https://pvela.gatech.edu/classes/ 2026-04-08T20:05:52+00:00 https://pvela.gatech.edu/classes/ https://pvela.gatech.edu/classes/lib/exe/fetch.php?media=wiki:dokuwiki.svg text/html 2024-08-21T01:38:55+00:00 Anonymous (anonymous@undisclosed.example.com) https://pvela.gatech.edu/classes/doku.php?id=turtlebot:adventures:movingdr&rev=1724204335&do=diff Turtlebot: Moving Part 1 ---------- Intro Assumption: Connection to and Teleoperation of the Turtlebot are functional. This first step in learning how to control a robot is to learn how to get its actuators to work. The vanilla turtlebot only really has two of them, a left wheel and a right wheel. This would be the simplest instantiation of a (non-trivial) mobile robot. The text/html 2024-08-21T01:38:55+00:00 Anonymous (anonymous@undisclosed.example.com) https://pvela.gatech.edu/classes/doku.php?id=turtlebot:adventures:rosbasic&rev=1724204335&do=diff ROS: Basic Commands / Cheat Sheet ---------- There are several commands that can help you navigate different pieces of ROS. Like an operating system, ROS sets up services that communicate between each other. Some are setup to communicate, but only if someone wants to listen. These communication channels go by the name of text/html 2024-08-21T01:38:55+00:00 Anonymous (anonymous@undisclosed.example.com) https://pvela.gatech.edu/classes/doku.php?id=turtlebot:adventures:sensing101_forwarderror&rev=1724204335&do=diff Forward Error Signal Feedback ---------- Some Basics on $SE(2)$ By now you've been able to do orientation control. The current adventure now requests that you add a little forward position control. What will be described here is yet another step towards full fledged geometric control of the Turtlebot. The geometric part means that we will try to use the natural geometry of the Turtlebots space to create feedback controls that look like what you are used to. There will be some nonlinear ma… text/html 2024-08-21T01:38:55+00:00 Anonymous (anonymous@undisclosed.example.com) https://pvela.gatech.edu/classes/doku.php?id=turtlebot:adventures:sensing101_hints&rev=1724204335&do=diff Sensing 101 Hints Bumper Events The button callback code should be pretty self-explanatory. The main thing is to create your own subscriber, then to use rostopic echo and rostopic type to understand the structure of the bumper events enough to create a properly modified version of the button callback function (the direct link to the Turtlebot $1+j0$$0 + j$$z_{des} = e^{j \theta_{des}}$ text/html 2024-08-21T01:38:55+00:00 Anonymous (anonymous@undisclosed.example.com) https://pvela.gatech.edu/classes/doku.php?id=turtlebot:adventures:sensing101_thetaerror&rev=1724204335&do=diff The orientation estimate is published as a quaternion for the Turtlebot. However, the turtlebot is a planar creature, so the full quaternion is never used. What parts are used? Which of the four values in the odometry quaternion correspond to the real value? The other one would then be the complex value. Which is it?$ z = x + jy$$$ z_{des} = e^{j \theta_{des}} = \cos(\theta_{des}) + j \sin(\theta_{des})$$$z_{des}$$z_des$$z_{curr}$$$z_{err} = z_{curr}^{-1} z_{des} = z_{des} \,/\, z_{curr},$$$z… text/html 2024-08-21T01:38:55+00:00 Anonymous (anonymous@undisclosed.example.com) https://pvela.gatech.edu/classes/doku.php?id=turtlebot:adventures:sensing101&rev=1724204335&do=diff Turtlebot: Sensing Part 1 ---------- Intro It might seem weird to have an adventure entitle sensing the turtlebot, but in the world of controls actuation and sensing go hand in hand. We really need to sense the turtlebot to be able to properly control it. That said, the turtlebot does indeed have a few sensors on it that are used to measure movement of the turtlebot. The first are a pair of rotary encoders, used to measure the rotational velocity of the wheels (as you've seen, commanding a… text/html 2024-08-21T01:38:55+00:00 Anonymous (anonymous@undisclosed.example.com) https://pvela.gatech.edu/classes/doku.php?id=turtlebot:adventures:sensing102_hints&rev=1724204335&do=diff Connecting to the Kinect Sensor w/out Color+Depth Registration If you have trouble with subscribing to the depth data or to the linescan data, then it may be that the main publisher needed is not running, or is publishing to another topic. One fix, found text/html 2024-08-21T01:38:55+00:00 Anonymous (anonymous@undisclosed.example.com) https://pvela.gatech.edu/classes/doku.php?id=turtlebot:adventures:sensing102&rev=1724204335&do=diff Turtlebot: Sensing Part 2 ---------- Intro Now we get to the sensing part that maybe you were thinking about initially. This is sensing of the world outside of the turtlebot (not using proprioceptive sensors). The default version comes with a kinect sensor, so it has an on-board RGB camera and also a depth image. To access it you would have to do one of the following two things (1) run the minimal launch file plus a sensor launch file separately (can you figure out what this second launch … text/html 2024-08-21T01:38:55+00:00 Anonymous (anonymous@undisclosed.example.com) https://pvela.gatech.edu/classes/doku.php?id=turtlebot:adventures:wandering&rev=1724204335&do=diff Turtlebot: Wandering Like a Zombie ---------- Intro Here, we will try to combine a little bit of sensing with actuation, but it will be somewhat mindless. Given the popularity of zombies at the time of this writing, let's say that we are creating a zombie mode for the turtlebot. Historically this zombie mode has been called wandering; it's a rite of passage for robotics students to create their own wandering zombie robot.