Automatic Control of Cycling Induced by Functional Electrical Stimulation With Electric Motor Assistance
Automatic Control of Cycling Induced by Functional Electrical Stimulation With Electric Motor Assistance
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DOI：
10.1109/tase.2016.2527716
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发表时间：
2017-04-01
影响因子：
5.6
通讯作者：
Dixon, Warren E.
中科院分区：
文献类型：
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作者：
Bellman, Matthew J.;Downey, Ryan J.;Dixon, Warren E.
自动控制功能电刺激诱导的自行车运动为瘫痪患者提供了一种治疗锻炼和功能恢复的手段。在由功能性电刺激诱导的骑行过程中，根据自行车的曲柄角度刺激不同的肌肉群；然而，由于自行车-骑手系统的运动学限制，刺激通常仅在曲柄循环的一部分进行。因此，这些系统可以被认为是具有自治的、具有潜在不稳定模式的状态相关切换的切换控制系统。以前的研究已经在系统中加入了电机，以提供额外的控制权限，但还没有研究在电动功能性电刺激自行车系统的稳定性分析中考虑切换控制的影响。本文提出了一种考虑开关控制输入影响的功能性电刺激摩托车骑行系统模型。一种新颖的电动马达切换策略被设计为仅在骑手肌肉运动效率较低的曲柄循环区域提供帮助。设计了切换滑模控制器，并通过李亚普诺夫方法保证了对期望曲柄轨迹的全局指数稳定跟踪，尽管存在非线性模型中的参数不确定性和未知的时变扰动。给出了五名健全的被动骑手的实验结果，以验证控制设计，开发的控制系统在每分钟50转的期望轨迹上实现了每分钟50转的平均节奏跟踪误差。从业者注意-为残疾人(如瘫痪)的康复和功能援助而设计的自主系统具有最大化康复结果和提高数百万人生活质量的潜力。由于失去神经肌肉控制，瘫痪等疾病会极大地降低一个人完成任务的能力。功能性电刺激可以激活瘫痪的肌肉，通过自动向神经肌肉系统施加电流来恢复功能能力，当应用于自行车等任务时，既具有康复作用，又具有赋能作用。然而，由功能性电刺激诱导的自行车骑行受到骑手肌肉能力的限制，因此通常会增加一个电动马达来适应骑手的能力和支持稳定性。肌肉对电刺激的反应是不确定的、时变的和非线性的，跨多个肌肉组以及在骑手和电动马达之间切换控制输入使得确保稳定性和性能具有挑战性。本文提出了一种利用功能性电刺激控制机动自行车系统的新方法，该方法考虑了切换效应，并保证了对期望曲柄轨迹的指数稳定跟踪，实验结果表明，该控制系统可以应用于康复骑行任务。未来研究的方向是在瘫痪患者群体中实施开发的控制系统，以量化其对肌肉功能和神经可塑性等治疗结果的影响。
Cycling induced by automatic control of functional electrical stimulation provides a means of therapeutic exercise and functional restoration for people affected by paralysis. During cycling induced by functional electrical stimulation, various muscle groups are stimulated according to the cycle crank angle; however, because of kinematic constraints on the cycle-rider system, stimulation is typically only applied in a subsection of the crank cycle. Therefore, these systems can be considered as switched control systems with autonomous, state-dependent switching with potentially unstable modes. Previous studies have included an electric motor in the system to provide additional control authority, but no studies have considered the effects of switched control in the stability analysis of the motorized functional electrical stimulation cycling system. In this paper, a model of the motorized cycle-rider system with functional electrical stimulation is developed that includes the effects of a switched control input. A novel switching strategy for the electric motor is designed to only provide assistance in the regions of the crank cycle where the kinematic effectiveness of the rider's muscles is low. A switched sliding-mode controller is designed, and global, exponentially stable tracking of a desired crank trajectory is guaranteed via Lyapunov methods for switched systems, despite parametric uncertainty in the nonlinear model and unknown, time-varying disturbances. Experimental results from five able-bodied, passive riders are presented to validate the control design, and the developed control system achieves an average cadence tracking error of revolutions per minute for a desired trajectory of 50 revolutions per minute.Note to Practitioners-Autonomous systems designed for rehabilitation and functional assistance for people with disabilities such as paralysis have the potential to maximize rehabilitative outcomes and improve the quality of life for millions of people. Disorders such as paralysis drastically reduce a person's ability to complete tasks due to a loss of neuromuscular control. Functional electrical stimulation can activate paralyzed muscles, restoring functional ability through automated application of electric current to the neuromuscular system, and, when applied to a task such as cycling, is both rehabilitative and empowering. However, cycling induced by functional electrical stimulation is limited by the capability of the rider's muscles, so an electric motor is typically added to accommodate the rider's ability and to support stability. The response by muscle to electrical stimulation is uncertain, time-varying, and nonlinear, and switching the control input across multiple muscle groups and between the rider and an electric motor make guaranteeing stability and performance challenging. This paper presents a novel approach to the challenge of controlling motorized cycling systems with functional electrical stimulation that considers the switching effects and guarantees exponentially stable tracking of a desired crank trajectory, and experimental results indicate how the control system may be applied to a rehabilitative cycling task. Directions for future research are aimed at implementation of the developed control system in patient populations with paralysis to quantify its impact on therapeutic outcomes such as muscle function and neuroplasticity.