I originally posted this to the drones-discuss Google Group, but it was suggested that I repost here in case Michael Oborne could provide some assistance.
I am currently trying to implement a modified throttle controller on the APM for formation flight and have come across a potential bug (or operator error on my part) relating to the throttle setting when doing HIL simulation through the Mission Planner software.  I am basically seeing that the throttle is 0.000 until the throttle stick is physically moved up to approximately 50% of its travel, then the throttle linearly increases from 0 to 1 in the upper 50% of travel.

I am running Mission Planner 1.2.48, but have observed the same behavior in the newest version of Mission Planner as well.  I am using APM 2.5 running version 2.68 of the ArduPlane firmware.  As mentioned, I have modified the firmware, but see the same behavior on another board running stock firmware doing HIL sim on a different computer. 

I have calibrated the radio (and made sure to set the throttle stick all the way down when centering the sticks).  I can confirm both through the calibration tab and through serial debug that the PWM value on throttle is increasing linearly from 1084 to 1920 ms.  I am also sure that the flight mode is set to manual, so it should be doing a direct passthrough on throttle.

My feeling is that the Mission Planner is reading the PWM throttle command and incorrectly mapping that to a throttle setting (0 to 1) for use in simulation.  Any ideas of what could be the source of error or what I need to do to fix the problem?

Thanks!
-Mike

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  • Developer

    Michael,

    try setting throttle trim to the mid range of that channel. ie ch3_trim = 1500 or similar

  • As a follow-up.  I have actually found that I can reassign the value of RC3_MIN to equal RC3_MIN - (RC3_MAX - RC3_MIN).  This "hack" works for me by letting the throttle scale more like I would expect it to, but becomes a potential safety issue if someone forgets to recalibrate before trying to actually go out and fly outside of the sim.  I can get by with this, but it may be worth looking at for future releases of the APM Mission Planner.

    Thanks.

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