IEEE Transactions on Industrial Electronics

Volume 51, Number 2, April 2004 Access to the journal on IEEE XPLORE IE Transactions Home Page

Special Section Papers on Automotive Electronic Systems

51.2.1	F. Cuesta, F. Gomez-Bravo, A. Ollero, "Parking maneuvers of industrial-like electrical vehicles with and without trailer," IEEE Trans. on Industrial Electronics, vol. 51, no. 2, pp. 257- 269, April 2004. Abstract Link Full Text Abstract: Maneuvering autonomous vehicles in constrained environments is not a trivial task. This paper concentrates in the practical maneuvering of electrical vehicles. The autonomous vehicles considered in the paper, ROMEO-3R and ROMEO-4R, have been developed at the University of Seville, Seville, Spain, as the result of the adaptation of a tricycle and a car-like conventional electrical vehicles for transportation of people, respectively. Moreover, maneuvering of ROMEO-4R backing up a trailer has also been considered. A particular maneuver, namely, autonomous parallel parking, has been used to illustrate the application of the presented methods to different electrical vehicles.
51.2.2	R. Daily, D.M. Bevly, "The use of GPS for vehicle stability control systems," IEEE Trans. on Industrial Electronics, vol. 51, no. 2, pp. 270- 277, April 2004. Abstract Link Full Text Abstract: This paper presents a method for using global positioning system (GPS) velocity measurements to improve vehicle lateral stability control systems. GPS can be used to calculate the sideslip angle of a vehicle without knowing the vehicle model. This measurement is combined with other traditional measurements to control the lateral motion of the vehicle. Noise estimates are provided for all measurement systems to allow the sensors to be accurately represented. Additionally, a method to calculate the lateral forces at the tires is presented. It is shown that the tire estimation algorithm performs well outside the linear region of the tire. Results for the controller and force calculations are shown using a nonlinear model to simulate the vehicle and the force calculations are validated with experimental measurements on a test vehicle.
51.2.3	J. Stephant, A. Charara, D. Meizel, "Virtual sensor: application to vehicle sideslip angle and transversal forces," IEEE Trans. on Industrial Electronics, vol. 51, no. 2, pp. 278- 289, April 2004. Abstract Link Full Text Abstract: This paper compares four observers (virtual sensors) of vehicle sideslip angle and lateral forces. The first is linear and uses a linear vehicle model. The remaining observers use an extended nonlinear model. The three nonlinear observers are: extended Luenberger observer, extended Kalman filter and sliding-mode observer. Modeling, model simplification, and observers are described, and an observability analysis is performed for the entire vehicle trajectory. The paper also deals with three different sets of sensors to see the impact of observers results. Comparison is first done by simulation on a valid vehicle simulator, and then observers are used on experimental data. Our study shows that observers are more accurate than simple models as regards unmeasurable variables such as sideslip angle and transversal forces. It also shows that speed of center of gravity is not an indispensable variable here.
51.2.4	M. Parmar, J.Y. Hung, "A sensorless optimal control system for an automotive electric power assist steering system," IEEE Trans. on Industrial Electronics, vol. 51, no. 2, pp. 290- 298, April 2004. Abstract Link Full Text Abstract: This paper considers the analysis and design of a double-pinion-type electric power assist steering (EPAS) control system. A simplified model of the augmented steering assembly-electric motor system is developed using Lagrangian dynamics, and an optimal controller structure for the model is proposed. Three main advances to the state of the art are presented in this paper. First, a state-space design model is used rather than an input-output model. A state-space formulation for a system model that incorporates motor electrical dynamics is obtained with the assist motor angular position as the output. Second, linear quadratic regulator (LQR) and Kalman filter techniques are employed to arrive at an optimal controller for the EPAS system. The selection of weighting coefficients for the LQR cost function is discussed. Finally, the authors present a control strategy that eliminates the steering column torque sensor, a critical component in existing EPAS controller designs. The proposed control strategy presents an opportunity to improve EPAS system performance and also reduce system cost and complexity.
51.2.5	M. Montanari, F. Ronchi, C. Rossi, A. Tonielli, "Control of a camless engine electromechanical actuator: position reconstruction and dynamic performance analysis," IEEE Trans. on Industrial Electronics, vol. 51, no. 2, pp. 299- 311, April 2004. Abstract Link Full Text Abstract: Camless internal combustion engines offer major improvements over traditional engines in terms of efficiency, maximum torque and power, and pollutant emissions. Electromechanical valve actuators are very promising in this context, but they present significant control problems. Further, to keep system cost at an acceptable level, a control system without a valve position sensor needs to be adopted. Low valve seating velocity, small transition time for valve opening and closing, and unavailability of position sensor are conflicting objectives that need to be jointly considered. In this paper, a control system architecture is presented, capable of dealing with all these issues. It is shown that a position tracking controller is needed: a key point is the design of the reference trajectory to be tracked. Actuator physical limitations strongly influence the feasible trajectory when low valve seating velocity is required, thus affecting valve transition time. Owing to the same limitations, valve electromagnets have to be energized for a significant part of the trajectory, thus allowing valve position reconstruction starting from electrical measurements only. A method for position reconstruction is presented, which makes use of auxiliary coils to reconstruct electromagnets fluxes; it is shown via sensitivity analysis that the functional characteristics of position reconstruction and its accuracy are compatible with the required applications. The trajectory design is then addressed as an optimization problem that explicitly considers the tradeoff between fast dynamic performance and system robustness. The solution of this optimization problem enlightens the limitations on achievable dynamic performance, which are presented and discussed.
51.2.6	Junha Kim, Jinhwan Jung, Kwanghee Nam, "Dual-inverter control strategy for high-speed operation of EV induction motors," IEEE Trans. on Industrial Electronics, vol. 51, no. 2, pp. 312- 320, April 2004. Abstract Link Full Text Abstract: An integrated starter/alternator (ISA) is normally designed to have high pole structure (10-14 poles) for high starting torque. However, its back electromotive force (EMF) at the peak revolutions per minute should be less than its battery voltage for the power flow control. For example, the back-EMF of a 12-pole ISA should be 42 V at 6000 r/min. These types of conflicting requirements lead to a nonclassical motor design that has extremely large field-weakening range (8:1/spl sim/10:1). In this paper, we are considering the use of an induction machine instead of a permanent synchronous machine. As an idea for solving the voltage limit problem, two inverters are utilized with an objective of sharing the required voltage. The secondary inverter only takes care of the reactive voltage component that grows very fast in high-speed operation. Therefore, an extra voltage source is not required for the secondary inverter. Only a capacitor bank suffices for the secondary inverter.
51.2.7	W.G. Koellner, G.M. Brown, J. Rodriguez, J. Pontt, P. Cortes, H. Miranda, "Recent advances in mining haul trucks," IEEE Trans. on Industrial Electronics, vol. 51, no. 2, pp. 321- 329, April 2004. Abstract Link Full Text Abstract: Electric mining haul trucks are one of the most challenging applications of power electronics in automotive systems. This paper presents some advances in very-high-power trucks used in copper mines. The special operational and environmental requirements for this application are highlighted. It is established that the use of inverter-fed three-phase induction motors with vector control is the preferred solution to reach the required high starting torque and good dynamic performance required by these vehicles. Packaging is a key issue and special attention is dedicated to the forced-air cooling system, because the air has a high dust level including conductive and corrosive materials. The truck's high-performance electric retarding system is described along with a novel use of trolley lines in a diesel boost mode as a way to increase the power and speed of the truck and reduce fuel consumption. Advanced features like remote monitoring, the use of global positioning systems and Internet diagnostics and troubleshooting are also discussed. The paper clearly shows that modern electric haul trucks are highly sophisticated systems that make full use of advances in modern technologies to increase safety and productivity levels. Drive Control
51.2.8	Ching-Chih Tsai, Chih-Hung Huang, "Model reference adaptive predictive control for a variable-frequency oil-cooling machine," IEEE Trans. on Industrial Electronics, vol. 51, no. 2, pp. 330- 339, April 2004. Abstract Link Full Text Abstract: This paper develops methodologies and techniques for the design, analysis, and implementation of a model reference adaptive predictive temperature controller for a variable-frequency oil-cooling machine, suited for cooling high-speed machine tools. The oil-cooling process is modeled experimentally as a first-order system model with a time delay and its system parameters are identified using the recursive least-square method. Based on this model, a model reference adaptive predictive controller is proposed for achieving set-point tracking and robustness. A real-time model reference adaptive predictive control algorithm is then presented and implemented utilizing a stand-alone digital signal processor TMS320F243 from Texas Instruments Incorporated. The experimental results show that the proposed control method is proven capable of giving satisfactory performance under set-point changes, fixed loads, and load changes.
51.2.9	A.G. Loukianov, J.M. Canedo, V.I. Utkin, J. Cabrera-Vazquez, "Discontinuous controller for power systems: sliding-mode block control approach," IEEE Trans. on Industrial Electronics, vol. 51, no. 2, pp. 340- 353, April 2004. Abstract Link Full Text Abstract: Based on the complete model of the plant, a sliding-mode stabilizing controller for synchronous generators is designed. The block control approach is used in order to derive a nonlinear sliding surface, on which the mechanical dynamics are linearized. This combined approach enables us to compensate the inherent nonlinearities of the generator and to reject high-level external disturbances. A nonlinear observer is designed for estimation of the rotor fluxes and mechanical torque.
51.2.10	N. Bonnail, D. Tonneau, F. Febdard, G.-A. Capolino, H. Dallaporta, "Variable structure control of a piezoelectric actuator for a scanning tunneling microscope," IEEE Trans. on Industrial Electronics, vol. 51, no. 2, pp. 354- 363, April 2004. Abstract Link Full Text Abstract: Scanning probe microscopes are now widely used in the field of material science and engineering for surface imaging at atomic scale. Their principle is based on the surface probing by a sharp tip approached at a nanometric distance of the surface. The probe is fixed to piezoelectric actuators allowing its displacement above the surface. An electronic command of a scanning tunneling microscope (STM) has been designed and tested. The regulation feedback loop of the tunnel current includes an integral controller, as is the case in commercial equipment. An extra control by variable-structure system has been implemented on this electronic command. Its principle is based on the commutation of the feedback sign. The effect on the system performance of the variable structure control is presented and discussed. An STM head has been modeled and all the model parameters have been determined. The model has been validated by comparison of the experimental and simulated responses of the system under excitation.
51.2.11	A. Damiano, G.L. Gatto, I. Marongiu, A. Pisano, "Second-order sliding-mode control of DC drives," IEEE Trans. on Industrial Electronics, vol. 51, no. 2, pp. 364- 373, April 2004. Abstract Link Full Text Abstract: One of the most recent topics in variable-structure systems theory is represented by the second-order sliding-mode control (2-SMC) methodology. This approach guarantees the same robustness and dynamic performance of traditional first-order SMC algorithms, and, at the same time, attenuates the chattering phenomenon, which is the main drawback in the actual implementation of this technique. In the present paper, a recently-proposed 2-SMC algorithm is used to synthesize a robust dc-drive control system which does not require current feedback and demands only rough information about the actual motor parameters. Stability and performance are analyzed, and an experimental comparison with a proportional-integral-based control scheme is reported.
51.2.12	Jin-Woo Ahn, Sung-Jun Park, Dong-Hee Lee, "Hybrid excitation of SRM for reduction of vibration and acoustic noise," IEEE Trans. on Industrial Electronics, vol. 51, no. 2, pp. 374- 380, April 2004. Abstract Link Full Text Abstract: The inherent simplicity, ruggedness, and low cost of a switched reluctance motor (SRM) makes it a viable candidate for various general-purpose adjustable-speed applications such as industrial and home appliances. The primary disadvantage of an SRM is the vibration and acoustic noise compared with that of conventional machines. The main source of vibration in the SR drive is generated by rapid change of radial magnetic force when phase current is extinguished during commutation action. In this paper, a hybrid excitation method with C-dump inverter is proposed to reduce vibration and acoustic noise in the SR drive. The hybrid excitation has two-phase excitation by long dwell angle as well as conventional one-phase excitation. The vibration and acoustic noise are reduced because the scheme reduces abrupt change of excitation level by distributed and balanced excitation.
51.2.13	Chunxiang Wang, Yongzhang Wang, Ruqing Yang, Hua Lu, "Research on precision tension control system based on neural network," IEEE Trans. on Industrial Electronics, vol. 51, no. 2, pp. 381- 386, April 2004. Abstract Link Full Text Abstract: In this paper, the closed-loop tension control system, with industrial control computer as the core, direct current torque motor as the actuator, equipped with tension sensor of real-time feedback filament tension change, is researched and manufactured. The theory of a neural network is applied on the system, and this method overcame the shortcomings of the traditional proportional-integral-derivative control method, and effectively weakened the coupling action between the velocity and tension of the tension control system. Some simulation results indicated the favorable effect of the control algorithm.
51.2.14	P. Baranyi, "TP model transformation as a way to LMI-based controller design," IEEE Trans. on Industrial Electronics, vol. 51, no. 2, pp. 387- 400, April 2004. Abstract Link Full Text Abstract: The main objective of this paper is to propose a numerical controller design methodology. This methodology has two steps. In the first step, tensor product (TP) model transformation is applied, which is capable of transforming a dynamic system model, given over a bounded domain, into TP model form, including polytopic or Takagi-Sugeno model forms. Then, in the second step, Lyapunov's controller design theorems are utilized in the form of linear matrix inequalities (LMIs). The main novelty of this paper is the development of the TP model transformation of the first step. It does not merely transform to TP model form, but it automatically prepares the transformed model to all the specific conditions required by the LMI design. The LMI design can, hence, be immediately executed on the result of the TP model transformation. The secondary objective of this paper is to discuss that representing a dynamic model in TP model form needs to consider the tradeoff between the modeling accuracy and computational complexity. Having a controller with low computational cost is highly desired in many cases of real implementations. The proposed TP model transformation is developed and specialized for finding a complexity minimized model according to a given modeling accuracy. Detailed control design examples are given. Power Electronics
51.2.15	G. Escobar, A.M. Stankovic, P. Mattavelli, "An adaptive controller in stationary reference frame for D-statcom in unbalanced operation," IEEE Trans. on Industrial Electronics, vol. 51, no. 2, pp. 401- 409, April 2004. Abstract Link Full Text Abstract: This paper presents a passivity-based controller for a Distribution Static synchronous Compensator (D-Statcom) aimed at compensating reactive power and unbalanced harmonics in the general case of distorted and unbalanced source voltages and load currents. The proposed approach is based on the measurements of line currents, and ensures precise compensation for selected harmonics. Moreover, in order to compensate for the unavoidable uncertainty in certain system parameters, adaptation is added to the passivity-based controller. One of the major advantages of the proposed solution compared to conventional alternatives is that we are able to perform precise tracking (including higher order harmonics) even in the presence of a relatively low switching frequency, i.e., in the presence of an inverter with limited bandwidth. Simulation and experimental results are provided to illustrate the merits of our solution.
51.2.16	K.K. Tse, B.M.T. Ho, H.S.-H. Chung, S.Y.R. Hui, "A comparative study of maximum-power-point trackers for photovoltaic panels using switching-frequency modulation scheme," IEEE Trans. on Industrial Electronics, vol. 51, no. 2, pp. 410- 418, April 2004. Abstract Link Full Text Abstract: A comparative study of the maximum power point trackers using a switching-frequency modulation scheme (SFMS) for photovoltaic panels is presented. Some commonly used dc/dc converters, which are applied for the power conversion stage of those trackers, will be examined. Method of locating the maximum power point (MPP) is based on injecting a small-signal sinusoidal perturbation into the switching frequency of the converter and comparing the ac component and the average value of the panel's terminal voltage. Apart from not requiring sophisticated computation of the panel power, this SFMS does not approximate the panel characteristics and can globally locate the MPP under wide insolation conditions. Tracking capability of the converters under investigation will be compared, using a 10-W solar panel with a controlled experimental setup. Theoretical predictions will be verified with experimental results. Operating characteristics at steady state and in large-signal change of the insolation (incident solar radiation) level will be studied.
51.2.17	M. Lopez, L.G. de Vicuna, M. Castilla, P. Gaya, O. Lopez, "Current distribution control design for paralleled DC/DC converters using sliding-mode control," IEEE Trans. on Industrial Electronics, vol. 51, no. 2, pp. 419- 428, April 2004. Abstract Link Full Text Abstract: This paper shows the analysis and design of a parallel-connected converter system using sliding mode control techniques. The design is particularised for a system that consists of N boost converters and a current feedback loop based on a proportional-integral compensator of the output voltage error. The paper emphasises the advantages of the sliding-mode control over the classic design method based on small-signal models, thus providing an effective and robust means of controlling nonlinear multi-input converters. The design is based on the Utkin conditions, which permit us to know the regions under which a sliding mode exists. This fact allows us to design the compensator and to introduce some modifications in the control loop that avoids input-current overshoots during the system startup. Simple design expressions are obtained and verified with simulation and experimental results, thus showing the improvements achieved with the proposed modifications.
51.2.18	H.Y. Kanaan, H. Fortin-Blanchette, K. Al-Haddad, R. Chaffai, L. Duguay, F. Fnaiech, "Linear control design for a current-injection-based three-phase unity-power-factor rectifier," IEEE Trans. on Industrial Electronics, vol. 51, no. 2, pp. 429- 438, April 2004. Abstract Link Full Text Abstract: In this paper, a new control strategy based on the pulsewidth-modulation technique is proposed and applied to an active-current-injection-based unity-power-factor three-phase ac-dc converter. The control circuit of the converter consists of a multivariable inner current regulator and an outer voltage regulator. Based on linear control techniques, the control circuit has been designed. Averaging techniques are used to derive a linear small-signal model of the converter in the frequency domain. Numerical simulations using the Power System Blockset tool of Matlab/Simulink highlight the performance of the proposed control scheme. Experimental results obtained on a 2-kW prototype validate the theoretical approach described in the paper.
51.2.19	R.L. de Araujo Ribeiro, C.B. Jacobina, E.R.C. da Silva, A.M.N. Lima, "Fault-tolerant voltage-fed PWM inverter AC motor drive systems," IEEE Trans. on Industrial Electronics, vol. 51, no. 2, pp. 439- 446, April 2004. Abstract Link Full Text Abstract: This paper shows how to integrate fault compensation strategies into two different types of configurations of induction motor drive systems. The proposed strategies provide compensation for open-circuit and short-circuit failures occurring in the converter power devices. The fault compensation is achieved by reconfiguring the power converter topology with the help of isolating and connecting devices. These devices are used to redefine the post-fault converter topology. This allows for continuous free operation of the drive after isolation of the faulty power switches in the converter. Experimental results demonstrate the validity of the proposed systems.
51.2.20	M. Malinowski, M. Jasinski, M.P. Kazmierkowski, "Simple direct power control of three-phase PWM rectifier using space-vector modulation (DPC-SVM)," IEEE Trans. on Industrial Electronics, vol. 51, no. 2, pp. 447- 454, April 2004. Abstract Link Full Text Abstract: This paper proposes a novel and simple direct power control of three-phase pulsewidth-modulated (PWM) rectifiers with constant switching frequency using space-vector modulation (DPC-SVM). The active and reactive powers are used as the pulse width modulated (PWM) control variables instead of the three-phase line currents being used. Moreover, line voltage sensors are replaced by a virtual flux estimator. The theoretical principle of this method is discussed. The steady-state and dynamic results of DPC-SVM that illustrate the operation and performance of the proposed system are presented. It is shown that DPC-SVM exhibits several features, such as a simple algorithm, good dynamic response, constant switching frequency, and particularly it provides sinusoidal line current when supply voltage is not ideal. Results have proven excellent performance and verify the validity of the proposed system.
51.2.21	Chongming Qiao, Taotao Jin, K.M. Smedley, "One-cycle control of three-phase active power filter with vector operation," IEEE Trans. on Industrial Electronics, vol. 51, no. 2, pp. 455- 463, April 2004. Abstract Link Full Text Abstract: Active power filters (APFs) provides an effective measure to eliminate the power line harmonic/reactive currents generated by nonlinear loads or by distributed energy sources that are connected to the grid. Active power filters are typically connected in parallel to the harmonic/reactive current sources and cancel the harmonic/reactive components in the line current so that the current flow into and from the grid is sinusoidal and in phase with the grid voltage. Since the APFs process only the harmonic/reactive power, their power-handling capability can be much higher than that of the cascade power-factor-correction methods. In this paper, the one-cycle control method is extended to control three-phase APFs. The proposed control approach employs one integrator with reset along with several logic and linear components to control a voltage-source converter to achieve three-phase unity power factor for the current to and from the power grid. No multipliers or sensors for the load current and the APF inductor current are required. Furthermore, there is no need to calculate the reference for controlling APF inductor current so that complicated digital computation is eliminated. The operation switching frequency is constant that is desirable for industrial applications. The proposed control approach features great simplicity, excellent harmonic/reactive current cancellation, and solid stability. It is a cost-effective solution for power quality control for electronic equipment, buildings, industrial facilities, ships, airplanes, distributed power generation stations, etc. All findings are supported by experimental results. Emerging Technology
51.2.22	K.F. Leung, F.H.F. Leung, H.K. Lam, S.H. Ling, "On interpretation of graffiti digits and characters for eBooks: neural-fuzzy network and genetic algorithm approach," IEEE Trans. on Industrial Electronics, vol. 51, no. 2, pp. 464- 471, April 2004. Abstract Link Full Text Abstract: This paper presents the rule optimization, tuning of the membership functions, and optimization of the number of fuzzy rules, of a neural-fuzzy network (NFN) using a genetic algorithm (GA). The objectives are achieved by training a proposed NFN with rule switches. The proposed NFN and GA are employed to interpret graffiti number inputs and commands for electronic books (eBooks).
51.2.23	Chin Tsu Yen, Wan-de Weng, Yen Tsun Lin, "FPGA realization of a neural-network-based nonlinear channel equalizer," IEEE Trans. on Industrial Electronics, vol. 51, no. 2, pp. 472- 479, April 2004. Abstract Link Full Text Abstract: The software simulation as well as the hardware implementation of equalizers for transmissions through nonlinear communication channels based on artificial neural networks structure is presented in this paper. We consider four-quadrature-amplitude-modulation technique as an example and compare the performance of two different structures of equalizer, namely, the linear least-mean-square-based equalizer (LIN) and the functional link artificial neural networks (FLANN). The learning curve and symbol error rate for the two structures are respectively evaluated by computer simulation. Besides, the systems have been implemented using field-programmable-gate-array devices. As FLANN uses functions to expand the dimensionality of the input signals, it has about the same system complexity as LIN. But FLANN can achieve fast processing speed under parallel processing structure. Simulation results have demonstrated that FLANN presents much better error performance than LIN, especially when the communication channel is highly nonlinear. Robotics and Vision
51.2.24	G. Ginesu, D.D. Giusto, V. Margner, P. Meinlschmidt, "Detection of foreign bodies in food by thermal image processing," IEEE Trans. on Industrial Electronics, vol. 51, no. 2, pp. 480- 490, April 2004. Abstract Link Full Text Abstract: This paper deals with the problem of detection of foreign bodies in food. A new method for inspecting food samples is presented, using thermographic images to detect foreign bodies that are not detectable using conventional methods. At first, the basic background of thermography is given. Then, experiments to obtain well-contrasted thermographic images of different food and foreign bodies are discussed. The main part of the present paper introduces specific image processing methods that show a good recognition power of foreign bodies within food. Results achieved with a small set of test images are presented. The results are promising and the methods work even on some poorly contrasted images. To compare the different image processing and recognition methods, a quality index is defined. On the test images the success of the presented methods is shown and the difference in recognition results can be measured using the introduced quality index.
51.2.25	D. Bi, Y.F. Li, S.K. Tso, G.L. Wang, "Friction modeling and compensation for haptic display based on support vector machine," IEEE Trans. on Industrial Electronics, vol. 51, no. 2, pp. 491- 500, April 2004. Abstract Link Full Text Abstract: As the presence of friction in a haptic display device seriously affects its performance, proper compensation of the frictional effects in such a device is of practical importance for advanced virtual reality applications where haptic display plays a critical role. This paper addresses the issue of friction modeling and compensation for haptic control system designs. A new method based on the Support Vector Machine (SVM) is developed in a controller design based on a two-port network to achieve accurate haptic display. The approximation model of friction is established offline through SVM learning and is used for online feed forward friction compensation. The advantages of this novel method are demonstrated through the experiments performed.
51.2.26	T. Muraoka, H. Ikeda, "Selection of display devices used at man-machine interfaces based on human factors," IEEE Trans. on Industrial Electronics, vol. 51, no. 2, pp. 501- 506, April 2004. Abstract Link Full Text Abstract: The display devices used in intelligent machines are very important to exchange information between the operators and the machines online. New selection methods for the display devices used at the man-machine interfaces are proposed based on the results of both the electronic Landolt's ring test and the electronic stress test. The electronic Landolt's ring test checks the degradation of the visual accommodation during the contiguous visual data terminal (VDT) operation, and the electronic stress test checks the efficiency changes of the practical work during the VDT operation. The electronic Landolt's ring and electronic stress tests were respectively confirmed to be useful for selecting the display devices used at man-machine interfaces. In addition, the combination of these two test methods is believed to be utilized for the proper selection of the display devices used at man-machine interfaces in the intelligent machines. Letters to the Editor
51.2.27	Kyu-Wang Lee, Doo-Hee Jung, In-Joong Ha, "An online identification method for both stator resistance and back-EMF coefficient of PMSMs without rotational transducers," IEEE Trans. on Industrial Electronics, vol. 51, no. 2, pp. 507- 510, April 2004. Abstract Link Full Text Abstract: This letter describes an effective online method for identifying both the stator resistance and the back-electromotive-force (EMF) coefficient of a permanent-magnet synchronous motor (PMSM) without rotational transducers. Using only the information of stator currents and voltages, it can provide fairly good identification accuracy under various load conditions and can be easily incorporated into most sensorless speed control schemes proposed in the prior literature.
51.2.28	M. Karimi-Ghartemani, H. Karimi, M.R. Iravani, "A magnitude/phase-locked loop system based on estimation of frequency and in-phase/quadrature-phase amplitudes," IEEE Trans. on Industrial Electronics, vol. 51, no. 2, pp. 511- 517, April 2004. Abstract Link Full Text Abstract: This paper introduces a new phase-locked loop (PLL) system. The proposed system provides the dominant frequency component of the input signal and estimates its frequency. The mechanism of the proposed PLL is based on estimating in-phase and quadrature-phase amplitudes of the desired signal and, hence, has application advantages for communication systems which employ quadrature modulation techniques. The studies demonstrate that the proposed PLL also provides a superior performance for power system applications. Derivation of the mathematical model and theoretical stability analysis of the proposed PLL are carried out using dynamical systems theory. Advantages of the proposed PLL over the conventional PLLs are its capability of providing the fundamental component of the input signal which is not only locked in phase but also in amplitude to the actual signal while providing an estimate of its frequency. Computer simulation is used to evaluate its performance. Evaluations confirm structural robustness of the proposed PLL with respect to noise and distortions.
51.2.29	Xinbo Ruan, Jiangang Wang, "Calculation of the resonant capacitor of the improved current-doubler-rectifier ZVS PWM full-bridge converter," IEEE Trans. on Industrial Electronics, vol. 51, no. 2, pp. 518- 520, April 2004. Abstract Link Full Text Abstract: A resonant capacitor is introduced to the current-doubler-rectifier zero-voltage-switching pulsewidth-modulation full-bridge converter to alleviate the limit for the leakage inductance of the transformer. In this letter, the effect and calculation of the introduced resonant capacitor are analyzed and verified by a 540-W prototype converter.