Possible new design, the Arc Bot

I’ll preface this with “I’m not a coder”.
I was wondering if anyone has considered adding a circular design Farm Bot to the line-up ?
I’ve given this some thought, even considered a name, “Arc Bot”.
To me, this could greatly simplify construction with only a single drive wheel needed at the outer end and a central pivot that all the wires and plumbing could come up through. A 10’ boom would enable a 20’ diameter circular garden without the need for added support of the boom.
While I’m not sure what types of encoders the Farm Bot uses, a circular design would only need a single rotary encoder to measure the arc travel, along with the linear encoders for the working head travel down the boom and Z-axis encoder.


It sounds like a neat idea. Have you read about the FarmBot Eden?


No I hadn’t, thanks for the PDF.
I haven’t read the entire paper yet, but seems very similar to the concept idea I had from the quick scan through.
It also seems to verify my thought that this type design would reduce part count and cost. It just seems to me that most of the leg work is already done with the current Farm Bot programming/software, would just need to modify the User Interface and some of the control coding to accept the rotational design vs the linear of the current design.

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This idea has come up a few times:

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I was not involved with the project, as it was mostly focused on hardware, but from a software perspective, the project would require substantial changes to existing packages since FarmBot has worked with a traditional X/Y/Z system for 7 years now. There are a lot of assumptions baked into the software as a result.

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I thought it would be cool to do a FarmBot like a delta 3d printer and ditch the rails.


I understand, I just wasn’t sure if the idea had been tossed around.

As I initially stated, I’m not a programmer/code writer. I am in the process of trying to learn for use with a few Arduino controlled projects.

While the Farm Bot, in its current design, is closer to the more traditional American farming/gardening layout, it occurred to me that a circular methodology would be a much cheaper method from a parts and cost perspective.

The proposed FarmBot Eden (in the PDF file) is based on a central gimbal that provides both circular movement and all of the lateral support.

The concept I had in mind is more akin to modern irrigation platforms with a central pivot at the well and drive wheels at the end of each section of irrigation pipe. This type of design would divide the lateral load between the 2 points allowing for lighter, cheaper construction materials to be used

I crunched a few numbers. A 10’ radius circle would give a tad over 314 sq ft of area. Granted, not all would be usable space, but if you figure 300 sq ft usable, that’s the approximate same coverage area as the original Farm Bot Genesis.

I also calculated the arc length at the extreme distance of 10’ using the standard 4,096 count rotary encoder. If I punched in the number correctly, each increment would be equal to a bit over 1” arc length travel per encoder increment, easily accurate enough for this application. A 20’ diameter radius, using the same standard 4,096 rotary encoder, figures out to a 3.75” arc length with total area of 1,256 sq ft. Even at 80% of total area being usable space, that’s over 1,000 sq ft of garden space. Almost double that of the current Genesis Max model.

Like you said, it would take some redesign of the current system. A new User Interface would have to be created and calculations for plant and row spacing based on distance from center and arc travel vs linear movement.

This type design would be a more permanent install as the central pivot would have to be anchored or buried.

While there are design hurdles, it seems to me that many of the basic bones are already in place in the current system.

Just some my thoughts on the idea.


@jebba You can’t ditch rails in a delta 3d printer design. Instead of having three horizontal rails (2X, 1Y) you’d need three vertical ones.


Ya, I didn’t word that great. I was thinking in terms of the level rails on wood. With delta, you avoid all that.

I’ve been reading more of the Dartmouth proposal on the Eden.
Does anyone know if they made any of the code they developed public ?
Specifically, the Polar coordinate system they developed for use with it.

If not, I think I’ll try contacting them to see if they would be willing to share it.


I’m not sure under which license the FarmBot software is released. Could be that is it mandatory to make it public (I hope so). @RickCarlino or @roryaronson should be able to answer that.

The license FarmBot uses is MIT, so others aren’t required to share any code. Even if it was another license (such as GPL), Dartmouth wouldn’t be forced to distribute code if they didn’t distribute binaries.


masze, thanks for the two email contacts you listed.
I went to the college website and found he contact info for Dr Ronald Lasky, the Faculty Advisor list on the paper. I sent him an email last night asking:

  1. If FarmBot Eden was still a work in progress.
  2. If they had, were planning on, or were willing to share the coding they’d created.

I did specify the parts I was most interested in were the code developed for the User Interface and the Polar Coordinate system.

After perusing the paper on Eden, a couple things stood out that, I personally, didn’t care for.
First, the design they opted for used a gimbal design. To me, this severely limited the length of the boom and resultant work space.
Also, due to using a NEMA 17 stepper motor with 100:1 gearbox, made traversing speed extremely slow and made accurate movement difficult such that they had to design and build a single multi-task tool head instead of a tool changing system, like the Genesis models have.
I do have to admit, based on the design criteria and price point specifications laid out in their initial guidelines, the design they came up with fits well.

My original design thoughts incorporated an outrigger drive system along with using a rotary encoder at the central pivot. Based on the specs of a 4,096 point rotary encoder, the arc length calculations (per increment of the encoder) should be more than accurate enough for plant spacing requirements and mapping, out to a radius of about 20 feet. In closer to the central pivot, this accuracy should translate to movement accuracy enabling the use of a tool change system.

For now, I’ll just be waiting for a response from Dr Lasky and hope they are willing to share their work. If I don’t hear back, I’ll try contacting some of the other individuals involved.


I just received a response from Dr Lasky. It appears the project was closed and no further development planned. He also told me that he wasn’t directly involved in the project and didn’t have any information.
A closer read of the report stated they concentrated on the mechanical aspects of the design and not the software. Given the report is over 2 years old, no longer an active project, and probably little, to no code written or modified, I think it’s a dead end.

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@masze, here is detailed information for all our licensing choices: https://meta.farm.bot/docs/licensing

@jpigg55, here is another polar coordinate FarmBot student project you may be interested in. FarmBot Inc sponsored this team and we have their prototype in our warehouse :wink:

That’s me :point_down: with the blue hair at the senior project demo day, along with the student team and their faculty advisor, Dr. Jim Widmann, who also advised me when I took senior project!

We have forked versions of the code they developed:

  • A basic GUI mostly for development purposes
  • A modified firmware that converts cartesian coordinates to polar coordinates, with the origin at the center pivot. This can be mostly used with the rest of the FarmBot software stack untouched.

The primary flaw with their hardware design (which I actually advised them against in the ideation phases :grimacing: lol) was the stepper motor and gearbox set up in a ‘direct drive’ configuration. There is just no good way to control a massive boom arm with a tiny shaft like that. But, they wanted to try it, and trial and error is part of the senior project experience, so that’s what they built :slight_smile: The hardware did work well initially, but after dozens of movements, significant backlash began developing in the system where the gearbox output shaft interfaced with the column. By the end of the project demo day I think they had upwards of 45 degrees of backlash as the shaft interface plate wore out.

Since they finished up, and as of this writing, FarmBot Inc has not further pursued the development of polar coordinate bots, though it is something we would like to do in the future.


Thanks for the links and info Rory.
And yes, I’m very interested. Not a lot of info with on other Polar coordinate project on the page the link takes you to, but I haven’t dug into it much yet.
I just see too much potential and advantage with the rotary design over the rectangular one. The biggest advantage I see is the ease of getting rid of the tracked drive system.
While not as scalable, the simplicity and lower cost of a rotational FarmBot is just too much to ignore, in my opinion.

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Also check out the Hangprinter:

This could be used for large/tall gardens, perhaps.


:heart: for this Torbjörn Ludvigsen design !

I like this idea with something simple like anchoring to a pvc frame.

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