Sharif Digital Repository

In this paper, an attractive and novel algorithm for improving irreducible model identification of continuous time(CT) MIMO systems has been presented. The algorithm is based on least - squares (LS) estimates of Markov parameters (MP) using input output data and residual whitening. By choosing a linear-in-parameters model structure, the estimation becomes linear and asymptotically robust to zero-mean additive disturbances. CT Markov parameters may result in diverging approximations even for stable systems. To remove the existing limitations in the case of systems with low or zero damping, Markov Poisson parameters have been used to lend much flexibility to the estimation model. The MIMO... 

Fuel cells belong to an avant-garde technology family for a wide variety of applications including micro-power, transportation power, stationary power for buildings and other distributed generation applications. The first objective of this contribution is to find a suitable reduced model of a Solid Oxide Fuel Cell (SOFC). The derived reduced model is then used to design a state estimator. In the first step, the distributed model of the SOFC that is derived using the first principle balance equations is solved by the method of lines. Since this model is too complex and sluggish for real-time applications, a representation of this model with lower number of states and good accuracy is needed.... 

In this paper, some commonly used model reduction methods for integer-order systems are employed to approximate commensurate fractional-order linear systems. In comparison with the original system, the approximating model possesses a smaller inner dimension, while its fractional order is the same as that of the original system. The applied methods fall into the global reduction category, such as direct truncation and singular perturbation methods, and into the local reduction category, such as Pade approximation, partial realization, shifted Pade approximation, and rational interpolation methods. The applicability of these methods is illustrated by approximating a sample high-dimensional,... 

In this paper, an attractive and novel algorithm for improving irreducible model identification of continuous time(CT) MIMO systems has been presented. The algorithm is based on least - squares (LS) estimates of Markov parameters (MP) using input output data and residual whitening. By choosing a linear-in-parameters model structure, the estimation becomes linear and asymptotically robust to zero-mean additive disturbances. CT Markov parameters may result in diverging approximations even for stable systems. To remove the existing limitations in the case of systems with low or zero damping, Markov Poisson parameters have been used to lend much flexibility to the estimation model. The MIMO... 

A mathematical model is developed to investigate the reduction process of hematite in the reduction zone of the Midrex shaft furnace as a moving bed reactor. It is described as a counter-current moving bed cylindrical reactor in which hematite pellets are reduced by a gaseous mixture of hydrogen, water vapour, carbon dioxide and carbon monoxide, namely Syngas. It is laterally injected into the bed at the lower part close to the bottom. Governing equations, including continuity, momentum, energy and mass equations, are derived based on the conceptual model for both gas and solid phases in the cylindrical coordinate system. A three interface unreacted shrinking core model (USCM) is applied to... 

In the present work, multiple non existing model order reduction (MOR) techniques for unstable second-order form systems (SOSs) are proposed. For unstable SOSs, continuous-time algebraic Lyapunov equations get unsolvable that halt the reduction process. To avoid this problem, unstable SOS is first decomposed into stable and unstable portions and balanced truncation is applied to the stable part. The obtained reduced order model (ROM) for the stable portion is augmented with the unstable portion to obtain the overall reduced system. It is observed that the second-order structure in ROM for the first technique gets lost as well as augmented unstable dynamics degrade the ROM performance. To... 

In the present work, multiple non existing model order reduction (MOR) techniques for unstable second-order form systems (SOSs) are proposed. For unstable SOSs, continuous-time algebraic Lyapunov equations get unsolvable that halt the reduction process. To avoid this problem, unstable SOS is first decomposed into stable and unstable portions and balanced truncation is applied to the stable part. The obtained reduced order model (ROM) for the stable portion is augmented with the unstable portion to obtain the overall reduced system. It is observed that the second-order structure in ROM for the first technique gets lost as well as augmented unstable dynamics degrade the ROM performance. To... 

This paper utilizes data measured by phasor measurement units (PMUs) to extract a low-order dynamic equivalent model for power system stability studies. The estimated model is a 2-order model for synchronous machines. This model has the advantage of simplicity of classical model and considerably reduces the oversimplifying error of classical model. This method offers an alternative approach to analytical model reduction techniques based on the detailed system models. The proposed method uses the synchronized bus voltage and current phasors measured by PMUs. Using post disturbance data, electrical and mechanical parameters of the equivalent generator are estimated sequentially. Furthermore, a... 

This paper is a study on control of vibration of plate subjected to random vibration loading using magnetorheological (MR) dampers. Some key issues, i.e. model reduction, modeling of the MR dampers and their applications in vibration control of plates, are addressed in this work. MR dampers are semi-active devices that use MR fluids to produce a controllable damping with low power requirement. In this paper, first, a model reduction method for preparing a reduce order model (ROM) is presented. The method uses an optimal model truncation method which in it the ROM to be constructed such that it will provide the same frequency response characteristics as the original full model within the... 

Fractional order PI and PID controllers are the most common fractional order controllers used in practice. In this paper, a simple analytical method is proposed for tuning the parameters of these controllers. The proposed method is useful in designing fractional order PI and PID controllers for control of complicated fractional order systems. To achieve the goal, at first a reduction technique is presented for approximating complicated fractional order models. Then, based on the obtained reduced models some analytical rules are suggested to determine the parameters of fractional order PI and PID controllers. Finally, numerical results are given to show the efficiency of the proposed tuning... 

For microstructure modeling of copper wire after wire drawing process and annealing, an algorithm based on the Upper Bound Method and Potts Model is developed. In the algorithm, the Upper Bound Method is utilized to calculate the stored energy distribution in the drawn wire and then the stored energy is used in the Potts Model to obtain the grain size distribution of the drawn wire after annealing. The microstructure modeling is carried out at different deformation and annealing conditions. In all of the conditions, the fine and coarse grains are achieved at the surface and center of the wire, respectively. Also, the grain size of the drawn wire after annealing is decreased with increasing...