The Error Analysis And Compensation Of Six Degrees Of Freedom Parallel Mechanism

Parallel mechanism process the merit of great rigidity, high movement precision,good carrying capacity and lower movement inertia, so it is applied widely in manyfields of industry. The accuracy of the parallel mechanism is an important indicator ofits performance, the factors causing the pose error of the tip must be analyzed, so thatthe pose error of can be compensated and the accuracy of parallel mechanism can beimproved.A motion-control device of wind tunnel with type of6-PSS parallel mechanismwas regarded as the research object, the analysis and compensation method of poseerror were conducted, so that the requirements of experiment could be met. Thedissertation’s main work included kinematics analysis, dynamic analysis, theidentification of error parameters and the compensation of pose error.The jacobian matrix was obtained by using velocity projection method with thestructural features of6-PSS parallel mechanism considered, and the second-orderinfluence could be obtained through differential vector method, then the velocity andacceleration of components were deduced, and the dynamic model of rigid bodiessystem was established. The flexible dynamic model of the6-PSS parallel mechanismwas established with the links seen as flexible bodies.The error model of6-PSS parallel mechanism was established by using differentialvector method with all of the kinematic errors considered. The characteristics of eachmechanism error were analyzed according to the form of the transfer matrix, and theinfluence to the pose error was shown. The error sensitivity of the mechanism wasdeduced through using the theory of singular value decomposition, and itscharacteristics were analyzed.The pose error of tip about the6-PSS parallel mechanism was measured by LaserTracker, and the error identification model was established with all of the static errorsconsidered. The error identification model was solved through using least squaresmethod, and all of the errors were obtained.The static errors and dynamic errors were compensated through the application ofSoftware Compensation Act. The error of legs and gap error of hinges were seen as theerrors of position errors about hinges, and the kinematics parameters of6-PSS parallel mechanism were modified. The modified inverse kinematics model of the mechanismwas solved in order to improving the accuracy of the mechanism.The6-PSS parallel mechanism was seen as a rigid-flexible coupling system in thisdissertation, the pose error was analyzed and compensated with the static errors anddynamic errors considered, therefore, the accuracy of the mechanism was improvedgreatly. The work of this dissertation provided great guiding significance for theoryresearch and practical application of such a parallel mechanism, it also laid thefoundation for the expansion of application filed of the parallel mechanism.