Department of Mechanical Engineering, Vanderbilt University, Nashville, TN 37235, USA.
IEEE Trans Biomed Eng. 2011 Jan;58(1):144-51. doi: 10.1109/TBME.2010.2070840. Epub 2010 Aug 30.
This paper presents a method for providing volitional control of a powered knee prosthesis during nonweight-bearing activity such as sitting. The method utilizes an impedance framework, such that the joint can be programmed with a given stiffness and damping that reflects the nominal impedance properties of an intact joint. Volitional movement of the knee joint is commanded via the stiffness set-point angle of the joint impedance, which is commanded by the user as a function of the measured surface electromyogram (EMG) from the hamstring and quadriceps muscles of the residual limb. Rather than using the respective EMG measurements from these muscles to directly command the flexion or extension set point of the knee, the presented approach utilizes a combination of quadratic discriminant analysis and principal component analysis to align the user's intent to flex or extend the knee joint with the pattern of measured EMG. The approach was implemented on three transfemoral amputees, and their ability to control knee movement was characterized by a set of knee joint trajectory tracking tasks. Each amputee subject also performed the same set of trajectory tracking tasks with his sound side (intact) knee joint. The average root mean square trajectory tracking errors of the prosthetic knee employing the EMG-based volitional control and the intact knee of the three subjects were 6.2° and 5.2°, respectively.
本文提出了一种在非承重活动（如坐立）期间为动力膝关节假肢提供自主控制的方法。该方法利用了阻抗框架，使得关节可以被编程为具有给定的刚度和阻尼，反映完整关节的标称阻抗特性。膝关节的自主运动通过关节阻抗的刚度设定点角度来命令，该角度由用户根据残肢的腘绳肌和四头肌的测量表面肌电图（EMG）来命令。该方法不是直接使用这些肌肉的各自 EMG 测量值来直接命令膝关节的弯曲或伸展设定点，而是利用二次判别分析和主成分分析相结合的方法，将用户弯曲或伸展膝关节的意图与测量的 EMG 模式对齐。该方法在三名股骨截肢者身上进行了实施，并通过一系列膝关节轨迹跟踪任务来描述他们控制膝关节运动的能力。每个截肢者还使用其健全侧（完整）膝关节执行了相同的轨迹跟踪任务。三名受试者中，使用基于 EMG 的自主控制的假肢膝关节的平均均方根轨迹跟踪误差为 6.2°，而健全侧膝关节的平均均方根轨迹跟踪误差为 5.2°。
