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Showing 4 results for Parameter Identification
Identification of Lorenz chaotic system based on synchronization using fractional order calculus
Mehdi Gomroki, Mohammad Abedini, Hassan Salarieh, Ali Meghdari,
Volume 14, Issue 7 (10-2014)
Abstract
In this paper the goal is to identify the parameters of the Lorenz chaotic system, based on synchronization of identical systems using fractional calculus. The method which is used for synchronization is come from Lyapunov stability theorem and then by using fractional dynamics, control laws are improved. To this end, a Lyapunov function is presented and based on the Lyapunov stability theory and asymptotic stability criteria, some adaptation laws to estimate unknown parameters of the system are proposed. The introduced method is applied to the Lorenz chaotic system and since the goal is identification, all the parameters of the system are taken unknown. Using invariant set theory, it is proved that the parameter estimation errors converge to zero. Then the results of numerical simulations are shown and discussed and it is observed that fractional calculus has an essential effect on reducing fluctuations and settling time of the parameters convergence. At the end, the stability of the system by using fractional adaptation law is discussed. It is shown that the asymptotic stability of the synchronization error dynamics is proved using the fractional adaptation law, and this is confirmed through simulation.
A New Approach for Finite Element Model Updating of Bolted Joints and Comparison with Interface Layer Method
Saeed Shokrollahi, Hamid Ahmadian, Farhad Adel,
Volume 16, Issue 3 (5-2016)
Abstract
In this paper, a new model called connective layer is developed for simulation of linear dynamical behavior of bolted lap joints and model updating in 3D models. Connective layer unifies neighboring zones on sides of common surfaces of substructures in joint region. The constitutive relation of connective elements is defined by decomposing it into its normal and shear components. Unknown and different elastic properties with respect to the neighboring solid elements are defined for connective layer and the unknown parameters of the model are identified by a finite element model updating technique using modal test data. The frequency response of the structure is measured by exciting the structure using an impact hammer. Using an optimization algorithm in ANSYS, the difference between the experimentally measured frequencies and the predictions of the parametric model is minimized as objective function. The connective element performance is demonstrated by application to an actual structure containing a single lap bolted joint coupling two identical aluminum alloy 7075-T651 beams and finally comparison of results to those of interface elements. The outcomes of presented model have good correlation with experimental results. The proposed method predicts the higher mode frequencies which don’t have participation in model updating process with minimum error in comparison to those of interface element. Due to simplicity, accurate and computationally efficient manner, this model can be incorporated into commercial finite element codes to simulate bolted joints in large and complex structures.
Kinetic Modeling and Parameters Identification Based on Metaheuristic Optimization Techniques for Extraction Process of Marrubium vulgare L. Essential Oil

Volume 19, Issue 2 (3-2017)
Abstract
Recently, increasing attention has been directed to the isolation of natural active components from various medicinal plants. In the present research, the extraction of essential oil from horehound (M. vulgare L.) is presented. Effects of mass ratio and particle size on the process performance were studied and kinetics were determined. The chemical composition of the volatiles present in M. vulgare L. was evaluated for the sample extracted in the optimum conditions (mass ratio, 3 kg/m3 and particle size,0.1
Identification of Parameters of Spencer Model for a Double-Ended Magnetorheological Damper with Different Spherical Iron Carbonyl Powder Sizes
M. Mousazadeh, K. Jahani, M. Abdollahi,
Volume 19, Issue 5 (5-2019)
Abstract
The aim of this paper is identifying the parameters of for a double-ended magnetorheological damper with different sizes of iron- powders suspended in magnetorheological fluid. There is not any published work in literature about identification of parameters of spherical iron particles with different particle diameters in magnetorheological fluids. Hence, in at first, two different magnetorheological fluids with different diameters of iron particle and same volume percentage are prepared. Then, using a double-ended magnetorheological damper, dynamic displacement tests with harmonic excitation in different frequencies and using different electric currents are conducted. The parametric Spencer model is selected for modeling the damper and identifying its parameters. 10 parameters of this model are identified, using nonlinear least square solver and implementing for damper, using two different magnetorheological fluids in different frequencies and different electric currents. The appropriate polynomials are extracted for parameters that have systematic trends with increasing electric current. experimental hysteresis curves in different electric currents, excitation frequencies and different fluids, it is to assess the capability of Spencer model in regenerating the experimental counterparts. The comparisons of the hysteresis curves obtained from with identified parameters by the experimentally achieved counterparts show that this model has adequate compatibility with experiments in predicting force-velocity hysteresis curves. However, the implemented model has not enough success in predicting the force-displacement hysteresis curves, especially in sharp ends of the curves and force delaying regions.

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