Kinematic and dynamic analysis of a 3-DOF parallel mechanism

This paper presents a three Degrees of Freedom (DOFs) parallel manipulator with no rotational capacity. Planar kinematic pairs (revolute joint and prismatic joint) are exclusively employed in this parallel structure. The parallelogram joint in each kinematic chain assists to ensure the moving platform’s orientation is constant throughout the reachable workspace. Unlike the general parallel mechanisms, three identical kinematic limbs are degenerated to two kinematic limbs through merging two passive prismatic joints with same movement. Three active sliding joints are still required to drive this special parallel structure. Its mobility characteristic is firstly studied in detail and all possible singularity configurations are discussed by means of screw theory. The Lagrangian formulation is employed to compute the mathematical model of the inverse dynamic problem. The reachable workspace is obtained based on the inverse kinematic solutions. The distributions of the maximum joint force effect and maximum joint velocity effect are conducted. An example is provided to illustrate their trends under preset motion of the mobile platform.