I was thinking, during the first take of take off, the Crazyflie tends to yaw towards a certain direction which then keeps stable once it is in the air (I observed this first using a joystick without yaw axis at all so it's not a bad axis input).
Does this happen to other people? What could be causing this effect?
It's not a big deal when flying and you can just correctly manually and then it will be fine. It only happens on [first?] take off, but it will be optimal that the CF would take of keeping the direction on which it was landed. And overall I'm just curious of the reasons behind it.
Yaw correction on take off
Re: Yaw correction on take off
Normally it should take off pretty straight if the ceter of mass is good and all the motors perform equally. Have you tested if each propeller seem to turn equally well? E.g. there might be hair stuck on the axle, the propeller could be pressed down to tight or possibly a bad motor. You can also check the PWM bars in the cfclient when houvering at one spot. They should then be about the same if the system is well tuned. It can also be that the motors are a bit tilted so that the thrust isn't directed downwards but in a little angle. That would also cause this effect.
There are many possibilites to the effect but I would start investigating the above.
There are many possibilites to the effect but I would start investigating the above.
Re: Yaw correction on take off
Hmm I have thought of these things, but I'm not sure it is any of them. PWM bars are about the same. This only happens on take off. Once it is on the air the CF is stable, it does not drift away to one side or anything (actually I am very happy I don't even have to fine-tune skewing for the axis).
I see the problem most if I increase the thrust very slowly until it starts flying slowly. It it is like it tries sometimes (sometimes not) to head in a certain direction which is not always the same (this is the confusing part). Once in the air, it flies perfectly and does not yaw again to it or anything (perhaps the stabilizer compensates it if a motor is misbehaving?). Anyway if it is not a wide-spread effect I'll look closer into my CF and find out what's going on.
I see the problem most if I increase the thrust very slowly until it starts flying slowly. It it is like it tries sometimes (sometimes not) to head in a certain direction which is not always the same (this is the confusing part). Once in the air, it flies perfectly and does not yaw again to it or anything (perhaps the stabilizer compensates it if a motor is misbehaving?). Anyway if it is not a wide-spread effect I'll look closer into my CF and find out what's going on.
Re: Yaw correction on take off
Try going into Advanced mode and set Yaw % at 0. This will eliminate any minor variations in controller calibration. Does it still yaw? Then it is an issue with blades, etc. as tobias mentions. By the way. I found this to be a great first timer fix for learning to fly. It eliminated some nasty yaw while I was learning to control the thrust.
Re: Yaw correction on take off
When taking off slowly there are a lot of ground effect turbulence. If you feel confident you can try to take off quickly, if the yawing effect is gone then it is caused by turbulence.
[SOLVED] Re: Yaw correction on take off
Thanks all. I'll mark this as solved. It was just a doubt. I wanted to know if some special physics or mechanisms I wasn't aware of impacted this. It seems taking off VERY slowly means one of the rotors is the last one to take off so it causes a slight turn as it is still touch the ground. This can be caused by multiple causes mentioned but it is not a real issue. Taking off normal slowly and fast seems to work as expected.