843 research outputs found
Algorithms for Building High-Accurate Optical Tracking Systems
Die vorliegende Arbeit präsentiert eine Untersuchung von Einflussfaktoren auf die Genauigkeit eines optischen Trackingsystems zur hoch präzisen Koordinatenmessung, wie sie beispielsweise im Bereich der Computer-unterstützten Chirurgie benötigt wird. Zu den Haupteinflussfaktoren gehören die Modellierung der Aufnahmegeometrie, die verwendeten Bildverarbeitungsalgorithmen zur Markensegmentierung, welche sowohl während der Systemkalibrierung als auch während des eigentlichen Messvorgangs verwendet werden, und nicht zuletzt thermische Einflüsse.Wahrend die Modellierung der Kamerageometrie ein gut erforschter Gegenstand sowohl im Bereich der Photogrammetrie als auch des Maschinellen Sehens darstellt, existieren fur den Vergleich von verschiedenen Markentypen und deren Segmentierungsalgorithmen in bezug auf die Messgenauigkeit noch keine umfassenden Ergebnisse. Einen weiteren Bereich, der nahezu nicht untersucht ist, bilden thermische Einflüsse auf die zugrundeliegende Aufnahmegeometrie. Die vorliegende Arbeit legt ihren Schwerpunkt auf diese zwei Bereiche. Zum einen werden verschiedene Algorithmen zur Segmentierung von Messmarken vorgestellt und miteinander verglichen. Den zweiten großen Schwerpunkt bildet eine Analyse von thermischen Einflussen auf Kameras. Es wird ein Verfahren entwickelt, welches den Einfluss von Temperaturänderungen modelliert und so Messfehler kompensieren kann. Die Ergebnisse dieser Arbeit finden Anwendung in der Entwicklung eines optischen Trackingsystems fur den Einsatz in der orthopädischen Chirurgie
Positioning System for a Hand-Held Mine Detector
Humanitarian mine clearance aims at reducing the nuisance of regions infected by explosive devices. These devices need to be detected with a high rate of success while keeping a low false alarm rate to reduce time losses and personnel’s fatigue. This chapter describes a positioning system developed to track hand-held detector movements in the context of close-range mine detection. With such a system, the signals captured by the detector over time can be used to build two- or three-dimensional data. The objects possibly present in the data can then be visually appreciated by an operator to detect specific features such as shape or size or known signatures. The positioning system developed in the framework of the HOPE European project requires only a camera and an extra bar. It adds few constraints to current mine clearance procedures and requires limited additional hardware. The software developed for calibration and continuous acquisition of the position is described, and evaluation results are presented
Extrinisic Calibration of a Camera-Arm System Through Rotation Identification
Determining extrinsic calibration parameters is a necessity in any robotic
system composed of actuators and cameras. Once a system is outside the lab
environment, parameters must be determined without relying on outside artifacts
such as calibration targets. We propose a method that relies on structured
motion of an observed arm to recover extrinsic calibration parameters. Our
method combines known arm kinematics with observations of conics in the image
plane to calculate maximum-likelihood estimates for calibration extrinsics.
This method is validated in simulation and tested against a real-world model,
yielding results consistent with ruler-based estimates. Our method shows
promise for estimating the pose of a camera relative to an articulated arm's
end effector without requiring tedious measurements or external artifacts.
Index Terms: robotics, hand-eye problem, self-calibration, structure from
motio
Inspection with Robotic Microscopic Imaging
Future Mars rover missions will require more advanced onboard autonomy for increased scientific productivity and reduced mission operations cost. One such form of autonomy can be achieved by targeting precise science measurements to be made in a single command uplink cycle. In this paper we present an overview of our solution to the subproblems of navigating a rover into place for microscopic imaging, mapping an instrument target point selected by an operator using far away science camera images to close up hazard camera images, verifying the safety of placing a contact instrument on a sample or finding nearby safe points, and analyzing the data that comes back from the rover. The system developed includes portions used in the Multiple Target Single Cycle Instrument Placement demonstration at NASA Ames in October 2004, and portions of the MI Toolkit delivered to the Athena Microscopic Imager Instrument Team for the MER mission still operating on Mars today. Some of the component technologies are also under consideration for MSL mission infusion
Vision-based localization methods under GPS-denied conditions
This paper reviews vision-based localization methods in GPS-denied
environments and classifies the mainstream methods into Relative Vision
Localization (RVL) and Absolute Vision Localization (AVL). For RVL, we discuss
the broad application of optical flow in feature extraction-based Visual
Odometry (VO) solutions and introduce advanced optical flow estimation methods.
For AVL, we review recent advances in Visual Simultaneous Localization and
Mapping (VSLAM) techniques, from optimization-based methods to Extended Kalman
Filter (EKF) based methods. We also introduce the application of offline map
registration and lane vision detection schemes to achieve Absolute Visual
Localization. This paper compares the performance and applications of
mainstream methods for visual localization and provides suggestions for future
studies.Comment: 32 pages, 15 figure
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