| With the development of manufacturing and industrial innovation,higher requirements have been placed on unitized equipment,especially parallel robots.The degree of freedom is the core attribute of robots and determines the motion form of the mechanism.However,a fixed degree of freedom also imposes constraints on the mechanism and makes it unable to adapt to complex and changing environments and different application scenarios.Therefore,the redundant drive of variable degrees of freedom has become a research hotspot for the reconfigurable parallel mechanism and has received extensive attention from scholars.This paper aims to propose a parallel robot with reliable performance in multiple operating modes.In this paper,the parallel robot is studied based on Lie group theory.A six-degree-offreedom supporting chain is proposed by selecting one of the six-dimensional manifolds generated by the semi-direct product operation of the three-dimensional rotation group and the three-dimensional translation group in Lie group.Then,a reconfigurable parallel mechanism with reconfigurable motion pairs is obtained by replacing the motion pairs with the same degree of freedom with spherical five-bar motion pairs.Three redundant drives are added to obtain a redundantly reconfigurable parallel mechanism.The kinematics of this mechanism is analyzed.The degrees of freedom of the mechanism under various working modes are solved using the screw theory,and the correctness of the solution is verified.The forward and inverse kinematics of the mechanism under six degrees of freedom are analyzed,and the nine inputs are decoupled.The correctness of the solution is numerically verified.The unique positive solution is determined by adding redundant drives,and the probability of completing the target task is analyzed using a simple mathematical model.Furthermore,the performance of the mechanism is analyzed.The Jacobian matrix under redundant drive is solved,and the singularity of the mechanism is studied,concluding that the mechanism has no singularity under certain scale conditions.Seven different workspaces are obtained through analytical solutions,and the correctness of the analytical solutions is numerically verified.The factors affecting the workspace volume are analyzed and classified into three categories,and the maximum workspace volume under certain conditions is obtained.The dexterity of the mechanism is analyzed using the condition number of the Jacobian matrix.The difference between non-redundant and redundant drives is compared,and it is found that redundant drives effectively improve the dexterity of the mechanism.The dexterity of the mechanism is analyzed under redundant drive conditions based on initial height,mechanism attitude,and mechanism scale,and the changing rules and characteristics of the dexterity are summarized.Finally,this paper summarizes the research and obtains various performance indicators of the mechanism,which meet the design requirements of the redundant reconfigurable parallel mechanism. |
