Research On The 3-PRR Compliant Micro-positioning Stage Based On The Compliant Linear Mechanism

In recent years,with more and more wide applications of flexible precision positioning platform in bioengineering,advanced manufacturing and other fields,the requirements of the system and equipment for precision positioning technology become exigent.The flexible linear mechanism is a key part of the flexible precise positioning platform,and its performance directly affects positioning accuracy of the platform.The method of structural representation of flexible mechanisms and the synthesis method of flexible linear mechanisms are proposed in this paper.The displacement of the flexible linear mechanism and the stiffness and the off-axis stiffness ratio of the typical flexible linear mechanism have been analyzed.The 3-PRR micro platform based on flexible linear mechanism has been studied theoretically and experimentally evaluated on the constructed prototype.The main contents of this dissertation are as follows:(1)The structural representation of flexible mechanisms and the configuration synthesis of flexible linear mechanisms have been studied.Based on the analysis of the basic composition of the flexible mechanism and the criterion of the structural model of the flexible mechanism,a method of a topological graph and the adjacency matrix for the flexible mechanisms is proposed.The definition and calculating formula of the degree of freedom are introduced.A flexible mechanism synthesis method for regenerative flexible kinematic chains is proposed based on the method of Freedom and Constraint Topologies(FACT).The core of the method is to establish the constraint mapping relationship among the geometric module,constraint module,and physical module based on the screw theory.Then,the integrated flexible kinematic chain is used to realize the effective extension of the shape synthesis.According to the flexible linear mechanism,28 representative flexible linear mechanisms are synthesized under 6 regenerative paths,of which 5 are newly proposed.(2)For the typical flexible linear mechanism,a displacement calculation method considering axial drift has been proposed.The simplified analysis model of the branch stiffness of the combined flexure hinge mechanism and the displacement analysis method considering the axial drift are proposed.The location of characteristic points of the Roberts flexible mechanism is determined,and the displacement calculation model based on axial drift is established.The buckling displacement of the Roberts compliant linear mechanism is studied and verified by finite element method.This method is more accurate than the pseudo rigid body calculation method.The soft spring combination type Roberts flexible hinge mechanism's displacement is analyzed and verified by finite element method and experimental prototype test.It proves that the performance of the linear displacement mechanism is superior when the mechanism is applied to the large stroke micro platform.(3)The stiffness and off-axis stiffness ratio of flexible linear mechanisms have been studied.The input and output characteristics of the flexible four bar mechanism are compared.The influence of the profile of the flexible hinge and the shape of the flexible moving pair on the output displacement of the symmetrical four bar linkage are discussed.A high-efficient and low-coupling flexible symmetrical four bar linkage with variable cross sections is proposed.The flexibility matrix is obtained and the influence of structural parameters on its size is studied.A lever displacement reduction flexible linear mechanism and a stiffness difference displacement reduction flexible linear mechanism are designed,analyzed,and evaluated by finite element method.The concept and the analysis principle of off-axis stiffness ratio of flexible linear mechanism are put forward.The off-axis stiffness ratio of typical flexible linear mechanism is analyzed and compared.(4)The movement,optimization and coupling of the 3-PRR flexible micro platform are studied,and the lever type micro platform has been developed.The positive and negative solutions of the 3-PRR mechanism are derived by using the pseudo rigid body model.The motion model of the 3-PRR flexible micro platform is deduced by using the second theorem and the optimum design is carried out.The input coupling method of the micro platform is proposed,and the influence of the related parameters on the input coupling of the micro platform is studied.A 3-PRR flexible micro platform is designed based on the principle of the lever mechanism,and the symmetrical Roberts parallel flexure hinge mechanism is used as a moving pair in the micro platform.The stiffness matrix of the whole body is built by the functional transformation principle.A prototype platform has been fabricated and the pose tests have been carried out.The experimental data are basically consistent with the theoretical data,and the correctness of the theoretical analyses is successfully verified.(5)A high precision 3-PRR flexible micro platform based on the V type reed is studied.A high precision 3-PRR flexible platform based on the V folding reed is proposed,and its stiffness matrix is derived.The platform could realize millimeter input and micro scale output.The larger displacement reduces the proportion,which was helpful to reduce the displacement output error and improve the platform accuracy.A prototype platform has been fabricated and the pose tests have been carried out.The experimental results show that the platform has very high displacement accuracy,and the data are basically consistent with the theoretical calculation results.The correctness of the theory has been successfully verified.As a fine-tuning device,the flexible micro platform is applied to the micro milling machine 3A-S100,and the positioning accuracy could reach 0.05 ?m.In conclusion,the research involves not only the structure of flexible mechanism and flexible mechanism configuration synthesis,the displacement and stiffness modeling,and the analysis method,but also the specific design and study of several kinds of 3-PRR flexible micro platforms.This work will provide a strong theoretical and technical support for the application of 3-PRR flexible micro platform based on flexible linear mechanism in the fields of precision engineering,medical,biological engineering,industrial automation,etc.