Throttle scaling Fixedwing without airspeed sensor

PX4 Autopilot
1

Hi PX4 enthusiasts!

I’m currently tuning a little fixedwing foamie without airspeed sensor.
Flys fine already!

I used many tips from here: VTOL Without an Airspeed Sensor | PX4 Guide (main)

At the moment still not working well is the throttle scaling over battery voltage.
So, as the battery voltage decreases over flighttime, the throttle must increase, to keep the same thrust (and airspeed).
At the moment, if I adjust the throtte for full battery, the plane flys slower and slower over longer flighttime, even until stall. I must increase FW_THR_CRUISE when battery voltage gets lower.

I know, that using an airspeed sensor would do this better, because it simply keeps the airspeed constant by increasing the throttle.

Is there a way to solve this without airspeed sensor?
I found FW_BAT_SCALE_EN is 1 on my plane already (Def.:“Whether to scale throttle by battery power level”)
So this sound like it should do the job, but it doesn’t. Or too little.
How can I increase this functionality?

I tried to adjust up and down BAT1_V_CHARGED (4.2V) and BAT1_V_EMPTY (2.8V) but couldn’t see an improvement. I use a LiIon battery BTW, which looses more voltage than LiPo, maybe that’s why I need the stronger scaling.

Would be thankfull for any advice!

Thank you!
Best regards,
Andreas

2

Hi @Aeroandi !

Yes indeed, FW_BAT_SCALE_EN together with a good battery estimation should normally do the trick. You can find the applied scaling factor in the an uorb topic: battery_estimation.scale.
How does that field look for your tries? And how is battery_status.remaining?