George Acioli Júnior

On Simple Identification Techniques for First-Order Plus Time-Delay Systems

Abstract First-Order plus Time-Delay (FOPTD) models are extensively used to approximate systems in order to tune PID controllers. Several estimation techniques have been developed and the obtained models applied to controller design. Most estimation techniques are based on least-squares and excitation such as step, square waves and pseudo-random signals. In order to speed up the experiments, simple and short excitations have also been considered. Pulses (rectangular, double rectangular, doublet) as well as relay experiments have been used. Estimation is performed in time or frequency domains. In this paper alternatives are proposed to robustify the estimates in order to obtain a better model around important frequencies. Simulation results are presented to illustrate the techniques.

A Flexible Laboratory-Scale Quadruple-Tank Coupled System for Control Education and Research Purposes

Abstract In this paper it is described a flexible laboratory-scale quadruple-tank coupled system designed for Control Education and Research purposes. The quadruple-tank process presented is a flexible structure for experimental implementation and evaluation of different control strategies in a multivariable non-linear process. The structure allows the implementation of different experiments, such as SISO (single-input single-output), TITO (two-input two-output) and MIMO (multiple-input multiple-output), with the option of coupling or cascade effect between tanks. A general description for the system is presented. A linear dynamic model of the tank system is presented for a SISO configuration and simple experiments are shown which illustrate the use of the laboratory-scale system in undergraduate control course.

Closed-loop evaluation and PI controller redesign satisfying classical robustness measures

In this paper it is proposed a procedure for closed-loop evaluation and PI controller redesign using a relay-based experiment. The experiment data is used to evaluate the actual closed-loop. It is evaluated using classical robustness measures. A first-order plus dead-time(FOPDT) process model is estimated using the relay data. The controller redesign is performed using the robustness measures and a FOPDT model. The aim of controller redesign is to achieve a closed-loop with classical robustness measures around the redesign specifications. Simulation examples illustrate the redesign procedure.

Two-input Two-output Laboratory-scale Temperature System Based on Peltier Modules

Abstract A laboratory-scale temperature system for Control and Automation courses is presented. The system is a coupled two-input two-output process which use peltier modules for temperature control. This paper describes the laboratory-scale system in details. A linear dynamic model of the thermoelectric cooler including the heat sink and the cooling-load heat exchanger is developed and experiments are shown which illustrate the use of the system.

LOOP-SHAPING PI CONTROLLER REDESIGN USING LEAST-SQUARES MODEL-MATCHING

Abstract In this work it is presented a PI controller loop-shaping redesign technique. The existing closed-loop is excited using a relay experiment which allows one to estimate the current phase-margin, the crossover frequency and a first-order plus time-delay model. Techniques for continuous-time identification are examined. Based on the information obtained from the experiment, a desired loop transfer function is defined. The controller is obtained using least squares model-matching. Constrained optimization is used in the estimation. Simulation examples illustrate the technique.

System identification of a pilot scale heat exchanger: A state-space realization approach

It is presented a state-space realization approach for identification of a pilot scale heat exchanger plant. The proposed methodology is a computational efficient way to estimate state-space models from experimental data with pulsed input signals. It is specially suitable for short data batches.

Closed-loop evaluation and redesign of decentralized PI controllers satisfying classical robustness measures

In this paper it is proposed a procedure for MIMO closed-loop evaluation and decentralized PI controller redesign using a relay-based experiment in a sequential manner. The experiment data is used to evaluate the actual MIMO closed-loop. It is evaluated using classical robustness measures of each loop. The aim of the controller redesign is to achieve a closed-loop with classical robustness measures around the redesign specifications. Simulation examples illustrate the redesign procedure.