Hemami Hooshang, Barin Kamran, Pai Yi-Chung
The Ohio State University, Columbus, OH 43210, USA.
IEEE Trans Neural Syst Rehabil Eng. 2006 Dec;14(4):470-80. doi: 10.1109/TNSRE.2006.886718.
The ankle strategy is one of the postural adjustment maneuvers humans utilize when the support platform is disturbed. This paper presents a quantitative analysis of the ankle strategy. A three-link sagittal biped model is considered. The first link represents the two legs locked together. The second link represents the two thighs locked together. The third link represents the hip, the torso, the upper limbs, the neck, and the head. The dynamics, control, and stability of the three-link biped, under platform translation, are considered. The disturbance of the platform is represented as an input and the effect of the muscular system is reduced to a set of torques applied to the joints and across the joints. Two digital computer simulations are presented to demonstrate the behavior of the biped under backward or forward platform disturbance. The simulations are compared with experimental measurements of humans subjected to postural disturbances. It is shown that the effect of a horizontal disturbance at the ankle appears to be about 40 times that of the effect of the disturbance at the knees and at least a few hundred times larger than the effect of a disturbance at the hip. This means that, under translational platform disturbance, the ankle angle is subjected to the largest excursion. The knee and the hip angle excursions are relatively minor. Consequently, the biped, as a whole, appears to move as a single inverted pendulum. Major postural corrections are initiated by the ankle excursion. Further, when the available ankle torque is limited or nonexistent, the stability requires resorting to the knee or hip strategies.
踝关节策略是人类在支撑平台受到干扰时所采用的姿势调整动作之一。本文对踝关节策略进行了定量分析。考虑了一个三连杆矢状面双足模型。第一连杆代表两条锁定在一起的腿。第二连杆代表两条锁定在一起的大腿。第三连杆代表髋部、躯干、上肢、颈部和头部。研究了平台平移时三连杆双足模型的动力学、控制和稳定性。平台的干扰被表示为输入，肌肉系统的作用被简化为施加在关节上和跨关节的一组扭矩。给出了两个数字计算机模拟，以演示双足模型在平台向后或向前干扰下的行为。将模拟结果与受到姿势干扰的人体实验测量结果进行了比较。结果表明，踝关节处水平干扰的影响似乎是膝关节处干扰影响的40倍左右，并且比髋关节处干扰的影响至少大几百倍。这意味着，在平台平移干扰下，踝关节角度的偏移最大。膝关节和髋关节角度的偏移相对较小。因此，双足整体似乎作为一个单倒立摆运动。主要的姿势校正由踝关节偏移启动。此外，当可用的踝关节扭矩有限或不存在时，稳定性需要借助膝关节或髋关节策略。
