Isabela Roxana Birs

Bio: Isabela Roxana Birs 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 9, co-authored 51 publications receiving 288 citations. Previous affiliations of Isabela Roxana Birs include Control Group & Ghent University.

Approximation methods for FO-IMC controllers for time delay systems

Abstract: Fractional Order Internal Model Control (FO-IMC) is among the newest trends in extending fractional calculus to the integer order control. Approximation of the FO-IMC is one of the key problems. Apart from this, when dealing with time delay systems, the time delay needs also to be approximated. All these approximations can alter the closed loop performance of the controller. In this paper, FO-IMC controllers will be tested in terms of the approximation accuracy. The case study is a first order system with time delay. Several scenarios will be considered, aiming for a conclusion regarding the choice of the approximation method as a function of the process characteristics, closed loop performance and FO-IMC fractional order. To approximate the time delay, two extensively used techniques will be considered, such as the series and Pade approximations. These will be compared to a novel approximation technique. An analysis of the test cases presented show that the series approximation proves more suitable in a single scenario, whereas the novel approximation method produces better results for the rest of the test cases.

Alternative Approximation Method for Time Delays in an IMC Scheme

Abstract: Internal Model Control (IMC) algorithms have proven to be quite efficient in designing PID type controllers for time delay systems. However, to compute the equivalent PID controller in a feedback loop, using the IMC tuning approach, implies the approximation of the process time delay. Two of the most widely used approximation methods (first order or series and Pade) are used in this paper and compared to a new approximation method, the Non Rational Transfer Function (NRTF) approximation. In the current paper, the NRTF approximation is presented as an alternative method to the series/Pade approximation techniques for time delay systems in an IMC closed loop design. It is shown that for first order and second order processes, given a certain ratio of the IMC filter time constant and process time delay, the NRTF method could produce better closed loop dynamics, compared to the series/ Pade approximations. Several numerical examples are presented, as well as a case study.

Ergonomic and Economic Office Light Level Control

Abstract: Light regulation systems in industrial or office buildings play an important role in minimizing the use of fossil energy resources, while providing both economic and ergonomic optimal functionality. Although industrial buildings resolve the problem of interaction or disturbance mitigation by providing constant light levels exclusively from artificial sources, office landscapes may benefit from up to a 20% decrease in costs if mixed light sources are optimized properly. In this paper, we propose a theoretical framework based on model predictive control (MPC) to resolve a multi-system with strong dynamic interactions and multi-objective cost optimization. Centralized and distributed predictive control strategies are compared on various office landscaping structures and functionality conditions. Economic and ergonomic indexes are evaluated in a scaled laboratory setting.

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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Non-newtonian fluids.

Abstract: The Viscosity can be imagined as the force that should be applied to a layer of fluid belonging to the plane fixed to the velocity of the layer placed at a fixed distance. For example a fluid flowing in a tube at different speeds: the minimum speed is in the edge of the section (due to friction) and the maximum speed is at the center. The viscosity in this example is that pressure which is exerted on the wall allows a constant speed on the whole section.

Applications of Fractional Calculus

Abstract: Explicit formula and graphs of few special functions are derived in the paper on the basis of various definitions of various fractional derivatives and various fractional integrals. Their applications are also reviewed in the paper.