Papers by Silvana Revollar
Processes
In this work, deep reinforcement learning methodology takes advantage of transfer learning method... more In this work, deep reinforcement learning methodology takes advantage of transfer learning methodology to achieve a reasonable trade-off between environmental impact and operating costs in the activated sludge process of Wastewater treatment plants (WWTPs). WWTPs include complex nonlinear biological processes, high uncertainty, and climatic disturbances, among others. The dynamics of complex real processes are difficult to accurately approximate by mathematical models due to the complexity of the process itself. Consequently, model-based control can fail in practical application due to the mismatch between the mathematical model and the real process. Control based on the model-free reinforcement deep learning (RL) methodology emerges as an advantageous method to arrive at suboptimal solutions without the need for mathematical models of the real process. However, convergence of the RL method to a reasonable control for complex processes is data-intensive and time-consuming. For this ...
Wastewater treatment plants operation optimization using economic dynamic real time optimization strategies
This paper addresses the implementation of economic oriented model predictive controllers for the... more This paper addresses the implementation of economic oriented model predictive controllers for the dynamic real time optimization of the operation of wastewater treatment plants (WWTP). The controller cost function includes the energy consumption and the fines for effluent ammonia violations as economic performance indices. The economic optimizing controller and the economic oriented tracking controller formulation are considered to be used directly for control in the BSM1 platform. The different designs and structures is compared in terms of satisfactory plant behaviour and operating costs. A non-linear reduced model of the process is used for predictions to get a reasonable computing effort. Their use as a unique model for optimization and control in the single-layer structures prove to be an advantage respect to the two-layer implementation.
Processes, 2020
In this work a comprehensive analysis of the environmental impact of the operation of a wastewate... more In this work a comprehensive analysis of the environmental impact of the operation of a wastewater treatment plant (WWTP) using different control strategies is carried out considering the dynamic evolution of some environmental indicators and average operation costs. The selected strategies are PI (proportional integral) control schemes such as dissolved oxygen control in the aerobic zone (DO control), DO control and nitrates control in the anoxic zone (DO + NO control) and regulation of ammonium control at the end of aerobic zone (Cascade SNHSP) commonly used in WWTPs to maintain the conditions that ensure the desired effluent quality in a variable influent scenario. The main novelty of the work is the integration of potential insights into environmental impact from the analysis of dynamic evolution of environmental indicators at different time scales. The consideration of annual, bimonthly and weekly temporal windows to evaluate performance indicators makes it possible to capture ...
Estudio sobre la identificación de sistemas de segundo orden: una mejora a lazo abierto ya lazo cerrado
In this work an original method for identifying the parameters of a second order under damped sys... more In this work an original method for identifying the parameters of a second order under damped systems is presented. Unlike the classical methods, this new approach takes into account the areas above and below the value of the steady state of the system’s time profile graph when performing the calculations. This procedure is suitable for on line identification. Also, a procedure for closed loop identification method when a PID controller is used in the loop is presented. The techniques are illustrated with numerical examples.
Metodología para la Obtención de Modelos Semifísicos de Base Fenomenológica Aplicada a una Sulfitadora de Jugo de Caña de Azúcar
Revista Iberoamericana de Automática e Informática Industrial RIAI, 2009
Sustainability, 2020
In this paper, a control approach for improving the overall efficiency of a wastewater treatment ... more In this paper, a control approach for improving the overall efficiency of a wastewater treatment plant (WWTP) is presented. It consists of a cascaded control system that uses a global performance indicator as the controlled variable to drive the plant to operating conditions that satisfies trade-offs involved in the WWTP operation, improving the global performance of the plant. The selected global performance indicator is the N/E index that measures the ratio between the amount of nitrogenated compounds eliminated (kgN) and the energy (kWh) required to achieve that goal. This index links the variables of the activated sludge process with the energy consumed in the whole plant, thus the control strategy takes actions based on plantwide considerations. An external Proportional Integral (PI) controller changes the DO set point according to the N/E index and the basic dissolved oxygen (DO) control scheme in the activated sludge process follows this reference changes varying the aeration...
Activated Sludge Process control strategy based on the dynamic analysis of environmental costs
2020 24th International Conference on System Theory, Control and Computing (ICSTCC), 2020
In this work, an analysis of the dynamic behavior of some environmental indicators and the annual... more In this work, an analysis of the dynamic behavior of some environmental indicators and the annual average operation costs under ammonium control of activated sludge process is carried out. A comprehensive analysis of the evolution of environmental indicators considering different temporal windows (weeks and bimesters) allows to detect the seasonal effect of influent disturbances, as well as the most convenient control actions on each scenario. It makes possible to formulate an ammonium control strategy (Cascade SNHSP), where a sequence of movements of ammonium reference (SNHSP) and carbon dosage (Qcarb) are defined to minimize energy ans chemicals usage with a minimum impact on effluent quality. Thus, the proposed strategy improves overall wastewater treatment plant (WWTP) performance.
Optimization of economic and environmental objectives in a Non Linear Model Predictive Control applied to a wastewater treatment plant
2016 20th International Conference on System Theory, Control and Computing (ICSTCC), 2016
Economic model predictive control (EMPC) combines real-time economic optimization and feedback co... more Economic model predictive control (EMPC) combines real-time economic optimization and feedback control in the same algorithm, resulting in a single-layer structure that is especially suitable for non-linear processes operating under strong disturbances. This strategy is used to enhance the performance of WWTPs in terms of economics and effluent quality. The compromise between the optimization of economic and effluent quality objectives in the EMPC is addressed. An heuristic strategy is introduced in the formulation of the EMPC to improve its performance dealing with the multiobjective optimization.
Influence of fuzzy layer in distributed control structure applied to four coupled tanks
2019 IEEE 4th Colombian Conference on Automatic Control (CCAC), 2019
A distributed predictive control strategy including a fuzzy layer is presented in this work. The ... more A distributed predictive control strategy including a fuzzy layer is presented in this work. The control strategy is based on a multi-agent distributed model and it is applied to the four coupled tanks benchmark. The fuzzy inference is used in order to determine the final control action, i.e. the negotiation between the agents. In this work, the influence of the fuzzy inference over the distributed control strategy is analyzed, taking into account the sets size and user requirements.
Water, 2021
This work explores the possibilities of improving the eco-efficiency of Wastewater Treatment Plan... more This work explores the possibilities of improving the eco-efficiency of Wastewater Treatment Plants (WWTPs) introducing a plant-wide perspective in the formulation of the control strategy. Eco-efficiency goals are contemplated in the analysis of the appropriateness of control actions, considering the seasonal effects of temperature into the decision-making process. Plant-wide control strategy handles are the operation variables of the activated sludge process, the volume of the primary clarifier, and the temperature of the anaerobic digester. Performance is evaluated in terms of energy use, biogas production, effluent quality, emissions to air and soil, considering annual and bimestrial average values of indicators to capture seasonal effect of temperature. The result is a set of possible solutions, obtained from a multi-objective decision-making procedure, consisting on a sequence of control actions applied at different temporal windows that improve the eco-efficiency indicators of...
Applied Sciences, 2018
The main scope of this paper is the proposal of a new single layer Nonlinear Economic Closed-Loop... more The main scope of this paper is the proposal of a new single layer Nonlinear Economic Closed-Loop Generalized Predictive Control (NECLGPC) as an efficient advanced control technique for improving economics in the operation of nonlinear plants. Instead of the classic dual-mode MPC (model predictive controller) schemes, where the terminal control law defined in the terminal region is obtained offline solving a linear quadratic regulator problem, here the terminal control law in the NECLGPC is determined online by an unconstrained Nonlinear Generalized Predictive Control (NGPC). In order to make the optimization problem more tractable two considerations have been made in the present work. Firstly, the prediction model consisting of a nonlinear phenomenological model of the plant is expressed with linear structure and state dependent matrices. Secondly, instead of including the nonlinear economic cost in the objective function, an approximation of the reduced gradient of the economic function is used. These assumptions allow us to design an economic unconstrained nonlinear GPC analytically and to state the NECLGPC allow for the design of an economic problem as a QP (Quadratic Programing) problem each sampling time. Four controllers based on GPC that differ in designs and structures are compared with the proposed control technique in terms of process performance and energy costs. Particularly, the methodology is implemented in the N-Removal process of a Wastewater Treatment Plant (WWTP) and the results prove the efficiency of the method and that it can be used profitably in practical cases.
Processes, 2020
This paper describes a design procedure for a collaborative control structure in Plant Wide Contr... more This paper describes a design procedure for a collaborative control structure in Plant Wide Control (PWC), taking into account the existing controllable parameters as a novelty in the procedure. The collaborative control structure includes two layers, supervisory and regulatory, which are determined according to the dynamics hierarchy obtained by means of the Hankel matrix. The supervisory layer is determined by the main dynamics of the process and the regulatory layer comprises the secondary dynamics and controllable parameters. The methodology proposed is applied to a wastewater treatment plant, particularly to the Benchmark Simulation Model No 1 (BSM1) for the activated sludge process, comparing the results with the use of a Model Predictive Controller in the supervisory layer. For determining controllable parameters in the BSM1 control, a new specific oxygen mass transfer model in the biological reactor has been developed, separating the kLa volumetric mass transfer coefficient ...
IFAC-PapersOnLine, 2018
In this paper, a PID based hierarchical control structure is proposed to improve the overall WWTP... more In this paper, a PID based hierarchical control structure is proposed to improve the overall WWTP performance. The control problem is focused on the definition of integral efficiency indices for a typical WWTP operation. The efficiency index considered in this work is the ratio between the nitrogen removed in the activated sludge process (Kgr N) and the energy (kWh) required for eliminating that amount of nitrogenated compounds (N/E index). The efficiency index is used as the controlled variable for an upper level PI controller that manipulates the dissolved oxygen (DO) set point to keep the index as close as possible to a desired level. Effect of DO manipulation is analyzed and DO operation is defined in terms of its overall effect instead of local DO dynamics.
IFAC-PapersOnLine, 2016
Nonlinear model predictive controllers based on neural networks are implemented in this paper to ... more Nonlinear model predictive controllers based on neural networks are implemented in this paper to regulate the activated-sludge process. The simulation protocol BSM1 is used to apply the predictive controller schemes and study the closed loop process behavior in different situations. Also input-output data are gathered from the benchmark for the neural networks training. Control results under dry-weather perturbations are satisfactory when a combined NLMPC-Classic PI control system is tested. This scheme has shown the best performance when compared to a centralized NLMPC scheme, a decoupled NLMPC scheme or the classic PI system developed on the BSM1. An economic analysis indicates that the neural predictive algorithm for nitrates control improves the effluent quality while also decreasing the pumping energy consumption by optimizing the internal recirculation flowrate variations.
This work presents the simultaneous synthesis, design and control of an activated sludge process.... more This work presents the simultaneous synthesis, design and control of an activated sludge process. The mathematical formulation translates a process superstructure into a mixed-integer non-linear optimization problem. The optimization has been solved by the classical method of Branch and Bound using the SQP method for the evaluation of the nodes. The PID's are tuned using the SIMC (Simple Internal Model Control) method in order to avoid decomposition algorithms. The results of the integrated approach are compared to the obtained when classical methodology is applied, giving better controllable plants.
Aplicación de Algoritmos Genéticos en la Solución del Diseño Integrado de Sistemas de Reactores Químicos
Se presenta la formulación matemática del problema de diseño integrado de reactores tipo tanque c... more Se presenta la formulación matemática del problema de diseño integrado de reactores tipo tanque continuo agitado, traduciendo una superestructura de dos reactores en serie, donde se incluyen todas las alternativas de diseño, en un modelo de optimización mixto-entero (MINLP). Se presenta la resolución de este problema de optimización mixto-entero utilizando algoritmos genéticos. La flexibilidad de los algoritmos genéticos permite alcanzar el objetivo final de este diseño optimo, minimizando los costos de construcción para el sistema a la vez que se imponen condiciones de estabilidad y ciertas condiciones de controlabilidad.
A closed loop paradigm for NLGPC with constraints on control variables
This paper deals with on-line estimation and control of a biological wastewater treatment plant p... more This paper deals with on-line estimation and control of a biological wastewater treatment plant process. The objective of the control is to force the residual substrate and the dissolved oxygen to track a given set point despite the disturbances and system parameter uncertainties. The control law is based on a NLGPC embedded with a nonlinear closed loop paradigm. The control approach structure is combined with the Kalman Filter, for the on-line reconstruction of unmeasured biological states and unknown parameters of the bioprocess. The efficiency of both the control and estimation are demonstrated via computer simulations.
Set-point optimization for enhancing the MPC control of the N-removal process in WWTP's
In this paper, an steady state set point optimization is applied to improve the Model Predictive ... more In this paper, an steady state set point optimization is applied to improve the Model Predictive Control (MPC) performance in the nitrogen removal reactors of a Wastewater Treatment Process (WWTP). The objective is to find out the set points that optimizes the Effluent Quality (EQ) and the energy costs for a dry season characteristic influent. An MPC algorithm that guarantees offset-free control and satisfactory disturbance rejection is implemented. The set point optimization improved the nitrogen removal (N-removal) process in terms of EQ and energy costs, resulting in a 75% decrease of pumping energy.
Algorithmic synthesis and integrated design of chemical reactor systems using genetic algorithms
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Papers by Silvana Revollar