[chbot] UAV I'm in

[Charles Manning]

I too was thinking about the "middle path" using an ARM level micro. That's 
definitely going to get you out of any problems wrt grunt for a control loop.

Since ArduPilot doesn't need much CPU I think an AVR is enough.

Unless you're making multi-layer boards I doubt there's a real benefit in 
12bit ADCs over 10 or even 8.

In some ways I'm cheating in my design because I'm using a high dihedral 
glider wing that is inherently stable and does not have ailerons and does not 
need roll control. That should severely reduce the need for complex control 
too. The only potentially instability should be pitch (ie. putting the plane 
into an uncontrolled dive or stall) and I'm hoping that a 3D accelerometer 
will be enough to figure that all out.

As my first go, I'll be only using accelerometers, no gyro, which should mean 
that  uncle Kalman can stay at home. In theory you can use two or three 
accelerometers placed at different parts of the plane instead of having a 
gyro but I'm hoping I don't have to go that far.

What will be good is to see what different approaches yield.

-- CHarles




On Tuesday 25 August 2009 19:23:19 Michael Hope wrote:
> Hmm.  I'm thinking about going pretty much the opposite way - a
> Rustler UGV with a Nokia N800 running Python and the I/O provided by a
> ET-STM32 Stamp :)
>
> A great thing about the Arduino is that you only need a ATMEGA and a
> serial port and that's about it.  The ET-STM32 is getting close to
> that but with the advantage of 12 bit ADCs and a bunch of UARTs.
>
> The interesting part will be doing the control loop well enough to run
> the truck at full speed.
>
> http://www.traxxas.com/products/electric/rustler3705/trx_rustler3705.htm
> http://en.wikipedia.org/wiki/Nokia_N800
> http://www.futurlec.com/ET-STM32_Stamp.shtml
>
> -- Michael
>
> 2009/8/25 Charles Manning <manningc2 at actrix.gen.nz>:
> > I think it would be different to try different approaches and share
> > ideas.
> >
> > The UAV stuff I'm doing is not Propeller based. While Propeller seems to
> > have some admirable properties for some purposes, I just can't be
> > bothered learning yet another architecture, getting yet another set of
> > tools, etc etc. unless there is a very pressing reason to do so.
> >
> > You don't need much CPU grunt to do a basic UAV and I'm going to use an
> > AVR at first because I know the toolchain, they're very cheap and very
> > easy to use.
> >
> > Most control stuff is quite light in its CPU requirements and a 68HC11
> > (remember them?) is enough to do a two-wheel balancing robot so I figure
> > it is enough to control a UAV flight.
> >
> > If I get to needing something more grunty than that, for some serious
> > software engineering, then I'd probably put in an ARM Linux board. I've
> > recently been working with OMAP based Gumstix which will give you a very
> > powerful Linux board (including 256MB flash and 2456MB ram) in less than
> > 20 grams.
> >
> > I know you could kick of with Ardupilot or similar which will give a
> > whole drop-in autopilot for approx USD150 including GPS
> > (http://diydrones.com/), but I'm interested in doing a fresh project
> > rather than just plugging in an existing project.
>
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