Accuracy Analysis And Synthesis Of 3-(?)RS Parallel Mechanism

Accuracy is one of the great important performance index for the parallelmechanism, however, which has not been completely resolved so far. Supported bythe NKPSTSP (Grant No. 2006BAF01B00), Studies on kinematic analysis, errormodeling, accuracy analysis and synthesis of the 3-PRS parallel mechanism werecarried out in this thesis, which provided important theoretical instructions for thedevelopment of the novel head for the aircraft manufacturing. The work issummarized as follows:The forward and inverse position models of the 3-PRS parallel mechanism areestablished using the closed-loop vectors method. Analysis of the forwardposition is carried out by using both analytical and numerical methods. Then thevelocity mapping is deduced. Its full Jacobian matrix is formulated by means ofthe constraints. This lays the foundation for identification of the geometricsource errors concerned with uncompensable position and pose error of thesystem.The error model of the 3-PRS parallel mechanism is formulated based on theperturbation theory. Then actuation and constraint Jacobian matrix is employedto identify the geometric source errors relative to compensable anduncompensable position and pose errors respectively.An index has been proposed for evaluating the contribution of the relatedgeometric source errors to the uncompensable errors of the system. By use of theMonte Corlo method to simulate the geometric source errors, sensitivity analysisis carried out. And the configurations in which the uncompensable errors of thesystem take the maximum value have been found.On the pursuit of the minimum manufacturing cost, the accuracy synthesis hasbeen carried out to guide to design the tolerance of manufacturing and assemblyof the parts with the help of the Genetic Algorithms, where, the permitted valueof the maximum errors of the system is taken as constraint conditions.