Kinematics and Singularity Analysis of a Four-Degree-of-Freedom Serial-Parallel Hybrid Manipulator

摘要

For adapting to the complex working environments of amphibious manipulators, we proposed a serial-parallel hybrid quadruped walking manipulator. We simplified the leg mechanism of the serial-parallel hybrid manipulator as a 2UPU-UPR parallel mechanism, and then analyzed the degree of freedom (DOF) of the parallel mechanism by using the screw theory. The results show that the position of the Y direction and the pose of the Z direction are two independent variables which influence the mechanism movement. We deduced the kinematics inverse solution and the velocity Jacobian matrix of the 2UPU-UPR parallel mechanism. Based on the analysis of the Jacobian matrix, three kinds of kinematic singularities of the 2UPU-UPR parallel mechanism are identified. The results show that the 2UPU-UPR parallel mechanism doesn't have the kinematic inverse singularity, but it has three kinds of kinematic forward singularities and two kinds of combined singularities. Finally, the variation of motorial parameters of this 2UPU-UPR parallel mechanism was discussed by a calculation example.