Adaptive Delta Modulation in Networked Controlled Systems With bounded Disturbances

This technical note investigates the closed-loop properties of the differential coding scheme known as Delta Modulation (Δ - M) when used in feedback loops within the context of linear systems controlled through a communication network. We propose a new adaptive scheme with variable quantization step Δ, by defining an adaptation law exclusively in terms of information available at both the transmitter and receiver. With this approach, global asymptotic stability of the networked control system is achieved for a class of controllable (possibly unstable) linear plants. Moreover, thanks to the globally defined switching policy, this architecture enjoys a disturbance rejection property that allows the system to recover from any finite-time unbounded disturbance or communication loss

Community Resilience Processes in Schools with Roma Students during COVID-19 : Two Case Studies in Spain

The aim of this paper is to describe coping strategies for difficulties generated by the COVID-19 pandemic in schools categorized as "highly vulnerable" in Spain, mainly focusing on children from immigrant and Roma families. Within the framework of a broader research study, we focus our gaze, as a case study, on two schools using in-depth interviews with its principals. These two schools were chosen as case studies because they had shown a history of carrying out documented educational change processes for at least 3 years before the pandemic. Our analytical strategy was a qualitative content analysis of a deductive-inductive nature. The results of our study can help identify key elements for the mechanisms of "Community Socio-Educational Resilience" and show that the innovative educational strategies tested by schools in the periods prior to the pandemic facilitated the generation of specific strategies for addressing problems arising from the pandemic. These strategies contributed to cushioning the increased inequality generated by the pandemic, contributing to the social sustainability of the educational and community system

Virtual assistant for individualized practical training on controller design

Abstract: In this work we present a virtual assistant to help instructors offer individualized practical training on controller design for linear systems. The virtual assistant is designed to be used together with Goodle GMS, a web application which offers services for the collection, storage and automatic grading of students exercises. Using the proposed scheme, an instructor can generate in an easy way and without having knowledge of programming, individualized exercises that can be graded automatically, ensuring that all the exercises have a solution and the same degree of difficulty. The platform has been teste

Voltage Balance for Five-Level DCC Based on Mixed-Integer Linear Programming

In power converters, the modulation stage commands the switching devices to drive the converter outputs to the voltage required by the inner controllers in order to achieve their objectives. However, in multilevel converters, the modulation may be in charge of an ad ditional goal since it also has to tackle with the capacitor voltage balancing issue. This paper formulates the modulation of multilevel three-phase power converters, specifically a five-level diode-clamped converter (DCC), as a mixed-integer linear optimization prob lem. In this paper, it is shown that the presented optimization problem can deal with the capacitor voltage balance at the same time that the number of commutations is minimized. The problem is solved offline and its solution is stored in a lookup table to be used during normal operation. Then, an online procedure to obtain the levels that modulate each phase from the lookup table is given. Comparisons with model predictive control, space-vector based algorithms and other modulation approaches are presented in simulations. Several experimental results are presented showing the feasibility of this approach with changes in the operating conditions

Asymptotic rejection of sinusoidal disturbances based voltage balance control in back-to-back power converters

This paper addresses the imbalance problem of the dc-link capacitor voltages in the three-level diode-clamped back-to-back power converter. In order to cope with it, a mathematical analysis of the capacitor voltage difference dynamics, based on a continuous model of the converter, is first carried out. It leads to an approximated model which contains explicitly several sinusoidal functions of time. In view of this result, the voltage imbalance phenomenon can be addressed as an output regulation problem, considering the sinusoidal functions as exogenous disturbances. Thus, a novel approach to deal with the mentioned problem in the back- to-back converter is presented. Then, the particular features of the disturbances are used to design several controllers. They all follow an asymptotic disturbance rejection approach. In this way, the estimations of the disturbances are used to apply a control law that cancels them while regulating the capacitor voltage balance as well. Finally, the performance of the proposed control laws is evaluated, presenting the simulation results obtained when the different controllers are implemented.MICINN-FEDER DPI2009-0966

Pseudo-optimal five-level DCC modulation based on machine learning

This paper presents a method for the control design of five-level DCC converters based on mixed-integer optimization and machine learning. The resulting controller is computationally simple and can be easily implemented on low-resource control hardware using simple nested “if-else” statements. The optimization problem is recalled from previous work by modifying the cost function to further enhance the dynamic performance. Additionally, and in contrast to previous works, the online implementation accomplished in this paper allows the system to cover a wider range of operating points. For this, the optimization problem is solved offline for several operating conditions, and the results are gathered into a dataset to train classification and regression trees (CARTs), which are later used online. Due to the generalization capability of the CARTs, a more flexible and less resource-intensive implementation is achieved which is capable of operating at points outside the ones considered in the training dataset. The resulting control strategy is compared in simulation and experiments with several alternative approaches found in the literature. This approach can be extended to other power converter topologies, allowing the implementation of optimized modulations

Sistema de Evaluación Automática Vía Web en Asignaturas Prácticas de Ingeniería

En este trabajo se presenta una nueva herramienta web para educación que permite automatizar la recogida y evaluación de ejercicios prácticos de diferentes disciplinas de ingeniería con la complejidad típica que la formación técnica requiere. Una de las principales características de la herramienta propuesta es la posibilidad de personalizar los ejercicios para cada alumno. El sistema realiza una comparación funcional de las soluciones propuestas por los alumnos con las soluciones correctas proporcionadas por el profesorado y en función de los resultados obtenidos asigna una calificación al alumno de forma automática. La plataforma permite al profesor implementar técnicas innovadoras de docencia que fomentan el autoaprendizaje en cursos numerosos. Se presentan los resultados de uso del sistema de evaluación en dos cursos, uno de Teoría de Sistemas y otro de Fundamentos de Informática.Universidad de Sevilla I Plan Propio de Docenci

Hybrid Modelling and Control of a Class of Power Converters With Triangular-Carrier PWM Inputs

In this paper, a new control design procedure for a class of power converters based on hybrid dynamical systems theory is presented. The continuous-time dynamics, as voltage and current signals, and discrete-time dynamics, as the on- off state of the switches, are captured with a hybrid model. This model avoids the use of averaged and approximated models and includes the PWM as well as the sample-and-hold mechanism, commonly used in the industry. Then, another simplified hybrid system, whose trajectories match with the original one, is selected to design the controller and to analyse stability properties. Finally, an estimation of the chattering in steady state of the voltage and current signals is provided. The results are validated through simulation and experiments.MCIN/ AEI Project PID2019-105890RJ-I00MCIN/ AEI Project PID2019-109071RB-I0