Dynamic Stability of Passive Bipedal Walking on Rough Terrain： A Preliminary Simulation Study

• Published in: Journal of bionics engineering Vol. 9; no. 4; pp. 423 - 433
• Main Authors: Afshar, Parsa Nassiri, Ren, Lei
• Format: Journal Article
• Language: English
• Published: Singapore Elsevier Ltd 01.12.2012; Springer Singapore
• Subjects: Artificial Intelligence; Biochemical Engineering; Bioinformatics; Biomaterials; Biomedical Engineering and Bioengineering; Biomedical Engineering/Biotechnology; bipedal walking; Computer simulation; dynamic stability; Engineering; Floquet乘子; human locomotion; Passive dynamics; Rough terrain; Roughness; Stability; Strikes; Surface roughness; Walking; 动态稳定性; 双足步行; 模型模拟; 行走稳定性; 表面粗糙度; 路面; 轨道稳定性; bipedal walking; rough terrain; dynamic stability; human locomotion
• ISSN: 1672-6529; 2543-2141
• DOI: 10.1016/S1672-6529(11)60139-X

A simplified 2D passive dynamic model was simulated to walk down on a rough slope surface defined by deterministic profiles to investigate how the walking stability changes with increasing surface roughness. Our results show that the passive walker can walk on rough surfaces subject to surface roughness up to approximately 0.1% of its leg length. This indicates that bipedal walkers based on passive dynamics may possess some intrinsic stability to adapt to rough terrains although the maxi- mum roughness they can tolerate is small. Orbital stability method was used to quantify the walking stability before the walker started to fall over, It was found that the average maximum Floquet multiplier increases with surface roughness in a non-linear form. Although the passive walker remained orbitally stable for all the simulation cases, the results suggest that the possibility of the bipedal model moving away from its limit cycle increases with the surface roughness if subjected to additional perturbations. The number of consecutive steps before falling was used to measure the walking stability after the passive walker started to fall over. The results show that the number of steps before falling decreases exponentially with the increase in surface roughness. When the roughness magnitude approached to 0.73% of the walker＇s leg length, it fell down to the ground as soon as it entered into the uneven terrain. It was also found that shifting the phase angle of the surface profile has apparent affect on the system stability. This is probably because point contact was used to simulate the heel strikes and the resulted variations in system states at heel strikes may have pronounced impact on the passive gaits, which have narrow basins of attraction. These results would provide insight into how the dynamic stability of passive bipedal walkers evolves with increasing surface roughness.