http://www.nt.ntnu.no/users/skoge/prost/proceedings/ifac11-proceedings/data/html/papers/2327.pdf

The Navigation and Control technology inside the AR.Drone micro UAV

Unmanned aerial vehicle (UAV) networks are playing an important role in various areas due to their agility and versatility, which have attracted significant attentions from both the academia and industry in recent years. As an integration of embedded systems with communication devices, computation capabilities and control modules, the UAV network could build a closed loop from data perceiving, information exchanging, decision making to the final execution, which tightly integrates cyber processes into physical devices. Therefore, the UAV network could be considered as a cyber physical system (CPS). Revealing coupling effects among the three interacted CPS components, i.e., communication, computation and control, is envisioned as the key to properly utilize all available resources and hence improve the performance of the UAV network. In this paper, we present a comprehensive survey on UAV networks from a CPS perspective. Firstly, we review the basics and advances of the three CPS components in UAV networks. Then we look inside to investigate how these components contribute to the system performance by classifying UAV networks into three hierarchies, i.e., cell level, system level, and system of system level. Furthermore, the coupling effects among these CPS components are explicitly illustrated, which could be enlightening to deal with the challenges in each individual aspect. New research directions and open issues are discussed at the end of this survey. With this intensive literature review, we intend to provide a novel insight into the state of the art in UAV networks.

Survey on Unmanned Aerial Vehicle Networks: A Cyber Physical System Perspective

An unmanned quadrotor presents excellent mobility to fly freely in complex environments, which makes it an ideal choice for aerial transferring tasks. During the transferring process, it is very challenging to eliminate the swing, since there is no direct control on the payload. The quadrotor transportation system presents the great challenge of the cascaded underactuated–underactuated property, which makes it extremely difficult to simultaneously implement accurate quadrotor positioning and efficient payload swing suppression. In this paper, a nonlinear hierarchical control scheme is proposed for a quadrotor transportation system, which takes full advantage of the cascade property of the system and separates the controller design for the inner loop and the outer loop, respectively, to facilitate the design procedure. More specifically, for the outer loop subsystem, based on the proposed energy storage function, a virtual control vector is designed, which introduces a saturation function to make the desired attitude free of any singularities. For the inner loop, a coordinate-free geometric attitude tracking controller is designed on the Lie group to drive the quadrotor to its desired attitude. It is shown theoretically by Lyapunov techniques and LaSalle's invariance theorem that the equilibrium point of the overall system is asymptotically stable. As illustrated by experimental results, the proposed control law presents advantages such as high control precision, effective payload swing suppression, and so on.

Nonlinear Hierarchical Control for Unmanned Quadrotor Transportation Systems

A wide range of robotic systems needs to estimate their rotation for diverse tasks like automatic control and stabilization, among many others. In regards of the limitations of traditional navigation equipments (like GPS and inertial sensors), this paper follows a vision approach based on the observation of vanishing points (VPs). Urban environments (outdoor as well as indoor) generally contain orthogonal VPs which constitutes an important constraint to fulfill in order to correctly acquire the structure of the scenes. In contrast to existing VP-based techniques, our method inherently enforces the orthogonality of the VPs by directly incorporating the orthogonality constraint into the model estimation step of the RANSAC procedure, which allows real-time applications. The model is estimated from only 3 lines, which corresponds to the theoretical minimal sampling for rotation estimation and constitutes our 3-line RANSAC. We also propose a 1-line RANSAC when the horizon plane is known. Our algorithm has been validated successfully on challenging real datasets.

/pdf/3-line-ransac-for-orthogonal-vanishing-point-detection-55f572ge13.pdf

3-line RANSAC for orthogonal vanishing point detection

Quadrotors are Vertical Take-Off and Landing aerial vehicles with many potential applications ranging from mapping to supporting rescue operations. This paper aims to provide an overview on various works carried out on the quadrotor, from the perspective of control and dynamic modelling. Also in this paper, based on the information summarized from 160 researches available, different control targets and flight missions are analysed and classified, and according to it, a general flight mission map is introduced. In addition, history of advances in development of quadrotors and set-ups proposed when performing experimental researches on quadrotors is presented.

Quadrotors unmanned aerial vehicles: a review

In this paper, we present a comparison of three control techniques: Nested Saturations, Backstepping and Sliding Modes. The control objective consists of obtaining the best control strategy to stabilize the position of a quad-rotor when using visual feedback. We propose a method to measure translational speed as well as the UAV 3D position in a local frame. The selected controllers were implemented and tested in real-time experiments. The obtained results demonstrate the performance of such methodologies applied to the quad-rotor system.

/pdf/hovering-quad-rotor-control-a-comparison-of-nonlinear-3elw2476dz.pdf

Hovering quad-rotor control: A comparison of nonlinear controllers using visual feedback

This paper present the design of a novel embedded control system for improving attitude stabilization of a quad-rotor mini UAV. The control strategy uses low cost components and includes an extra control loop based on motor armature current feedback. This additional control loop significantly improves the performance of the quad-rotor attitude stability. This technique results in a controller that is robust with respect to external disturbances as has been observed experimentally.

Hovering Flight Improvement of a Quad-rotor Mini UAV Using Brushless DC Motors

In this paper, we address the hover flight and speed regulation of a quadrotor rotorcraft to perform autonomous navigation. For this purpose, we have developed a vision system which estimates the altitude, the lateral position and the forward speed of the engine during flights. We show that the visual information allows the construction of control strategies for different kinds of flying modes: hover flight, forward flight at constant speed. A hierarchical control strategy is developed and implemented. The local stabilization of the vehicle is proven. Experimental autonomous flight was successfully achieved which validates the visual algorithm and the control law.

/pdf/vision-based-altitude-position-and-speed-regulation-of-a-1die4aljvd.pdf

Vision-based altitude, position and speed regulation of a quadrotor rotorcraft

We address the problem of hover flight and translational velocity regulation of a quad-rotorcraft unmanned aerial vehicle (UAV) with the main objective of allowing the vehicle to navigate autonomously. This paper complements and improves previous researches considering multiple-camera systems and nonconventional sensors, which deal only with stabilizing the aerial vehicle in hover or in take-off and landing tasks. A vision system has been implemented to estimate the vehicle’s altitude, lateral position, and forward velocity during flights. It is shown that, using visual information, it is possible to develop control strategies for different kinds of flying modes, such as hover flight and forward flight at constant velocity. The stability of the closed-loop system is ensured by implementing a hierarchical control strategy. In the first stage, the performance of the proposed methodologies was validated under a simulation environment, showing satisfactory and promising results. Next, real-time experimental applications, consisting of autonomous hover and forward flight at constant velocity, were successfully achieved, validating the effectiveness of the proposed imaging algorithm and vision-based controller.

/pdf/three-dimensional-position-and-velocity-regulation-of-a-quad-tmri3oehqu.pdf

Three-dimensional position and velocity regulation of a quad-rotorcraft using optical flow

Autonomous navigation of an unmanned aerial vehicle (UAV) can be achieved with a reactive system which allows the robot to overcome all the unexpected changes in its environment. In this article, we propose a new approach to avoid frontal obstacles using known properties of the optical flow and by taking advantage of the capability of stationary flight of the rotorcraft. A state machine is proposed as a solution to equip the UAV with all reactions necessary for indoor navigation. We show how smooth transitions can be achieved by decreasing the speed of the vehicle proportional to the distance to an obstacle and by brief instants of hovering flight. Each stage of our algorithm has been tested in a mobile robot.

/pdf/optical-flow-based-controller-for-reactive-and-relative-2z9keabzdl.pdf

Eduardo Rondon

Papers

Hovering quad-rotor control: A comparison of nonlinear controllers using visual feedback

Hovering Flight Improvement of a Quad-rotor Mini UAV Using Brushless DC Motors

Vision-based altitude, position and speed regulation of a quadrotor rotorcraft

Three-dimensional position and velocity regulation of a quad-rotorcraft using optical flow

Optical flow-based controller for reactive and relative navigation dedicated to a four rotor rotorcraft