Forward kinematics of 3-PPR parallel mechanism based on displacement compensation of BP neural network

Aiming at the forward kinematics of 3-PPR parallel mechanism,the results of inverse kinematics were utilized combining with Levenberg-Marquardt training method.By adopting BP neural network and improved BP neural network in succession,the nonlinear mapping from joint-variable-space to operation-variable-space of the mechanism was accomplished,and the forward kinematics was achieved.To improve the accuracy of positive solution,a displacement compensation algorithm was put forward to optimize the BP neural network.By applying this method in the mechanism with MATLAB tool,the results illustrated that the precision of positive solution was enhanced from level 10-3 to level 10-6 by iterative computations with 2.17 milliseconds,and the effectiveness as well as the correctness of proposed algorithm were proved.Thus the high accuracy and real-time controls of the 3-PPR parallel mechanism were realized.