Tailsitter Duorotor Feedback

There was a bit of head-scratching to get both the controller orientation, and RC inputs working as they should. There’s no option to set orientation as Roll 180 and Pitch 90, meaning these values had to be offset manually, which breaks the accelerometer calibration and flight levelling routines in qGroundControl 3.0.

Through tethered testing, I then found I needed to reverse channels 1 and 2 on my radio to get the correct outputs. There’s potential for this to be automated during the radio calibration, but I’m still in the process of digesting how all the code works.

Waiting for better weather to carry out test flights, but I’ve attached photos of the prototype below. Construction is out of depron foam, 3mm & 6mm carbon fibre tubes, and balsa. It took around 4 hours to assemble, but could be built a bit quicker now that I know how everything should work together. It uses extremely cheap Turnigy park flyer motors with 8x4 props, 20A ESCs with SimonK that I had left over from a previous project, 1,300mAh 3S Lipo, an old analog airspeed sensor, and a 3DR Pixhawk that will be swapped for a PixRacer once my order arrives. All up weight is 550g, with around 800g of static thrust.

Hi Guy. I am also in the process of building a tailsitter VTOL and have been looking into how I would setup the Pixhawk. I had a very similar concern as you: how does the pixhawk know what is the new level flight orientation after it transitions from tail-sitting orientation to horizontal flight orientation?

When I calibrated my pixhawk, I did it for the tailsitting orientation (i.e., with “ROTATION_PITCH_90”). So when it pitches back down after it transitions to horizontal flight, the controller will get confused and think the horizon has shifted. Can you tell me how you addressed this issue? Somewhere in the VTOL code there must be a variable that you can set to tell the pixhawk its new level orientation after transition. But I don’t even know where to begin looking.

~Glenn

Hello Everyone,

My robotics team and I have built a tailsitter with the ritewing zephyr model. We are having issues getting it to hover. Here is the link https://drive.google.com/open?id=0B7Kz1MAIsMCAY2FOT0tsLVUxWEU to the videos from our first and second tests. Any suggestions on what you guys think we are doing wrong would be helpful. I’m not sure why it’s overcorrecting so much. Thank you!

how to test this delta vtol ,I can’n find not thing different when test without Propeller between hover and fix wing mode?

Hello @generator
It would be great if you could help me out, I tried uploading the firmware and configured with rotation 270 YAW to match the compass heading and done the calibration but it doesn’t worked as expected.
Could you tell me in which configuration sholud i mount pixhawk in order to work correctly and also how to transit from multicopter to fixed wing mode.
waiting to hear from you.

A problem about VTOL transition without a air speed sensor?

I have built a delta wing ,as following Fig

.

I have set the parameters according to this two page 1)VTOL’S WITHOUT AIRSPEED SENSOR.2)TBS Caipiroshka.I have conducted indoor test and outdoor test.Now the plane can hover well .But MC-FW transition is failed !!
#The problem is:
when I Toggle transition RC switch which channel is assigned to AUX1,but the ailerons don’t response to the RC yaw and pitch input ,and then the plane is not under control.How to solve this problem?

A recent test flight, the wing can hover but switch to fixed wing mode after all channels are not reflected, I did not use the airspeed meter, please help me to see what is the reason? I have been in accordance with the S’ WITHOUT AIRSPEED SENSOR VTOL to set up, but still invalid.

I have met you this question, now the aileron and elevator is reverse, I set the pitch_90.
In addition, your motor and steering gear is connected to the 1, 2 and 5, 6 on it?

我也遇到你这样的问题了,现在副翼和升降是反向的,我设置的是pitch_90.
另外你的电机和舵机是接在了 1、2 和5、6上了吗?

Hello, everyone!

We made a Caipiroshka VTOL and carried out several test flights.
When we transited it from mc to fw mode, it seemed lost control in the roll angle of fw mode, which means the plane flied upside down before successfully transited into fw mode.

We checked the code in “src/modules/vtol_att_control/tailsitter.cpp” and finded that in Line 262-263, it is

	if (_airspeed->indicated_airspeed_m_s > ARSP_YAW_CTRL_DISABLE) {
		_mc_yaw_weight = 0.0f;

	} else {
		_mc_yaw_weight = 1.0f;
	};

I can not understand why the mc_yaw control should be closed in the transition stage.

I am also wondering whether this caused my “upside down” flight before entered fw mode.

Thanks!

The MC yaw control is disabled only for the multicopter control as above a certain airspeed this should no longer be controlled by the multicopter but the fixed wing.

It seems unlikely that yaw (which moves over the horizontal plane) could cause a flip, but tailsitters is not my specialty.

Thank you very much for your kindly help.
I understand your point and it make sense to me. however, it looks like the fw roll control will be involved if the vehicle reach the certain airspeed and a certain pitch angle. I wondering if we just reach the fw airspeed without reaching the pitch angle? what will happen?

our vehicle was not flip every time in test, but quite a lot. That makes me confused…

hi ,

I have built a caiperinha vtol, which flight mode should I use to test my first hover , is it stabilise.

also is there any documentation available to help set up.

yes you can use stabilize mode for hovering. you can find the documentation in PX4 Developer Guide for setting up. BTW, you still need airspeed sensor even for simple hovering.

hi thanks for the response, how is your project going. the Dev guide seems to stop at motor , elevon channel setup. I can’t quite work out orientation. I have my pixhawk mounted with the arrow to the nose of the plane, is this classed as no orientation or pitch 90. also I can’t quite work out how to set the transition switch is this explained anywhere, btw I have airspeed sensor fitted and calibrated. should I be able to gently build up throttle to take off , at the moment the plane just drops forward, I’m not sure if I should try to tether it and start it away from the ground. or give it more aggressive throttle at take off to clear the ground.

hi there goosewso, just watching your videos, I was wondering if you managed to solve these problems, I am just about to make my maiden flight with a caiperinha vtol and wondered if you had some tips.

@thedudevt Did you figure out what is going on. I have the same issue and as @tumbili commented below, yes my aircraft is sitting on my desk. I am using the analyzer in QGroundControl to monitor the servo output but i see no yaw response when i move the stick

also when i flip the transition switch to FW, in Manual mode i dont see and stick response being translated to servo output on the analyzer in QGC but when i switch to Acro mode i can see pitch and roll stick commands translated to servo output on the analyzer but no Yaw out again…I have absolutely no idea what is going on.

hello @PKocmoud did you solve the problem, turns out i have the same issue. Unlike the Caipirinha mine is a quad + configuration though.

@y2kare are you talking about differential thrust for FW yaw?

Yes, but not in MC mode … only for FW mode