| Abstract |
Ultrasonic motors (USMs) are increasingly being developed for their potential to replace electromagnetic motors due to their high torque density, low power consumption, and their ability to be miniaturized. Ultrasonic motors have been used in different applications including autonomous vehicles, mobile robots, and autofocus systems in digital cameras. One potential application for USMs is LiDAR systems, which are key components in autonomous vehicles in the near future.
This thesis presents a novel design of a compact standing-wave rotary USM based on a coupled axial-tangential mode, one power source, and a bulk piezoelectric actuator of a tube form. The excitation wave type and the actuator shape are the only two fixed parameters in this study. The other parameters investigated in this thesis are electrode configuration parameters, such as the number of electrodes, active electrode length, active electrode location, and applied voltage; geometrical parameters, such as tube height, wall thickness, and outer radius; drive-tip location, and stator-housing mounting.
Both radially-polarized and axially-polarized piezoelectric PZT tubes are investigated in this thesis. A finite element model (FEM) is developed for the piezoelectric stator only and for a stator- rotor connection. Furthermore, the USM electric circuit model is studied based on an experimental assessment of the piezoelectric tube.
In conclusion, the coupled axial-tangential mode can successfully be utilized for USM design, and can achieve no-load speeds up to 500 rpm. In addition, axially-polarized PZT tubes are capable of producing a symmetrical axial-tangential mode compared to the radially-polarized ones. To check the validity of the developed design and the FEM model, capacitance testing, impedance testing, and axial-displacement testing are conducted. The results show an agreement between both simulation and experimental results but with a noticeable error. Sources of error such as mechanical damping of the system are discussed and a power consumption analysis is presented.
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