Straight-Leg Walking Through Underconstrained Whole-Body Control

TL;DR

This paper introduces a novel whole-body control method enabling bipedal robots to walk naturally with straight legs and toe-off, simplifying height planning and improving gait efficiency.

Contribution

It proposes an underconstrained control approach that allows real-time straight-leg gait generation with toe-off, demonstrated on the Atlas humanoid.

Findings

Successful walking over varied terrain in experiments and simulations

Legs remain straight throughout the gait cycle

Enhanced kinematic reachability via toe-off motion

Abstract

We present an approach for achieving a natural, efficient gait on bipedal robots using straightened legs and toe-off. Our algorithm avoids complex height planning by allowing a whole-body controller to determine the straightest possible leg configuration at run-time. The controller solutions are biased towards a straight leg configuration by projecting leg joint angle objectives into the null-space of the other quadratic program motion objectives. To allow the legs to remain straight throughout the gait, toe-off was utilized to increase the kinematic reachability of the legs. The toe-off motion is achieved through underconstraining the foot position, allowing it to emerge naturally. We applied this approach of under-specifying the motion objectives to the Atlas humanoid, allowing it to walk over a variety of terrain. We present both experimental and simulation results and discuss performance limitations and potential improvements.