Design, modeling and control of a novel multi functional translational-rotary micro ultrasonic motor.

摘要

The major goal of this thesis was to design and develop an actuator, which is capable of producing translational and rotary output motions in a compact structure with simple driving conditions, for the needs of small-scale actuators for micro robotic systems. Piezoelectric ultrasonic motors were selected as the target actuator schemes because of their unbeatable characteristics in the meso-scale range, which covers the structure sizes from hundred micrometers to ten millimeters and with operating ranges from few nanometers to centimeters.;In order to meet the objectives and the design constraints, a number of key research tasks had to be undertaken. The design constraints and objectives were so stringent and entangled that none of the existing methods in literature could solve the research problems individually. Therefore, several unique methods were established to accomplish the research objectives. The methods produced novel solutions at every stage of design, development and modeling of the multi functional micro ultrasonic motor.;Specifically, an ultrasonic motor utilizing slanted ceramics on a brass rod was designed. Because of the unique slanted ceramics design, longitudinal and torsional mode vibration modes could be obtained on the same structure. A ring shaped mobile element was loosely fitted on the metal rod stator. The mobile element moved in translational or rotational, depending on whether the vibration mode was longitudinal or torsional.;A new ultrasonic motor drive method was required because none of the existing ultrasonic motor drive techniques were able to provide both output modes in a compact and cylindrical structure with the use of single drive source. By making use of rectangular wave drive signals, saw-tooth shaped displacement profile could be obtained at longitudinal and torsional resonance modes. Thus, inheriting the operating principle of smooth impact drive method, a new resonance type inertial drive was introduced. This new technique combines the advantages of inertial method with resonance drive. The motor that combines inertial drive at resonance will be a new type of ultrasonic motor, according to the classification of vibration types.;A method to analyze the stator vibration by incorporating the piezoelectric loss coefficients was developed. By using the model, natural frequencies of the operating modes were predicted and exact formulations of the vibration displacements in longitudinal and torsional modes were obtained. The vibration model was in perfect agreement with the ATILA finite element analysis simulations even for different design parameters. The model was also used in design optimization and for theoretical explanation of the newly introduced motor drive technique. The theoretical analysis of the operating principle was verified with finite element analysis simulations and by vibration measurements.;Several prototypes of motor were built in order to realize the dual function output as the main objective of this research. Translational output was observed for rectangular wave input signals at the resonance frequency of the fundamental longitudinal mode.The output mode changed to the rotational mode when the operating frequency switched for the fundamental torsional mode. While the mode of motor could be switched by switching the operating frequency, the direction of motion could be reversed by switching the duty cycle of rectangular input signals from D % to (100-D) %. A prototype (5 mm diameter, 25 mm total length produced 55 mm/s (translational) and 3 rad/s (rotary) speed under 40 mN blocking force, when the input signal was 40 V pp rectangular with 33% duty cycle. The motor speed at translational mode was characterized for different input voltage and output force.;The meso-scale ultrasonic motor which utilizes smooth impact drive method, provided a unique ability to produce dual function with prominent output characteristics in a compact structure by using simple drive conditions.