Showing papers in "Electrical Engineering in Japan in 2012"

Driving torque control method for electric vehicle with in‐wheel motors

Abstract: Antislip control or slip ratio control can help improve the stability of EVs on a low-μ road. However, these control methods cannot control the driving torque. In this paper we propose a driving torque control method for EVs with in-wheel motors. By using this method we can control the driving torque directly. Simulations and experiments are carried out to demonstrate the effectiveness of the proposed method. © 2012 Wiley Periodicals, Inc. Electr Eng Jpn, 181(3): 49-58, 2012; Published online in Wiley Online Library (wileyonlinelibrary.com). DOI 10.1002/eej.21286

Influence of surface‐conductivity nonuniformity on charge accumulation of GIS downsized model spacer under DC field application

Abstract: When a DC voltage is applied to an insulating spacer, the electric field distribution around it is determined by the resistivity of the material. Consequently, charges are accumulated on the surface of the insulator, and its breakdown voltage may become low. In this paper, the charge density distribution of the insulator is measured. The measured data indicate that the surface conductance is the main factor in charge accumulation. Therefore, the conductivity of the insulator is also measured, and the influence of the surface conductivity on charge accumulation is examined both experimentally and by numerical computation. It is confirmed that nonuniformity of surface conductivity is responsible for charge accumulation and the conductivity of the insulator in atmospheric-pressure SF6 is estimated to be . © 2012 Wiley Periodicals, Inc. Electr Eng Jpn, 181(2): 29–36, 2012; Published online in Wiley Online Library (wileyonlinelibrary.com). DOI 10.1002/eej.22272

Train timetable evaluation from the viewpoint of passengers by microsimulation of train operation and passenger flow

Abstract: In order to evaluate train timetables from point of view of the passengers, it is indispensable to estimate the disutility of passengers This can be done by accurately estimating the movements of passengers and trains In particular, when there is a large number of passengers, the interactions between the passengers and trains must be considered To this end, we have developed a microsimulation system to simulate both train operation and passengers' train choice behavior The system can simulate the train choice behaviors of more than one million passengers as well as their positions in trains It is possible to estimate the delays caused by crowding in trains as well The system is based on models of different attitudes of the passengers with respect to the train choice behavior, which includes the choice of the earliest train, transfer avoidance, and avoiding crowding; a passenger's train choice behavior reflects his/her preferences We applied this system to an actual railway line in a metropolitan area and evaluated two train schedules by calculating the generalized cost, which reflects each passenger's disutility based on his/her experience Numerical experiments confirmed that the proposed method is very useful for evaluating timetables from the point of view of the passengers © 2012 Wiley Periodicals, Inc Electr Eng Jpn, 181(4): 51–62, 2012; Published online in Wiley Online Library (wileyonlinelibrarycom) DOI 101002/eej21264

Parameter optimization of model predictive control by PSO

Abstract: Among various control methods, model predictive control (MPC) is one of the major control strategies and has many successful applications. This paper presents an automatic tuning method for MPC using particle swarm optimization (PSO). One of the challenges in MPC is how control parameters can be tuned for various target plants, and the use of PSO for automatic tuning is one of the solutions. The MPC tuning problem is formulated as an optimization problem and PSO is applied as the optimization technique. PSO is one of the metaheuristic methods which are known to seek a global optimum at a relatively high ratio and with no use of a gradient. The numerical results for simple examples show the effectiveness of the proposed PSO-based automatic tuning method. © 2011 Wiley Periodicals, Inc. Electr Eng Jpn, 178(1): 40–49, 2012; Published online in Wiley Online Library (wileyonlinelibrary.com). DOI 10.1002/eej.21188

Route guidance by a car navigation system based on augmented reality

Abstract: Car navigation systems play a prominent role in road traffic safety and traffic regulation. However, it is necessary to improve the route guidance of car navigation systems so that they accurately and quickly recognize small differences in location. Thus, to increase the ease of understanding and safety of car navigation systems, navigation systems based on augmented reality have been proposed for providing guidance at road intersections. We are currently developing a car navigation system based on augmented reality, called AR-Navi. We investigated designs for the display of road intersection guidance that can be easily understood even when limited information is available and proposed a “best shot” display method that does not use moving images. In addition, we implemented a prototype system that includes these methods and conducted driving experiments on public roads to evaluate the ease of understanding and safety of AR-Navi. Using the evaluation results, we confirmed that the ease of understanding and safety is similar in the case of AR-Navi and CG-Navi. We also clarified the characteristics of AR-Navi. © 2012 Wiley Periodicals, Inc. Electr Eng Jpn, 180(2): 43–54, 2012; Published online in Wiley Online Library (wileyonlinelibrary.com). DOI 10.1002/eej.22278

Development of ionospheric tomography using neural network and its application to the 2007 Southern Sumatra earthquake

Abstract: An ionospheric anomaly prior to the 2007 Southern Sumatra earthquake (M8.5) was observed by GPS receivers around the Sumatra islands. In this paper, to investigate the three-dimensional structure of electron density in the ionosphere, a tomographic approach (Residual Minimization Training Neural Network; RMTNN) has been used. Results of the tomographic approach are consistent with those of the total electron content (TEC) approach. We found that a significant decrease of electron density takes place at altitudes of 250 to 400 km, especially at an altitude of 330 km. But the altitude at which the maximum electron density has been observed remains unchanged. The obtained structure has a region of decreased density of Integrated Electron Content (IEC) in the southwest area (at altitudes of 400 to 550 km) and in the northern area (at altitudes of 250 to 400 km). The global tendency of the decreased electron density expands to the east with higher altitudes and it is concentrated in the southern hemisphere over the epicenter. These results show that the high capability of the RMTNN method can be used for estimation of the ionospheric electron density distribution possibly associated with earthquake. © 2012 Wiley Periodicals, Inc. Electr Eng Jpn, 181(4): 9–18, 2012; Published online in Wiley Online Library (wileyonlinelibrary.com). DOI 10.1002/eej.22298

Spherical tokamak generation and merging on UTST using ex-vessel poloidal field coils only

Abstract: We successfully generated two spherical tokamaks (ST) at two null points by using ex-vessel poloidal field (PF) coils only and succeeded in merging them. This scheme is called a double null merging (DNM) scheme. First, two pairs of ex-vessel PF coils generate two null points where the poloidal field is zero at the upper and lower regions inside the vacuum vessel. Then a poloidal flux swing generates two STs at two null points, because the distance to the wall along the magnetic field is long at the null points. Finally, the coil currents push two STs toward the mid-plane and merge them into a single ST. Since a magnetic reconnection during merging transforms magnetic energy into thermal energy, this merged ST plasma is expected to have a high beta. It must be noted that the DNM scheme generates an ST without a center solenoid coil. The DNM scheme was demonstrated on the TS-3/4 (Japan) and MAST (UKAEA). However, these devices have all PF coils inside the vacuum vessels, and the initial plasmas were generated around the PF coils, not the null points. Since internal coils are not feasible in a fusion reactor due to high neutron flux, it is important to demonstrate the DNM scheme by using ex-vessel PF coils. © 2012 Wiley Periodicals, Inc. Electr Eng Jpn, 179(4): 18–24, 2012; Published online in Wiley Online Library (wileyonlinelibrary.com). DOI 10.1002/eej.21254

Decomposition of Methylene Blue in an Aqueous Solution Using a Pulsed-Discharge Plasma at Atmospheric Pressure

Abstract: The decomposition characteristics of methylene blue in an aqueous solution on exposure to a pulsed-discharge plasma generated above a water surface are investigated for different background-gas compositions (N2-O2 mixture and Ar-O2 mixture) and electrode configurations (1 needle and 55 needles). It is likely that OH radicals produced by reaction between H2O vapor and high-energy electrons in the pulsed plasma expanding on the water surface contribute to the decomposition of methylene blue. Further, O3 is found to contribute to methylene blue decomposition at high oxygen concentrations, and a slight contribution of OH radicals, produced by the reaction between N2 molecules excited in a metastable state [N2(A3)] and H2O vapor, is observed in pure N2. In a N2-O2 mixture, the O3 concentration decreases significantly and simultaneously NOx is produced by the pulsed plasma. Therefore, NOx probably destroys O3 and inhibits O3 generation. In an Ar-O2 mixture, a high decomposition rate of methylene blue is obtained regardless of the O3 concentration. It is likely that Ar atoms in metastable states, such as 3P2 and 3P0, contribute to the decomposition of methylene blue. A higher decomposition rate of methylene blue and a higher O3 concentration are observed when a streamer-like discharge is generated with 55 needle electrodes, than with a single needle electrode. © 2012 Wiley Periodicals, Inc. Electr Eng Jpn, 179(3): 1–9, 2012; Published online in Wiley Online Library (wileyonlinelibrary.com). DOI 10.1002/eej.21217

Electrical properties of heat-treated polylactic acid

Abstract: Polylactic acid (PLA), a biodegradable plastic, has excellent electrical insulation properties at temperatures ranging from room temperature to around 70 °C. At temperatures higher than 70 °C, however, the insulation performance of PLA deteriorates due to its poor heat resistance. In this study, PLA was heat-treated at 100 °C to endow it with greater heat resistance, and the effects of this heat treatment on the electrical properties of PLA were investigated. Before being subjected to heat treatment, the crystallinity (xc) of PLA was about 6%. After the heat treatment was begun, xc increased in proportion to the heat treatment time, such that measurements revealed that xc had increased to about 42% by 15 minutes after the start of the heat treatment. The temperature dependence of the insulation breakdown strength (EB) of heat-treated PLA was investigated, and it was found that EB of heat-treated PLA (PLA-A) decreases at a more moderate rate at temperatures above 60 °C. © 2012 Wiley Periodicals, Inc. Electr Eng Jpn, 180(1): 1–8, 2012; Published online in Wiley Online Library (wileyonlinelibrary.com). DOI 10.1002/eej.21272

Input power factor control of three-phase to three-phase matrix converters

Abstract: This paper presents input power factor control of three-phase to three-phase matrix converters. The authors propose three kinds of switching patterns for the matrix converters that can realize an arbitrary input-power-factor angle between 0 and 2π and reduce the number of commutations in all three phases to four during the control period. Also, the control range of the output voltage reference in the proposed control scheme is derived. The improvement of the input power factor by using the proposed control algorithm has been verified by experiments. © 2011 Wiley Periodicals, Inc. Electr Eng Jpn, 178(3): 42–52, 2012; Published online in Wiley Online Library (wileyonlinelibrary.com). DOI 10.1002/eej.21199

Numerical Simulation of Power Generation Characteristics of a Disk MHD Generator with High-Temperature Inert Gas Plasma

Abstract: The power generation characteristics of a disk magnetohydrodynamics (MHD) generator with high-temperature inert gas (argon) plasma have been examined by a time-dependent two-dimensional numerical simulation. The numerical simulation results based on the experimental conditions show that the enthalpy extraction ratio (= electrical output power/thermal input) can reach above 10%, which surely supports the reasonability of the experimental results. Proper selection of working conditions, especially the inlet total gas temperature, is necessary, since the gas temperature dominantly determines the electrical conductivity in the generator, unlike the conventional seeded plasma MHD generator. It is also found that the plasma is not in the recombination process but in the ionization process, where the ionization degree moderately increases along the flow. © 2012 Wiley Periodicals, Inc. Electr Eng Jpn, 179(3): 23–30, 2012; Published online in Wiley Online Library (wileyonlinelibrary.com). DOI 10.1002/eej.21237

Control Method for Harmonic Voltage Injection to Achieve Noise Reduction in Position‐Sensorless Control of Permanent‐Magnet Synchronous Motors at Low Speeds

Abstract: In this study, we examine the relationship between harmonic voltage injection, acoustic noise, and position estimation performance in a PMSM when a position-sensorless control method involving harmonic voltage injection is used at low speeds. Further, we propose a novel control method for voltage injection; this method can be used to reduce acoustic noise in the motor. The proposed control method is verified by performing numerical simulations and carrying out experiments using a four-pole, 2-kW, 2100-rpm IPMSM (interior permanent-magnet synchronous motor). © 2012 Wiley Periodicals, Inc. Electr Eng Jpn, 179(3): 49–56, 2012; Published online in Wiley Online Library (wileyonlinelibrary.com). DOI 10.1002/eej.21246

Evaluation of local residual stress distribution of stator core in a rotating machine

Abstract: It is well known that magnetic properties deteriorate in constructed cores due to conditions of stress such as riveting and welding during the manufacturing process, or punching and shearing during the cutting of the electrical steel sheets. Therefore, it is important to know the relationship between the stress and magnetic properties of electrical steel in order to design electrical machinery. In this paper, the local residual stress distribution on the cross section of the stator core in a rotating machine is measured with an X-ray stress measurement device. As a result, the difference in the residual stress distribution of each component is obtained in the teeth and core back of the stator core. In addition, we estimated the deterioration of the magnetic properties in the teeth region. We demonstrate that the magnetic properties of the electrical steel sheet deteriorated due to the residual stress. © 2012 Wiley Periodicals, Inc. Electr Eng Jpn, 181(3): 1–8, 2012; Published online in Wiley Online Library (wileyonlinelibrary.com). DOI 10.1002/eej.21271

Generation of uniform discharge by dielectric barrier discharge device in atmospheric-pressure air

Abstract: We found that the generation of a uniform discharge in atmospheric-pressure air was possible in the frequency range from 32 Hz to 1.1 kHz using alumina as a barrier material of the DBD (Dielectric Barrier Discharge) device. We also found that there is a voltage domain for the generation of the uniform discharge. The domain becomes wider with the increase of the frequency. If the applied voltage is slightly higher than the upper limit voltage of stable generation of a uniform discharge, the uniform discharge changes to a nonuniform FD (Filamentary Discharge). In order to clarify the mechanism of generation of the uniform discharge, we investigated how the barrier materials change the discharge mode by both photographic observation and analysis of electric circuit phenomena. We also carried out experiments with a DBD device, using a combination barrier of soda glass and alumina. In this case, the uniform discharge and the FD appeared alternately in every half cycle. As a result, it was found that a uniform discharge was generated when the alumina barrier was used and it acted as a cathode. From analysis of the gap voltage and the current, it was also found that the uniform discharge was an APTD (Atmospheric Pressure Townsend Discharge) characterized by electron avalanche. This paper presents the experimental results and discussions. © 2012 Wiley Periodicals, Inc. Electr Eng Jpn, 180(4): 1–9, 2012; Published online in Wiley Online Library (wileyonlinelibrary.com). DOI 10.1002/eej.21253

A study of centralized voltage profile control of distribution network considering dynamics of distributed generator

Abstract: In a future distribution network, it will be difficult to maintain system voltage because a large number of distributed generators are introduced into the system. The authors have previously proposed a voltage profile control method using power factor control of distributed generators. When all information on the system is available, an ideal stationary solution of control orders to distributed generators is given by an optimization calculation. However, it is difficult to apply optimization control in real time because a long calculation time is required for the optimization. Therefore, it is possible that a voltage change may occur before the power factor control has finished. Thus, in this paper, we develop a new control method which can save the excessive voltage changes by taking into consideration the controlled response time of distributed generators. The proposed method was tested in a 24-node distribution network model. © 2012 Wiley Periodicals, Inc. Electr Eng Jpn, 179(1): 29–39, 2012; Published online in Wiley Online Library (wileyonlinelibrary.com). DOI 10.1002/eej.21231

Three‐dimensional magnetostriction and vector magnetic properties under alternating magnetic flux conditions in arbitrary direction

Abstract: This paper presents the measured magnetostriction of electrical steel sheets under alternating magnetic flux conditions. In the measurements, we used a two-dimensional vector magnetic property measurement system, and a three-axial strain gauge. In order to know the magnetostriction in an arbitrary direction, the strain tensor was evaluated. In addition, we try to evaluate the magnetostrictions in the thickness direction. In this paper, the three-dimensional magnetostriction in nonoriented and grain-oriented silicon steel sheets are compared. © 2012 Wiley Periodicals, Inc. Electr Eng Jpn, 179(4): 1–9, 2012; Published online in Wiley Online Library (wileyonlinelibrary.com). DOI 10.1002/eej.21257

Feedback control of electromagnetic actuator with three degrees of freedom using optical image sensors

Abstract: Recently, multidimensional actuators have been attracting considerable interest as a solution for increases in size and weight. In this paper, we propose a position feedback control method using optical image sensors for an actuator with three degrees of freedom. The validity of this control method is verified on the basis of the measurement results. © 2012 Wiley Periodicals, Inc. Electr Eng Jpn, 181(2): 47–54, 2012; Published online in Wiley Online Library (wileyonlinelibrary.com). DOI 10.1002/eej.21290

Effect of polymer ablation gas on arc quenching properties around current zero

Abstract: The influence of polymer ablation on arc properties such as the temperature distribution and arc conductance in the current decay process was investigated by numerical approaches. A numerical thermofluid model was developed for a simplified circuit breaker with POM or PTFE ablation. In this model, thermal plasma-polymer solid coupling phenomena such as melting and evaporation were taken into account without any empirical model based on measurements, unlike other existing numerical thermofluid models. The dominant process for the decay of arc conductance was examined by changing the thermodynamic parameters such as the melting and boiling temperatures of solid polymers, or the thermal conductivity and electrical conductivity of the ablation gas. It was found that the gas density, thermal conductivity, and electrical conductivity of the ablation gas were more effective for decaying arc conductance than any other thermodynamic parameters. © 2012 Wiley Periodicals, Inc. Electr Eng Jpn, 180(3): 32–45, 2012; Published online in Wiley Online Library (wileyonlinelibrary.com). DOI 10.1002/eej.22274

A Shack–Hartmann laser wavefront sensor for measuring electron density in low-current arc

Abstract: A Shack-Hartmann type laser wavefront senor was developed for achieving electron density distributions over an arc channel in an extinguishing phase by only a single measurement with high temporal and spatial resolutions. The sensor was applied to pulsed arcs in 3-mm air gap between rod-to-rod tungsten electrodes with a diameter of 1mm. Electron densities in the arc discharges with currents of several tens of amperes were lower around the gap centre than near the anode and cathode. The behaviour of the electron densities was consistent with the intensity of emission light from arc discharges.

Method for bandwidth compression and transmission of environmental information in bilateral teleoperation

Abstract: In this paper, a novel method for bandwidth compression and transmission of environmental information is proposed for bilateral teleoperation systems with multiple degrees of freedom (MDOF). In this method, environmental information, that is, the position of end-effectors and the reaction force exerted on them, is converted into environmental modes by using discrete Fourier transform (DFT) matrices. The environmental modes to be transmitted are then selected on the basis of the communication bandwidth between master and slave robots. Bilateral control is achieved in low-frequency modal spaces, and local position control is achieved in high-frequency modal spaces. The validity of the proposed method is confirmed by performing an experiment. © 2011 Wiley Periodicals, Inc. Electr Eng Jpn, 178(2): 47–54, 2012; Published online in Wiley Online Library (wileyonlinelibrary.com). DOI 10.1002/eej.21206

A study of lightning current distribution at a wind turbine foot: Influence on current measurements using a Rogowski coil

Abstract: A Rogowski coil, used for measuring lightning current through a wind turbine generator system, is generally set up at the foot of a tower. In most wind turbines, there is an entrance at the foot of the tower, which leads to a flight of stairs or a ladder. When lightning strikes the wind turbine, the lightning current flows to the ground through the blades, nacelle, and tower. The current is shunted to the tower and the stairs/ladder at the foot of the tower, from where it may flow into the foundation and the earth. A Rogowski coil is usually set up at only the foot of a tower. The lightning current shunted to the stairs/ladder cannot be measured using the Rogowski. The installation position of the Rogowski coil depends on the construction of the stairs/ladder. In this study, the lightning current distribution at the foot of a tower is calculated using the FDTD (Finite Difference Time Domain) method, which is one of the methods used for numerical analyses of electromagnetic fields. We also studied the effect that the setup of the stairs/ladder and the resistivity of the ground have on the lightning current distribution. The results of the current distribution are very important for predicting the total current that flows through an existing wind turbine generator system. © 2012 Wiley Periodicals, Inc. Electr Eng Jpn, 180(4): 10–17, 2012; Published online in Wiley Online Library (wileyonlinelibrary.com). DOI 10.1002/eej.22273

Modeling of magnetization curves in nonoriented electrical steel sheets

Abstract: This paper discusses the modeling of magnetization curves in nonoriented electrical steel sheets. The initial curve and hysteresis loop below 0.15 T are approximately modeled by the Rayleigh model, and the Rayleigh loop constants are nearly proportional to the crystalline grain size. Hysteresis loops above 0.15 T in the magnetization rotation region are represented by the Preisach model, with consideration of the grain size distribution and the RD easy axis. Magnetization curves above 10 kA/m are calculated by the magnetization rotation model. However, magnetization curve modeling is necessary between the domain displacement model and the magnetization rotation regions. Magnetization curves in this region are modeled considering the field component , where B is the flux density and N is the order of the flux density and is equal to about 15. © 2012 Wiley Periodicals, Inc. Electr Eng Jpn, 180(3): 1–8, 2012; Published online in Wiley Online Library (wileyonlinelibrary.com). DOI 10.1002/eej.21296

Effect of ZrO2 addition on tolerance characteristics of the electrical degradation of ZnO varistors

Abstract: 3 ZnO varistors with excellent electrical degradation tolerance characteristics were made by addition of Bi2O3-MnO2-Co3O4-Cr2O3-SiO2-Sb2O3-NiO. The electrical degradation tolerance characteristics were evaluated by varying the amount of ZrO2. The evaluation methods were voltage–current (V–I) characteristics, X-ray diffraction (XRD), scanning electron microscope (SEM), and energy dispersion X-ray spectroscopy (EDX). Monoclinic and tetragonal ZrO2 and compounds derived from Zr were observed at both the grain boundaries and triple points. Moreover, the compounds derived from Zr with added Sb showed improved electrical degradation tolerance characteristics. On the other hand, monoclinic ZrO2 in particular degraded the electrical degradation tolerance characteristics. One factor in the improvement of the electrical degradation tolerance characteristics is that the mobility of oxide ions or interstitial Zn2+ ions might be hindered by the formation of compounds containing Zr, Sb, Si, and Bi atoms. The electrical degradation tolerance characteristics of ZnO varistors with added ZrO2 were better than those of varistors without addition of ZrO2 but subjected to heat treatment. © 2012 Wiley Periodicals, Inc. Electr Eng Jpn, 179(2): 11–19, 2012; Published online in Wiley Online Library (wileyonlinelibrary.com). DOI 10.1002/eej.21228

A Service Business Model for Saving Energy and Reduction of CO2 Emissions Using Inverters

Abstract: This paper considers the effectiveness of the service business approach for reducing CO2 emissions. “HDRIVE” is a service business using inverters to reduce the energy consumption of motor drive. The business model of this service is changed to find new opportunities of CO2 emission reduction by combining various factors such as financial services or long-term service contracts. Risk analysis of this business model is very important for providing stable services to users over the long term. The HDRIVE business model is found to be suitable for this objective. This service can be applied effectively to industries such as chemicals or steel, where CO2 emissions are very large, and has the possibility of creating new business considering CDM or trading CO2 emission rights. The effectiveness of this approach is demonstrated through several examples in real business. © 2012 Wiley Periodicals, Inc. Electr Eng Jpn, 179(3): 40–48, 2012; Published online in Wiley Online Library (wileyonlinelibrary.com). DOI 10.1002/eej.21242

Generation and control of electrolyte cathode atmospheric glow discharge using miniature gas flow

Abstract: Stable electrolyte cathode atmospheric DC glow microdischarges were generated by using a miniature helium gas flow from a nozzle electrode in air. We developed two schemes to control the temporal evolution of the discharge and the interaction between the discharge column and the ambient air. The vaporization of electrolyte solutions takes place and affects the discharge characteristics. This takes time from the start of the discharge. Therefore, the discharge was controlled by applying pulse-modulated DC voltages. If the voltage was dropped down to zero before the vaporization, the gas discharge developed without the ionization of the solution components. A helium gas discharge without air developed when the nozzle electrode was placed in a glass capillary. This was confirmed by examining the change in pH of the solution, which usually decreased owing to the generation of nitrogen oxides in the discharge in air. © 2011 Wiley Periodicals, Inc. Electr Eng Jpn, 178(4): 8–15, 2012; Published online in Wiley Online Library (wileyonlinelibrary.com). DOI 10.1002/eej.21222

A small‐size self‐propelled Stewart platform

Abstract: This paper describes a self-propelled Stewart platform. The Stewart platform usually consists of a base platform, a moving platform, and linear actuators connecting the platforms. We use six stacked-type piezoelectric actuators as linear actuators. Mechanical joints connected the linear actuators and both of the platforms. We inserted electromagnets between the linear actuators and the base platform instead of the mechanical joints. This structure enables the Stewart platform to move on a surface by using the principle of inchworm motion. While the electromagnets fix the linear actuators on the base platform, the proposed Stewart platform realizes a precise 6-DOF motion. Control signals are designed for small displacement based on inverse kinematics, and for a wide working area based on the principle of inchworm motion. The position and orientation of the moving platform are measured, and experimental results indicate the feasibility of the proposed mechanism. The mechanism is effective for a precise position system which has unlimited working space. © 2012 Wiley Periodicals, Inc. Electr Eng Jpn, 181(2): 37–46, 2012; Published online in Wiley Online Library (wileyonlinelibrary.com). DOI 10.1002/eej.21261

Investigation and improvement of torque response of control system based on direct torque control in interior permanent magnet synchronous motors

Abstract: In this study, we investigate the torque response of a control system that is based on the direct torque control (DTC) principle for an interior permanent magnet synchronous motor (IPMSM). We also propose a gain-scheduling method for improving the torque response. Reference flux vector calculation (RFVC) DTC is used in this study. In RFVC DTC, a PI controller is used for torque control; this is in contrast to the use of the hysteresis comparator and switching table in basic DTC. In this paper, we present the relationship between the torque response and the gain of the PI controller. This relationship is derived by using the transfer function of the torque control loop. We also examine the difference between the torque responses of two motors that have different machine parameters. The proposed method can be used to realize a torque response that is independent of the operating torque. The simulation results and experimental results presented in this paper show the validity of the derived relationship as well as the effectiveness of the proposed method. © 2012 Wiley Periodicals, Inc. Electr Eng Jpn, 181(2): 55–65, 2012; Published online in Wiley Online Library (wileyonlinelibrary.com). DOI 10.1002/eej.21198

Investigation of optimum applied voltage for water treatment by pulsed streamer discharge in air‐sprayed water droplets

Abstract: In this study, we investigated a water treatment method of spraying droplets of wastewater into a pulse discharge space. The water treatment was carried out by applying voltage with different pulse widths to determine the optimum pulse width, and the optimum pulse voltage determined on the basis of the results of the study was analyzed. The rise time of the voltages with pulse widths of 40, 60, and 80 ns was about 12, 19, and 32 ns, respectively, and the discharge current in the case of the faster rise time was higher. The number of streamer discharges is believed to increase with a decrease in the rise time. The energy efficiency in the case of the pulse width of 40 ns is higher than that in the case of the other pulse widths. This is because almost all of the active species are generated by early streamer discharge, and the longer discharging time at longer pulse widths increases the ineffectual energy by thermal loss. These results show that pulsed voltages with a faster rise time and shorter pulse width are optimum for the treatment. © 2012 Wiley Periodicals, Inc. Electr Eng Jpn, 180(2): 1–8, 2012; Published online in Wiley Online Library (wileyonlinelibrary.com). DOI 10.1002/eej.21273

Structure change of PTFE by low‐energy ion irradiation. Restraint of structure collapse by crosslinking structures

Abstract: The authors irradiated PTFE (polytetrafluoroethylene) with low-energy nitrogen ions (100 eV) for surface modification. However, PTFE cannot be expected to show improvement in adhesive strength because it is a degradation-prone polymer and surface fatigue is produced by ion irradiation. We focused on cross-linked structure to solve this problem. PTFE was changed from a degradation-prone polymer into a cross-linked polymer by raising the temperature above the glass-transition temperature during ion irradiation. As a result, the formation of CF3 bonds was inhibited and degradation was prevented by ion irradiation above the glass-transition temperature. In addition, combined consideration of the C1s spectrum and the density profile suggests that a cross-linked structure is effective for improvement of adhesive strength. © 2011 Wiley Periodicals, Inc. Electr Eng Jpn, 178(4): 1–7, 2012; Published online in Wiley Online Library (wileyonlinelibrary.com). DOI 10.1002/eej.21225

A multiagent-based cooperative voltage and reactive power control

Abstract: In order to maintain the system voltage within the optimal range and to prevent voltage instability phenomena before they occur, a variety of phase modifying equipment are installed in optimal locations throughout the power system network and a variety of methods of voltage reactive control are employed. The proposed system divides the traditional method of controlling voltage and reactive power into two subproblems: “voltage control” to adjust the secondary bus voltage of substations, and “reactive power control” to adjust the primary bus voltage. In this system, two types of agents are installed in substations in order to coordinate voltage control and reactive power control. In order to verify the performance of the proposed method, it was applied to a model network system. The results confirm that our proposed method is able to control violent fluctuations in load. © 2012 Wiley Periodicals, Inc. Electr Eng Jpn, 181(2): 20–28, 2012; Published online in Wiley Online Library (wileyonlinelibrary.com). DOI 10.1002/eej.22286