Analysis of Kinematic Characteristics of 2-P(RPS + UPS) Parallel Mechanism with Six Degrees of Freedom

At present, there is an increasing demand for the workspace required for the assembly of components, and a parallel mechanism with a large workspace is urgently needed to make up for it. Therefore, in this paper, a 2-P(RPS + UPS) parallel mechanism (where S, P, R, and U represent spherical, prismatic, revolute, and universal joints) with four branched chains and six degrees of freedom is proposed and its kinematic characteristics are analyzed. First, the speed of the 2-P(RPS + UPS) parallel mechanism is numerically derived and verified by simulation using ADAMS software. Then, the motion decoupling characteristics of the mechanism are analyzed from the expression of the speed and position relationship between the input and output of the mechanism. To minimize the force on each branch in the workspace, scale optimization of the 2-P(RPS + UPS) mechanism and the Stewart mechanism is performed. Further, analysis of the dexterity, singularity, and workspace of the 2-P(RPS + UPS) mechanism is conducted, and the performance of the mechanism is compared with that of the Stewart mechanism. The proposed parallel mechanism has fewer branches, a simple kinematic model, strong motion decoupling, a high bearing capacity, a large workspace, and a low initial position height. Moreover, it can be conveniently transported and stored. Therefore, it has good application prospects in assembly and posture adjustment scenes requiring large workspaces.