Bipedal-Walking-Dynamics Model on Granular Terrains
Xunjie Chen, Xinyan Huang, Peter Shan, Jingang Yi, Tao Liu
AI summary
Problem
Legged robots face significant instability and energy inefficiency on yielding terrains like sand due to unmodeled foot sinkage and slip, which traditional rigid-ground dynamics models fail to capture.
Approach
The authors integrate a three-degree-of-freedom foot-terrain interaction model into a bipedal dynamics framework, explicitly estimating vertical sinkage and horizontal slip to couple robot kinematics with granular resistive forces.
Key results
- Accurate prediction of joint kinematics, ground reaction forces, and foot intrusion across varying walking speeds
- Quantification of effective rolling radius and transient slip effects on granular media
- Computationally efficient estimation of the cost of transport for energy-aware gait design
- Experimental validation on a physical bipedal robot walking on a custom sand track
Why it matters
This model enables energy-efficient locomotion control and gait optimization for bipedal robots navigating unstructured, yielding environments like sand and soil.
Abstract
Bipeds have demonstrated high agility and mobil- ity in unstructured environments such as sand. The yielding of such granular media brings significant sinkage and slip of the bipedal feet, leading to uncertainty and instability of walking locomotion. We present a new dynamics-modeling approach to capture and predict bipedal-walking locomotion on granular media. A dynamic foot-terrain interaction model is integrated to compute the ground reaction force (GRF). The proposed granular dynamic model has three additional degree-of-freedom (DoF) to estimate foot sinkage and slip that are critical to capturing robot-walking kinematics and kinetics such as cost of transport (CoT). Using the new model, we analyze bipedal kinetics, CoT, and foot-terrain rolling and intrusion affects. Experiments are conducted using a biped robotic walker on sand to validate the proposed dynamic model with robot-gait profiles, media-intrusion prediction, and GRF estimations. This new dynamics model can further serve as an enabling tool for locomotion control and optimization of bipedal robots to efficiently walk on granular terrains.