Collective pitch output on Tx defined in plane mode

Hi Chris,
I am coming back to you after a long period of hibernation for heli due to other constraint.
So, thanks to your high assistance combined with other experts, I succeeded step by step to set the heli’s organs to the Pixhawk.
Nevertheless, I am still facing 2 difficulties as follows:

  • I set the H-col_M related to -9, 0 and +9 degrees. But those pitches of the swach plate does not change according to the flight mode. For instance, I would like to have -3, 3, 8 degrees according to the stick position, when stabilize mode is selected. Although IM_STAB_COL is set to 0, 400, 600, 1000.

  • the second diffficulty is that there is no response of the swash plate and the yaw servo neither when I lean down or up and turn left or right the heli. I just hear the servos growling. This happens in armed condition.

Thanks again for your help.
Sincerely Yours

To limit the minimum pitch in Stabilize, IM_STAB_COL_1 has to be set to a value higher than 0. This corresponds to the stick position all the way down.

To limit the maximum pitch in Stabilize, IM_STAB_COL_4 must be set to a value lower than 1000. This corresponds to the stick position all way up.

IM_STAB_COL_2 & 3 correspond to stick position at ~40% and ~60%, respectively. And must be set to get the helicopter to hover at mid-stick in Stabilize.

Several things must be true to get a corresponding swash movement:

  1. you must be in Stabilize flight mode
  2. H_CYC_MAX must be set to a reasonable value, at least 2500
  3. H_SV_MAN must be set to 0
  4. The output from the rate controller must be sufficient to provide attitude correction, recommend ATC_RAT_xxx_VFF be set to 0.15 to start.

The second video in the wiki covers setting servos and pitch ranges:
http://ardupilot.org/copter/docs/traditional-helicopter-configuration.html

Thanks for these precious tips. I will come back to report. I have watched the video you mentionned but I did not understand every details.
Guy

Hi Chris,
OK for adjusting the values of IM_STAB_COL_X which give the related positions of the swach in stabilize flight mode.

I cannot change the value of ATC_RAT_xxx_VFF; When I try to vary the preset value to reach the figure you recommend (0.15), the system reject the modification with “bad value” message.

Besides, with H_CYC_MAX set to 3000, I have some reaction of the swach for attitude correction but slow and late compare to the hely leaning action.

Your advice please.

Guy

You need the VFF to get it to work right. What ground station are you using, and what page in it, that won’t let you set the VFF values? That doesn’t make sense. Those don’t even exist for multicopters and the range specified in the code for those params is up to 0.5.

Hi Chris,

I use the mission Planner 1.3.55 build 1.3.6660.28588
The preset values for ATC
on “Full Parameter Tree” page are :
ATC_RAT_PIT_VFF = 0.06
ATC_RAT_RLL_VFF= 0.06
ATC_RAT_YAW_VFF = 0.024

When I try to modify these values even by a little step (i.e. 0.07 or 0.05) the message “bad value” is displayed. The change is rejected.
Thanks

Don’t use the full parameter tree instead use full parameter list. That should not reject any inputs and you should just be able to write the parameters to the pixhawk

Yes, try Bill’s suggestion. If that doesn’t work try QGroundControl - it is a much easier to use ground station

https://docs.qgroundcontrol.com/en/getting_started/download_and_install.html

Hi Bill,
I will follow your instruction and report the result.
Thanks

Hi Chris,
I will first try to modify the ATC parameters within the Full parameters list (Bill’s instruction) and experience the QgroundControl. Will report.
Thanks

Hi Bill,

When I modify the value of ATC_RAT_XXX_VFF parameter within the full parameter list, the change seems working, without any alarm, but the corresponding box becomes red. I push tthen the “write parameter” without any counter indication. When I switch to another page and come back to the full parameters list page, the parameter I thought changed, actually kept its original value. In fact, the change is not possible.
Regards

As I wrote to Bill, I cannot change the value of the parameters you indicated, even using the full parameters list. May be there are other parameters to change prior? I confirm that I am In stabilize mode.

After arming the system I get this behavior of the swash plate and the Yaw servo:

  • When I lean the heli for a small angle, nothing happens. Just the servos growling.
  • When I lean the heli for an important angle, the swash does not react immediately. But after almost 2 or 3 seconds, the swash releases suddently to reach the corresponding angle, on the good direction to counter my action.
    I am afraid it is not a right servo-control behavior.
    What to think about?
    I will try to use the Qgroundcontrl.
    Thanks

Yeah, try it with QGroundControl and see if you can change the VFF values. I have not heard of a problem (yet) with the Full Parameter List in MP not allowing the change.

Hi Chris,

By using QGroundControl I have succeeded to modify the ATC_RAT_XXX_VFF parameters to 0.15. The reaction of the swash plate to balance the heli movment, seems to be correct but I don’t know how far I have to increase these parameters to have a reasonnable compensation without twitchy servo. For instance, I increased the yaw parameter from 0.024 to 0.20 to get reaction of the tail servo.
I watched several times your effective tuto videos.
Thanks

Good to hear QGroundControl worked for you.

In all cases I’ve seen so far, 0.15 VFF is adequate to provide control of the helicopter for tuning the rate PID’s. The VFF will not cause twitchy servos. You can set it as high as 0.5 and it just makes the servos respond faster.

If you have the heli in a flyable state you can refer to the tuning wiki on how to proceed with tuning it
http://ardupilot.org/copter/docs/traditional-helicopter-tuning.html

It is confusing as to why Mission Planner’s Full Parameter List refused to make the setting for you. I thought that should always work. But if you have QGroundControl now it will not be a problem anyway making your settings.

Thanks for your encouragement that push me to continue on setting and tuning up.
Keeep you informed.
Thanks

Hi Chris,
I performed a check on ground of the heli, which shake a lot without rising up from ground, even with throttle stick at mid. In fact I found the swash pitch remains negative (-1°) until mid throtle, whatever the setting of IM_STAB_COL_2&3; I have not succeed on setting the pitch ramp.
So, I would like to use the features of my Tx instead, for setting the ramp of the throttle and the pitch.
Is it possible? If yes,how to? Thanks for your precious help again. Guy

Guy, on your last parameter file I looked at, you still did not turn up the throttle curve high enough - you are pulling too much pitch because the headspeed is not right. The H_RSC_THRCRV_100 needs to be 100% throttle and tune the other points so you get 1,160 rpm headspeed at light on the skids and in hover. And it holds that headspeed doing a full-collective punchout. That is what the GX9 requires to fly.

Using a transmitter throttle/pitch curve will NOT work. You will crash your heli as soon as you switch to Loiter or Auto with no governor because the RC collective is totally different in Loiter. The software needs to control it.

Please review the setup for throttle and pitch with piston or turbine engines - it is the fourth video in the series.

http://ardupilot.org/copter/docs/traditional-helicopter-configuration.html

Plus an additional video on fine tuning the throttle curve that I did:

Thanks Chris for pointing out what is wrong in the setting of the throttle curve parameter, about which your video is highly instructive. I will review that setting and will report the result.

Hi Chris,
Among my parameters list, H_RSC_THRCRV_100 is not displayed!
Besides, in stab mode, I have to set IM_STAB_COL_1 to maximum 600 to have 0° for swash pitch. So, the pitch curve is flat until throtle stick at mid.
I have not found in QGroundstation how to record the settings file in order to communicate to you.
Thanks