Determining the Force and Moment Workspaces of Redundantly-Actuated Spatial Parallel Manipulators

Abstract

In this study, the concept of force and moment-workspaces is introduced. The force-moment capability analysis of parallel-manipulators is used to generate the force and moment workspaces. Force and moment workspaces of the manipulator are used to visualize the boundary of the workspace along with the sustainable/applicable value of force or moment depending on the maximum limits of the manipulator’s actuators. A method which analytically sets the greatest number of actuators to their maximum values is used for the determination of the force and moment workspaces. Four cases, two for finding the maximum magnitude of force with the value of moment either prescribed or associated and two for finding the maximum magnitude of moment with a prescribed or associated force, are explained and discussed. The redundantly-actuated 3-RRRS (all revolute joints actuated), six degree-of-freedom parallel manipulator is used as an example case for the analysis. The results show that a more even force/moment distribution is achieved for points lying inside the boundary of the maximum reachable workspace. It is shown that the proposed force and moment workspaces are an effective design tool for parallel manipulators. In addition, these force and moment workspaces can be seen as an efficient tool for task planning.