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hybrid-modeling
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Hybrid Modeling and Control of Voltage Source Inverters
, M.Sc. Thesis Sharif University of Technology ; Mokhtari, Hossein (Supervisor)
Abstract
Modeling and control of power electronic converters, due to their non-linear nature, are from important research subjects in power electronics. Power electronic systems contain both continuous-time dynamics and discrete-time inputs, and therefore, are categorized as hybrid systems. Conventionally, modeling and control of hybrid systems is done by linearizing and state-space averaging. However, these methods do not guaranty well operation of the system over a wide range of load or input variation. In this project, by employingMLD modeling method, a model for an inverter which is connected to a three-phase RL load through an LC filter, is derived. Then, this model is used in an optimization...
Estimation of Spinal Loads in Static Activities by Considering Trunk Muscle Forces in a Detailed Nonlinear Finite Element Model
, Ph.D. Dissertation Sharif University of Technology ; Arjmand, Navid (Supervisor) ; Shirazi-Adl, Aboulfazl (Co-Supervisor)
Abstract
Spine biomechanical models suffers from either simplification in passive disc components modeling (modeling via torsional spring or beam elements) in musculoskeletal (MS) models or shortcomings in detailed muscles modeling (via a simple force and torque vector) in detailed finite element (FE) models. Considering these, that is aimed in this study to develop a hybrid MS-FE model which the calculated muscle forces by a MS model (developed based on geometrical and mechanical properties of FE model) for a desired static posture, being applied to a detailed FE model. Considering the change of discs stiffness in FE model under the applied muscles and gravity forces, the equivalent stiffness in MS...
A comparative study of a hybrid logit-Fratar and neural network models for trip distribution: Case of the city of Isfahan
, Article Journal of Advanced Transportation ; Volume 45, Issue 1 , 2011 , Pages 80-93 ; 01976729 (ISSN) ; Shetab-Bushehri, S. N ; Poorzahedy, H ; Hejazi, S. R ; Sharif University of Technology
Abstract
This paper introduces a new procedure to forecast the future O/D demand. It is a hybrid of logit and Fratar model. The hybrid model has the long run, policy sensitive, characteristic of a logit model, calibrated at sector-level with little/no zero O/D cells. This feature, joint with a Fratar-type operation at zonal level within a sector, gives a better performance to this model than either of the two types of the models alone. The performance of the hybrid model is contrasted with a neural network model, and shows encouraging results in a real case
Control of pH processes using fuzzy modeling of titration curve
, Article Fuzzy Sets and Systems ; Volume 157, Issue 22 , 2006 , Pages 2983-3006 ; 01650114 (ISSN) ; Shahrokhi, M ; Sharif University of Technology
2006
Abstract
Model-based pH control is a difficult problem due to its inherent nonlinearity and time-varying characteristics. This is specially the case when the pH regulation of streams consisting hundreds of constituents with varying concentrations is desired. The pH process can be modeled by using conservation laws and neutrality condition. An alternative to this mechanistic modeling is using nonlinear empirical modeling such as fuzzy modeling. This paper proposes a new approach of fuzzy modeling of titration curves, which can be used for control purposes. The Takagi-Sugeno model was used for the modeling of titration curve. Two control algorithms, which are designed based on the titration curve,...
Optimization of Radiotherapy Plan under Uncertainty
, M.Sc. Thesis Sharif University of Technology ; Rafiee, Majid (Supervisor)
Abstract
As a method of cancer treatment or improvement of cancer-related complications, external radiation therapy is prescribed by physicians, in case of detection of a tumor in a region of patient’s body. Over time, various techniques have been developed for external beam radiation therapy. Among which, Intensity Modulated Radiation Therapy (IMRT), due to its ability to adjust the intensity of radiation beams, has a higher capacity to generate appropriate dose distribution based on tumor size and volume and it is one of the most widely used techniques in cancer treatment centers.The core process in treatment planning is using appropriate computer algorithms which results in posing enough damage to...
An MPC method based on a hybrid model of a three-phase inverter with output LC- filter
, Article 2012 3rd Power Electronics and Drive Systems Technology, PEDSTC 2012, 15 February 2012 through 16 February 2012 ; February , 2012 , Pages 170-174 ; 9781467301114 (ISBN) ; Mokhtari, H ; Sharif University of Technology
2012
Abstract
Controlling inverters with LC output filters in order to achieve a high quality desired output voltage or current is a challenging problem in power electronics. The LC filter and the binary nature of switch state variables increase the difficulty of achieving a single comprehensive model for the system. In this paper, a hybrid model is presented for a three-phase inverter with an LC output filter and a three-phase RL load. Then, the Model Predictive Control (MPC) algorithm is applied to the model and a geometrical approximate method is used to fit the answers to the binary values. Simulation results for a sample system verify the usability of the method and the quality of the answers
Improved iterative techniques to compensate for interpolation distortions
, Article Signal Processing ; Volume 92, Issue 4 , 2012 , Pages 963-976 ; 01651684 (ISSN) ; Ayremlou, A ; Akhaee, M. A ; Marvasti, F ; Sharif University of Technology
2012
Abstract
In this paper a novel hybrid algorithm for compensating the distortion of any interpolation has been proposed. In this Hybrid method, a modular approach was incorporated in an iterative fashion. The proposed technique features an impressive improvement at reduced computational complexity. The authors also extend the scheme to 2-D signals and actual (real) images and find that the solution exhibits great potential. Both the simulation results and mathematical analysis confirm the superiority of the Hybrid model over competing methods and demonstrate its robustness against additive noise
A hybrid model on severe plastic deformation of copper
, Article Computational Materials Science ; Volume 44, Issue 4 , 2009 , Pages 1107-1115 ; 09270256 (ISSN) ; Kazeminezhad, M ; Sharif University of Technology
2009
Abstract
A hybrid model based on the flow function and dislocation cell structure model by considering the Taylor assumption is utilized to model the dislocation structure evolution, cell size and mechanical properties of OFHC in severe plastic deformation. Here, the ECAP is chosen as a process of severe plastic deformation. In this study, the model is modified by taking the value of cell size coefficient as a function of strain and considering two different values of dynamic recovery coefficients of cell walls and cell interiors. These modifications lead to achieve the more accurate modeling results. From the flow function the strain rate distribution are achieved and then using the model the...
The Application of Simplified MDOF Models for Estimating the Moment Resisting Frames Seismic Demands in Endurance Time Method
, M.Sc. Thesis Sharif University of Technology ; Esmaeil Pourestekanchi, Homayoon (Supervisor)
Abstract
Modified Fish-Bone (MFB) Model and Consistent Generic (CG) Model are simplified Multi-Degrees-of-Freedom (MDOF) models, proven to be valuable tools in estimating seismic demands of moment-resisting frames, aimed to reduce the computational costs by decreasing the number of degrees of freedom. The preliminary expansion of these simplified models for steel moment resisting frames (SMRFs) were proposed by considering elastoplastic behavior and is not able to take into account stiffness and strength deteriorations in nonlinear dynamic behavior of structures. However, behavior deterioration affects seismic demands of SMRFs under intense earthquakes. For this reason, the present study is done to...
Data-driven Modeling of a Fermenter Using Flux Balance Analysis
, M.Sc. Thesis Sharif University of Technology ; Pishavie, Mahmoud Reza (Supervisor) ; Vafa, Ehsan (Supervisor)
Abstract
Optimization and control of complex bioprocesses require accurate modeling. The application of flux balance analysis has gained considerable attention. In this approach, structured modeling is constructed based on metabolic genome networks. Although flux balance analysis provides an accurate model, applying it in optimization and control schemes especially model predictive control strategies often lead to bilevel optimization problems with significant computational cost. Therefore, we require a faster approach. The aim of this work is to use hybrid neural networks as a substitute for the optimization problem embedded in the dynamic model of a fermenter. In this work by proposing a hybrid...
Hybrid modeling of a DC-DC series resonant converter: Direct piecewise affine approach
, Article IEEE Transactions on Circuits and Systems I: Regular Papers ; Volume 59, Issue 12 , 2012 , Pages 3112-3120 ; 15498328 (ISSN) ; Karimpour, A ; Pariz, N ; Tahami, F ; Sharif University of Technology
IEEE
2012
Abstract
A dc-dc resonant converter has the advantage of overcoming switching losses and electromagnetic interference which are the main limitations of high frequency power converters. Nevertheless, the modeling and stability analysis of dc-dc resonant converters are considerably more complex than pulsewidth modulation counterparts. The conventional averaged linearized model of the resonant converter has limitations due to averaging and linearization. First of all, the linearized model has large modeling error in presence of large variations of reference voltage and input voltage. Furthermore, Converging area for stabilizing controllers is smaller in the averaged model. In order to overcome these...
Developing a hybrid artificial intelligence model for outpatient visits forecasting in hospitals
, Article Applied Soft Computing Journal ; Volume 12, Issue 2 , 2012 , Pages 700-711 ; 15684946 (ISSN) ; Shavandi, H ; Ghanbari, A ; Abbasian Naghneh, S ; Sharif University of Technology
Abstract
Accurate forecasting of outpatient visits aids in decision-making and planning for the future and is the foundation for greater and better utilization of resources and increased levels of outpatient care. It provides the ability to better manage the ways in which outpatient's needs and aspirations are planned and delivered. This study presents a hybrid artificial intelligence (AI) model to develop a Mamdani type fuzzy rule based system to forecast outpatient visits with high accuracy. The hybrid model uses genetic algorithm for evolving knowledge base of fuzzy system. Actually it extracts useful patterns of information with a descriptive rule induction approach based on Genetic Fuzzy Systems...
Fuzzy rule extraction using hybrid evolutionary models for data mining systems
, Article 2011 International Symposium on Artificial Intelligence and Signal Processing, AISP 2011, 15 June 2011 through 16 June 2011 ; June , 2011 , Pages 25-30 ; 9781424498345 (ISBN) ; Abadeh, M. S ; Teshnehlab, M ; Nayyerirad, A ; Sharif University of Technology
2011
Abstract
Data mining is a very popular technique which is successfully used in many areas. The aim of this paper is to present a Hybrid model for data classification from input datasets. The proposed model extracts knowledge using fuzzy rule based systems and performs classification task by fuzzy if-then rules. The proposed method performs the classification task and extracts required knowledge using fuzzy rule based systems which consists of fuzzy if-then rules. In order to do so the hybrid ant colony and simulated annealing algorithms have been used to optimize extracted fuzzy rule set. "ACSA", a self development data mining software system based on swarm intelligence, is applied to experiment on...
Radial basis function network for exponential stabilisation of periodic orbits for planar bipedal walking
, Article Electronics Letters ; Volume 47, Issue 12 , 2011 , Pages 692-694 ; 00135194 (ISSN) ; Hamed, K.A ; Gruver, W. A ; Dumont, G. A ; Sharif University of Technology
2011
Abstract
Presented is a novel and analytical approach to design a hybrid controller based on hybrid zero dynamics for exponential stabilisation of a desired periodic orbit for a hybrid model of walking composed of single and double support phases. To achieve this goal, the effect of a double support phase on angular momentum transfer and stabilisation is investigated. Also, the class of control inputs corresponding to an orbit during double support is presented. A smooth feedback law based on a radial basis function network is then proposed for the double support phase such that (i) the desired orbit is exponentially stable and (ii) the control vector minimises the least square control cost
Misuse detection via a novel hybrid system
, Article EMS 2009 - UKSim 3rd European Modelling Symposium on Computer Modelling and Simulation, 25 November 2009 through 27 November 2009, Athens ; 2009 , Pages 11-16 ; 9780769538860 (ISBN) ; Abadeh, M. S ; Momenzadeh, A ; Pouyan, M. B ; Sharif University of Technology
Abstract
Intrusion detection systems (IDS) are tools located inside computer networks that analyze the network traffics. In this paper, a novel fuzzy-evolutionary system is presented to effectively detect the intrusion in computer networks. This system utilizes a hybridization of simulated annealing heuristic and tabu search algorithm to improve the accuracy of fuzzy if-then rules as intrusion detectors. Each of these algorithms has its advantageous and disadvantageous. Using the hybrid model of both algorithms, the proposed system employs the good features of them to improve the accuracy of obtained rules. Evaluation of the proposed system is done on the KDDCup99 Dataset which has information about...
Hybrid modeling of quasi-resonant converters: A piecewise affine approach
, Article 13th Power Electronics, Drive Systems, and Technologies Conference, PEDSTC 2022, 1 February 2022 through 3 February 2022 ; 2022 , Pages 448-454 ; 9781665420433 (ISBN) ; Tahami, F ; Sharif University of Technology
Institute of Electrical and Electronics Engineers Inc
2022
Abstract
DC-DC quasi-resonant converters (QRC) have the advantage of reducing switching losses and electromagnetic interference (EMI) which are the main disadvantages of high frequency power converters. The control and stabilization of these converters have always been a challenge. Traditionally, the dynamical model of the QRC is obtained using state space averaging followed by linearization about an operating point. The major flaw of this method is that state variables have large variations; thus, the linearized averaged model is not valid. Therefore, it is necessary to obtain a more precise model for the aim of stability analysis and controller design. Due to semiconductors switching, QRCs are...
RETRACTED ARTICLE: Hybridization of adaptive neuro-fuzzy inference system and data preprocessing techniques for tourist arrivals forecasting
, Article Proceedings - 2010 6th International Conference on Natural Computation ; Volume 4 , 2010 , Pages 1692-1695 ; 9781424459612 (ISBN) ; Shavandi, H ; Ghanbari, A ; Sharif University of Technology
IEEE Computer Society
Abstract
Intelligent solutions, based on artificial intelligence (AI) technologies, to solve complicated practical problems in various sectors are becoming more and more widespread nowadays, because of their flexibility, symbolic reasoning, and explanation capabilities. Meanwhile, accurate forecasts on tourism demand and study on the pattern of the tourism demand from various origins is essential for the tourism-related industries to formulate efficient and effective strategies on maintaining and boosting tourism industry in a country. In this paper we develop a hybrid AI model to deal with tourist arrival forecasting problems. The hybrid model adopts Adaptive Neuro-Fuzzy Inference System (ANFIS) and...
Global hybrid modeling and control of a buck converter: a novel concept
, Article International Journal of Circuit Theory and Applications ; Volume 37, Issue 9 , 2009 , Pages 968-986 ; 00989886 (ISSN) ; Mokhtari, H ; Sharif University of Technology
2009
Abstract
Several attempts have been made to design suitable controllers for DC-DC converters. However, these designs suffer from model inaccuracy or their inability to desirably function in both continuous and discontinuous current modes. This paper presents a novel switching scheme based on hybrid modeling to control a buck converter using mixed logical dynamical (MLD) methodologies. The proposed method is capable of globally controlling the converter in both continuous and discontinuous current modes of operation by considering all constraints in the physical plant such as maximum inductor current and capacitor voltage limits. Different loads and input voltage disturbances are simulated in MATLAB...
Solving haplotype reconstruction problem in MEC model with hybrid information fusion
, Article EMS 2008, European Modelling Symposium, 2nd UKSim European Symposium on Computer Modelling and Simulation, Liverpool, 8 September 2008 through 10 September 2008 ; 2008 , Pages 214-218 ; 9780769533254 (ISBN) ; Moeinzadeh, M. H ; Habibi, J ; Sharifian-R, S ; Rasooli-V, A ; Najafi-A, A ; Sharif University of Technology
2008
Abstract
Single Nucleotide Polymorphisms (SNPs), a single DNA base varying from one individual to another, are believed to be the most frequent form responsible for genetic differences. Genotype is the conflated information of a pair of haplotypes on homologous chromosomes. Although haplotypes have more information for disease associating than individual SNPs and genotype, it is substantially more difficult to determine haplotypes through experiments. Hence, computational methods which can reduce the cost of determining haplotypes become attractive alternatives. MEC, as a standard model for haplotype reconstruction, is fed by fragments as input to infer the best pair of haplotypes with minimum error...
Hybrid predictive control of a DC-DC boost converter in both continuous and discontinuous current modes of operation
, Article Optimal Control Applications and Methods ; Volume 32, Issue 3 , 2011 , Pages 270-284 ; 01432087 (ISSN) ; Mokhtari, H ; Sharif University of Technology
Abstract
Developing efficient and appropriate modeling and control techniques for DC-DC converters is of major importance in power electronics area and has attracted much attention from automatic control theory. Since DC-DC converters have a complex hybrid nature, recently several techniques based on hybrid modeling and control have been introduced. These techniques have shown better results as compared with conventional averaging-based schemes with limited modeling and control abilities. But the current works in this field have not considered all possible dynamics of the converters in both continuous and discontinuous current modes (CCM, DCM) of operations. These dynamics are results of controlled...