MEAM Seminar: “Controlling Contact Transitions for Dynamic Robots”

Legged robots, robotic manipulators, and their combined embodiment as humanoid robots have received considerable attention across both academia and industry. However, with few notable exceptions, state-of-the-art demonstrations are significantly less dynamic than their biological counterparts. A considerable challenge for performing more dynamic tasks for both legged robots and robotics manipulators lies within controlling contact interactions with their environment. Legged robots are sensitive to impacts with the ground when executing dynamic motions because they undergo large changes in their velocities in a short amount of time with uncertainty in both the impact model and timing. Robotics manipulators often focus on quasistatic models or static contacts to avoid the underactuation that comes with sliding. First, we will propose a general framework for reducing sensitivity to uncertainty to the impact event, which we demonstrate on dynamic jumping and running controllers on the 3D bipedal robot, Cassie. Next, we explore a dynamic non-prehensile manipulation task that requires the consideration of the full spectrum of hybrid contact modes. We leverage recent methods in contact-implicit MPC to handle the multi-modal planning aspect of the task. We demonstrate, with careful consideration of integration between the simple model used for MPC and the low-level tracking controller, how contact-implicit MPC can be adapted to dynamic tasks. Finally, I propose small modifications to the MPC framework to add a dual-sided margin to the stick-slip boundary.