Robotic manipulation by pushing at a single point with constant velocity : modeling and techniques

University of Technology, Sydney. Faculty of Engineering and Information Technology.In many mobile robotic manipulation tasks it is desirable to interact with the robot’s surroundings without grasping the object being manipulated. Non-prehensile manipulation allows a robot to interact in situations which would otherwise be impossible due to object size or mass. This thesis investigates the most general pushing mode, that of a single contact point, formed either as a fixed point at a vertex or as a single rolling contact between two curved surfaces with a view to enable the manipulation of common household objects such as bins or coffee tables by a simple mobile robot. The investigation is limited to objects which possess a flat base and are able to slide on a flat, horizontal support surface. The derivation of a mathematical model is presented for an object pushed under these conditions, where the system accelerations influence the object motion through the dynamic effects of inertia and friction rendering the quasi-static assumption invalid. Numerical simulations explore the system behavior under a variety of configurations revealing the effect of the dynamic forces on the object motion and the existence of stable configurations, under certain conditions, where an object is pushed by a curved fence. The stable pushing behavior is confirmed experimentally. The mathematical model is utilized to generate near time-optimal pushing trajectories to manipulate an object to a desired goal location and control strategies to compensate for uncertainty in the physical parameters