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The purpose of this paper is to present a state variable model for the drying section of a paper-making machine. This model is based on the mass and energy balance relationships written for steam, paper, cylindrical heater wall, and moisture. These relationships give a set of six nonlinear partial derivative equations. The form of these equations changes somewhat from one cylindrical heater to another. The solution for this model yields the operating parameters needed to achieve the desired steam temperature while obtaining good paper drying. Boundary conditions are specified by a stochastic generator, and initial conditions are obtained by solving the static model. The dynamic model is presented in [1]. In this paper, we present only the state variable model for the paper drying, as well as comparing the obtained results with dynamic model results. Solving the set of differential equations with respect to the boundary conditions, we obtain the standard form of the state representation, which represents the dynamic version of the model used for process control. In conclusion, it can be said that the consistency of the model with experimental results seems to be reasonably good and can be used for process control. Index Terms - Drying paper, linearization, state equations, steam dryer.

In this paper, the influence of the stiffness and damping of real elastic shafts on the behavior of a multidrive system driving a tissue paper machine is investigated. The drive system consists of four dc motors, where two of them drive the Yankee drying cylinder and the other two drive the presses section. Six-pulse thyristor bridge power converters that are connected to the same power transformer supply the motors. The inertias of the motors and the driven machines, in conjunction with the shaft stiffness, form mechanical resonators. Thus, resonance phenomena may occur, which may lead to undesirable results. This particular case results to two three-mass and one five-mass systems. This paper presents an analysis of the resonance frequencies of two sections of the machine during startup and machine production, considering the shaft stiffness (shaft diameter, length, and thickness). The elastic shafts eliminate the ripple of the motor electromagnetic torque, which is transferred to the driven machine. The behavior of elastic shafts with different stiffness in the transmission system is studied. Moreover, the steady state and dynamic behavior of the system considering the influence of the elastic shafts and vibration analysis were investigated using simulation. A model algorithm for system simulation was developed using the MATLAB/SIMULINK software. Characteristic simulation results are presented and are expressed in terms of speed and torque response. Considering the resonance frequency analysis and simulation results, mechanical design guidelines can be given for the most significant drive components in order to avoid torsional oscillation resonance phenomena and minimize torsional oscillations of the drive system. Index Terms--Current and torque control, dc motor drives, modeling, pulp and paper industry, resonance, simulation, vibrations.

Large portions of a winder's control system software are tested during commissioning. This is inefficient because production is stopped and financial pressures limit the time available for testing. However, it avoids the cost of integrating the winder and electrical drive system before installation. This paper describes a winder simulator that allowed control system software to be tested before installation. Shipping roll build up, parent roll build down, mechanical brakes, and a two-drum windup model were developed. These models were used to simulate the winder, web, and drive system dynamics in real time with a dedicated programmable logic controller (PLC). This PLC provided signals for the winder PLC that would normally be supplied by the drive system and various sensors. The simulator was verified with data from a previously installed winder. The use of the simulator before installation of a new winder demonstrated the benefits of pre-installation software testing. Index Terms--Industrial control, pulp and paper industry, real-time systems, simulation, software testing.

This paper investigates the closed-loop properties of the differential coding scheme known as Delta-modulation ([DELTA]-M) when used in feedback loops within the context of feedback-controlled systems. We propose a new modified scheme of the original form of the [DELTA]-M algorithm which is better suited for applications where the sensed information is used in feedback. A state feedback controller is implemented with the state estimated by a predictor-based differential decoder. Stability of the resulting closed-loop system (controller-coder-decoder) is studied. These properties (stability and performance) depend on the quantization parameter [DELTA], which is assumed constant in the first part of this paper. In a further step, parameter [DELTA] is made adaptive, by defining an adaptation law exclusively in terms of information available at both the transmitter and receiver side. With this approach both stability and performance is improved. Index Terms--Delta-modulation ([DELTA]-M), differential coding, networked controlled systems (NCS).

This paper presents an investigation of a multilevel multicell ac/ac converter. The converter employs flying capacitors, whose voltages should remain in a constant relation to the input ac voltage. An inadequate relation between the voltages across the flying capacitors (the imbalance state) results in an increase of voltages across the switches above their rated values. An RLC series circuit (a balancing circuit) with a properly selected resonance frequency was connected in parallel to the load in order to eliminate the imbalance. The balancing process with the use of a passive RLC depends on the configuration and parameters of the balancing circuit, the parameters of the converter, as well as on the operating conditions. This paper focuses on the impact of these parameters on the operation of the converter. Furthermore, the principle of operation of the multilevel multicell ac/ac converter with an application of the natural balancing process is described. Index Terms--AC-AC power conversion, multicell converter, multilevel systems, natural balancing.

Recently, a multilevel cascaded converter fed with a single dc source has been presented. An analysis of the steady-state working limits of this type of converter is presented in this paper. Limits of the maximum output voltage and the minimum and maximum loading conditions for stable operation of the converter are addressed. In this paper, a way to achieve any dc voltage ratio (inside the stable operation area of the converter) between the H-bridges of the single-dc-source cascaded H-bridge converter is presented. The proposed dc-voltage-ratio control is based on a time-domain modulation strategy that avoids the use of inappropriate states to achieve the dc-voltage-ratio control. The proposed technique is a feedforward-modulation technique which takes into account the actual dc voltage of each H-bridge of the converter, leading to output waveforms with low distortion. In this way, the dc voltage of the floating H-bridge can be controlled while the output voltage has low distortion independently of the desired dc voltage ratio. Experimental results from a two-cell cascaded converter are presented in order to validate the proposed dc-voltage-ratio control strategy and the introduced concepts. Index Terms--Modulation, multilevel systems, voltage control.

This paper presents the results of an investigation of the multilevel multicell converters with a passive RLC balancing circuit applied for the maintenance of the voltage sharing on the capacitive sources of the converters. The topologies of dc/dc, ac/ac, dc/ac, and ac/dc multicell converters were analyzed. For the purpose of multilevel modulation, a multicell converter employs several capacitors that are connected to every cell--the flying capacitors, charged to a given level of voltage. An inadequate relation between the voltages across the flying capacitors (the unbalance state) results in the increase of the voltages above their rated values across the switches. An RLC series circuit (a balancing circuit) with the properly selected resonance frequency is connected in parallel to the load in order to eliminate the unbalance. The balancing process with the use of passive RLC depends on the configuration and parameters of the balancing circuit, the parameters of the converter, as well as on the operating conditions. This paper presents the mathematical description of both the converter and the balancing process, the balancing circuit approach in the different topologies of the multicell converters, a selection of the balancing circuit parameters, and the analysis of the improper control conditions. Index Terms--AC-AC power conversion, multicell converter, multilevel systems, natural balancing.

In this paper, a novel 12-sided polygonal space vector structure is proposed for an induction motor drive. The space vector pattern presented in this paper consists of two 12-sided concentric polygons with the outer polygon having a radius double the inner one. As compared to previously reported 12-sided polygonal space vector structures, this paper subdivides the space vector plane into smaller sized triangles. This helps in reducing the switching frequency of the inverters without deteriorating the output voltage quality. It also reduces the device ratings and dv/dt stress on the devices to half. At the same time, other benefits obtained from the existing 12-sided space vector structure, such as increased linear modulation range and complete elimination of 5th and 7th order harmonics in the phase voltage, are also retained in this paper. The space vector structure is realized by feeding an open-end induction motor with two conventional three-level neutral point clamped (NPC) inverters with asymmetric isolated dc link voltage sources. The neutral point voltage fluctuations in the three-level NPC inverters are eliminated by utilizing the switching state multiplicities for a space vector point. The pulsewidth modulation timings are calculated using sampled reference waveform amplitudes and are explained in detail in this paper. Experimental verification on a laboratory prototype shows that this configuration may be considered suitable for high power drives. Index Terms--Pulsewidth modulation (PWM) timings, three-level neutral point clamped (NPC) inverter, twelve-sided polygonal space vector structure.

High-intensity discharge (HID) lamps are becoming popular substitutes for halogen lamps in automotive headlamps because of the high lumen/watt ratio and the color of the light. In this paper, a ballast (integrated with a voltage multiplier circuit in the secondary winding of the dc converter transformer) with dimming control is presented. The proposed circuit not only eliminates one auxiliary winding but also reduces the voltage across the switch on the primary side and consequently permits the selection of switches with a lower rating. A brief review of the HID circuits is done and compared with the proposed circuit. Experimental results from the prototype are presented. This paper also presents different methods of dimming the automotive HID lamps based on analog and digital control and discusses the relative merits of each of the methods. The dimming control is implemented using both the methods, and experimental results are presented. It is envisaged that the dimming control will provide some flexibility to drivers in the control of HID lamps to suit the driving conditions in the modern cities that are very well lit at night. This paper investigates the merits of each method and discusses the practical issues for implementing such controls. Index Terms--Constant power, dimming control, high-intensity discharge (HID) ballast.

In this paper, the application of model predictive control (MPC) for high-performance speed control and torsional vibration suppression in the drive system with flexible coupling is demonstrated. The control methodology presented in this paper relies on incorporating the drive's safety and physical limitations directly into the control problem formulation so that future constraint violations are anticipated and prevented. In order to reduce the computational complexity, the standard MPC controller is replaced by its explicit form. The resulting explicit controller achieves the same level of performance as the conventional MPC, but requires only a fraction of the real-time computational machinery, thus leading to fast and reliable implementation. The simulation results are confirmed by laboratory experiments. Index Terms--Constrained control, elastic couplings, industrial drives, model predictive control (MPC).

Different modulation methods have been proposed to control the multilevel inverters. This paper focuses on the staircase modulation that is very popular for multilevel inverters with low switching frequencies. Nonreal-time algorithms for the staircase modulation cannot be applied practically in multilevel inverters with varying voltage steps, since the sizes of lookup tables would be huge. We propose a real-time algorithm for multilevel inverters with unequal or varying voltage steps under the staircase modulation. The algorithm results in the minimal total harmonic distortion (THD) of the output voltage of the inverter, which is proved by rigorous mathematical derivations in this paper. A new expression of THD is presented to simplify the derivation significantly. Computational complexity of the algorithm is analyzed to estimate the time cost of the calculation. We implemented the algorithm on a digital signal processor and provide experimental results that verify the performance of the proposed algorithm. Index Terms--Multilevel inverter, multilevel pulsewidth modulation (PWM), power conversion, staircase modulation.

This paper proposes a new soft-switching bidirectional dc/dc converter. The proposed converter achieves zero-voltage switching (ZVS) for the entire main switches and zero-current switching for the rectifier diodes in the large-load range. These features reduce switching loss, voltage and current stresses, and diode reverse-recovery effect. The simple electrical isolated topology with the soft-switching characteristic provides an attractive solution for a battery charge/discharge system in an electric vehicle, distributed power system, or uninterruptible power system. This paper describes the operation principle and the ZVS condition in detail. The mathematical model based on the state-space averaging method is also deduced to depict the performance characteristic. Then, design guidelines are presented to ensure the ZVS condition for all the switches. Finally, simulation and experimental results obtained from a 1-kW prototype verify the discussed theoretical analysis. Index Terms--Bidirectional dc/dc converter, zero-current switching (ZCS), zero-voltage switching (ZVS).

In order to ensure increasing current rating of semiconductor switches, paralleling is unavoidable. In this paper, the paralleling of switches has been studied from the reliability point of view. A prototype 4-kW boost converter has been used for this paper. In this boost converter, five insulated gate bipolar transistors are paralleled per switch in order to increase the current rating. Based on experimental results, the reliability of converter has been calculated. Results of reliability calculations showed that paralleling switches extremely decreases reliability of dc--dc converters. The same converter has been constructed by using an integrated power module (IPM). The same calculations have been repeated for the IPM-based converter. The comparison of the results shows that the case of IPM in converters can increase the reliability of the circuit. Index Terms--Boost converter, integrated power module (IPM), paralleling, reliability.

The instantaneous reactive power theory was published 25 years ago, in an IEEE TRANSACTIONS. Since then, it has been the most used in nonlinear load compensation with active power filters. Its application allows constant source power to be obtained after compensation in a simple way. Moreover, some researches have showed up some limitations of the theory, i.e., it goes optimally with source voltage balanced and sinusoidal, but not so good with source voltage unbalanced and/or nonsinusoidal, since the source current obtained is not balanced and sinusoidal. This paper presents a new compensation strategy in phase coordinates, equivalent to the original theory's one. Its simplicity, due to the nonnecessity of coordinate mathematical transformation, makes easier the modifications necessary to obtain alternative compensation objectives. In this way, this paper presents those modifications and derives compensation strategies that obtain alternative compensation objectives: unity power factor or balanced and sinusoidal source current. Finally, compensation strategies are applied to a practical power system, and the results are presented. Index Terms--Active power filters (APFs), instantaneous reactive power theory, power quality.

This paper focuses on direct torque control (DTC) for three-phase ac electric drives. A novel model predictive control scheme is proposed that keeps the motor torque, the stator flux, and (if present) the inverter's neutral point potential within given hysteresis bounds while minimizing the switching frequency of the inverter. Based on an internal model of the drive, the controller predicts several future switch transitions, extrapolates the output trajectories, and chooses the sequence of inverter switch positions (voltage vectors) that minimizes the switching frequency. The advantages of the proposed controller are twofold. First, as underlined by the experimental results in the second part of this paper, it yields a superior performance with respect to the industrial state of the art. Specifically, the switching frequency is reduced by up to 50% while the torque and flux are kept more accurately within their bounds. Moreover, the fast dynamic torque response is inherited from standard DTC. Second, the scheme is applicable to a large class of (three-phase) ac electric machines driven by inverters. Index Terms--AC motor drives, direct torque control (DTC), model predictive control (MPC), power electronics.

This paper utilizes an intelligent system which incorporates Kalman filters (KFs) and a fuzzy expert system to track the tip of a fastening tool and to identify the fastened bolt. This system employs one inertial measurement unit and one position sensor to determine the orientation and the center of mass location of the tool. KFs are used to estimate the orientation of the tool and the center of mass location of the tool. Although a KF is used for the orientation estimation, orientation error increases over time due to the integration of angular velocity error. Therefore, a methodology to correct the orientation error is required when the system is used for an extended period of time. This paper proposes a method to correct the tilt angle and orientation errors using a fuzzy expert system. When a tool fastens a bolt, the system identifies the fastened bolt using a fuzzy expert system. Through this bolt identification step, the 3-D orientation error of the tool is corrected by using the location and orientation of the fastened bolt and the position sensor outputs. Using the orientation correction method will, in turn, result in improved reliability in determining the tool tip location. The fastening tool tracking system was experimentally tested in a lab environment, and the results indicate that such a system can successfully identify the fastened bolts. Index Terms--Accelerometer, expert system, fuzzy logic, gyroscope (gyro), inertial measurement unit (IMU), Kalman filter (KF).

This paper proposes an antilock braking system (ABS), in which unknown road characteristics are resolved by a road estimator. This estimator is based on the LuGre friction model with a road condition parameter and can transmit a reference slip ratio to a slip-ratio controller through a mapping function. The slip-ratio controller is used to maintain the slip ratio of the wheel at the reference values for various road surfaces. In the controller design, an observer-based direct adaptive fuzzy-neural controller (DAFC) for an ABS is developed to online-tune the weighting factors of the controller under the assumption that only the wheel slip ratio is available. Finally, this paper gives simulation results of an ABS with the road estimator and the DAFC, which are shown to provide good effectiveness under varying road conditions. Index Terms--Antilock braking systems (ABSs), observer-based direct adaptive fuzzy-neural controller (DAFC), road estimators.

The direct thrust control (DTC) has been utilized as a general formalism methodology for permanent-magnet linear synchronous motors (PMLSMs). The imposition control policies did not seem to handle the inherent flux linkage problems. This paper will try to propose a solution for the problems. This paper presents a genetic PI parameters generator and a new DTC policy for the motor control systems. Moreover, this paper also proposes a new switching table which can assist in selecting the optimum voltage vectors for the control system. The advantage of the proposed approach is that the clear presentation of the system behavior and readiness for implementation. Finally, some results of the simulation and the experiment both are met as expected. To the authors' knowledge, this is the first work that employs DTC to implement on a real-world PMLSM which is starting at arbitrary positions and can be allowed moving in the full route. Index Terms--Direct thrust control (DTC), flux linkage estimation, permanent-magnet linear synchronous motor (PMLSM).

This paper proposes a generalized method for the generation of space vector pulsewidth modulation (SVPWM) signals for multilevel inverters. In the proposed method, the actual sector containing the tip of the reference space vector need not be identified. A method is presented to identify the center of a subhexagon containing the reference space vector. Using the center of the subhexagon, the reference space vector is mapped to the innermost subhexagon, and the switching sequence corresponding to a two-level inverter is determined. A new technique is proposed in this paper, by which these two-level vectors are translated to the switching vectors of the multilevel inverter by adding the center of the subhexagon to the two-level vectors. The proposed method can be extended to any n-level inverter, and a generalized algorithm is proposed. The scheme is explained for a five-level inverter, and experimental results are presented for a three-level inverter. Index Terms--Multilevel inverter, open-end winding, reverse mapping, space vector pulsewidth modulation (SVPWM).

This paper proposes a multilevel inverter configuration which produces a hexagonal voltage space vector structure in the lower modulation region and a 12-sided polygonal space vector structure in the overmodulation region. A conventional multilevel inverter produces 6n [+ or -] (n = odd) harmonics in the phase voltage during overmodulation and in the extreme square-wave mode of operation. However, this inverter produces a 12-sided polygonal space vector location, leading to the elimination of 6n [+ or -] 1 (n = odd) harmonics in the overmodulation region extending to a final 12-step mode of operation with a smooth transition. The benefits of this arrangement are lower losses and reduced torque pulsation in an induction motor drive fed from this converter at higher modulation indexes. The inverter is fabricated by using three conventional cascaded two-level inverters with asymmetric dc-bus voltages. A comparative simulation study of the harmonic distortion in the phase voltage and associated losses in conventional multilevel inverters and that of the proposed inverter is presented in this paper. Experimental validation on a prototype shows that the proposed converter is suitable for high-power applications because of low harmonic distortion and low losses. Index Terms--Multilevel inverter, pulsewidth modulation (PWM) control, 12-sided polygonal space vector structure.

This paper describes an adaptive control to realize the desired steering characteristics on a vehicle. As is well known, the steering characteristics indicate handling performance on a vehicle and are important for safe driving. In this paper, a strategy to adjust it to a driver's preference easily using a Steer-by-Wire system is proposed. The control system including the proposed method intervenes only when the front tire cornering stiffness undergoes many changes. Then, the estimated self-aligning torque is fed back to the steering wheel so that a driver can feel reaction torque from the road. This is one of the remarkable features in the proposed Steer-by-Wire system. Numerical simulation and experiment are carried out to show the validity of the proposed method. Index Terms--Parameter identification, steer-by-wire system, steering characteristics, steering control, vehicle state estimation.

Solar photovoltaic (PV) arrays in portable applications are often subject to partial shading and rapid fluctuations of shading. In the usual series-connected wiring scheme, the residual energy generated by partially shaded cells either cannot be collected (if diode bypassed) or, worse, impedes collection of power from the remaining fully illuminated cells (if not bypassed). Rapid fluctuation of the shading pattern makes maximum power point (MPP) tracking difficult; generally, there will exist multiple local MPPs, and their values will change as rapidly as does the illumination. In this paper, a portable solar PV system that effectively eliminates both of the aforementioned problems is described and proven. This system is capable of simultaneously maximizing the power generated by every PV cell in the PV panel. The proposed configuration consists of an array of parallel-connected PV cells, a low-input-voltage step-up power converter, and a simple wide bandwidth MPP tracker. Parallel-configured PV systems are compared to traditional series-configured PV systems through both hardware experiments and computer simulations in this paper. Study results demonstrate that, under complex irradiance conditions, the power generated by the new configuration is approximately twice that of the traditional configuration. The solar PV system can be widely used in many consumer applications, such as PV vests for cell phones and music players. Index Terms--Complex illumination, maximum power point tracking (MPPT), partial shading, photovoltaic (PV) solar cell, power converter, solar array.

This paper presents a novel topology named Forward--flyback bidirectional dc-dc converter (BDC), which is a hybrid of forward and flyback converters. The windings of forward and flyback transformers are connected in series on the primary side and in parallel on the secondary side. The proposed converter has no startup problem and no high voltage spikes on the switches, which otherwise are inherent for current- and voltage-fed-type bidirectional converters. It is easy to achieve soft switching by proper control and design. The built-in flyback transformer acts as a filter inductor, so the current ripple is smaller than flyback BDCs. In this paper, the operation principles and characteristics of the proposed topology are analyzed in detail. The advantages aforementioned are verified with experimental results of a 300-W prototype. Index Terms--Bidirectional, converter, dc-dc, forward-flyback.

Based on the fact that a hybrid electric vehicle (HEV) connects a high number of batteries in series to obtain more than approximately 300 V, this paper proposes a modularized charge equalizer for an HEV battery pack. In this paper, the overall battery string is modularized into [M.sup.*] N cells, where M is the number of modules in the string and N is the number of cells in each module. With this modularization, low voltage stress on the electronic devices can be achieved, which means that there is less chance of a failure on the charge equalizer. The power rating selection is one of the most important design issues for a charge equalizer because it is very closely related to equalization time. To solve this problem optimally, this paper presents a power rating design guide. In addition, this paper considers system-level design issues, such as cell voltage acquisition, equalizer control logic, and system-level grounding. The simulation and experimental results are presented to show the usefulness of the optimal power rating selection guide and the low voltage stressed charge equalization process. Index Terms--Hybrid electric vehicle (HEV), lithium-ion battery, modularized charge equalization, module balancing transformer (MBT).

In this paper, an interleaved ac--dc converter based on current tracking without any current sharing required is presented and applied to a two-phase flyback converter. This is realized using two critical-conduction-mode (CRM) pulsewidth-modulated chips, together with a field-programmable gate array technique. By doing so, not only are the total harmonic distortion and the power factor improved but the output power is also upgraded. In this paper, the circuit operation is described in detail, with some experimental results given to verify the proposed control scheme. Index Terms--AC-DC converter, current sharing, field-programmable gate array (FPGA), flyback converter, interleaved control, output power, power factor (PF), total harmonic distortion (THD).

This paper describes a novel regenerative braking control scheme of electric power-assisted wheelchairs for safety driving on downhill roads. The 'electric power-assisted wheelchair' which assists the driving force by electric motors is expected to be widely used as a mobility support system for elderly people and disabled people; however, it has no braking system to suppress the wheelchair's velocity and brings the dangerous and fearful driving particularly on downhill roads. Therefore, this paper proposes a novel safety and efficient driving control scheme based on the regenerative braking system. This paper applies the regenerative braking system with the step-up chopper circuit serially connecting two motors and realizes the velocity feedback control with the variable duty ratio so that it tracks the optimal velocity based on the Minimum Jerk Model. In addition, the dynamic braking system is also applied at the low-speed range instead of the regenerative braking in order to suppress the acceleration. Some driving experiments on the practical downhill roads show the effectiveness of the proposed control system. Index Terms--Driving control, dynamic braking, electric power-assisted wheelchair, Minimum Jerk Model, regenerative braking control.

This paper presents the design and analysis of a novel high thrust force linear actuator with high backdrivability. This motor consists of a mover and a stator with spiral (helical) structure. The mover moves spirally in the stator, and the linear motion is extracted to drive the load. This motor is a direct-drive system and highly backdrivable. In this paper, a basic model and thrust-force/torque equations are proposed, and finite-element method analysis and experimental results of a prototype are presented. From experiments, the designed spiral motor achieves 2000-N rated thrust force. The thrust-force capabilities of the spiral motor are compared with other linear motors. It is confirmed that the spiral motor is almost close to the latest state of the art in linear motor technology. Index Terms--Axial flux machines, electrical machines, finite-element analysis (FEA), finite-element method (FEM), helical-motion motors, linear actuators, permanent-magnet (PM) machines, spiral motors, thrust force.

This paper proposes a tactile-sensing mechanism for a robot. The mechanism is composed of a force-sensor device and an end-effector of shell shape. Since the end-effector plays the role of an outer shell, a force can be sensed at any position on the body. Due to the aspect of its intrinsic contact sensing, position of the single contact point is calculable without any sensor array. Another advantage is that the six-axis resultant force is measurable. This paper shows that the mechanism is also available for the end-effector with an angulated shape. The only condition for the shape is to be a convex hull. Some experimental results evaluate sources of error in practical measurement and show the validity of the proposed mechanism. Index Terms--Force sensation, force sensor, haptic sensor, tactile sensation, tactile sensor, whole-body force sensation.

This paper presents the development and real-time implementation of a nonlinear controller for the speed control of an induction motor (IM) drive. Neglecting the iron loss in an IM model causes performance deterioration, and there has been research to investigate and cope with this problem in the vector control of an IM. However, little work has been done in the area of the nonlinear control of an IM. In this paper, an adaptive backstepping-based nonlinear controller incorporating the iron loss is developed under the parameter uncertainties. To reduce the complexity in the design of the controller, the motor model is referenced to the rotor magnetizing current, and the controller is developed in the rotor-flux-oriented control scheme. The adaptive backstepping technique is utilized to estimate the parameters online and maintain the global stability of the drive through Lyapunov. The proposed controller is successfully implemented in real time using a digital signal processor board DS 1104 for a laboratory 1/3-hp IM. Both simulation and experimental results show that the proposed controller successfully achieves the rotor-speed-tracking objective and improves dynamic responses as compared to the one without parameter adaptation. Index Terms--adaptive backstepping design, digital signal processor (DSP) and real-time implementation, induction motor (IM), iron-loss resistor, nonlinear control, speed control, vector control.

This paper proposes a hybrid fuel cell power system, which consists of a fuel cell, an isolated unidirectional converter, a bidirectional converter, an inverter, and a battery. The fuel cell and the battery are connected to the same voltage bus through an appropriate hybrid full-bridge LLC resonant unidirectional converter and a three-level buck/boost bidirectional converter, respectively. The battery is an auxiliary energy source, powers the load during the system's start state to make it easy for the system to cold start, and provides or absorbs the dynamic power when the load varies and the fuel cell cannot respond immediately, so the system dynamic characteristics are improved. Furthermore, the battery can also provide peak power at overload, so the power rating of the fuel cell can be decreased, which reduces the total system cost. In order to ensure that the system operates with high efficiency, this paper also proposes a power management control scheme, which controls the bidirectional converter operating under buck, boost, or shutdown mode according to the operation condition of the fuel cell and battery, so that the battery can be charged or discharged. The operation of the system during cold start and overload are analyzed in detail. A 1-kW fuel cell power system was built in the laboratory. Experimental results are shown to verify the theoretical analysis. Index Terms--Battery, bidirectional converter, fuel cell, power management, unidirectional converter.

In this paper, control systems over soft real-time carrier sensing multiple access networks are considered. A precise modeling of the system is presented, and the effects of using the communication network are probabilistically characterized. The results can be used to study several control performance issues in the stochastic setting. In this paper, the expected value of a quadratic cost function is calculated, and the result is used for optimal controller tuning and performance analysis through an example. Index Terms--Carrier sensing multiple access (CSMA) protocol, communication constraints, networked control systems (NCSs), quadratic cost function.

This paper reports a tungsten microhotplate fabricated in a standard CMOS process and the implementation of a MicroPirani pressure sensor with it. A monolithic constant-current circuit including an operational amplifier is used to bias the tungsten microhotplate to measure the gas pressure. The sensor shows a linear response to the gas pressure in the range of 1-100 Pa when driven by a constant current of 7 mA. In this regime, the sensitivity of the sensor is 0.23 mV/Pa, the linearity is 4.95%, and the hysteresis is 8.69%. The MicroPirani pressure sensor in this paper can be used in a medium-vacuum measurement. Because tungsten in a standard CMOS process has a large temperature coefficient regardless of the different manufacturing processes, the design of the tungsten microhotplate can be applied to other thermal-based sensors, even in different standard CMOS processes. Index Terms--CMOS pressure sensor, microelectromechanical systems (MEMS), pressure sensor, tungsten microhotplate.

A second-order microelectromechanical systems (MEMS) filter with high selectivity and sharp rolloff is required in wireless transceivers used in dense wireless sensor networks (WSNs). These sensors are expected to replace existing wired sensors used in industrial-plant management and environmental monitoring. These filters, together with MEMS-based oscillators and mixers, are expected to replace off-chip components and enable the development of a single-chip transceiver. Such a transceiver will leverage the integrated MEMS components' characteristics to operate at lower power and, hence, longer battery life, making autonomous WSNs more feasible in a wider range of applications. As a result, this paper presents the design and optimization of the coupling beam of wineglass-mode micromechanical disk filters using simulated annealing. The filter under consideration consists of two identical wineglass-mode disk resonators, mechanically coupled by a flexural-mode beam. The coupled two-resonator system exhibits two mechanical-resonance modes with closely spaced frequencies that define the filter pass-band. A constraint is added on the beam length to eliminate the effect of the coupling-beam mass on the filter's resonant frequency. A new process flow is proposed to realize self-aligned overhanging coupling beams designed in this paper. Index Terms--High-frequency microelectromechanical systems (MEMS), micromechanical filters, optimization, simulated annealing, spring coupling.

This paper introduces an improved differential evolution (DE) algorithm for robust layout synthesis of microelectromechanical system components subject to inherent geometric uncertainties. A case study of the layout synthesis of a comb-driven microresonator shows that the approach proposed in this paper can lead to design results that meet the target performance and are less sensitive to geometric uncertainties than the typical designs. It is also demonstrated that the algorithm proposed in this paper cannot only obtain better results than the standard DE algorithm but also outperform some other state-of-the-art algorithms in constrained optimization. Index Terms--Differential evolution (DE), microelectromechanical systems (MEMS), robust design, stochastic ranking (SR).

In this paper, the analysis, design, and implementation of a novel rotor position estimator for the control of variable-speed switched reluctance generators (SRGs) are presented. The rotor position is obtained using the unsaturated instantaneous inductance. This unsaturated inductance is estimated calculating the slope of the phase current and using a reduced-size neural network (NN) whose inputs are the average current and the saturated inductance. The proposed estimator requires less processing time than traditional methods and can be fully implemented using a low-cost DSP with very few additional analog/ digital components. The rotor position estimator presented in this paper can be applied to a wind energy conversion system where the SRG is used as a variable-speed generator. This application is currently being studied because the SRG has well-known advantages such as robustness, low manufacturing cost, and good size-to-power ratio. Simulation and experimental results are presented using a 2.5-kW 8/6-SRG prototype. Index Terms--Neural networks (NNs), position control, wind power generation.

Complex wavelet transform (CoWT)-based phase information (PI) extraction methods are popular. None of them is simultaneously simple, fast, and nonredundant. Real discrete wavelet transform (RDWT) is simple, fast, and nonredundant, but it is usually regarded to be lacking PI. After finding out that RDWT conserves the PI of an analyzed signal, this paper proposed three RDWT-based PI extraction methods and proved that RDWT-based PI extraction methods are equal to CoWT-based ones from the mathematical point of view. Therefore, RDWT-based methods not only can extract PI but also can inherit all merits of RDWT. This paper further presented a quadrature procedure to extract the actual phase of single-frequency or asymptotic signals. Test examples demonstrated that the extracted PI by using the CoWT- and RDWT-based methods is almost the same, and the extracted phase curves by using the RDWT-based quadrature method are really the actual ones. Some engineering applications of the proposed method are discussed, and the PI extraction programs of the method are given. Index Terms--Complex continuous wavelet transform (CCWT), complex discrete wavelet transform (CDWT), phase information (PI) extraction method, quadrature signal in wavelet domain, real discrete wavelet transform (RDWT).

In this paper, the authors present an extended survey on the evolution and the modern approaches in the thermal analysis of electrical machines. The improvements and the new techniques proposed in the last decade are analyzed in depth and compared in order to highlight the qualities and defects of each. In particular, thermal analysis based on lumped-parameter thermal network, finite-element analysis, and computational fluid dynamics are considered in this paper. In addition, an overview of the problems linked to the thermal parameter determination and computation is proposed and discussed. Taking into account the aims of this paper, a detailed list of books and papers is reported in the references to help researchers interested in these topics. Index Terms--Computed fluid dynamic, electrical machines, finite-element analysis (FEA), lumped-parameter thermal network (LPTN), thermal model, thermal parameter identification.

Various short-timescale transients exist in power electronic converters, particularly in high-voltage and high-power systems. The timescales of these transients are from nanoseconds to microseconds, including a switching transition of power semiconductor devices, commutating processes, and drive signal transmissions. These transient processes directly affect the performance and reliability of power electronic systems. Therefore, it is necessary to study these short-timescale processes. Based on two high-power prototype power converters, a 6000-V/1250-kW three-level adjustable-speed drive and a 10-kW/600-V dc-dc converter, this paper studies the various abnormal behaviors of the converters that occurred during the operation of these converters. Dead bands and accumulated switching errors are also investigated. A combined microscopic pulsed power and macroscopic control strategy was proposed for the design of power electronic converters. Three new concepts for power electronic converters are introduced and validated in this paper: 1) sneak pulse; 2) energy dead band; and 3) transient commutating topology. Index Terms--Adjustable-speed drive (ASD), dc-ac inverter, dc-dc converter, dead band, isolation, minimum pulsewidth, phase-shift control, power electronics, pulsewidth modulation, safe operation area (SOA), short timescale, three-level converter.

The problem of reactive power and harmonics in the medium voltage level of a power distribution system is considered in this paper. Reconfiguration of the power delivery network imposes new constraints in a distribution substation so that the reactive compensation should be increased. The alternative of a shunt hybrid active filter connected to the 13.8-kV level to enhance the power quality is analyzed in this paper. This proposal uses the existing capacitor bank to build a hybrid filter in which the complementary compensation is performed by the active filter. The performance of the hybrid filter is evaluated with extensive simulations considering reactive power, harmonics, and unbalance compensation. It shows very good behavior in steady-state and transient conditions. Index Terms--Active filters, harmonic distortion, power distribution, power quality, reactive power.

New energy concepts such as distributed power generation systems (DPGSs) are changing the face of electric distribution and transmission. Power electronics researchers try to apply new electronic controller solutions with the capacity of implementing new and more complex control algorithms combined with internal high-speed communication interfaces. Thus, it is possible to monitor, store, and transfer a large number of internal variables that can be sent online to local or remote hosts in order to take new set points of different generation units. With this objective, this paper presents the design, implementation, and test of an industrial multiprocessor controller based on a floating-point digital signal processor (DSP) and a field-programmable gate array, which operate cooperatively. The communication architecture, which has been added to the proposed electronic solution, consists of a universal serial bus (USB), implemented with a minimum use of the DSP core, and a controller area network (CAN) bus that permits distributed control. Although the proposed system can be readily applied to any DPGS, in this paper, it is focused on a 150-kVA back-to-back three-level neutral-point-clamped voltage source converter for wind turbine applications. Index Terms--Digital signal processors (DSPs), field-programmable gate arrays (FPGAs), power distribution control, power system communication.

Digital frequency input and output (typically in the range 1 Hz to 100 kHz) for data transmission are employed in many industrial applications. This paper provides the following elaborations of the ISIE'07 conference paper. A thorough literature review suggests that previous techniques can be classified into three basic approaches. Theoretical expressions for the errors of each are derived and compared with the new approach developed by the authors. Each method has been implemented in a more recent field programmable gate array architecture (Spartan 3), and the results are consistent with the theoretical values. The new method provides a precision of 6 x [10.sup.-6]% or better for all frequencies, based on a 40-MHz clock. Index Terms--Field-programmable gate arrays (FPGAs), frequency control, Handel-C, hardware compilation, pulse frequency modulation.

This paper presents a novel initial value compensation (IVC) using an additional input for semi-closed control systems. The authors have already proposed the IVC approach using the additional input for residual vibration suppression in the fast and precise positioning control. In the approach, however, an essential subject has remained, i.e., the positioning control in the load side could not satisfy the required performance because the systems have been constructed under the assumption of a semi-closed control system. An improvement of the control performance in load position, therefore, is discussed in this paper, where the appropriate assignments of poles and zeros in IVC are ensured, considering the transfer functions of position in both sensor and load for the control initial values. The effectiveness of the proposed approach has been verified by numerical simulations and experiments using a prototype. Index Terms--Fast-response and high-precision positioning, high-order vibration modes, initial value compensation (IVC), residual vibration suppression, semi-closed control system.

Power electronics technology has gone through dynamic evolution in the last four decades. Recently, its applications are fast expanding in industrial, commercial, residential, transportation, utility, aerospace, and military environments primarily due to reduction of cost, size, and improvement of performance. In the global industrial automation, energy conservation, and environmental pollution control trends of the 21st century, the widespread impact of power electronics is inevitable. It appears that the role of power electronics on our society in the future will tend to be as important and versatile as that of information technology today. In this paper, the importance of power electronics will be discussed after a brief historial introduction in the beginning. Then, the recent advances of power semiconductor devices, converters, variable-frequency ac drives, and advanced control and estimation techniques will be reviewed briefly. Unlike a traditional technology survey paper, the number of figures is kept intentionally small in favor of the text within the length constraint of this paper. The prognosis of different areas will be highlighted wherever possible based on the author's own knowledge and experience. In conclusion and future scenario, the trend of power electronics and motor drives along with some possible research and development areas will be highlighted. Index Terms--Control, converters, motor drives, power electronics.

This paper deals with the identification of mechanical backlash in drives. The development of a reliably working identification method is intended. The method presented in this paper is considered to be a necessary step toward the development of more complex diagnosis tools and condition monitoring systems that are demanded today in the area of servodrives. The main idea for identifying backlash is explained. Measurement results clearly point out the efficiency of the identification strategy proposed in this paper. Thus, the results of the identification can be utilized for the tuning of the controller or for the diagnostics of the actual state of the drive. Index Terms--Drives, mechatronics, modeling, system identification.

In this paper, an Eye-in-Hand robotic system with laser pointer is developed to detect, grasp, and assemble a planar object on a main body in robotic manufacturing systems. This paper is focused on detecting the object and moving the end effector to a position where a pump can perfectly suck up the object. A switching control of image-based visual servoing (IBVS) is designed to control the pose of the end effector with respect to the stationary object so that the image features of the planar object observed by the camera converge to the target image features for the further assembly. A simple off-the-shelf laser pointer is adopted to realize the depth estimation for obtaining the image Jacobian matrices. By using a laser spot as an image feature and the separate degree-of-freedom method, the proposed switch-control algorithm decouples the rotational and translational motions of the camera to avoid the inherent drawbacks of traditional IBVS. The experiments on a robotic assembly system are given to verify the effectiveness of the proposed method. Index Terms--Control systems, laser pointer, robot vision systems, visual servoing.

This paper discusses velocity measurement for motor drives with optical encoders. Although many methods on velocity measurement have been proposed, accurate measurement was not achieved in a high-speed range. This paper therefore proposes synchronous-measurement method (S method) that measures the velocity synchronized with the alteration of pulse numbers in each sampling period. Accurate velocity measurement is achieved in all speed ranges with this method. Furthermore, other velocity prediction methods are applicable in addition to the method. Simulation and experimental results verify the validity of the proposed method. Index Terms--Acceleration control, mechatronics, motion control, optical encoder, tachometers, velocity measurement.

In this paper, a new control system to regulate the reactive power supplied by a variable-speed wind energy conversion system (WECS), based on an induction generator fed by a matrix converter (MC), is presented. The control system discussed in this paper is based on an input current observer, implemented using an estimation of the modulation matrix, and a nonlinear control loop that regulates the displacement angle at the MC input. The reactive power capability of the proposed system is also investigated. The work presented in this paper demonstrates that, for the proposed WECS, the maximum reactive power supplied to the grid is about 40% of the nominal value. Experimental results obtained from an experimental prototype are presented in this paper. The performance of the system using a wind turbine emulator and typical wind profiles is discussed in this paper. Index Terms--Current control, power generation, reactive power control, wind power generation.

Harmonics are a very important issue in the design and operation of medium-voltage inverter drives, due to restrictions imposed by regulations. This paper studies the harmonics generated by a three-phase multicell cascade inverter, with single-phase pulsewidth modulation rectifiers at the input side of each cell; thus, the entire topology is able to regenerate power to the net. This paper identifies accurately the harmonic generation process in the dc-link voltage, the input current of each cell, and, therefore, at the input side of the inverter. Moreover, this paper proposes a method to reduce and, in some cases, eliminate the input current harmonics, reaching a very high input power factor for any operation condition. Simulation and experimental results are provided to validate the theoretical analysis. Index Terms--Harmonic analysis, power electronics, voltage control.

Voltage--oriented PI control of three-phase grid-connected pulsewidth-modulation rectifiers with LCL filters is addressed. LCL filters require resonance damping. Active resonance damping is state of the art to face the problem, but it is still under investigation because of the manifold solutions. It is often realized using many sensors and/or complex control algorithms. In contrast, pure PI control requires only one set of current sensors, and its implementation and design are rather simple and well known from the L filter control. PI control has already been shown to be a suitable solution also for LCL filters, but there are limitations. These are investigated in this paper. System stability is analyzed with respect to different ratios of LCL filter resonance and control frequencies. The latter are important parameters for system design and control. Both line and converter current control are analyzed. For a certain range of frequency ratios, the voltage-oriented PI control gives stable performance without additional feedback, but for ratios outside this range, stable operation is impossible. Experimental tests validate the theoretical results. In addition, an experimentally determined LCL filter transfer function is shown in this paper, which shows a lower resonance peak as expected from commonly used filter models. Index Terms--Active damping (AD), grid-connected pulsewidth-modulation (PWM) rectifier, LCL filter, PI current control.

Among converter control techniques, the direct current tracking methods give fast and accurate response with good dynamic performance. Unfortunately, in multiswitching systems, these techniques have certain drawbacks. In particular, when the number of controlled switching elements is greater than the number of independent currents, undesirable interactions arise between the control algorithms. This paper proposes a general and systematic approach to decouple the controlled currents. This allows us to adopt simpler current tracking strategies (not discussed in this paper) for each controlled switching element even in complex multiswitching converters. Independence between lower level switching algorithms is achieved by means of a set of decoupling variables. Simulation and experimental results from a case study are reported. Index Terms--Current control of multiconverters, switching strategies.