[terrance]

hi i am having this problem with my dualcopter. initially when i test run the motors without the propeller blades, i can hear the nice motor hum/pitch from low throttle to high throttle. but when i installed the propellers blades, the pitch will increase slowly without i adjusting the throttle, and then the dualcopter will "jump" when it reached the peak and i have to throttle down immediately.

tried a few times also the same results. so i am wondering which part of the hardwares is bad and/or need to be replaced.

[TheOtherCliff]

Slow increase is normal.  When it is on the ground it tries harder and harder (winds up) to be level.  In the air it only takes a tiny tiny difference to cause rotation to level.  When on the ground, it would have to be enough difference to pick the low arm up off the ground.  Then the difference is large, and when it gets into the air, it takes a while to "unwind", and flips over before it unwinds.

Solution is to take off immediately as soon as you start the motors, and only use throttle until it is in the air (no roll / pitch / yaw).  Increase the motor speed quickly until it is in the air.

Maybe move throttle from 0% to 20% and back down to 0%, then try 0-30-0 then 0-40-0 etc. until you get a feel for how much it takes to get off the ground.

[terrance]

so there is nothing wrong with my hardware then? my guess is that when on the ground, the propellers which are much closer to the ground are downwashing the air flow which doesnt have much space to spread hence will cause some backflow current back to the pros causing the pitch increase and the "jump".

is there a way to do a gradual takeoff rather than immediate take off? 

[TheOtherCliff]

Rate mode is better for gradual takeoff, but it may cause crashes for a beginner since it does not automatically level the aircraft.  In any case, you don't want to move any stick except throttle until you are in the air.

Jumping into the air is not difficult.  Sitting on the ground, start with little throttle blips and make the blips bigger and bigger until you find what it takes to get it in the air.  Use that amount or a little more.  Try to get it knee high and keep it there.

[terrance]

tks for the advise, i have managed to find some similar issue on the internet regarding this. there is actually a term for it, its call instra-flip when the drone flips the moment it throttle up.



however, my problem is not listed in the video as mine is a dualcopter and have also checked all my connections are in order.

[TheOtherCliff]

From the title, I suspect that is a different issue.  If you mess up any of several setup things that make e.g. the left motor increase when the right motor should increase, the left side (for instance) may get low and that should make the left motor spin faster.  But since it is connected backwards, the right motor spins faster and now the left side is even lower.  This repeats many times in a 1/10 of a second and so you get instant (from a human perception) full power flip.

That is different than "I" term windup (what we discussed ), which is what we avoid by:
- leaving "Zero the integral" at the default value of enabled
- taking off quickly, as soon as you start the motors; don't increase throttle slowly, do it quickly and take off right away

[terrance]

will it damage my esc and/or motor if i do the immediate take off? my other concern is will it shoot straight up before i can level it down?

[TheOtherCliff]

no damage
that is why you try bigger and bigger throttle blips ... to find what it takes to take off ... so you get a feel for it and don't use too much.

[terrance]

is this going to be the same everytime i take off? i would have though that it can do a gradual take off like those bigger quad. btw does those dji phantoms or bigger have the same issue?

[AerialPerPlexity]

I followed the other cliffs advice when I got into the hobby, About when you arm and take off... And when you do it , you get use to it. Its like a glove   you get that same feeling and if something is Wrong you know right away. because if you pop your craft up every time you know how much throttle to give it, to how high it goes. So when I change props I can tell right away how much thrust they have and at what rpm. So if your new to a craft start slow and the more you fly it, the more one becomes the craft.

[TheOtherCliff]

The amount of problem you have is more when the ground is sloped more.  It is more when you move the throttle more slowly.  It is more for different quads.  It is more for different PIDs (I term windup).  It is more if you move the sticks (like to try to "help it correct for a slope") before it is off the ground.

If you start out with "jumping up right away with controls neutral", you know there is not a problem from any of these.

You can then experiment with changing any of the listed reasons, like you can experiment with slower motor runup on level ground (never on a slope) to see how much you can "get away with".

And this happens mainly in auto leveling modes (Attitude, Rattitude ...), much much less in Rate.

[Mateusz]

is this going to be the same everytime i take off? i would have though that it can do a gradual take off like those bigger quad. btw does those dji phantoms or bigger have the same issue?

You can make gradual takeoff with LP when you get used to it. DJI Phantom may not have that behaviour. These commercial quadcopters, from the first day, use all sensors and throttle stick is not controlling real throttle, but vertical position afaik You can control vertical position if you have enough information from sensors. All open-source firmwares, can also be used for racing copters, that's the default configuration using Complementary sensor fusion algorithm (using only gyro and accel). With these two sensors only, you can't control vertical position accurately I think. LP has INS13 sensor fusion algorithm (EKF for navigation) which uses more sensors, but it will still use throttle as real throttle, there has never been a need for anything else. Furthermore, DJI Phantoms are just one hardware, which means they can be shipped already tuned. Open-source firmware can't be tuned to any specific build, as it has to run on wide range of vehicles. Most problems people have are usually bad tune, bad build or bad configuration. If you want to just fly, DJI is a choice, you don't have to know much, when it breaks or goes nuts, you don't even need to know why it flew away. With DIY hardware and open-source firmware, you really need to know a lot and learn a lot, it's mostly about learning, building, tinkering. DJI places magnetometer in landing pads, for a good reason, and many users realize why when their self-build copter goes nuts