Type Synthesis And Kinematic Analysis Of Several Spatial Coupled Mechanisms

Spatial coupled mechanism is a complex mechanism model,has been used in astronomical telescope,magic ball toys,large engineering machinery etc..Spatial coupled mechanism has a good application prospect,but at present the theoretical research of this kind of mechanisms is still in the initial stage,the methods of type synthesis and analysis of serial and parallel mechanisms can not be directly applied to this kind of mechanism.In this paper,based on the methods of serial and parallel mechanisms,two new ideas for the type synthesis of spatial coupled mechanism are proposed,and are applied to the type synthesis of the moving multi-loop coupled mechanism.And two new mechanisms are selected for kinematic analyze.The two basic principles of the transformation of parallel mechanism to multi-loop coupled mechanism with equal DoF by adding coupled branches are presented,which to avoid instantaneous mechanism.Using 3-(RRR)RR as the basic parallel mechanism,a new kind of three-DOF translational symmetric multi-loop coupled mechanism with the first and second coupled node is obtained through the application of these two basic principles.A new kind of single DoF translational spatial multi-loop coupled mechanism is synthesized using method for replacing upper mechanism's input by output of lower mechanism's.There are three coupled nodes in this kind of mechanism,and both the terminal platform and each coupled node has one translational DoF.Then a multi-loop coupled mechanism with symmetrical structure is selected out,and its forward kinematics solution and the end trajectory are analyzed.Based on MATLAB simulation of the end trajectory is carried out.The trajectory is a general curve witch different from usual single DoF parallel mechanisms.In the end of this paper,a new 2-DoF moving multi-loop coupled mechanism with symmetrical structure is designed by improving the single DoF multi-loop coupled mechanism that has been previously proposed.The forward and inverse position kinematics solutions and corresponding numerical examples are given,which verify the correctness of the solutions.The influence coefficient method is used to analyze the velocity and acceleration of the mechanism.The kinematics simulation is carried out with MATLAB.At the same time,the stiffness and flexibility of the new mechanism are analyzed,and the area with good stiffness and flexibility is determined,which provides a theoretical basis for the further optimization design of the mechanism.