Hello,
I have built a quadcopter UAV using ArduCopter version 4.5.3.
The hover throttle is set to 0.281 through hover learn in ALTHOLD mode.
At the start of the flight, the throttle output is close to the hover throttle, but during a long flight, it starts decreasing below the hover throttle. The flight weight is close to the weight on which the hover throttle is learned. The UAV is flying at a constant weight throughout the flight.
Is this normal behavior, or could something else be causing it?
Does this affect the overall flight stability?
I have attached an image showing the plot of throttle output and hover throttle.
The quadcopter was flying in Auto executing a 2D Grid mission at an altitude of 60 m.Then I switch to loiter and bring it back to home point.
In a separate flight, I have observed same behaviour when the copter flew like 20 mins in Auto mission and then hovered in place at a low altitude of 10 m for next 20 mins. The Throttle out lowered in both sections of the flight as the case here.
In the above image i have mentioned the current, voltage and throttle out at two different time frames in the auto mission and there is almost 15% drop in throttle out.
I am using a Li solid-state battery, and for initial parameter tuning, I set the high and low voltage limits to 4.2V and 3.0V, (MOT_BAT_VOLT_MIN=36 and MOT_BAT_VOLT_MAX=50.4) respectively. However, the manufacturer specifies that the battery can be discharged down to 2.7V per cell. Should I consider using this lower limit, or is it acceptable to continue with the 3.0V threshold?
If you look to the two marked points and calculate the used power, than you see that the used power is a little increasing while the Throttle Out is decreasing
