Optimization for Control and Planning of Multi-contact Dynamic Motion

Whether a robot is assisting a stroke victim to move about his or her home, or packing shipping containers in a warehouse, the fundamental promise of robotics centers on the ability to productively interact with a complex and changing environment in a safe and controlled fashion. However, current robots are largely limited to basic tasks in structured environments–operating slowly and cautiously, afraid of any incidental contact with the outside world. Dynamic interaction, encompassing both legged locomotion and manipulation, poses significant challenges to traditional control and planning techniques. Discontinuities resulting from impact events and dry friction make standard tools especially poorly suited in scenarios with complex or uncertain contacts between the robot and the environment. In this talk, I will discuss approaches that leverage the interplay between numerical optimization and the mathematical structure of contact dynamics to avoid the combinatorial complexity of mode enumeration. In particular, a tractable algorithm for trajectory optimization without an a priori encoding of the contact sequence is presented. The talk will also present novel algorithms utilizing sums-of-squares programming, a form of convex optimization, that provide concrete, formal analysis of the stability of systems making and breaking contact.
Michael Posa is a Ph.D. candidate in Electrical Engineering and Computer Science at the Massachusetts Institute of Technology, where he is a member of the Robot Locomotion Group working with Professor Russ Tedrake. He received his B.S. and M.S. in Mechanical Engineering from Stanford University in 2007 and 2008, where he received the Frederick E. Terman Award. Before joining MIT, he worked as an engineer at Vecna Robotics in Cambridge, Massachusetts, designing control systems and simulation tools for the humanoid BEAR robot and other devices. His research emphasizes computational approaches for control and planning of robotic systems with frictional contact. He is a recipient of the Rolf Locher Graduate Fellowship and received the Best Paper award at HSCC in 2013.