Robust Manipulation via Contact Sensing

Abstract

Humans effortlessly manipulate objects in cluttered and uncertain environments. In contrast, most robotic manipulators are limited to carefully engineered environments to circumvent the difficulty of manipulation under uncertainty. Contact sensors can provide robots with the feedback vital to addressing this limitation. This thesis proposes a framework for using feedback from contact sensors to reliably manipulate objects under uncertainty. We formalize manipulation as a partially observable Markov decision process that includes object pose uncertainty, proprioceptual error, and kinematic constraints. Our algorithms exploit the structure of contact to efficiently estimate state and plan with this model. First, we introduce the manifold particle filter as a principled method of estimating object pose and robot configuration. This algorithm avoids degeneracy by drawing samples from the lower- dimensional manifold of states induced by contact. Next, we introduce two belief space planning algorithms that seek out contact with sensors when doing so is necessary to achieve the goal. One algorithm harnesses the decoupling effect of contact to share computation between problem instances. The second leverages lower-dimensional structure to plan around kinematic constraints. Finally, we evaluate the efficacy of our approach in real-robot and simulation experiments. The results show that our state estimation and planning algorithms consistently outperform those that are not tailored to manipulation with contact sensing.