【作者】 董浩民；

【导师】 王代华；

【作者基本信息】 重庆大学 ， 仪器科学与技术， 2011， 硕士

【摘要】 随着微纳米技术(Micro/nanotechnology)和微机电(Micro-electro Mechanical Systems, MEMS)系统的兴起和发展,对多个微小零件装配成复杂的微机电系统的微装配与微操作技术成为迅速发展起来的一个研究领域。微夹钳在微操作和微装配过程中直接与夹持对象接触,其作为微操作和微装配系统中典型的末端微执行器,对微操作和微装配任务的实现有着重要的作用。微夹钳技术是一门涉及微机械、材料、传感器、自动控制、电子技术和计算机等的交叉学科,在微机械、微电子学、光学、微流体和生物科学等领域有着广泛的应用。装配零件的尺寸和形状都不固定,而且容易变形和破碎。一方面微夹钳的夹爪位移应行程大、分辨率高,在显微视觉视场中可以准确地移动;另一方面为避免损伤微型零件,应对夹持力进行传感和反馈控制。因此,研究具有大行程、高分辨率的夹爪位移,并集成夹持力/位移传感器和反馈控制的微夹钳具有重要的意义。本文在开发的夹爪平行移动的压电驱动微夹钳基础上,建立了力/位移输入输出关系模型,并对动力学模型进行了改进。分析了微夹钳的单片柔顺机构的传感特性,集成了夹持力和夹爪位移传感器,并完成了传感器的标定。建立了实验平台并对微夹钳的夹持力特性进行了测试。在集成传感基础上,辨识了微夹钳的驱动电压与夹持力和夹爪位移之间的关系模型。研究了力/夹爪位移的反馈控制技术,采用了PID反馈和模型参考自适应控制来提高夹持力/夹爪位移的控制精度。本文的主要研究工作和成果包括:1.在开发的压电致动微夹钳的基础上,对微夹钳的夹持力和夹爪位移的性能进行了分析。运用伪刚体模型法建立了微夹钳的单片柔顺机构的夹持力、输入力、夹爪位移与输入位移之间的关系模型并进行讨论。对原有的单片柔顺机构的动力学模型进行了改进。理论分析为微夹钳夹持力的传感与控制提供了理论基础。2.分析了微夹钳的单片柔顺机构在夹爪移动和夹持物体过程中的应变特性及实现夹爪位移传感和夹持力传感的可行性,分别建立了单边柔顺铰链最大应变与输入力、夹爪位移,柔性梁最大应变与梁变形、夹持力的之间关系模型,并与有限元仿真结果进行比较。利用ANSYS软件仿真分析了单片柔顺机构的应变特性和粘贴的应变片的应变分布。仿真结果表明,可在单片柔顺机构单边柔顺铰链和柔性梁上分别粘贴应变片构成夹爪位移传感器和夹持力传感器,并且传感器输出呈线性关系。3.在单片柔顺机构的单边柔顺铰链和柔性梁上分别粘贴半导体应变片实现了夹爪位移和夹持力的测量,并利用惠斯通单臂电桥和差动电桥连接实现了传感信号的转换和处理。根据微夹钳的单片柔顺机构的夹爪平行移动的特点,利用标准悬臂梁的受力与梁弯曲变形之间关系,提出一种利用非接触式位移传感器测量柔性梁的形变量来实现夹持力传感器标定的方法。4.建立了相应的实验装置分别对夹持力传感器和夹爪位移传感器进行了标定,实验测试了微夹钳的夹持力特性并与理论模型进行了比较,给出了夹持微小物体的实验来模拟实际的夹持过程。实验结果表明,微夹钳的夹爪位移与输入力、夹持力与输入力呈线性关系,夹持力模型符合实际的夹持过程。5.在集成传感基础上,辨识了微夹钳的驱动电压与夹持力和夹爪位移之间的关系模型。研究了力/夹爪位移的反馈控制技术,采用PID反馈和模型参考自适应控制来提高夹持力/夹爪位移的控制精度。为了验证反馈控制系统的有效性,对系统进行了仿真研究。仿真结果表明,夹持力/夹爪位移的PID控制的误差呈周期性变化,而自适应控制对期望输入的跟踪控制误差小,控制效果较好。本文的研究工作为压电驱动微夹钳的单片柔顺机构的设计、分析与控制提供了理论基础和设计方法。更多还原

【Abstract】 Micro-assembly and micromanipulation, which assemble parts with extremely small dimensional size as a complicated micro-electro mechanical system (MEMS), is a rapidly developed field with development of micro/nanotechnology and MEMSs. Microgrippers, which directly contact the operated objects as the end-effectors of micro-assembly and micromanipulation systems, play a crucial role in micro-assembly and micromanipulation. Microgripper technology, which involves micro-machinery, materials, sensors, automation, electronics, and computers, is widely applied to MEMS, microelectronics, optics, microfluidics and biological sciences, and other fields. The size and shape of operated objects are not fixed and fragile. On the one hand, microgrippers should possess large tip displacement with high resolution and be moved accurately in vision field of microscopes. On the other hand, in order to avoid damaging micro-parts, the gripping force should be monitored and feedback controlled. Therefore, microgrippers with large tip displacement, high resolution, integrated gripping force and tip displacement sensors, and feedback controller are desired.In this thesis, based on a piezoelectric-driven microgripper with parallel movement of gripping jaws, the relationships between the input and output of the gripping force/tip displacement are established, and the dynamic model is improved. The monolithic compliant mechanism (MCM) is integrated with gripping force sensor (GFS) and tip displacement sensor (TDS) based on analyzing the strain of the MCM, and both the gripping force sensor and tip displacement sensor are calibrated. The gripping force characteristics of the developed microgripper are tested using the established experimental setup. Based on the integrated gripping force sensor tip displacement sensor, the relationships between the applied voltage and the gripping force and tip displacement are modeled. The PID feedback control and model reference adaptive control (MRAC) are applied to improve the control accurary of the gripping force and tip displacement.The major research works completed in this thesis include:1.Based on the developed piezoelectric-driven microgripper, the characteristics of the gripping force and tip displacement are analyzed, and the relationships between the gripping force, input force, tip displacement, and input displacement of the MCM for microgrippers are established with the pseudo-rigid-body-model (PRBM) method and analyzed. The original dynamic model of the MCM has been improved. The theoretical analyses have established a theoretical foundation for monitoring and control of the gripping force.2.The strain characteristics of the MCM and the possibility of monitoring griping force and tip displacement are analyzed. The relationships between the maximum strain of the single-notch flexure hinges with the tip displacement and input force, and the relationships between the maximum strain of the cantilever beams with the gripping force and the deformation cantilever beams are established, respectively. Comparisons between the theoretical models of strain characteristics for the MCM and the simulation results using FEM are carried out. The strain characteristics of the MCM and the strain distribution of the strain gauges bonded onto the MCM are analyzed using ANSYS software. The research results indicate that the strain gauges can be bonded onto the single-notch flexure hinges and the cantilever beams as tip displacement sensor and gripping force sensor, respectively, and the outputs of sensors are linear.3.The tip displacement and gripping force are measured by semiconductor strain gauges pasted at the single-notch flexure hinges and the cantilever beams, and the outputs of strain gauges are transformed and processed by Wheatstone bridge. Based on the parallel movement of the jaws and the cantilever beam bending theory, a method to calibrate the gripping force sensor by using a non-contact displacement sensor to measure the deformation of the cantilever beam is proposed.4.The gripping force sensor and tip displacement sensors are calibrated using the established experimental setup. The gripping force characteristics are tested and compared with the theoretical model, a case of gripping a micro object to simulate the gripping process is shown. The experimental results indicate that the relationship between the tip displacement and input force, and the relationship between the gripping force and input force are linear. Theoretical model of the gripping force can predict the actual gripping process.5.Based on the integrated gripping force sensor and tip displacement sensor, the relationships between the applied voltage and the gripping force and tip displacement are modeled. The PID feedback control and model reference adaptive control are applied to improve the control accurary of the gripping force and tip displacement. In order to evaluate the proposed method, the corresponding simulation system is established and experimently verified. The simulation results indicate that the control error by the PID feedback control is periodical, while the tracking control error of the adaptive control for the gripping force and tip displacement is small, and the control accurary by the adaptive control is better than the PID control.The research works in this thesis provide theoretical basis and method for design, analysis, and control of MCMs for microgrippers.更多还原