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[Paparazzi-devel] Tuning Suggestions Part II

From: TurboTas
Subject: [Paparazzi-devel] Tuning Suggestions Part II
Date: Sun, 1 Feb 2009 03:51:08 -0800 (PST)

Hi All,

I posted a couple of weeks ago about a tuning problem I was having.  To refresh 
your memories, my funjet plunges groundward every time I try AUTO1.

I have made some progress but would be great for one of you techies to validate 
my steps! 

What I did was to use the Log plotter and go through all the available 
variables plot by plot to see if I could see anything odd.

I think I found something which may be the culprit, but I don't know how to fix 
it - or even if my diagnosis is valid.

My airframe is a Funjet and I have a pretty standard setup: Horiz and Vertical 
IR sensor, Roll Gyro, Xbee etc.

For the Roll Gyro, I use the ADXRS 150 and have both the Temp and Rate 
connected, so I have a ADC section like this:

  <section name="adc" prefix="ADC_CHANNEL_">

    <define name="IR1" value="ADC_1"/>

    <define name="IR2" value="ADC_2"/>

    <define name="IR_TOP" value="ADC_0"/>

    <define name="IR_NB_SAMPLES"        value="16"/>

    <define name="GYRO_ROLL" value="ADC_5"/>

    <define name="GYRO_TEMP" value="ADC_6"/>

    <define name="GYRO_NB_SAMPLES"      value="16"/> 


Look good? 
Then I hve a Gyro Section which looks like this:

  <section name="GYRO" prefix="GYRO_">

    <define name="ADC_ROLL_COEFF" value="1"/>

    <define name="ADC_ROLL_NEUTRAL" value="495.464"/>

    <define name="ADC_TEMP_NEUTRAL" value="476"/>   

    <define name="ADC_TEMP_SLOPE" value="0"/>

    <define name="DYNAMIC_RANGE" value="150" unit="deg/s"/>

    <define name="ADXRS150_RESISTOR_BRIDGE" value="(3.3/(3.3+1.8))"/>

    <define name="ADXRS150_SENSITIVITY" value="5" unit="mV/(deg/s)"/>

    <define name="ROLL_SCALE" 

    <define name="ROLL_DIRECTION" value="1."/> 


Okay, to me this looks correct but I get an odd result in the Log plotter.  In 
the Plotter under the Gyro _Rates Section, I only get three variables: Pitch, 
Roll & Roll_ADC.

If I plot these in the log plotter, I get pretty much what I expect from the 
ROLL and ROLL_ADC.  Good numbers that tie up with the flight.

However, If I plot the PITCH param, I would expect to get nothing as I don't 
have a pitch Gyro, But what I actually get is a number that starts off around 
25 for the few minutes before flight.  After takeoff, the number gradually 
drops to about 5.  After landing, the value gradually starts to climb agian.

My guess is that I'm seeing the gyro temperature in the PITCH position on the 

The obvious question is therefore: Does this mean that the AP is seeing the 
temp as pitch as this may explain the lack of pitch controll?

Any comments would be great!


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