Cristina I. Muresan

Bio: Cristina I. Muresan is an academic researcher from Technical University of Cluj-Napoca. The author has contributed to research in topics: PID controller & Control theory. The author has an hindex of 14, co-authored 122 publications receiving 1046 citations. Previous affiliations of Cristina I. Muresan include Core Laboratories.

Experimental Validation of an Efficient Disturbance Rejection Method for Dead-Time Processes using Internal Model Control

Abstract: When controlling industrial processes, setpoint tracking and disturbance rejection play an important part in the design and tuning of the PID controller parameters, especially since most of these processes exhibit dead-times. Internal Model Control (IMC) algorithms have proven to be quite efficient in setpoint tracking issues. However, the basic tuning rules for IMC lead to PID controllers that cause a sluggish disturbance rejection, especially for delay dominant processes (i.e. with big ratio of dead-time versus the process time constant). In the current paper, the experimental validation of a novel idea for tuning IMC controllers for improved disturbance rejection is presented. The method is based on using a disturbance filter that compensates for the dead-time, provided that the process is affected by stochastic disturbances having their spectral energy in a narrow frequency band (such as quasi-periodic disturbances). Diophantine equations are used to compute the disturbance filter coefficients. The exaperimental case study consists in the Quanser six tanks process.

Tuning Method of Fractional Order Controllers for Vibration Suppression in Smart Structures

Abstract: Vibration suppression is a major problem in various domains, with applications ranging from medical devices to aerospace engineering Several methods for suppressing vibrations have been proposed, but very few address this issue from the fractional calculus perspective The emerging new fractional order controllers have the ability to meet more design specifications at the same time, behaving robustly against modeling uncertainties, external disturbances, etc In this paper, a new tuning method for fractional order PDµ controller is proposed in which the design directly addresses the problem of suppressing resonance frequency vibrations The case study consists in an unloaded smart beam The simulation results, considering an additional situation of the loaded smart beam, show that the proposed method is simple and leads to a robust closed loop behavior

Fractional order IMC based controller for time delay systems

Abstract: In this paper a novel control strategy implying a Smith Predictor structure is proposed for which the primary controller is tuned based on the IMC method, but altered such that the final primary controller is a fractional order controller. A first order time delay process is used as a case study. The simulation results show that the proposed fractional order IMC controller ensures improved closed loop performance compared to the classical IMC, especially in terms of modeling uncertainties.

Improving performance for a 13 C isotope separation plant using multivariable fractional order controllers

Abstract: High purity 13C isotope is widely used in numerous areas of medicine, including tests to evaluate metabolism problems, ulcer diagnostics, studies of amino-acids kinetics and especially to highlight metabolic changes in the human brain that help diagnose earlier important diseases such as Alzheimer and other neuropsychiatric abnormalities. It is for this particular reason that efficient methods for separating and enriching the 13C isotope are widely sought. One of these methods is the cryogenic distillation of the two stable carbon isotopes, 12C and 13C. However, due to the low separation factor (1.007 at -194°C) a single distillation column is not enough to raise the natural concentration of 13C from its original 1.1% to 90% Therefore, cascaded columns are generally required. Nevertheless, such complex equipment involves the individual control of each column and also a supervisory control of the entire cascade. Prior to the design of a supervisory control system, the individual control of each column has to be developed. Due to the modeling errors, the variable time delays, the multivariable nature, strong couplings and interactions and also because any deviation of the process outputs from the prescribed set-points might lead to compromising the entire separation process, a robust control algorithm should be employed. Fractional order controllers have proven to be an interesting approach towards solving the problem of closed loop robustness. It is therefore one of the choices for controlling the 13C isotope separation column. In this paper, the authors design and compare two multivariable controllers, a fractional order controller and its integer counterpart. The simulation results show that the multivariable fractional order controller outperforms the classical one, and represents a simple and robust choice for raising the concentration of 13C.

I and i

Abstract: There is, I think, something ethereal about i —the square root of minus one. I remember first hearing about it at school. It seemed an odd beast at that time—an intruder hovering on the edge of reality. Usually familiarity dulls this sense of the bizarre, but in the case of i it was the reverse: over the years the sense of its surreal nature intensified. It seemed that it was impossible to write mathematics that described the real world in …

Formulas For Natural Frequency And Mode Shape

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Utilizing Electric Vehicles for LFC in Restructured Power Systems Using Fractional Order Controller

Abstract: Introduction of vehicle-to-grid technology offer electric vehicles (EVs) to participate in different ancillary services under competitive electric market. EVs provide an opportunity to grow new products and services for grid management. Particularly, EVs, which is a new form of distributed energy storage, can be used to compensate the uncontracted power in the local area if the contracts between the market players are violated. This paper presents the participation of EVs for load frequency control (LFC) under deregulated environment along with other conventional sources such as hydro, thermal, and gas turbine units. An aggregate model of EV fleets and improved version of fractional order (FO) controller is provided in all the areas for robust LFC considering bilateral transactions. Flower pollination algorithm, which is one of the new proven nature inspired algorithm employed to choose the optimal parameters of the FO controllers under several scenarios. Numerous simulations are conducted to validate the superiority of the proposed control strategy.