[Top][All Lists]

[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]

[Paparazzi-devel] Re: Paparazzi-devel Digest, Vol 33, Issue 1

From: Filipe Varela
Subject: [Paparazzi-devel] Re: Paparazzi-devel Digest, Vol 33, Issue 1
Date: Wed, 27 Dec 2006 17:11:31 +0000


So I'm putting together a shopping list for a helicopter autopilot based on,,
<> and anecdotal information on the
internet.  Sorry but can't find any implementation notes on

Hovering a helicopter seems to require a 3-axis accelerometer and a
2-axis gyroscope. claims they hovered a
helicopter on just this information.

Consider a 6DOF unit (3 axis accels + 3 axis gyros)

One problem isn't being addressed anywhere:  How do the autopilots
for the drift in the gyroscopes?  Do the accelerometers compensate for
it?  Do they need a GPS
to reset periodically? Do they just have a time limit before requiring
pilot intervention?

Drift is addressed with a kalman filter. It's a technique whereby you take a highly-realiable angle estimate created from accelerometers (which is only realiable on the long run, as they don't update frequently and suffer interference from linear accelerations) to "periodically" reset the body frame state to a point where you can trust gyros again.

Say a gyro becomes inacurate after 3 seconds. If you feed the accelerometer based attitude estimate to the filter every second, your gyros will never become inacurate. They'll be the "only" reference you will use between the slower accelerometer estimates.

Mind the "". There are many parameters that can be tuned in such a filter. What i wrote is a high-level approach with some inacuracies. The purpose is to explain the process, not the actual details.

I suggest you do some googling for complementary filters, kalman filtering and study some linear algebra before attempting/spending money on such a project, or go for integration only and buy paparazzi hardware for your model.

These projects can become pretty expensive and you won't want to regret starting one after spending 1000+ EUR/USD would you?

Good luck,

reply via email to

[Prev in Thread] Current Thread [Next in Thread]