Kinematic Analysis And Optimization Of A 4-PRRU Redundantly Actuated Parallel Manipulator

A three-DOF parallel mechanism with two rotations and one translational DOFs(2R1T)is an important branch of parallel mechanism and have a wide range of applications.In this paper,a new type of 4-PRRU manipulator is proposed.This manipulator is a three-DOF redundantly actuated parallel manipulator.The kinematics analysis,singularity analysis,performance analysis and design of the mechanism are mainly studied.The main contents cover the following aspects:A simple model of 4-PRRU redundantly actuated parallel manipulator was established,then determined a fixed coordinate system,a moving coordinate system and given some relevant parameters.Based on the basic knowledge of screw theory,the DOF of the manipulator under the initial position and the general position are analyzed and then can be verified with the modified GK formula again.The results show that the manipulator has three degrees of freedom,a translation in the direction of z-axis,a rotation around u-axis,and a rotation around v-axis.Using the geometric relationship of the mechanism,the inverse kinematic analysis can be solved.The velocity equation and Jacobian matrix of the mechanism can be obtained by taking differentiation of the inverse kinematics equations.Using the calculation of Jacobian matrix determinant,we can find that inverse singularities exists.However,there are no forward or combined singularities.By considering the factors such as the constraint of the rod length,the corner constraint of the rotation pair,and the singularity constraint of the mechanism,the numerical search method of MATLAB is used to draw up the reachable working space of the tool on the moving platform.Through the spiral of a given tool in the workspace,the corresponding time-driven quantities of each branch are solved and imported into the Motion module in SolidWorks for animation.The simulation results show that the degrees of freedom and position analysis of the mechanism are correct.Using the force transfer performance index LTI which based on the screw theory to analyzed redundantly actuated parallel manipulator,the performance analysis of the mechanism is performed and the dimension of the mechanism rod is treated dimensionless with the LTI performance index as the objective function.The results show that the force transfer performance of the organization has been significantly improved.Choose some key parts of redundantly actuated parallel manipulators to analys in ANSYS software.The final results show that the body parts stiffness and strength all meet the project requirements.