Throttle setup in AC 3.4

My Trex 450 Pro / Pixhawk is finally tuned and flying with Throttle in Ch. 8 Input mode (1) using a throttle curve setup in my radio. I thought that the controller would not adjust throttle with this configuration in Stabilize mode? But the settings in MP Heli setup for Throttle Accel (P,I,D,IMAX) and Throttle Rate § seem to have a big effect on my throttle output. I am getting sudden changes in RPMs. The docs (ardupilot.org/copter/docs/traditional-helicopter-tuning.html) appear to be outdated and I am stuck. Am I correct in using H_RSC_MODE=1? Is possibly the new feature that autosets hover throttle causing a problem?

Not a lot going on in Traditional Helicopter anymore it seems.

I have my electric set up with the throttle on a switch. It’s either on or off. No throttle curve in the radio. When I arm the rotor doesn’t spin up. Flip my throttle switch and it starts the motor and it spools up to governed headspeed.

How fast it goes from no zero throttle to governed throttle is set with H_RSC_RAMP_TIME. The main rotor normally takes longer to spool up than the throttle signal ramp time and that’s set with H_RSC_RUNUP_TIME. From there the governor just holds the headspeed.

I think, but don’t know for sure, that there is a type of throttle curve available with the params H_RSC_POWER_LOW and H_RSC_POWER_HIGH where power low is the throttle signal at zero collective, and power high is the throttle signal at maximum collective. Since I use a governor I don’t know about that for sure.

Just a note to be careful with AC3.4. As I found out yesterday, if you apparently take off before the runup time has expired and switch to Pos Hold flight mode it will drop collective to full negative and the result is not good. Don’t even use Pos Hold. Use only Loiter.

Hi,

POS_HOLD issue was resolved in AC3.4.4.
http://discuss.ardupilot.org/t/copter-3-4-4-released/13962

As for the throttle PID tuning, I’ve used external governors with H_RSC_MODE set to 1 without any problem, but in my case CH8 was assigned to a rotary dial on the transmitter, instead of the throttle stick. In any case, I think it is recommended that you use a governor, or at least use the expo on the Pixhawk, not on the transmitter.

FYI: explanations for RSC_POWER_x parameters:
http://ardupilot.org/copter/docs/parameters.html#h-rsc-power-low-throttle-servo-low-power-position

I feel like an idiot! My problem turned out to be that my throttle curve on the tx was set to “INHibit”! Although I had set up a throttle curve to simulate a governer mode (0-25-75-75-75), it was not active and I was blaming it on the throttle PID.

Since Mode 1 is pass-thru you should be able to use a throttle curve programmed in your transmitter, whether it be slaved to the collective stick, or a knob. I would recommend having a switch associated with it like a Throttle Hold, though, if you slave it to the collective. Otherwise, if you do an autrotation and shut down your motor by going to full negative collective, some ESC’s won’t restart right away and you may find yourself doing a full autorotation to landing.

Mode 2 is governor mode, and is what I use with my electic.

Mode 3 is what I use for my nitro heli. I would think that Mode 3 could be used for electric, but somebody that has tested it and knows how to set it up for electric would have to comment on that. It does provide somewhat of a throttle curve in the software, plus idle up to prevent a petrol engine from stalling for warmup without the clutch engaged.

I’m making some comparisons between AC3.3.3 (which I consider safe), 3.4.2 (which I was flying with a rather expensive crash a couple days ago), and AC3.4.5. Yes, the problem with taking off before you do your ramp up countdown and having full negative collective slam in when switching to Pos Hold was fixed. However, Pos Hold should not even be in Heli Like a stupe, I had programmed my flight mode switches and mixer on Heli to be the same as for my Tri’s, and Pos Hold was one of those flight modes. When I accidentally switched to it the results were not good. That mode is not in the settings for my 700 nitro, and when I carried over some of the settings for my 600 electric from my Tri’s it wrongly ended up in the FM mixer.

If anybody has used H_RSC_MODE 3 for an electric, it would be interesting to hear the results and how it was set up.

I flew my Trex 500 today using Mode 3 in AC3.4.5. It works fine for an ESC with no governor built in and yields the same as a three-point throttle curve set up in your radio with Mode 1. With the added advantage that the Pixhawk can use the throttle curve on Auto Missions with Mode 3, and has complete control over the throttle and headspeed. After I fiddled with it for a bit and figured out what values to set the low (full neg collective), mid (zero collective), and high (max pos collective) to, it was able to maintain headspeed on my 500 +/- 40 rpm (I have telemetry on my radio with a mag tach pickup on the main drive gear) using a non-governed ESC.