Comment by rikeanimer | Hacker News Reader

Comment by rikeanimer | Hacker News Reader

Did no one notice the balls? Those are there so a set of external cameras [think motion capture] can feed in an absolute, essentially perfect state estimate to the control algorithm. It's probably a run of the mill system from Vicon [company].

Essentially if you're running vicon you can make flying things do things like you could make them do programming them in Blender or similar, subject to the [pretty minimal to the human eye] time constants of the mechanical systems. Brushless speed controllers are pretty fast, servos are as well [but way slower]. The end-to-end control loops we are talking about are in the ballpark of 1khz easy and have been for quite some years.

If they had balls they'd take off the balls ;) Other than that it is essentially CGI in real life ;)

Sorry don't mean to be negative it looks cool guys. Now go make it actually cool.

I ain't got no darn PhD in control theory from some fancy skool er nuthin but my gut tells me for this situation it's the state estimation that actually composes the beavers tail under the wattuh of dis dat der prollem.

> Essentially if you're running vicon you can make flying things do things like you could make them do programming them in Blender or similar

It is not quite that easy though. Yes having an external tracker will give you a reliable, high quality source of position and orientation.

But that does not mean that you can “program them in Blender”. You still need to figure out what kind of trajectories your system can or can’t follow and how to map from position and orientation errors to actuation outputs.

If you can’t control the robot with external tracking then you have no hope of controlling it with internal state estimation, so if you already have the test facilities it makes sense to start with that. That way you are not debuging two crappy subsystems depending on each other and failing spectacularly.

I certainly noticed the marker balls, but...

On a quick glance, they do not mention if they are using the external cameras for the control algorithm or just verifying the results. The QR code-like markers on the gates suggests that there is also some onboard cameras.

The statistics on the measurement errors suggests that they have a ground truth (from external cameras?) which they compare to some other source of measurement.

So I would not draw the conclusion that the tracker balls and external cameras are doing all the heavy lifting here.

> The QR code-like markers on the gates suggests that there is also some onboard cameras.

I would be carefull with conclusions like that. These facilities are usually shared between a lot of different experiments through the years. The presence of QR codes on the gates certainly implies that someone at least once thought they might want to use onboard cameras in some experiment.

Are they used in this project? You can’t really tell by just looking at the presence of the QR code.

Same as I can’t tell if you are hungry or not by observing the presence of an oven in your kitchen.

I'm pretty sure that the "facility" is a gymnasium with cloth on the walls and floor to protect them. And, the hanging gates are rigid pink insulating foam sheets, probably made and hung custom for this project.

> I'm pretty sure that the "facility" is a gymnasium with cloth on the walls and floor to protect them.

Plus the tracking system. Which is the big differentiator of course. And the fact that it is not used for basketball games but to test indoor drones.

What else do you think you need for an indoor drone testing facility?

> And, the hanging gates are rigid pink insulating foam sheets

Yes.

> probably made and hung custom for this project.

No.

Here is an earlier MIT aeroastro project using the same gates from 2021: https://aeroastro.mit.edu/news-impact/system-trains-drones-t...

And this is the point I am making. There are many student studying aeroastro at MIT. Not all of their projects are about small drones but many are. And if the small drone test they want to do fits into this room they seem to prefer it. And if one project makes some gizmo (like those gates) for themselves and it looks usefull they won’t throw it away, but chuck it somewhere for storage and then the future projects, such as this one we are just discussing, reuses them.

Model airplane servos aren't "way slower" than brushless motors (with their propellers). Here's a higher-end servo that moves 60° in 68ms:

https://www.horizonhobby.com/product/a7090-brushless-low-pro...

I doubt a motor-prop pair could significantly change its speed in 68ms.

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