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This work presents the development of a fault detection and identification module for multirotor unmanned aerial vehicles (UAVs), capable of detecting a total failure in any of its rotors. The solution is based on a supervised learning approach, for which random forest and support vector machine classifiers have been trained using simulated data, and proved to be feasible to implement in real time. To validate these models, experimental proof will be shown of a classifier running in real time onboard a particular fault tolerant hexarotor design, showing the fastest detection times in this vehicle to date.

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 article, 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 article 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.

Lately, a novel multirotor aerial vehicle capable of handling single rotor failures was presented. When a rotor fails, physically reconfiguring one of the remaining rotors of a hexarotor allows to compensate for maneuverability limitations. In this work, experimental results show the performance of the vehicle in a trajectory-following task in both nominal and fault conditions.

This work carries out an analysis on fault tolerance in multirotor vehicles, particularly for an hexarotor one, where such feature is achieved by shifting the center of mass in case of a motor failure. It will be shown that, for an hexarotor vehicle, for each of the possible motor failures, there exists an optimal fixed position for the center of mass, in order to keep independent control of four degrees of freedom, and to obtain the best maneuverability. The performance of this solution will be compared with a previous design based on motor reconfiguration in case of a motor failure.

In this work, the design of an autopilot for small unmanned vehicles is presented. It is focused mainly on the system’s architecture, while presenting some important remarks of the developed firmware. In particular, the firmware uses rosserial, a package that allows a simple connection with ROS (Robot Operating System), which is useful for a number of applications.The work is validated experimentally on an multirotor-type unmanned aerial vehicle (UAV), and on an autonomous surface vehicle (ASV). These vehicles have been developed by our group, and this work provides information about such projects, which may be useful for those interested in the development of this kind of vehicles., 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 (UAV 1) del tipo multi-rotor y en un vehículo acuático de superficie (ASV 2). 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.

A simulation model and an experimental characterization of energy saving glazing transparent to mobile communication frequency up to 40 GHz is presented. A previous study showed that laser structured energy efficient windows with a frequency selective surface greatly reduces the microwave attenuation for frequencies below 5 GHz, while preserving the thermal insulation properties of the window. In this study, the focus is laid upon higher frequency range (26–40 GHz), considering the rapid evolution of the carrier frequencies. Several energy efficient windows were built and laser scribed with a cell periodicity down to 0.5 mm. A computational model based on electric equivalent circuit behavior and transfer matrix representation is shown, and compared to a real set of measurements taken from the manufactured glazing. The simulated data strongly fit the measurements taken for five different windows, and, additionally, it allows to infer parameters of a real double-glazing that may be difficult to measure directly. To the best of our knowledge, this is the first time energy efficient windows are produced with these characteristics, measured and simulated at high frequency range.

Tilted rotors in multirotor vehicles have shown to be useful for different practical reasons. For instance, increasing yaw maneuverability or enabling full position and attitude control of hexarotor vehicles. It has also been proven that a hexagon-shaped multirotor is capable of complete attitude and altitude control under failures of one of its rotors. However, when a rotor fails, the torque that can be reached in the worst- case direction decreases considerably.This work proposes to actively change the tilt angle of the rotors when a failure occurs. This rotor reconfiguration increases the maximum torque that can be achieved in the most stressful direction, reducing maneuverability limitations. Experimental validations are shown, where the proposed reconfigurable tilted rotor is used in order to control a hexarotor vehicle when a failure appears mid-flight. The impact of the delay in the reconfiguration when a failure occurs is also addressed.

Several works have addressed the issue of obtaining a six degree of freedom (6DOF) capable multirotor. However, the capability of keeping full control in the case of a total failure in one of the rotors has not yet been analyzed. In this work, it is proven that eight is the minimum number of rotors necessary to achive 6DOF control of a multirotor, in the case of a total failure in one of them. Also, an octorotor configuration with 6DOF control capabilities in a failure situation is proposed and analyzed through numerical simulations, comparing its flight performance in a nominal and a failure case.

In this work we present a new flight controller board based on a Cortex-M7 microcontroller. The design is based on previous work done in our laboratory, this being the third version of the board. The main goal of this update is to achieve a very small and lightweight flight controller, but with a high computational power that can be used in a wide range of autonomous vehicles. In order to show its performance, an example for stabilizing a quadrotor UAV is presented and analyzed.

We present an approach based on machine learning for detecting total motor failure in a tilted-rotor hexacopter. We generate large flight datasets using a Simulink model based on a 6-DoF block and position and attitude PID controllers; these datasets are used to train and validate a random forest classifier that is able to detect if a motor has failed, and identify which one. The algorithm uses as inputs the attitude of the vehicle and the signals commanded to the motors, and outputs a flag per motor that indicates its healthy or faulty state. The classifier achieves a good performance, resulting in a detection of the fault in less than 100mS after it has occurred, with a high rejection of false positives, less than one false positive per hour of flight.

Recently, it was shown that an hexagon-shaped hexa-rotor micro aerial vehicle with unidirectionally spinning tilted rotors is capable of fault tolerant attitude and altitude control. This result has been theoretically proven and validated by simulations. However, experimental results have never been reported yet. In this work experimental results are presented, and a comparison between a tilted-rotor hexacopter with one in a standard rotor configuration is carried out.

Recently, it was shown that an hexagon shaped hexarotor vehicle with tilted rotors, is capable of fault tolerant attitude and altitude control. In this work, we propose a strategy to select the signals commanded to each rotor in order to achieve a desired torque and vertical force. The proposed strategy is optimal in the sense that minimizes the maximum force exerted by the rotors. A comparison with the commonly used strategy based upon the Moore-Penrose pseudoinverse is carried out. It is shown that, with the optimal strategy proposed here, maneuverability is improved, because the new method takes into account the actuators constraints. Although the optimal strategy is computationally more demanding than the classical method, the additional computational burden is not significant when both strategies are compared in a real application. To show this, both algorithms were programmed in an autopilot based on an ARM Cortex M3 microcontroller, and the experimental results are presented.

The aim of this work is to present a navigation system for GPS denied environments. The system fuses measurements provided by an arrangement of ultrasonic range sensors with inertial measurements and a magnetometer. The core of the navigation computer are two microprocessors, an ARM Cortex M3 processor for low-level tasks, such as sensor acquisition and control, and an ARM Cortex A8 for computationally demanding tasks, as the fusion filter to compute navigation solutions. A brief description of the navigation computer is given, also the navigation algorithm is presented and validated through experimental results.