Ingeniería Electrónica

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http://ri.itba.edu.ar/handle/123456789/42

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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."
LPV control of a magnetic bearing experiment
(2010-10) Ghersin, Alejandro S.; Smith, R. S.; Sánchez-Peña, Ricardo
"An LPV (Linear Parameter Varying) controller design example for a Magnetic Bearing System is presented. A linear model of the system including bending modes and imbalance is described. Simulations and experimental results show the usefulness of the LPV method with eigenvalue clustering constraints in spite of the limited rotation rate range. The results show that this method facilitates simulation and allows implementation. Conclusions are drawn on the limited range for the rotation rate the LPV controller allows for."
A novel design approach for switched LPV controllers
(2022-07-22) Bianchi, Fernando D.; Sánchez-Peña, Ricardo
"A novel design procedure for switched linear parameter-varying (LPV) controller is proposed. The new procedure, based on the Youla parameterisation ideas, decomposes the controller design into two steps. One focuses on ensuring global stability and the other on fulfilling the local performance specifications. This scheme allows the design of each local controller independently of each other, which may achieve higher performance without compromising the global stability and also simplifies the synthesis and the implementation of the local controllers. Any standard LPV synthesis procedure can be used to design these controllers. On the other hand, the stability during switching is ensured with convex constraints and no restrictions are imposed on the switching among controllers. The use of the proposed procedure is illustrated with an active magnetic bearing example."
Applied LPV Control with Full Block Multipliers and Regional Pole Placement
(2010-05) Sánchez-Peña, Ricardo; Ghersin, Alejandro S.
"A formulation of an LPV control problem with regional pole placement constraints is presented, which is suitable for the application of a Full Block S-Procedure. It is demonstrated that improved bounds can be obtained on the induced 𝐿2 norm of closed loop systems, while satisfying pole placement constraints. An application consisting in the 6 degrees of freedom (DOF) control of a space vehicle is developed as an example, with hardware in the loop (HIL) simulation. This shows that the method is appealing from the practical point of view, considering that the synthesized control law can be implemented satisfactorily in standard flight control systems. Conclusions with remarks towards the practical use of the method are presented as well."
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
Distributed data-driven UAV formation control via evolutionary games: experimental results
(2021-07) Barreiro-Gomez, Julian; Mas, Ignacio; Giribet, Juan I.; Moreno, Patricio; Ocampo-Martínez, Carlos; Sánchez-Peña, Ricardo; Quijano, Nicanor
"This work proposes a novel data-driven distributed formation-control approach based on multi-population evolutionary games, which is structured in a leader-follower scheme. The methodology considers a time-varying communication graph that describes how the multiple agents share information to each other. We present stability guarantees for configurations given by time-varying interaction networks, making the proposed method suitable for real-world problems where communication constraints change along the time. Additionally, the proposed formation controller allows for an agent to leave or enter the group without the need to modify the behaviors of other agents in the group. This game-theoretical approach is evaluated through numerical simulations and real outdoors experimental results using a fleet of aerial autonomous vehicles, showing the control performance."
Active noise hybrid time-varying control for motorcycle helmets
(2010-05) Castañé-Selga, Rosa; Sánchez-Peña, Ricardo
"Recent noise at work regulations in the EU (2003) have been established to prevent noise induced hearing loss (NIHL). This imposes better performance results to traditional feedback active noise control (ANC) in motorcycle helmets, which suffer from well known limitations. Here two new ideas are applied to this problem. First, an hybrid (feedforward/feedback) linear time invariant (LTI) controller is designed for a motorcycle helmet ANC, which improves the resulting attenuation. This is achieved by adding an extra pair of microphones which measure the external noise that is then used as the feedforward input signal. In addition and to increase even more the resulting performance, the air velocity is measured in real-time and used as the parameter which schedules a linear parameter varying (LPV) feedback (FB) controller. This is combined with the previous feedforward (FF) controller, resulting in a time-varying hybrid controller. Both hybrid, LTI and LPV controllers are designed using linear matrix inequality (LMI)-based optimization. Two experiments have been carried out to measure the relation between external noise spectra and velocity: a wind tunnel test and a freeway ride experience. The resulting controllers are tested in a simulation which uses actual data obtained from the freeway experiment. The resulting attenuations in this motivating study seem promising for future controller tests to be performed in real-time, with the adequate hardware."
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."
Industry engagement with control research: perspective and messages
(2020) Samad, Tariq; Bauer, Margret; Bortoff, Scott; Di Cairano, Stefano; Fagiano, Lorenzo; Odgaard, Peter Fogh; Rhinehart, R. Russell; Sánchez-Peña, Ricardo; Serbezov, Atanas; Ankersen, Finn; Goupil, Philippe; Grosman, Benyamin; Heertjes, Marcel; Mareels, Iven; Sosseh, Raye
"Despite the enormous benefit that has accrued to society from control technology and the continuedvitality of control science as a research field, there is broad consensus that the practitioners of control andthe academic research community are insufficiently engaged with each other. We explore this concernwith reference to the oft-cited theory/practice gap but also from an industry perspective. The core ofthis article is comprised of ten “messages,”intended primarily for researchers interested in the practicalimpact of their work, that we hope shed insight on the industry mindset. Results from surveys and otherdata are cited to underpin the points. Some educational synergies between industry and academia arealso noted. To highlight the continuing relevance of control science to industry, several recent examples ofsuccessful, deployed advanced control solutions are presented. The authors of this article are members ofthe IFAC Industry Committee, formally established in 2017 with objectives that include (per the updatedIFAC Constitution) “increasing industry participation in and impact from IFAC activities.”"
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."

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