To add to list:
- mismatched motors, props, ESCs, ESC calibration, anything that causes a different amount of thrust in one or more motors causes some tipping until the PID "I" term adjusts for it over the course of typically a second or two.
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I thought deadband is for ignoring small amount of changes in all range (by analogy to mechanical loose in steering system) but not related with detecting neutral range in such cases.
Deadband only removes small changes that are near neutral. If you use 25% stick (anything outside the deadband) plus or minus a hair, the hair is acted on as if there is no deadband.
Sensors are calibrated
Maybe calibrated incorrectly so I suggest to recalibrate. The worst thing is that recalibrate may be a waste of time.
mag show max 2% (Mag is green before take off).
Mag is not used with Basic/Complementary (no mag) AttiEstAlgo, but is used with INS13
I have installed OP GPS and tried fly with INS13 but it's impossible even to take off, quad flips or fall bank immediately after throttle increase (GPS has steady fix).
Assuming you were using Attitude mode, this is a big hint that something is actually wrong. It is not good to use GPS flight modes for takeoff if you sit on the ground with motors running. The GPS position changes and it tries to move to new GPS location while it is still stuck to the ground. Use Attitude mode (with manual throttle) for takeoff.
Flying with complementary+mag gives chilling experiences witch sudden flips or changes with directions, so I suspect on board magnetometer has problems with wiring, FC is too close to power distribution PCB (10 milimiters below it) etc...
This is a very large hint.
If complementary (no mag) is OK, then there is a problem with the mag. It is recommended to not use the "on board" mag especially with small (say less than 450) quads. Part of mag (and thus GPS) setup is to get all motor power wiring well twisted and without this, the mag fields from the wiring completely overpower the weak earth mag field. It is generally recommended to use "aux only" mag (mag built into GPS) for all electric models.
But starting without "little help" could big drift, jumps to the left.
Even when using Attitude with Basic / Complementary (no mag)?
I instinctively always try to gentle take off to avoid unexpected flips or hits when something goes wrong, fast take off would be a big challenge to me.
It should not be scary. Small throttle blips up and back to zero. Starting small blips and getting bigger and bigger helps you know how much power it needs to take off.
Currently only Basic algorithm works for me and I fly only with attitude mode, I'm not ready for rate mode yet, still practicing.
I confess that I use mostly Attitude mode for my quads because I am mainly interested in GPS flight modes.
What is INS13 mode or INS13Indoor, I guess is related to GPS but how it works in detail?
INS13 uses a high tech computer code that uses all data from all sensors as input and produces position, attitude, and velocity as output. For instance, even the 3D mag is fully used to help know which direction is up. It works by constantly updating a list of values for all 13 output numbers. There is a weight table that says which sensor should be believed more if they disagree (sensors should not disagree much or there is a problem). For instance GPS altitude is known to have a fairly large error. Barometer altitude has a much smaller error, but it is not accurate over a long time period such as when the weather changes. Baro altitude (even with a good hard coded correction table) changes a lot from day to day. So for altitude, the GPS is believed over the long time frame, but the baro is believed over the short time frame, and these two sensors are "fused together" to give an altitude number that is better than either one alone could give.
I tried AutoTune but whole process is too long, durning shaking quad drifts a bit far away and I have to switch it off and fly back to start position. Documentation says that AutoTune needs ~60s to complete but it's too long for me... The documentation is not clear for me: can I touch sticks/ throttle to prevent dirft away durning tuning or not??
Yes, sticks are enabled and you should keep it close with small smooth stick motions.
I wonder is it possible to tune revo with 250 frame to fly steady as a rock like commercial drones? Without drifting, with holding altitude without swinging, with slow and gentle take off etc..?
Revo with Basic/Complementary(no mag) runs code that is similar to CC3D and should act like CC3D.
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If you post your settings (File -> Export UAV Settings ... with Revo plugged in) as an attachment. I/we can look at them to see if I see anything strange. Maybe even put them in a quad to see if they fly for me.