Department of Mechanical Engineering and Science, Graduate School of Engineering, Kyoto University, Kyoto-Daigaku-Katsura, Nishikyo-ku, Kyoto, 615-8540, Japan.
Bioinspir Biomim. 2020 Jul 7;15(5):055001. doi: 10.1088/1748-3190/ab968d.
Quadruped animals use not only their legs but also their trunks during walking and running. Although many previous studies have investigated the flexion, extension, and lateral bending of the trunk, few studies have investigated the body torsion, and its dynamic effects on locomotion thus remain unclear. In this study, we investigated the effects of body torsion on gait stability during trotting and pacing. Specifically, we constructed a simple model consisting of two rigid bodies connected via a torsional joint that has a torsional spring and four leg springs. We then derived periodic solutions for trotting and pacing and evaluated the stabilities of these motion types using a Poincaré map. We found that the moments of inertia of the bodies and the spring constant ratio of the torsional spring and the leg springs determine the stability of these periodic solutions. We then determined the stability conditions for these parameters and elucidated the relevant mechanisms. In addition, we clarified the importance of the body torsion to the gait stability by comparison with a rigid model. Finally, we analyzed the biological relevance of our findings and provided a design principle for development of quadruped robots.
四足动物在行走和奔跑时不仅使用它们的腿，还使用它们的躯干。尽管许多先前的研究已经研究了躯干的弯曲、伸展和侧向弯曲，但很少有研究研究过身体扭转，因此其对运动的动态影响尚不清楚。在这项研究中，我们研究了身体扭转对小跑和踱步时步态稳定性的影响。具体来说，我们构建了一个由两个刚体通过一个带有扭转弹簧和四个腿弹簧的扭转关节连接而成的简单模型。然后，我们推导出了小跑和踱步的周期解，并使用庞加莱映射评估了这些运动类型的稳定性。我们发现，物体的转动惯量和扭转弹簧与腿弹簧的弹簧常数比决定了这些周期解的稳定性。然后，我们确定了这些参数的稳定性条件，并阐明了相关的机制。此外，我们通过与刚体模型的比较，阐明了身体扭转对步态稳定性的重要性。最后，我们分析了我们发现的生物学相关性，并为四足机器人的开发提供了设计原则。
