A Structure Error Compensation Method for the Parallel Mechanisms

The structure error, which is not belonged to the kinematical parameters´ error, is studied in this paper. According to the characters of the parallel mechanism, a compensation method for structure error is presented. This method can compensate the errors caused by kinematical parameter errors and non-kinematical parameter errors, which are both parts of the structure errors. This method is applied to the iterative compensation for the structure errors caused by the branch chains with prismatic joints in parallel mechanisms. The compensation mathematic model is derived. The structure errors decreased obviously by once iteration of the forward kinematics, and to the higher order by twice. We take this method to simulate the error compensation of a parallel orientation mechanism with 2-degree of freedom (DOF). The simulation result shows that the structure error is reduced to one in hundreds after compensation.