Romualdo Moreno

Development of a real-time expert system for wastewater treatment plants control

Abstract A real-time expert system to control wastewater treatment plants is presented. The software has been developed in the G2 environment. It contains: an interface that permits on-line acquisition of plant data using G2 standard interface (GSI), a predictive control algorithm for dissolved oxygen (DO) control, and a graphical interface between the expert system and the operator. The dissolved oxygen control is performed using a non-linear predictive control algorithm, that has been developed to satisfy quality constraints whilst reducing energy demands. The algorithm uses data obtained from the plant by hardware sensors, and software which recursively estimates the oxygen uptake rate. All these elements are integrated in a knowledge base that includes a set of diagnosis, detection, prediction and operation rules, making the system capable of handling a wide number of usual (where predictive control can be useful) and unusual situations (where quantitative and qualitative information must be considered.

A refinement procedure for PID controller tuning

The use of optimization is an alternative to the well-known automatic PID tuning rules. However, for a proper approach to the optimization problem, the stability of the resulting closed-loop must be guaranteed. A framework for the PID parameter optimization, with stability guarantees, is proposed in this paper. The framework is intended to be used to refine an initial choice for the PID parameters. The way to the solution is based on to the characterization of the set of PID achievable designs and the establishment of a condition that will ensure us to move on to the appropriate subset of achievable stable PID designs. The optimization procedure is applied to tune a PI controller on an unstable system and also on a non-minimum phase system.

Causal simulation models for facing third millennium air transport sustainability

Aeronautics and air transport is a vital sector of our society and economy. Air transport logistics is one of the key players to support efficient globalization; however, sustainable mobility is at stake, due to facts such as the interdependencies with the financial system, climate change and an increasing scarcity of resources. This paper highlights the consequences of a lack of a proper understanding of air-side and land-side, leading to an unsustainable air transport system. A system approach for knowledge sharing between air traffic controllers, handling operators, airlines and airport managers is justified by means of causal models to design a mitigation mechanism to tackle perturbations instead of increasing the latent capacity. The simulation benefits to design indicators of sustainability are also mentioned.

Considerations on PID controller operation: Application to a continuous stirred tank reactor

This paper analyzes optimal controller settings for controllers with One-Degree-of-Freedom (1-DOF) Proportional-Integral-Derivative (PID) structure. The analysis is conducted from the point of view of the operating mode (either servo or regulation mode) of the control loop and tuning mode of the controller. Performance of the optimal tuning settings (ISE-like) can be degraded when the operating mode is different from the select one for tuning. An index for measuring the overall Performance Degradation is proposed and from the minimum of this, tradeoff tuning settings are given. The proposed procedure is applied to control a Continuous Stirred Tank Reactor (CSTR), which is a non-linear system.

A Hybrid Algorithm for the Multi Level Capacitated Lot Sizing Problem with Setup Carry-over

We present a hybrid algorithm for the multi level capacitated lot sizing problem with setup carry-over. The problem is an extension of the classical capacitated lot sizing problem. The inclusion of setup carry-over implies that the setup state of a machine can be extended over two, or more, consecutive periods. The proposed algorithm is based upon a hybrid approach, where a metaheuristic, an LP solver and a dynamic programming scheme are iteratively used within a Lagrangean framework. Finally, three repair heuristics aimed at finding feasible solutions in the neighborhood of an incumbent, infeasible solution, are presented. The algorithm is tested on 480 benchmark instances from the literature and promising results are obtained, both in terms of solution quality and computational time.

An undergraduate laboratory course on fuzzy controller implementation in FPGAs

In this paper the guidelines for a lab course consisting of implementing a fuzzy controller in an FPGA are given. The aim is to introduce it at the Autonomous University of Barcelona as an undergraduate lab course on embedded control using FPGAs.

Coprime factorization based strong stabilizing controller design

In this paper a general two-step design procedure for robustness enhancement aimed at finding stable stabilizing (strong stabilizing) controllers for LTI systems is presented. The proposed approach attemps to deal with strong stabilization issues and recent linear robust control design techniques in a unified way.

2-DOF Control Configuration Applied to 1992 ACC Benchmark Problem

The 2-DOF Observer-Controller configuration is based on a right coprime factorization of the plant and makes use of an observer-based feedback control scheme combined with a prefilter controller. A two-step design procedure is accomplished: first, we can design to guarantee stability robustness and some levels of performance in terms of disturbance rejection; second, we can design the prefilter controller to guarantee open-loop processing of the reference commands. The first step is carried out by solving a constrained Hinfin optimization problem using the right coprime factorization of the plant in an active way. The second step is done by assuming a Reference Model and by solving a Model Matching Problem. The design procedure is exemplified by means of the 1992 ACC Benchmark Problem.

The Control Problem: A Framework for A Holistic Design

Traditionally the control problem has been tackled from a reductionist point of view. The complex whole problem has been divided in smaller more manageable subproblems (e.g. model identification, control structure selection, control design, etc). However this presents several problems: i) issues arising from the interrelation between subproblems of the reductionist approach are neglected, ii) recent advances in identification for control have arisen the necessity of tackling the identification and control design in an unified approach, iii) in order to design automatic supervisors high level issues must be considered. Consequently we face the holistic control design problem. First the elements of the problem are defined and their relations established. Secondly we proposed a new scheme for dynamic management of information flow of the control design problem. It provides a structured approach to consider all the important aspects of the control design. It is suited for automatic supervisory schemes design

Application of H ∞ control to an activated sludge process

This paper presents an application of the Robust Control Theory, concretely the H∞ approach, to the control of the activated sludge process with the aim of proving the feasibility of these types of techniques to the control of biotechnological processes. A generic non-linear model of the process is considered. The design of the H∞ controller is carried out based on a linearization of such a model around prescribed operating conditions. In order to evaluate the performance of the design, simulation calculations with input profiles taken from experimental data have been made. The results show the effectiveness of the H∞ design.