Optimization-free Ground Contact Force Constraint Satisfaction in Quadrupedal Locomotion

TL;DR

This paper introduces an optimization-free control framework for quadrupedal robots that enforces ground contact constraints efficiently using an Explicit Reference Governor and Lyapunov stability, bypassing heavy optimization algorithms.

Contribution

The work presents a novel control approach combining a supervisory controller with an ERG to enforce ground contact constraints without optimization, suitable for less powerful onboard computers.

Findings

The ERG effectively enforces ground contact constraints.

The approach reduces computational load compared to traditional optimization methods.

Preliminary results demonstrate feasibility on the Husky Carbon robot.

Abstract

We are seeking control design paradigms for legged systems that allow bypassing costly algorithms that depend on heavy on-board computers widely used in these systems and yet being able to match what they can do by using less expensive optimization-free frameworks. In this work, we present our preliminary results in modeling and control design of a quadrupedal robot called \textit{Husky Carbon}, which under development at Northeastern University (NU) in Boston. In our approach, we utilized a supervisory controller and an Explicit Reference Governor (ERG) to enforce ground reaction force constraints. These constraints are usually enforced using costly optimizations. However, in this work, the ERG manipulates the state references applied to the supervisory controller to enforce the ground contact constraints through an updated law based on Lyapunov stability arguments. As a result, the approach is much faster to compute than the widely used optimization-based methods.