See-and-avoid quadcopter using fuzzy control optimized by cross-entropy

In this work we present an optimized fuzzy visual servoing system for obstacle avoidance using an unmanned aerial vehicle. The cross-entropy theory is used to optimise the gains of our controllers. The optimization process was made using the ROS-Gazebo 3D simulation with purposeful extensions developed for our experiments. Visual servoing is achieved through an image processing front-end that uses the Camshift algorithm to detect and track objects in the scene. Experimental flight trials using a small quadrotor were performed to validate the parameters estimated from simulation. The integration of cross- entropy methods is a straightforward way to estimate optimal gains achieving excellent results when tested in real flights

La suspensión de obligaciones contractuales en sede cautelar

There has been a recent proliferation of decisions by Spanish courts and tribunals ordering interim measures suspending the effects of contractual obligations. These interim measures have often been handed down in legal proceedings in which a contractual party is seeking the total or partial ineffectiveness of a contract whose performance is singularly onerous for that party, putting its solvency at risk. For instance, the coronavirus health crisis and the financial crisis that began in 2008 recently led to a spike in the filing of lawsuits seeking contractual modification. These interim measures usually result in a finding by the court that a delay would be prejudicial by increasing the claimant’s risk of insolvency. In other words, a payment obligation challenged in the claim is suspended on the basis that, if the payment obligation were to be satisfied, the claimant would be forced into insolvency. In such cases there is some doubt as to whether the Spanish legal system allows an interim measure that not only brings forward the effects of a potentially favorable judgment, but also simultaneously implies the alteration of the status quo prior to the dispute. There is also debate as to whether the risk of the claimant entering into a situation of insolvency can be taken into consideration by a court when deciding whether to order an interim measure. In order to find a solution to this problem, it is necessary to analyze and systematize the difficult legal regulation of interim measures in Spanish procedural law, which involves some contentious issues. Despite the significant practical importance of this subject, it is striking how little attention jurists have paid to the potential alteration or suspension of contracts in interim measures. This paper aims to fill that gap and clarify whether or not the Spanish legal system allows the provisional modification of a prior to the court issuing a final judgment.Este trabajo ha obtenido ha sido finalista en el Premio «Estudios Financieros» 2021 en la modalidad de Derecho Civil y Mercantil. Han proliferado en los últimos tiempos resoluciones de nuestros juzgados y tribunales que conceden medidas cautelares por las que se suspenden los efectos de obligaciones contractuales. Estas medidas frecuentemente han sido resueltas en procedimientos judiciales, en los cuales una parte contractual promueve la ineficacia total o parcial de un contrato cuyas prestaciones le resultan singularmente gravosas, hasta el punto de comprometer su solvencia. Por ejemplo, la pandemia del coronavirus o la crisis financiera iniciada en 2008 han dado lugar recientemente al ejercicio de este tipo de acciones que tratan de modificar un contrato. Habitualmente, esas resoluciones concluyen que concurre peligro en la demora debido a un riesgo de insolvencia del demandante. Es decir, se suspende una obligación de pago cuestionada en la demanda principal sobre la base de que, en caso de tener que satisfacer esa obligación, el actor se vería abocado a una situación de insolvencia. En tales casos se plantea la duda sobre la admisibilidad o no en nuestro ordenamiento de una medida cautelar que no solo adelanta los efectos de una posible sentencia estimatoria, sino que también comporta una alteración del estado de cosas previo al conflicto. También existe controversia sobre si el riesgo de que el demandante devenga en una situación concursal puede ser considerada a la hora de adoptar la medida. Para dar respuesta a esta problemática será necesario analizar y sistematizar la difícil regulación legal de las medidas cautelares en el ordenamiento procesal español, que presenta algunas cuestiones oscuras. Pese a la notable importancia práctica de la cuestión, resulta llamativa la escasa atención que la doctrina ha dedicado a la posible alteración o suspensión de los contratos en sede cautelar. El presente trabajo se propone llenar ese vacío y aclarar si nuestro ordenamiento permite o no la modificación provisional de la relación contractual en tanto no se dicte sentencia sobre el fondo

AR drone identification and navigation control at CVG-UPM

This article presents the proposal of the Computer Vision Group to the first phase of the international competition “Concurso de Ingeniería de Control 2012, Control Aut ́onomo del seguimiento de trayectorias de un vehículo cuatrirrotor”. This phase consists mainly of two parts: identifying a model and designing a trajectory controller for the AR Drone quadrotor. For the identification task, two models are proposed: a simplified model that captures only the main dynamics of the quadrotor, and a second model based on the physical laws underlying the AR Drone behavior. The trajectory controller design is based on the simplified model, whereas the physical model is used to tune the controller to attain a certain level of robust stability to model uncertainties. The controller design is simplified by the hypothesis that accurate positions sensors will be available to implement a feedback controller

A General Purpose Configurable Navigation Controller for Micro Aerial Multirotor Vehicles

In this paper, we consider the problem of autonomous navigation of multirotor platforms in GPS-denied environments. The focus of this work is on safe navigation based on unperfect odometry measurements, such as on-board optical flow measurements. The multirotor platform is modeled as a flying object with specific kinematic constraints that must be taken into account in order to obtain successful results. A navigation controller is proposed featuring a set of configurable parameters that allow, for instance, to have a configuration setup for fast trajectory following, and another to soften the control laws and make the vehicle navigation more precise and slow whenever necessary. The proposed controller has been successfully implemented in two different multirotor platforms with similar sensoring capabilities showing the openness and tolerance of the approach. This research is focused around the Computer Vision Group's objective of applying multirotor vehicles to civilian service applications. The presented work was implemented to compete in the International Micro Air Vehicle Conference and Flight Competition IMAV 2012, gaining two awards: the Special Award on "Best Automatic Performance - IMAV 2012" and the second overall prize in the participating category "Indoor Flight Dynamics - Rotary Wing MAV". Most of the code related to the present work is available as two open-source projects hosted in GitHub

Análisis del efecto del ejercicio físico en la homogeneidad espacial del espectro de la señal de fibrilación ventricular

El presente trabajo estudia las modificaciones intrínsecas que el ejercicio físico produce en la respuesta cardíaca durante fibrilación ventricular (FV), tanto en condiciones de perfusión estable como cuando se produce isquemia en una zona del miocardio. Se estudiarán dichas modificaciones comparándolas con las producidas por el efecto de un fármaco (Glibenclamida) y con un grupo control. El análisis se realizará desde el punto de vista del dominio frecuencial, estudiando la homogeneidad espacial de la frecuencia dominante (ROIsaFD) y de la energía normalizada (ROIsaEN), en registros de cartografía cardíaca unipolar de corazón aislado de conejo. Se utilizarán tres grupos de conejos: control (GC: sin entrenamiento, N=18), entrenados (GE: N=9) y fármaco (GF: sin entrenamiento, con tratamiento, N=15). Se realizarán comparaciones intergrupos, teniendo en cuenta el hecho de que se realizan medidas repetidas en el tiempo, y se harán comparaciones intragrupos para estudiar el efecto del tiempo. Los resultados obtenidos sugieren que los efectos intrínsecos producidos por ejercicio físico sobre la homogeneidad espacial de la respuesta espectral de la FV son similares a los producidos por el tratamiento con Glibenclamida, especialmente cuando se tienen zonas isquémicas

Análisis de regularidad en fibrilación ventricular: aplicación a registros de mapeado cardíaco

Las técnicas utilizadas en el análisis de la señal de fibrilación ventricular (FV), obtenida mediante sistemas de mapeado utilizando matrices de electrodos, extraen información del proceso a partir de parámetros calculados principalmente en el dominio del tiempo o de la frecuencia. El presente trabajo plantea la aplicación del índice de regularidad (IR), propuesto inicialmente para caracterizar la fibrilación auricular humana, a la señal de FV en un modelo experimental de corazón animal. Los resultados obtenidos muestran que el IR permite extraer información de los mapas de FV no disponible de forma directa cuando se estudian mediante los métodos clásicos en el tiempo o la frecuencia, cuantificando el grado de modificación en la morfología de las ondas de activación durante la FV

Modifications on regularity and spectrum of ventricular fibrillation signal induced by physical training

The objective of this work is to study the modifications on cardiac response during ventricular fibrillation (VF) induced by physical training. The analysis was performed in the frequency domain of VF, and the regularity of the signal was also considered. Two sets of records were acquired: control (G1: without physical training, N=10), and trained (G2, N=9). Cardiac registers were obtained using a 240-electrodes matrix located on left ventricle of isolated rabbit heart. A Langendorff system was used to maintain the heart perfusion. VF was induced by increased frequencies. To analyze the time course of VF, records were processed in 4-second segments. For every segment and channel, Welch periodogram with Hanning window, two non-overlapped sections and zero padding, was computed. Parameters considered in frequency domain are: dominant frequency (DF) and normalized energy (NE: spectral energy in the window DF±1Hz, normalized by spectral energy in 5-35Hz band). For every segment and channel, a regularity analysis of VF was performed, obtaining the regularity index (RI), which is a measure of similarity among local activation waves present in every channel. Mean values for the parameters (DF, NE and RI) of the whole set of electrodes were computed for every segment. Obtained results show that DF is lower for trained rabbits (G1: 18.234±1, 241Hz; G2: 14.370±0, 866Hz; p<0.001). NE is greater for this group (G1: 0.140±0.006; G2: 0.263±0.017; p<0.001), suggesting a greater spectral concentration around DF. Finally, a greater regularity has been observed in the fibrillation signal for trained group (IR, G1: 0.756±0.026; G2: 0.834±0.014; p<0.001). As a summary, the results suggest that both spectral characteristics and regularity of VF signal are clearly different for G1 and G2 groups. The trained group (G2) shows greater regularity, lower DF and spectral dispersion. These factors should be interpreted as a more stable cardiac response to V

Application of machine learning techniques to analyse the effects of physical exercise in ventricular fibrillation

This work presents the application of machine learning techniques to analyze the influence of physical exercise in the heart's physiological properties, during ventricular fibrillation. With that purpose, different kinds of classifiers (linear and neural models) were used to classify between trained and sedentary rabbit hearts. These classifiers were used to perform knowledge extraction through a wrapper feature selection algorithm. The obtained results showed the higher performance of the neural models compared to the linear classifier (higher performance measures and higher dimensionality reduction). The most relevant features to describe the benefits of physical exercise are those related to myocardial heterogeneity, mean activation rate and activation complexity

Analysis of spatial and temporal evolution of regularity maps during ventricular fibrillation

The analysis of cardiac mapping allows investigating the structure of ventricular fibrillation (VF). This work analyzes regions of interest (ROI) on cardiac maps obtained from the regularity analysis of VF records, providing information about signal regularity at each time instant and its spatial distribution. Cardiac registers were obtained using a 240- electrodes matrix located on left ventricle of isolated rabbit heart. A Langendorff system was used to maintain the heart perfusion. VF was induced by increased frequencies. Two groups of records were considered: control (G1: without physical training, N=10), and trained (G2, N=9). Records were processed in consecutive 4-second segments. Regularity index (RI) was obtained for every segment and channel. RI is a measure of similarity degree among local activation waves for every channel. A map with the RI value of each channel was computed for the 82 register segments. To analyze the spatial distribution of RI, a threshold value was determined experimentally and applied to the map in order to obtain the ROI. Two parameters were calculated: ROI spatial number (ROIsn, a measure of spatial fragmentation), and ROI spatial area (ROIsa, the percentage of area map occupied by ROI). In case of the time course of ROI, two additional parameters were computed: the number of electrodes which value had changed respect to the threshold in two consecutive maps (ROIen, which is related with the change size), and the cumulative absolute differences of RI values for the electrodes which are changed (ROIed). Obtained results for spatial analysis show that the number of ROI is lower for trained rabbits (ROIsn; G1: 4.465±1.120; G2: 2.,227±0.623; p<0.001), but ROI spatial area is greater than the control group (ROIsa; G1: 76.235±5.355%; G2: 88.163±2.885%; p<0.001). Time-course analysis shows that more electrodes change between consecutive maps in the control group (ROIen, G1: 22.455±6.702; G2: 13.877±2.485; p<0.001). No significant differences were found for ROIed (G1: 18.509±6.932; G2: 18.619±4.196; n.s.). To conclude, ROI analysis on RI maps applied to trained and no trained rabbits groups shows that VF cardiac response is more irregular and spatially fragmented in no trained group. In addition, regularity maps are more stable with time in trained group

Relación entre el espectro y la regularidad en la señal de fibrilación ventricular modificada por el ejercicio físico

El presente trabajo estudia las modificaciones intrínsecas que el ejercicio físico produce en la respuesta cardíaca durante la FV. Se han calculado dos parámetros relacionados con el espectro de la señal (FD: frecuencia dominante, y EN: energía normalizada), y otro relacionado con la regularidad de las OAL (IR: índice de regularidad), Se ha realizado un análisis de correlación entre los tres parámetros para valorar su grado de complementariedad. Se consideraron dos grupos de conejos: control (G1: sin entrenamiento, N=10) y entrenados (G2, N=9). Se utilizó un electrodo matricial de 240 canales localizado en ventrículo izquierdo de corazón aislado de conejo perfundido mediante un sistema de Langendorff. La FV se indujo por estimulación a frecuencias crecientes. Los resultados muestran que el grupo entrenado presenta una mayor regularidad de la señal (IR: G1: 0,757+-0,091; G2: 0,845+-0,084; p<0.001), así como menor FD (G1: 18.23±2.96Hz; G2: 14.13+-1.73Hz; p<0.001) y dispersión espectral (EN: G1: 0,138+-0.105; G2: 0,293+-0,176; p<0.001). El análisis de las relaciones entre parámetros muestra correlaciones significativas entre los parámetros para todos los casos excepto para IR y FD en G2, por lo que estos parámetros proporcionan información complementaria, ya que analizan aspectos diferentes de la señal como la morfología de las ondas de activación y su frecuencia. La existencia de correlación entre ambas para G1 puede ser debida a otras causas, tales como las modificaciones en ambos factores inducidas por la presencia de reentradas o colisiones entre frentes de activación.. Como conclusión, los resultados obtenidos sugieren que el entrenamiento físico produce una respuesta cardíaca más estable ante FV, debida a modificaciones intrínsecas en las características electrofisiológicas cardíacas