CAREER: Nonlinear Control of Human Skeletal Muscle

这一职业奖旨在为人类骨骼肌人工电刺激的非线性控制方法发展一个综合的研究和教育基础。目前通过应用电刺激治疗医学疾病的临床实践是基于患者独立的方案，用于对刺激参数(例如，幅度、相位和脉冲持续时间)进行开环调整。关于闭环电刺激的研究要么基于纯反馈控制，要么基于反馈控制，并加入由软计算元件(例如，人工神经网络、模糊逻辑集)组成的前馈组件。不幸的是，这些方法没有充分利用正在进行的研究的潜在好处，这些研究的重点是更有效地模拟肌肉反应。该项目的研究工作将集中在非线性控制方法的开发和实验验证上，该方法将肌肉模型纳入设计和分析，作为一种实现可预测响应的手段，尽管受试者内和受试者之间存在差异，肌肉的力量生产能力也是如此。这项研究的结果将通过开发新的数学模型来促进人工电刺激研究的知识，这些数学模型可以用来改变刺激参数以减少疲劳。这些模型将被首次用于基于Lyapunov的方法，作为一种将肌肉反应现象封装在神经肌肉电刺激控制器中的手段。基于李亚普诺夫的方法将被用来设计呈现输入饱和并适应时变的受试者间和受试者内变化的控制器，产生可定制的神经假体。通过临床应用以及建模和控制研究的科学进步影响社会的研究努力有直接的结果，但进一步的结果将由学生接触到人机交互技术以及科学和工程对疾病和残疾治疗的影响而产生。神经肌肉电刺激(即通过内部或外部电极施加电流导致肌肉收缩)为治疗或减轻与某些疾病和功能障碍相关的衰弱发病率提供了巨大的希望。神经肌肉电刺激目前被用来治疗各种疾病，由于中风和脊髓损伤等运动障碍患者日常生活能力的潜在改善，神经肌肉电刺激已经迅速增长。每年有100多万美国人受到这些障碍的影响。除了作为一种治疗方法，神经肌肉电刺激还可以为身体提供人工延伸(即神经假体)，以恢复或补充因疾病或伤害而丧失的功能，目的是减少由此对社会的影响，提高个人的生活质量。这种神经假体的吸引力在于，人体自身的肌肉被用来恢复运动，从而产生显著的次要好处，如减少肌肉萎缩和相关的新陈代谢变化，降低心力衰竭的风险，心力衰竭是脊髓损伤患者的主要死亡原因。不幸的是，目前的商业电刺激产品对患者产生的功能结果有限，因为使用的特别刺激策略不是针对患者的，并且会导致快速的肌肉疲劳。该项目的目标是开发新的电刺激控制器，这种控制器(1)能够进行长时间的体力活动，(2)可以定制并适应不断变化的肌肉骨骼系统。为了实现这些目标，努力将重点放在通过将神经肌肉模型结合到新的自适应控制设计中来弥合目前生物生理学研究和控制工程研究之间的差距，以获得所需的肌肉反应。考虑到这种新兴研究对个人生活质量的潜在好处以及对社会的影响，包括运动系统神经假体、神经调节设备和治疗性肌肉刺激器在内的神经技术产品的全球市场预计将从2004年的24亿美元增长到2008年的72亿美元。

AbstractThis CAREER award seeks to develop an integrated research and educational foundation in nonlinear control methods for artificial electrical stimulation of human skeletal muscle. Current clinical practices for treating medical disorders through the application of electrical stimulation are based on patient independent protocols for the open-loop adjustment of stimulation parameters (e.g., amplitude, phase, and pulse duration). Research focused on closed-loop electrical stimulation is based on either pure feedback control or feedback control with the addition of a feedforward component composed of soft computing elements (e.g., artificial neural networks, fuzzy logic sets). Unfortunately, these methods do not fully exploit the potential benefits of on-going research focused at more effectively modeling muscle response. Research efforts in this project will focus on the development and experimental validation of nonlinear control methodologies that incorporate muscle models in the design and analysis as a means to achieve a predictable response despite intra- and inter-subject variability and fatigable force production capabilities of the muscle. Outcomes of this research will advance knowledge in artificial electrical stimulation research through the development of new mathematical models that can be used to alter stimulation parameters to reduce fatigue. These models will be incorporated in the first ever use of Lyapunov-based methods as a means to encapsulate muscle response phenomena in a neuromuscular electrical stimulation controller. Lyapunov-based methods will be used to design controllers that exhibit input saturation and are adaptive to time-varying inter- and intra-subject variations, yielding a customizable neuroprosthesis. There are direct outcomes of the research efforts that impact society through the clinical applications and the scientific advancement of modeling and control research, but further outcomes will result by the exposure of students to human-machine interaction technologies and the impacts of science and engineering for the treatment of disease and disability.Neuromuscular electrical stimulation (i.e., the application of an electrical current via internal or external electrodes which results in a muscle contraction) offers an enormous promise to treat or alleviate the debilitating morbidity associated with certain diseases and dysfunctional conditions. Neuromuscular electrical stimulation is currently prescribed to treat a wide range of disorders and has rapidly grown because of the potential improvement in the activities of daily living for individuals with movement disorders such as stroke and spinal cord injuries that affect over one million Americans annually. In addition to serving as a treatment, neuromuscular electrical stimulation can provide an artificial extension to the body (i.e., a neural prosthetic) to restore or supplement function lost due to disease or injury with the goal of reducing the resulting implications on society and improving the quality of life of individuals. An attraction of such a neuroprosthesis is that the bodys own muscles are used to restore movement, leading to significant secondary benefits such as reducing muscle atrophy and the associated changes in metabolism and reduced risk for heart failure, the leading cause of death among individuals with spinal cord injuries. Unfortunately, current commercial electrical stimulation products have yielded limited functional outcomes for patients because ad hoc stimulation strategies are used that are not patient specific and lead to rapid muscle fatigue. The goals of this project are to develop new electrical stimulation controllers that (1) would enable long periods of physical activity that (2) could be customized and adapt to an individuals ever changing musculoskeletal system. To achieve the goals, efforts will focus on bridging the current gap between biological physiology research and control engineering research by incorporating neuromuscular models in novel adaptive control designs that elicit a desired muscle response. Given the potential benefits to the quality of life of an individual and the impacts on society of such emerging research, the worldwide market for neurotechnology products including motor system neuroprostheses, neuromodulation devices, and therapeutic muscle stimulators is predicted to grow from $2.4 billion in 2004 to $7.2 billion by 2008.