From the manual (this, this and this) I did not understand enough how the APM controls the collective pitch and throttle in AltHold mode.
According to the description, everything looks like the APM controls only throttle (AltHold Tunning section).
However, in the manual there is a mention about setting the midpoint of the collective pitch for AltHold (Swash Set-up section). But there is no description of how the APM controls the collective pitch and how can I setup the parameters of the collective pitch changes in altitude hold mode, there is only about throttle parameters.
Can anyone explain, how the APM works in AltHold mode for heli or specify where it’s described?
Sorry for my english. Thanks
I would appreciate explanation of throttle and collective pitch handling by APM (and naming in Mission Planner) from someone who is involved with APM:Copter for TradHeli development too.
As far as I understood till now, things connected to altitude control of heli with word THROTTLE rather mean collective pitch handling than the throttle handling. E.g. ThrottleOut in Log Analyser or THR_ACCEL_X in APM parameters…
Еhanks for your reply! Yes, it seems to be true.
I have done various tests on the ground, connecting the servo to Throttle out, and it looks exactly as if all the Throttle parameters in “Extended tuning” tab operates only with collective pitch.
To control altitude, APM uses collective pitch channel, not throttle channel.
Throttle signal from receiver passes through the APM without changes in althold mode.
Yes, this is all correct. In most cases, mention of “throttle” in the wiki is intended for multicopters, and should really be called “collective throttle”. In our case, this is “collective pitch”. Arducopter does not really control the real “throttle” for the motor, it just passes through, with the intent that you are using an ESC with a good governor.
Sorry for the confusion on this point, but I don’t control the nomenclature the multirotor guys use.
It’s even worse in the code, the servo outputs are all called “motors”.
@Rob: Am I right if I say that Radio Fail Safe uses channel for collective pitch (3) instead of throttle channel (8)?
Hi Rob, I’m trying to get my traditional helicopter (electric without a governor) up and running with ardupilot and I am a bit confused about the altitude control. I wanted to know in AltHold mode, does altitude controller drive the collective pitch alone as a SISO system or does it control both speed and collective pitch? Also, if it is a SISO loop, how is the motor speed driven? I know there is a parameter H_RSC_MODE available for configuring rotor speed control. So far I’ve used “Ch8 Input” as the mode, so I controlled rotor speed explicitly in “stabilize mode”. I can’t imagine this setup working if I just changed to AltHold mode - because I’d have to control heave rate and rotor speed with the throttle stick. If I change the mode to “Throttle Curve” and set throttle curve points appropriately, will the throttle be driven by the collective pitch (as determined by the altitude controller) and thus I only have to control heave rate with the throttle stick?
Thanks for any clarity with this matter.