Accuracy modeling, analysis and radical error distribution of 3-RPR planar parallel mechanism

Output accuracy performance is directly determined by geometric errors and working poses of a mechanism. Accuracy sensitivity as geometric error transmission coefficient, closely relates to pose configuration and geometric parameters. This research focuses on accuracy of a 3-RPR planar parallel mechanism: firstly, established 3 models in an analytic form, to describe relationship between output errors and geometric ones, then they are mutually verified statistically. Secondly, the anisotropy and periodic fluctuation of position errors, independently contributed by each category of geometric errors, are illustrated; and mirror symmetric trajectories and poses generating output errors with mirror symmetry, are also revealed by numerical simulation. Finally, the radical accuracy model in an analytic form, was established through variance and covariance analysis on output errors. We concluded that the radical error of the movable platform in central symmetric poses, follows Rayleigh distribution pattern. Through statistical comparison with Monte Carlo simulation, the radical error model was demonstrated, that provided a reference for accuracy design for other planar parallel mechanism.