215 research outputs found
Visual servoing of aerial manipulators
The final publication is available at link.springer.comThis chapter describes the classical techniques to control an aerial manipulator by means of visual information and presents an uncalibrated image-based visual servo method to drive the aerial vehicle. The proposed technique has the advantage that it contains mild assumptions about the principal point and skew values of the camera, and it does not require prior knowledge of the focal length, in contrast to traditional image-based approaches.Peer ReviewedPostprint (author's final draft
Hybrid visual servoing with hierarchical task composition for aerial manipulation
© 2016 IEEE. Personal use of this material is permitted. Permission from IEEE must be obtained for all other uses, in any current or future media, including reprinting/republishing this material for advertising or promotional purposes, creating new collective works, for resale or redistribution to servers or lists, or reuse of any copyrighted component of this work in other works.In this paper a hybrid visual servoing with a hierarchical task-composition control framework is described for aerial manipulation, i.e. for the control of an aerial vehicle endowed with a robot arm. The proposed approach suitably combines into a unique hybrid-control framework the main benefits of both image-based and position-based control schemes. Moreover, the underactuation of the aerial vehicle has been explicitly taken into account in a general formulation, together with a dynamic smooth activation mechanism. Both simulation case studies and experiments are presented to demonstrate the performance of the proposed technique.Peer ReviewedPostprint (author's final draft
Modelling the Xbox 360 Kinect for visual servo control applications
A research report submitted to the faculty of Engineering and the built environment, University of the Witwatersrand, Johannesburg, in partial fulfilment of the requirements for the degree of Master of Science in Engineering.
Johannesburg, August 2016There has been much interest in using the Microsoft Xbox 360 Kinect
cameras for visual servo control applications. It is a relatively cheap
device with expected shortcomings. This work contributes to the practical
considerations of using the Kinect for visual servo control applications.
A comprehensive characterisation of the Kinect is synthesised
from existing literature and results from a nonlinear calibration procedure.
The Kinect reduces computational overhead on image processing
stages, such as pose estimation or depth estimation. It is limited
by its 0.8m to 3.5m practical depth range and quadratic depth resolution
of 1.8mm to 35mm, respectively. Since the Kinect uses an
infra-red (IR) projector, a class one laser, it should not be used outdoors,
due to IR saturation, and objects belonging to classes of non-
IR-friendly surfaces should be avoided, due to IR refraction, absorption,
or specular reflection. Problems of task stability due to invalid
depth measurements in Kinect depth maps and practical depth range
limitations can be reduced by using depth map preprocessing and
activating classical visual servoing techniques when Kinect-based approaches
are near task failure.MT201
Uncalibrated visual servo for unmanned aerial manipulation
© 20xx IEEE. Personal use of this material is permitted. Permission from IEEE must be obtained for all other uses, in any current or future media, including reprinting/republishing this material for advertising or promotional purposes, creating new collective works, for resale or redistribution to servers or lists, or reuse of any copyrighted component of this work in other works.This paper addresses the problem of autonomous servoing an unmanned redundant aerial manipulator using computer vision. The overactuation of the system is exploited by means of a hierarchical control law, which allows to prioritize several tasks during flight. We propose a safety-related primary task to avoid possible collisions. As a secondary task, we present an uncalibrated image-based visual servo strategy to drive the arm end-effector to a desired position and orientation by using a camera attached to it. In contrast to the previous visual servo approaches, a known value of camera focal length is not strictly required. To further improve flight behavior, we hierarchically add one task to reduce dynamic effects by vertically aligning the arm center of gravity to the multirotor gravitational vector, and another one that keeps the arm close to a desired configuration of high manipulability and avoiding arm joint limits. The performance of the hierarchical control law, with and without activation of each of the tasks, is shown in simulations and in real experiments confirming the viability of such prioritized control scheme for aerial manipulation.Peer ReviewedPostprint (author's final draft
Adaptive Autonomous Navigation of Multiple Optoelectronic Microrobots in Dynamic Environments
The optoelectronic microrobot is an advanced light-controlled micromanipulation technology which has particular promise for collecting and transporting sensitive microscopic objects such as biological cells. However, wider application of the technology is currently limited by a reliance on manual control and a lack of methods for simultaneous manipulation of multiple microrobotic actuators. In this article, we present a computational framework for autonomous navigation of multiple optoelectronic microrobots in dynamic environments. Combining closed-loop visual-servoing, SLAM, real-time visual detection of microrobots and obstacles, dynamic path-finding and adaptive motion behaviors, this approach allows microrobots to avoid static and moving obstacles and perform a range of tasks in real-world dynamic environments. The capabilities of the system are demonstrated through micromanipulation experiments in simulation and in real conditions using a custom built optoelectronic tweezer system
Visual servoing of a five-bar linkage mechanism /
This document is the written product of the graduation project developed: Visual Servoing of a Five-bar Linkage Mechanism. This project means to venture into the fields
of a method of control, with visual feedback, known as Visual Servoing. The contents
of this document show a summary of all the theory taken into account to realize the
project. They also shows how other people have approached this method. These pages
present the project establishing its aims, the importance of its realization, a detailed
description of how it was carried out - including experiments and obstacles, - and the
results obtained. This document also informs how is this work of use and what can
be done from it. In the same way, here are consigned the books, articles, and works
consulted in the way, which in their own pages provide a large quantity of references
and information.Incluye referencias bibliográfica
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