Showing papers by "Isabela Roxana Birs published in 2019"

A Survey of Recent Advances in Fractional Order Control for Time Delay Systems

Abstract: Several papers reviewing fractional order calculus in control applications have been published recently. These papers focus on general tuning procedures, especially for the fractional order proportional integral derivative controller. However, not all these tuning procedures are applicable to all kinds of processes, such as the delicate time delay systems. This motivates the need for synthesizing fractional order control applications, problems, and advances completely dedicated to time delay processes. The purpose of this paper is to provide a state of the art that can be easily used as a basis to familiarize oneself with fractional order tuning strategies targeted for time delayed processes. Solely, the most recent advances, dating from the last decade, are included in this review.

Tuning of fractional order proportional integral/proportional derivative controllers based on existence conditions:

Abstract: Fractional order proportional integral and proportional derivative controllers are nowadays quite often used in research studies regarding the control of various types of processes, with several pa...

Identification for control of suspended objects in non-Newtonian fluids

Abstract: This paper proposes a framework for modelling velocity profiles and suspended objects in non-Newtonian fluid environment. A setup is proposed to allow mimicking blood properties and arterial to venous dynamic flow changes. Navier-Stokes relations are employed followed by fractional constitutive equations for velocity profiles and flow. The theoretical analysis is performed under assumptions of steady and pulsatile flow conditions, with incompressible properties. The fractional derivative model for velocity and friction drag effect upon a suspended object are determined. Experimental data from such an object is then recorded in real-time and identification of a fractional order model performed. The model is determined from step input changes during pulsatile flow for velocity in the direction of the flow. Further on, this model can be employed for controller design purposes for velocity and position in pulsatile non-Newtonian fluid flow.

An Autotuning Method for a Fractional Order PD Controller for Vibration Suppression

Abstract: Fractional order controllers are receiving an ever-increasing interest from the research community due to their advantages. However, most of the tuning procedures for fractional order controllers assume a fully known mathematical model of the process. In this paper, an autotuning method for the design of a fractional order PD controller is presented and applied to the vibration suppression in airplane wings. To validate the designed controller, an experimental unit consisting of a smart beam that simulates the behaviour of an airplane wing is used. The experimental results demonstrate the efficiency of the designed controller in suppressing unwanted vibrations.

Design and Practical Implementation of a Fractional Order Proportional Integral Controller (FOPI) for a Poorly Damped Fractional Order Process with Time Delay

Abstract: One of the most popular tuning procedures for the development of fractional order controllers is by imposing frequency domain constraints such as gain crossover frequency, phase margin and iso-damping properties. The present study extends the frequency domain tuning methodology to a gen-eralized range of fractional order processes based on second order plus time delay (SOPDT) models. A fractional order PI controller is tuned for a real process that exhibits poorly damped dynamics characterized in terms of a fractional order transfer function with time delay. The obtained controller is validated on the experimental platform by analyzing staircase reference tracking, input disturbance rejection and robustness to process uncertainties. The paper focuses around the tuning methodology as well as the fractional order modeling of the process’ dynamics.

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.

Experiment Design and Estimation Methodology of Varying Properties for Non-Newtonian Fluids

Abstract: This paper provides an overview of the distributed parameter properties of non-Newtonian fluids and a proposal for identifying them. A low cost setup is described along with a proposed methodology protocol. The paper introduces the problem of moving from a linear framework of fluid properties towards a nonlinear one and motivates the choice for lumped nonlinear parameter model structures. It follows identification using nonlinear least squares in various liquids. The results obtained suggest that parameters of the proposed fractional order impedance model are susceptible to changes in density as being one important feature of non-Newtonian fluids. Further use of these findings across disciplines is given in the conclusion section of the paper.

Electrical circuits to mimic respiratory diseases: an interdisciplinary bachelor project

Abstract: This paper introduces a multidisciplinary project that is given in the last year of bachelor studies in civil engineering at Ghent University, Belgium. In this project, concepts learned during the first three years of study (bachelor program) are applied on a real system. Electrical circuits are build to mimic changes occurring at specific locations in the respiratory tree. The hypothesis tested using this cross-disciplinary project was that if a link exist to a real functionality provide a better understanding and leads to better outcomes in terms of learning process. In this project the students need to build an analogy between the lung airways properties and use equivalence to electrical circuits to evaluate and mimic changes from disease. During this project the students learned to work in a team and to allocate tasks among the team members. Another important competence that they have gained is time management. They have also developed skills for poster design and presentation, developed a critical thinking. All these have lead to a successful implementation of the project and they were able to critically asses changes to mimic diseases.

Fractional-order modeling of impedance measurements in a blood-resembling experimental setup *

Abstract: In this paper we analyze the opportunity to provide a methodology and signal processing algorithm to model and quantify drug concentrations in blood. The properties of blood as a non-Newtonian fluid are used to develop a physiologically based model using fractional calculus tools, which provide natural solutions to derivatives which no longer limit their order to integer numbers. In vitro tests support our mathematical model development. A prospective use for continuous monitoring of drug concentration profiles during anesthesia or other interventions is proposed. The proposed solution is based on fractional order impedance models.