| Ultrasonic motor (USM) is a new kind actuator developed during recent three decades, which transform micro displacement into macro motion of rotators via resonant amplifying and frictional effect by using converse piezoelectric effect and ultrasonic vibration. Presently, almost all the practically used USM have only one degree of freedom (DOF), such as linear or rotary movement. However, special actuators realizing multi-degree of freedom motion (multi-DOF) are in great demand in the area of ball-shape bionic joints, flexible joints and eye balls of rotots and moon explorer vehicles. Due to the structure flexibility and multi motion way, USMs are suitable to realizing multi-DOF motion. The research on the structure and application on the multi-DOF USM in the world is in the investigating stage until now. The existing multi-DOF USMs realize multi-degree of freedom motion by superimposing several independent actuation, then impediment and interference occurs leading to an unsatisfactory mechanical output. The research on this topic can bring forward new thinking and build theoretical foundation for multi-DOF spherical USM. Meantime, the application area of multi-DOF USM can be broadened with significant practical meaning.Based on the Langevin transducer driving process and working principle, this dissertation carried out research on the coupling relation of active longitudinal and passive bending vibration on transducer driving performance. By adopting parametric finite element method (FEM), those dimension parameters, which were more sensitive to transducer longitudinal and bending vibration, were selected to perform optimization design. The optimization method was verified to be correct and feasible by analyzing the optimization results using FEM.A quadric transducer coordinately driving spherical USM was proposed and fabricated. This kind of USM has merits such as simple structure and high output torque. The spherical USM actuated through driving four orthogonally arranged Langevin transducer coordinately. The output mechanical properties were tested by experiment, and the maximum rotary speed is 12r/min, the maximum output torque is 0.45 N·m.A cross orthogonal horn was proposed to build foundation for study single vibrator multi-DOF transducer. Comprehensive analysis was carried out on structure parameters of the single vibrator longitudinal-bending transducer, thereby the parameters'influence tendency towards the eigenfrequencies was got to realize longitudinal-bending modal degeneration. Positions of piezoelectric ceramics were determined by using effective electromechanical coupling factor. The exciting way of getting three type orthogonal elliptical trajectories on the particle of the driving foot was proposed. The investigation of elliptical trajectories of the driving foot particle was performed through transient analysis of FEM.A multi-DOF spherical USM based on single longitudinal-bending transducer vibrator was proposed and studied. This kind of USM has merits such as high output torque, simple driving and easy controllability. The output mechanical properties were as follows: when revolving around X and Y axis, the output torque was 0.97 N·m and the maximum rotary speed was 11r/min; when revolving around Z axis, the output torque was 0.27 N·m and the maximum rotary speed was 66r/min.
|
PDF Full Text Request