Cartesian Parallel Manipulator Modeling, Control and Simulation

Parallel manipulators are robotic devices that differ from the more traditional serial robotic manipulators by their kinematic structure. Parallel manipulators are composed of multiple closed kinematic loops. Typically, these kinematic loops are formed by two or more kinematic chains that connect a moving platform to a base, where one joint in the chain is actuated and the other joints are passive. This kinematic structure allows parallel manipulators to be driven by actuators positioned on or near the base of the manipulator. In contrast, serial manipulators do not have closed kinematic loops and are usually actuated at each joint along the serial linkage. Accordingly, the actuators that are located at each joint along the serial linkage can account for a significant portion of the loading experienced by the manipulator, whereas the links of a parallel manipulator generally need not carry the load of the actuators. This allows the parallel manipulator links to be made lighter than the links of an analogous serial manipulator. The most noticeable interesting features of parallel mechanisms being: • High payload capacity. • High throughput movements (high accelerations). • High mechanical rigidity. • Low moving mass. • Simple mechanical construction. • Actuators can be located on the base. However, the most noticeable disadvantages being: • They have smaller workspaces than serial manipulators of similar size. • Singularities within working volume. • High coupling between the moving kinematic chains.