460 research outputs found
Energy-based Modeling and Control of Interactive Aerial Robots:A Geometric Port-Hamiltonian Approach
Aerial Manipulation: A Literature Review
Aerial manipulation aims at combining the versatil- ity and the agility of some aerial platforms with the manipulation capabilities of robotic arms. This letter tries to collect the results reached by the research community so far within the field of aerial manipulation, especially from the technological and control point of view. A brief literature review of general aerial robotics and space manipulation is carried out as well
A distributed optimization framework for localization and formation control: applications to vision-based measurements
Multiagent systems have been a major area of research for the last 15 years. This interest has been motivated by tasks that can be executed more rapidly in a collaborative manner or that are nearly impossible to carry out otherwise. To be effective, the agents need to have the notion of a common goal shared by the entire network (for instance, a desired formation) and individual control laws to realize the goal. The common goal is typically centralized, in the sense that it involves the state of all the agents at the same time. On the other hand, it is often desirable to have individual control laws that are distributed, in the sense that the desired action of an agent depends only on the measurements and states available at the node and at a small number of neighbors. This is an attractive quality because it implies an overall system that is modular and intrinsically more robust to communication delays and node failures
Nonlinear Control Strategies for Outdoor Aerial Manipulators
In this thesis, the design, validation and implementation of nonlinear control strategies for aerial manipulators
{i.e. aerial robots equipped with manipulators{ is studied, with special emphasis on the internal coupling of the
system and its resilience against external disturbances. For the rst, di erent decentralised control strategies
{i.e. using di erent control typologies for each one of the subsystems{ that indirectly take into account this
coupling have been analysed. As a result, a nonlinear strategy composed of two controllers is proposed. A higher
priority is given to the manipulation accuracy, relaxing the platform tracking, and hence obtaining a solution
improving the manipulation capabilities with the surrounding environment. To validate these results, thorough
stability and robustness analyses are provided, both theoretically and in simulation.
On the other hand, a signi cant e ort has been devoted to improving the response and applicability of
robot manipulators used in
ight via control. In particular, the design of controllers for lightweight
exible
manipulators {that reduce the consequences of incidents involving unforeseen contacts{ is analysed. Although
their inherent nature perfectly ts for aerial manipulation applications, the added
exibility produces unwanted
behaviours, such as second-order modes and uncertainties. To cope with them, an adaptable position nonlinear
control strategy is proposed. To validate this contribution, the stability of the approach is studied in theory
and its capabilities are proven in several experimental scenarios. In these, the robustness of the solution against
unforeseen impacts and contact with uncharacterised interfaces is demonstrated.
Subsequently, this strategy has been enriched with {multiaxis{ force control capabilities thanks to the
inclusion of an outer control loop modifying the manipulator reference. Accordingly, this additional applicationfocused
capability is added to the controlled system without loosing the modulated response of the inner-loop
position strategy. It is also worth noting that, thanks to the cascade-like nature of the modi cation, the transition
between position and force control modes is inherently smooth and automatic. The stability of this expanded
strategy has been theoretically analysed and the results validated in a set of experimental scenarios.
To validate the rst nonlinear approach with realistic outdoor simulations before its implementation, a
computational
uid dynamics analysis has been performed to obtain an explicit model of the aerodynamic
forces and torques applied to the blunt-body of the aerial platform in
ight. The results of this study have been
compared to the most common alternative nowadays, being highlighted that the proposed model signi cantly
surpasses this option in terms of accuracy. Moreover, it is worth underscoring that this characterisation could
be also employed in the future to develop control solutions with enhanced rejection capabilities against wind
conditions.
Finally, as the focus of this thesis is on the use of novel control strategies on real aerial manipulation outdoors
to improve their accuracy while performing complex tasks, a modular autopilot solution to be able to implement
them has been also developed. This general-purpose autopilot allows the implementation of new algorithms,
and facilitates their theory-to-experimentation transition. Taking into account this perspective, the proposed
tool employs the simple and widely-known MAS interface and the highly reliable PX4 autopilot as backup, thus
providing a redundant approach to handle unexpected incidents in
ight.En esta tesis se ha estudiado el diseño, validación e implementación de estrategias de control
no lineales para robots manipuladores aéreos –esto es, robots aéreos equipados con un sistema
de manipulación robótica–, dándose especial énfasis a las interacciones internas del sistema y a
su resiliencia frente a efectos externos. Para lo primero, se han analizado diferentes estrategias
de control descentralizado –es decir, que usan tipologías de control diferentes para cada uno de
los subsistemas–, pero que tienen indirectamente en consideración la interacción entre manipulación
y vuelo. Como resultado de esta línea, se propone una estretegia de control conformada
por dos controladores. Estos se coordinan de tal forma que se le da prioridad a la manipulación
sobre el seguimiento de posiciones del vehículo, produciéndose un sistema de control que mejora
la precisión de las interacciones entre el sistema manipulador y el entorno. Para validar estos resultados,
se ha analizado su estabilidad y robustez tanto teóricamente como mediante simulaciones
numéricas.
Por otro lado, se ha buscado mejorar la respuesta y aplicabilidad de los manipuladores que se
usan en vuelo mediante su control. Dentro de esta tendencia, la tesis se ha centrado en el diseño
de controladores para manipuladores ligeros flexibles, ya que estos permiten reducir el peso del
sistema completo y reducen el riesgo de incidentes debidos a contactos inesperados. Sin embargo,
la flexibilidad de estos produce comportamientos indeseados durante la operación, como la aparición
de modos de segundo orden y cierta incentidumbre en su comportamiento. Para reducir su
impacto en la precisión de las tareas de manipulación, se ha desarrollado un controlador no lineal
adaptable. Para validar estos resultados, se ha analizado la estabilidad del sistema teóricamente y se
han desarrollado una serie de experimentos. En ellos, se ha comprobado su robustez ante impactos
inesperados y contactos con elementos no caracterizados.
Posteriormente, esta estrategia para manipuladores flexibles ha sido ampliada al añadir un bucle
externo que posibilita el control en fuerzas en varias direcciones. Esto permite, mediante un único
controlador, mantener la suave respuesta de la estrategia. Además cabe destacar que, al contar esta
estrategia con un diseño en cascade, la transición entre los segmentos de desplazamiento del brazo
y de aplicación de fuerzas es fluida y automática. La estabilidad de esta estrategia ampliada ha sido
analizada teóricamente y los resultados han sido validados experimentalmente.
Para validar la primera estrategia mediante simulaciones que representen fielmente las condiciones
en exteriores antes de su implementación, ha sido necesario realizar un estudio mediante
mecánica de fluidos computacional para obtener un modelo explícito de las fuerzas y momentos
aerodinámicos a los que se efrenta la plataforma en vuelo. Los resultados de este estudio han
sido comparados con la alternativa más empleada actualmente, mostrándose que los avances del
método propuesto son sustanciales. Asimismo, es importante destacar que esta caracterización podría
también usarse en el futuro para desarrollar controladores con una respuesta mejorada ante
perturbaciones aerodinámicas, como en el caso de volar con viento. Finalmente, al ser esta una tesis centrada en las estrategias de control novedosas en sistemas
reales para la mejora de su rendimiento en misiones complejas, se ha desarrollado un autopiloto
modular fácilmente modificable para implementarlas. Este permite validar experimentalmente
nuevos algoritmos y facilita la transición entre teoría y práctica. Para ello, esta herramienta se
basa en una interfaz sencilla ampliamente conocida por los investigadores de robótica, Simulink®,
y cuenta con un autopiloto de respaldo, PX4, para enfrentarse a los incidentes inesperados que
pudieran surgir en vuelo
Grasping, Perching, And Visual Servoing For Micro Aerial Vehicles
Micro Aerial Vehicles (MAVs) have seen a dramatic growth in the consumer market because of their ability to provide new vantage points for aerial photography and videography. However, there is little consideration for physical interaction with the environment surrounding them. Onboard manipulators are absent, and onboard perception, if existent, is used to avoid obstacles and maintain a minimum distance from them. There are many applications, however, which would benefit greatly from aerial manipulation or flight in close proximity to structures. This work is focused on facilitating these types of close interactions between quadrotors and surrounding objects. We first explore high-speed grasping, enabling a quadrotor to quickly grasp an object while moving at a high relative velocity. Next, we discuss planning and control strategies, empowering a quadrotor to perch on vertical surfaces using a downward-facing gripper. Then, we demonstrate that such interactions can be achieved using only onboard sensors by incorporating vision-based control and vision-based planning. In particular, we show how a quadrotor can use a single camera and an Inertial Measurement Unit (IMU) to perch on a cylinder. Finally, we generalize our approach to consider objects in motion, and we present relative pose estimation and planning, enabling tracking of a moving sphere using only an onboard camera and IMU
Haptic Tele-operation of Wheeled Mobile Robot and Unmanned Aerial Vehicle over the Internet
Teleoperation of ground/aerial vehicle extends operator\u27s ability (e.g. expertise, strength, mobility) into the remote environment, and haptic feedback enhances the human operator\u27s perception of the slave environment. In my thesis, two cases are studied: wheeled mobile robot (MWR) haptic tele-driving over the Internet and unmanned aerial vehicle (UAV) haptic teleoperation over the Internet. We propose novel control frameworks for both dynamic WMR and kinematic WMR in various tele-driving modes, and for a mixed UAV with translational dynamics and attitude kinematics. The recently proposed passive set-position modulation (PSPM) framework is extended to guarantee the passivity and/or stability of the closed-loop system with time-varying/packet-loss in the communication; and proved performance in steady state is shown by theoretical measurements.For UAV teleoperation, we also derive a backstepping trajectory tracking control with robustness analysis. Experimental results for dynamic/kinematic WMR and an indoor quadrotor-type UAV are presented to show the efficacy of the proposed control framework
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