Disturbance detection, identification, and recovery by gait transition in legged robots

Abstract

We present a framework for detecting, identifying, and recovering within stride from faults and other leg contact disturbances encountered by a walking hexapedal robot. Detection is achieved by means of a software contactevent sensor with no additional sensing hardware beyond the commercial actuators' standard shaft encoders. A simple finite state machine identifies disturbances as due either to an expected ground contact, a missing ground contact indicating leg fault, or an unexpected "wall" contact. Recovery proceeds as necessary by means of a recently developed topological gait transition coordinator. We demonstrate the efficacy of this system by presenting preliminary data arising from two reactive behaviors -wall avoidance and leg-break recovery. We believe that extensions of this framework will enable reactive behaviors allowing the robot to function with guarded autonomy under widely varying terrain and self-health conditions. Abstract-We present a framework for detecting, identifying, and recovering within stride from faults and other leg contact disturbances encountered by a walking hexapedal robot. Detection is achieved by means of a software contactevent sensor with no additional sensing hardware beyond the commercial actuators' standard shaft encoders. A simple finite state machine identifies disturbances as due either to an expected ground contact, a missing ground contact indicating leg fault, or an unexpected "wall" contact. Recovery proceeds as necessary by means of a recently developed topological gait transition coordinator. We demonstrate the efficacy of this system by presenting preliminary data arising from two reactive behaviors -wall avoidance and leg-break recovery. We believe that extensions of this framework will enable reactive behaviors allowing the robot to function with guarded autonomy under widely varying terrain and self-health conditions.

Limping following limb loss increases locomotor stability

“…The use of specific gaits has been suggested to be a feature enabling efficient and stable locomotion (Aoi et al, 2013;Full et al, 2002;Hildebrand, 1989;Hoyt and Taylor, 1981;Johnson et al, 2010;McGhee and Frank, 1968;Schmidt, 2014;Wilshin et al, 2017). Performance of an effective gait, however, is predicted to be strongly dependent on the number and spatial arrangement of legs available, making it particularly sensitive to autotomy.…”

Design Principles for a Family of Direct-Drive Legged Robots

“…The high sensorimotor bandwidth enjoyed by these machines greatly facilitates simple reactive strategies, affording, for example, reliable observer-free proprioceptive touchdown detection (cf. [36]). In turn, bringing such high sensing and control authority to bear upon platforms whose dynamics are so well described by simple hybrid Lagrangian mechanics [22] facilitates the application and reuse of simple, robust behavioral "modules" whose parallel [37] and sequential [38] compositions can now be extended across multiple bodies as well as flexibly recombined within a single one.…”

Autonomous legged hill and stairwell ascent

“…Instead the robot would rely on proprioceptive sensors and use the legs to "feel" obstacles. For stair climbing, we could use a "virtual contact sensor" to feel the walls and a "missing ground" sensor as a cliff detector [29]. For autonomous hill climbing, the gravitational gradient sensor could be replaced with a proprioceptive (instead of vestibular) sensor [34].…”