Increasing RPM without throttle

when quad is on the ground with small amount of constant throttle, pixhawk automatically and slowly increasing motors rpm.
Its in stabilize mode. I noticed when quad was not in level the rpm increase was more rapid then if qaud is in levelled position.
I also tried acro mode, but same problem.
BTW where can I see RPM in MP? In QUICK window I can select rpm1 and rpm2 but it shows only zeros…

Arducopter uses multiple PID controllers to control the copter. PID stands for Proportional Integral Derivative controller.
As soon as you raise the throttle, all calculations start to run.
What you are seeing is the effect of the integral part. The copter never is perfectly level on the ground and the sensors are noisy. The integral part adds up the error between level and actual attitude of the copter over time and generates an output from this.
Since the copter sits on the ground unmoving, the integral gets bigger and bigger and so the motor rpm is rising.
Lift off as soon as possible after raising the throttle! Otherwise the copter may flip over after lifting off.

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