Leg Mechanics for Dynamic Locomotion

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This research moves towards walking and running robots that will meet and exceed the agility, efficiency, and robustness of human walking and running. Specifically, the research will address fundamental principles behind the physical design of legs, including describing configurations of joints, springs, and other components to best enable legged locomotion. This work falls within a broad, interdisciplinary effort to understand leg function and dynamics, and will have utility and impact among the robotics, dynamics, and biomechanics communities. The foundational design guidelines initiated here will enable robots that can go anywhere that animals and humans go, and many places they cannot, such as nuclear power plant disaster areas and burning buildings. The same foundation will enable prosthetic limbs and exoskeletons that match the natural dynamics of a human leg, while running all day on a single battery charge. This research will enhance understanding of the interaction between the design of a legged system and its dynamics during touchdown, stance, and swing, focusing on three key aspects of the design: First, the inertia distribution in the leg, with an emphasis on how mass placement, number of links, and "redundant" elements of leg kinematics (such as pointing the knee "up" or "down") contribute to the impact felt by the system at touchdown and the dynamics during swing phase. Second, the motor coupling to the linkages, focusing on how different mappings between actuation and mechanism degrees of freedom can lead to the motors either sharing loads or fighting against each other. Third, spring function and placement, including desirable nonlinearities for mitigation of impacts and swing-phase ringing, alignment of principle stiffness axes with mechanism degrees of freedom, and transmissions that allow for configuration-dependent elasticity. The research approach draws on examples from biology and previously constructed robots, utilizes mathematical tools from applied mechanics, and builds on prior work with experimental walking and running robots.