Showing papers by "Cristina I. Muresan published in 2015"

Fractional order control of unstable processes: the magnetic levitation study case

Abstract: Although a considerable amount of research has been carried out in the field of fractional order controllers, the majority of the results deal with stable processes. Very little research has been reported regarding the design, analysis, and tuning of fractional order controllers for unstable processes. This paper proposes a methodology for designing and tuning fractional order controllers for a class of unstable second-order processes. The design is carried out using the stability analysis of fractional order systems, by means of Riemann surfaces and a proper mapping in the $$w{\text {-}}\hbox {plane}$$ . The resulting fractional order controllers are implemented using graphical programming on industrial equipment and are validated experimentally using a laboratory scale magnetic levitation unit.

Sliding mode control for a class of sub-systems with fractional order varying trajectory dynamics

Abstract: In this paper, a sliding mode control strategy is discussed for a class of nonlinear mechanical sub-systems with varying trajectory dynamics. The proposed class of sub-systems are represented in this simulation example by a two link robot actuator/manipulator. The fractional order is introduced in the setpoint definition as to represent changes in the desired trajectory of this sub-system. Furthermore, the same order is used to adapt the control law to the new dynamics. Uncertainties are introduced in the model used for the control law, hence robustness is intrinsic.

Fractional order PI control strategy on an activated sludge wastewater treatment process

Abstract: Lately, the eco-friendly concept have impacted all the human activities. The wastewater treatment plant (WWTP) are now subject to optimization processes required for reaching the strict regulations applied on the discharged waters. Efficiency and costs are also key terms in this context, thus manually operation of these plants is not accepted anymore. The activated sludge process is the most complex and energy consuming part of a WWTP. Two robust Pi controllers - a conventional PI and a fractional order PI - on the dissolved oxygen concentration are presented in this paper having the goal of decreasing the operation costs, increasing the performance and rejecting the disturbances. The controllers were designed and simulated using a mathematical model tuned based on the data from the WWTP of Romanofir, Talmaciu.

Fractional order IMC based controller for time delay systems

Abstract: In this paper a novel control strategy implying a Smith Predictor structure is proposed for which the primary controller is tuned based on the IMC method, but altered such that the final primary controller is a fractional order controller. A first order time delay process is used as a case study. The simulation results show that the proposed fractional order IMC controller ensures improved closed loop performance compared to the classical IMC, especially in terms of modeling uncertainties.

Auto-tuning fractional order velocity control of a DC motor

Abstract: Most of the tuning techniques for fractional order controllers deal with complex computations and optimization routines, not suitable for auto-tuning control schemes. This research paper proposes a novel, vector based fractional order parameter tuning algorithm which considerably simplifies the procedure. The control aspect of the auto-tuning fractional order control scheme is studied in velocity control of DC motor.

Implementation of an extended prediction self-adaptive controller using LabVIEW TM

Abstract: The implementation of the Extended Prediction Self-Adaptive Controller is presented in this paper. It employs LabVIEWTM graphical programming of industrial equipment and it is suitable for controlling fast processes. Three different systems are used for implementing the control algorithm. The research regarding the controller design using graphical programming demonstrates that a single advanced control application can run on Windows, real time operating systems and FPGA targets without requiring significant program modifications. The most appropriate device may be selected according to the required processing time of the control signal and of the application. A relevant case study is used to exemplify the procedure.