead zirconate titanate (PZT) have been developed [3]. Variable sE is the elastic compliance at constant electric field, d and dt are the piezoelectric strain coefficients for direct and reverse effects, and εT is the dielectric permittivity
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