Abstract:Two types of 3RPS parallel mechanisms with arc prismatic pairs are proposed, its limb kinematic chain consists of prismatic pair P, a revolute pair R, and a spherical joint S. Mobility, kinematics and workspace of these two types parallel mechanisms were analyzed via screw theory. The rotational center of moving platform of first parallel mechanism was the center of arc of arc rods, and moving platform rotates around the Zaxis with respect to the other two directions was decoupled. In the second parallel mechanism, the rotational center of moving platform was an intersection point of three straight lines, which passing through each center of arc rod and the center of spherical joint, and this intersection point was changed with the posture of the moving platform. In addition, the workspace of second parallel mechanism was less than the workspace of first parallel mechanism. These two types of parallel mechanisms have simple structure, high flexibility, so it can be widely used in virtual axle machine tool, flight simulator and medical equipment fields.