Predictor-based compensation for electromechanical delay during neuromuscular electrical stimulation

Electromechanical delay (EMD) is a biological artifact that arises due to a time lag between electrical excitation and tension development in a muscle. EMD is known to cause degraded performance and instability during neuromuscular electrical stimulation (NMES). Compensating for such input delay is complicated by the unknown nonlinear muscle force-length and muscle force-velocity relationships. This paper provides control development and a mathematical stability analysis of a NMES controller with a predictive term that actively accounts for EMD. The results are obtained through the development of a novel predictor-type method to address the delay in the voltage input to the muscle. Lyapunov-Krasovskii functionals are used within a Lyapunov-based stability analysis to prove semi-global uniformly ultimately bounded tracking. Experiments on able-bodied volunteers illustrate the performance and robustness of the developed controller during a leg extension trajectory following task.     

Electronic design of a multichannel programmable implant for neuromuscular electrical stimulation.

An advanced stimulator for neuromuscular stimulation of spinal cord injured patients has been developed. The stimulator is externally controlled and powered by a single encoded radio frequency carrier and has four independently controlled bipolar stimulation channels. It offers a wide range of reprogrammability and flexibility, and can be used in many neuromuscular electrical stimulation applications. The implant system is adaptable to patient's needs and to future developments in stimulation algorithms by reprogramming the stimulator. The stimulator is capable of generating a wide range of stimulation waveforms and stimulation patterns and therefore is very suitable for selective nerve stimulation techniques. The reliability of the implant has been increased by using a forward error detection and correction communication protocol and by designing the chip for structural testability based on scan test approach. Implemented testability scheme makes it possible to verify the complete functionality of the implant before and after implantation. The stimulators architecture is designed to be modular and therefore its different blocks can be reused as standard building blocks in the design and implementation of other neuromuscular prostheses. Design for low-power techniques have also been employed to reduce power consumption of the electronic circuitry.     

Colon emptying induced by sequential electrical stimulation in rats.

Electrical stimulation could be used to induce colon emptying. The present experiments were performed to establish a stimulation pattern to optimize the stimulation parameters and to test neural involvement in propulsion induced by electrical stimulation. Colon segments were sequentially stimulated using rectangular pulses. The resulting propulsive activity displaced intraluminal content in consecutive propulsion steps. The propulsion steps differed in displacement latency, distance, and velocity along the stimulated colon. Increasing the pulse duration or amplitude resulted in a decrease of the latency. Increasing the stimulation amplitude doubled the displacement distance. The frequencies tested in the present study did not affect propulsion. Inhibition of cholinergic and nitrergic pathways inhibited propulsion. Electrical stimulation can induce colonic propulsion. Motor differences are present along the descending colon. The most suitable combination of pulse parameters regarding colon stimulation is 0.3 ms, 5 mA, 10 Hz. Neural circuits are involved in propulsion when using these values.     

Comparison of single- and two-channel neuromuscular electrical stimulation sites for enhancing venous return

Neuromuscular electrical stimulation (NMES) has previously been used to activate the musculature of the lower leg and increase venous return to the heart. However, there is little evidence to suggest the superiority of one particular stimulation site over another. In this paper, we aim to reveal the optimal stimulation site on the lower leg in a group of healthy adults. Doppler ultrasound measurements of venous blood volume expelled and peak venous velocity in response to various single and two-channel applications of NMES were taken for each subject. We found that soleus NMES is the most effective single-channel stimulation method, capable of expelling 58.3% of the blood achieved during a voluntary contraction, alternatively soleus plus tibialis posterior stimulation is capable of expelling 76.5%. Based on these and other factors we suggest that the soleus and soleus plus tibialis posterior are the most effective NMES sites for improving venous return.     

The effect of joint angle on the timing of muscle contractions elicited by neuromuscular electrical stimulation

Neuromuscular electrical stimulation was used to evoke isometric knee extension contractions in seven individuals with spinal cord injury (SCI) and the time for knee extension torque to rise and fall was measured across a range of knee angles. The stimulated muscles took more than twice as long to develop 50% of maximum torque at an angle of 15 degrees, compared to an angle of 90 degrees. This time difference comprised both an increased delay before torque rose above resting levels (31 +/- 3 ms at 90 degrees, 67 +/- 24 ms at 15 degrees), and a prolonged duration over which torque was rising (72 +/- 14 ms at 90 degrees, 140 +/- 62 ms at 15 degrees). There was no change, however, in the time taken for torque to fall after cessation of stimulation at different knee angles (58 +/- 5-ms delay, 60 +/- 11-ms fall time). The difference in torque rise time with joint angle has implications for modeling functional activities that differ greatly in their joint angles. This study provides regression equations whereby activation times for the quadriceps muscles of individuals with SCI can be predicted for specific angles of knee flexion.     

Development of a circuit for functional electrical stimulation

This paper examines the various design of a multiple-purpose portable functional electrical stimulator which is used in surface stimulation of paralyzed muscle of patients with stroke and results in limb activation. The functionality, circuit performance and reliability of the circuits will be examined. Analysis, design, and experimental results are presented.     

Cycling induced by electrical stimulation improves muscle activation and symmetry during pedaling in hemiparetic patients

A randomized controlled trial, involving 35 post-acute hemiparetic patients, demonstrated that a four-week treatment of cycling induced by functional electrical stimulation (FES-cycling) promotes motor recovery. Analyzing additional data acquired during that study, the present work investigated whether these improvements were associated to changes in muscle strength and motor coordination. Participants were randomized to receive FES-cycling or placebo FES-cycling. Clinical outcome measures were: the Motricity Index (MI), the gait speed, the electromyography activation of the rectus femoris and biceps femoris, and the mechanical work produced by each leg during voluntary pedaling. To provide a comparison with normal values, healthy adults also carried out the pedaling test. Patients were evaluated before, after training, and at follow-up visits. A significant treatment effect in favor of FES-treated patients was found in terms of MI scores and unbalance in mechanical works, while differences in gait speed were not significant (ANCOVA). Significant improvements in the activation of the paretic muscles were highlighted in the FES group, while no significant change was found in the placebo group (Friedman test). Our findings suggested that improvements in motor functions induced by FES-cycling training were associated with a more symmetrical involvement of the two legs and an improved motor coordination.     

How clean energy and efficiency can replace coal for a reliable,modern electricity grid

Aging coal-fired power plants are retiring all over the country, presenting the U.S. with an exciting opportunity to lead a global transition to a clean energy economy. The move away from coal begs the question: What will replace it? Energy efficiency, renewable energy and electric grid modernization should play an important part in replacing retiring coal capacity, and thereby mitigate the rush to build new natural gas plants.     

The energy efficiency of a high-voltage electrical drive for oil- and gas-industry compressor stations

The structure and volume of fuel- and energy-resource consumption in the gas industry show that the most energy is used in the process of long-distance gas transportation from gas-producing regions to the central industrial regions of Russia. Thus, the problem of reduction costs in the industry is primarily topical for long-distance pipelines—in particular for compressor stations, these being the main consumers of fuel and energy. Methods aiming at improving the energy efficiency of the compressor plants with centrifugal blowers using variable-frequency high-voltage electrical drives are considered in this article. Comparison and selection of the optimal structure for the power-circuit diagrams of the frequency converters are given. With the help of computer modeling, it is shown that a cascade multilevel frequency converter possesses better characteristics than do its analogues. The effect of the frequency converters on supply mains is considered. Comparison of different algorithms for control of cascade multilevel frequency converters is carried out on the basis of the computer model of the system. It is shown that the algorithm of the space modulation of the basic vectors is more applicable for providing the best energy characteristics of such a converter. A list of technical solutions aiming at improvement of the energy efficiency of a compressor station is constructed. The energyefficiency values of the applied technical solutions are calculated.     

Implanted functional electrical stimulation system for mobility in paraplegia: a follow-up case report.

A 16-channel functional electrical stimulation (FES) system has been implanted in a person with T10 paraplegia for over a year. The system consists of two eight-channel radio frequency controlled receiver-stimulators delivering stimuli through a network of 14 epimysial and two intramuscular electrodes. Using this system and a walker for support, the subject was able to stand up for 8 min and walk regularly for 20 m. The standing duration was limited by arm fatigue since upper extremities supported an average of 25% of body weight. This was due to suboptimal hip extension and some undesired recruitment of rectus femoris and sartorius with stimulation of quadriceps electrodes. The left quadriceps exhibited rapid fatigue that limited walking distance and duration. The metabolic energy requirements were well within the aerobic limits of the sedentary paraplegic population. At one-year follow-up evaluation all electrodes are functional except one intramuscular electrode. The implant caused no adverse physiological effects and the individual reported health benefits such as increased energy and overall fitness as a result of the FES system use. With further improvements in muscle response through innovative surgical techniques, the 16-channel implanted FES system can be a viable addition to exercise and mobility function in persons with paraplegia.     

Test bed with force-measuring crank for static and dynamicinvestigations on cycling by means of functional electrical stimulation

Cycling by means of functional electrical stimulation (FES) is an attractive training method for individuals with paraplegia. The physiological benefits of FES are combined with the psychological incentive of independent locomotion. In addition, cycling has the advantage in that the generated muscle forces are converted into drive power with relatively high efficiency compared to other means of locomotion, e.g., walking. For the design of an appropriate cycling device and the development of optimal stimulation patterns, it has to be investigated how the geometry for FES cycling, influenced by individual parameters of the FES-generated drive torques and the magnitude of variations among subjects with paraplegia, can be optimized. This study shows the design of a freely adjustable test bed with additional motor drive which allows static and dynamic measurements of force components and drive torque at the crank. Furthermore, the influence of geometry and various individual parameters on FES pedaling can be tested for each subject individually. A pedal path realized by a three-bar linkage that was optimized according to preliminary simulations further increases leg cycling efficiency. Safety precautions avoid injuries in case of excessive forces, e.g., spasms. Test results illustrate the application of the test bed and measurement routines. A test series with four paraplegic test persons showed that the presented static and dynamic measurement routines allow to provide optimal stimulation patterns for individual paraplegic subjects. While pedaling with these optimal stimulation patterns only negligible negative active drive torques, due to active muscle forces, were applied to the crank and sufficient drive power was generated to power a cycle independently     

Space charge trapping in electrical potential well caused by permanent and induced dipoles for LDPE/MgO nanocomposite

Space charge accumulation in low-density polyethylene film containing a small amount of MgO nanoparticles (LDPE/MgO nanocomposite film) subjected to an electric field greater than 100 kV/mm has been studied using an improved pulsed electroacoustic (PEA) system. No marked space charge accumulation was observed in LDPE/MgO nanocomposite films. To determine the mechanism of no space charge accumulation in the LDPE/MgO nanocomposite film, we compared electric potential wells produced by a permanent dipole moment such as that of carbonyl groups (C=0) and an induced dipole consisting of MgO nanoparticles (spherical dielectrics) under a high electric field to create a trapping site for electric charge carriers. The trapping depth created by the permanent dipole moment such as that of the carbonyl groups (C=0) of chemical defects is approximately 0.45 eV. However, the potential well induced by high-permittivity dielectric nanoparticles (MgO) is about 1.5 to 5.0 eV, which is much deeper than that induced by chemical defects. The suppression of space charge formation is explained using the potential well model consisting of a dipole induced by a high-permittivity dielectric nanoparticle. We explained the suppression mechanism of charge accumulation in the LDPE/MgO film that contains deep traps.     

Injection of a minimal space charge as mechanism for the initialphase of electrical polymer degradation

In this paper we present a model for polymer degradation during high-field stresses in analogy to the charge-to-breakdown concept in SiO ₂. The model is based on space charge injection under high fields which leads to a cumulative effect as in radiation damage. A critical total injected charge density Q_c is introduced, which is needed prior to any permanent damage. The assumption of a critical injection level explains the time and field dependence of the tree initiation time. The model is applied to electrical aging experiments in epoxy resins. It turns out that the critical charge for tree initiation is ~10 C/cm² similar to the value for trap creation in SiO₂ gate oxides     

Orbital solar power stations as a promising way for solving energy and environmental problems

The state of and prospects for development of space orbital solar power stations are considered. Known projects of orbital space solar power stations (SSPSs) and problems connected with their construction are reviewed. New conceptual solutions promising essential improvement of the technical and economic indicators of such stations are proposed.     

Minimum energy path search for a manipulator in consideration of all nonlinear characteristics by GA and its experiments

The dissipated energy even of a manipulator must be decreased in order to improve the environment of the earth. This paper describes an optimal path which minimizes the dissipated energy in PTP motions of a vertically articulated manipulator. The dynamic equation of the manipulator is nonlinear due to centrifugal, Coriolis, gravity, and Coulomb friction forces. Moreover the driving system of the joints is also nonlinear in that the generating torque is expressed by a third‐degree polynomial with respect to current. Therefore, an optimal path cannot be obtained by solving a two‐point boundary‐value problem analytically. In this paper an optimal path is searched for by a Genetic Algorithm (GA) in cases in which all kinds of nonlinear characteristics of the manipulator, including the driving system, are taken into consideration. The obtained optimal velocity functions are applied to a vertically articulated manipulator with two direct‐drive motors. The dissipated energy is measured by integrating the input power to the motors. Experimental results agree with the simulation values only when all kinds of nonlinearity are taken into consideration. © 2006 Wiley Periodicals, Inc. Electr Eng Jpn, 157(3): 26–34, 2006; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/eej.20437 Copyright © 2006 Wiley Periodicals, Inc.     

A study on collaborative operation method for a new energy type dispersed power supply system by AC‐EMAP model

Application of a dispersed power supply system consisting of a large‐scale photovoltaic system (PV), a fuel cell (FC), and an electric double layer capacitor (EDLC) is studied in this paper. This system is operated in autonomous mode, taking account of time delay characteristics of FC. The modified Euler type Moving Average Prediction (EMAP) model is improved using short‐time fast Fourier transform (ST‐FFT). The Adaptive Control type EMAP (AC‐EMAP) model is introduced to reduce the capacity of EDLC. This system can meet the multi‐quality electric power requirements of customers, and improve voltage stability and uninterruptible power supply (UPS) function as well. Moreover, the required capacity of EDLC to compensate the fluctuation of both PV output and Load demand is clarified by a simulation based on collaborative operation method by a prediction model using software MATLAB/Simulink. © 2006 Wiley Periodicals, Inc. Electr Eng Jpn, 156(1): 13–24, 2006; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/eej.20262     

Design support system for coloring illustrations by using the colors preferred by a user as determined from the hue patterns of illustrations prepared by that user

We propose a new design support system that can color illustrations according to a person's color preferences that are determined on the basis of the color patterns used by the same person in his previous work. Recently, many design tools for promoting free design have been developed. However, preferences for various colors differ depending on individual taste. Therefore, a system that can automatically color various designs on the basis of human preference is required. In this study, we propose an automatic modeling system that can be used to model illustrations. To verify the effectiveness of the proposed system, we simulate a coloring design experiment to determine the color patterns preferred by test subjects by using various design data. By using the design data, we determine each subject's preferred color pattern, and send feedback on these individual color patterns in the proposed system. © 2012 Wiley Periodicals, Inc. Electr Eng Jpn, 181(1): 19–27, 2012; Published online in Wiley Online Library (wileyonlinelibrary.com). DOI 10.1002/eej.21283     

Selection of injection conditions for aluminum particles as a raw material by numerical analysis in the synthesis of ultrafine particles with transferred type arc plasma

We investigated by numerical analysis the dependence of vaporization behavior of aluminum particles injected into transferred type arc plasma on injection conditions in synthesis of aluminum nitride ultra fine particles. On the basis of calculation results, we chose one proper injection condition where aluminum particles vaporized more. © 2009 Wiley Periodicals, Inc. Electr Eng Jpn, 170(2): 46–52, 2010; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/eej.20852     

Electrochemical properties of nanostructured Li[Fe0.9Mn0.1]PO4/C as a cathode material for lithium ion batteries prepared by electrospinning method

In this paper, Li[Fe_0.9Mn_0.1]PO₄/C nanofibers were successfully synthesized from a sol-gel precursor by electrospinning and used as a cathode material for lithium ion batteries. The synthesized nanofibers were smooth, and distributed uniformly, and when produced at 750 °C for 10 h in a nitrogen atmosphere had an average diameter of 100?~?300 nm. The crystal structures were studied by X-ray diffraction (XRD) and no obvious impurity-related peaks were observed. The electrochemical properties were examined using initial charge-discharge curve, cycle performance, EIS, etc. The initial discharge capacity reached about 124mAh/g. In addition, the impedance was lower than LiFePO₄.