Terrain-perception-free Quadrupedal Spinning Locomotion on Versatile Terrains: Modeling, Analysis, and Experimental Validation

TL;DR

This paper introduces a novel algorithmic approach for quadrupedal robots to perform accurate spinning on uneven terrains, minimizing drift through improved kinematic modeling and control strategies, validated by experiments on various challenging surfaces.

Contribution

The study presents a new method combining a modified spherical foot kinematics model, a CoM planner, and LQR control to enable stable, drift-minimized spinning on complex terrains.

Findings

Effective spinning motion achieved on stairs, slopes, and flat ground.

Significant reduction in position drift during spinning movements.

Validated approach improves quadruped navigation in complex environments.

Abstract

Dynamic quadrupedal locomotion over rough terrains reveals remarkable progress over the last few decades. Small-scale quadruped robots are adequately flexible and adaptable to traverse uneven terrains along sagittal direction, such as slopes and stairs. To accomplish autonomous locomotion navigation in complex environments, spinning is a fundamental yet indispensable functionality for legged robots. However, spinning behaviors of quadruped robots on uneven terrain often exhibit position drifts. Motivated by this problem, this study presents an algorithmic method to enable accurate spinning motions over uneven terrain and constrain the spinning radius of the Center of Mass (CoM) to be bounded within a small range to minimize the drift risks. A modified spherical foot kinematics representation is proposed to improve the foot kinematic model and rolling dynamics of the quadruped during locomotion. A CoM planner is proposed to generate stable spinning motion based on projected stability margins. Accurate motion tracking is accomplished with Linear Quadratic Regulator (LQR) to bound the position drift during the spinning movement. Experiments are conducted on a small-scale quadruped robot and the effectiveness of the proposed method is verified on versatile terrains including flat ground, stairs and slopes.