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.

Fractional-Order PID Controller Based on Immune Feedback Mechanism for Time-Delay Systems

Abstract: The control of processes with time delays is crucial in process industries such as petrochemical, hydraulic, and manufacturing. It is a challenging task for automation engineers, as it may affect both phase and gain margins. In this case, a robust control system is preferred. This article presents a novel controller structure combining computational intelligence (CI) and fractional-order control. A fractional-order PID (FOPID) controller based on a bio-inspired immune feedback mechanism (IFM) is developed for controlling processes described as first-order plus time-delay systems (FOPTD). A genetic algorithm (GA) is used to optimize the controller parameters. Fractional-order control has been used to give extra flexibilities and an immune feedback mechanism for its self-adaptability. Numerical simulations are presented to validate the proposed control strategy in terms of reference tracking and disturbance rejection. Comparative simulation results with an immune integer-order PID controller are also included to demonstrate the efficiency of the proposed fractional-order method.

Model Identification and Control of Electromagnetic Actuation in Continuous Casting Process With Improved Quality

Abstract: This paper presents an original theoretical frame-work to model steel material properties in continuous casting line process. Specific properties arising from non-Newtonian dynamics are herein used to indicate the natural convergence of distributed parameter systems to fractional order transfer function models. Data driven identification from a real continuous casting line is used to identify model of the electromagnetic actuator device to control flow velocity of liquid steel. To ensure product specifications, a fractional order control is designed and validated on the system. A projection of the closed loop performance onto the quality assessment at end production line is also given in this paper.

Design and experimental validation of an optimal fractional order controller for vibration suppression

Abstract: In this paper, a fractional order optimal controller is designed, tested and validated experimentally for seismic mitigation in a one floor structure. The design is based on a two-step optimization procedure. The first step is concerned with the computation of the classical optimal controller gains. A second step follows that deals with the computation of an optimal fractional order parameter value that minimizes the attenuation level. The designed controller is implemented and tested experimentally on a laboratory scale civil structure. For comparison purposes, the passive seismic mitigation case is also considered, as well as the active case using the traditional optimal controller. The closed loop experimental results show that the designed fractional order optimal controller can ensure an improved attenuation level in the occurrence of a seismic event in comparison to the classical optimal controller.

Stabilizing control strategies: A comparison between the fractional order controller and the IMC

Abstract: Magnetic levitation systems are widely used in practice and especially as a research topic due to their nonlinear and unstable characteristics. In this paper, two rarely used control algorithms for unstable systems are proposed: a special type of a fractional order controller and an IMC (Internal Model Control) based controller. The two control algorithms are compared and tested on an experimental laboratory scale magnetic levitation system. The results show that both control strategies may be used as a viable option for controlling such types of systems, with the fractional order controller ensuring a better closed loop performance in comparison with the IMC algorithm. Robustness issues are also addressed, with the fractional order controller turning out to be an adequate alternative to compensate for modeling uncertainties and variable process parameters.

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.