A New Design of Redundant 7-DOF Parallel Robot with Large Workspace

In recent years, the demand for the dexterous machine systems is increasing and various robot mechanisms have been developed. Above all, parallel robots have been taken attention because they have some advantages in the motion performance like high precision and high stiffness. However, the application is limited because the workspace is small and the kinematic characteristics including singularities is complex. Further consideration to overcome such problems at the view of the mechanism will lead to further application of parallel robots. In this study, we propose a new design of 7-DOF parallel robot with large workspace and high dynamic capability. The enlargement of the workspace is realized by the asymmetric architecture and additional joint at the base leading to the kinematic redundancy. The mechanism leads to a simple solution of the forward kinematics and the inverse kinematics available in the control cycle. The kinematic analysis leads to the simple control strategy to perform precise position control. Moreover, robust control is achieved utilizing the acceleration control method based on the disturbance observer. The experiments were conducted with the prototype and the results show that simple and robust position control is realized. This study gives insights to the mechanism of parallel robots and leads to the further application of them.