Beschreibung
This paper presents a hybrid position and force control approach for the cooperative transport of an object by an arbitrary number of mobile manipulators. In this approach, the mobile base is controlled by a position-based formation controller and the manipulator by a force-based controller. We use a simple tracking controller to control the position of the mobile platforms. The end effector position is controlled by a cartesian impedance controller while controlling the orientation force-free. By splitting the control problem, we can eliminate the feedback of the object handling into the formation control and thus simplify the formation control significantly. Also, the orientation limitations and control errors of the nonholonomic mobile platforms can be compensated for by the manipulator's compliance, without the need for elaborate whole-body modeling and identification. As proof of concept, we demonstrate the usefulness of our approach using a transport process with two mobile manipulators in an industrial environment.