small quad, no stable hover

[Shogun]

Hi,
I need some help to get my copter to a stable hover. It's a small 30cm quad, 1400kv, 8045 props, fw 6.6r19. It works perfect with the MultiWii.

The throttle is very sensitive, with FactorThrottle=0.35 the hover now should be at about stick middle position. The dead band is set to 60.

I played a lot with NavAltSpeed, settings now are:
P=2, PM=10
I=2, IM=60
OM=60

Whatever I do at the stick, the copter is either climbing or descending. I can't get it to hover. What can I do to get that fixed?

[Max]

So you're saying it flies stable otherwise, but just doesn't hold altitude in PH mode? Can you get a steady hover manually?

-Max

[Shogun]

As far as I can say now it is stable on tilt and yaw with the default settings, but no stable hover. But I am not able to do further tests and fly around.

[Shogun]

OK, she flies.
After some pid tuning this morning the altitude is still little oscillating and has drift about 50cm. This does by far not beat my Naza, but is promising. The copter is very stable on tilt and yaw.
I just corrected the manual hover from 500 to 700 as this seems to be hard coded for alt/pos hold. FactorThrottle=0.225 did the job but I have no feeling if it's safe to do so. Motor/Esc Hover Throttle also from default 500 to 700. Hope to test this tomorrow outside.
Alt Speed Settings now is
P=14, PM=50
I=0.1, IM=200, OM=200

[Shogun]

I was not lucky with the last changes, after switching from manual to alt hold the quad fell like a stone, full kicking in throttle could not prevent that. Only the landing gear was broken. I will now revert to MultiWii.

My opinion is: AutoQuad is a promising concept, I like the different approach it uses against all other flight controllers. Please do not forget to also develop for smaller copters. When the product is ripe, and I am very confident it will, I will return. And no, I will not sell my unit.

[JussiH]

Sry, just saw this...

I have flown a similar size copter on AQ, with good results on similar altitude_speed settings to yours, so there is something wrong in your setup somewhere. I am gonna assume that your board is properly calibrated according to the instructions in the wiki, but if its not that could be part of the explanation for erratic pos hold... But it does sounds more like a radio problem to me....

Without more details about your Radio setup, craft parameters and especially a flightlog I can only really guess at what is going on, and the more data you supply to begin with, the easier it gets to help you out.

It sounds like you have your radio endpoints for throttle maxed out or there is some other problem with your radio setup or scaling - that would explain why you have go as low for throttle factor - "normal" values is between 0.5 and 0.6, depending on your throttle ranges. Use the radio tab in QGC Widget to set up throttle for a total range of circa 1400 with center stick at 700

Take a look at Steves method using flightlog to set up throttle:

viewtopic.php?f=27&t=539&start=10#p2735

Other causes of erratic position hold behavior is vibration at certain frequencies that can saturate the Z-acc and cause very sudden jumps or drops in altitude estimation. Again, the flightlog is a powerful tool to identify and root out such problems.

Have you covered the pressure sensor in foam and shielded it from sunlight?

Do you have a proper ground plane between antenna and controller?

Are you using fast-update ESC´s (Reflashed or ESC32) If using reflashed Atmel type ESCs without external oscillator, make sure you calibrate them often (or replace them with one that has an external oscillator)... Autoquad needs well-balanced, fast update ESC´s to work properly!

If you have a low range on one or more of your ESC´s, it could also be an explanation for the problems with the throttle factor. The controller does an excellent job of masking up such imbalance up to a certain point.

It puzzles me that you state angle/rate PID is at default, I found that for a similar size frame with TMotor 2208 1100 KV with EPP0845 on 3S with ESC32, I had to more or less cut Rate and Angle D in half, or it would wobble itself to death.

[Shogun]

Thanks Jussi, I appreciate your help and will give it another try. I have to wait for a new landing gear.

The copter is a Quadrixette 30 with 0845 props on 200W A2212 1400kv, 3S. ESC are 30A Flyduino simonk preflashed. AUW is 800gr. The quad worked excellent with my MultiWii.

The radio endpoints in QGC are 6 and 1360. In the transmitter I gave a little expo with 33 and 67 at the 25 and 75% points.

I did not know the Steves method, but this is what I did to find the 0.225 for throttle factor.

I also suspected vibrations and balanced the props before yesterdays flights. They were not well balanced.

The pressure sensor is covered with dark foam, I use a 5x5cm alloy plate as gps shield.

Like you I expected to cut tilt and yaw pids but no wobbles, absolutely stable.

I attach my params and a cut-out from the last logfile I have. I guess it was from sunday with the not well balanced props. Btw, is there a function in QGC to download the logs?

[epyonxero]

[Shogun]

This should definitly be covered in the wiki. I had a closer look at Jussi's link to Steves method. He set a throttle factor to bring mot_throttle to 700. Jussi speaks about a radio thottle of 700. I did the last, my mot_throttle in hover is about 150.

[Kisssys]

I think we have some confusion on getting the throttle set correctly so I'll touch on this again.

In QGroundControl their is a setting for Motor/Esc Hover Throttle and sounds like a good place to go. It is actually not currently used but is available. You can put anything you want here and it won't matter.

We want to change Factor Throttle so that in a hover the throttle viewed in LOG_RADIO_CHANNEL0 is 700.

FactorThrottle.jpg (37.46 KiB) Viewed 19140 times

So do a flight in manual and see where it likes to hover and look at what the average throttle is at a hover.

To get the value you need in Factor Throttle you divide that average number by 700. Multiply that number, it may be less than one slightly or greater than one slightly and multiply it times current Factor Throttle. Now put this in the Factor throttle window and write to ROM . This will adjust it so that with a LOG_RADIO_CHANNEL0 of 700 the copter will put out the necessary power to hover at that setting.

If you have messed with the throttle curve on you transmitter it is fine to do so, I do all the time. Just make sure that you don't change the point for the center of the throttle range. Do it so it looks like a expo curve around that point if you want to soften the feel around the hover. At half throttle you want your LOG_RADIO_CHANNEL0 to be 700.

We probably need to remove the Motor/ESC Hover Throttle setting until it is used from the setup menu.

For inquiring minds that want to know, in the following line of code you see the hover throttle setting being used.

expFactor = constrainFloat((p[MOT_HOV_THROT] - throttle) * p[MOT_EXP_FACT], p[MOT_EXP_MIN], p[MOT_EXP_MAX]);

The fact that p[MOT_EXP_FACT] is currently assigned the value of 0 makes the value of MOT_HOV_THROT go to 0.