Hi i have been having issues getting my home made quadcopter to fly. To test bits out i built a rig so i could spin it up but keep it tied down. Basically when i increase the throttle two motors stop spinning and while the other two spin up fine. Also the two that stop spinning dont respond to tilting the quadcopter. The two that do spin work as expected and hold the quadcopter level really well.
If i put the quadcopter in acro mode then all motors spin up fine but in this mode i cant take advantage of the gyros.... Please watch the video below and it should all be clear whats going on.
https://www.youtube.com/watch?v=KY8OI8T16wM
Cheers
Chris
Replies
Hi,
Sorry for the delay on this i broke a prop and had to wait for a new one to come into stock. I still cannot find an answer to this. So far i have tried the following.
Replaced both speed controllers on the roll axis. (no effect)
Swapped the motors over to see if the issue followed the motor (it didnt)
I have now even replaced the ardupilot board (also had not effect)
I have been looking at the configurator while the motors are spinning to try and see if the motor output supports what is happening. I think it does.... Generally the left motor outputs upto 20 higher than the right motor (see attached image). So my next question is why? At first i thought could this be a vibration issue but watching the roll accel output I can see it does jump around a bit but surly this would make the quadcopter bounce around rather than smoothly roll to the right???
If i put the quadcopter into stable mode and spin up the throttle i can see it is trying to tilt the same way as in acro mode but it corrects itself straight away, this isnt ideal as it will make it unstable..
If anyone can shed some light on this it would be good. I just cant see what is going on....
Cheers
Chris
RollDriftMotorOutputs.jpg
Right i have managed to test stable mode fully now so i thought i would try a small test flight but i have come across another issue.... As i spin up the throttle the quadcopter tilts to the right. I can counteract this to a degree with the roll stick on the controller but it is very unstable. I have checked it with my rig and it is balanced... while it is on the balance rig it sits there level but when i spin up the throttle (just a small amount) it starts to tilt to the right... Does anyone have any ideas?
Here is a quick vid to show what it is doing https://www.youtube.com/watch?v=GPbaQOzH-Yo
if you want to test in the rig:
set Yaw PID to 0
just a side note: acro mode uses unly gyros, you need them for flight, what you mean are the accelerometers
I agree with john reynolds that it's trying to yaw. I think you will only see this behaviour when you have the throttle very low - increase it and it will act better. Engines stopping while flying will cause a crash so you might considering using the CLI menu to set the min throttle higher. This has the effect of meaning that your engines will always spin when armed which some people don't like..but it will remove the danger of engines stopping in flight which is very bad.
-Randy
The reason for this is that stable mode expects your quad to rotate. When it is fixed like that, or even just sitting on the ground, stable mode keeps trying to correct for yaw (which is why two motors on the same arm power down and eventually reach zero). Acro mode doesn't do this because it doesnt compensate for yaw the same way stable mode does.
When I launch my quad, I always launch in acro mode and then immediately flip to stable mode to avoid this issue.
These two pics show the quadcopter output one on stable mode and one on acro mode. As you can see the adrucopter just isnt sending out the motor commands.....
stablemode.jpg
acromode.jpg