High-throughput biomass estimation in rice crops using UAV multispectral imagery

in Journal of Intelligent and Robotic Systems (2019), 96(3-4), 573--589

A Hierarchical Strategy for Real-Time Tracking On-Board UAVs

in ICUAS 2012 : 2012 International Conference on Unmanned Aircraft Systems (2012, June)

In this paper, we present a real-time tracking strategy based on direct methods for tracking tasks on-board UAVs, that is able to overcome problems posed by the challenging conditions of the task: e.g ... [more ▼]

In this paper, we present a real-time tracking strategy based on direct methods for tracking tasks on-board UAVs, that is able to overcome problems posed by the challenging conditions of the task: e.g. constant vibrations, fast 3D changes, and limited capacity on-board. The vast majority of approaches make use of feature-based methods to track objects. Nonetheless, in this paper we show that although some of these feature-based solutions are faster, direct methods can be more robust under fast 3D motions (fast changes in position), some changes in appearance, constant vibrations (without requiring any specific hardware or software for video stabilization), and situations where part of the object to track is out the field of view of the camera. The performance of the proposed strategy is evaluated with images from real-flight tests using different evaluation mechanisms (e.g. accurate position estimation using a Vicon sytem). Results show that our tracking strategy performs better than well known feature-based algorithms and well known configurations of direct methods, and that the recovered data is robust enough for vision-in-the-loop tasks. [less ▲]

On-board and Ground Visual Pose Estimation Techniques for UAV Control

in Journal of Intelligent and Robotic Systems (2011), 61(1-4), 301-320

In this paper, two techniques to control UAVs (Unmanned Aerial Vehicles), based on visual information are presented. The first one is based on the detection and tracking of planar structures from an on ... [more ▼]

In this paper, two techniques to control UAVs (Unmanned Aerial Vehicles), based on visual information are presented. The first one is based on the detection and tracking of planar structures from an on-board camera, while the second one is based on the detection and 3D reconstruction of the position of the UAV based on an external camera system. Both strategies are tested with a VTOL (Vertical take-off and landing) UAV, and results show good behavior of the visual systems (precision in the estimation and frame rate) when estimating the helicopter's position and using the extracted information to control the UAV. [less ▲]

Fuzzy-4D/RCS for Unmanned Aerial Vehicles

in BICS 2010 Conference on Brain-Inspired Cognitive Systems (2010, July)

Abstract This paper presents an improvement of the cognitive architecture, 4D/RCS, developed by the NIST. This improvement consist of the insertion of Fuzzy Logic cells (FLCs), in different parts and ... [more ▼]

Abstract This paper presents an improvement of the cognitive architecture, 4D/RCS, developed by the NIST. This improvement consist of the insertion of Fuzzy Logic cells (FLCs), in different parts and hierarchy levels of the architecture, and the adaptation of this architecture for Unmanned Aerial Vehicles (UAVs). This advance provides an improvement in the functionality of the system based on the uses of the Miguel Olivares’ Fuzzy Software for the definition of the FLCs and its adaptative learning algorithm. These adaptative-FLCs contribute with the reduction of the uncertainty in the data sensor adquisition, a more adaptative behavior of the system to the real world and the reduction of the computational cost in the decision making. [less ▲]

Omnidirectional vision applied to Unmanned Aerial Vehicles (UAVs) attitude and heading estimation

in Robotics and Autonomous Systems (2010), 58(6), 809-819

This paper presents an aircraft attitude and heading estimator using catadioptric images as a principal sensor for UAV or as a redundant system for IMU (Inertial Measure Unit) and gyro sensors. First, we ... [more ▼]

This paper presents an aircraft attitude and heading estimator using catadioptric images as a principal sensor for UAV or as a redundant system for IMU (Inertial Measure Unit) and gyro sensors. First, we explain how the unified theory for central catadioptric cameras is used for attitude and heading estimation, explaining how the skyline is projected on the catadioptric image and how it is segmented and used to calculate the UAV's attitude. Then, we use appearance images to obtain a visual compass, and we calculate the relative rotation and heading of the aerial vehicle. Finally the tests and results using the UAV COLIBRI platform and the validation of them in real flights are presented, comparing the estimated data with the inertial values measured on board. (C) 2010 Elsevier B.V. All rights reserved. [less ▲]

Unmanned aerial vehicles UAVs attitude, height, motion estimation and control using visual systems

in AUTONOMOUS ROBOTS (2010), 29(1), 17-34

This paper presents an implementation of an aircraft pose and motion estimator using visual systems as the principal sensor for controlling an Unmanned Aerial Vehicle (UAV) or as a redundant system for an ... [more ▼]

This paper presents an implementation of an aircraft pose and motion estimator using visual systems as the principal sensor for controlling an Unmanned Aerial Vehicle (UAV) or as a redundant system for an Inertial Measure Unit (IMU) and gyros sensors. First, we explore the applications of the unified theory for central catadioptric cameras for attitude and heading estimation, explaining how the skyline is projected on the catadioptric image and how it is segmented and used to calculate the UAV's attitude. Then we use appearance images to obtain a visual compass, and we calculate the relative rotation and heading of the aerial vehicle. Additionally, we show the use of a stereo system to calculate the aircraft height and to measure the UAV's motion. Finally, we present a visual tracking system based on Fuzzy controllers working in both a UAV and a camera pan and tilt platform. Every part is tested using the UAV COLIBRI platform to validate the different approaches, which include comparison of the estimated data with the inertial values measured onboard the helicopter platform and the validation of the tracking schemes on real flights. [less ▲]

Visual 3-D SLAM from UAVs

in Journal of Intelligent and Robotic Systems (2009), 55(4-5), 299-321

The aim of the paper is to present, test and discuss the implementation of Visual SLAM techniques to images taken from Unmanned Aerial Vehicles (UAVs) outdoors, in partially structured environments. Every ... [more ▼]

The aim of the paper is to present, test and discuss the implementation of Visual SLAM techniques to images taken from Unmanned Aerial Vehicles (UAVs) outdoors, in partially structured environments. Every issue of the whole process is discussed in order to obtain more accurate localization and mapping from UAVs flights. Firstly, the issues related to the visual features of objects in the scene, their distance to the UAV, and the related image acquisition system and their calibration are evaluated for improving the whole process. Other important, considered issues are related to the image processing techniques, such as interest point detection, the matching procedure and the scaling factor. The whole system has been tested using the COLIBRI mini UAV in partially structured environments. The results that have been obtained for localization, tested against the GPS information of the flights, show that Visual SLAM delivers reliable localization and mapping that makes it suitable for some outdoors applications when flying UAVs. [less ▲]