Adding URDF

So now that I have a whole bunch of sensors on the robot it's time to talk about transforms. 

Transforms are the relationships between different frames of reference on the robot. For example the center of the robot could be 5 cm off the ground, but the laser scanner is 10 cm off the ground. 

So your transform would be ( 0 0 5) to indicate that it is 5 cm up in the z direction (the convention is x y z).

However as you can imagine it gets messy trying to keep track of all of the transforms as the robot grows in complexity. What can end up happening is that you have transforms tucked away in different files, and its not obvious where to find them if you need to change one. 

Enter URDF!

URDF stands for Unified Robot Description Format and it is used to create a visual model of the robot as well as describe the relationships between links. Essentially it is an XML file with some dimensions and other values. The great thing about it is that you can use macros to make it really efficient to specify the details and have one central spot to edit the robot characteristics.

Recently I created my own URDF file to describe my robot. What I need to do next is to connect it with a robot state publisher that will publish the transforms for me.