@SteveOsborne wrote:
I have been doing some DIY thrust testing for my 2.5" prop quadcopter (Arducopter 4.0.3) with a kitchen scale. Basically I have the quad mounted upside down, so the thrust goes down “into” the scale. Seems to work well enough.
Anyway, I have been using the Mavlink Motor Test functionality to spin up my motors to a given PWM. This is basically the same as the Motor Test sliders on the tab in QGC or Mission Planner.
My problem is that the thrust I get out of the Motor Test is much higher than the thrust I actually get from the throttle during “normal” operation. Example: on 3s, with Motor Test, my max thrust is 370 g. But when I arm the copter and throttle up all the way with RC transmitter, I max out at 210 g. This is a big difference!
The point at which the throttle loop maxes out is actually somewhere a little north of mid-throttle, about 1600 PWM. In other words, my PWM vs achieved thrust looks the same for 1000 - 1600 PWM for either method. It’s just that the Motor Test method yields an increasing thrust all the way to 2000 PWM (370 g) whereas the throttle method stays at 210 g all the way to 2000 PWM.
So, what’s limiting thrust in the Arducopter throttle loop? Relevant (maybe?) parameters:
MOT_PWM_MAX = 2000
MOT_PWM_MIN = 1000
MOT_PWM_TYPE = Dshot600
MOT_SPIN_ARM = 0.1
MOT_SPIN_MIN = 0.15
MOT_SPIN_MAX = 1.0
MOT_THST_EXPO = 0.25 (I’ve tried changing this from 0 to 1, with no effect on my problem)
MOT_THST_HOVER = 0.8 (I’ve tried changing this from 0 to 1, with no effect on my problem)
SERVOn_MAX = 2000, for n = 1-4 (my motor functions)
SERVOn_MIN = 1000
SERVOn_TRIM = 1000 (tried 1500 too)
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