The motion of a pushed, sliding object : part 2 : contact friction

The physics of motion of a sliding object can be used to plan sensorless robot manipulation strategies based on sliding. Prediction of a sliding object's motion is difficult because the object's distribution of support on the surface, and the resulting frictional forces, are in general unknown. We describe a new approach to the analysis of sliding motion, which finds the set of object motions for all distributions of support. The analysis includes contact friction between the pusher and pushed object, as well as sliding friction between the pushed object and the surface it slides on. To demonstrate the use of our results, we find the distance a polygonal object must be pushed by a fence to assure alignment of an edge of the object with the fence. We also analyze the motion of a sliding disk as it is pushed aside by the corner of an object in linear motion. Finally, we consider a sensorless manipulation strategy based on "herding" a sliding disk toward a central goal by moving a robot finger in a decreasing spiral about the goal. The optimal spiral is constructed, and its performance discussed.