Odom value error

asked 2020-04-22 04:45:34 -0500

harrynick gravatar image

I'm using turtlebot 2 with kobuki base. I have launched a world file with turtlebot, the turtlebot came in its default positiom (0,0,0). Now i want my robot to be at (-1.6,0,0). I have made the changes accordingly and now the robot is in required position, but when i checked the odom value it is showing that position as (0,0,0). why it is showing like that?? Do i need to make some other change??

Thanks in advance

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Comments

Odometry is relative to when the calculation was initiated/reset (or at least: that's how it's typically implemented in many ROS nodes/drivers). It's not world-referenced like you seem to be expecting.

gvdhoorn gravatar image gvdhoorn  ( 2020-04-22 05:14:08 -0500 )edit

So you where telling this is not possible?? but this problem was not there with turtlebot3. In turtlebot3 when i change the intial position of robot and checked the odom value it shows as same as of the intial pose value that i gave. This thing is not happening with turtlebot2

harrynick gravatar image harrynick  ( 2020-04-22 05:20:34 -0500 )edit

So you where telling this is not possible?

No, that's not what I'm writing at all.

What I wrote is that in most cases, odometry calculation is relative. And it's typically relative to when the algorithm was started. So that makes the point you start the algorithm 0, 0, 0 automatically.

but this problem was not there with turtlebot3. In turtlebot3 when i change the intial position of robot and checked the odom value it shows as same as of the intial pose value that i gave. This thing is not happening with turtlebot2

well, it sounds like it then that the authors of the TB2 node(s) implemented things differently than those of the TB3 nodes.

I would not know about that..

The only thing I wanted to point out is that you seemed to expect odometry to always be absolutely referenced against some external point ...(more)

gvdhoorn gravatar image gvdhoorn  ( 2020-04-22 05:26:11 -0500 )edit

.. some externally referenced "start state", that would seem to be a design decision.

You'd have to ask them about that.

gvdhoorn gravatar image gvdhoorn  ( 2020-04-22 05:26:35 -0500 )edit