Towards an Online Framework for Changing-Contact Robot Manipulation Tasks

We describe a framework for changing-contact robot manipulation tasks, which require the robot to make and break contacts with objects and surfaces. The discontinuous interaction dynamics of such tasks make it difficult to construct and use a single dynamics model or control strategy for such tasks. For any target motion trajectory, our framework incrementally improves its prediction of when contacts will occur. This prediction and a model relating approach velocity to impact force modify the velocity profile of the motion sequence such that it is C∞ smooth, and help achieve a desired force on impact. We implement this framework by building on our hybrid force-motion variable impedance controller for continuous-contact tasks. We evaluate our framework in the illustrative context of a robot manipulator performing sliding tasks involving multiple contact changes with surfaces of different properties.