基于功能性电刺激的上肢康复系统条件反馈控制

功能性电刺激是脑卒中患者有效的康复方法,然而上肢肌肉的动态模型存在着强非线性、多源扰动、模型不精确和参数变化大等控制难点.为提高基于功能性电刺激的上肢康复系统的跟踪速度和扰动抑制能力,本文提出了一种基于条件反馈的比例–积分控制策略,条件反馈的设计用于提高系统的跟踪性能,通过比例–积分控制器抑制外部扰动与模型不确定性.通过单一变量法分析了控制器参数对控制效果的影响,提出了一种简单、实用的参数整定规则.基于Hammerstein肌骨系统模型,通过仿真验证了所提方法在保证闭环系统鲁棒性的前提下,与常规的比例–积分控制器相比在跟踪和扰动抑制性能方面的优势.最后,基于搭建的上肢康复系统控制平台,对不同实验者在不同目标输出力下进行对比实验,实验结果表明本文所提基于条件反馈的比例–积分控制策略的平均峰值量占比为9.22%,而对比控制策略的平均峰值量占比为17.80%,所提控制策略的平均单位误差绝对值积分指标是对比控制策略平均单位误差绝对值积分指标的70.43%,验证了本文所设计的控制策略在保证闭环系统鲁棒性的前提下具有更好的跟踪效果.

Conditional feedback control of upper limb rehabilitation system based on functional electrical stimulation

Functional electrical stimulation is an effective rehabilitation method for stroke patients, however, the muscular dynamic models of upper limbs face many control difficulties such as strong nonlinearity, multi-source disturbance, inaccurate model and large-varying parameters. In order to improve the tracking speed and disturbance rejection ability of the upper limb rehabilitation system based on functional electrical stimulation, a proportional-integral control strategy based on conditional feedback control is proposed in this paper, where the design of conditional feedback can improve the tracking performance, and the external disturbance and the model uncertainties are handled by proportional-integral controller. Based on the influence analyses on the control performance by the single variable method, a simple and practical tuning rule is proposed. Based on the Hammerstein model of musculoskeletal system, simulation results show that the proposed control method can obtain better tracking and disturbance rejection performance than the regular proportional-integral controller with stronger robustness. Finally, comparative experiments are carried out with different target output forces on different experimenters based on the control platform of upper limb rehabilitation system based on functional electrical stimulation. Experimental data indicate that the average peak proportion of the proposed proportional-integral control strategy based on conditional feedback control is 9.22%, while the average peak proportion of the comparative control strategy is 17.80%. Besides, the average unit integral of absolute error index of the proposed control strategy is 70.43% of the average unit absolute error index of the comparative control strategy. It can be learnt that the proposed control strategy can obtain better tracking performance with satisfactory robustness of the closed-loop system.