Stabilize trim adjustments in ground preflight test.

[KPack]

I am setting up my second Plane with the UDB4 board.

Ground preflight test.

I have a question. In a static test with plane on the table. I switch from manual to stabilize mode. My aileron controls move slightly between the manual and stabilized flying modes. Is this a problem?

Keith

[Phillip Kocmoud]

Hi Keith,

I suspect you have #define ALTITUDEHOLD_STABILIZED set to AH_FULL or AH_PITCH_ONLY , this is probably to be expected. You UDB is attempting to climb to the HEIGHT_TARGET_MIN.

If not please attach you options.h file so we can help you further.

Phil

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[William Premerlani]

Keith,

A slight movement of ailerons when you switch between manual and stabilized mode during a ground test is normal. There are a couple of possibilities:

1. After power up, the gyro drift compensation still takes a few minutes to completely settle. Part of the reason for that is there is some dependence of gyro offset on temperature, and the UDB4 warms slightly. Also, we have seen that some of the gyros take longer to stabilize than others.

2. Possibly you have changed the orientation slightly.

3. Perhaps your ROLL_KP gain is a bit on the high side.

If you want to explore further, do the following:

1. Power up. Make sure that your plane is motionless for 10 seconds prior to the first wag.

2. After initialization is complete, switch between manual and stabilize and observe aileron deflection.

3. Repeat step 2 once every minute for 5 minutes.

If there is a little bit of gyro drift, you will see the amount of aileron deflection reduce with time, as the

drift compensation controller adjusts for it.

Best regards,

Bill

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[William Premerlani]

Phil,

My guess is that what Phil is seeing is related to the explanation I gave the same time you were writing your response.

Regarding altitude controls, that would impact the elevator deflection, not the ailerons.

Also, regarding elevator deflection, there would not be any at all if the throttle is turned all the way down, because that disengages the altitude controls.

Best regards,

Bill

[Phillip Kocmoud]

That's what I get for only flying deltas...

[William Premerlani]

Phil,

Good point. I just assumed that Keith was flying a "normal" airplane, but perhaps he has a delta. Keith?

Bill

[KPack]

I should have specified my aircraft sorry. I am mounting the UDB4 to my Hangar 9 - Arrow 40 that I converted to electric.

The solution: I powered up again and waited and after a few minutes the problem is gone. I don't see the problem on subsequent power ups. So, I think the problem is fixed.

Another question: I have my speed control inside the aircraft. The cooling air will pass over the speed control and then over the UDB4 board. My speed control data logging shows my temperature changing from 80 F to 120 F jn the speed control. As the temperature climbs inside the aircraft will this be a problem for the accelerometers or other sensors?

Thanks for both your help!

Keith

[William Premerlani]

Keith,

Regarding temperature effects, if you can at all arrange it, it is best not to get the UDB4 hot, it will create an offset shift for the accelerometers, which will create a shift in the vertical reference.

I did a lot of tests on this a few years back, and discovered the accelerometers used on the UDB4 will shift the tilt by about 0.5 degrees for each 1 degree C change in temperature of the UDB4.

Best regards,

Bill