| The parallel mechanism has become a research hotspot in recent years because of its advantages such as high precision and high rigidity.Less DOF parallel mechanism were more concerned.Redundantly driven parallel mechanism has become a new research hotspot because it can eliminate or reduce the shortcomings of the traditional parallel mechanism,such as singularity and small working space.Beside,redundantly driven parallel mechanism also have the advantage of increasing the stiffness,optimizing the load among the drives,eliminating the hinge clearance and improving the motion accuracy.Based on a major national wind tunnel project,kinematics,dynamic,error,static and dynamic characteristic are studied.It lays a theoretical foundation for research of this type in the future.In this paper,inverse kinematic of 4-PRR mechanism is analyzed by analytical method,and proves its correctness by comparing the simulation result of MATLAB and ADAMS.The kinematics positive solution is analyzed by the Newton iteration method.Six sets of attitudes date are selected to verify the correctness of the kinematics positive solution.The first-order influence coefficient method is used to solve the speed Jacobian matrix of 3-PRR and 4-PRR mechanism.In order to analyzes the mechanism dynamic,the model is reasonable simplified.Dynamic model of 3-PRR parallel mechanism is established by using the Lagrange method.Dynamic simulation of the mechanism is solved by MATLAB and ADAMS,and proves its correctness by comparing the result of two method.Dynamic model of 4-PRR parallel mechanism is established,the driving force of the redundant mechanism was optimized by the pseudo-inverse method.It was proved that the redundant branches could improve the mechanical performance of the mechanism by comparing the driving force of 3-PRR mechanism and 4-PRR mechanism.In order to calculate the kinematic accuracy of the mechanism,error transfer matrix is deduced.Based on the error matrix,the influence of comprehensive error on the posture of the parallel mechanism is analyzed.Single error is analyzed to find out the important factors.Perform rigid-flexible coupling simulation is performed by ADAMS software to analysis the effect of elastic deformation of rod on mechanism error.Static and dynamic characteristics of the 3-PRR mechanical and 4-PRR mechanism is analysis by workbench,it is proved that the redundant branches could greatly improve the stiffness of the parallel mechanism. |
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