CAREER: Robust Bipedal Locomotion in Real-World Environments

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The objective of this Faculty Early Career Development (CAREER) Program grant is to develop tools for analyzing and optimizing quasi-periodic biped gaits for high-dimensional models of both humans and humanoid devices. From watching Olympic athletes to taking a hike along a dirt path, our experiences demonstrate that biped locomotion provides a highly agile and robust means of mobility. However, today's humanoid robots are far less capable than their fictional, Hollywood counterparts. The same inverted-pendulum dynamics that make upright walking highly maneuverable under desired control inputs also make it highly susceptible to destabilization. Unlike classic inverted pendulum problems (for example, a rocket propelled by thrusters at its base stabilized during continuous flight), the process of walking is complicated by the discontinuities of impulsive footsteps that vary in both width and height, resulting in a 'quasi-periodic' gait. In particular, work focuses on the challenges of walking on terrain that is not flat and includes intermittent obstacles. The approach exploits the observation that step-to-step 'snapshots' of the position and velocity states of the joints tend to lie on two-dimensional manifolds within a much higher dimensional state space for such systems. This dimensionality reduction enables the use of machine learning techniques for control policy evaluation and improvement to quantifiably estimate fall rates, energy use, and speed for a given combination of biped walker and stochastic terrain.If successful, this work will provide important tools to analyze and/or optimize a variety of real-world systems. From evaluation of the risk of falling for a stroke survivor who walks with an impaired gait, to the design of smart lower-limb prostheses for injured veterans, the modeling approach developed will provide a means of quantifying reliability for systems with such high dimensionality and complexity that traditional guarantees of stability cannot be made. Additionally, robotics research provides a natural gateway for both K-12 and university STEM education. This project includes several outreach elements to encourage this interest, from hosting on-campus field trips for local FIRST Robotics participants and predominantly Hispanic elementary school students to sponsorship of a new Robotics Club at UC Santa Barbara.