Amiga jumped around when doing in-place turns at the width of 28 inches

general
1

Hi Guys,

We were interested in seeing if Amiga could fit into our client’s 5-feet wide rows so we adjusted the width of Amiga to 28 inches and tele-oped it for a bit. We observed that Amiga wobbled and jumped when making turns, especially in the clockwise direction, but not so much in the counter clockwise direction. Have you guys encountered this issue before? Do you have any suggestions for fixing this?

You can see the videos in this driver here: Farm-ng videos - Google Drive

Best,
Di

2

Hi Di,

Thanks for sharing the videos. I don’t think we’ve ever tried a configuration that narrow! Since the Amiga is a skid-steered robot, a long and narrow configuration is not going to work well.

My quick suggestion is to try pushing the front & back tires as close as possible, but I’m concerned it’ll still be too narrow. Alternatively, could you get longer bars and span across the 5 foot wide rows rather than fitting between rows?

Some more detailed notes:

  1. The track should be measured from the center of the left tires to the center of the right tires. So your track (or width) is actually closer to 18".
  2. We typically use a 2:1 track to baseline ratio, while you’re probably at 0.75:1. You can try to push the front and back tires closer together to get the baseline down and get that ratio up.

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For reference, we had discussed this a while back: Calculation or guide for wheel base vs track width · Issue #43 · farm-ng/amiga-dev-kit · GitHub

Let me know what you try / how it goes.
– Kyle

3

Thank you for the prompt response Kyle!

We are currently working for a tree nursery, where the trees can grow up to 8 feet tall. Therefore, spanning across the rows sounds pretty difficult too. Thank you for your suggestions still. We will try shorten the wheelbase and see if the turnings would be more smooth. Do you know why one side is jumping more than the other though? Also, what is the narrowest configuration you have tested?

Best,
Di

4

OK makes sense, narrow config it is. I can’t see any record of what the narrowest we’ve tested would be. Definitely 36", but I’m not sure if we’ve tried below that.

For the jumping:

  1. The turning should be a lot smoother on dirt. You should test there.
  2. I saw in one of the videos you were spit-balling some ideas, and yeah it could be anyone of those things. Tire pressure, alignment, etc.
  3. A big thing could be the offset of your bars, giving you an eccentric COM. Try centering those (assuming you don’t want to cut them yet).
  4. Finally, you could also try adding a rigid, centered mass or four rigid masses above each wheel.

– Kyle

5

Thank you Kyle! The jumping issue from yesterday is gone now. You were right about the track width. Turned out that we just needed to put the right track width in the settings. We tried track width of 20 inches, and added weight by sitting on it. The turning is pretty smooth now. You can see videos of us testing on 3 type of ground here: 03-14-2023 - Google Drive

6

Great! Glad it’s working now.

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