An interactive approach to determining complex contact states

The information of topological contact states is needed for a wide range of tasks, especially high-precision robotic assembly tasks, where contact states are inevitable. Often an assembly motion plan involves a sequence of contact state transitions between the part held by a robot and another part to form the assembly or subassembly. Except for the simplest cases, obtaining the information of all possible geometrically valid contact states is far from trivial. There is considerable research on how to obtain all valid contact states and their adjacency graph automatically between polyhedral objects, given certain seed contact states (J. Xiao and X. Ji, 2001). More recently, how to obtain such information between general curved objects is also considered (P. Tang and J. Xiao, 2005). However, one open problem is how to obtain the seed contact states in the first place, which are preferred to be locally most constrained contact states involving multiple contact regions. This is especially challenging between general curved objects with boundaries of high-order algebraic surfaces. In this paper, we describe how a fast interactive approach based on accurate real-time distance computation and taking advantage of haptic rendering is particularly suitable for determining complex contact states between general curved objects accurately, which can be used as a handy and accurate tool to find seed contact states for subsequent automatic generation of other possible contact states. We demonstrate the effectiveness of this tool with implemented examples