MacKay W A, Crammond D J, Kwan H C, Murphy J T
J Biomech. 1986;19(3):231-8. doi: 10.1016/0021-9290(86)90155-7.
In human subjects, stiffness of the relaxed elbow was measured by three methods, using a forearm manipulandum coupled to a.d.c. torque motor. Elbow stiffness calculated from frequency response characteristics increased as the driving amplitude decreased. Step displacements of the forearm produced restoring torques linearly related to the displacement. The stiffness was very similar to that calculated from natural frequencies at amplitudes above 0.1 rad. Thirdly, elbow stiffness was estimated from brief test pulses, 120 ms in duration, by mathematically simulating the torque-displacement functions. Stiffness values in the limited linear range (under +/- 0.1 rad) were higher than in the linear range of the first two methods. A major component of elbow stiffness appears to decay within 1 s. The coefficients of viscosity determined from the simulation were, however, very similar to those calculated from the frequency response. Test pulse simulation was then used to determine joint impedance for different, actively maintained elbow angles. Joint stiffness and viscosity increased with progressive elbow flexion.
在人体受试者中，使用与直流扭矩电机相连的前臂操作器，通过三种方法测量放松状态下肘部的刚度。根据频率响应特性计算出的肘部刚度随着驱动幅度的减小而增加。前臂的阶跃位移产生与位移呈线性相关的恢复扭矩。在幅度高于0.1弧度时，该刚度与根据固有频率计算出的刚度非常相似。第三，通过对持续时间为120毫秒的简短测试脉冲进行数学模拟扭矩 - 位移函数，来估计肘部刚度。在有限线性范围（±0.1弧度以内）的刚度值高于前两种方法的线性范围内的刚度值。肘部刚度的一个主要成分似乎在1秒内衰减。然而，从模拟中确定的粘度系数与根据频率响应计算出的系数非常相似。然后使用测试脉冲模拟来确定不同主动维持的肘部角度下的关节阻抗。关节刚度和粘度随着肘部逐渐屈曲而增加。
