真空环境下行波型超声波电机的特性

真空环境下由于缺少空气介质，靠摩擦驱动的超声波电机的特性会与常态 下发生较大的变化。采用行波型超声波电机常用的三种摩擦材料（环氧树脂、聚四氟乙 烯烧结和生聚四氟乙烯填充为基的摩擦材料）对比分析了常态和真空环境下的超声波电机的 机械特性。发现除环氧胶外，其他摩擦材料制成的电机真空下的堵转力矩都有所增大，而空 载转速全部降低。为了分析变化产生的原因，实验比较了真空环境下三种摩擦材料在常规、 驻波和行波状态下的动摩擦系数，实验表明除环氧胶外其它摩擦材料的摩擦系数比常态下都 略有增大,且相应电机的堵转力矩也都增大。其次实验研究了行波型超声波电机的瞬态特性 ，当真空度增加到10 -2 Pa后，电机的起动时间和起动电压都有明显的增加，即电 机起动和运行的阻力逐步增大，导致电机空载转速的降低。最后测试了声悬浮力大小，其数 值不超过预紧力的1％，不是真空环境下特性变化的主因。导致电机真空环境下堵转力 矩和空载转速发生变化的主要原因在于摩擦材料动态摩擦系数和起动与运行阻力的变化。

Ultrasonic Motor's Characteristics in Vacuum

Uhrasanic motor's characteristics could change a lot in vacuum, as lacking of air. This paper described the motor's mechanical characteristics both in normal and vacuum condition with three fi'iction materials, agglomerated-PTFE, unag-glomerated-PTFE and epoxy-colophony. The max torque goes up in vacuum expect sepoxy-coiophony, and the max speed all goes down. To find the reason, this paper give the dynamic friction coefficient's experiment and finded it increasing up in convention-al, standing wave and travelling wave from normal to vacuum except sepoxy-colophony. Then, this paper tested the transient char-acteristics in vacuum, and finded the starting time and starting voltage grow up when the vacuum' degree went up to 10-2Pa. At last, this paper give the acoustic levitation force's numerical and fined it is about 1% in preload, which deserted the affect of acoustic levitation force in vacuum. The most factors which affecting the motor's mechanical characteristics are dynamic friction coefficient and the starting and run-time resistance.