Artículos de publicaciones periódicas

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Control inteligente VS. LPV : Comparación aplicada a un cuatrirotor de dos brazos
(2022) Silva Rodrigues, Reurison; Ghersin, Alejandro S.; Giribet, Juan
Tomando como ejemplo de aplicación, un vehículo aéreo no tripulado con dos brazos y cuatro rotores, en el presente trabajo se lleva cabo una comparación del desempeño de dos sistemas de control. Uno de estos controles fue diseñado mediante técnicas lineales de parámetros variantes, mientras que el otro se basa en la estrategia denominada PID inteligente, técnica adaptativa basada en controles libres de modelo. Ambos controles atacan el problema de tolerancia a fallas con diferentes enfoques para adaptarse a dos casos de fallas, en uno y en dos rotores. Las fallas consideradas son de tipo total y se conocen de ellas el momento en que se producen y el actuador en el cual ocurrió la falla. En este escenario, se lleva a cabo la comparación.
Analysis of the impact of artificial networks in system-level EMC tests
(2022) Gardella, Pablo J.; Mariani, Eduardo
The impedance of an Off-The-Shelf Artificial Network (OTS-AN) and a custom made High-Frequency Artificial Network (HF-AN) were analysed and compared. It is showed that in order to meet the requirements of automotive standards, such as Bulk Current Injection (BCI) from ISO 11452-4 as well as both Conducted and Radiated Emissions (CE, RE) from CISPR 25, the HF-AN is needed. System-level circuit simulations were run using S-parameters for quantifying the impact of these two models in the previously mentioned EMC tests. Above 50 MHz, up to 3.5 dB and 4.3 dB differences were found on the transferimpedance of CE and in the Common-Mode to Differential-Mode conversion of BCI, respectively. On the other hand, in RE the OTS-AN leaded to an overestimation of the emission profile in the 300 MHz and 800 MHz band as high as 5.3 dB. Besides that, it is showed that the OTS-AN behaves as a source of non-constant uncertainty, specially above 50 MHz. Finally, the issues in terms of reproducibility, repeatability and accuracy that arise from the non-RF connectors in the OTS-AN are discussed and a metric for test-bench comparison and validation is proposed.
Analysis and design of a tilted rotor hexacopter for fault tolerance
(IEEE, 2016) Giribet, Juan I.; Sanchez-Peña, Ricardo; Ghersin, Alejandro S.
A proof is presented of how a hexagon-shaped hexacopter can be designed to keep the ability to reject disturbance torques in all directions while counteracting the effect of a failure in any of its motors. The method proposed is simpler than previous solutions, because it does not require change of the motor rotation direction or in-flight mechanical reconfiguration of the vehicle. It consists of tilting the rotor a small fixed angle with respect to the vertical axis. Design guidelines are presented to calculate the tilt angle to achieve fault-tolerant attitude control without losing significant vertical thrust. It is also formally proved that the minimum number of unidirectional rotating motors needed to have fault tolerance is 6 and that this can be achieved by tilting their rotors. This proof is essentially a control allocation analysis that recovers in a simple way a result already known: the standard configuration (without tilting the motors) is not fault tolerant. A simulation example illustrates the theory.
On the dynamics of a single-bit stochastic-resonance memory device
(2010-07) Ibáñez, Santiago Agustín; Fierens, Pablo Ignacio; Perazzo, Roberto P. J.; Patterson, Germán; Grosz, Diego
"The increasing capacity of modern computers, driven by Moore’s Law, is accompanied by smaller noise margins and higher error rates. In this paper we propose a memory device, consisting of a ring of two identical overdamped bistable forward-coupled oscillators, which may serve as a building block in a larger scale solution to this problem. We show that such a system is capable of storing a single bit and its performance improves with the addition of noise. The proposed device can be regarded as asynchronous, in the sense that stored information can be retrieved at any time and, after a certain synchronization time, the probability of erroneous retrieval does not depend on which oscillator is being interrogated. We characterize memory persistence time and show it to be maximized for the same noise range that both minimizes the probability of error and ensures synchronization. We also present experimental results for a hard-wired version of the proposed memory, consisting of a loop of two Schmitt triggers. We show that this device is capable of storing a single bit and does so more efficiently in the presence of noise."
Analysis of the Impact of the monitoring equipment on the common-mode to differential-mode conversion in bulk current injection tests
(2021) Gardella, Pablo; Marini, Eduardo
"In this paper, the common-mode to differential mode conversion in a Bulk Current Injection (BCI) test setup is analyzed in the presence of an optical fiber transmitter. A modular-basis analysis based on S-parameters measurements and Electromagnetic simulations has been performed. It is shown that the loading effects can change the insertion losses from the RF amplifier to the Devices Under Test, even at frequencies as low as 10MHz by 2dB and up to 23dB at worst cases. The study has been undertaken with the substitution and closed-loop methods. Quantification of this problem as well as mitigation strategies are proposed, analyzed and evaluated with the aim of improving the accuracy of BCI simulations at early-design stages. Considering the significant cost of redesigning at an advanced point in the product development cycle, the presented work expects to raise awareness about how even small changes in the BCI setup can remarkably compromise the outcome."
Training a gaming agent on brainwaves
(2020-12-07) Bartolomé, Francisco; Moreno, Juan; Navas, Natalia; Vitali, José; Ramele, Rodrigo; Santos, Juan Miguel
"Error-related potential (ErrP) are a particular type of Event-Related Potential (ERP) elicited by a person attending a recognizable error. These Electroencephalographic (EEG) signals can be used to train a gaming agent by a Reinforcement Learning (RL) algorithm to learn an optimal policy. The experimental process consists of an observational human critic (OHC) observing a simple game scenario while their brain signals are captured. The game consists of a grid, where a blue spot has to reach a desired target in the fewest amount of steps. Results show that there is an effective transfer of information and that the agent successfully learns to solve the game efficiently, from the initial 97 steps on average required to reach the target to the optimal number of 8 steps. Our results are expressed in threefold: (i) the mechanics of a simple grid-based game that can elicit the ErrP signal component, (ii) the verification that the reward function only penalizes wrong steps, which means that type II error (not properly identifying a wrong movement) does not affect significantly the agent learning process; (iii) collaborative rewards from multiple observational human critics can be used to train the algorithm effectively and can compensate low classification accuracies and a limited scope of transfer learning schemes."
Aerial multi-camera robotic jib crane
(2021-03) Moreno, Patricio; Presenza, Juan F.; Mas, Ignacio; Giribet, Juan I.
"A formulation based on a team of unmanned aerial vehicles operating as a fully articulated multi-camera jib crane is proposed for the application of aerial cinematography. An optimization-based controller commands the formation to follow an artistic trajectory defined by the director of photography, while actively avoiding collisions and cameras’ mutual visibility. The proposed scheme, based on the cluster-space formulation, presents an intuitive way of maneuvering the virtual camera fixture while automatically adjusting the motions by imposing artistic and safety constraints, facilitating the operator task."
Revisiting soliton dynamics in fiber optics under strict photon-number conservation
(2021) Linale, N.; Fierens, Pablo Ignacio; Grosz, Diego F.
"We revisit the complex interplay between the Raman-induced frequency shift (RIFS) and the effect of selfsteepening (SS) in the propagation of solitons, and in the framework of an equation that ensures strict conservation of the number of photons. The generalized nonlinear Schrödinger equation (GNLSE) is shown to severely fail in preserving the number of photons for sub-100-fs solitons, leading to a large overestimation of the frequency shift. Furthermore, when considering the case of a frequency-dependent nonlinear coefficient, the GNLSE also fails to provide a good estimation of the time shift experienced by the soliton. We tackle these shortcomings of the GNLSE by resorting to the recently introduced photon-conserving GNLSE (pcGNLSE) and study the interplay between the RIFS and selfsteepening. As a result, we make apparent the impact of higherorder nonlinearities on short-soliton propagation and propose an original and direct method for the estimation of the second-order nonlinear coefficient."
A direct method for the simultaneous estimation of self-steepening and the fractional Raman contribution in fiber optics
(2021-06) Linale, N.; Bonetti, Juan I.; Fierens, Pablo Ignacio; Hernández, Santiago M.; Grosz, Diego
"We propose an original, simple, and direct method for the simultaneous estimation of the selfsteepening parameter and the fractional Raman contribution in fiber optics. Our proposal is based on the dependence of the modulation instability gain on both parameters, as obtained from a linear stability analysis of the newly introduced photon-conserving generalized nonlinear Schrödinger equation (pcGNLSE), and requires only the CW or quasi-CW pumping of the waveguide under test and a few direct spectral measurements. Further, we demonstrate the feasibility of the estimation procedure by means of detailed simulations for typical waveguide parameters in relevant spectral ranges. Last, we discuss the range of applicability of the proposed method and compare its results, advantages, and disadvantages with a recently introduced method based on short-pulse dynamics."
Model for frequency-dependent nonlinear propagation in 2D-decorated nanowires
(2021-03) Linale, N.; Bonetti, Juan I.; Sánchez, Alfredo D.; Fierens, Pablo Ignacio; Grosz, Diego
"We show that 2D-decorated silicon nanowires exhibit a strong frequency dependence of the real (Kerr) and imaginary (two-photon absorption) nonlinear coefficients. In this setting, we demonstrate that the usual extension of the nonlinear Schr¨odinger equation used to model propagation in this type of waveguides is rendered inadequate. Hence, we introduce a new modeling framework to tackle the frequency dependence of the nonlinear coefficients in 2D-decorated." nanowires, and present an example of its application to the relevant case of supercontinuum generation in graphene- and graphene-oxide decorated silicon nanowires
Control robusto H∞ para la velocidad de desplazamiento de un UAV en base a estimación de flujo óptico
(2021-07) Ghersin, Alejandro S.; Giribet, Juan I.; Luiso, Javier E.; Tournour, Andrés
"Se presenta el diseño del control para la velocidad de desplazamiento de un vehículo aéreo de seis rotores. La técnica de diseño utilizada es el control optimo en H-infinito con el objetivo de conseguir rendimiento robusto ante la incertidumbre en el modelo de la dinámica de la velocidad de desplazamiento. Se considera que buena parte de la incertidumbre es atribuible a retardos de tiempo inciertos que introduce el propio algoritmo que se utiliza para estimar la velocidad de desplazamiento. El vehículo realiza a bordo la estimación de esta última a través de un sensor de flujo óptico implementado con una cámara y un procesador de alto nivel en el cual además se implementa la ley de control. Junto con el diseño del control, se muestra el procedimiento de identificación de sistemas utilizado para conseguir una descripción de la dinámica a través de una familia de plantas con incertidumbre dinámica global a través de la toma de datos experimentales. Finalmente se exhiben resultados experimentales con la implementación del sistema de control completo."
A literature review on embedded systems
(2020-02) De Micco, Luciana; Vargas, Fabian; Fierens, Pablo Ignacio
"Embedded system design is crucial for the development of industry, technology, and science, and it is an area that has significantly grown in recent years throughout Latin America, both in academia and in industry. Embedded System (ES) refers to electronic equipment with a computing core which, unlike a personal computer, is designed to meet a specific function and is usually optimized to satisfy strict requirements of processing time, reliability, power consumption, size, and cost. With the advancement of research on the domains of Internet of Things (IoT), Computing Edge (CE) and Cloud Computing (CC) and their endless application possibilities, ESs have gained new roles and assumed unquestionable importance in our daily lives. In this article, we make a brief review of the relevant literature in the area of embedded systems in the Latin America region during recent years."
Multi-UAV specification and control with a single pilot-in-the-loop
(2020-10) Moreno, Patricio; Esteva, Santiago; Mas, Ignacio; Giribet, Juan I.
"This work presents a multi-unmanned aerial vehicle formation implementing a trajectory-following controller based on the clusterspace robot coordination method. The controller is augmented with a feed-forward input from a control station operator. This teleoperation input is generated by means of a remote control, as a simple way of modifying the trajectory or taking over control of the formation during flight. The cluster-space formulation presents a simple specification of the system’s motion and, in this work, the operator benefits from this capability to easily evade obstacles by means of controlling the cluster parameters in real time. The proposed augmented controller is tested in a simulated environment first, and then deployed for outdoor field experiments. Results are shown in different scenarios using a cluster of three autonomous unmanned aerial vehicles."
Fault tolerance analysis for a class of reconfigurable aerial hexarotor vehicles
(2020-08) Pose, Claudio D.; Giribet, Juan I.; Mas, Ignacio
"Several works have addressed the issue of fault tolerance in multirotors in case of a rotor total failure, particularly their ability to keep full independent control of attitude and altitude. It has been proven that to achieve this, a minimum of six rotors is needed. In this work, the performance of several standard and nonstandard hexarotor structures is analyzed, both for a nominal case (without failure) and in the case where one of the actuators is under failure (incapability to exert thrust). The performance is shown in terms of maximum rotational torque and vertical force that the vehicle can exert. The main contribution of this work is the proposal and analysis of converting these vehicles into reconfigurable ones through the addition of a minimum number of servomotors, to deal with failures and to greatly improve the maneuverability under these conditions, in order to identify the reconfigurable structure with the best performance. An experimental demonstration in an outdoor environment is shown for the proposed reconfigurable structure with best performance in case of a full rotor failure."
Guest editorial special issue on embedded systems
(2020-02) De Micco, Luciana; Vargas, Fabian; Fierens, Pablo Ignacio
"La temática de sistemas embebidos (SE) tiene una enorme relevancia debido al gran número de aplicaciones en muy diversas áreas. En los últimos años ha habido un interés especial animado por las áreas emergentes de la Internet de las Cosas (IoT, según la sigla en inglés) y la Industria 4.0."
A non-centralized predictive control strategy for wind farm active power control: a wake-based partitioning approach
(2020-05) Siniscalchi-Minna, Sara; Bianchi, Fernando D.; Ocampo-Martínez, Carlos; Domínguez-García, José Luis; De Schutter, Bart
"Owing to wake effects, the power production of each turbine in a wind farm is highly coupled to the operating conditions of the other turbines. Wind farm control strategies must take into account these couplings and produce individual power commands for each turbine. In this case, centralized control approaches might be prone to failures due to the high computational burden and communication dependency. To overcome this problem, this paper proposes a non-centralized scheme based on splitting the wind farm into almost uncoupled sets of turbines by solving a mixed-integer partitioning problem. In each set of turbines, a model predictive control strategy seeks to optimize the distribution of the power set-points among turbines such that the impact of the power losses due to the wake effect is reduced. Then, a supervisory controller coordinates the generation of each group to satisfy the power demanded by the grid operator. The effectiveness of the proposed control scheme in terms of reduction of computational costs and power regulation is confirmed by simulations for a wind farm of 42 turbines."
Modulation instability in waveguides with an arbitrary frequency-dependent nonlinear coefficient
(2020-05) Linale, N.; Bonetti, Juan I.; Sánchez, Alfredo D.; Hernández, Santiago M.; Fierens, Pablo Ignacio; Grosz, Diego
"In this Letter, we present, for the first time, to the best of our knowledge, the modulation instability (MI) gain spectrum of waveguides with an arbitrary frequency-dependent nonlinear coefficient ensuring strict energy and photon-number conservation of the parametric process. This is achieved by starting from a linear stability analysis of the recently introduced photon-conserving nonlinear Schrödinger equation. The derived MI gain is shown to predict some unique features, such as a nonzero gain extending beyond a zero-nonlinearity wavelength and a complex structure of the MI gain spectrum. Analytical results are shown to be in excellent agreement with numerical simulations."
A dual-stator winding induction generator based wind-turbine controlled via super-twisting sliding mode
(2019-11) Talpone, Juan I.; Puleston, Paul F.; Cendoya, Marcelo G.; Barrado-Rodrigo, José A.
"The dual-stator winding induction generator (DWIG) is a promising electrical machine for wind energy conversion systems, especially in the low/mid power range. Based on previous successful results utilising feed forward control, in this article, a super-twisting (ST) sliding mode improved control set-up is developed to maximise power extraction during low wind regimes. To accomplish this objective, via constant volts/hertz implementation, a ST controller was designed to command the DWIG control winding, such that the tip-speed ratio is robustly maintained at its optimal value. The proposed super-twisting control set-up was experimentally assessed to analyse its performance and to verify its efficiency in an actual generation test bench. The results showed a fast convergence to maximum power operation, avoiding chattering and offsets due to model uncertainties"
Diseño de un autopiloto para pequeños vehículos no tripulados
(2019-06) Garberoglio, Leonardo; Pose, Claudio D.; Mas, Ignacio; Giribet, Juan I.
"En este trabajo se presenta el diseño de un autopiloto para pequeños vehículos autónomos. El trabajo está enfocado principalmente en la arquitectura del sistema, pero se presentan también algunos detalles del firmware desarrollado para el autopiloto. En particular, el firmware incluye el paquete rosserial, que permite una conexión simple con ROS (Robot Operating System), resultando beneficioso para diversas aplicaciones. El desarrollo se valida experimentalmente en un vehículo aéreo no tripulado (UAV1) del tipo multi-rotor y en un vehículo acuático de superficie (ASV2). Estos vehículos han sido desarrollados por nuestro grupo, y en este trabajo puede encontrarse información sobre estos proyectos, lo cual puede ser de utilidad para los interesados en el desarrollo de UAV o ASV."
Hardware in the loop and software in the loop testing of the MOVE-II CubeSat
(2019-12) Kiesbye, Jonis; Messmann, David; Preisinger, Maximiliam; Reina Kiperman, Gonzalo Julián; Nagy, Daniel; Schummer, Florian; Mostad, Martin; Kale, Tejas; Langer, Martin
"This article reports the ongoing work on an environment for hardware-in-the-loop (HIL) and software-in-the-loop (SIL) tests of CubeSats and the benefits gained from using such an environment for low-cost satellite development. The satellite tested for these reported efforts was the MOVE-II CubeSat, developed at the Technical University of Munich since April 2015. The HIL environment has supported the development and verification of MOVE-II’s flight software and continues to aid the MOVE-II mission after its launch on 3 December 2018. The HIL environment allows the satellite to interact with a simulated space environment in real-time during on-ground tests. Simulated models are used to replace the satellite’s sensors and actuators, providing the interaction between the satellite and the HIL simulation. This approach allows for high hardware coverage and requires relatively low development effort and equipment cost compared to other simulation approaches. One key distinction from other simulation environments is the inclusion of the electrical domain of the satellite, which enables accurate power budget verification. The presented results include the verification of MOVE-II’s attitude determination and control algorithms, the verification of the power budget, and the training of the operator team with realistic simulated failures prior to launch. This report additionally presents how the simulation environment was used to analyze issues detected after launch and to verify the performance of new software developed to address the in-flight anomalies prior to software deployment."

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