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    Variation source identification of multistage manufacturing processes through discriminant analysis and stream of variation methodology: A case study in automotive industry

    , Article Journal of Engineering Research ; Volume 3, Issue 2 , July , 2015 , Pages 96-108 ; 23071885 (ISSN) Bazdar, A ; Baradaran Kazemzadeh, R ; Akhavan Niaki, S. T ; Sharif University of Technology
    University of Kuwait  2015
    Product quality problem is a critical issue for multistage manufacturing processes, especially in continuous production lines whereby quality characteristics are measured at the end of the line. Therefore, it is important to reduce process variation by identifying its sources and eliminating its causes. In this regard, a novel approach, to identify the source of variation in multistage manufacturing processes through integration of the Fisher's linear discriminant analysis and the stream of variation methodology, is proposed. Linear discriminant analysis is used to separate the variation of quality characteristics through the different stages of the manufacturing processes while the stream... 

    Noise reduction of speech signal using bayesian state-space Kalman filter

    , Article 2013 19th Asia-Pacific Conference on Communications, APCC 2013 ; August , 2013 , Pages 545-549 ; 9781467360500 (ISBN) Sarafnia, A ; Ghorshi, S ; Sharif University of Technology
    IEEE Computer Society  2013
    The noise exists in almost all environments such as cellular mobile telephone systems. Various types of noise can be introduced such as speech additive noise which is the main factor of degradation in perceived speech quality. At some applications for example at the receiver of a telecommunication system, the direct value of interfering noise is not available and there is just access to noisy speech. In these cases the noise cannot be cancelled totally but it may be possible to reduce the noise in a sensible way by utilizing the statistics of the noise and speech signal. In this paper the proposed method for noise reduction is Bayesian recursive state-space Kalman filter, which is a method... 

    A unified optimization-based framework to adjust consensus convergence rate and optimize the network topology in uncertain multi-agent systems

    , Article IEEE/CAA Journal of Automatica Sinica ; Volume 8, Issue 9 , 2021 , Pages 1539-1548 ; 23299266 (ISSN) Sarafraz, M. S ; Tavazoei, M. S ; Sharif University of Technology
    Institute of Electrical and Electronics Engineers Inc  2021
    This paper deals with the consensus problem in an uncertain multi-agent system whose agents communicate with each other through a weighted undirected (primary) graph. The considered multi-agent system is described by an uncertain state-space model in which the involved matrices belong to some matrix boxes. As the main contribution of the paper, a unified optimization-based framework is proposed for simultaneously reducing the weights of the edges of the primary communication graph (optimizing the network topology) and synthesizing a controller such that the consensus in the considered uncertain multi-agent system is ensured with an adjustable convergence rate. Considering the NP-hardness... 

    Continuous-time state-space unsteady aerodynamic modeling based on boundary element method

    , Article Engineering Analysis with Boundary Elements ; Volume 36, Issue 5 , 2012 , Pages 789-798 ; 09557997 (ISSN) Mohammadi Amin, M ; Ghadiri, B ; Abdalla, M. M ; Haddadpour, H ; De Breuker, R ; Sharif University of Technology
    In this paper a continuous-time state-space aerodynamic model is developed based on the boundary element method. Boundary integral equations governing the unsteady potential flow around lifting bodies are presented and modified for thin wing configurations. Next, the BEM discretized problem of unsteady flow around flat wing equivalent to the original geometry is recast into the standard form of a continuous-time state-space model considering some auxiliary assumptions. The system inputs are time derivative of the instantaneous effective angle of attack and thickness/camber correction terms while the outputs are unsteady aerodynamic coefficients. To validate the model, its predictions for... 

    Sensor selection cost optimisation for tracking structurally cyclic systems: a P-order solution

    , Article International Journal of Systems Science ; Volume 48, Issue 11 , 2017 , Pages 2440-2450 ; 00207721 (ISSN) Doostmohammadian, M ; Zarrabi, H ; Rabiee, H. R ; Sharif University of Technology
    Measurements and sensing implementations impose certain cost in sensor networks. The sensor selection cost optimisation is the problem of minimising the sensing cost of monitoring a physical (or cyber-physical) system. Consider a given set of sensors tracking states of a dynamical system for estimation purposes. For each sensor assume different costs to measure different (realisable) states. The idea is to assign sensors to measure states such that the global cost is minimised. The number and selection of sensor measurements need to ensure the observability to track the dynamic state of the system with bounded estimation error. The main question we address is how to select the state... 

    Fault diagnosis within multistage machining processes using linear discriminant analysis: a case study in automotive industry

    , Article Quality Technology and Quantitative Management ; Volume 14, Issue 2 , 2017 , Pages 129-141 ; 16843703 (ISSN) Bazdar, A ; Baradaran Kazemzadeh, R ; Akhavan Niaki, S. T ; Sharif University of Technology
    Taylor and Francis Ltd  2017
    Statistical process control provides useful tools to improve the quality of multistage machining processes, specifically in continuous manufacturing lines, where product characteristics are measured at the final station. In order to reduce process errors, variation source identification has been widely applied in machining processes. Although statistical estimation and pattern matching-based methods have been utilized to monitor and diagnose machining processes, most of these methods focus on stage-by-stage inspection using complex models and patterns. However, because of the existence of high rate alarms and the complexity of the machining processes, a surrogate modelling is needed to solve... 

    Particle filtering-based low-elevation target tracking with multipath interference over the ocean surface

    , Article IEEE Transactions on Aerospace and Electronic Systems ; Volume 56, Issue 4 , 2020 , Pages 3044-3054 Shi, X ; Taheri, A ; Cecen, T ; Celik, N ; Sharif University of Technology
    Institute of Electrical and Electronics Engineers Inc  2020
    As radar signals propagate above the ocean surface to determine the trajectory of a target, the signals that are reflected directly from the target arrive at the receiver along with indirect signals reflected from the ocean surface. These unwanted signals must be properly filtered; otherwise, their interference may mislead the signal receiver and significantly degrade the tracking performance of the radar. To this end, we propose a low-elevation target tracking mechanism considering the specular and diffuse reflection effects of multipath propagation over the ocean surface simultaneously. The proposed mechanism consists of a state-space model and a particle filtering algorithm and promises... 

    Implementation of Bayesian recursive state-space Kalman filter for noise reduction of speech signal

    , Article Canadian Conference on Electrical and Computer Engineering ; 2014 Sarafnia, A ; Ghorshi, S ; Sharif University of Technology
    Noise reduction of speech signals plays an important role in telecommunication systems. Various types of speech additive noise can be introduced such as babble, crowd, large city, and highway which are the main factor of degradation in perceived speech quality. There are some cases on the receiver side of telecommunication systems, where the direct value of interfering noise is not available and there is just access to noisy speech. In these cases the noise cannot be cancelled totally but it may be possible to reduce the noise in a sensible way by utilizing the statistics of the noise and speech signal. In this paper the proposed method for noise reduction is Bayesian recursive state-space... 

    The employment of Bayesian method in noise: Reduction and packet loss replacement

    , Article Proceedings Elmar - International Symposium Electronics in Marine ; 2013 , Pages 207-210 ; 13342630 (ISSN); 9789537044145 (ISBN) Rahimi, A ; Ghorshi, S ; Sarafnia, A ; Sharif University of Technology
    Speech enhancement in real-time applications improves the quality and intelligibility of the speech and reduces communication fatigue. Nowadays, due to reactivity of the systems and spread of online real-time applications, including VoIP, state-space models have been used broadly. This paper presents a speech enhancement method based on adaptive Bayesian-Kalman filter and Bayesian-MAP estimation to improve the performance and the quality of the enhancement procedure. The enhancement method includes a combination of Bayesian-Kalman filter for noise reduction and Bayesian-MAP estimation for parameter estimation of the lost speech segments. Performance evaluation and result of the proposed... 

    Design a LQG power system stabilizer for bistun power plant

    , Article AUPEC'09 - 19th Australasian Universities Power Engineering Conference: Sustainable Energy Technologies and Systems, 27 September 2009 through 30 September 2009, Adelaide ; 2009 ; 9780863967184 (ISBN) Keivanian, R ; Hossein Vahabie, A ; Nademi, H ; Ranjbar, A ; Sharif University of Technology
    Design of a classical controller is based on output feedback and structure of the controller. From modern control point of view, the information of input signals, output signals and internal behavior of the system are presented in state space model. In this paper, modern control is used to increase small-disturbance stability of power systems. Although many of existing power plants prefer to use classical Power System Stabilizers (PSS), these controllers have their own problems. Digital implementation of modern controllers is considered as a good advantage of modern PSS. In this paper, a modern control based PSS is designed for Bistun power plant and its output results are compared to the... 

    A model aided inertial navigation system for automatic landing of unmanned aerial vehicles

    , Article Navigation, Journal of the Institute of Navigation ; Volume 65, Issue 2 , June , 2018 , Pages 183-204 ; 00281522 (ISSN) Mohammadkarimi, H ; Nobahari, H ; Sharif University of Technology
    Wiley-Blackwell  2018
    The use of Model Aided Inertial Navigation (MAIN) during the landing of an Unmanned Aerial Vehicle (UAV) is investigated. A new MAIN algorithm is proposed, which is fast and accurate enough to be used in automatic landing. In this algorithm, the six Degree of Freedom (6DoF) model of the UAV is tightly coupled with the inertial navigation system; thus, the 6DoF model acts as an aiding system for the INS and vice versa. In the last parts of the landing phase in proximity of Earth, the proposed algorithm also estimates and removes the Ground Effect (GE) uncertainties and provides the height controller with a realistic model. An adaptive controller based on a parametric state-space model is used... 

    Decentralized model predictive voltage control of islanded DC microgrids

    , Article 11th Power Electronics, Drive Systems, and Technologies Conference, PEDSTC 2020, 4 February 2020 through 6 February 2020 ; 2020 Abbasi, M ; Mahdian Dehkordi, N ; Sadati, N ; Sharif University of Technology
    Institute of Electrical and Electronics Engineers Inc  2020
    This paper proposes a novel decentralized control approach for islanded direct-current (DC) microgrids (MGs) based on model predictive control (MPC) to regulate the distributed generation unit (DGU) output voltages, i.e. the voltages of the point of common coupling (PCC). A local controller is designed for each DGU, in the presence of uncertainties, disturbances, and unmodeled dynamics. First, a discrete-time state-space model of an MG is derived. Afterward, an MPC algorithm is designed to perform the PCC voltage control. The proposed MPC scheme ensures that the PCC voltages remain within an acceptable range. Several simulation studies have been conducted to illustrate the effectiveness of... 

    Dual Lagrangian modeling and Lyapunov-based control of three-level three-phase NPC voltage-source rectifier

    , Article 2012 11th International Conference on Environment and Electrical Engineering, EEEIC 2012, Venice, 18 May 2012 through 25 May 2012 ; 2012 , Pages 737-743 ; 9781457718281 (ISBN) Mehrasa, M ; Ahmadigorji, M ; Abedi, A ; Sharif University of Technology
    IEEE  2012
    The load current of three level/phase neutral point clamped rectifier could be expressed in two forms: the load current involving the current of capacitor C1, and the load current involving the current of capacitor C2. Using the Euler-Lagrange model based on the superposition law and the obtained load current, a new dual Lagrangian model of the rectifier is founded in this paper and then the two obtained nonlinear state space models are developed in dq0 reference frame. According to the new model, two positive definite Lyapunov function candidates are defined and a Lyapunov-based control is applied to the rectifier. Each of the function is utilized to control its corresponding output voltage...