Design for 3D Agility and Virtual Compliance using Proprioceptive Force Control in Dynamic Legged Robots

Abstract

For legged robots to be effective in real-world scenarios they must be capable of robustly navigating complex 3D environments using multiple modes of mobility. To achieve mobility over such a broad set of terrain topographies —- spanning structured and unstructured environments –- an ideal robot will employ both static, highly stable motions (e.g. dexterous crawling, climbing, walking), as well as highly dynamic agility maneuvers (e.g. leaping, inertial reorientation, controlled landing; running; etc.) to optimally traverse the terrain at hand. Therefore, a capable legged robot must be both dexterous, for precise footstep placement, and dynamic, for running and jumping when obstacles are insurmountable by static gaits alone. For example, extra-terrestrial landscapes or a collapsed rubble environment, ubiquitous to war and disaster zones, will contain regions of highly rugged yet relatively level ground. In these environments using high bandwidth virtual compliance, made possible by low impedance actuators, will allow the robot's legs to actively conform to the terrain producing a more efficient and swift mode of locomotion as compared to a statically stable crawling gait which requires accurate terrain mapping and explicit foot step planning. Alternatively if the terrain is both sloped and rugged it may be ideal to crawl or climb slowly using precise footholds made possible by dexterous limbs with a large workspace. Likewise, unstructured or collapsed disaster environments often contain local discontinuities (e.g. cavities, pits, ditches, curbs, obstructions, large local elevation changes relative to the robot’s leg length, etc.) in the robot's path. For these situations dynamic jumping, controlled inertial re-orientation during flight, and compliant landing would allow the robot to traverse the otherwise insurmountable obstacle and continue forward with its mission. This thesis explores the design of a new electromechanically actuated robot with legs capable of dexterous walking, running, and most significantly, explosive omni-directional jumping and actively compliant landing. A robot with such capabilities does not yet exist but is needed for legged robots to make the next leap in real-world effectiveness.