Modal frequency modification of an ultrasonic motor stator
The stator of a rod shape ultrasonic motor using bending modes is axially symmetrical as a whole,and has degeneracy in which two transverse bending vibration modes have the same shape and same modal frequency.In reality,due to influence of heterogeneous materials,irregular clamping pressure of screws,or a machining error,the modal frequencies of natural modes of two phases dont coincide with each other.In this study,it is verified from theory that when the stator has different modal frequencies of two phases,the motor will have an unstable rotary speed.Moreover,motor efficiency is also decreased.To make the modal frequencies of two phases coincide with each other,this paper presents a modification technique for the rod shape ultrasonic motor stator.According to the structural perturbation theory,a recess portion is formed in a predetermined portion of the stator,or an appropriate mass is added thereto so as to change the modal frequencies of the stator.The modal frequencies of an updated stator are calculatdby solving dynamic equations.The adjustment position is located on basis of the modal analysis of the stator using FE software.A stator of rod shape ultrasonic motor is fabricated.The difference of modal frequencies of two phases is 1.86 kHz.After chamfered portions have been formed above the circumferential groove of the stator,the modal frequencies of two phases perfectly coincided with each other,and the degeneracy of the stator modes is realized.The modification technique presented in this study allows one to adjust the modal frequencies of the stator in an assembled state.As a result,a motor can be manufactured at low cost and motor performances can be improved.
ultrasonic motor stator modal frequenc structural perturbation
Jiantao Zhang Hua Zhu Chunsheng Zhao
Precision Driving Laboratory,Nanjing University of Aeronautics & Astronautics,Nanjing 210016,China
国际会议
南京
英文
326-334
2007-09-09（万方平台首次上网日期，不代表论文的发表时间）