Tandem heli how to connect swach 2 servo plates to pixhawk?

ArduCopter Traditional Helicopter
1

Hello,

II set the dual heli param, and I have one front swash and one rear swash plate.
I have on each swach only 2 servo, one left and one right.
I don’t have virtual angle.

I suppose that I can manage to use the params for each plate as generic swash 3 plate setting pos servo 1 to 90° and pos servo 2 to -90°.
I let the non used third servo on each swash plate to 180°.

But I have issue:

I tryed many servo combinations (inverting/non iverting), and I always have:
-or the pich invesed when all the other 2 swash movements are ok
-or the yaw inversed when all the other 2 swash movements are ok…

Also can you confirm that sw1 is front and sw2 is rear swash? (I also tryed to invert it but same issue…)
Also can you confirm that servo 1 on each swach are left ?
Also can you confirm that servo 2 on each swach are right ?

How I can resolve my issue?

Also I saw that on mission planner in heli setup: when setting collective and cyclic settings only affect swash1…

So swash 2 need to be set as manual?

Thankyou so much for your help.

Kind regards.

2

Swash 1 is definitely the front swashplate
Swash 2 is definitely the rear swashplate

Yes, Servo 1 is the left swashplate servo on the front swashplate
Servo 2 is the right swashplate servo on the front swashplate
Servo 4 is the left swashplate servo on the rear swashplate
Servo 5 is the right swashplate servo on the rear swashplate

Unfortunately the Heli Setup page doesn’t have all of the settings for dual heli. You need to do those in the Full Parameter Tree in the Config Tab.

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3

Hello Bill, Thank you so much.

Today i test little flight with params set following: Preparing for Tuning — Copter documentation (ardupilot.org)

I don’t broke anything, but pitch and yaw was very overcompensated, and result in large pitch forth and back movements, and yaw to larges I with this parameters.

I just see on the wiki dual heli that they are theses parameters to setup the tandem:

  • H_DCP_SCALER - Scales the differential collective output to the rotors for a pitch axis input
  • H_DCP_YAW - Feedforward input to yaw axis for pitch axis (DCP) inputs
  • H_YAW_SCALER - Scales the differential lateral cyclic based on yaw axis input. This is a positive number for this setup.

but I don’t know how to start with…
DCP SCALER is originaly set to 0,25…
DCP_YAW to 0
and YAW SCALER to 1.

Given this first flight I have the impression that the DCP scale and yaw scale gains are too strong.

Do you advise me to go with smaller gains?

Before flying in swash passthrough mode, can I already measure a blade angle according to the movements of my sticks to adjust these parameters?

Thank you very much for your help.

4

@kuspower

Determining the appropriate values for these parameters is not easy. It would be helpful if you provided a log. However, for pitch, the ATC_RAT_PIT_FF needs to be adjusted so that the actual rate (RATE.P) matches the desired rates (RATE.PDes). My guess is that the ATC_RAT_PIT_FF is too large. But I am assuming that ATC_RAT_PIT_P is zero.

Once the desired rates and actual rates match for meaningful inputs like 50-100 deg/s then you will need to look at the output pitch request (RATE.POut). You have to make sure that 50-100 deg/s rate requests don’t require a large amount of output pitch request (> +/- 0.7). I’m somewhat guessing but the point is that you don’t want to be saturating the output request for rather small desired rates. That would indicate that H_DCP_SCALAR is too small. On the other hand, you don’t want the output pitch request to be really small. That would mean that H_DCP_SCALER is too large. Hopefully this makes sense. I think the first step would be to adjust the ATC_RAT_PIT_FF until the desired rates match the actual rates. The same would apply to the H_YAW_SCALAR.

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