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.

Analysis of a new continuous-to-discrete-time operator for the approximation of fractional order systems

Abstract: One of the methods for discrete-time approximation of fractional order systems consists in an indirect approach in which a continuous-time rational transfer function is firstly derived. Then, using different mapping techniques, the s plane transfer function is converted to the z plane. In this paper a new mapping technique is proposed. The tuning parameter of this continuous-to-discrete-time mapping operator balances the discrete-time approximation between the classical Euler and Tustin rules, ensuring an increased flexibility compared to these classical methods. An analysis of the effects of the changes in this parameter is given, along with some general guidelines for its proper selection. The authors show that for digital approximation of fractional order systems using the indirect approach, Tustin rule can lead to ringing and should be avoided. The inverse discrete-to-continuous time operator is also presented. Numerical examples are provided. The results show that high accuracy of approximation is obtained and that the proposed method can be considered as a suitable solution, compared to classical discretization methods (Tustin).

Microcontroller Implementation of a Multivariable Fractional Order PI Controller

Abstract: Fractional order calculus has been used intensively to control various types of processes. The main approaches towards fractional order controllers focus on the single-input-single-output systems. The general design procedure consists in a frequency domain specification of various performance criteria followed by optimization routines. The implementation issues regarding fractional order controllers are based on Oustaloup approximations and are centered on SISO processes. The present paper addresses the problem of implementing on a microcontroller a fractional order multivariable controller for time delay processes. The paper presents a tuning algorithm for determining the parameters of the multivariable fractional order controller and the implementation issues. The multivariable time delay process is implemented in Matlab Simulink environment. The experimental results show that the fractional order multivariable controller implemented on a simple microcontroller provides similar results to that obtained by simulation, even under uncertainty conditions.

Analytical modeling and preliminary fractional order velocity control of a small scale submersible

Abstract: This paper presents the modeling and control of a small scale submersible equipped with one propeller. The modeling process takes into consideration physical elements such as fluid statics, viscous damping and propulsive thrust. A first order transfer function with time delay is developed to make the connection between the voltage applied to the motor actuating the propeller and the velocity of the submersible. The velocity control is realized with a Fractional Order Proportional Integral (FOPI) controller that ensures zero steady state error. The controller is designed based on frequency domain specifications such as gain crossover frequency, phase margin and robustness to gain variations. The obtained fractional controller is validated through simulation in terms of steady state error and disturbance rejection performance.

Anesthesia regulation: Towards completing the picture

Abstract: This paper introduces for the first time in literature the complete picture of depth of anesthesia regulatory paradigm. The simulation model proposes to include not only the three anesthesia features: hypnosis, analgesia and neuromuscular blockade, but also to introduce the interaction with the hemodynamic system (cardio-regulatory loops). Disturbances occurring in the operation theatre origin from surgical stimulation, for which profiles are available. A novel addition is the model of nociceptor pathway, recently developed and thus available for analysis. The nociceptor pathway model makes the link between the surgical stimulation and the perception to the patient of its effect. In conclusion, this paper presents a nonlinear multiple input multiple output model for further development of control algorithms in this application field.

Experimental results of a fractional order PD λ controller for vibration suppresion

Abstract: Vibration occurs in numerous important domains, such as the aerospace industry, and has negative effects since it can limit the life span of the devices, cause malfunctioning or even system instability. The necessity of research on vibration suppression in aeroplane wings is important from a scientific and technologic point of view: to provide better, more efficient, robust, cheaper solutions to eliminate vibrations effects, which triggers the socioeconomic aspect regarding the increase of flight safety and passenger comfort. Vibration suppression can be achieved using passive techniques, but they come along with certain disadvantages related to efficiency/costs. An alternative solution is to use active control. Several active control strategies have been proposed so far, with aeroplane wings/helicopter blades simulated as smart cantilever beams. The present paper proposes a fractional order Proportional Derivative controller, designed using frequency domain specifications. The case study consists in a smart beam equipped with dedicated sensors and actuators. The experimental results, considering both passive and active control responses of the smart beam, show that the proposed method leads to significant improvement of the closed loop behavior.

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.