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Re: [Paparazzi-devel] simultaneously using two autopilot systems for rel

From: Chris Gough
Subject: Re: [Paparazzi-devel] simultaneously using two autopilot systems for reliability
Date: Wed, 27 Mar 2013 11:55:17 +1100

Hi Refik

In my opinion it's difficult to make a the system more reliable by
adding complexity. If you have an additional component choosing which
autopilot should be in control, that device has to be more reliable
than the autopilots otherwise the system will be less reliable than a
single autopilot. The autopilots are very reliable, so it's a hard

In the Outback Challenge competition we were required to have an
independent failsafe device. Initially developed a "failsafe/mux"
device that with a "failover feature", it would try falling back to
the a spare autopilot before triggering a failsafe (deliberate crash).
We abandoned that because we felt it was less secure than having a
simpler failsafe and a single autopilot. To many wires, an immature
component on the critical failure path, more complexity than
absolutely necessary. I'm not convinced the failsafe made the system
any more secure either, but it was necessary because of the rules of
the competition.

Redundant communication links do make sense if link reliability is
important in your application. Any given link can fail for a number of
reasons, spatial and spatial diversity of multiple links probably adds
more than the additional networking component takes away.

For redundant GPS', I suppose the information is there to chose "the
best of many" one but my guess is that the benefit would be marginal
compared to single, well installed GPS (good location, good cable

I don't know about redundant IMUs.

Split control surfaces (redundant servos) are a common precaution on
larger airframes.

Chris Gough

On Tue, Mar 26, 2013 at 7:21 PM, refik <address@hidden> wrote:
> Hello,
> In paparazzi, is it possible to use two complete autopilot systems for
> reliability ? (each system includes GPS, imu, transmitter and autopilot, if
> one of the systems is gone, the system automatically switches to other).
> If it is not possible currently, I think that it will be a good choice to
> implement.
> We will try to fly an aircraft for 24 hours within 20km, therefore we will
> need a reliable autopilot. What configuration (autopilot, imu, Gps and
> modem) do you suggest to use?
> Cheers,
> Refik
> _______________________________________________
> Paparazzi-devel mailing list
> address@hidden


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