Hacker News Reader

Comment by n0us | Hacker News Reader

> 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 engineer.

https://www.thingiverse.com/thing:3145690

View on HN

> the "Nano Dog" is probably a cheaper and more approachable option for the garage engineer.

Hard to find out much about that or OpenDog in general. I've found videos and 3d printer files but nothing that I can read to understand what it can do and why I might want to build it.

Or do I really have to watch a bunch of YouTube videos? I hate video.

Have I missed the actual project page somehow?

Good point, now that I am searching for it I cannot seem to find the code. At the same time it still does not require custom manufactured parts or circuit boards which makes the barrier to entry (and importantly price) a bit lower unless the Stanford folks setup a store.

I make an internet promise here and now that if I ever build the robot I'll open source the source code to control it.

https://github.com/XRobots/miniDogV2

The code's a bit of a mess -- James is clearly not a software engineer first. This is totally understandable, given that he does so many other things!

When I first saw the code, I thought about doing a refactoring pass and making a pull request. It would be painful to test correctness without the hardware, and I don't want to make things worse, so I haven't.

Oh wow, you're not joking. I'm getting flashbacks to when I supported a team of EEs.

Hell, I'm getting flashbacks to my own code in EE lab. Except this stuff looks way less messy, not nearly enough random assembly declarations to bludgeon a register or pin into submission.

For future reference, I saw "OpenDog" and thought we were discussing James Bruton's (XRobots) OpenDog/Mini-Dog, which is where the firmware I linked above comes from.

NanoDog is something different, apparently! Sorry for any confusion I might've caused there.

It's probably also worth mentioning the project is a work in progress, and from the videos, it looks like OpenDog is likely to undergo at least one more major change before "completion".

brb building automatic testing environment with dog physics simulation

As someone who also isn't a SWE first, what are the changes you'd make and where can one learn to code in a more SWE way?

For carbon fiber parts (used for the chassis and legs), I wonder if it is possible to carve them out out from the same power distribution PCB board. Some PCB manufacture seems to support custom shapes.

But the PCB material must be heavier than carbon fiber, not sure if it will affect the robot dynamics.

Just for fun I uploaded the top and bottom body panel DXFs to jlcpcb and they're only about $2 each. That's compared to about $30 to have them cut out of carbon fiber, and of course you don't get to put circuity like your power distribution on it for free.

I wasn't able to find any examples of this quadruped walking.

I'd be amazed if you found any doing a dynamic gait with closed loop control. One problem with making legged robots smaller is that you drastically increase the reaction speed required for any kind of closed loop control.

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

I've built several servo powered walking robots. Torque is a major concern, and obviously weight plays a part in how much torque is required. The recommended servos look to be $30 each, x12 means $360. If you spent $200 just on servos you'd have to settle for $16 servos. Probably less torque. That would mean that at full leg extension the robot might not be able to support itself. That would be an annoyance when trying to focus on walking algorithm development, which is usually the fun part for these small walkers.

You can definitely do something for cheaper, but I wouldn't call this a joke. When I was 15 (20 years ago lol) I designed an 18 servo hexapod. I saved up $350 from cleaning horse stalls and my dad agreed to pay the other half, and I spent $700 on servos. It was great to learn about inverse kinematics before ever setting foot on a college campus!

> You can definitely do something for cheaper

If the 35kg is in fact needed (which I’m not prepared to debate, probably needed, but I can’t prove / disprove), you are exactly right. Yes, you could maybe save a couple dollars with cheaper servo brands, but honestly for a 35kg servo, you’re going to pay a decent amount for 12 of them.

Yes and I noticed this robot can jump completely off the ground. Pretty nice!

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

Well don't be shy, post some videos of your $200 quadruped showing off its flexible dynamic gait performance.

Reply on news.ycombinator.com