Transition tuning parameters help

ArduPlane Plane 4.5
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1

Hello community,

I would like some help in finalize the tuning of my VTOL plane.

I will add further details on request but following is a good summary:

  • Tricopter configuration with 2 vectored front motors
  • A tail
  • 800mm wingspan
  • 4s1p Liion powered

I’m quite happy with the “quad” tuning and the “plane” tuning. In both configuration it is quite stable and precise.
My issues are during transition.

While going from quad to plane sometimes fails as it can’t reach minimum flying speed.

  • Front motor are powerful enough, in plane mode max throttle is limited to 75/80% ish and usually plane flies with 30-40% throttle.
  • When manually flying I transit from Q_Loiter to FBWA.
  • I tried to transit with throttle centred or trying to increase the throttle while transitioning in order to give the plane more power but sims no difference.
  • minimum flying speed can’t be decrease otherwise too close to stall speed.

While going from plane to quad, there is a sudden pitch up movement with a gain of altitude of about 5-8m.

  • Transition is FBWA to Q_Loiter or Q_hold

Let me know if you need further data.

2

@andyp1per apologies for the tag as I didn’t receive any support

3

Post a log. Back transition is usually more hairy than forward transition.

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4

Interested in that as well. Facing similar issues with a non-vectored tailsitter here Help with tailsitter transition oscillations.

5

here is the folder with few logs.
https://drive.google.com/drive/folders/1f5aN0wsv7abh6TK1xztd7z1ynfvvYfUU?usp=sharing

6

I am having similar issues, check WP_SPEED. I think this needs to be set to a value that forces transition. I am playing with the same, I had my value too low, 5 m/s or so, just set to 12 m/s and the plane went to that. I need to get back out to the field, I’m going to set the value to something like 18 m/s or so.

7

Did you autotune the fixed wing? The gains look very high and are absolutely dominating during transition. I think you have the classic issue of the VTOL controller fighting the fixed wing controller.

8

Thanks for your reply. No auto tuning, I don’t like it at all. All done by me.

I like the UAV to be quite “rigid” and precise.

What is your suggestion then ? What I shall reduce?

9

I think you should try a fixed wing autotune and see what that gives you. If I had to summarize the key to a successful quadplane tune it would be “compromise”. Generally the tune that you might do for fixed wing or VTOL individually will be too aggressive for good quadplane performance, so you need to find that middle ground where both are tuned enough but not interfering too much with each other.

10

I got your point but I don’t understand the reason behind.

While transitioning from quad to plane the only issue I have is the minimum speed for complete the transition is not reach.

While transitioning from plane to quad the plane pitch up (I can suppose) because I change from fbwa to q_loiter and the system “demand” to stop the system as fast as possible.

I can even suggest that maybe for some VTOL we should implement a more gentle brake during transition, similar to position hold for quadcopters or a relaxed loiter_jerk setting.

For example last week I tested a more traditional quadplane with 4 non tilting motor and a tractor engine. And despite being a non tilting configuration, the guy suggested to never use q_loiter to perform transition for a similar reason.

Just to clarify, I could be absolutely wrong in my statement. What I can say is that I quite like how my plane flies as plane and as quadcopter.

11

It’s possible your motors are not tilting enough to reach transition speed. Here are the tilt parameters from my ranger:

Q_TILT_ENABLE,1
Q_TILT_FIX_ANGLE,15
Q_TILT_FIX_GAIN,0.1
Q_TILT_MASK,3
Q_TILT_MAX,60
Q_TILT_RATE_DN,20
Q_TILT_RATE_UP,20
Q_TILT_TYPE,2
Q_TILT_WING_FLAP,0
Q_TILT_YAW_ANGLE,15

The pitch up is almost certainly a tuning issue, you should be able to transition to qloiter just fine - there are parameters that control the transition speed.

What I can say is that I quite like how my plane flies as plane and as quadcopter.

I don’t doubt it, but that is not enough

12

Many thanks for sharing your parameters, I will try to do more testing and tuning on the transition.

You mentioned about parameters that control transition speed, can you highlight them ?

I much appreciate your support

13

https://ardupilot.org/plane/docs/quadplane-transitions.html#transition-to-a-vtol-mode-from-fixed-wing

14

Just an update on this topic. I finally had the chance to test my VTOL plane with updated parameters.

I would say that reducing tilt rate from 80 to 20 and max angle to 60 has massively improve VTOL to plane transition and helped on the opposite while increasing transit time for the pitch from 3 sec to 5 has improve the transition from plane to VTOL!

Thanks for the support

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