Structural Design And Parameters Optimization Of A Two-Dimensional Translational Parallel Micro-Positioning Platform

Since fully compliant joints taking the place of traditional kinematic pairs, the fully compliant parallel micro-displacement mechanism that has characteristics of free of friction, no clearance, fast response, compact structure, small error accumulation was received much attention and application, the design and analysis methods of which existed a certain difference between macro-moving parallel mechanisms. In terms of structural design and performance analysis of parallel micro-displacement mechanism, this paper carried out a detailed and in-depth study to a new kind of two-dimension translational parallel micro-positioning platform on the points of compliance calculation of flexible kinematic pairs, kinematics and static analysis of overall mechanism, error analysis and structural parameters optimization. The contents are as follows:Firstly, degree-of-freedom and motion output analysis of micro-positioning platform were analyzed, position equation, speed positive/negative solution equation were established using the methods of pseudo-rigid-body model and differential movement system analysis, shape of workspace was given, relationship between workspace area and structural parameters was analyzed.Secondly, compliance calculation formula of flexible parallel plate prismatic pair in its work plane was built up by taking advantage of the Second Castiglianos Theorem, variations of flexibility coefficient in all directions corresponding to structural parameters of prismatic pair were analyzed; finite element model of flexible parallel plate prismatic pair was established with software of ANSYS, and made comparation with traditional compliance calculation formula, all these verified that the derived calculation formula had a relatively high accuracy. On this basis, flexibility matrix and static stiffness matrix of the micro-positioning platform' overall mechanism was worked out respectively according to energy principle and virtual work principle, mapping relationship between the two Jacobian matrixes was derived.Thirdly, error analysis model of the micro-positioning platform was established from the two aspects of theoretical model error that based on the kinematic analysis and machining error that based on stiffness matrix, influence of various structural parameters on the accuracy of micro-positioning platform was analyzed comprehensively, main factors that influenced the positioning accuracy were verified.Finally, the smallest stiffness and the highest positioning accuracy of the overall mechanism were optimization objectives, multi-objective optimization mathematical model was built up, mathematical model was solved using the genetic algorithm, and optimal structural size that met the objective function was obtained.Through above analysis and study, design plan of two-dimension translational parallel micro-positioning platform was verified, which provided theoretical foundation to kinematics/ statics, accuracy analysis, and follow-up study such as dynamics research and control system design.