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Low Cost Robot Arm

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Re: Low Cost Robot Arm

#151

Post by rini17 »

deelly wrote: post #111
rini17 wrote: post #98

Why not start with something less ambitious, like low cost robot platform able to follow people and carry stuff around and avoid obstacles. No arms, I am okay using mine to put stuff on and off it. When I had leg injury and used crutches, carrying stuff around suddenly became a problem. There are many people with impaired movement. And even without that, I often misplace things and it could help there. There are plen…

> low cost robot platform able to follow people and carry stuff around and avoid obstacles. So, basically autonomous self-driving mini vehicle. Сompanies spend billions on self-driving cars with quite limited luck.

No, rather a larger version of robotic vacuum.

Re: Low Cost Robot Arm

#152

Post by mglz »

flutas wrote: post #148
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…

Uneducated in hardware, mostly a software guy for perspective, so I could be way off. Would using something like a stepper motor geared way down with a cycloidal gear box work for a situation like this? (in my mind) It would give you a very controllable and repeatable way to position, with the backlash handled by the gearbox mainly. Would love to know if I'm wrong though, like I said mostly a software guy trying to v…

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 base can get really long

* Motors are heavy! Ideally you can mount them towards the base, but then you need drive shafts or belts, which again add flex. (See KUKA arms which have motors 4, 5 and 6 on the elbow often)

* How much payload do you need to move? 5kg is already challenging in ~1m arms and if you need to move it fast the problem gets even bigger.

* Where do you run your cables? Internal is tricky to build, external can get you tangled.

And so on. When approaching this you get a totally new appreciation for biological arms which arae insane in most aspects except for repeatability. And on the software side you can enjoy inverse kinematics :)

Re: Low Cost Robot Arm

#153

Post by mglz »

7373737373 wrote: post #69

I'm surprised (or perhaps very unaware) that there doesn't seem to exist a company yet that mass produces cheap, high quality, reasonably standardized robot arms. So many things like 3D printers or CNC machines have entered the consumer/amateur level price realm, but this seems to be something still largely unexplored. Seems to have Arduino/Raspberry Pi scale potential, but I haven't heard of a name/ecosystem that po…

They do, but cheap is ~10.000€ currently for a general-purpose bot with 1.2m reach. You get a high quality machine and software for that. Note that a robot without really good kinematics software is borderline unusable. Also, besides the arm you need the control box which reliably delivers power and commands in real-time. That adds quite a bit of cost too.

Re: Low Cost Robot Arm

#154

Post by leoedin »

7373737373 wrote: post #69

I'm surprised (or perhaps very unaware) that there doesn't seem to exist a company yet that mass produces cheap, high quality, reasonably standardized robot arms. So many things like 3D printers or CNC machines have entered the consumer/amateur level price realm, but this seems to be something still largely unexplored. Seems to have Arduino/Raspberry Pi scale potential, but I haven't heard of a name/ecosystem that po…

I worked for a startup developing robot arms for a while. What we found was that giving someone a robot arm - even one with reasonable APIs and no cost to them - didn't really help because the hard part is making useful automations. Mostly people spent a few hours playing with the arm and then put it on a shelf.

Every use case is completely different and is a lot of work. Even when you get something working, accidentally shake the desk or crash the arm into something and all your coordinates are broken and you have to start again.

Not to mention the actual mechanics are really complicated - to have a meaningful payload at 50cm reach you end up with really high torque at the base joints (which also need to have super-high accuracy), which requires expensive gears and motors. None of that is cheap.

Then you get to safety - an arm that has a useful payload is also quite heavy, and having that amount of mass flailing around requires safety systems - which don't come cheap.

It's a bit like hardware no-code - you can't make an easy to use robotic arm because programming it is inherently hard. I think the only thing that will change that is really good AI.

Re: Low Cost Robot Arm

#155

Post by 4gotunameagain »

greggsy wrote: post #127
michaelt wrote: post #81

Earlier quoted context omitted.

> Seems trivial Said like someone who's never tried it :) For a start you're going to need a camera. Maybe more than one. You want depth sensing? Even an cheap choice like a RealSense is going to add another $250 to your costs. And you'll need a sturdy mount for it, the robot's going to vibrate the table and you don't want to suffer motion blur. Got the camera in a fixed location, over the area you're picking from? T…

It’s trivial to fork one of the several open source projects focused on this problem.

For example ?

[1] lists [2] which uses a robotic arm, but it is closed source

[1] https://github.com/360er0/awesome-lego-machine-learning [2] https://www.thirdarmrobotics.com/q_and_a.html

Re: Low Cost Robot Arm

#156

Post by ectopasm83 »

RecycledEle wrote: post #103
7373737373 wrote: post #69

I'm surprised (or perhaps very unaware) that there doesn't seem to exist a company yet that mass produces cheap, high quality, reasonably standardized robot arms. So many things like 3D printers or CNC machines have entered the consumer/amateur level price realm, but this seems to be something still largely unexplored. Seems to have Arduino/Raspberry Pi scale potential, but I haven't heard of a name/ecosystem that po…

There is a reason there is no standard hobbyist-grade robotic arm. People think they can build their own robotic arms for leas than a "real" robotic arm costs, but the do not account for wobble or repeatability. With all due respect to the person who posted a design for a robotic arm made with RC servos on HN, I would like measurements of the repeatability. Have it draw the same pattern on a piece of paper every day…

https://github.com/adamb314/ServoProject

^Modifying cheap servos so that a robot arm can repeatedly insert a pencil lead. It's a lot of work though.

Most interesting application though fall out of the scope of old-fashioned robotic arms, i.e. when you need to sense the real world in a non controlled context. For instance to develop a robot that can trim wilted flowers, you'll need to measure the real world, and as soon as you do that, you can just sense your robot arm too, no need for fancy, ultra-precise actuators.

Look at this BOM: https://docs.google.com/document/d/1_3yhWjodSNNYlpxkRCPIlvIA...

Do you really need the $6,129.95 & $3,549.95 robot arms for the kind of application described ? I doubt it. I'm not a robotician, and would love some feeback on this idea.

Re: Low Cost Robot Arm

#157

Post by flutas »

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 ..

I could see people wanting to add on color detection for the bricks, but even that could still be solved by camera + servos/steppers and a chute that goes to different bins. No need for an arm.

Doesn't stop me from wanting one though.

Re: Low Cost Robot Arm

#158

Post by nerdjon »

I have zero idea what I am going to use this for, but the idea of having a robot arm has fascinated me since I was a kid and I am 100% going to start working on this this weekend.

I think I could find some fun projects. I wonder if it could hold my microphone and it turn into an automatic microphone arm...

Re: Low Cost Robot Arm

#159

Post by zafka »

leoedin wrote: post #154
7373737373 wrote: post #69

I'm surprised (or perhaps very unaware) that there doesn't seem to exist a company yet that mass produces cheap, high quality, reasonably standardized robot arms. So many things like 3D printers or CNC machines have entered the consumer/amateur level price realm, but this seems to be something still largely unexplored. Seems to have Arduino/Raspberry Pi scale potential, but I haven't heard of a name/ecosystem that po…

I worked for a startup developing robot arms for a while. What we found was that giving someone a robot arm - even one with reasonable APIs and no cost to them - didn't really help because the hard part is making useful automations. Mostly people spent a few hours playing with the arm and then put it on a shelf. Every use case is completely different and is a lot of work. Even when you get something working, accident…

In Robotic assisted surgery, Tracking targets are mounted on the robot arm and an infrared camera tracks the exact position.

Re: Low Cost Robot Arm

#160

Post by kaibee »

CakeEngine wrote: post #122
RecycledEle wrote: post #103

Earlier quoted context omitted.

There is a reason there is no standard hobbyist-grade robotic arm. People think they can build their own robotic arms for leas than a "real" robotic arm costs, but the do not account for wobble or repeatability. With all due respect to the person who posted a design for a robotic arm made with RC servos on HN, I would like measurements of the repeatability. Have it draw the same pattern on a piece of paper every day…

Is this not something that can be addressed with cameras and (maybe) learnt approaches now? You don't need blind repeatability if you've got good visual monitoring to close the control loop, you just (just!) need good accuracy and low latency from video to motor control.

Why not just throw a SteamVR/Vive laser tracker onto the end of the arm and use that to close the loop? They claim sub-mm precision at room-sized distances, so it should be even better if you had it basically mounted on the base. If you wanted to get fancier you could build it into the end effector w/ one of these? https://tundra-labs.com/products/tl448k6d-vr-system-in-packa...
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