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[DPRG] Question about the origin of "theta"

Subject: [DPRG] Question about the origin of "theta"
From: Paradug paradug at gmail.com
Date: Sun Jan 18 13:43:43 CST 2015

Pat,
    I believe the term "theta" comes from the use of 2D Polar coordinates to describe the robot's pose. Since robot kinematics are often developed by folks who are strong mathematicians, they tend to use the mathematical terms.    From my very meager experience in robotics, I have noticed that in most code examples "theta" is more frequently used than the term robot heading. However, It is interesting that the difference between a target's bearing and the robot's heading  is often called "heading error".  

    I maybe misunderstanding your descriptions of the terms "heading' and "bearing'.  Since “aiming”, could be interpreted as “the direction of the robot” or as “the direction we want to go”, I would describe heading differently . "Heading" is the direction that the robot is going (i.e., theta), not the "direction we're aiming". Your definition of "Bearing" (i.e., "direction to an object" or “direction to a target”) is fine.  

     You might find slides 4 and 5 from http://dprgblog.files.wordpress.com/2014/03/cancansoccer_algorithms_tutorial1.pdf a good way to show your team. 

Regards,
Doug P.

-----Original Message----- 
From: Patrick R. Michaud 
Sent: Sunday, January 18, 2015 12:19 PM 
To: dprglist 
Subject: [DPRG] Question about the origin of "theta" 

I'm in the process of trying to add a little precision and rigor to my understanding of common robotics terms, so I can improve the way I relate concepts to my robotics teams and others that I teach or interact with.

In DPRG I've heard a number of people talk about "theta" in robot navigation, whereas I've always tended to use terms like "heading" and "bearing" (from standard navigation terminology) for "direction we're aiming" and "direction to an object".

So, I'm curious:  Is "theta" the common term among roboticists for this?  Is there a nuance I'm missing?  And, more generally -- is there a good reference / resource of common robotics names and concepts?

Thanks!

Pm
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