[ros-users] [Discourse.ros.org] [ROS Projects] Tractobots, my attempts at field robots

Kyler Laird ros.discourse at gmail.com
Thu Mar 30 00:15:17 UTC 2017

OK...I'm finally butting up against transforms.  I'm going to have to do something more complicated for Tractobot03 because of the location of the satellite antennas.
<img src='/uploads/ros/original/1X/04c5a094ca36ddc86f51da1033c001d97255232a.jpg'>

I tried hiring an expert on Upwork but I'm having trouble getting messages there now.  So I might have to figure this out on my own.  I'm overwhelmed.

I have this very fuzzy understanding that I need to:
1. Establish a world frame and a base frame.
2. Define the base, the loader arms on which the antennas are mounted, and the rear hitch.
3. Translate the satellite navigation data into odometry and pose messages.
4. Use transforms to determine the hitch location using the satellite data.

Unfortunately, every one of those steps feels insurmountable right now.  And I don't even know if I'm on a reasonable path.

My fallback plan is to do some simple nvector calculations to move the satellite-derived position half way between the primary antenna and the secondary antenna.  (The position of the secondary antenna is given as meters of latitude and meters of longitude from the primary antenna.)  Then I can just pretend that my antenna is on the centerline of the tractor (like my others have been).

Of course it's likely that there will be a slight offset, so I'll tweak the "half way" calculation as necessary.  And I will have tilt data so I really should use it to calculate the ground-level position.  I can imagine this eventually working well enough but it would be so nice to have transforms working so that I can do this cleanly.

I will gratefully welcome assistance/advice.  And I'm quite willing to pay for help!

[Visit Topic](https://discourse.ros.org/t/tractobots-my-attempts-at-field-robots/1486/8) or reply to this email to respond.

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