Rouse Elliott J, Hargrove Levi J, Perreault Eric J, Peshkin Michael A, Kuiken Todd A
Department of Biomedical Engineering, Northwestern University, 2145 Sheridan Road, Room E310, Evanston, IL 60208, USA.
J Biomech Eng. 2013 Aug;135(8):81009. doi: 10.1115/1.4024286.
The mechanical properties of human joints (i.e., impedance) are constantly modulated to precisely govern human interaction with the environment. The estimation of these properties requires the displacement of the joint from its intended motion and a subsequent analysis to determine the relationship between the imposed perturbation and the resultant joint torque. There has been much investigation into the estimation of upper-extremity joint impedance during dynamic activities, yet the estimation of ankle impedance during walking has remained a challenge. This estimation is important for understanding how the mechanical properties of the human ankle are modulated during locomotion, and how those properties can be replicated in artificial prostheses designed to restore natural movement control. Here, we introduce a mechatronic platform designed to address the challenge of estimating the stiffness component of ankle impedance during walking, where stiffness denotes the static component of impedance. The system consists of a single degree of freedom mechatronic platform that is capable of perturbing the ankle during the stance phase of walking and measuring the response torque. Additionally, we estimate the platform's intrinsic inertial impedance using parallel linear filters and present a set of methods for estimating the impedance of the ankle from walking data. The methods were validated by comparing the experimentally determined estimates for the stiffness of a prosthetic foot to those measured from an independent testing machine. The parallel filters accurately estimated the mechatronic platform's inertial impedance, accounting for 96% of the variance, when averaged across channels and trials. Furthermore, our measurement system was found to yield reliable estimates of stiffness, which had an average error of only 5.4% (standard deviation: 0.7%) when measured at three time points within the stance phase of locomotion, and compared to the independently determined stiffness values of the prosthetic foot. The mechatronic system and methods proposed in this study are capable of accurately estimating ankle stiffness during the foot-flat region of stance phase. Future work will focus on the implementation of this validated system in estimating human ankle impedance during the stance phase of walking.
人体关节的力学特性（即阻抗）会不断被调节，以精确控制人体与环境的交互。对这些特性的估计需要关节偏离其预期运动，并随后进行分析，以确定施加的扰动与由此产生的关节扭矩之间的关系。对于动态活动期间上肢关节阻抗的估计已经有很多研究，但步行过程中踝关节阻抗的估计仍然是一个挑战。这种估计对于理解人体踝关节的力学特性在运动过程中是如何被调节的，以及这些特性如何在旨在恢复自然运动控制的人工假肢中得到复制非常重要。在这里，我们介绍了一个机电一体化平台，旨在解决步行过程中估计踝关节阻抗刚度分量的挑战，其中刚度表示阻抗的静态分量。该系统由一个单自由度机电一体化平台组成，该平台能够在步行的支撑阶段扰动踝关节并测量响应扭矩。此外，我们使用并行线性滤波器估计平台的固有惯性阻抗，并提出了一组从步行数据估计踝关节阻抗的方法。通过将实验确定的假肢脚刚度估计值与独立测试机测量的值进行比较，对这些方法进行了验证。当跨通道和试验进行平均时，并行滤波器准确地估计了机电一体化平台的惯性阻抗，占方差的96%。此外，我们发现我们的测量系统能够产生可靠的刚度估计值，在运动支撑阶段的三个时间点进行测量时，与假肢脚独立确定的刚度值相比，平均误差仅为5.4%（标准差：0.7%）。本研究中提出的机电一体化系统和方法能够在支撑阶段的足平区域准确估计踝关节刚度。未来的工作将集中于在步行支撑阶段估计人体踝关节阻抗时实施这个经过验证的系统。
