Computational design and energy-efficient optimization of overconstrained robotic limbs

Abstract

Energy efficiency is one of the key evaluating indicators for legged robots, which is also the driving factor in biological structure evolution. Lots of efforts have been made to develop legged machines with agile and energy-efficient motion like animals. By leveraging the planar four-bar or its variations, modern robotic design can reduce energy consumption with negligible leg inertia, which has been a widely adopted design pattern, but remains a limited adoption of overconstrained linkages in robotic application, even though it is a class of simplest revolute-only spatial mechanism. On the other hand, most of the existing legged robots still make significant trade-offs among various design indices, and there is an open question of which limb configuration has the best performance across energy efficiency, versatility, and mechanical robustness. This thesis builds upon the theoretical foundations, design principles, and optimization strategies of a class of novel robotic limb designs based on overconstrained linkage, towards developing advanced robotic limbs with better performance in energy efficiency. The first part of this thesis (Chapter 2) focuses on the kinematic derivation and engineering application of overconstrained robotic limbs, as well as the investigation of their spatial characteristics. The proposed prototype quadruped was capable of omni-directional locomotion and had a minimal turning radius (0.2 Body Length) using the fewest actuators. The second part (Chapter 3) develops a computational optimization framework for optimizing the energy efficiency performance of generalized robotic limb design. The framework is validated by hardware experiment using a reconfigurable quadruped prototype and empirically validated the outstanding performance of overconstrained robotic limbs in omni-directional locomotion. The third part (Chapter 4) deepens the findings in the above studies and proposes a computational framework to design 1-DoF overconstrained robotic limbs for desired spatial trajectory while achieving energy-efficient, self-collision-free motion in full-cycle rotations. The resulting hexapod robot with overconstrained robotic limbs showed state-of-the-art energy efficiency compared with other small hexapod robots in recent years. The findings of this research argue the potential for a research field in overconstrained robotics by using overconstrained linkages to formulate novel robot structures. (339 words)