Guarin Diego L, Kearney Robert E
Annu Int Conf IEEE Eng Med Biol Soc. 2015;2015:6740-3. doi: 10.1109/EMBC.2015.7319940.
Dynamic joint stiffness defines the torque generated at the joint in response to position perturbations. Dynamic stiffness is modulated by the angular position and the muscle activation level, making it difficult to estimate during large movements and/or time-varying muscle contractions. This paper presents a new methodology for estimating dynamic joint stiffness during movement and muscle activation. For this, we formulate a novel, nonlinear, dynamic joint stiffness model and present a new algorithm to estimate its parameters. The algorithm assumes that the variability in the model parameters is a function of the mean joint position. Using this methodology we estimated the dynamic joint stiffness at the ankle throughout ramp and hold displacements during a constant muscle contraction. The estimated model accurately predicted the intrinsic and reflex torques produced at the ankle as a response to small position perturbations during large displacement with muscle activation. Preliminary results show that during muscle contraction, ankle intrinsic stiffness estimated during movement is significantly lower than that estimated during quasi-stationary experiments.
动态关节刚度定义了关节在响应位置扰动时产生的扭矩。动态刚度受角位置和肌肉激活水平的调节，这使得在大幅度运动和/或随时间变化的肌肉收缩过程中难以进行估计。本文提出了一种在运动和肌肉激活过程中估计动态关节刚度的新方法。为此，我们构建了一个新颖的非线性动态关节刚度模型，并提出了一种估计其参数的新算法。该算法假定模型参数的变异性是平均关节位置的函数。使用这种方法，我们在恒定肌肉收缩过程中的斜坡和保持位移期间估计了踝关节的动态关节刚度。估计模型准确地预测了在肌肉激活的大位移过程中，踝关节对小位置扰动产生的固有扭矩和反射扭矩。初步结果表明，在肌肉收缩过程中，运动期间估计的踝关节固有刚度明显低于准静态实验期间估计的刚度。
