TOWARDS HIGH DYNAMIC OPERATIONS WITH PARALLEL-SERIAL HYBRID ROBOTS

Hybrid manipulators are a combination of parallel and serial linkage connection robots which can exhibit high articulation and achieve modularity in design. This paper presents the results on the kinematic modeling and motion generation of a parallel-serial hybrid robot architecture. Parallel mechanisms are increasingly being employed as a reconfigurable subsystem alongside serial kinematic chains for high speed machining and manufacturing operations. These kinematic structures have known to have superior stiffness and dynamic properties at the expense of increased complexity in modeling and control. For a specific application of placing fixture heads along sheet metal, a hybrid parallel-serial manipulator is developed. It consists of a spherical revolute (SR) 4-degree-of-freedom (DOF) serial arm mounted on a (3-DOF) parallel manipulator with two UPR (4DOF) legs constrained to move in a common rotating plane, and an SPR (5-DOF) leg. The kinematic architecture utilizes parallel linkage as a positioning manipulator, whereas the serial arm provides the necessary dexterity and increased workspace required for the task. An approach to model such complex kinematic structures with the evaluation of workspace and motion generation is discussed. The presented approach is finally validated both in simulation and with experiments performed on the real platform.