Development Of Motion Simulation And Accuracy Prediction System Of Parallel Platform With Six Degrees Of Freedom

Parallel platform with six degrees of freedom has a series of advantages, suchas good stiffness, load distribution, high control accuracy, strong bearing capacity,steady motion, so it is widely used in the situation which requires high precision,large load and small workspace. However, the structure of the parallel platform iscomplexity with many assembly parts, and the high assembly accuracy is requiredwhich leads its assembly process is difficult, on the other hand, there are irreversibleassembly problems. At present, manual-based practices are mainly used for theassembly of complex products such as parallel platform in domestic enterprises,which bring about series problems such as uncertain accuracy, longer assemblycycle, and higher costs, etc.Research on the prediction of motion accuracy of parallel platform with sixdegrees of freedom is proposed in this thesis which predicts the motion accuracybefore parallel platform assembly or during the assembly process. Final motionaccuracy of parallel platform is predicted by the given original error, and theassembly quality is evaluated by the predicted results, the evaluation result is used tosee whether assembly quality meet the use and design requirements, then originalerrors reference which meets the design requirements is designed to instruct theworkers’ assemble operation, which can reduce the number of assembly adjustment,and also provide reference for some irreversible assembly problems.Firstly, the movement principle of parallel platform was analyzed in this thesis.A three-dimensional simplified geometric model of parallel platform was built, andthe geometric motion simulation was done by file of STL format and timer principle.In order to predict the error of current pose state in parallel platform movementprocess, the motion simulation of parallel platform geometric model is necessary toachieve predicting accuracy of the end moving platform in any pose state within itswork space.Secondly, the factors were summarized which influence moving platform poseerror. A coordinate system was created according to spatial distribution of thesefactors, and a spatial geometric model was simplified from the complex parallelplatform. Then the various original errors were determined in the stationary andmoving established coordinate system, the solving equation of moving platformpose error was deduced by coordinate transformation and differential geometrycalculation, which was the error solution model of parallel platform, the accuracyanalysis was completed with the equation. On the base of accuracy analysis,accuracy design was done for the factors which influence the parallel platform errors, then a series of original tolerance design values of the factors which influence errorwere given by orthogonal design method.Finally, motion simulation and accuracy prediction system of parallel platformwith six degrees of freedom was developed and applied in the project, then theaccuracy analysis and design of parallel platform were achieved.