Dynamic modelling of a 4-DOF parallel kinematic machine with revolute actuators

Recursive matrix equations for kinematics and dynamics analysis of a 4-DOF parallel manipulator with a passive constraining leg and revolute actuators are presented in this paper. The prototype of this robot is a spatial mechanism, which has two translation degrees of freedom and also two rotation degrees of freedom. The manipulator consists of a base platform, a moving platform and a system of four connecting legs, having wide application in the fields of industrial robots, simulators, parallel machine tools and any other manipulating devices in which high mobility is required. Supposing that the position and the motion of the moving platform are known, an inverse dynamics problem is solved using the principle of virtual powers. Finally, some iterative matrix relations and graphs of the torques of all actuators are analysed and determined.