Proprioception and Reaction for Walking Among Entanglements

Entanglements like vines and branches in natural settings or cords and pipes in human spaces prevent mobile robots from accessing many environments. Legged robots should be effective in these settings, and more so than wheeled or tracked platforms, but naive controllers quickly become entangled and stuck. In this paper we present a method for proprioception aimed specifically at the task of sensing entanglements of a robot's legs as well as a reaction strategy to disentangle legs during their swing phase as they advance to their next foothold. We demonstrate our proprioception and reaction strategy enables traversal of entanglements of many stiffnesses and geometries succeeding in 14 out of 16 trials in laboratory tests, as well as a natural outdoor environment.

I. Introduction

Tripping hazards like vines, branches, and outcroppings fill many natural environments from forest floors to reed beds. Without a way to navigate these entanglement-filled environments, mobile robots cannot perform important tasks like environmental monitoring, scientific sampling, or fire-fighting. In human environments, robots may need to navigate around cords, hoses, and protrusions to perform tasks like inspection, delivery, or in-home assistance. In this work, we develop proprioceptive detection of entanglements on a quadruped robot's swing legs and simple control strategies to disentangle from them, enabling the robot to walk through numerous, distributed contacts of any stiffness.