Nonlinear output feedback control of V2G single‐phase on‐board BEV charger

In this work, we consider the problem of controlling a single‐phase on‐board battery electric vehicle (BEV) charger with vehicle‐to‐grid (V2G) technology. The BEV charger consists of a bidirectional ac‐dc power converter connected to the single‐phase power grid, followed by a bidirectional dc‐dc power converter interfacing an EV battery pack. The main control objectives are fourfold: (i) Unitary Power Factor (UPF) in grid‐side; (ii) tight dc‐bus voltage regulation; (iii) safety battery charge and battery discharge during the grid‐to‐vehicle (G2V) mode and V2G mode, respectively; and (iv) asymptotic stability of the closed loop system. After an accurate system modelling, a nonlinear controller is designed using a backstepping design technique. The point is that the battery inner voltage is not accessible to measurement. Therefore, a nonlinear observer is invoked in order to estimate all non‐measured variables making the solution cheaper and noiseless. It is shown using a formal analysis and numerical simulations, that the proposed output feedback controller (combining a nonlinear controller and a nonlinear observer) meets all control objectives.     

The bond and flexural strengthening of reinforced concrete elements strengthened with near surface mounted prestressing steel (PS) bars

Abstract

The main objective of this work is to study the performance of prestressing steel (PS) bars as reinforcements in the reinforced concrete (RC) elements strengthened by the near-surface mounted method (NSM). The work includes two parts. In the first part, direct pull-out tests are performed in order to study the bond performance between PS reinforcement and concrete. The influences of groove sizes and PS surface conditions (smooth and sand coated) are evaluated. The results show that the sand coated PS (PS-Sc) reinforcement has the best adhesion behavior compared with the smooth bar, and its pull-out force is increased by 48%. For this reason, the PS-Sc bars are used in the second part of this work as NSM reinforcement to strengthen RC beams subjected to bending forces. Then, four-point bending tests are carried out to understand the flexural behavior of strengthened RC beams with PS-Sc reinforcements of different lengths and ratios. The obtained results demonstrate that the use of NSM-PS-Sc bars strengthening technique leads to important enhancement in the load carrying capacity of the RC beams. The first crack load and ultimate load of the strengthened RC beams attain 71.41 and 65.67%, respectively, which are higher than those of the control beam. Furthermore, the experimental values show a good agreement with the analytical values in both the ultimate deflection and the ultimate load. This proves that the NSM-PS-Sc bars studied in this work are promising reinforcement of the RC beams.     

Delay-dependent Stabilization Conditions of Controlled Positive Continuous-time Systems

The stabilization problem for a class of linear continuous-time systems with time-varying non differentiable delay is solved while imposing positivity in closed-loop. In particular, the synthesis of state-feedback controllers is studied by giving sufficient conditions in terms of linear matrix inequalities(LMIs). The obtained results are then extended to systems with non positive delay matrix by applying a memory controller. The effectiveness of the proposed method is shown by using numerical examples.     

Using genetic algorithm for lot sizing and scheduling problem with arbitrary job volumes and distinct job due date considerations

This paper considers an integrated lot sizing and scheduling problem for a production–distribution environment with arbitrary job volumes and distinct due dates considerations. In the problem, jobs are firstly batch processed on a batching machine at production stage and then delivered to a pre-specified customer at the subsequent delivery stage by a capacitated vehicle. Each job is associated with a distinct due date and a distinct volume, and has to be delivered to the customer before its due date, i.e. delay is not allowed. The processing time of a batch is a constant independent of the jobs it contains. In production, a constant set-up time as well as a constant set-up cost is required before the first job of this batch is processed. In delivery, a constant delivery time as well as a constant delivery cost is needed for each round-trip delivery between the factory and the customer. Moreover, it is supposed that a job that arrives at the customer before its due date will incur a customer inventory cost. The objective is to find a coordinated lot sizing and scheduling scheme such that the total cost is minimised while guaranteeing a certain customer service level. A mixed integer formulation is proposed for this problem, and then a genetic algorithm is developed to solve it. To evaluate the performance of the proposed genetic algorithm, a lower bound on the objective value is established. Computational experiments show that the proposed genetic algorithm performs well on randomly generated problem instances.     

Subcarrier and Power Allocation for the Downlink of Multiuser OFDM Transmission

In this paper, a new algorithm for subcarrier and power allocation for the downlink of multiuser OFDM transmission is presented. The proposed algorithm is more stable and it offers a lower complexity and better performance than previous existing algorithms. Khalid El Baamrani was born in Ouarzazate, Morocco in 1976. He received the License degree (equiv. B.A.) in electronic engineering from the University of Cadi Ayyad, Marrakech, Morocco, in 1998, the D.E.S.A. (equiv. M.A) in electrical engineering from the University of CadiAyyad, Marrakech, Morocco, in 2000, the certificate in engineering of the data-processing networks and telecommunications from the national institute of posts and telecommunications, Rabat, Morocco in 2002 and the Ph.D. degree at University of Cadi Ayyad, Marrakech, Morocco in 2005. His research interests include multicarrier modulation, communication theory, multiuser information theory, OFDM and DSL systems. Victor P. Gil Jiménez received the B. Eng. in Telecommunications with honors from University of Alcalá in 1998 and the M. Eng. in Telecommunications and the PhD. degree both from the University Carlos III de Madrid in 2001 and 2005, respectively. He is with the Department of Signal Theory and Communications at the University Carlos III de Madrid as an Assistant Professor. He worked at the Spanish Antarctica Base in 1999 as Communications Staff. He visited University of Leeds and Chalmers Technical University in 2003 and 2004 respectively. His research interests include multicarrier communications and signal processing for wireless systems. Ana Garcia Armada received the Telecommunication Engineer degree and the Ph.D in Electrical Engineering both from the Polytechnic University of Madrid (Spain) in 1994 and 1998, respectively. She is currently working as an Associate Professor at the University Carlos III de Madrid, where she has occupied several management positions. She has participated in several national and international research projects, most of them related to OFDM. She is coauthor of four books on wireless communications and signal processing. She has published 13 papers in international journals and more than 40 papers in conferences. She has contributed to international organizations such as ITU and ETSI. She has performed research stays in ESA-ESTEC, Kansas University, Stanford University and Bell Labs. Her research interests are simulation of communication systems, multicarrier and MIMO techniques.     

A New Approach in Optimizing the Induction Heating Process Using Flux Concentrators: Application to 4340 Steel Spur Gear

The beneficial effects of using flux concentrators during induction heat treatment process of spur gears made of 4340 high strength steel is demonstrated using 3D finite element model. The model is developed by coupling electromagnetic field and heat transfer equations and simulated by using Comsol software. Based on an adequate formulation and taking into account material properties and process parameters, the model allows calculating temperature distribution in the gear tooth. A new approach is proposed to reduce the electromagnetic edge effect in the gear teeth which allows achieving optimum hardness profile after induction heat treatment. In the proposed method, the principal gear is positioned in sandwich between two other gears having the same geometry that act as flux concentrators. The gap between the gear and the flux concentrators was optimized by studying temperature variation between the tip and root regions of gear teeth. Using the proposed model, it was possible identifying processing conditions that allow for quasi-uniform final temperature profile in the medium and high frequency conditions during induction hardening of spur gears.     

Accuracy enhancement of multi-axis CNC machines through on-line neurocompensation

This research is devoted to one of the most fundamental problems in precision engineering: machine tool accuracy. The paper presents a new approach designed to improve the accuracy of multi-axis CNC machines through software compensation of geometric, thermal and dynamic errors. Based on a multi-sensor monitoring system, the proposed compensation scheme is built to ensure error prediction. Four steps are required to develop and implement this system: (i) measurement of individual error components along each axis using a laser interferometer system, (ii) sensor integration via an artificial neural network model for on-line error estimation, (iii) synthesis of the total error into a three-dimensional error form using a simplified kinematic model and finally (iv) error compensation. Implemented on a turning center, the neurocompensation approach has improved machine accuracy by reducing the maximum error without compensation from 70 m without compensation to less than 4 m.     

Modeling the Effects of Strand Surface Bulging and Mechanical Softreduction on the Macrosegregation Formation in Steel Continuous Casting

Positive centerline macrosegregation is an undesired casting defect that frequently occurs in the continuous casting process of steel strands. Mechanical softreduction (MSR) is a generally applied technology to avoid this casting defect in steel production. In the current paper, the mechanism of MSR is numerically examined. Therefore, two 25-m long horizontal continuous casting strand geometries of industrial scale are modeled. Both of these strand geometries have periodically bulged surfaces, but only one of them considers the cross-section reduction due to a certain MSR configuration. The macrosegregation formation inside of these strands with and without MSR is studied for a binary Fe-C-alloy based on an Eulerian multiphase model. Comparing the macrosegregation patterns obtained for different casting speed definitions allows investigating the fundamental influence of feeding, bulging and MSR mechanisms on the formation of centerline macrosegregation.     

Simultaneous Observation of Melt Flow and Motion of Equiaxed Crystals During Solidification Using a Dual Phase Particle Image Velocimetry Technique. Part I: Stage Characterization of Melt Flow and Equiaxed Crystal Motion

A dual phase particle image velocimetry technique is applied to study the flow pattern during a combined equiaxed-columnar solidification process. This technique is able to measure simultaneously the liquid and the equiaxed grain velocity pattern within an academic Ammonium Chloride water ingot. After the formation of a steady convection pattern, solutal buoyancy together with falling crystals destabilize and break the steady convection flow into multiple chaotic cells. In the beginning of the solidification process, the flow transitioned from 2D to a 3D turbulent regime. The kinetic energy for the flow was calculated during the solidification process.     

Simultaneous Observation of Melt Flow and Motion of Equiaxed Crystals During Solidification Using a Dual Phase Particle Image Velocimetry Technique. Part II: Relative Velocities

A two-camera Particle Image Velocimetry (PIV) technique is applied to study the flow pattern and the equiaxed crystal motion during an equiaxed/columnar solidification process of Ammonium Chloride in a die cast cell. This technique is able to measure simultaneously the liquid and the equiaxed grain velocity pattern as already shown in Part I of this paper. The interaction between the equiaxed grains and the melt flow was explored by means of relative velocities. In single isolated configurations, the settling velocity of equiaxed crystal was found to be 41 times smaller than spheres of equivalent size. The coupling between the fluid flow and the equiaxed crystals was found to be important in areas of high crystal density. Chaotic and turbulent behaviors are found to be damped in regions of high equiaxed crystal density.