100% throttle when airspeed low or climbout - regardless of FW_THR_MAX?

PX4 Autopilot Flight Controllers 💻
1

Hi,

Could someone please tell me what causes the throttle to go to 100% (FW_THR_MAX set to 50%) at the time of about 355 and 375 seconds in the picture below? Is there some stall prevention system, or is the plane entering the climbout mode? What controls the maximum throttle in these situations?

The flight mode is Return when the throttle is non-zero and otherwise Stabilized (ie. the throttle goes straight to 100% when activating Return and the airspeed is low).

Screenshot from 2018-04-15 12-02-22.png1517×975 88.9 KB

(The thottle output is with an offset of -1000, airspeed is scaled 100x and altitude and altitude setpoints are scaled 10x.

Regards,
almaaro

2

After some research, the issue was solved! In firmware/src/lib/ecl/tecs/tecs.cpp there is an underspeed protection, which sets the throttle to 100% regardless of any limits.