【作者】 张帆；

【导师】 陈维山；

【作者基本信息】 哈尔滨工业大学 ， 机械电子工程， 2006， 博士

【摘要】 一个机械系统低速运行时,影响性能的一个重要问题就是摩擦振动的存在。学者们在不断的探寻高效的润滑技术来减小摩擦,实现机械系统的低速平滑运动。超声波马达是上世纪80年代开始发展起来的一种新型驱动器,它是利用压电陶瓷的逆压电效应激励出定子表面质点的椭圆轨迹振动,依靠摩擦耦合来实现驱动。本文研究新型超声波马达,利用其产生于摩擦界面的椭圆轨迹超声振动引起的润滑效应和摩擦接触行为的改变来减小摩擦力的大小,完成对摩擦力的主动控制,实现机械系统的低速平滑运动。首先利用赫兹接触理论建立了夹心式换能器和刚性平面的超声动态接触模型。通过对模型进行分析、求解表明,在纵向超声频率动态接触作用下,换能器节面位置产生了上浮,换能器端面与刚性平面的动态真实接触面积比静态时减少了。对该模型的分析很好地解释了纵向超声振动所引起的摩擦系数降低的现象,为提出利用椭圆轨迹超声振动来实现减摩奠定了理论基础。用微位移测试仪实际测试夹心式换能器节面沿纵向上浮的实验证实了该模型的分析结论。为提高驻波直线超声波马达的输出功率以满足减摩的要求,本文在其基础上提出了一种新型的直线超声波马达。该马达振子由夹心式换能器和加工有齿的金属薄板连接而成。夹心式换能器激励金属薄板产生弯曲模态的振动,从而通过作斜线轨迹振动的齿产生驱动力。文中研究了马达振子的声阻抗匹配问题以实现能量的高效传输,提出了复杂形状夹心式换能器的有限元设计方法。由于采用了机电转换能力较高的夹心式换能器替代压电陶瓷薄片来实现电声能量转换,相比传统驻波直线超声波马达,该马达能实现更高的驱动速度和更大的驱动力。基于纵向超声动态接触作用产生换能器节面上浮的理论分析,提出了可以实现双向驱动的换能器直线超声波马达。该马达振子由两个互成90o夹角的夹心式换能器构成,依靠倾斜的夹心式换能器驱动头的斜线轨迹振动产生驱动力。利用夹心式换能器振动时产生的上浮效应,该马达可以方便的实现双向驱动。利用有限元软件ANSYS建立了马达的有限元模型,对模型的分析计算表明,畸变的椭圆轨迹振动是马达产生驱动力的根本原因,同时计算结果也证实了超声动态接触作用会使马达产生上浮。在230Vrms电压下,该马达样机的最大测试速度达到947mm/s,最大推力为35N,最大输出功率12W。更多还原

【Abstract】 Since frictional vibration damages a mechanical system’s performances when the system works at a low velocity, efficient antifriction techniques are the key tasks that have been seeking after all along. Ultrasonic motors are a new kind of solid actuators that come into being since 1980’s, which use inverse piezoelectric effect of PZT to excite stator’s elliptical vibration and produce driving power by frictional coupling. In order to realize smooth movement of mechanical system at a low velocity, the following work investigates new types of linear ultrasonic motors and antifriction technique by superposing the motor’s elliptical vibrating motion at the friction interface to change frictional characteristics, produce ultrasonic lubricant effect and realize active control of friction force.The ultrasonic dynamic contact of bolt-clamped transducer and rigid plane are modeled using Hertzian contact theory, and the analyzing results reveal that the nodal plane of the bolt-clamped transducer is levitated in normal direction by the ultrasonic dynamic contact action, and the real area of contact of bolt-clamped transducer and rigid plane decreases in the same time. The established contact model has provided good explanation for the phenomena of the reduction of frictional coefficient induced by longitudinal ultrasonic vibration and has great academic significance in proposing friction reduction technology based on elliptical ultrasonic vibration. The normal levitation of nodal plane tested under ultrasonic dynamic contact action validates the normal dynamic contact model.In order to increase output power of conventional standing wave ultrasonic motors to satisfy the antifriction technique, this dissertation presents a new linear transducer-metallic plate type ultrasonic motor based on the conventional standing wave ultrasonic motor’s structure. The stator of this motor is composed of a bolt-clamped transducer and a metallic plate in which legs are machined. Through acoustic coupling of the transducer and the elastic plate, energy is transferred to the metallic plate, thus, the metallic plate’s flexural vibrating mode comes into being and driving force is produced by the legs’rectilinear motion.更多还原