Month: April 2011

Paper Chuckranoplan!

chorl1 Comment

I officially renounce any claim I might ever have possessed to being an engineer.

I just straight give up. There’s no point in continuing.

…because look at this thing!! Isn’t it SOO CUUUTE? And adorable and foamcore-y and completely undesigned and unplanned and made in 20 minutes while I was supposed to be tutoring 2.007?

And it works exactly like it should. Of course it does… I didn’t think about it too hard beforehand.

Anyways, meet Chuckranoplan 0004FML, where the FML is for for “foamcore, medium length”, I swear. 0004FML is about 30″ long and made from 5.5-6mm foamcore, the kind you put bad science fair posters on.  With the Nut of CoG Shifting, it weighs a bit under one pound. The wingspan is roughly 18″ (just one entire foamcore sheet), and the little winglets take it to about 30″ wide.

Here’s the planform overall. This was certainly the quickest build I’ve ever pulled off. There was a little bit of precognition here, since Shane and I have been meaning to just pick up a pile of foamcore and go for it, since there’s a large supply for the 2.007 class. The joinery was with pretty standard hot glue, and there’s no other materials used in construction, excluding the nut of course.

Here’s a front lower view showing the air pocket space under the wing and the orientation of the tail.

While it did work somewhat at first, only after adding the dihedral winglets did it actually achieve meaningful roll and lateral stability. So it seems that these little winglets do play a pretty significant role in the dynamics of the vehicle after all. And it does make sense – the winglets contribute to the stabilizing dihedral effect while the main wings provide most of the lift. The technique is known already to GEV designers and is called a “composite” wing.

0004FML will not get any flight electronics, but it was a good geometry study for 0004 proper. And it looks like I’ll definitely be considering those winglets more seriously.

Here’s some shove testing video!

Doesn’t that work so awesome!?

A Few Words on “The Segfault”

chorl2 Comments

Okay Make, I have an axe to pick and a bone to grind with you guys.

My experiences with Make Magazine and the affiliated blog have been extremely positive in the past. Everything from LOLrioKart to a certain 3D printer to even Fankart has been on the blog so far, and MITERS generally has contacts with people pretty closely associated with Make anyway, so just about everything we do ends up on there. But I have some pretty big reservations about the description of Segfault up there, in this month’s Make (volume 26). Basically the story is a few months ago I was contacted by a journalist for a quick interview about Segfault’s construction, which I obliged to. Now, I don’t blame John up there at all – I know that the guy knows his shit, and he’s in fact the person who puts alot of our stuff on the blog. So I think in this case, he was only reporting on information relayed to him. And boy was that faulty – so since the given address seems to link directly back to this site, I might as well open the valve a little, so to speak.

In a nutshell, those are all the fine little details that nobody cares about being treated as headline news. It has 9 inch scooter wheels!!! And GEARMOTORS!!! No, I’m not just bitter because the gyro and accelerometer functional description is wrong and I’m not sure how it was distilled from the description I gave it. No, what I’m really peeved about is the fact that

Segfault is analog.

That was like, the entire point, man.  Fact #1 about Segfault is always that it’s analog. Not a single line of code runs to keep the vehicle stabilized. Your segway runs on 14 lines of code, mine runs on op amps. Real op amps.  FOUR HUNDRED OP AMPS.

Okay, so more like 11. I think they’re starting to wear out and their gains need replacing soon, but OP AMPS!!!

The signal processing occurs in continuous time.

Instead of waterjetted aluminum chassis (which is nice and all), that line should read ANALOG!!!! I’m not particularly proud of the fact that it uses rudimentary and rather obsolete technology to accomplish the task, but the fact that it was one hell of a control theory learning experience, especially since the final build really occured over like 48 hours. Porting a transfer function to op amps!!!!! is about the closest you can get to just double-fisting the raw theory.

It doesn’t have an Arduino.

Or an ATMEGA chip, or a MSP, or a Cortex. Or anything for that matter. I guess the twin Class D switching amplifiers running the motors are kind of digital.

It also doesn’t work like that.

I’m not sure where the “gyroscope prevents the accelerometer from overcorrecting” bit came from, but it’s way more like the gyro and accelerometer complementing eachother and working in synchrony. In fact that’s so true that it’s even called a complementary filter. It’s a very common and simple sensor fusion algorithm, and if you actually want to know what one is, Segfault’s second most recent build post goes over why I use the two sensors this way in the Adaptive Face Forward Compensator.

Okay, that’s enough for now. Ya’ll should go build Segsticks. Maybe I should start writing for Make or something, eh?!