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Re: [Paparazzi-devel] Changing the main loop frequency on the Tiny

From: Prof. Dr.-Ing. Heinrich Warmers
Subject: Re: [Paparazzi-devel] Changing the main loop frequency on the Tiny
Date: Mon, 15 Aug 2011 21:57:14 +0200
User-agent: Mozilla/5.0 (Windows; U; Windows NT 5.0; de-DE; rv:1.4) Gecko/20030619 Netscape/7.1 (ax)

Hi Andreas,
i found just an error in my last mail.
The rate has to be set 8 times for the largest time constant in the loop.
The phase error by the DDC is then lower 10° .


Felix Ruess schrieb:
Hi Andreas,

Of course you can... just depending on what you use you might need to
code a bit ;-)
I assume you are using an imu that you can read with a higher rate?
Which one? As a subsystem or module?

For fixedwings you can set the rates of reading imu, propagation and updates:
   <configure name="PERIODIC_FREQUENCY" value="120"/> <!-- IMU FREQ -->
   <configure name="AHRS_PROPAGATE_FREQUENCY" value="120"/>
   <configure name="AHRS_CORRECT_FREQUENCY" value="60"/>
Then you can <define name="AHRS_TRIGGERED_ATTITUDE_LOOP"/> to trigger
the control loops when a new attitude was computed.
I just commited a small fix to the dev branch:
- update the fw_estimator not only after a correction, but after
propagation as well (if correction is running at a lower rate)
- if you use AHRS_TRIGGERED_ATTITUDE_LOOP way it only is triggered if
you actually have a new attitude estimate and not every time you get a
gyro callback.

This is all not especially nice, we should be able to set this more
flexibly (and e.g. also select a lower rates for gyros than accels,
So feel free to improve this in main_ap.c

Cheers, Felix

On Mon, Aug 15, 2011 at 1:49 PM, Prof. Dr.-Ing. Heinrich Warmers
<address@hidden> wrote:
Hi Andreas,
i think yes, depending what kind of AHS you use.
If you use the IR and the DCM for normal plane  there is no problem.
The processor load is less then 25 %.
But look to the main time constants.
It is only necessary  to be  about 8 times  faster then the lowest time
constant in your feedback control system.

Andreas Gaeb schrieb:

Hello everybody,

is it possible to increase the main loop frequency on the Tiny 2.11
beyond 60 Hz? The sys_mon module indicates there is still some headroom
in terms of processor load, and my PID experiments would greatly benefit
from a higher frequency.

Best regards,

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