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Low Cost Robot Arm

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Re: Low Cost Robot Arm

#231

Post by euroderf »

Ekaros wrote: post #101
euroderf wrote: post #93

Earlier quoted context omitted.

Drinks mixer! Line up the booze bottles and other stuff. No need for brute strength. Tolerances of one or two millimeters are mostly fine.

This actually sounds to me as bit complicated. As you need to adjust angle for each pour from a bottle. And then there might be different viscosities involved with some bottles...

Angle would benefit from visual recog - shape of bottle top, shape of bottle body.

Viscosities - probably finding a booze's sugar content online would be 90+% of it.

Re: Low Cost Robot Arm

#232

Post by 3seashells »

xg15 wrote: post #207
mtreis86 wrote: post #134

I started working on a similarly sized arm. I've got a use-case, long time friends with a glass blower. I was thinking of using it to make faceted glass pendants. They've got a faceting machine but it is manually operated. The hard part is repeatability. You need tight tolerances and each joint in the arm adds inaccuracy the further you get from the base. If the base has 1mm of wiggle, the 20cm arm has 4mm wiggle at…

> The hard part is repeatability. You need tight tolerances and each joint in the arm adds inaccuracy the further you get from the base. If the base has 1mm of wiggle, the 20cm arm has 4mm wiggle at the end, and the arm beyond it has even more. Could this be solved by software instead of expensive hardware? Some idea I had a while ago was to build an arm out of cheap, "wobbly" components for the large-scale movements…

[dead]

Re: Low Cost Robot Arm

#233

Post by ActorNightly »

tomp wrote: post #227
xg15 wrote: post #207

Earlier quoted context omitted.

> The hard part is repeatability. You need tight tolerances and each joint in the arm adds inaccuracy the further you get from the base. If the base has 1mm of wiggle, the 20cm arm has 4mm wiggle at the end, and the arm beyond it has even more. Could this be solved by software instead of expensive hardware? Some idea I had a while ago was to build an arm out of cheap, "wobbly" components for the large-scale movements…

> Could this be solved by software instead of expensive hardware? Yes. Imagine a human putting a screw in a hole. You don't follow the "optimal" trajectory, you adapt it on the fly, even do several quick trials to do it. Humans do it with a combination of vision, touch and planning. Each of these is currently still a huge problem for AI, nowhere near human level.

Id consider it more a fundamental problem - lack of a way to introduce new data to a model without repeating training runs and waiting for the error to converge. Humans seem to have an understanding of things from a one-shot learning run (this is perhaps due to our vast experience with the world and ability to run simulations in our head, but a subset of that should be possible for ML quite easily)

If you solve this problem, teaching a robot arm to be accurate should be pretty easy. You would just have stereoscopic cameras that map to a 3d world, and "program" in a trajectory of the object, and the model should use that trajectory to figure out where to move and how to compensate based on visual feedback.

Re: Low Cost Robot Arm

#234

Post by sebastiennight »

spxneo wrote: post #217
MaxikCZ wrote: post #17

I want the arm to wander around my house, pick up articles of loose clothing and put them into washing machine. Then pull them out and spread them on a drying hanger. How far away from that are we?

You have to tradeoff between privacy, automation and cost. The scenario you described is tough to solve because of edge cases sort of like FSD. If you want that work done then its cheaper to hire a maid. It would be nice to have complete privacy and have a robot perform all those tasks flawlessly but the price point would make it economical to get a human to do it. Perhaps you can get someone to drive the robot but t…

You're not going to get "complete privacy" (aka fully-offline local-model-driven) robots outside of building one yourself... There'd be just too much of an economic incentive to use this as a data collection platform.

Re: Low Cost Robot Arm

#235

Post by tomp »

ActorNightly wrote: post #233
tomp wrote: post #227

Earlier quoted context omitted.

> Could this be solved by software instead of expensive hardware? Yes. Imagine a human putting a screw in a hole. You don't follow the "optimal" trajectory, you adapt it on the fly, even do several quick trials to do it. Humans do it with a combination of vision, touch and planning. Each of these is currently still a huge problem for AI, nowhere near human level.

Id consider it more a fundamental problem - lack of a way to introduce new data to a model without repeating training runs and waiting for the error to converge. Humans seem to have an understanding of things from a one-shot learning run (this is perhaps due to our vast experience with the world and ability to run simulations in our head, but a subset of that should be possible for ML quite easily) If you solve this…

No, I'm telling you, you're assuming way too much. The problems are lower-level

> stereoscopic cameras that map to a 3d world

The current state of the art for this is completely atrocious.

Take a look at this very recent research: https://makezur.github.io/SuperPrimitive/

The idea that robots can "understand" the 3D world from vision is, right now, completely illusory.

Re: Low Cost Robot Arm

#236

Post by brozaman »

xg15 wrote: post #207
mtreis86 wrote: post #134

I started working on a similarly sized arm. I've got a use-case, long time friends with a glass blower. I was thinking of using it to make faceted glass pendants. They've got a faceting machine but it is manually operated. The hard part is repeatability. You need tight tolerances and each joint in the arm adds inaccuracy the further you get from the base. If the base has 1mm of wiggle, the 20cm arm has 4mm wiggle at…

> The hard part is repeatability. You need tight tolerances and each joint in the arm adds inaccuracy the further you get from the base. If the base has 1mm of wiggle, the 20cm arm has 4mm wiggle at the end, and the arm beyond it has even more. Could this be solved by software instead of expensive hardware? Some idea I had a while ago was to build an arm out of cheap, "wobbly" components for the large-scale movements…

I'm a software engineer myself so I don't know a lot about this, but there are a few patterns that are not far off of what you're describing. For instance:

https://en.wikipedia.org/wiki/Input_shaping https://en.wikipedia.org/wiki/Proportional%E2%80%93integral%...

Re: Low Cost Robot Arm

#237

Post by mglz »

adolph wrote: post #166
mglz wrote: post #152

Earlier quoted context omitted.

Servo + Cycloidal or Harmonic gears are usually the way to go, but to get them backlash-free is hard (or expensive, if you're buying). Once you got that down challenges include: * How rigid are the links between my joints? Plastic will wobble, metal is better * How heavy is my arm and how does that limit its movement? If you go for stiff metal castings, you add weight you need to move. The lever arm relative to the b…

Do you think there is a way to take out backlash with sensors and software? Something like how additive manufacturing systems can use accelerometers to smooth artifacts from motor movement. [0] Let's say two cheaper cycloidal geared motors running in opposition with a load cell between them to maintain the materially compatible force. https://www.klipper3d.org/Measuring_Resonances.html

I don't want to say no, however it seems very hard to do. You get feedback about motor position via an encoder, which is usually located on the motors axis and not the output element. Since the motor axis spins a lot more, you get more resolution. Backlash happens on the output, so you could add a second encoder there (but now you've got more complexity + cost). An oldschool CNC solution is to add brakes to lock an axis out, but this makes your system less flexible and doesn't prevent backlash during motion. A more modern solution might be to factor backlash in to your motion software so that you tell the kinematic solver what compliance is acceptable in some direction.

> Let's say two cheaper cycloidal geared motors running in opposition with a load cell between them to maintain the materially compatible force.

This might work, but now you have twice the amount of motors.

Re: Low Cost Robot Arm

#238

Post by otikik »

boffinAudio wrote: post #83
otikik wrote: post #56

Earlier quoted context omitted.

Oh look someone has already done something like that: https://www.youtube.com/watch?v=04JkdHEX3Yk

I don't know why this can't just be a cleverly laid out arrangement of layered sieves, each one parsing a different object .. I don't see how it needs to be mechanical in any sense other than "pour in the lego junk, out it comes neatly sorted", a la coin-sorting machines ..

It is probably possible to do it, but the sieves would be quite big, just to account for the very large number of pieces, as well as having to “orientate” them correctly using only gravity.

Re: Low Cost Robot Arm

#239

Post by app13 »

GabeIsko wrote: post #197
Climato wrote: post #187

Earlier quoted context omitted.

I think about this regularly just don't have the time to pursue it: Couldn't you build your arm in Nvidia Omniverse by also adding feedback like a cheap hig resolution distance or angle detector and train an ml model to compensate it?

Making and animating a 3D graphics robot arm is trivial compared to building it in real life. So not so much Omniverse, you would want to use a proper simulator like gazebo. But beyond that, the kinematics as well as the force dynamics for controlling a serial manipulator are very well understood. So there aren't too many gains to be made by AI. It is difficult to implement in software due to some tricky situations a…

Omniverse is a simulation platform specifically designed to do things like train/test robotics. It's not a creative engine like UE or Unity.

Re: Low Cost Robot Arm

#240

Post by jononor »

mtreis86 wrote: post #134

I started working on a similarly sized arm. I've got a use-case, long time friends with a glass blower. I was thinking of using it to make faceted glass pendants. They've got a faceting machine but it is manually operated. The hard part is repeatability. You need tight tolerances and each joint in the arm adds inaccuracy the further you get from the base. If the base has 1mm of wiggle, the 20cm arm has 4mm wiggle at…

What kind of manipulation is needed? If a 3 axis or 4d axis system can do the job, that is always much cheaper than a robot arm, for a given precision and load capacity.
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