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Fiducials
(Thu Oct 24, lect 16)
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Uses of Fiducials
Logistics
Introduction to Fiducials
A specific kind of graphical image combined with an algorithm
Generally the recognition algorithm includes a tool to create the images
Standardized image with known dimensions
Conceptually simple geometrical transformation
Perspective distortion is used to compute relative pose (orientation and distance)
Tricky business with TFs and POV!
Aruco Fiducials
We have used Ubiqutiy Robotics
aruco_detect
Easily recognized by camera using computer vision
Known dimensions
Known pose (location in 6d) within a certain coordinate system
Think of that as the map coordinate system
Creating Aruco Fiducials
Lots of ways, in code or online
e.g.
Aruco Markers Generator
You can choose the size, the number of bits, and the number of distinct tags
Tag Detection
How do we get the transform between a camera and fiducials?
Compare the orientation, size and transfor betwen the obsrved image and the known features of the fiducial
ROS Wiki with demo
Tag Placement
Trade-offs: along the wall, along the ceiling
How many tags do you need?
Can you have too many?
Remember: the tag is not identifying a
thing
It is just a point where your real world coordinate system is bound to your robot coordinate system
Fiducial Localization
In general localization means computing the transform between
real world
and
robot
coordinates.
More specifically we are computing a transform betwen a
map
tf and a
robot_base
tf
Even more specifically what is the transform between the
pose
of the fiducial and the
pose
of the camera.
Lab Notebook Entries
A coming homework asks that you write a “howto” for our lab notebook
Here’s one about
Localization with Fiducials
from another semester
Other Resources
fiducial_follow
Ubiquity Robotics Fiducials
Two types of Fiducial Localization
Fiducial SLAM
Detect fideucials in image
Compute transform between fiducial(s) and camera (and robot)
Orient a coordinate system corresponding to the real world
Fiducial Localization with an existing map
Predefine a map with fiducials marked on it
Detect fiducials in camera image
Find transforms between fiducials and camera
Localize robot on that map
Thank you. Questions?
(random Image from picsum.photos)
Welcome
Autonomous Robotics
List of Lectures
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Final Projects
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Lectures
Sensing and Moving
Welcome
ROS From the top
ROS Nodes and Topics
Robot Hardware
Sensing with Lidar
Perception and Sensors
How do mobile Robots move?
ROS Programming Best Practices
Orienting
Robot Orientation
ROS Coordinates
The almighty TF package
How do Robots Localize?
Localization in practice
Navigating
Path Planning
Advanced Topics
Fiducials
Finite State Machines
Behavior Trees
Intro to computer Vision
Kalman Filters
Kalman Filters
Joints and Links
Manipulators
Projects
Project Work
Project Work
Last Class!
Course Resources
Guide for Teaching Asssistants!
References
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Key Papers in Robotics
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Cosi119a FAQ
The "Big Ideas"