Kinematics Analysis of 3UPU_UP Coupling Parallel Platform in the Marine Environment

A study of the kinematic characteristics of a 3UPU_UP coupling parallel platform that has three-degree-of-freedom(3-DOF). In this article, a novel 3UPU_UP parallel platform is presented, which is based on the 5-DOF 3UPU parallel platform by adding a UP followed limb. The DOFs and motion constraints of the platform are analyzed by the screw theory, and the coupling constraint equation of the platform is obtained through coordinate transformation. The inverse kinematics equation of the platform is derived by the closed-loop method, and the forward kinematics equation of the platform is solved by Netwon-Rapson iteration. The trajectory of the platform in space is obtained and the correctness of the coupling constraint equation of the platform in other DOFs is verified. Considering that the motion of a ship on the sea is multi-DOF and complicated, the motion of the cargo on the ship can be compensated by using a coupling characteristic of the platform to improve the safety of marine operations.