基于迭代学习控制的肘关节功能性电刺激系统

为帮助肢体功能障碍患者上肢运动功能的康复和重建,本文设计针对肘关节运动康复的功能性电刺激(functional electrical stimulation,FES)系统。首先应用动态神经网络建立电刺激下肘关节运动的模型。根据模型的非线性与肘关节运动轨迹的重复性,采用迭代学习控制(iterative learning control,ILC)算法设计FES系统的控制器,实现肘关节角度精确控制的FES系统。经过10次迭代控制,肘关节实际运动轨迹与期望轨迹之间的最大误差为0.438°,相对平均误差为0.32%,均方根误差为0.245°。结果表明,所设计的基于ILC算法的FES系统能够实现肘关节运动功能性电刺激的精确控制,对帮助肘关节运动康复的FES系统研究具有一定的指导意义。     

多速率数据采集与处理系统的设计与实现

在非协作通信中需要根据信号带宽调整中频采样速率,以便降低后端盲信号处理的复杂度,实现信号调制方式的识别与信号参数的估计,从而实现信号的解调。本文介绍了一种基于嵌入式计算机模块、高速AD芯片和数据处理软件的多速率数据采集处理系统,该系统具备400ksps至25.6 Msps实时采集和51.2 Msps、80 Msps、93.33 Msps高速采集及信号处理等功能,达到了对中频信号记录和分析目的。     

基于RFMRA和改进PNGV模型的锂离子电池SOC估算

提出基于渐消记忆的递推算法(RFMRA)和改进的新一代汽车合作伙伴(PNGV)等效电路模型的锂离子电池荷电状态(SOC)在线估算方法.RFMRA在传统递推最小二乘算法的基础上加入遗忘因子,使在线参数辨识能更实时地反映模型参数;在PNGV模型上串联RC回路,可更精确地体现电池特性.与离线SOC估算相比,算法的最大误差降低35.106％,平均绝对误差(MAE)降低7.21％,平均绝对值百分比误差(MAPE)降低22.42％,均方根误差(RMSE)降低25.38％.     

开关磁阻电动机角度在线调制策略研究

为改善中低速段开关磁阻电动机(SRD)动态响应性能,提出了一种SRD控制角度在线调制策略。控制器依据相电流建立与退磁过程确定误差,在线调节开通角度与关断角度。设计了基于角度的在线调制策略的速度闭环控制器,通过引入误差反馈量,增加了系统稳定性。样机实验结果表明,角度在线调制策略能够有效改善SRD中低速段电流响应,并有效减少相电流峰值,提高系统效率。     

模型不确定的下肢康复机器人轨迹跟踪自适应控制

为了实现康复训练过程中高精度的轨迹跟踪控制,针对下肢康复机器人的模型参数和外界干扰等不确定性因素对其轨迹跟踪造成严重影响,提出一种模型不确定的下肢康复机器人轨迹跟踪自适应控制方法。根据所提方案,设计了相应的轨迹跟踪自适应控制器;并进行了轨迹跟踪控制仿真实验对比分析,结果表明,计算力矩控制方法在系统模型不确定时,膝关节的最大角度跟踪误差高达11.3°,髋关节最大稳态误差4.6°;而轨迹跟踪自适应控制方法在模型不确定的情况下,髋关节和膝关节的角度跟踪稳态误差均收敛于零;轨迹跟踪自适应控制方法可以显著提高下肢康复机器人轨迹跟踪的精度。     

通用伺服转矩监视信号在等速肌力测试系统中的应用

为避免等速肌力测试系统需额外动态转矩传感器的问题,研究了一种基于带转矩监视信号的通用伺服装置的实现方法。在伺服电机速度模式下,利用编码器反馈设计了具有速度闭环的控制器,实现肌力测试过程中的精确等速运动;通过伺服自带的转矩监视信号检测施加到电机转子上的转矩,并转换得到肌力信息。利用Simulink软件和Quanser Q8运动控制器构建了等速肌力测试半实物仿真系统。为验证该方法的可行性,选取5名在校男大学生,分别测量肘关节肌肉群多运动参数,并与现有运动参数进行比较。结果表明,峰力矩(PT)等指标均在所测指标的波动范围内,说明该系统实现方法在等速肌力测试方面具有实用价值。     

基于闭环算法的光学电流互感器的暂态电流误差特性研究北大核心CSCD

基于对光学电流互感器闭环调制解调算法的数学分析,研究了闭环算法对一次电流的计算误差来源,证实闭环算法的计算误差只与一次电流的变化速率相关,并在此基础上研究了暂态电流工况下,典型光CT的误差特性,探讨了减小暂态电流误差的几类措施并进行试验验证,证实减少传感光纤匝数、缩短光路总长度以及线性度误差实时补偿均可有效修正闭环算法的计算误差,提高互感器的暂态电流精度。     

基于非均匀高斯函数的无刷直流电动机模糊控制

采用一种基于非均匀高斯型隶属函数的模糊PI控制算法来实现无刷直流电机闭环调速控制.根据转速误差E和误差变化率EC在控制过程中非均匀分布的特点,构建相应的非均匀高斯型隶属函数模糊控制器来实时调整PI控制器的两个参数KP,KI.并运用Matlab/Simulink结合Fuzzy工具箱实现了对BLDCM系统的仿真.仿真结果表明:基于非均匀高斯型隶属函数的模糊PI控制与普通模糊PI控制相比,具有更好的动态、稳态性能,更强的鲁棒性及更高的控制精度.     

变压器油纸绝缘系统低频介电参数方程

油纸绝缘系统频域介电谱的低频部分更有利于诊断、评估绝缘系统的老化状态与水分含量,为了将频域介电响应法更好地应用到工程中,针对变压器油纸绝缘系统低频激励下的介电响应进行了研究。首先分析了绝缘电介质(油隙、油浸纸)在低频激励下的电极极化过程,进而提出以电导率、离子迁移率等为参量的绝缘电介质的介电参数方程;然后基于变压器油纸绝缘系统的XY几何等效模型,构建变压器油纸绝缘系统低频介电参数方程;最后通过试验对所构建的介电参数方程进行验证。研究结果表明:油纸绝缘系统介电参数计算值与试验值相符合,建立的介电参数方程能够有效地表征变压器油纸绝缘系统频域介电响应低频部分的介电参数。     

次同步振荡动态稳定器抑制弱阻尼次同步振荡的机理与实验

针对呼盟系统呼伦贝尔电厂存在的弱阻尼次同步振荡问题,实际工程采用次同步振荡动态稳定器(SSO-DS)进行抑制。文中提出了一种适用于SSO-DS的瞬时无功功率次同步调制策略,基于复转矩系数法推导出该控制策略下SSO-DS提供的阻尼,给出了影响其阻尼大小的相关因素;搭建了实时数字—物理闭环仿真平台,并基于弱阻尼次同步振荡问题,提出了确定其有效阻尼区域的方法,对控制器参数进行优化。闭环仿真及现场实验均验证了SSO-DS控制策略的有效性以及闭环仿真实验参数优化的准确性。     

Improving signal reliability for on-line joint angle estimation from nerve cuff recordings of muscle afferents

Closed-loop functional electrical stimulation (FES) applications depend on sensory feedback, thus, it is important to continuously investigate new methods to obtain reliable feedback signals. The objective of the present paper was to examine the feasibility of using an artificial neural network (ANN) to predict joint angle from whole nerve cuff recordings of muscle afferent activity within a physiological range of motion. Furthermore, we estimated how small changes in joint angle that can be detected from the nerve cuff recordings. Neural networks were tested with data obtained from ten acute rabbit experiments in simulated, on-line experiments. The electroneurograms (ENG) of the tibial and peroneal nerves were recorded during passive ankle joint rotation. To decrease the joint angle prediction error with new rabbit data, we attempted to pretune the nerve signals and re-trained the ANNs with the pretuned data. With these procedures we were able to compensate for interrabbit variability. On average the mean prediction errors were less than 2.0/spl deg/ (a total excursion of 20/spl deg/) and we were able to predict joint angles from muscle afferent activity with accuracy close to the best-estimated angular resolution. The angular resolution was found to depend on the initial joint angle and the actual step size taken and we found that there was a low probability of detecting joint angle changes less than 1.5/spl deg/. We thus suggest that muscle afferent activity is applicable as feedback in real-time closed-loop control, when the motion speed is restricted and when the movement is limited to a portion of the joint's physiological range.     

Strategies for generating prolonged functional standing using intramuscular stimulation or intraspinal microstimulation.

Spinal cord injury (SCI) often results in the loss of the ability to stand. The goal of this study was to implement a functional electrical stimulation (FES) system for restoring prolonged periods of standing after SCI. For this purpose, we tested two control strategies: open-loop and closed-loop control, and two stimulation paradigms: non-interleaved intramuscular stimulation (IM-S) and interleaved intraspinal microstimulation (ISMS). The experiments were conducted in anesthetized cats. Stimulation was applied to the muscles through IM-S electrodes implanted in the main knee and ankle extensor muscles, or to the spinal cord through ultra-fine ISMS wires implanted within the ventral horn of the lumbosacral enlargement. The cats were partially supported over parallel force plates and accelerometers were secured to the hindlimbs above and below the ankle joint. Ground reaction forces and knee and ankle joint angles were measured by the force plates and accelerometers, respectively. The closed-loop controller used these feedback signals to modulate the amplitude of stimulation applied to the extensor muscles. The open-loop controller applied constant levels of stimulation which were determined before the onset of each trial. The duration of standing achieved using closed-loop control of IM-S was significantly longer than that achieved with open-loop control (approximately 2 times longer). The increase in the duration of standing corresponded with a decrease in the rate of force decay and a lower average injected current during closed-loop control. Standing was further improved with the use of ISMS. Closed-loop control of interleaved ISMS resulted in a period of standing > 3 times longer than the best trial generated using non-interleaved IM-S. There was also a significant improvement in the balance of force between the two hindlimbs. The results suggest that a system which uses closed-loop control in conjunction with interleaved ISMS could achieve prolonged FES standing in people with SCI.     

基于欧拉角的关节活动度测量系统

人体关节活动度的测量在司法鉴定、康复医学等领域有着重要的意义。设计并实现了一种基于欧拉角的关节活动度测量系统,系统利用光学定位设备获取标记点位置信息,通过旋转矩阵变换与欧拉角反解算法计算角度,实现了精确、实时的关节活动度测量。系统适用于人体颈部关节、腰部关节、肩关节、肘关节、腕关节、髋关节、膝关节以及踝关节的活动度测量。精度验证实验结果显示,系统的测量精度可达到0.3°。     

The relationship between electrical stimulus and joint torque: a dynamic model.

The knowledge of the behavior of electrically activated muscles is an important requisite for the development of functional electrical stimulation (FES) systems to restore mobility to persons with paralysis. The aim of this work was to develop a model capable of relating electrical parameters to dynamic joint torque for FES applications. The knee extensor muscles, stimulated using surface electrodes, were used for the experimental preparation. Both healthy subjects and people with paraplegia were tested. The dynamics of the lower limb were represented by a nonlinear second order model, which took account of the gravitational and inertial characteristics of the anatomical segments as well as the damping and stiffness properties of the knee joint. The viscous-elastic parameters of the system were identified experimentally through free pendular movements of the leg. Leg movements induced by quadriceps stimulation were acquired too, using a motion analysis system. Results showed that, for the considered experimental conditions, a simple one-pole transfer function is able to model the relationship between stimulus pulsewidth (PW) and active muscle torque. The time constant of the pole was found to depend on the stimulus pattern (ramp or step) while gain was directly dependent on stimulation frequency.     

The two-pole two-zero root locus

The author highlights the unity negative feedback root locus of a loop gain having two real poles lying along the real axis to the right of two real zeros. He demonstrates that the complex portion of the root locus (of the closed-loop negative feedback system) is a circle. He locates the center and computes the radius of the circle, and illuminates the stability of the closed-loop system     

Design and evaluation of a stance-control knee-ankle-foot orthosis knee joint.

Conventional knee-ankle-foot orthoses (KAFOs) are prescribed for people with knee-extensor muscle weakness. However, the orthoses lock the knee in full extension and, therefore, do not permit a natural gait pattern. A new electromechanical stance-control knee-ankle-foot orthosis (SCKAFO) knee joint that employs a novel friction-based belt-clamping mechanism was designed to enable a more natural gait. The SCKAFO knee joint allows free knee motion during swing and other non-weight-bearing activities and inhibits knee flexion while allowing knee extension during weight bearing. A prototype SCKAFO knee joint was mechanically tested to determine the moment at failure, loading behavior, and wear resistance. The mean maximum resisting moment of the SCKAFO knee joint over five loading trials was 69 Nm +/- 4.9 Nm. The SCKAFO knee-joint strength and performance were sufficient to allow testing on a 90 kg subject at normal walking cadence. Proper function of the new electromechanical knee joint was verified in walking trials of an able-bodied subject.     

Effect of initial joint position on nerve-cuff recordings of muscleafferents in rabbits

The objective was to characterize nerve-cuff recordings of muscle afferents to joint rotation over a large part of the physiological joint range. This information is needed to develop control strategies for functional electrical stimulation (FES) systems using muscle afferent signals for sensory feedback. Five acute rabbit experiments were performed. Tripolar cuff electrodes were implanted around the tibial and peroneal divisions of the sciatic nerve in the rabbit's left leg. The electroneurograms (ENG) were recorded during passive ankle rotation, using a ramp-and-hold profile starting at seven different joint positions (excursion=5°, velocity=10°/s, initial positions 60°, 70°, 80°, 90°, 100°, 110°, and 120°). The amplitude of the afferent activity was dependent on the initial joint position. The steady-state sensitivity of both nerve responses increased with increasing joint flexion, whereas the dynamic sensitivity increased initially but then decreased. The results indicate that recordings of the muscle afferents may provide reliable information over only a part of the physiological joint range, Despite this limitation, muscle afferent activity may be useful for motion feedback if the movement to be controlled is within a narrow joint range such as postural sway     

Proposed network structures and combined adaptive algorithms for electrocardiogram signal denoising

An electrocardiogram (ECG) signal is a record of the electrical activities of heart muscle and is used clinically to diagnose heart diseases. An ECG signal should be presented as clear as possible to support accurate decisions made by doctors. This article proposes different combinations of combined adaptive algorithms to derive different noise-cancelling structures to remove (denoise) different kinds of noise from ECG signals. The algorithms are applied to the following types of noise: power line interference, baseline wander, electrode motion artifact, and muscle artifacts. Moreover, the results of the suggested models and algorithms are compared with those of conventional denoising tools such as the discrete wavelet transform, an adaptive filter, and a multilayer neural network (NN) to ensure the superiority of the proposed combined structures and algorithms. Furthermore, the hybrid concept is based on dual, triple, and quadruple combinations of well-known algorithms that derive adaptive filters, such as the least mean squares, normalized least mean squares and recursive least squares algorithms. The combinations are formulated based on partial update, variable step-size (VSS), and second iterative VSS algorithms, which are considered in different combinations. In addition, biased NN and unbiased linear neural network (ULNN) structures are considered. The performance of the different structures and related algorithms are evaluated by measuring the post-signal-to-noise ratio, mean square error, and percentage root mean square difference.     

Simulation of a functional neuromuscular stimulation powered mechanical gait orthosis with coordinated joint locking.

The purpose of this study was to examine a hybrid orthosis system (HOS) for walking after spinal-cord injury (SCI) that coordinates the mechanical locking and unlocking of knee and ankle joints of a reciprocating gait orthosis (RGO), while propulsive forces are injected and unlocked joints controlled with functional neuromuscular stimulation (FNS). The likely effectiveness of the HOS in terms of forward progression, stability, and posture of paraplegic gait was determined in this simulation study. A three-dimensional computer model of a HOS combining FNS with an RGO incorporating feedback control of muscle activation and joint locking was developed. An anthropomorphic human model included passive joint moments and a foot-ground contact model adapted from other studies. A model of the RGO reciprocally coupled the hips and locked and unlocked the knee and ankle joints during stance and swing respectively. The actions of muscles under FNS activation were modeled via closed-loop control of joint torque inputs. A walking aid that mimicked canes and voluntary upper extremity actions maintained lateral stability by providing the necessary shoulder forces and moments. The simulated HOS achieved gait speeds of 0.51 +/- 0.03 m/s, stride lengths of 0.85 +/- 0.04 m, and cadences of 72 +/- 4 steps/min, exceeding the reported performance of other assistive gait systems. Although minimal forward trunk tilt was found to be necessary during specific phases of gait, posture, and stability were significantly improved over FNS-only systems.     

Dynamic simulation of FES-cycling: influence of individual parameters

Cycling by means of functional electrical simulation (FES) is an attractive training method for spinal cord injured (SCI) subjects. FES-cycling performance is influenced by a number of parameters like seating position, physiological parameters, conditions of surface stimulation, and pedaling rate. The objective of this paper was the determination of the influence of the most important parameters on optimal muscle stimulation patterns and power output of FES-cycling on a noncircular pedal path. The rider-cycle system was modeled as a planar articulated rigid body linkage on which the muscle forces are applied via joint moments and implemented into a forward dynamic simulation of FES-cycling. For model validation, the generated drive torques that are predicted by the simulation were compared to measurements with an individual paraplegic subject. Then, a sensitivity analysis was carried out to determine the influences of the most important parameters for surface stimulation of gluteus maximus, quadriceps, hamstrings, and peroneus reflex. The results show how optimal stimulation patterns and the expected mean active power output can be estimated based on measured individual parameters and adjusted geometry and stimulation parameters for a particular SCI-subject. This can considerably improve FES-cycling performance and relieve the patients by shortening the time that is necessary for experimental adaptation of the stimulation patterns.