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.     

Recruitment and comfort of BION implanted electrical stimulation: implications for FES applications.

Restoration of motor function to paralyzed limbs by functional electrical stimulation (FES) has been hampered by the lack of precise and gradual control over muscle recruitment. A suitable interface should provide selective stimulation of individual muscles with graded recruitment of force. The BION was developed to enable neuromuscular stimulation through a miniature, self-contained implant designed to be injected in or near muscles and peripheral nerves. In this study, recruitment properties and comfort of the BION implanted electrical stimulation were systematically evaluated in subjects who participated in a clinical trial. Recruitment properties were qualitatively similar to other methods of implanted neuromuscular stimulation: thresholds and steepness of recruitment were negatively correlated and depended on stimulus charge (product of pulse current and duration). Perceived comfort was not affected by the choice of stimulus parameters, thus their choice can be based purely on technical considerations such as efficiency or resolution of recruitment.     

A reference model approach to performance monitoring of control loops with applications to irrigation channels

In this paper a new method for detection of oscillatory and sluggish controllers is developed. The method is aimed at control systems where rejection of measured load disturbances is the main control objective, and it is based on comparing the actual system output with the output of a reference model. A number of performance indicators are defined taking the most important factors from a control perspective into consideration. Based on the performance indicators, the performance of the control loops is evaluated. The developed method has been successfully applied to real data from an irrigation channel. The method correctly detected the control loops which needed retuning, and it provided useful information about several aspects of the control performance such as speed of response, oscillations and interactions between control loops. Copyright © 2005 John Wiley & Sons, Ltd.     

An EMG-to-force processing approach for determining ankle muscle forces during normal human gait.

Muscle forces move our limbs. These forces must be estimated with indirect techniques, as direct measurements are neither generally possible nor practical. An electromyography (EMG)-to-force processing technique was developed. Ankle joint moments and, by extension, ankle muscle forces were calculated. The ankle moment obtained by inverse dynamics was calculated for ten normal adults during free speed gait. There was close correlation between inverse dynamics ankle moments and moments determined by the EMG-to-force processing approach. Muscle forces were determined. The gait peak Achilles tendon force occurred in late single limb support. Peak force observed (2.9 kN) closely matched values obtained where force transducers were used to obtain in vivo muscle forces (2.6 kN). The EMG-to-force processing model presented here appears to be a practical means to determine in vivo muscle forces.     

Neurofuzzy adaptive controlling of selective stimulation for FES: a case study.

A controller was designed for the selective stimulation of the sciatic nerve with a multiple contact cuff electrode to generate a desired torque in the ankle joint of cat. The design integrates three approaches, artificial neural network (ANN) modeling, fuzzy logical adaptation, and geometrical mapping. The geometrical mapping refers to the vector transformation from the joint coordinates to the virtual muscle coordinates which have been conceptually developed to represent the major recruitment features of contact-based functional units in the physical plant. This method reduces the complexity of generating a data set for training the neural network in the feedforward path and implementing the on-line learning algorithm embedded in the feedback loop. The controller was evaluated by computer simulation with the experimental data obtained from the torque generation in five acute cats. The results show that the ANN-based feedforward is capable of predicting 65% of a given desired isometric torque, and the fuzzy logical machine is able to provide suitable gains for feedback modulation to reduce the error from 35 to 8.5% and produce a robust control.     

An effective approach to obtain model parameters for BJTS and FETSfrom data books

The authors address the problem of obtaining the values of small signal parameters of the high frequency hybrid-π models of bipolar junction transistors (BJTs) and junction FETs (JFETs) for a given set of bias conditions from the data-book values. They also show the methods of determining the 'typical' values of the input parameters to be used in the model statements of circuit simulators, such as SPICE     

An expectation-maximization-based interacting multiple model approach for cooperative driving systems

In this paper, we present a novel combined sensor registration and fusion approach for cooperative driving in intelligent transportation systems (ITSs). A realistic augmented registration and fusion-state space model in three dimensions is first developed for dissimilar sensors. In order to have unbiased sensor registration parameter estimates, the expectation-maximization (EM) algorithm is incorporated with the extended Kalman filter (EKF) to give simultaneous state and parameter estimates. Furthermore, the interacting multiple model (IMM) filter is introduced here for collaborative driving in order to deal with the jumping model problem occurred in different vehicles driving status. To evaluate the registration and fusion performance, a new recursive relationship is derived theoretically for computing the posterior Cramer-Rao bound (PCRB). It is shown by simulation that the proposed EM-IMM-EKF method has a more robust estimation performance than the conventional approach. The performance is furthermore verified by comparing the mean square error with the PCRB.     

An approach for determining the subsystem experiencing andproducing a bifurcation in a power system dynamic model

This paper presents a method for determining reduced-order subsystems called bifurcation subsystems, that experience bifurcation, and produce the bifurcation in the full power system dynamic model. The bifurcation subsystem is generally a subset of the center manifold subsystem. The bifurcation subsystem is in fact the singular perturbation determined slow subsystem within the center manifold dynamics that actually experiences and produces the bifurcation in the center manifold dynamics. The test procedure used to determine a bifurcation subsystem is described in this paper and does not require performing a nonlinear transformation required to determine the center manifold. The theory provides two singular perturbation based test conditions for existence of bifurcation subsystems. Examples that demonstrate the systematic use of this test procedure are presented for saddle-node and Hopf bifurcations in a single-machine-infinite-bus-model. Results when the test procedure for finding a bifurcation subsystem is applied to the large dominant elements of the tight eigenvector and the participation factor of a bifurcating eigenvalue are compared     

An approach to the semi-quantitative assessment model on human errors for decommissioning of nuclear facilities

This paper is to suggest the assessment model on human errors for decommissioning of nuclear facilities. On the basis of evaluation items, the structure of the model was systematically established and the method for the model was quantitatively designed. The categories of evaluation items consist of ‘psychological’, ‘physical’, ‘man-machine’, and ‘environmental’. The method is composed of scaling and weighting factors. Feasibility study of the method was accomplished by applying a scenario.     

A fuzzy clustering approach to a demand response model

This paper proposes a novel demand response model using a fuzzy subtractive cluster approach. The model development provides support to domestic consumer decisions on controllable loads management, considering consumers’ consumption needs and the appropriate load shape or rescheduling in order to achieve possible economic benefits. The model based on fuzzy subtractive clustering method considers clusters of domestic consumption covering an adequate consumption range. Analysis of different scenarios is presented considering available electric power and electric energy prices. Simulation results are presented and conclusions of the proposed demand response model are discussed.     

An electromagnetics course with EMC applications for computerengineering students

When computer engineering students follow a different (separate) program of study from the electrical engineering students, only a single course in engineering electromagnetics can be accommodated in the computer engineering (CE) core program. An outline for a course on electromagnetics for computer engineering is given combining traditional electromagnetics topics with definitions, concepts, and discussions drawn from EMC. In this way engineering electromagnetics is made relevant and vital for the CE student. Specific EMC topics are included as they arise in a presentation based on a standard engineering electromagnetics text. Shielding, radiated emissions, susceptibility, the electromagnetic environment, EMC test methods, open sites, shielded anechoic rooms, screen rooms, TEM cells, and EMC test antennas are discussed. The goal of the computer engineering electromagnetics course is to prepare the student for a full-scale EMC course to be taken as an elective in the final undergraduate year or the first year of graduate study     

An improved approach to application-specific power electronicseducation. Curriculum development

This paper presents an innovative power electronics curriculum spanning the undergraduate and graduate programs. The curriculum develops the basic concepts of the field and applies them to modern industrial challenges to solve practical problems. It is based on three fundamental disciplines: switching devices, circuits and topologies and control and drives. The curriculum, which will facilitate the development of optimal systems, bridges the gap between power semiconductor devices and circuit design. An underlying principle of the curriculum is the development of optimal application-specific power electronics systems, achieved primarily through optimization of power semiconductor devices. The curriculum is described in detail with an emphasis on the courses pertaining to power semiconductor device physics and converter circuit design. The role of advanced computer-aided design tools is also identified and shown to facilitate an application-specific device design and optimization methodology. To further illustrate the effectiveness of this approach, two industry-relevant course projects performed in the curriculum are presented in detail     

An enhanced time-frequency-spatial approach for motor imagery classification.

Human motor imagery (MI) tasks evoke electroencephalogram (EEG) signal changes. The features of these changes appear as subject-specific temporal traces of EEG rhythmic components at specific channels located over the scalp. Accurate classification of MI tasks based upon EEG may lead to a noninvasive brain-computer interface (BCI) to decode and convey intention of human subjects. We have previously proposed two novel methods on time-frequency feature extraction, expression and classification for high-density EEG recordings (Wang and He 2004; Wang, Deng, and He, 2004). In the present study, we refined the above time-frequency-spatial approach and applied it to a one-dimensional "cursor control" BCI experiment with online feedback. Through offline analysis of the collected data, we evaluated the capability of the present refined method in comparison with the original time-frequency-spatial methods. The enhanced performance in terms of classification accuracy was found for the proposed approach, with a mean accuracy rate of 91.1% for two subjects studied.     

An approach for transmission expansion planning using neurocomputing hybridized with a genetic algorithm

The aim of transmission expansion planning is to determine which right-of-way to use when constructing new lines in order to meet a forecasted load in the most economical way. This problem has been solved previously by mathematical sensitivity analysis (which finds a single nonoptimal solution). It is difficult to plan for economical and reliable expansion due to its discrete and combinatorial nature. Although another method that has efficiency for combinatorial problems is neurocomputing, this approach saves computational efforts but obtains poor solutions. The most desirable approach for this planning problem is one in which many good solutions are found in reasonable time, because planning experts will then be able to plan economical and reliable expansion according to these solutions. This paper presents an approach for solving transmission expansion planning based on neurocomputing hybridized with a genetic algorithm. This approach generates suitable initial states, which include past information, of neural networks utilizing genetic algorithm. Mingling neurocomputing and a genetic algorithm, the proposed approach can find many good solutions in reasonable time making full use of their merits. Computational examples show the effectiveness of the proposed approach by comparison with conventional approaches.     

变电站二次系统防雷保护初探

变电站二次设备的防雷保护是一个新的课题．其设计思想强调以电子信息系统为保护核心,为被保护设备构建一个均压等电位系统,并通过各级电涌保护器．逐级把雷电流泄放入大地。广东省广电集团有限公司汕尾供电分公司在对110kV汕尾变电站进行自动化改造的工程实践中．根据以上设计原则并结合实际情况对变电站二次设备防雷进行选型设计,提高了系统的运行安全性和可靠性。     

An apparatus for characterization and control of isolated muscle.

An apparatus for characterization and control of muscle tissue is presented. The apparatus is capable of providing generalized mechanical boundary conditions to muscle tissue, as well as implementing real-time feedback control via electrical stimulation. The system is intended to serve as an experimental platform for implementing a wide variety of muscle control and identification studies that will serve as fundamental investigations of muscle mechanics, energetics, functional electrical stimulation, and fatigue. In one illustration of the capabilities of the apparatus, pilot experimental results of muscle workloops against a finite-admittance passive load are presented, illustrating how richer boundary conditions may reveal interesting muscle behavior.     

An approach to design a high power piezoelectric ultrasonic transducer

Application of ultrasonic waves has been considerably progressed during the last decade and piezoelectric ceramics have had a common use as the driving source of such waves. However, there is not enough documented information on design and technology of manufacturing a high power ultrasonic transducer. In this paper, an attempt has been made to analyze the stress produced along the oscillating PZT employed ultrasonic head by applying the principles of acoustic wave propagation. Then, based on such analysis, general principles of PZT transducer design, excited by a DC-biased alternating electrical source, has been derived and finally a typical such transducer has been designed, manufactured and tested. By employing finite element modal analysis, the resonance frequency of the transducer was determined and compared with the experimental results. It was concluded that, the constitutive piezoelectric equations referred to in most sources and books are not valid for analyzing the acoustical dynamic stress in ultrasonic transducers. Instead, the analysis should be done with considering the dynamic behavior (elastic, damping and Inertia factors) of the problem.

A modified approach to transient stability enhancement with fast valving and braking resistor applications

Fast valving and braking resistor are two important members of the family of the discrete supplementary controllers (DISCOS). Both of these are very effective and economic means of transient stability enhancement under extreme contingencies. Being stationed at the similar end of a power system the two schemes carry a very good potential of an effective coordination. Such a coordinated control is helpful not only in obtaining an improved gain in stability, but also in overcoming the limitations and avoiding excessive duty on the part of an individual controller. In this work, a detailed study has been carried out to evaluate the scope and limitations of fast valving and dynamic braking resistor controls in enhancing the transient stability of power systems. Improvements have been suggested over the conventional schemes of control so as to improve their adaptability under different conditions of fault and loading or with different types of generating units.     

Equivalent optimization model for loss minimization: a suitableanalysis approach

Any OPF (optimal power flow) tool used in on-line minimum loss calculation requires an accurate representation of the external or unobservable parts of the network. This paper proposes an optimization model of both internal and external network represented explicitly. Although requiring only external network data, any available information about the external state may be used to improve its response. A general methodology for the performance analysis of equivalent OPF models is also proposed. On one level, the robustness of equivalent models for the production of accurate control actions in the internal system is analyzed. Accurate control actions are those that are as close as possible to the controls obtained through a hypothetical OPF solution of the complete system. On a second level, the capacity to react accurately, when such control actions are set in the internal system, is investigated. The proposed model and the Extended Ward equivalent have been tested through the presented methodology. The proposed model has been capable to take into account the information related to the optimization “status” (under optimization or not) of external system. This is an important information since it affects considerably the internal control action calculation. This information cannot be incorporated in the reduced equivalent models. Computational test results with the Brazilian South-Southeast 810 bus real system are presented