Topology Optimization Of Compliant Mechanism And Its Application In Micro-Electro-Mechanical System

Compliant mechanisms are the type of mechanisms that use elastic deformation of flexible members to transfer force, motion or energy. These devices have good prospects in areas such as Micro-Electro-Mechanical Systems, precision position and smart structures due to their advantages such as elimination of friction and wear. In this dissertation, the topology optimization method of compliant mechanisms is deeply investigated. Based on topology optimization method, piezoelectric driven micro-gripper and thermal micro actuator is designed and tested.In this dissertation, a new method using nodal density as design variable of continuum topology optimization is proposed to resolve the checkerboard pattern. This method ensures C₀ continuity of density field in a fixed design domain, which prevents the checkerboard pattern problem from mathematical model in essence. Numerical examples are presented to support the proposed design method which can effectively eliminate the numerical instabilities, such as checkerboard and mesh-dependency in topology optimization results. The calculate speed of the proposed method is faster than the filter method. Therefore, it can be widely used in application.The mathematical model of topology optimization for compliant mechanisms is established based on the principle of mutual energy, in which, the ratio of mutual energy to strain energy of the mechanism is regarded as the objective function. The analytical expression of sensitivity based on nodal density for compliant mechanisms is deduced in detail. The design of thermal actuator is deeply researched, which is a coupling multi-physics problem. The mathematical model of thermal actuator is established based on the nodal density method. The adjoint method is applied to sensitivity analysis of design of thermal actuator. The results of representative numerical examples show that the mechanisms obtained by the nodal density method have clear topology structures which actually reflectthe structures of the mechanisms without any filtering schemes.The above theory and algorithm for topology optimization of compliant mechanisms is applied on the study of MEMS component. The microgripper used in the assembly of the electrophoresis chip is designed and manufactured. The experimental results of piezoelectric micro gripper show that displacement and clamping fore of gripper are coincident with the FEM results and linear with the control voltage.The 2D micro actuator that can be used in micro stage is designed by using topology optimization of compliant mechanisms with multi load cases. Based on the topology optimization results and restrictions of micro fabrication technology, the size of the micro actuator is finally determined. The prototype of the micro actuator is fabricated by means of micro electroforming and SU-8 photolithography techniques. The displacement of the micro actuator is measured by using the stereo vision micromanipulation systems. The experimental results show that properties of the micro actuator can be fulfilled the designing demand.It can be seen that the topology optimization of compliant mechanisms plays an important methodological role in the optimal design of MEMS component, which will be applied in wide fields.