Design Optimization And Experimental Study Of Quasi-zero Stiffness Flexible Micro-grippe

With the continuous development of micro-operation technology toward high precision,precision force control based on force feedback is constrained in micro-scale applications.The quasi-zero stiffness flexible mechanism can replace the traditional complex force feedback control system by using the constant force characteristic of mechanical structure,which can get rid of the dependence on force sensors and reduce the complexity of the control system while effectively guaranteeing the operation accuracy.In addition,the quasi-zero stiffness flexible mechanism combines the characteristics of constant force mechanism and flexible mechanism,which can reduce the impact on the object while applying the control force.As a result,the study of quasi-zero stiffness compliant mechanisms have received more and more attention from researchers,but the optimal design of their structures is still at an early stage and lacks systematic discussion and research.Therefore,this thesis aims to carry out the design optimization and experimental research of quasi-zero stiffness compliant microgripper,to build an automatic structural optimization framework based on the quasi-zero stiffness compliant mechanism model,to eliminate the time-consuming parameter adjustment and complex model design in the traditional design process,to automatically optimize the structural parameters according to the specific constant force target,and to design a quasi-zero stiffness compliant microgripper capable of achieving constant force clamping on the basis of the optimized mechanism.The main research of this paper includes:(1)Establish the basic model for automatic optimization of compliant constant force mechanism.Based on the principle of superposition of positive and negative stiffness,the design of the quasi-zero stiffness compliant mechanism is carried out,and the performance of the zero-stiffness structure is analyzed by the elliptic integration method to clarify the interrelationship between the dimensions of each structure and the characteristics of the constant force mechanism.The solid model is established and parameterized in Solid Works,and the parameterized model is imported into ANSYS finite element analysis software to carry out performance analysis,and the force-displacement curve and other performance indexes of the compliant constant force mechanism are obtained,which are verified with the numerical analysis results of the theoretical model of positive and negative stiffness,and thus the basic model of the compliant constant force mechanism is obtained.(2)Model structure optimization based on multi-objective genetic algorithm.The compliant constant force mechanism has many structural parameters,and it is not practical to check the performance results and modify the model parameters manually.In this study,an automatic optimization framework is designed based on finite element analysis and Multi-Objective Genetic Algorithm(MOGA)method.The MOGA objective function between the key parameters and the target constant force is designed by conducting sensitivity analysis and screening the key structural parameters of the optimized object,and the preliminary model is automatically optimized based on the finite element analysis results.The finite element simulation and experimental results show that the optimized model can automatically achieve the expected target performance while realizing a larger constant force stroke.(3)Structural design of quasi-zero stiffness compliant microgripper.A quasi-zero stiffness compliant microgripper is designed based on the structure-optimized mechanism model,including drive module,clamping module,constant force module and adjustment module.The microgripper is capable of maintaining almost constant clamping force within a certain clamping range,offsetting the clamping force variation caused by control accuracy and external disturbance during operation,avoiding problems such as product damage or damage,and being able to adjust the constant force output size through the adjustment module.Finite element analysis and constant force clamping experiments have verified the overall rationality and correctness of the designed microgripper.