Francisco R. Rubio

Universidad de Sevilla | US · Systems Engineering and Automatics

This work addresses the energy management of a combined system consisting of a refrigeration cycle and a thermal energy storage tank based on phase change materials. The storage tank is used as a cold-energy buffer, thus decoupling cooling demand and production, which leads to cost reduction and satisfaction of peak demand that would be infeasible...

El artículo presenta el modelado de un sistema de refrigeración que combina una planta solar de absorción y un sistema de producción de frío basado en enfriadoras refrigeradas por aire. Se pretende satisfacer la demanda de frío de una instalación haciendo que ambas plantas trabajen en paralelo, priorizando el abastecimiento de energía frigorífica p...

In this paper, we aim to open up new perspectives in the field of autonomous aerial surveillance and target tracking systems, by exploring an alternative that, surprisingly, and to the best of the authors’ knowledge, has not been addressed in that context by the research community thus far. It can be summarized by the following two questions. Under...

En este trabajo se detallan algunos aspectos clave en la optimización de la operación de sistemas de refrigeración por compresión de vapor. Se analiza un ciclo básico de una etapa de compresión y un recinto a refrigerar. Se plantea la optimización global según criterios de máxima eficiencia energética, considerando restricciones tanto tecnológicas...

En este trabajo se identifican los parámetros de un modelo de parámetros distribuidos de colectores solares planos mediante un algoritmo genético de codificación real utilizando datos de una planta piloto experimental.

En este artí­culo se evalua el desempeño por apuntamiento de una serie de estrategias de control para seguidores solares de alta concentracion. Dado el alto grado de precisión que se necesita en el apuntamiento real, por debajo del semi ángulo de aceptancia global del sistema de captacion de energí­a, en el artí­culo se revisan las incertidumbres m...

This paper tackles the problem of modelling a smart charging station for electric vehicles (EVCS) that is suitable for DC fast and ultra-fast charging while providing a minimum stress on the power grid. Operation of the charging station is managed in such a way that it is either supplied by photovoltaic (PV) power or the power grid, with the additi...

This paper presents a comparison between five control strategies for HCPV sun tracking that comprise open-loop by means of Solar Equations, closed-loop by Sun position feedback (using an electro-optical sensor and a DC power sensor), and pointing ahead of the Sun. The performance of the control strategies is tested under a fully calibrated sun-trac...

When using high concentration photovoltaics modules, sun trackers must meet severe specifications in order to keep sun pointing error within a very small angle. Those required specifications are not only mechanical (misalignments in the structure itself, clearances of the joints, etc.) but also regards the installation (misalignments of the platfor...

This work is focused on optimal control of mechanical compression refrigeration systems. A reduced-order state-space model based on the moving boundary approach is proposed for the canonical cycle, which eases the controller design. The optimal cycle (that satisfying the cooling demand while maximizing efficiency) is defined by three variables, but...

This paper presents a control strategy for sun trackers which adapts continuously to different sources of error, avoiding the necessity of any kind of calibration by analyzing the produced electric power to sense the position of the Sun. The proposed strategy is able to meet the strict specifications for HCPV sun trackers despite of mechanical unce...

High concentration photovoltaic modules allow a significant increase in the electric power produced per unit area. Nevertheless, in order to reach the maximum possible increase in performance, the sun tracker must meet severe specifications regarding sun-pointing accuracy, because the lens-cell sets of the solar modules only work in a very small an...

This paper presents a distributed set-membership estimation and formation control algorithm for a fleet of vehicles. Each vehicle is equipped with an agent with sensing, acting, computational and communication capacities. The agent's objective is to compute estimation set for the state of all the fleet of vehicles and, additionally, generate contro...

This work describes the optimal control of a parabolic trough solar plant when the solar radiation is subject to variations due to the passage of clouds. The objective of the control strategies developed is to optimize the generated power, unlike other strategies that pursue the maintenance of the outlet oil temperature of the solar field. The sola...

This paper describes and assesses two strategies to control distributed solar collector fields, especially during days with partial radiation due to the passage of clouds. The main objective of these control strategies is to maximize the electrical power generated during different situations in which different parts of the solar field receive diffe...

This paper describes the main problems of operating parabolic trough solar fields during days with partial radiation. An optimal control strategy is proposed to solve these problems and it is assessed against a classical one, which uses a feedforward and a PI controller with a fixed set point of oil outlet temperature. Some simulations have been ma...

This paper shows the relationship between the incident solar radiation and the optimum outlet temperature of a solar field to produce the highest amount of electrical power. Various simulations were made for different values of incident solar radiation, calculating for each one the optimum temperature which produces the maximum electrical power and...

En este artículo se propone un observador distribuido garantista para sistemas en red, considerando de forma explícita el problema de los retardos variables en las comunicaciones. Se asume que la información intercambiada entre agentes llega siempre a su destino, si bien las comunicaciones están sujetas a retardos variables, cuyo valor máximo se su...

Soil water content is the main limiting factor for plant development under arid or semi-arid climates. Furthermore, it is a key factor in the physical, chemical and biological processes that occur in the soil-plant-atmosphere system; acting as a vector between these components. A distributed parameters model is proposed in order to describe the spa...

This paper focuses on the modeling and simulation of parabolic trough solar fields in situations of partial covering of the solar field by clouds. In these situations incident solar radiation on the field is different for each loop of it, so it is necessary to model a field that takes into account this radiation distribution. Then, the effect of pa...

In this paper we propose a novel algorithm for distributed set-membership observation based on zonotopes. The method is able to estimate the dynamics of non-directly measured unstable modes. The distributed observer gains are optimally chosen to minimize the Frobenius norm of the prediction zonotope. The simulations show that the performance of the...

This paper describes the methodology followed to design a functional autopilot for the quadcopter AR.Drone developed by Parrot. The main goal is to design a control strategy for autonomous path tracking in the XY plane, comparing two different control techniques. Three phases are carried out to achieve this objective: model identification, control...

This paper presents the modeling and control of a planar multibody aerial platform, composed of a Miniature Vertical Take-Off and Landing Aerial Platform (MAV-VTOL) and a camera positioning system. The goal is to improve the current operational profile of visual sensors onboard the MAV, by broadening current aerial configurations for visual sensors...

The application of two guaranteed estimation methods on the estimation of a quadrotor position is presented in this paper. A discrete time system model used for the position estimation is supposed, whereas GPS measurement is performed with greater sampling time. Firstly, guaranteed algorithms are applied in order to compute the feasible set of posi...

A nonlinear H∞ controller is designed and applied for two-wheeled self-balanced vehicles, which are underactuated mechanical systems with input coupling. The main objective is, in the presence of exogenous disturbances, to ensure that the inclination angle of the pendulum (controlled DOF) is led to the upper vertical position, while the angular vel...

The chapter proposes an innovative estimation&control scheme that enables the distributed monitoring and control of large-scale processes. The proposed approach considers a discrete linear time-invariant process controlled by a network of agents that may both, collect information about the evolution of the plant and apply control actions to drive i...

This chapter extends the Luenberger-like plus consensus ideas in Chap. 8 to the case of distributed estimation through unrealiable asynchronous communications networks. Again, a set of agents (observers) is assumed to be deployed to estimate the state of a large-scale process taking partial measurements of the process. Each agent builds its estimat...

In this paper the robust control of a one-stage refrigeration cycle is addressed. This is a MIMO process, where the expansion valve opening and the compressor speed are used as manipulated variables, whereas the control of both the outlet temperature of evaporator secondary flux and the superheating degree of refrigerant at evaporator outlet is int...

This paper describes the controllability analysis and the design of a multivariable robust controller for a one-stage refrigeration cycle, which is the most used system for cooling issues and whose energy management and control are key factors. The controlled variables are the superheating degree of refrigerant at the evaporator outlet and the outl...

This paper describes the analysis and robust control of a one-stage refrigeration cycle. Using the compressor speed and the expansion valve opening as control variables, the outlet temperature of evaporator secondary flux and the superheating degree of refrigerant at evaporator outlet are controlled. The main dynamics of the system are identified a...

This paper presents a distributed guaranteed estimation and control technique for a class of nonlinear system. The system outputs are being measured by a set of agents whose objective is the estimation of the whole state. Furthermore, one agent is responsible for the control of the plant. Compared to the case of distributed estimation, the joint pr...

This paper describes the design, implementation and automation of a two-stage, two-load-demand experimental refrigeration plant. The facility is fully configurable, since cycles with one or two compression stages, and one or two load demands can be set up. Detailed description of the experimental facility concerning its physical components, actuato...

In this paper an extension of the algorithms with saturation functions to the nonlinear H∞ control for robot manipulators introduced in [4] has been carried out. Based on the classical algorithm, this extension copes with a nonlinear equation of the closed-loop error. The resulting Lyapunov's equation in the linear case is substituted for a Hamilto...

This paper presents a model predictive control formulation for Networked Control Systems subject to independent and identically distributed delays and packet dropouts. The design takes into account the presence of a communication network in the control loop, resorting to a buffer at the actuator side to store and consistently apply delayed control...

In this paper a nonlinear robust control strategy designed for underactuated mechanical systems is proposed in order to solve the path tracking problem for a quadrotor unmanned aerial vehicle. An underactuated nonlinear H∞ controller based on the six degrees of freedom dynamic model is designed to control the helicopter attitude and altitude in the...

This work presents an adaptive nonlinear ∞∞ control strategy for variable-speed wind turbines intended to maximize turbine power extraction. The control structure is shown to robustly reject disturbances acting on the system, particularly those introduced by time-varying wind profiles. Remarkably, the controller does not make use of externally sens...

This paper discusses a comparative application of several control laws in a networked control system (NCS) environment. The application is carried out on a two-wheeled personal pendulum vehicle, which is remotely controlled through a Bluetooth wireless communication network. Three control structures are tested and compared: a local linear quadratic...

This paper deals with the application of nonlinear H∞ control techniques to a underactuted mechanical system, which is named as PPCar. A comparison between two nonlinear H∞ control strategies is presented. The first one considers only the position and velocity errors in the cost vector. In the second one the integral position error is added with th...

In this paper, the model for a one-dimensional visual servoing system implemented in our laboratory is initially presented. The system setup is composed by a PUMA robot manipulator, a CCD camera rigidly mounted on the end-effector of the robot, and some image processing hardware. The aim of the system is to keep a desired relative position between...

This paper proposes a distributed estimation and control scheme for discrete linear time-invariant systems. The plant is monitored and controlled by a network of agents that collect information about the system evolution and apply control inputs to drive its behavior. Bounded disturbances and measurement noises are considered through a zonotope-bas...

The paper proposes an innovative estimation and control scheme that enables the distributed monitoring and control of large-scale processes. The proposed approach considers a discrete linear time-invariant process controlled by a network of agents that may both collect information about the evolution of the plant and apply control actions to drive...

This paper is concerned with event-based H 2/H ∞ control design for networked systems with interval time-varying delays. The contributions are twofold. First, conditions for uniform ultimately bounded stability are provided in the H 2/H ∞ event-based context. The relation between the boundedness of the stability region and the threshold that trigge...

Este trabajo presenta una técnica de diseño novedosa para la estimación y control distribuido de sistemas en red. Se considera un proceso discreto de gran escala controlado por una red de agentes que pueden recopilar información acerca de la evolución de la planta y aplicar las acciones de control para mejorar su comportamiento. El diseño propuesto...

This brief proposes an innovative estimation and control scheme that enables the distributed monitoring and control of large-scale processes. The proposed approach considers a discrete linear time-invariant process controlled by a network of agents that may both, collect information about the evolution of the plant, and apply control actions to dri...

In this paper, the sensor scheduling problem for estimation is tackled, in which a set of sensors must share a common network to communicate their measurements. It is shown that, under some mild conditions, a Kalman-based scheduled filter results in a periodic selection of the sensors. In those cases, the computational cost and energy consumption c...

This paper presents the modeling and control of a multi-body air vehicle composed of a miniature aerial vehicle (MAV) and mechanical device, a camera positioner, augmented aerial platform which is considered as the logical next framework within the MAV civil applications. The goal is to improve the current operational profile of visual sensors onbo...

This work presents the modeling and control of a multi-body air vehicle composed of a miniature aerial vehicle (MAV) and a camera positioner subsystem. The goal is to get an actuated system to freely position the camera in the space, disengaging dynamic couplings between the underactuated aircraft and the camera frame due to typical setups, to impr...

This paper presents an unified approach to design suboptimal H2/H∞ controllers for different sorts of time delay systems (TDSs). The system stability is ensured by using a Lyapunov-Krasovski (LK) approach, and it is theoretically demonstrated that the method outperforms H2/H∞ designs in the literature. The improvement comes neither from new LK func...

Almond is the third largest woody crop in Spain. Although traditionally it is considered as a highly drought-tolerant crop with a great adaptability to water shortage, under non-limiting conditions almond significantly improves its yield, generating higher economic profits and increasing irrigation water productivity. Adequate measurements of volum...

In this paper, we propose a quality of service (QoS)-sensitive energy efficiency optimization mechanism for 802.11 networks on the basis of the dynamic and simultaneous adjustment of the content window (W) and retry attempts limit (r) of the media access control (MAC) sublayer. The use of both operational variables let us not only find the optimum...

This paper addresses the formation control problem for fleets of autonomous underwater vehicles (AUVs). The solution is based on the virtual leader approach, with the main goal of designing a control system to cope with the inter-vehicle communication problems, especially significant in underwater environments. The use of kinematic relations allows...

This brief addresses a networked control system problem: scheduling the transmission times in a time division multiple access (TDMA) architecture with a set of sensors embedded in a distributed control application. With TDMA, collisions are avoided, delays are bounded, and with the appropriate schedule, the data rate can be reduced to a minimum req...

This paper presents a predictive and nonlinear robust control strategy to solve the path tracking problem for a quadrotor helicopter. The dynamic motion equations are obtained by the Lagrange-Euler formalism. The control structure is performed through a model-based predictive controller (MPC) to track the reference trajectory and a nonlinear H ∞ co...

This paper studies the design of control systems subject to plant uncertainties and data losses in the channel connecting the plant sensor with the controller. The controller design has two main objectives. The first one is to robustify the control law against plant uncertainties. The other one is to achieve good performance by minimising the varia...

This paper is concerned with the design of mixed H2 ∕ H ∞ controllers for discrete-time delay systems and networked control systems. The controllers are obtained by solving a constrained optimization problem. Those constraints are suitably transformed into linear matrix inequalities, in such a way that the problem is solved using available algorith...

This paper presents a procedure to construct distributed observers for a system consisting in a perturbed linear time-invariant plant being observed by a network of sensor nodes. Based on local measurements of the plant and the information of its neighbours, every node builds an estimation of the plant states. Remarkably, each node can be designed...

This paper proposes a novel distributed estimation and control method for uncertain plants. It is of application in the case of large-scale systems, where each control unit is assumed to have access only to a subset of the plant outputs, and possibly controls a restricted subset of input channels. A constrained communication topology between nodes...

This paper's aim is to present a novel design technique for distributed estimation in networked systems. The problem assumes a network of interconnected agents each one having partial access to measurements from a linear plant and broadcasting their estimations to their neighbours. The objective is to reach a reliable estimation of the plant state...

In this paper a robust PID control strategy via affine parametrization is designed for an multivariable nonlinear unmanned aerial vehicle. The robustness of the controlled system is assured by using the H∞ norm of the weighted complementary sensitivity function. Simulation results carried out using a complete nonlinear model are shown, wherein the...

This paper’s aim is to present a novel distributed estimation technique for linear time-invariant systems with network-induced delays and packet dropouts. The methodology is based on local Luenberger-like observers in combination with consensus strategies. Only neighbors are allowed to communicate and the observer design contemplates the possibilit...

This paper considers the design of a variable structure observer for unknown input estimation and/or fault reconstruction in systems where the process measurements are sampled. It is well known that the principle of the equivalent injection signal from the sliding mode domain can be used for reconstruction of unknown inputs but much of the associat...

This brief tackles the problem of designing suboptimal $H_{2}/H_{\infty}$ controllers for linear networked control systems (NCS) subject to time-varying delays and packet dropouts. The formulation provides state feedback NCS controllers allowing to tradeoff performance and disturbance rejection. The control objective consists in designing an $H_{2}...

Parametric mathematical models of drying plants include balance equations and correlations that should be adjusted for each case depending on the material to be dried and the installation. In some cases, variable parameters are simplified as constants, providing an inaccurate model.This article presents a model of a cocurrent dryer, showing the pro...

En el presente trabajo se estudia el control óptimo con rechazo de perturbaciones L2 para sistemas lineales controlados a través de red. En estos sistemas el lazo de control se cierra utilizando una red de comunicaciones. Entre los problemas que introduce la red se encuentran posibles retrasos, en general aleatorios, así como pérdidas de paquetes....

This paper considers the design of a variable structure observer for discrete-time systems. The output of the system is assumed to be multidimensional, which extends existing work in which unidimensional outputs are assumed. The system is affected by both matched and unmatched disturbances. An ultimately bounded stable variable structure observer i...

In this study, a nonlinear robust control strategy designed for underactuated mechanical systems is proposed in order to solve the path tracking problem for a quadrotor unmanned aerial vehicle. An underactuated nonlinear controller based on the six degrees of freedom dynamic model is designed to control the helicopter attitude and altitude in the i...

In this paper, a Robust Networked Control System (RNCS) subject to data losses constraints is considered. The design will be composed by the calculation of a filter and the synthesis of an H ∞ controller. Both designs will have two purposes. The first one is to robustify the controlled system against plant uncertainties. The other one is the output...

This is a Deliverable Report for the FeedNetBack project (www.feednetback.eu). Networked Control Systems (NCS) are systems in which the sensors or/and the actuators communicate with the controller through a network. Energy saving and robustness to unreliable channels are major challenges in networked control, notably in wireless scenarios. Energy e...

This paper deals with the problem of obtaining delay-dependent stability conditions and L2-gain analysis for a class of nonlinear time-delay systems with norm-bounded and possibly time-varying uncertainties. No restrictions on the derivative of the time-varying delay are imposed, though lower and upper bounds of the delay interval are assumed to be...

This study presents a method to analyse the stability of the feedback interconnection of a class of systems, when the signals associated with the feedback interconnection are sampled asynchronously. A transformation based on L ₂-gain is designed and introduced on both sides of the interconnection. This transformation enlarges the maximum...

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...

Since ancient times, the obsession with security and authenticity has been an issue that has produced the development of diverse technologies, to avoid the access of third persons to information or to private places, and to guarantee the identity of a person with regard to a certain fact. Undoubtedly, in a society like today, which comes naming lik...

In this paper we analyze the scenario where a set of wireless sensors are time-multiplexed in order to reduce the traffic load and energy consumption in a Networked Control System. The possible choices for scheduling the transmission of measures are explored under the concept of periodic feedback patterns, i.e. repeated sequences of different measu...

This paper proposes a model-based control strategy for networked control systems subject to norm bounded disturbances. The communication channel is supposed to be shared with several processes and, therefore, the access to the network needs to be minimized to avoid collisions and packet losses. We propose to use a variable sample rate scheme in whi...

This paper proposes a suboptimal control solution for the L₂-gain disturbance rejection problem for networked control systems. The problem, usually referred as mixed H₂/H_∞, aims at designing a linear state feedback stabilizing controller minimizing a quadratic cost functional subject to a L₂-gain disturba...

Este artículo presenta una aplicación de control para la estabilización inercial de una plataforma de dos grados de libertad (2-GDL). El objetivo de la aplicación es, en primer lugar, controlar las posiciones angulares de la plataforma en ausencia de perturbaciones inerciales y en segundo lugar, controlar las velocidades de la plataforma medidas re...

This paper proposes an optimal control solution for the L₂-gain disturbance rejection problem for networked control systems. The problem, usually referred as mixed H₂/H_∞, aims at designing a linear stabilizing controller minimizing a given cost function subject to a L₂-gain disturbance rejection constrain...

This paper presents a control application for the inertial stabilization of a gyroscopic platform with two degrees of freedom (2-DOF). The purposes of this application are, first, to control the angular positions of the platform in the absence of inertial disturbances and second, to control velocities measured in an inertial frame, while rejecting...

This article presents a survey of the different automatic control techniques that have been applied to control the outlet temperature of solar plants with distributed collectors during the last 25 years. Different aspects of the control problem involved in this kind of plants are treated, from modeling and simulation approaches to the different bas...

This paper is concerned with the stability analysis for uncertain systems with interval time-varying delays. An appropriate class of Lyapunov-Krasovskii functionals is proposed and, splitting the known bounds of the delay interval in two subintervals, a new delay-dependent criterion is derived. In addition, we resort to the use of a polytope to int...

This paper presents an integral predictive and nonlinear robust control strategy to solve the path following problem for a quadrotor helicopter. The dynamic motion equations are obtained by the Lagrange–Euler formalism. The proposed control structure is a hierarchical scheme consisting of a model predictive controller (mpc) to track the reference t...

Este trabajo presenta una metodología para el modelado de secaderos rotatorios de s ólidos en isocorriente. El planteamiento del modelo está basado tanto en ecuaciones diferenciales paramétricas como en el uso de algunas correlaciones que permiten simplificar su tratamiento. En el trabajo se muestran aspectos de modelado que son comunes a la mayorí...

This paper presents a methodology for the modelling of co-current rotary dryers. The model is based in parametric differential equations and in the use of some correlations that allow simplifying the processing. In the work, which aspects of modelling are common to most installations are distinguished, and which ones are particular of each one depe...

This paper presents a method to analyze the stability of the feedback interconnection of a class of systems when the sampled signal associated to the feedback interconnection is asynchronous. In order to guarantee a stable interconnection, a combined transformation based on L2 - gain criteria is introduced before sampling and sending the informatio...

This paper presents a method to analyze the stability of the feedback interconnection of a class of systems when the sampled signal associated to the feedback interconnection is asynchronous. In order to guarantee a stable interconnection, a combined transformation based on L2 - gain criteria is introduced before sampling and sending the informatio...