Theoretical Study On The Mechanism Of Closed Loop Dual Drive Parallel Position Adjustment And Vibration Isolation Platform

Facing the demand of stable working environment for precision payload,the concept of closed-loop dual-drive redundant Dof parallel mechanism used as position adjustment and vibration isolation platform is proposed,using the redundant Dof of mechanism to achieve separate compensation for position adjustment and vibration isolation,synchronization hybrid output motion of position adjustment and vibration isolation is achieved by the transmission of the parallel mechanism.A local closed-loop is used as the drive unit of one leg to improve the driving performance.Firstly,a new kind of configuration applied for position adjustment and vibration isolation platform is synthesized,and the basic theory of kinematics and dynamics of the new mechanism is studied.The main research contents are as follows:Driving characteristics of the same hybrid motion by different driving modes are analyzed.Based on planar closed-loop mechanism,dual input and multi input drive unit are synthesized,so the serial kinematic chain with multi drive unit that have different type of constraints are constructed;Further,redundant Dof parallel mechanism with closed loop multi-input drive unit used for position adjustment and vibration isolation are synthesized,by using the screw theory type synthesis method;The instantaneous property of Dof and reasonable input selection of mechanism are analyzed.The judgment of mechanism type having sub closed loop is conducted,a distinguishing method is given;Proposing the concept of sub generalized coordinates,the motion of the closed-loop output link is represented as generalized screw form about sub generalized coordinate,based on screw algebra method of rigid body kinematics,the kinematics modeling method of redundant Dof and non redundant Dof parallel mechanism with sub closed loop is studied,and the influence coefficient of each component for generalized coordinates of mechanism is deduced.Solve the kinematics modeling problem of this kind of mechanism,and unify the modeling process to the kinematics modeling theory on the basis of screw algebra.The Newton-Euler formula of a single rigid body,represented by 6-dimensional screw form,under object coordinate system and space coordinate system are deduced.Based on the principle of virtual power and the screw expression of Newton-Euler formula,meanwhile combining the kinematics model of parallel mechanism that containing sub closed loop which expressed in sub generalized coordinates and generalized screw,the general dynamics formula of this kind parallel mechanism are established separately in joint space and operational space.Taking 6-(PRRPR)US and 5-UPS/(RPRRR)RS two mechanisms with sub closed-loop as numerical example,applying the theoretical method in detail,the correctness of the theoretical model is verified by simulation.To evaluate the closed-loop dual drive redundant Dof mechanism,multi index are defined;Taking 3-(RRPRP)-(4S)three translational parallel mechanism as an example,aiming at single performance,the single objective optimization for one parameter and multi parameters are conducted respectively;Considering each performance index of mechanism,presents multi-objective optimization for position adjustment drive,vibration isolation drive and hybrid drive,and get the pareto-optimal set of structure parameters for each driving situation.According to the hybrid motion property of position adjustment and vibration isolation platform,study the compensation drive solving method of redundant Dof mechanism;Taking 6-(PRRPR)US mechanism as an example,Based on local closed loop motion law,the successive approximation method is designed to solve the problem of local positive solution of the closed loop drive unit while inverse solution of mechanism.According to the situation of position adjustment and vibration isolation,develop drive distribution strategies;For the application of vehicle equipment stability and satellite observation camera precise pointing,virtual prototype simulation is conducted based on dual drive solving method and distribution strategies,the ability of the closed loop dual drive position adjustment and vibration isolation platform is verified,and examine the correctness of the designed driving algorithm and distribution method.Finally,the manufacturing of physical prototype is conducted,and various forms of motion experiments are carried out to verify the output capability of the hybrid motion and the theoretical solution.Through research of closed loop dual-drive redundant Dof parallel position adjustment and vibration isolation platform,the essential characteristic of kinematics and dynamics of such mechanisms has been cleared about;The detailed method of proper working for dualinput are given,proves the feasibility of the method that applying on position adjustment and vibration isolation;Meanwhile,the research and analysis of the mechanism in the process of optimization and simulation,can be used as a reference approach for analysis of similar mechanism.