提出一种塔形双模态直线超声电机。它由塔型定子和导轨组成,塔型定子由6片压电陶瓷(piezoelectric lead zirconate titanate ceramic,PZT)粘接在金属弹性体上构成。定子利用y-z面内对称振动模态激发驱动足的法向振动,利用x-z面内2阶弯振模态激发驱动足的切向振动。由于驱动足的法向振动和切向振动存在90°的相位差,从而在其驱动足处形成椭圆运动,推动导轨运动。讨论电机支撑位置与激振方式和位置,研制了电机样机及其实验装置。提出了一个新观点:电机工作性能与定子在接触边界条件下的频率一致性有关。通过接触边界条件下的模态实验确定了电机的最佳工作点,并在电机的最佳工作点附近进行了机械特性实验。实验表明,在激励电压峰峰值为500 V、预压力6 N下,该电机最大空载速度为980 mm/s,最大输出力1 N,定子质量为20 g,推重比(输出力与定子重量之比)达5。
A tower-shaped dual-mode linear ultrasonic motor(LUSM) was presented.The motor was composed of a tower-shaped stator and a slider.The stator used six piezoelectric lead zirconate titanate ceramic(PZT) plates sticked to a metal elastomer to form an actuator.The stator used symmetric vibration mode in y-z plane to excite normal vibration of the driving tip,and used bending vibration mode in x-z plane to excite tangential vibration of the driving tip.Because of 90? phase shift between the normal and the tangential vibration,elliptical motion of the driving tip was obtained,so the slider was pushed to move.The problems of where to hold the motor and excite the mode,and how to excite the mode were discussed.A prototype and its test equipment were fabricated.The following new point was presented: the working performance of the motor is dependent on the frequency consistency on the condition of contacting.The optimum working point of the motor was obtained from the modal testing on the condition of contacting.Then the testing of mechanical characteristics was accomplished near the optimum working point.When the peak value of exciting voltage is 500 V and the pre-pressure is 6 N,the maximal velocity with no load is 980 mm/s and the maximum output force is 1 N.Because the stator's mass is 20 g,the thrust-weight ratio(the ratio of output force to stator's weight) is 5.