Multi-objective Design Optimization Of Distributed Compliant Mechanism With Uniform Deformation

Compliant mechanisms are class of mechanical systems that can replace conventional hinge mechanisms by compliant members.Because of its excellent characteristics such as no assembly,no lubrication,and strong miniaturization,it has broad application prospects,and it has led to a research boom for compliant mechanisms.As an important method of structural design,structural topology optimization plays an important role in the design of compliant mechanisms.Its powerful design capability brings great power to the design and application of compliant mechanisms.However,for practical applications,the lumped compliant hinge produced by the topology design is not conducive to the precise manufacture and long-term use of the compliant mechanism.Therefore,the lumped hinge should be avoided as much as possible during the design phase.In addition,distributed compliant mechanisms tend to have a more reasonable configuration and stronger competitiveness than lumped compliant mechanisms.Therefore,it is of great significance to study the design method of distributed compliant mechanisms.This paper aims to study the function of describing the strain response of the mechanism and consider the strain response of the mechanism in the topology design stage,thus controlling the optimization direction,eliminating the centralized hinge,and then obtaining the distributed flexible mechanism.The main work of this paper includes:1.Based on the structural effective strain,the strain distribution function,global effective strain,maximum effective strain and migration maximum strain describing the strain response and its distribution are summarized.The differences between the four strain responses are compared and discussed.A new topology optimization model is established by using multi-objective optimization method.2.The numerical examples of compliant grippers and compliant inverters are solved based on the strain response model.The optimized results show that the strain distribution function can obtain a compliant mechanism with uniform strain distribution in the compliant mechanism topology design.The model considering the maximum effective strain can be used to eliminate the lumped hinge while the strain distribution of the mechanism is not uniform;the model considering the global effective strain cannot eliminate the lumped hinge,and fails to obtain the distributed compliant mechanism;the model considering the migration maximum strain can reduce the maximum effective strain and eliminate the lumped hinge to obtain a more uniform strain distribution,and a distributed compliant mechanism can be obtained;3.A compliant mechanism design model based on the geometric nonlinear finite element analysis is established.The energy interpolation method is used to deal with the problem of numerical instability caused by low-density elements.The adjoint method is used to obtain the sensitivity of the objective function,and the compliant gripper is designed based on geometric nonlinearity.The numerical examples demonstrate the necessity of nonlinear analysis and the validity of the strain distribution function.