Planning Robotic Manipulation Strategies for Workpieces that Slide

We consider the automated planning of manipulation strategies for workpieces able to slide on their work surface. We wish to generate open-loop (i.e. sensorless) strategies which succeed in aligning or grasping a workpiece, in the face of two kinds of uncertainty: 1) the initial configuration of the workpiece may nave some bounded error, 2) the details of the contact between workpiece and work surface may be unknown, precluding deterministic solution for the motion of the workpiece even were its initial configuration exactly known. Configuration maps are defined, which map all configurations of a workpiece before an elementary manipulative operation to all possible outcomes. The configuration map for an operation sequence is a product of configuration maps of the elementary operations which compose the sequence. We find the elementary configuration maps which describe the interaction of a polygonal workpiece with a moving fence or robot finger. Using elementary manipulative operations (represented by configuration maps) as primitives, appropriate search techniques are applied to find operations sequences which are guaranteed to succeed despite uncertainty. Such operation sequences may be used as parts-feeder designs or as simple manipulation or grasping strategies for robots. As a concrete example we demonstrate the automated design of a class of passive parts-feeder consisting of multiple sequential fences across a conveyor belt.