Department of Biomedical Engineering, Case Western Reserve University, Cleveland, OH, USA.
J Biomech. 2010 Apr 19;43(6):1086-91. doi: 10.1016/j.jbiomech.2009.12.017. Epub 2010 Jan 25.
In most clinical applications of functional electrical stimulation (FES), the timing and amplitude of electrical stimuli have been controlled by open-loop pattern generators. The control of upper extremity reaching movements, however, will require feedback control to achieve the required precision. Here we present three controllers using proportional derivative (PD) feedback to stimulate six arm muscles, using two joint angle sensors. Controllers were first optimized and then evaluated on a computational arm model that includes musculoskeletal dynamics. Feedback gains were optimized by minimizing a weighted sum of position errors and muscle forces. Generalizability of the controllers was evaluated by performing movements for which the controller was not optimized, and robustness was tested via model simulations with randomly weakened muscles. Robustness was further evaluated by adding joint friction and doubling the arm mass. After optimization with a properly weighted cost function, all PD controllers performed fast, accurate, and robust reaching movements in simulation. Oscillatory behavior was seen after improper tuning. Performance improved slightly as the complexity of the feedback gain matrix increased.
在功能电刺激 (FES) 的大多数临床应用中，电刺激的时间和幅度由开环模式发生器控制。然而，上肢运动的控制将需要反馈控制来实现所需的精度。在这里，我们提出了三种使用比例微分 (PD) 反馈来刺激六个手臂肌肉的控制器，使用两个关节角度传感器。控制器首先通过最小化位置误差和肌肉力的加权和来优化，然后在包括肌肉骨骼动力学的计算手臂模型上进行评估。通过对未优化的控制器执行运动来评估控制器的通用性，并通过具有随机弱化肌肉的模型模拟来测试鲁棒性。通过添加关节摩擦和将手臂质量增加一倍来进一步评估鲁棒性。使用适当加权的成本函数进行优化后，所有 PD 控制器在模拟中都能快速、准确且稳健地进行运动。在不当调整后会出现振荡行为。随着反馈增益矩阵的复杂性增加，性能略有提高。
