bluuebunny/crossref_metadata_2025_split huggingface dataset:
American Library Association Conference 2009
Authors: Ashcroft Linda 
Published: December 2009

PurposeThe purpose of this paper is to provide a flavour of the content of the American Library Association Annual Conference held in Chicago in July 2009.Design/methodology/approachThe approach takes the form of an outline description of the issues, content, networking, speakers and participants of this conference.FindingsThis major conference covered many topical issues and themes, latest trends and research and leading edge technology applicable to librarians and information professionals internationally. It facilitated many networking opportunities.Originality/valueThe paper is a conference report of value to librarians and information professionals, as the variety of themes apply to the various aspects of library and information work.
Field and field‐circuit models of electrical machines
Authors: Demenko Andrzej , Hameyer Kay 
Published: December 2009

PurposeThe purpose of this paper is to develop and systemize the 3D finite element (FE) description of electromagnetic field in electrical machines.Design/methodology/approach3D FE models of electrical machines are considered. The model consists of FE equations for the magnetic field, equations describing eddy currents and equations, which describe the currents in the machine windings. The FE equations are further coupled by the electromagnetic torque to the differential equation of motion. In the presented field‐circuit model, the flux linkages with the windings are expressed by two components. Attention is paid to the description of machine winding. Both scalar and vector potential formulations are analysed. The FE equations are derived by using the notation of circuit theory. The methods of movement simulation and torque calculation in FE models are discussed.FindingsProposed circuit description of electromagnetic field in electrical machines conforms to the applied method of electric and magnetic circuit analysis. The advantage of the presented description is that the equations of field model can be easy associated with the other equations of the electric drive system.Originality/valueThe applied analogies between the FE formulation and the equivalent magnetic and electric network models help formulate efficient field models of electrical machines. The developed models after coupling to the models of supply and control system can be successfully used in the analysis and design electric drives.
Simulation of wave propagation effects in machine windings
Authors: De Gersem Herbert , Henze Olaf , Weiland Thomas , Binder Andreas 
Published: December 2009

PurposeThe purpose of this paper is to offer a simulation method for predicting the impedance of machine windings at higher frequencies.Design/methodology/approachA transmission‐line model (TLM) is developed based on parameters calculated on the basis of electroquasistatic and magnetoquasistatic finite‐element (FE) model of the winding cross‐section.FindingsThe FE formulations for the low‐ and high‐frequency limits give acceptable results for the respective frequency ranges. An eddy‐current formulation is only accurate on a broader region when the FE mesh is sufficiently fine to resolve the skin depth.Research limitations/implicationsThe paper is restricted to frequency‐domain simulations.Practical implicationsThe results of the paper improve the understanding of higher‐frequency parasitic effects in electrical drives with long windings.Originality/valueThe paper shows the limitations of the FE methods used for determining the parameters of the TLMs and remedies to avoid these.
Optimization of the electromechanical systems on the basis of coupled field‐circuit approach
Authors: Nowak Lech 
Published: December 2009

PurposeThe purpose of this paper is to present an algorithm of the optimization of the dynamic parameters of an electromagnetic linear actuator operating in error‐actuated control system.Design/methodology/approachThe elaborated “unaided” software consists of two main parts: optimization solver and numerical model of the actuator. Genetic algorithm has been used for optimization. The coupled field‐circuit‐mechanical model for the simulation of the system dynamics has been applied. Different optimization problems have been considered. The shape of the steady‐state force‐displacement actuator characteristic has been imposed and its deviation has been minimised. Next, the total operation time of the actuator without feedback, and the setup time of the actuator with feedback are minimised. Finally, required trajectory of movement has been imposed and trajectory error is minimised.FindingsThe elaborated algorithm and the computer code can be an effective tool for field‐circuit simulation of the dynamics of an electromagnetic linear actuator that operates in an automatic control system. It enables optimal design of the electromechanical system in respect to its dynamic properties.Originality/valueThe elaborated algorithm and the computer code presented in this paper can be an effective tool for the field‐circuit simulation of the dynamics of an electromagnetic linear actuator that operates in an automation control system.
A nonlinear time‐varying map of a buck power‐switching amplifier for wide band tracking applications
Authors: El Aroudi A. , Alarcón E. , Rodríguez E. , Leyva R. 
Published: December 2009

PurposeThe purpose of this paper is to characterize the nonlinear dynamical behaviour of a buck‐based power‐switching amplifier controlled by fixed frequency and pulse width modulation with a proportional‐integral compensator. The system has two forcing frequencies and one natural frequency and therefore it is characterized by three different scales of time. When the frequencies are far one from the other, quasi‐static approximation can be used. However, as the switching and the modulating frequencies become closer, this approximation is not valid and the results based on it lead to erroneous conclusions about the dynamics of the system.Design/methodology/approachA discrete time approach is used to reveal the interesting nonlinear phenomena that the system can exhibit. From numerical simulations using the switched model, it is shown that the system can present period‐doubling bifurcation at the fast scale (switching frequency).FindingsAn exact solution discrete‐time model is derived, able to predict accurately the nonlinear dynamical behaviour of the system.Originality/valueThe discrete time model is obtained without making quasi‐static approximation. The exact switched model is used to validate the discrete‐time model obtained. Finally, the effect of the switching frequency instabilities on the output voltage spectrum has been explored.
Modified direct torque control for saturated interior permanent magnet synchronous motors
Authors: Majidi Behrooz , Milimonfared Jafar , Malekian Kaveh 
Published: December 2009

PurposeTo optimize the performance of direct torque‐controlled interior permanent magnet synchronous motor drives, the purpose of this paper is to modify the constraints and strategies of such a control while accounting for magnetic saturation.Design/methodology/approachThe machine model used to investigate the proposed method is the conventional two‐axis machine model, which is modified to include magnetic saturation in the quadrature axis. With the consideration of magnetic saturation, all optimal strategies, which correspond to the maximum torque per ampere and field weakening strategies, and motor‐inverter limitations are derived inT−|ψs| plane to apply in the direct torque control (DTC) method. Such strategies which take magnetic saturation into account and determine the optimal torque and flux commands are derived and implemented in DTC method.FindingsUsing the modified strategies ensures that the machine capacity is applied as much as possible. Simulation results emphasize the applicability and effectiveness of the proposed control process.Research limitations/implicationsIn order to use the proposed method, it is necessary to define quadrature‐axis inductance as a function of quadrature‐axis current. Since, in this method, a simplified function is applied, it is not required to know exact magnetic behavior of motor and this simplified function can be easily obtained using finite element softwares.Practical implicationsUsing the proposed method in practice results in better dynamic operation as well as maximal usage of the motor capacity.Originality/valueThis paper deals with consideration of magnetic saturation in DTC method which is not done in pervious works.
DFIM vector control sensitivity with current sensor faults
Authors: Abdellatif Meriem , Pietrzak‐David Maria , Slama‐Belkhodja Ilhem 
Published: December 2009

PurposeThe purpose of this paper is to present a doubly fed induction machine (DFIM) operating in motor mode and supplied by two voltage source inverters (in stator and rotor sides).Design/methodology/approachThe aim is to analyze the current sensor fault effects on the stator flux‐oriented control according to the current input‐output decoupling. This justifies the necessity of a reconfiguration control in order to satisfy the system service continuity. Also, a theoretical development of sensitivity coefficients gives an idea about control robustness toward a current sensor fault.FindingsThis paper emphasizes the system performance close dependency to the current sensor outputs accuracy. Moreover, simulation results point out the operation system deterioration in case of current sensor fault, which leads in most cases to its shut down in contrast with the industrial expectations. In this paper, the suggested solution is the DFIM speed drive control reconfiguration when a current sensor fault occurs in order to ensure system service continuity. MATLAB‐Simulink simulation results illustrate the system behavior before and after a current sensor fault. System performance preservation is performed after control reconfiguration.Originality/valueThis solution presented in this paper is relevant, especially because of its simplicity.
Optimal control of current switching angles for high‐speed SRM drive
Authors: Deskur Jan , Pajchrowski Tomasz , Zawirski Krzysztof 
Published: December 2009

PurposeThe purpose of this paper is to propose a method of optimal control of current commutation of switched reluctance motor drive.Design/methodology/approachThe problem of optimal current commutation control is solved by off‐line selection of switching‐on and switching‐off angles. Selection of optimal values of angles is provided on computer model of the drive with help of particle swarm optimisation method. The optimal angle values are detected as functions of phase current and rotor speed. These calculated optimal values are stored in microcomputer control system memory in form of two‐input look‐up tables. The results are validated on laboratory set up.FindingsThree different criteria of optimal control, which are taken into account: the maximum electromagnetic torque for given reference current, the maximum ratio of electromagnetic torque to root mean square value of phase current and the minimum electromagnetic torque ripples, gave a good results validated by simulation and experimental investigations.Practical implicationsA simple control method is proposed to optimise switched reluctance motors drive behaviour. Such an approach can be recommended for practical implementations.Originality/valueThe off‐line optimisation of switching angles, which is realised on computer model, is sufficient to obtain a good control effect.
Instantaneous torque control using flux‐based commutation and phase‐torque distribution technique for SR motor EV
Authors: Goto Hiroki , Nishimiya Ayumu , Guo Hai‐Jiao , Ichinokura Osamu 
Published: December 2009

PurposeThe purpose of this paper is to propose a new instantaneous torque control method for switched reluctance motor (SR motor) and presents experimental data in electric vehicle (EV) application.Design/methodology/approachThe proposed control method uses two kind of techniques: a flux‐based commutation technique prevents the negative phase torque always. On the other hand, a direct phase‐torque distribution technique gives suitable each phase‐torque command under limited DC voltage. These techniques can track motor torque to the command. These control schemes are implemented on a small processor and a field programmable gate array.FindingsThe experimental results of the EV show small torque ripple at low speed on both acceleration and regenerative braking. Changing the parameter of the current stop angle can improve torque ripple at high speed. The proposed method can effectively control motor torque.Practical implicationsThe proposed method can reduce torque ripple but the implementation is very simple. The proposed control method can be used for any applications. So, that contributes to expand the application of SR motors.Originality/valueThe proposed control scheme requires just static torque curve obtain by finite element analysis or simple experiments. Complex parameters, such as nonlinear inductance, current to torque profiles, and other heuristics parameters, are not necessary. The proposed control is simple but practical.
Forced dynamics control of PMSM drives with torsion oscillations
Authors: Vittek Ján , Briš Peter , Makyš Pavol , Štulrajter Marek 
Published: December 2009

PurposeThe purpose of this paper is to discuss the design and verification of a new control algorithm for the drive with permanent magnet synchronous motor (PMSM) and flexible coupling based on “Forced dynamics control”. Control laws are derived and tested for the rotor and load angle control and achieve non‐oscillatory position step response with a specified settling time.Design/methodology/approach“Forced dynamics control” is a new control technique based on feedback linearization which forces rotor or load position to follow demanded position with prescribed closed‐loop dynamics. The proposed control structure is developed in two steps: first, the feedback linearisation is applied to the rotor speed and then similar technique is used for position control loop.FindingsThe proposed controller is of the cascade structure, comprising an inner speed control loop, respecting vector control principles and outer position control loop designed to control the rotor or load angle, respectively. Estimates of load torques acting on the motor and load side as inputs of control algorithms are produced in observers and used to compensate disturbances offering a certain degree of robustness. Preliminary experiments confirm that proposed system follows the ideal closed‐loop dynamics with moderate accuracy.Research limitations/implicationsThe focus is on experimental verification of the position control of flexible PMSM drive with two position sensors and moderate precision, where the oscillations due to hardware setup, achieved sampling frequency and corresponding observers adjustment are limited up to 50 rad s−1.Practical implicationsThe designed control structure can substantially improve control performance of industrial plants subjects to torsion oscillations.Originality/valueExperimental results of a novel control structure for the PMSM drives with torsion oscillations are sufficiently promising and confirmed that the rotor and load angle responses follow the prescribed ones fairly closely.
Robust invariant set‐based protection of multi‐mass electrical drives
Authors: Vašak Mario , Perić Nedjeljko 
Published: December 2009

PurposeThe purpose of this paper is to elaborate a robust model‐based protective control algorithm for multi‐mass motor drives that are subjected to physical and safety constraints on their variables.Design/methodology/approachThe algorithm relies on the off‐line computed maximum robust controlled invariant set or its approximation for the given drive system and imposed constraints. It can be used to patch any existing drive control scheme with a firm constraints satisfaction guarantee. The online patch implementation is actually a simple correction of the control signal computed with the existing control scheme, with a mandatory state observer.FindingsPerformance of the patch is tested on a two‐mass drive system in combination with classical two‐mass drive speed controllers – P+I and reduced state controller. All constraints violations that exist in the presented responses obtained without the protection patch are suppressed by using the patch which shows the effectiveness of the approach. A brief implementation analysis shows that a digital signal processor could be used for online implementation of the controller with the protective patch.Originality/valueRobust invariant sets theory is efficiently and effectively used in a new application area – protection of multi‐mass electrical drives.
Common mode oscillations in electrical drive systems
Authors: Weidinger Thomas 
Published: December 2009

PurposeThe purpose of this paper is to present an analysis of common mode oscillations of several kilohertz in electrical drive systems. The analysed oscillations occur especially in electrical drive systems with active front end (AFE), common DC link and long motor cables and are independent of the well‐known reflection phenomenon. Owing to the resulting overvoltages, the motor isolation lifetime may be significantly reduced.Design/methodology/approachFor the analysis of the described problem, all parts of the common mode system of an electrical drive system are carefully modelled. This leads to an analysis of the frequency behaviour of the common mode system. The excitation mechanisms are also analysed and simulation in the time domain is performed to show the resulting overvoltages. Finally, measurements confirm the findings.FindingsThe investigations identified the reasons for the oscillations: the common mode system behaviour, including the common mode resonant behaviour of some special kinds of motor. Furthermore, the excitation mechanism is found to be dependent on the modulation schemes of the AFE and the inverters. Accordingly, a special remedy concerning the modulation is derived and compared to other known remedies. The results of the simulations show the good efficiency of the proposed remedy.Originality/valueThe presented results describe important basics for the development of electrical drive systems. By taking these issues into consideration, many unpredictable failures can be avoided.
Identification of electrical parameters in a power network using genetic algorithms and transient measurements
Authors: Dong Wei , Zanchetta Pericle , Thomas David W.P. 
Published: December 2009

PurposeThe knowledge of power network parameters (which are usually unknown or poorly quantified and cannot be measured directly) is very valuable for power system modelling, simulation, protection and control; since it is fundamental for solving many problems such as minimizing the effect of voltage distortion, active filter control or relay setting. The purpose of this paper is to develop a new, easy, effective and reliable method for power network parameters identification.Design/methodology/approachThe proposed identification method is based on current transient injections performed by a pulse width modulated power converter (which can be a rectifier or an active filter already installed in the network) and the analysis of the resultant network voltage response at the point of common coupling using genetic algorithms optimization.FindingsSimulation tests show the effectiveness of the proposed identification strategy achieving negligible errors, even in practical conditions when measurement noise is included. It is also a very flexible method since the optimization routine can be updated or modified in order to improve the performance.Originality/valueThe developed method is non‐invasive, and uses only hardware already present on the power system, identifying the single parameters rather than the total impedance. It will provide improvements to several areas of power quality control. For example, when used within a stand‐alone piece of instrumentation, it will be possible to build up mesh equivalent networks of unknown power and distribution systems, which can then be used for load flow studies, protection or harmonic penetration prediction.
A new control method in startup progress for power turbine generators as waste heat recovery system using an overall shipboard system model
Authors: Matsui Nobumasa , Kurokawa Fujio , Shiraishi Keiichi 
Published: December 2009

PurposeThe purpose of this paper is to present a new control method for a power turbine generator (PTG) as a waste heat recovery system using an overall shipboard system model that ascertains startup characteristics.Design/methodology/approachThe PTG system is a waste heat recovery‐type generation system making use of exhaust gas from the main shipboard diesel engines. With the PTG systems, control during startup is not entirely clear. Startup characteristics from power turbine startup through synchronization to the system bus are ascertained using an overall shipboard system model.FindingsA startup sequence control is clarified for a combination of gas valve operation and load bank. A prototype constructed on the basis of the simulation. As a result, in the startup process, so as to limit speed overshooting that is 0.83 p.u. at 100 percent output from main diesel engine as the severest condition. The synchronization to the system bus is attained, and highly satisfactory results are achieved.Originality/valueThe PTG is an extremely effective system for fuel cost reduction in the face of rising fuel prices, and systems capable of providing several thousand kilowatts are being considered.
Business schools in an age of globalization
Authors: Parker Lee D. , Guthrie James 
Published: December 2009

PurposeThe purpose of this paper is to consider the role of the business school now and in the future.Design/methodology/approachThe paper takes the form of an editorial review and argument.FindingsThe paper acknowledges the impact of globalization and “marketization” on business schools.Research limitations/implicationsThe editorial offers scope for accounting academics to engage with the university and protect against business school corporatization and/or privatization. This is an important issue in higher education, not only in Australia, but internationally.Originality/valueThe paper provides important empirical data and research information to scholars in the interdisciplinary accounting field of research about the future for business schools.