Research On Ultrasonic Motor Using Bending Vibration Transducer

As a new actuator, ultrasonic motor exhibits merits such as high energy density, high torque under low speed, fast response, high position accuracy, no electromagnetic interference, etc. For the merits given above, ultrasonic motor has a broad of applications in many high-tech areas.The increasing of output power and efficiency is one of the main directions of domestic and international research. Composite mode ultrasonic motor become a research focus, which exhibits advantages such as large torque or thrust, high output speed, etc. However, as its shortcoming, the mode degeneration problem limits the flexibility of the motor structure and the improvement of performance. Ultrasonic motor using bending vibration transducer avoids the problem successfully, which is the research interest of this paper.Firstly, the structure and operating principle of ultrasonic motor using bending vibration transducer was introduced. The second-order bending vibration mode applied by such ultrasonic motor was analyzed, while the elliptical motion trajectories of the two driving feet was deduced. The materials of the prototype and their properties were described, which are required in the simulation analysis. In the equivalent circuit simulation, it is knew that the lower the static capacitance of the equivalent stator can result in a higher electromechanical coupling efficiency and the larger the stiffness of the stator can result in a higher electromechanical coupling efficiency, and can result in a higher mechanical quality factor. Finally, based on the theory of admittance circle, the corresponding electrical equivalent circuit parameters were obtained.By adjusting the size parameters of ultrasonic motor, the relationship of among modal characteristic frequency, electromechanical coupling efficiency and the structural parameters was analyzed by means of ANSYS modal analysis. Two miniaturization models were proposed. By contrasting two models, it is founded that the smaller one has a higher resonant frequency and a larger energy density. The smaller one of two miniaturization models was fabrication. Typical output of the prototype is no-load speed of 744mm/s and maximum thrust force of 15N.The effects of different region exciting of the PZT ceramics on the vibration strength of driving feet are analyzed. Analysis results show that the contribution of different regions of the PZT meets the principle of superposition and the PZT away from the neutral plane of the bending mode shape offer more contribution to the bending vibration of the motor under the same exciting voltage, compared with the PZT that near to the neutral plane. Based on the study results, by changing the setting of ceramics, a novel exciting way of USM using bending vibration modes is proposed, and its prototype was fabrication. But there is a large deviation between the experimental results and simulation ones. By studying on the above issues, a modified configuration was developed and fabricated. Simulation analysis and experimental tests verified that the partition excitation of bending vibration ceramic can improve the energy conversion efficiency. Typical output of the modified one is no-load speed of 748mm/s and maximum thrust force of 25N.