Task-space tracking with redundant manipulators

A controller for redundant manipulators with a small fast manipulator mounted on a positioning part has been developed. The controller distributes the fast motion to the small fast manipulator and the slow gross motion to the positioning part. A position reference is generated on-line to the positioning part to avoid singularities and the loss of degrees of freedom. The task-space position vector is augmented by the generalized coordinates of the positioning part. Feedback linearization and decoupling are then applied in the augmented task space to obtain a model consisting of decoupled double integrators. These decoupled double integrators are controlled by the use of linear quadratic optimal control. In the optimal control problem the performance index is chosen so that the task-space position reference is tracked with a high bandwidth while the reference to the positioning part is tracked with a low bandwidth. The controller has been applied to a simple planar redundant manipulator and an eight-link spray painting robot in simulation experiments. These simulations showed that a high bandwidth was possible with moderate actuator torques.