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Stanford Pupper: low-cost quadruped robot

stanfordstudentrobotics.org

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Re: Stanford Pupper: low-cost quadruped robot

#51

Post by canada_dry »

NathanKau wrote: post #41

Hey all, my group in Stanford Student Robotics made Pupper. Happy to answer any questions!

Awesome project! I'd love to build one, except for sourcing the parts - esp. the carbon fibre (out-of-stock) bits! If your team sold it as a kit I'd be your first customer! Of course, you'd have to ship to Canada too.

Q. Was there a price point you had to aim for in the development (i.e. under $1K)? And, if you were to double the price, what improvements would you make (e.g. even better servos)?

Re: Stanford Pupper: low-cost quadruped robot

#52

Post by detaro »

softwarejosh wrote: post #45
n0us wrote: post #8

> You can buy most of the parts directly from a reseller like Amazon or McMaster-Carr, but for some you’ll need to get them custom manufactured for you. The custom parts include the carbon fiber routed parts, the 3D printed parts, the power distribution printed circuit board, and the motors. Very cool and I would like to build this, but the "Nano Dog" is probably a cheaper and more approachable option for the garage…

the parts list for the puppet is a joke everything is overkill for no reason you could easily do it for 200 same size and function

Now we're curious about what part replacements you'd suggest.

Re: Stanford Pupper: low-cost quadruped robot

#53

Post by e-_pusher »

NathanKau wrote: post #41

Hey all, my group in Stanford Student Robotics made Pupper. Happy to answer any questions!

Awesome project Nathan, kudos to the team. I'd love to use the Stanford Pupper at some point for K-12 outreach efforts myself.

I reviewed your power distribution board. I think it needs more safety features before it can safely be entrusted to the hands of K-12 kids. Couple of comments:

- The battery input is unfused. I would HIGHLY recommend adding one.

- I know you guys wrote in Github about how people should not plug in voltages above 8.4V, and not overdischarge batteries, but I would not trust K-12 kids to follow those instructions :)

It would be best to add a overvoltage, overcurrent and reverse polarity protection circuits. Those are pretty simple and should not take much space on the board. Jerri Ellisworth has a great video where she explains these circuits in detail, and how to make them low-cost: https://www.youtube.com/watch?v=QZ0WXQWND-I

- I would add a schmitt trigger circuit to sense the battery voltage and feed that as a digital input to the Raspberry Pi. If the batteries are too low, the Pi then can throw an audible alarm and disable the servos. This would prevent kids from overdischarging their batteries.

As a future addition, I think it would be sweet to add a Teensy somewhere. Then students would be able to easily add extra sensors and have their robot respond to changes in the environment etc. So much potential for fun.

Congrats again!

Re: Stanford Pupper: low-cost quadruped robot

#55

Post by Animats »

It's fun seeing these. As batteries and motors get better, they get more agile.

I'm disappointed that there's no force feedback. They're still using dumb PWM servos, which is a 1970s technology. There are better servos, from Dynamixel, where you get info back. There was a project called OpenServo [1] to smarten up dumb servos by developing tiny new controller boards for cheap RC servos. But that project seems to be defunct.

There are lots of good legged toy robots in the $300-$400 range, but without good feedback you can't do Boston Dynamics type stuff.

[1] https://hackaday.io/project/158267-openservo-20

Re: Stanford Pupper: low-cost quadruped robot

#56

Post by ebg13 »

isalhi wrote: post #54

Gotta say, really comforting that this was written in python. Everyone I talked to when it comes to quadrapeds tells me python is too slow for my projects.

People always imagine that mobile robotics needs nanosecond response times or some other silliness when the reality is that your sensors and servos only operate on the order of 100Hz.

Re: Stanford Pupper: low-cost quadruped robot

#58

Post by NathanKau »

Animats wrote: post #55

It's fun seeing these. As batteries and motors get better, they get more agile. I'm disappointed that there's no force feedback. They're still using dumb PWM servos, which is a 1970s technology. There are better servos, from Dynamixel, where you get info back. There was a project called OpenServo [1] to smarten up dumb servos by developing tiny new controller boards for cheap RC servos. But that project seems to be d…

We've found you can actually do a lot with dumb servos and orientation feedback and get visually similar results to Spot. For instance, we get hopping, trotting, strafing, turning + strafing, walking. What it can't do is prancing or a flying trot. But we think it's totally worth it since a good-enough servo is around $20, while similarly sized torque-controllable servo (excluding dynamixels, which don't actually have torque control), runs about $400 each. DJI did actually come out recently with their M3508 and M2006 which we're starting to play with, and we think we can build a torque-controllable pupper for about $1.5k.

The main limitation I think for servo robots with kinematic (position-control) controllers is speed. We're moving around 0.8m/s max, while the new Unitree A1 is something like 3.5m/s.

Re: Stanford Pupper: low-cost quadruped robot

#60

Post by NathanKau »

e-_pusher wrote: post #53
NathanKau wrote: post #41

Hey all, my group in Stanford Student Robotics made Pupper. Happy to answer any questions!

Awesome project Nathan, kudos to the team. I'd love to use the Stanford Pupper at some point for K-12 outreach efforts myself. I reviewed your power distribution board. I think it needs more safety features before it can safely be entrusted to the hands of K-12 kids. Couple of comments: - The battery input is unfused. I would HIGHLY recommend adding one. - I know you guys wrote in Github about how people should not p…

Great feedback! Will definitely incorporate those features into future revisions.
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