Andrzej Tutaj

Bio: Andrzej Tutaj is an academic researcher from AGH University of Science and Technology. The author has contributed to research in topics: Control theory & Control system. The author has an hindex of 4, co-authored 21 publications receiving 53 citations.

Analog realization of fractional filters: Laguerre approximation approach

Abstract: Fractional filters are attractive tools for signal processing allowing greater flexibility in shaping the frequency response. Unfortunately they are very difficult to realize directly, as for digital approach they require infinite memory and for analog approach they require fully fractional capacitors or inductors. That is why approximation approaches are so attractive. In this paper we present a method of implementing an analog approximation of fractional filter. Our approach is based on Laguerre Impulse Response Approximation method. We present its modification allowing reduction of the required connections and without problems with signal-to-noise ratios. Our results are illustrated both with simulations and with experiments.

Improving quality of control in networked control systems by co-design of sampling period and buffer size

Abstract: The paper studies the control of networked control systems (NCS) with sensor-to-controller and controller-to-actuator time delays. The delays are bigger than one sample and random. By using of buffers, the original problem can be transformed into linear system with constant delay. The optimal size of the buffer is an open problem. Increase of the buffer length deteriorates the quality because of longer delay in the control loop. At the same time longer buffer decreases the probability of packet dropping and thus improves the quality. The idea is to make the system more robust by buffering and simultaneously adjusting the control loop sampling and actuation intervals. The paper presents this “co-design” approach and demonstrates it for LQ control problem of cart-pendulum model.

State and parameter estimation in a hydraulic system - moving horizon approach

Abstract: In most control systems the best quality of control can be achieved if an exact model of a plant is known and if disturbances-free and continuous (instead of discrete) measurements of all its state space variables are available. Since it is seldom the case in real-life installations, state observers, adapting (parameters identification) algorithms, anti-noise filters and continuous signal estimators must be often employed. The paper describes an application of the moving horizon estimation (MHE) and continuous state estimation from discrete output measurements (CSE-DOM) based method to a laboratory hydraulic three-tank system. The resulting algorithm encompasses all the four above-mentioned mechanisms (state observation, parameters identification, disturbances filtration and continuous state estimation) and can be used for nonlinear systems as well, which is the case in the presented article. The paper provides a detailed explanation of how the MHE and CSEDOM methods were adapted to be applicable to the three-tank system. Results of computer simulations and practical laboratory experiments are also included.

Implementing Fractional PID Control for MagLev with SoftFRAC

Abstract: Nowadays, a realization of non-integer (fractional) order elements on a digital platform is a Widely researched problem. The theory of such dynamic components is relatively well grounded, however, many problems of implementation on a digital platform are still open. In this paper we consider real time fractional control of MagLev system. Classical methods of approximation and available toolboxes are unable to function in the fast discrete time environment. As a solution in this paper we use a novel library: SoftFRAC Which is dedicated for such control tasks. We illustrate library operation, controller design and present the application.

Analytical solutions of electrical circuits described by fractional conformable derivatives in Liouville-Caputo sense

Abstract: In this paper, new analytical solutions for the RL, LC and RLC electric circuits considering conformable and β -derivatives of type Liouville-Caputo were analyzed. These solutions were obtained by iterating conformable and β -integrals. The fractional derivatives considered have properties similar to the classical fractional integrals and derivatives. Due to these operators depend on two parameters, we obtain a better detection of the memory. Novel fractional conformable β -derivatives in the Riemann-Liouville and the Liouville-Caputo sense are obtained. Numerical simulations of alternative models are presented for evaluating the effectiveness of these representations. Different source terms are introduced in the fractional conformable differential equations in Liouville-Caputo sense.

Power law filters: A new class of fractional-order filters without a fractional-order Laplacian operator

Abstract: A new category of fractional-order filters, realized without employing a fractional-order Laplacian operator is introduced in this work. This can be achieved through the utilization of an efficient curve fitting method which approximates the frequency-domain behavior of the filter and transposes the fractional-order transfer function into the integer-order domain. Thus, the procedure results in a rational integer-order transfer function and its implementation is possible using conventional integer-order realization techniques. Therefore, there is no need for fractional-order elements to realize this class of filters. Design examples of this new kind of filters are presented with the derived simulation and experimental results confirming their correct performance.