320 research outputs found
Encoderless Gimbal Calibration of Dynamic Multi-Camera Clusters
Dynamic Camera Clusters (DCCs) are multi-camera systems where one or more
cameras are mounted on actuated mechanisms such as a gimbal. Existing methods
for DCC calibration rely on joint angle measurements to resolve the
time-varying transformation between the dynamic and static camera. This
information is usually provided by motor encoders, however, joint angle
measurements are not always readily available on off-the-shelf mechanisms. In
this paper, we present an encoderless approach for DCC calibration which
simultaneously estimates the kinematic parameters of the transformation chain
as well as the unknown joint angles. We also demonstrate the integration of an
encoderless gimbal mechanism with a state-of-the art VIO algorithm, and show
the extensions required in order to perform simultaneous online estimation of
the joint angles and vehicle localization state. The proposed calibration
approach is validated both in simulation and on a physical DCC composed of a
2-DOF gimbal mounted on a UAV. Finally, we show the experimental results of the
calibrated mechanism integrated into the OKVIS VIO package, and demonstrate
successful online joint angle estimation while maintaining localization
accuracy that is comparable to a standard static multi-camera configuration.Comment: ICRA 201
A Comprehensive Introduction of Visual-Inertial Navigation
In this article, a tutorial introduction to visual-inertial navigation(VIN)
is presented. Visual and inertial perception are two complementary sensing
modalities. Cameras and inertial measurement units (IMU) are the corresponding
sensors for these two modalities. The low cost and light weight of camera-IMU
sensor combinations make them ubiquitous in robotic navigation. Visual-inertial
Navigation is a state estimation problem, that estimates the ego-motion and
local environment of the sensor platform. This paper presents visual-inertial
navigation in the classical state estimation framework, first illustrating the
estimation problem in terms of state variables and system models, including
related quantities representations (Parameterizations), IMU dynamic and camera
measurement models, and corresponding general probabilistic graphical models
(Factor Graph). Secondly, we investigate the existing model-based estimation
methodologies, these involve filter-based and optimization-based frameworks and
related on-manifold operations. We also discuss the calibration of some
relevant parameters, also initialization of state of interest in
optimization-based frameworks. Then the evaluation and improvement of VIN in
terms of accuracy, efficiency, and robustness are discussed. Finally, we
briefly mention the recent development of learning-based methods that may
become alternatives to traditional model-based methods.Comment: 35 pages, 10 figure
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