C. Sagues

• PhD
• Professor (Full) at University of Zaragoza

Short-stroke reluctance actuators, such as electromechanical relays and solenoid valves, often experience strong impacts at the end of standard switching operations, leading to problems like contact bounces, mechanical wear or acoustic noise. This paper introduces a novel iterative learning controller for tracking the actuator position during switc...

In the stochastic estimation context, the absence of measurement information at the state estimator during large intervals can cause a divergence in the uncertainty of the estimates. This issue is aggravated when strategies to reduce communication, such as event-triggering mechanisms (ETMs), are used if an appropriate design is not made. Particular...

Los sistemas de levitación magnética han sido utilizados en la enseñanza de determinados conceptos de electrónica y control automático. Son dispositivos con un evidente atractivo para los estudiantes, que permiten ilustrar los efectos de las no linealidades presentes en la realidad, tanto aquellas debidas a la física del problema como las asociadas...

Electromagnetic relays and solenoid actuators are commonly used for their bistable behavior, which allows for switching between two states in electrical, pneumatic, or hydraulic circuits, among other applications. Although there has been extensive research on modeling, estimation, and control of these electromechanical systems, a gap remains in the...

We present AVOCADO (AdaptiVe Optimal Collision Avoidance Driven by Opinion), a novel navigation approach to address holonomic robot collision avoidance when the degree of cooperation of the other agents in the environment is unknown. AVOCADO departs from a Velocity Obstacle's formulation akin to the Optimal Reciprocal Collision Avoidance method. Ho...

Electromechanical relays and contactors suffer from strong collisions at the end of the switching operations. This causes several undesirable phenomena, such as clicking, mechanical wear and contact bounce. Thus, there is great interest in mitigating these switching impacts while keeping the advantageous features of these devices. This paper propos...

This paper introduces a novel distributed optimization technique for networked systems, which removes the dependency on specific parameter choices, notably the learning rate. Traditional parameter selection strategies in distributed optimization often lead to conservative performance, characterized by slow convergence or even divergence if paramete...

In networked control applications, event-triggering mechanisms (ETMs) reduce the communication load while ensuring performance guarantees. However, the design of ETMs is becoming increasingly complex, particularly for decentralized multi-agent and consensus setups, where the condition used to trigger communication might incorporate the agent's loca...

Los sistemas de levitación magnética han sido utilizados en la enseñanza de determinados conceptos de electrónica y control automático. Son dispositivos con un evidente atractivo para los estudiantes, que permiten ilustrar los efectos de las no linealidades presentes en la realidad, tanto aquellas debidas a la física del problema como las asociadas...

This paper presents a novel accelerated distributed algorithm for unconstrained consensus optimization over static undirected networks. The proposed algorithm combines the benefits of acceleration from momentum, the robustness of the alternating direction method of multipliers, and the computational efficiency of gradient tracking to surpass existi...

Electromechanical relays and contactors suffer from strong collisions at the end of the switching operations. This causes several undesirable phenomena, such as clicking, mechanical wear and contact bounce. Thus, there is great interest in mitigating these switching impacts while keeping the advantageous features of these devices. This paper propos...

Robotic manipulation of deformable objects is challenging due to the great variety of materials and shapes. This task is even more complex when the object is also fragile, and the allowed amount of deformation needs to be constrained. For the goal of driving a thin fragile deformable object to a target 2D position and orientation, we propose a mani...

We present a formation controller for a team of mobile robots, modelled with double-integrator dynamics, to manipulate deformable objects grasped around their contour. The manipulation task is defined as reaching a target configuration consisting of a desired shape, scale, position and orientation of the formation in 2D, while preserving the integr...

El excesivo consumo energético es actualmente un gran problema para la sociedad. Parte de la solución a este problema pasa por mejorar la eficiencia de los sistemas de uso extensivo, particularmente los sistemas térmicos. Una forma de abordarlo es mediante la construcción de modelos orientados a la mejora energética. Estos modelos dependen de parám...

Los sistemas de levitación magnética han sido utilizados en la enseñanza de determinados conceptos de electrónica y control automático. Son dispositivos con un evidente atractivo para los estudiantes, que permiten ilustrar los efectos de las no linealidades presentes en la realidad, tanto aquellas debidas a la física del problema como las asociadas...

Target tracking is a popular problem with many potential applications. There has been a lot of effort on improving the quality of the detection of targets using cameras through different techniques. In general, with higher computational effort applied, i.e., a longer perception-latency, a better detection accuracy is obtained. However, it is not al...

The graph identification problem consists of discovering the interactions among nodes in a network given their state/feature trajectories. This problem is challenging because the behavior of a node is coupled to all the other nodes by the unknown interaction model. Besides, high-dimensional and nonlinear state trajectories make difficult to identif...

Los algoritmos de visión basados en redes neuronales requieren grandes cantidades de datos etiquetados de forma precisa. Obtener estos datos de forma manual es un proceso muy costoso. En este trabajo se propone utilizar motores gráficos para generar imágenes etiquetadas automáticamente con las que entrenar redes neuronales.

This work is devoted to the problem of distributed target tracking when a team of robots detect the target through a variable perception-latency mechanism. A reference for the robots to track is constructed in terms of a desired formation around the estimation of the target position. However, it is noted that due to the perception-latency, classica...

The outer Lowner-John method is widely used in sensor fusion applications to find the smallest ellipsoid that can approximate the intersection of a set of ellipsoids, described by positive definite covariance matrices modeling the quality of each sensor. We propose a distributed algorithm to solve this problem when these matrices are defined over t...

This work addresses the problem of dynamic consensus, which consists of estimating the dynamic average of a set of time-varying signals distributed across a communication network of multiple agents. This problem has many applications in robotics, with formation control and target tracking being some of the most prominent ones. In this work, we prop...

The outer Löwner-John method is widely used in sensor fusion applications to find the smallest ellipsoid that can approximate the intersection of a set of ellipsoids, described by positive definite covariance matrices modeling the quality of each sensor. We propose a distributed algorithm to solve this problem when these matrices are defined over t...

This paper presents a novel solution for the discrete time dynamic average consensus problem. Given a set of time-varying input signals over the nodes of an undirected graph, the proposed algorithm tracks, at each node, the input signals’ average. The algorithm is based on a sequence of consensus stages combined with a second order diffusive protoc...

This paper presents ECO-DKF, the first E vent-Triggered and C ertifiable O ptimal D istributed K alman F ilter. Our algorithm addresses two major issues inherent to Distributed Kalman Filters: (i) fully distributed and scalable optimal estimation and (ii) reduction of the communication bandwidth usage. The first requires to solve an NP-...

Visual object tracking under challenging conditions of motion and light can be hindered by the capabilities of conventional cameras, prone to producing images with motion blur. Event cameras are novel sensors suited to robustly perform vision tasks under these conditions. However, due to the nature of their output, applying them to object detection...

This article presents a novel control strategy to herd groups of noncooperative evaders by means of a team of robotic herders. In herding problems, the motion of the evaders is typically determined by strongly nonlinear and heterogeneous reactive dynamics, which makes the development of flexible control solutions a challenging problem. In this...

The invention relates to a home appliance device, in particular a hob device, comprising a control unit, which is provided to actuate at least one switch and to supply at least one driving signal for completely transferring the switch in at least one first switching process from at least one first switch position to at least one second switch posit...

This paper solves the problem of herding countless evaders by means of a few robots. The objective is to steer all the evaders towards a desired tracking reference while avoiding escapes. The problem is very challenging due to the highly complex repulsive evaders’ dynamics and the underdetermined states to control. We propose a solution that is bas...

Visual object tracking under challenging conditions of motion and light can be hindered by the capabilities of conventional cameras, prone to producing images with motion blur. Event cameras are novel sensors suited to robustly perform vision tasks under these conditions. However, due to the nature of their output, applying them to object detection...

In the problem of autonomous transport of deformable objects, we propose a multirobot approach for steering a large object to a target configuration (object dimensions, orientation, and position). Firstly, we present a deformation model based on the evolution over time of the dimensions and rotation of the object's bounding box (BB). We consider th...

This paper solves the problem of herding countless evaders by means of a few robots. The objective is to steer all the evaders towards a desired tracking reference while avoiding escapes. The problem is very challenging due to the highly complex repulsive evaders' dynamics and the underdetermined states to control. We propose a solution that is bas...

This paper presents LEMURS, an algorithm for learning scalable multi-robot control policies from cooperative task demonstrations. We propose a port-Hamiltonian description of the multi-robot system to exploit universal physical constraints in interconnected systems and achieve closed-loop stability. We represent a multi-robot control policy using a...

Electromagnetic switching devices such as electromechanical relays and solenoid valves suffer from impacts and mechanical wear when they are activated using a constant-voltage policy. This paper presents a new control approach that aims at achieving soft landing in these devices, i.e., a movement without neither impacts nor bouncing. The hybrid non...

La identificabilidad es una propiedad esencial de los modelos dinámicos cuyo estudio debe ser abordado antes de iniciar cualquier procedimiento de estimación paramétrica. Sin embargo, este análisis generalmente ha sido ignorado en la literatura con unas pocas excepciones, como por ejemplo en el estudio de los sistemas biológicos. En este trabajo, s...

Presentation of article published in IEEE Transactions on Control Systems Technology. DOI: 10.1109/TCST.2021.3120909.

Electromagnetic relays and solenoid actuators are commercial devices that generally exhibit bistable behavior. In fact, this is the reason why they are extensively used to switch between two possible configurations in electrical, pneumatic, or hydraulic circuits, among others. Although the state of the art is extensive on modeling, estimation, and...

Identifiability is an essential property of a dynamical model whose study should be addressed before performing any parameter estimation procedure. In this work, we study the structural identifiability of a heat transfer system by making use of the local state isomorphism theorem for two scenarios based on the available experimental measurements.

Visual object tracking under fast motions can be hindered by conventional cameras, which are prone to producing blurry images. Event cameras are better suited for this task, but applying them to object tracking is non-trivial. We propose a framework to take advantage of these sensors by using deep learning techniques.

This article presents a novel state estimator for short-stroke reluctance actuators, intended for soft-landing control applications in which the position cannot be measured in real time. One of the most important contributions regards the system modeling for the estimator. The discrete state of the hybrid system is treated as an input. Moreover, th...

This work addresses the problem of distributed formation tracking for a group of follower holonomic mobile robots around a reference signal. The reference signal is comprised of the geometric center of the positions of multiple leaders. This work's main contribution is a novel Modulated Distributed Virtual Observer (MDVO) for the reference signal....

This paper presents a novel control strategy to herd groups of non-cooperative evaders by means of a team of robotic herders. In herding problems, the motion of the evaders is typically determined by strongly nonlinear and heterogeneous reactive dynamics, which makes the development of flexible control solutions a challenging problem. In this conte...

In this paper, we propose a formation control system for deforming and transporting simultaneously a deformable object with a team of robots, modeled with double-integrator dynamics. The goal is to reach a target configuration, defined as a combination of shape, scale, orientation and position of the formation. We augment this controller with a set...

This article addresses the problem of average consensus in a multi-agent system when the desired consensus quantity is a time varying signal. Recently, the EDCHO protocol leveraged high order sliding modes to achieve exact consensus under a constrained set of initial conditions, limiting its applicability to static networks. In this work, we propos...

This article addresses the problem of average consensus in a multi-agent system when the desired consensus quantity is a time varying signal. Recently, the EDCHO protocol leveraged high order sliding modes to achieve exact consensus under a constrained set of initial conditions, limiting its applicability to static networks. In this work, we propos...

This article addresses the problem of average consensus in a multi-agent system when the desired consensus quantity is a time varying signal. Although this problem has been addressed in existing literature by linear schemes, only bounded steady-state errors have been achieved. Other approaches have used first order sliding modes to achieve zero ste...

Perception over time is a critical problem in those cases where deformable objects are manipulated. The goal of this study is to cover the contour of an object along a deformation process and according to a prescribed coverage objective, in terms of visibility and resolution. This task is carried out by a set of limited field-of-view cameras. We pr...

This letter addresses the problem of distributed formation tracking for a group of follower holonomic mobile robots around a reference signal. The reference signal is comprised of the geometric center of the positions of multiple leaders. This letter’s main contribution is a novel Modulated Distributed Virtual Observer (MDVO) for the reference sign...

In this paper, we propose a novel system to transport 2D cloth-like deformable objects with mobile manipulators and without collisions along a known path. First, a new deformation model that allows for real-time shape prediction, based on the paradigm of deformable bounding box, is presented. Then, observability index maximization is applied to obt...

This article addresses the problem of average consensus in a multi-agent system when the desired consensus quantity is a time varying signal. Although this problem has been addressed in existing literature by linear schemes, only bounded steady-state errors have been achieved. Other approaches have used first order sliding modes to achieve zero ste...

The optimal fusion of estimates in a Distributed Kalman Filter (DKF) requires tracking of the complete network error covariance, which is a problem in terms of memory and communication bandwidth. A scalable alternative is to fuse estimates under unknown correlations, updating the local estimates and error covariance matrix as the solution of an opt...

This paper presents an efficient and accurate dynamical model of reluctance actuators, suitable for prediction and control applications. It is a hybrid lumped-parameter state-space model that takes into account the mechanical and electromagnetic dynamics, including eddy currents, flux fringing, magnetic hysteresis and saturation. Special emphasis i...

In this article, we consider a scenario of cooperative task servicing, with a team of heterogeneous robots with different maximum speeds and communication radii, in charge of keeping the network intermittently connected. We abstract the task locations into a one-dimensional cycle graph that is traversed by the communicating robots, and we discuss i...

Some electromagnetic actuators suffer from high velocity impacts during non-controlled switching operations, which cause contact bouncing, mechanical wear, and acoustic noise. Soft-landing control strategies aim at minimizing the impact velocities of these devices to improve their performance. This paper presents a sliding-mode controller for soft...

There is great interest in minimizing the impact forces of reluctance actuators during commutations, in order to reduce contact bouncing, acoustic noise and mechanical wear. In this regard, a run-to-run control algorithm is proposed to decrease the contact velocity, by exploiting the repetitive operations of these devices. The complete control is p...

This article presents a novel control strategy based on predictor‐feedback delay compensation for multiagent systems to reach a prescribed target formation under unknown but bounded communication delays and switching communication topology. Both communication delays and network topology can be subjected to arbitrarily‐fast time variations. The key...

This paper investigates new coordinate-free formation control strategies of multi-agent systems to overcome the negative effects of time delays. To this end, we present a single predictor-feedback scheme to compensate the multiple communication delays, assumed to be unknown but bounded and arbitrarily-fast time-varying. Although delays cannot exact...

A key problem in multi-agent systems is the distributed estimation of the localization of agents in a common reference from relative measurements. Estimations can be referred to an anchor node or, as we do here, referred to the weighted centroid of the multi-agent system. We propose a Jacobi Over—Relaxation method for distributed estimation of the...

This article addresses the problem of average consensus by a multi-agent system when the desired consensus quantity is a time varying signal, in particular the average of individual time varying signals localized at the agents. Although this problem has been addresses in existing literature by linear schemes, only bounded steady-state errors has be...

In this article, we tackle the problem of persistently covering a complex non-convex environment with a team of robots. We consider scenarios where the coverage quality of the environment deteriorates with time, requiring every point to be constantly revisited. As a first step, our solution finds a partition of the environment where the amount of w...

This paper presents a formation control synthesis method for a multiagent system to reach a prescribed rigid formation under communication delays and time-varying switching communication topology. The proposed control scheme only requires the knowledge of relative measurements of some neighbor agents, expressed in each agent's local frame, to be im...

This paper deals with the design and analysis of open-loop soft-landing control policies for a class of nonlinear actuators. A third-order nonlinear parametric model is firstly presented and the particularities of the systems under study are highlighted. Then, time-optimal and energy-optimal trajectories are analytically derived by means of the Pon...

There is great interest in minimizing the impact forces and bounces of reluctance actuators during commuta-tions, in order to reduce acoustical noise and wear. In that regard, a model-free run-to-run control algorithm is presented to decrease the contact velocities, by exploiting the repetitive operations of theses devices. The problem is mathemati...

A novel hybrid dynamical model for single-coil, short-stroke reluctance actuators is presented in this paper. The model, which is partially based on the principles of magnetic equivalent circuits, includes the magnetic phenomena of hysteresis and saturation by means of the generalized Preisach model. In addition, the eddy currents induced in the ir...

We propose a novel control method to enclose a moving target in a two-dimensional setting with a team of agents forming a prescribed geometric pattern. The approach optimises a measure of the overall agent motion costs, via the minimisation of a suitably defined cost function encapsulating the pattern rotation and scaling. We propose two control la...

Several modeling, estimation, and control strategies have been recently presented for simple reluctance devices like solenoid valves and electromagnetic switches. In this paper, we present a new algorithm to online estimate the flux linkage and the electrical time-variant parameters of these devices, namely the resistance and the inductance, only b...

Modeling the reluctance of an electromagnetic actuator is a critical step to analyze its dynamics and design model-based controllers. On the one hand, analytical expressions based on either theoretical or empirical models often lack accuracy due to model inconsistencies. On the other, numerical methods are much more precise but require exact inform...

This paper investigates the robust stability of a multiagent system moving to a desired rigid formation in presence of unknown time-varying communication delays and actuator faults. Each agent uses relative position measurements to implement the proposed control method, which does not require common coordinate references. However, the presence of t...

This paper investigates the convergence of nonholonomic multiagent coordinate‐free formation control to a prescribed target formation subject to communication delays by means of Lyapunov‐Krasovskii approach and smooth state‐feedback control laws. As a result, an iterative algorithm based on linear matrix inequalities is provided to obtain the worst...

We present a novel vision-based control method to make a group of ground mobile robots achieve a specified formation shape with unspecified size. Our approach uses multiple aerial control units equipped with downward-facing cameras, each observing a partial subset of the multirobot team. The units compute the control commands from the ground robots...

In this paper, we propose a periodic solution to the problem of persistently covering a finite set of interest points with a group of autonomous mobile agents. These agents visit periodically the points and spend some time carrying out the coverage task, which we call coverage time. Since this periodic persistent coverage problem is NP-hard, we spl...

Multi robot teams composed by ground and aerial vehicles have gained attention during the last years. We present a scenario where both types of robots must monitor the same area from different view points. In this paper we propose two Lloyd-based tracking strategies to allow the ground robots (agents) follow the aerial ones (targets), keeping the c...

This paper presents a novel nonlinear state observer with discrete-time measurements for estimating the plunger position of linear travel solenoid valves. The observer is an unscented Kalman filter (UKF) for nonlinear systems that iteratively calculates an estimated mean and covariance of the state. It is based on a basic lumped parameter model, wh...

This paper investigates the use of time delay compensation methodology based on Smith Predictor applied to the control of a group of agents moving on a plane to a desired rigid geometric configuration. The unavoidable presence of time delays inherent to the communication links between agents is known to have a negative impact on the system performa...

As Chaps. 2 and 3 of the monograph have illustrated, an effective way to address vision-based control when the robots (and their attached cameras) move in a planar environment is to use omnidirectional vision and 1D multiview models. This provides interesting properties in terms of accuracy, simplicity, efficiency and robustness. After exploring th...

The first problem addressed in the monograph is how to enable mobile robots to autonomously navigate toward specific positions in an environment. Vision sensors have often been used for this purpose, supporting a behavior known as visual homing, in which the robot’s target location is defined by an image. This chapter describes a novel visual homin...

In the last chapter of the book, we provide brief concluding remarks on the contents that have been presented, and discuss a number of ideas that may be attractive to pursue in future research efforts.

This chapter continues the study of methods for vision-based stabilization of mobile robots to desired locations in an environment, focusing on an aspect that is critical for successful real-world implementation, but often tends to be overlooked in the literature: the control inputs employed must take into account the specific motion constraints of...

Cameras are versatile and relatively low-cost sensors that provide a lot of useful data. Thanks to these remarkable properties, it is possible to envision a range of different setups when considering vision-based multirobot control tasks. For instance, the vision sensors may be carried by the robots that are to be controlled, or external to them. I...

It is undoubtedly interesting, from a practical perspective, to solve the problem of multirobot formation stabilization in a decentralized fashion, while allowing the agents to rely only on their independent onboard sensors (e.g., cameras), and avoiding the use of leader robots or global reference frames . However, a key observation that serves as...

This paper presents a distributed method to estimate the algebraic connectivity of fixed undirected communication graphs. The proposed algorithm uses bisection to estimate the second smallest eigenvalue of the Laplacian matrix associated to the graph. In order to decide the sub-interval in which the eigenvalue is contained, a distributed averaging...

The design of domestic cooking stoves is usually optimized by performing time-consuming cooking experiments, often using frying of pancakes as a standard. Simulation of cooking processes may reduce the number of experiments used in the development of the cooking stoves, saving time and resources. In this work we propose a model of contact frying of...

Contact bounce is probably the most undesirable phenomenon of electromagnetic switches. It reduces the performance of relays and contactors and is directly related to some of the processes that result in the destruction of the device. In this paper, a complete formulation of the problem is provided and a new strategy inspired by Run-to-Run control...

This monograph introduces novel methods for the control and navigation of mobile robots using multiple-1-d-view models obtained from omni-directional cameras. This approach overcomes field-of-view and robustness limitations, simultaneously enhancing accuracy and simplifying application on real platforms. The authors also address coordinated motion...

In this paper, we present a novel distributed method to stabilize a set of agents moving in a two dimensional environment to a desired rigid formation. In our approach, each agent computes its control input using the relative positions of a set of formation neighbors but, contrary to most existing works, this information is expressed in the agent's...

In this paper, we address the problem of persistently covering an environment with a group of mobile robots. In contrast to traditional coverage, in our scenario the coverage level of the environment is always changing. For this reason, the robots have to continually move to maintain a desired coverage level. In this context, our contribution is a...