四自由度压电微夹钳的设计

Design of a 4-DOF Piezoelectric Micro-gripper

为降低微夹钳前端执行机构的复杂度,探索四自由度压电微夹钳的实现问题。通过在被设计成夹钳形状的两个压电单晶片的非黏结面上制作相互绝缘的驱动电极,且使两个非黏结面上驱动电极相互对齐的方法,设计出了可同时产生夹持方向与垂直于夹持方向位移的四自由度压电微夹钳;采用压电悬臂梁变形理论,推导出了钳指位移同钳指几何参数、驱动电压的关系,进而在对钳指进行尺寸优化的基础上,采用有限元方法分析了其静动态特性;最后,对微夹钳的静动态特性进行了测试,结果表明:当驱动电压为60 V时,左钳指、右钳指在夹持方向上的位移分别为25.7μm、26.1μm,左、右钳指在垂直于夹持方向上的位移分别为33.5μm、32.8μm,钳指位移具有很好的重复性;微夹钳在夹持方向和垂直于夹持方向的固有频率分别为2.35 k Hz、0.62 k Hz;在15 V的阶跃电压作用下,微夹钳在夹持方向和垂直于夹持方向的响应时间均为0.23 s。

To reduce the complexity of micromanipulation system, a 4-DOF piezoelectric micro-gripper is proposed. Firstly, a 4-DOF piezoelectric micro-gripper is designed using the piezoelectric bimorph actuators. The gripper could bring displacements both in the gripping direction and the vertical direction. The gripper is composed of two unimorphs which is designed as clamp shape. The driving electrodes of the gripper are fabricated on non adhesive surface of each unimorph. The driving electrodes on the unimorph are mutually insulated and aligned with each other. Secondly, the relationships between the displacement and the geometric parameters of the finger, as well as driving voltage are deduced based on the bending theory of piezoelectric cantilevers. Then the static and dynamic characterizations of the optimized gripper are analyzed using ANSYS. Finally, the static and the dynamic performances of the micro-gripper are tested experimentally. The results show that： at the driving voltage of 60 V, the displacements of the left and right finger in the gripping direction are 25.7 μm and 26.1 μm, respectively; the displacements of the left and right finger in the vertical direction are 33.8 μm and 32.8 μm, respectively. The displacements of two fingers have good repeatability. In the gripping direction and the vertical direction, the natural frequencies of the gripper are 2.35 k Hz and 0.62 k Hz, respectively. The response time of the micro-gripper in the gripping direction and vertical to the gripping direction are both 0.23 s at the step voltage of 15 V.