A Mission Coordinator Approach for a Fleet of UAVs in Urban Scenarios

Abstract The use of Unmanned Aerial Vehicles (UAVs) is now common, but although they have been for various applications, there are still a lot of challenges that need to be overcome. One key issue is related to standardizing the use of these vehicles in urban environments and guaranteeing a minimum risk level for the population. To rise to these challenges, autonomous strategies that optimize and coordinate vehicles in cooperative missions and avoid human operators should be developed. The novelty of this paper is the development of an autonomous urban mission coordinator, which is responsible for the high-level logistics of a fleet of heterogeneous vehicles. A multi-variable weighted algorithm based on a tree optimization method is also proposed

The Borea project: a quadrotor uav cradle-to-grave design for space gnc prototyping and testing

Unmanned Aerial Vehicles (UAVs) and, more specifically, n-copters have come to prominence in the last decade due to their several applications. Also, in the automatic control research community UAVs have drawn great attention, since their non-linear and under-actuated nature making them suitable for testing a wide range of control architectures and algorithms. In this paper, prominent theoretical aspects, simulations, and experimental results of the Borea project are presented. The Borea project aims at testing space guidance, navigation, and control (GNC) algorithms leveraging a simplified, rapidly prototypable, low-cost, and easy-to-test quadrotor platform. More precisely, one of the main project objectives consists in testing Moon and Mars planetary landing algorithms, thanks to the similitude, in the command authority and the landing approach, between n-copters and spacecraft; during the propulsive landing phase. Indeed, both n-copters and spacecraft can provide a thrust vector characterized by constant direction and adjustable magnitude. This similitude approach makes it possible to anticipate issues and avoid failures such as those that occurred in the Schiaparelli Mars Lander. To this aim, the complete control unit design, and the UAV plant electro-mechanical prototyping were addressed; so far. Specifically, the control unit was designed within the framework of the Embedded Model Control (EMC) methodology. The EMC design, based on an internal model, also includes the uncertainties as disturbances to be estimated and actively rejected. The Borea UAV has been endowed with a control system leveraging a wide range of automatic control concepts, ranging from modelling, identification, and linear and non-linear control laws, to deal with its position, velocity, and attitude regulation. To sum up, all these results were achieved by means of a properly structured cradle-to-grave design process which, starting from the simultaneous plant modelling and prototyping, ended up with a complete flight tests campaign. Most notably, the testing process involved intensive numerical simulations as well as multi-stage hardware/plant tests and models validation. From the control perspective, the several developed controllers were tuned and tested, via proper simulations and on-purpose flight tests, aiming at validating, from time to time, specific functionalities and control performances. Finally, some results coming from high-fidelity simulations, the hardware and model testing, and in-flight operations are provided to underline the most relevant aspects of the Borea plant and the control unit performance

Diseño de un controlador robusto basado en Lmis aplicado en un Quadrotor

Introduction: An unmanned aircraft UAV or UAVS for its acronym in English is one capable of performing a flight without the need for a pilot on board. The control techniques applied in unmanned aircraft systems are used to improve the performance and stability of these systems. Several control techniques have been created to automate systems, aiming to improve the performance of these looking for optimal performance conditions. Quadrotors are a type of unmanned aerial vehicle that is currently used due to its ease of vertical take-off and landing (VTOL), it is an ideal system to apply control laws because of its non-linearity and its unstable behavior in the face of external disturbances, usually environmental variables. Objective: Establish the advantages of the implementation of a robust control based on linear matrix inequalities, compared to a state feedback controller implemented in a quadrotor type unmanned aerial vehicle. Method: Two linear control strategies were designed and implemented: control by location of poles and zeros, and control based on linear matrix LMI inequalities; therefore, in this work a linear model of the quadrotor represented in state variables was used. Results:  The controllers are stable against external disturbances and disturbances caused by the environment. For the Pitch and Roll angles, the set point was adjusted to 0 degrees, and for the yaw angle, the set point was adjusted to 100 degrees. This paper shows the performance of the control strategy based on LMIs, short response times and maintains an equilibrium point between -2 and 2 degrees on each axis, allowing the quadrotor to stabilize at each angle of rotation. Conclusions: The controller based on LMIs has multiple advantages compared to the state feedback control strategy, since it allows the inclusion of several controller design criteria such as: the control input, the poles location, the definition of the infinite H norm, uncertainties, and disturbances. In addition, the LMI-based controller is presented as a solution to be implemented in a real system as it significantly improved the maximum overshoot, the response to external disturbances, the response time and quadrotor stabilization in the tests carried out.Una aeronave no tripulada UAV o UAVS por sus siglas en inglés es aquella capaz de realizar un vuelo sin necesidad de tener un piloto a bordo. Las técnicas de control aplicadas en sistemas de aeronaves no tripuladas son utilizadas para mejorar el desempeño y estabilidad de estos sistemas. Varias técnicas de control se han creado con el objetivo de automatizar este tipo de sistemas, teniendo como objetivo final mejorar el rendimiento buscando las condiciones óptimas de desempeño. Los quadrotores son un tipo de vehículo aéreo no tripulado que actualmente es utilizado debido a su facilidad de despegue y aterrizaje vertical (VTOL), es un sistema ideal para aplicar estrategias de control debido a su modelo matemático no linealidad y su comportamiento inestable ante perturbaciones externas, que en su mayoría son variables ambientales. Objetivo: Establecer las ventajas que presenta la implementación de un control robusto basado en desigualdades lineales matriciales, frente a un controlador por realimentación de estados implementado en un vehículo aéreo no tripulado tipo quadrotor. Metodología: En este trabajo se diseñaron e implementaron dos estrategias de control lineal: control por realimentación de estados, y control basado en desigualdades de matriz lineal LMI, por lo tanto, en este trabajo utilizó un modelo linealizado del quadrotor representado en variables de estado.  Resultados: Los controladores son estables frente a perturbaciones externas y perturbaciones dadas por el ambiente. Para el caso de los ángulos Pitch y Roll, el set point fue ajustado en 0 grados, y para el caso del ángulo yaw, el set point fue ajustado en 100 grados. En este trabajo se muestra el desempeño de la estrategia de control basada en LMIs, tiempos de respuesta cortos y mantiene un punto de equilibrio entre -2 y 2 grados de cada eje, permitiendo estabilizar el quadrotor en cada ángulo de rotación. Conclusiones: El controlador basado en LMIs presenta múltiples ventajas frente a la estrategia de control por realimentación de estados, ya que permite incluir varios criterios de diseño de controladores como lo son: la entrada de control, la ubicación de polos, la definición de la norma H infinito, incertidumbres y perturbaciones. Además, el controlador basado en LMIs se presenta como una solución para ser implantada en un sistema real ya que mejoró significativamente el sobre pico máximo, la respuesta ante perturbaciones externas, el tiempo de respuesta y estabilización de quadrotor en las pruebas realizadas.  &nbsp