AR4 Leader arm

What do you mean by leader arm?

An arm (usually built with cheaper materials / motors) that can be used to remotely control the follower arm (for example AR4). This is used to teleop or to train AI models for the arm. The leader is only used to read values for the joints from.

I have not seen that for the AR4, but it would be cool to implement it.

Was thinking of modifying this design to meet the same proportions as AR4: https://github.com/AlexanderKoch-Koch/low_cost_robot As long as the proportions and joints are the same, it should work fine. I have to get better at cad to learn how to modify it though! Will post when I get it done.

I have made a leader arm for the GELLO project. See https://github.com/wuphilipp/gello_mechanical/tree/main/ar4

Omg, thank you! Saved me a ton of work!!

Do you have any videos of this working Aleksandr? This looks really great.

Cheers

Here's a clip of the arm in action:

Wow! Very cool!

Is the software totally separate to the AR4 control software?

Yeah, and I've had to develop my own firmware. The main issue is that you have to be able to issue a "move joints" command while the arm is already in motion from a previous command and have the arm change where it's going. The stock firmware doesn't support this. You don't want the arm to come to a complete stop between movement commands. This creates a huge amount of vibration and jerk especially when you're issuing commands at max speed and acceleration.

It remains an open question how to do this in the best way to minimize jerk while maximizing responsiveness. If you have any ideas, please share.

Is your firmware open source? Maybe I can contribute when I get to that point. Seems like we’re doing similar things

I'll have to do some code cleanup but I can share my code. Just let me know when you get to that point

I’m at that point! 🙂

any chance you have got around to doing this yet?

Will try to get it done this week 🙂

ETA Wednesday

Any chance you got to it yet?

I'm working on this 🙂

I've released as open-source my firmware and some of the other tools I wrote at https://github.com/adob/ar4 .

This includes the GELLO episode recorder which can be used to record teleoperation sessions for later training with ACT (Action-Chunking with Transformers). There is also a GUI tool that you can use to move the arm using arrow keys from a first-person perspective (assuming you have a camera mounted).

I haven't gotten to releasing the ACT training code. Let me know if there is interest.

Looks great, excited to try it! I wish the license was more permissive (mit, etc). ACT training code would be great, this is the same thing I’m working on doing, but haven’t got that far yet. Thank you for sharing this!!

As far as licensing, I do have a dependency on ViSP, which necessitates the GPL. But also, just curious, but why is permissive licensing important to you? You can do pretty much whatever you want with GPL code, no?

I'll work on getting my ACT changes open as well in the coming week or two. Curious about what you're working on.