On Lyapunov sampling for event-driven controllers

This paper investigates an event condition for event-driven controllers based on Lyapunov functions. Considering that constant values of a Lyapunov function define contour curves that form closed regions around the equilibrium point, in this paper we present a sampling mechanism that enforces job executions (sampling, control algorithm computation and actuation) each time the system trajectory reaches a given contour curve. By construction, the sequence of generated samples is stable in the discrete Lyapunov sense. However, in order to ensure that the system trajectory will tend to zero as time tends to infinity, it must be ensured that the sequence of samples is infinite. We provide conditions to ensure this property. The approach is illustrated by simulated examples.Peer ReviewedPostprint (published version

Análisis coste-beneficio de las estructuras inteligentes

Definimos estructura inteligente como aquella estructura dotada de unos sensores (en especial continuos y de fibra óptica), de manera que es capaz de transmitir datos de interés sobre su estado de salud (deformaciones, fisuraciones, oxidaciones, etc.). Esta tecnología puede facilitar el mantenimiento preventivo de los edificios y la gestión de su salud estructural. Por ello, un aspecto de interés necesario a analizar para saber si la tecnología es aplicable o no, es evaluar su rentabilidad. Así, el objeto de este artículo es realizar un análisis coste-beneficio de las estructuras inteligentes, estudiando por un lado cuál es el incremento de coste inicial que supone la implementación de la propuesta, y por otro lado evaluar cuál es el ahorro de dinero a lo largo del tiempo que supone la aplicación de la misma, lo que permite establecer el periodo de retorno de la inversión inicial, y a partir de qué momento sepueden esperar beneficios netos.Peer ReviewedPostprint (published version

Análisis coste-beneficio de las estructuras inteligentes

Definimos estructura inteligente como aquella estructura dotada de unos sensores (en especial continuos y de fibra óptica), de manera que es capaz de transmitir datos de interés sobre su estado de salud (deformaciones, fisuraciones, oxidaciones, etc.). Esta tecnología puede facilitar el mantenimiento preventivo de los edificios y la gestión de su salud estructural. Por ello, un aspecto de interés necesario a analizar para saber si la tecnología es aplicable o no, es evaluar su rentabilidad. Así, el objeto de este artículo es realizar un análisis coste-beneficio de las estructuras inteligentes, estudiando por un lado cuál es el incremento de coste inicial que supone la implementación de la propuesta, y por otro lado evaluar cuál es el ahorro de dinero a lo largo del tiempo que supone la aplicación de la misma, lo que permite establecer el periodo de retorno de la inversión inicial, y a partir de qué momento se pueden esperar beneficios netos.Peer ReviewedPostprint (published version

Cost-benefit analysis of smart structures

Smart structure is defined as structure equipped with sensors (especially continuous and composed of fiber optic), so that it is able of transmitting data of interest about its state of health (deformations, cracks, oxidation, etc.). This technology can facilitate the preventive maintenance of buildings and the management of their structural health. Therefore, a necessary aspect of interest to analyze in order to know if the technology is applicable or not, is to evaluate its profitability. Thus, the objective of this paper is to perform a cost-benefit analysis of smart structures, studying on the one hand which is the initial cost increase involved in the implementation of the proposal, and on the other hand to evaluate which is the saving of money to over the time that this application represents, what allows to establish the point of return on investment (ROI), and from which moment it is possible to expect net benefitsPeer ReviewedPostprint (published version

Anàlisi cost-benefici de les estructures intel.ligents

Postprint (author's final draft

Analysis of the effect of clock drifts on frequency regulation and power sharing in inverter-based islanded microgrids

© 2018 IEEE. Personal use of this material is permitted. Permission from IEEE must be obtained for all other uses, in any current or future media, including reprinting/republishing this material for advertising or promotional purposes,creating new collective works, for resale or redistribution to servers or lists, or reuse of any copyrighted component of this work in other works.Local hardware clocks in physically distributed computation devices hardly ever agree because clocks drift apart and the drift can be different for each device. This paper analyses the effect that local clock drifts have in the parallel operation of voltage source inverters (VSIs) in islanded microgrids (MG). The state-of-the-art control policies for frequency regulation and active power sharing in VSIs-based MGs are reviewed and selected prototype policies are then re-formulated in terms of clock drifts. Next, steady-state properties for these policies are analyzed. For each of the policies, analytical expressions are developed to provide an exact quantification of the impact that drifts have on frequency and active power equilibrium points. In addition, a closed-loop model that accommodates all the policies is derived, and the stability of the equilibrium points is characterized in terms of the clock drifts. Finally, the implementation of the analyzed policies in a laboratory MG provides experimental results that confirm the theoretical analysis.Peer ReviewedPostprint (author's final draft

Anàlisi const-benefici de les estructures intel·ligents

Quan es pensa en un element constructiu de formigó armat, s'associa clarament a un ésser inanimat, de la mateixa manera que una pedra també s'associa a un ésser inanimat. Però, i si fos possible dotar aquest element de formigó armat, aquest ésser inanimat, d'un sistema nerviós que li permetés transmetre dades sobre el seu estat de salut (fissuracions, deformacions, humitats, carbonatació, oxidació, etc.)? I si això pogués realitzar-se amb tota l'estructura d'un edifici? Això aportarà clarament beneficis importants, atès que facilita significativament el manteniment dels edifici si permet detectar precoçment les patologies existents. Explicat així, sona en certa manera a ciència ficció, però no ho és en absolut

Embedding Kalman techniques in the one-shot task model when non-uniform samples are corrupted by noise

The performance of several closed-loop systems whose controllers concurrently execute in a multitasking realtime system may be deteriorated due to timing uncertainties in tasks´executions, problem known as scheduling jitters. Recently, the one-shot task model, that combines irregular sampling, a predictor observer, and strictly periodic actuation, was presented in order to remove the negative effects of jitters. However, its successful application required noise-free samples. In this paper we extend the one-shot task model to the case of noisy measurements. In particular, we embed a Kalman filter into the model taking into account that the available measurements are not periodic. This poses the problem of adapting the standard discrete-time Kalman filter to the case under study, and decide when to apply the prediction and the correction phase. Two different strategies are presented, and their control performance and computation demand are analyzed through real experiments.Peer ReviewedPostprint (published version

Efficient utilization of bus idle times in CAN-based networked control systems

This paper presents a novel approach to networked control systems (NCS) analysis and design that provides increased control performance for a set of control loops that exchange control data over the Controller Area Network (CAN). This is achieved by enabling the following functionality for each control loop: first, standard periodic messaging is guaranteed to ensure stability, and second, non-periodic additional messaging is added whenever the bus is idle in such a way that the aggregated control performance for all control loops is improved. The proposed approach, named Maximum Difference (MD) policy, is computable in a distributed manner, and is practically feasible (computationally efficient and CAN-implementable). We theoretically prove that the MD policy behaves better than static strategies. Simulation results complement the theoretical derivations and show that the MD policy outperforms static, random and Largest Error First policies.Postprint (author’s final draft

Local secondary control for inverter-based islanded microgrids with accurate active-power sharing under high load conditions

Local secondary control has been successfully used to regulate the frequency of inverterbased islanded microgrids without using communications. In this scenario, noticeable steady-state deviations have been observed in active power sharing caused by the inherent clock drift of the digital processors that implement each inverter local control. This paper presents a control scheme that performs frequency regulation and improves the active power sharing under high load conditions, thus alleviating the impact of clock drifts in this situation. The study introduces a theoretical analysis that quantifies the steady-state deviations in active power sharing. It also includes a design procedure for the control parameters based on static and dynamic specifications. Experimental tests validate the expected features of the proposed control. The experimental setup is based on a laboratory microgrid equipped with three independent digital signal processors with different clock drifts.Postprint (author's final draft