Cho Kwonseung, Lee Kang-Woo, Hur Pilwon
Department of Mechanical and Robotics Engineering, Gwangju Institute of Science and Technology, Gwangju, 61005, South Korea.
Sci Rep. 2025 Sep 26;15(1):33268. doi: 10.1038/s41598-025-17957-4.
The human metatarsophalangeal joint-often referred to as the "toe joint"-plays a vital role in gait by supporting body weight during mid-stance, enabling smooth rollover from heel to toe, and facilitating effective push-off in terminal stance. However, identifying its optimal stiffness remains challenging despite its relevance to both biological and robotic locomotion. In this study, we used a simulation-based trajectory optimization approach to investigate toe joint stiffness in a bipedal model. The results revealed that lower stiffness facilitated rollover while higher stiffness enhanced push-off. Because continuously varying stiffness is impractical in most passive devices, we extracted a single representative value (0.98 Nm/deg) by averaging the time-varying stiffness during the push-off phase. We then conducted a human walking experiment using adjustable toe joint boots across multiple stiffness conditions. The 0.98 Nm/deg condition yielded the highest subjective satisfaction and favorable spatiotemporal outcomes, especially among participants with anthropometry similar to the simulation model. Although direct numerical comparison between simulation and experiment was not performed due to modeling simplifications, key qualitative trends-such as toe joint moment progression and heel-off timing-were consistent. These findings highlight the potential of toe joint stiffness tuning to improve walking performance and user experience.
人类的跖趾关节——通常被称为“脚趾关节”——在步态中起着至关重要的作用，在站立中期支撑体重，使从脚跟到脚趾的过渡顺畅，并在站立末期促进有效的蹬地动作。然而，尽管其与生物和机器人运动都相关，但确定其最佳刚度仍然具有挑战性。在本研究中，我们使用基于模拟的轨迹优化方法来研究双足模型中的脚趾关节刚度。结果表明，较低的刚度有助于过渡，而较高的刚度则增强蹬地效果。由于在大多数被动装置中连续改变刚度不切实际，我们通过对蹬地阶段随时间变化的刚度进行平均，提取了一个单一的代表性值（0.98 Nm/deg）。然后，我们使用可调节脚趾关节靴在多种刚度条件下进行了人体步行实验。0.98 Nm/deg的条件产生了最高的主观满意度和良好的时空结果，尤其是在人体测量学与模拟模型相似的参与者中。尽管由于建模简化未进行模拟与实验之间的直接数值比较，但关键的定性趋势——如脚趾关节力矩变化和脚跟离地时间——是一致的。这些发现凸显了调整脚趾关节刚度以改善步行性能和用户体验的潜力。
