弯振复合型超声驱动器振动特性研究

为了避免模态复合型超声驱动器中普遍存在的频率简并问题，作者在前期研究中提出了一种新型的弯振复合型超声驱动器。该驱动器采用压电金属复合梁两个正交弯振模态的复合在两个驱动足处激励出椭圆轨迹振动。本文对该驱动器的振动特性进行深入研究，旨在获得驱动区域质点的真实运动轨迹。首先，建立了矩形截面梁在弯振复合模态下末端区域质点振动轨迹的数学模型；然后，借助有限元瞬态分析，对驱动足振动轨迹进行仿真，实现对所建立振动轨迹数学模型的验证。振动轨迹方程和仿真结果均表明：两个驱动足表面质点振动轨迹均为三维的椭圆，垂直于驱动器轴线的平面内的椭圆振动更适合用于致动输出。最后，分析了该驱动器存在的不足之处，提出了一种改进方案，采用对称设置压电陶瓷片实现两个驱动足振动特性的一致；通过瞬态分析在两个驱动足处得到了一致的振动轨迹，改进的样机实现了输出特性的显著提高。

Vibration characteristics of an ultrasonic actuator with composite bending vibration modes

In order to avoid the modal frequency degeneration problems that commonly existed in ultrasonic actuator using composite vibration modes, the authors have presented and developed an ultrasonic actuator using composite bending vibration modes. In that new design, two orthogonal bending modes of a piezoelectric-metal composite beam are superimposed to produce elliptical vibrations on the two driving feet. This paper intends to obtain the motion trajectories of particles on the driving region by studying the actuator’s vibration characteristics. Firstly, the vibration trajectory equation of particle on the tip end of rectangle beam under the composition of bending vibration modes is founded. Then, transient analysis is developed to gain the vibration trajectories of nodes on the driving feet, which verify the correctness of the founded vibration trajectory equation. Both the theory and simulation analysis results indicate that the motion trajectories of particles on the driving feet are three-dimensional ellipses; the elliptical vibration in the plane that vertical to the axial of the actuator is more suitable for actuating. Finally, the disadvantage of the actuator is analyzed; an improved program to realize the consistent vibration on the two feet by a symmetric setting of the PZT ceramics is presented. Transient analysis states that the same ellipses are produced on the two feet; which helps the modified prototype has larger speed and thrust force.