Dual-motor tailsitters

@tridge That last flight was on latest master, so it should have had 400Hz ESC outputs, and mavproxy claimed I was in qstabilize and qhover mode, not fbwa. Is is it possible to hover in FBWA mode? The motors were spinning when armed, which is not the case in FBWA. I did at least 6 takeoffs and upright landings in that log.

I"ll have to pay closer attention to system status. I don’t know why there was no GPS lock; maybe the cable is damaged. Will have to get the pre-arm checks working properly; do they require just a 3D fix, or are there also constraints on hdop/vdop as in PX4?

there are quite a few constraints, and not just on hdop. See this function:

First Takeoff ended as Flip vorward. (No transition in low level:slight_smile:)
After analysing Log and video I think it was my fault.
Due to verry slow (carefully) increasing throttle the Tailsitter tilted forward, the elevons couldn’t not correct it, because the landing gear out of the winglet (2mm carbon) where stuck to the ground.(good to see in the pic)
And then immediatly increasing the throttle was to late probably not enoughe power to lift with this angle.
Video: https://www.youtube.com/watch?v=-l7qmgBgiQc&feature=em-upload_owner
Frame OK, Props damaged.
So, the conclusion: Full power for the takeoff.
Or other advice?

@lorbass Yes, takeoff is a bit difficult with this kind of tailsitter. I throttle up slowly till I’m sure the motors will respond quickly, then do a jump takeoff by (nearly) firewalling the throttle. You definitely want to clear the ground quickly with a lot of thrust for elevon control. Also don’t back off the throttle too far after you get airborn, try to avoid quick descents until it’s tuned well.

I did something similar with the “landing gear”, but used pivoting legs to avoid breakage during horizontal landings: https://goo.gl/photos/aLYKJQJtRoqs9sGs9

@tridge I think my mode changes weren’t getting logged reliably. Seems there are a lot of dropouts around mode changes: https://drive.google.com/open?id=0Bw3digSMQXDuaGVBZkVReklpNjQ
I always arm in QSTABILIZE mode, then switch to FBWA to disarm. The 10 second disarm delay is quite inconvenient during testing.

Hi, Tridge… gray is sitting here with no controller ,is it easy,or possible to get pixhawk working with tailsitter tilt vector s/w I can’t get it to conn. after it loads, that would allow me to work/tune with hover and fbwa

@lorbass Still learning the log analysis tools for ArduPilot. Here’s a plot of my last tailsitter takeoff in qstabilize mode (red is throttle, green upward accel, blue rel alt):

yes, the tilt vector support is in master now, so just load the “latest” firmware. Use control-Q in mission planner firmware load screen.

There could be several reasons for that. What is the main LED doing after you load the firmware? Do you have a buzzer attached? If so, what sounds does it make?
If you are connecting on USB it could be as simple as a failed microSD card.
Cheers, Tridge

off,[quote=“tridge, post:229, topic:15302”]
have a buzzer attached? If so, what sounds does it make?
[/quote]

no last 2 low tones just high beep beep after multi 3 tone

swaped sd card did not help

it’s fine if is not easy. I can do other stuff, the regular s/w loads and works

@tridge Next tuning iteration on pitch with the new motors and CG increased P, decreased FF and added some I and D back in. Felt like pitch control was improved, and yaw control seemed good enough.

https://drive.google.com/open?id=0Bw3digSMQXDuaHRHVmZqTDdMT0U

it should be easy. If you have skype of G+ hangouts I think we can sort it quickly with a shared screen if you want to try that. Ping me on skype as AndrewTridgell

Hi, my wife,( she who must be obeyed) says she will help with the skype, but is retired for the evening, we will try tomorrow?, thanks, looking foward to chatting

yep, sounds good, chat to you then!

@kd0aij
Thanks for the help.
How did you set the Param Q_M_THST_HOVER. (default 0.35)
My Throttle Stick is centered with the spring.
My copters nearly hover in center when tuned correct.
The value of 0.5 is for my Caipirinha not enoughe, next trial with 0.6.
Helps to avoid up and down as your blue curve in the log.

Why not start in Hover Mode, ist this not recommended?

My “landing gear” was intended for the first starts or better landings, only.

@tridge,
What is a “vectored Tailsitter” ?
Otto

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A “vectored” tailsitter is one with vectored thrust (motors that tilt) like the one in this post above: Dual-motor tailsitters

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And what is the advantage to load extra weight for one or two servos if it starts or lands on its tail?

A_M_THST_HOVER appears to be used only by the copter firmware. I’ll check to see whether there’s a similar parameter for quadplane.

The advantage of vectored thrust for a tailsitter is a large increase in body-frame roll and pitch authority. Also, if 90 degrees of motor tilt is available, you can take off and land with the wing horizontal: https://www.youtube.com/watch?v=koOqenMpvck&feature=youtu.be
and it should also be easy to deal with any amount of wind while in “hover” modes.

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