Simultaneous trajectory tracking and stiffness control of cable driven parallel manipulator
Cable actuated parallel manipulators, also called cable robots, share many features in common with traditional parallel manipulators. However, such systems additionally feature considerably large workspace, large payload handling capacity and good disturbance rejection potentials over traditional parallel manipulator by virtue of the cable-band actuation. However, realizing their benefits poses numerous challenges to researchers. One critical issue is the unidirectional nature of forces exerted by cables, which only allows them to endure tensile force when performing tasks. Another critical issue in such systems is the actuation redundancy. In this thesis, we will examine these two aspects in the context of motion and active stiffness control scenarios. First, we study the implication of actuation redundancy in the context of controller design and workspace (task space) stiffness property of cable robot system. Then suitable trajectory tracking control schemes are developed to achieve two different secondary goals under positive control input constraint: (a) minimal energy consumption among actuations; (b) active stiffness control to improve disturbance-rejection. Finally, these control schemes are evaluated within a virtual prototyping (VP) implementation framework.