Robot feet are crucial for maintaining dynamic stability and propelling the body during walking, especially on uneven terrains. Traditionally, robot feet were mostly designed as flat and stiff pieces of metal, which meets its limitations when the robot is required to step on irregular grounds, e.g., stones. While one could think that adding compliance under such feet would solve the problem, this is not the case. To address this problem, we introduced the SoftFoot, an adaptive foot design that can enhance walking performance over irregular grounds. The proposed design is completely passive and varies its shape and stiffness based on the exerted forces, through a system of pulley, tendons, and springs opportunely placed in the structure. This article outlines the motivation behind the SoftFoot and describes the theoretical model which led to its final design. The proposed system has been experimentally tested and compared with two analogous conventional feet, a rigid one and a compliant one, with similar footprints and soles. The experimental validation focuses on the analysis of the standing performance, measured in terms of the equivalent support surface extension and the compensatory ankle angle, and the rejection of impulsive forces, which is important in events such as stepping on unforeseen obstacles. Results show that the SoftFoot has the largest equivalent support surface when standing on obstacles, and absorbs impulsive loads in a way almost as good as a compliant foot.

中文翻译：

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SoftFoot 的分析模型和实验测试：用于跨越障碍物和不规则地形的自适应机器人脚


机器人脚对于保持动态稳定性和行走过程中推动身体至关重要，尤其是在不平坦的地形上。传统上，机器人脚大多设计为平坦且坚硬的金属件，当机器人需要踩在不规则的地面（例如石头）上时，这就满足了其局限性。虽然人们可能认为在这样的基础上增加合规性就能解决问题，但事实并非如此。为了解决这个问题，我们推出了 SoftFoot，这是一种自适应足部设计，可以增强在不规则地面上的行走性能。所提出的设计是完全被动的，通过适当放置在结构中的滑轮、腱和弹簧系统，根据施加的力改变其形状和刚度。本文概述了 SoftFoot 背后的动机，并描述了导致其最终设计的理论模型。所提出的系统已经过实验测试，并与具有相似足迹和鞋底的两个类似的传统脚（刚性脚和柔性脚）进行了比较。实验验证的重点是分析站立性能，以等效支撑面延伸和补偿性踝关节角度来测量，以及对脉冲力的抑制，这对于踩到不可预见的障碍物等事件非常重要。结果表明，当站在障碍物上时，SoftFoot 具有最大的等效支撑表面，并且吸收冲击载荷的方式几乎与顺应脚一样好。