[iseanstevens]

(Oops saw other comment linked, but I’ll leave this comment in case summary is helpful)

Check out the SO100 arm, being supported by Huggingface and others. Only 4 axis, but cheap AF (<$250/arm) and using ML to make it more capable than 4 axis would seem. Also using identical arms for mirror teleportation/training.

https://github.com/TheRobotStudio/SO-ARM100

[nullc]

4 is still though fundamentally limited: you need a minimum six DOF to position all three translational and rotational freedoms. The human arm has 7, and I think a case can be made the smart software would reduce the problems from having only exactly as many as required. ... but not eliminate: the extra degree of freedom lets you "get out of your own way" when moving objects that are not zero size trough multiple positions :)

Perhaps 4 is enough for any specific application, but then again perhaps 3 is or 2. :P

I've never programmed a robot arm, but I've spent a fair amount of time using a seven axis faro arm (a coordinate measuring device, sort of the opposite of a robot arm) and it certainly takes some practice to avoid "cant move there from here without reorienting everything", it's easy to take for granted what our brains do automatically for us. :)

[IanCal]

Humans have 7 dof but we can't get into all positions, as I've found clearly today trying to reach things for my kids in the back seat of the car.

[numpad0]

in simpler term: an object has position and rotation, and we're in 3D, so we need minimum 6 linearly independent parameters to be able to both point at a direction and be at a location at the same time.

Drone and helicopters has 4, and they are able to control max 4 of 6 parameters. Usually 3 positional + 1 rotational, and the rotatinal axis go first.

[numba888]

It uses cheap hobby servos which is, to put it mildly, not the same as steppers. You will never get 0.2mm precision with them. They will were out quickly and even quicker under load.

BTW, looks like it doesn't have closed loop control. "0.2mm repetability" (should be repeAtability) is only 'under certain conditions', no load.

[easygenes]

You'd be surprised what you can do with servos modified with encoders, setup with an industrial grade cascading control loop. First demo video below demonstrates threading a mechanical pencil lead in and out through the writing tip. Second video demonstrates a 187gram weight at the end of a 470mm long rod. Third video shows that the modification is now a quick fitting of some 3D printed parts to the servo motor axle and servo housing.

  https://www.youtube.com/watch?v=ECLrLupFW10
  https://www.youtube.com/watch?v=_4mrb2T706s
  https://www.youtube.com/watch?v=Ctb4s6fqnqo
  https://github.com/adamb314/ServoProject

[moffkalast]

It has closed loop control, these [0] are a bit more proper serial servos with digital absolute magnetic encoders. Each one can be sent positional, velocity and even acceleration targets. I doubt anyone is looking for 0.2mm precision for $300 total. Or even 1mm precision.

The PAROL6 BOM doesn't provide any cost estimate, but it looks quite a bit more expensive.

[0] https://www.waveshare.com/wiki/ST3215_Servo

[dheera]

I really never understood why hobby servos are so shitty. Their protocol uses only a very narrow range of PWM values and not the full 0-100% scale and that alone completely wrecks their precision beyond what their motors can achieve.

Also they do measure position to achieve their feedback, might as well just output that on a 4th wire.

[brcmthrowaway]

These look a bit better than $1 SG90s..

[thoweirjwoj234]

(AliExpress sells 6/7-dof arms made with hobby-servos & metal construction, shipped for $50).

[brcmthrowaway]

Can this actually do programmed movements ? It seems it learns through a camera only.

[maujim]

its actually 250 for both, 130 for just the leader