UDB for high alt payload

[Andrius Narbutas]

Hello pilots,
returning back to my old high altitude projects, but this time - unpowered. Idea is simple - glider is mounted to balloon, lifted to 20km+ and FPV back to base. Fully legal (need to stay below 300g) and simple, but well, when going to do everything - i found that i need to put a lot more work here :P
Anyway, few versions including glider on plane and so on (for structural testing) are already done some time ago, moving forward. I'm sure that i can have reliable link (video/control) over 50km+, but still want to have proper failsafe and here standart autopilot logic fails.
What i want (ideas and suggestions too, if you have experience with similar stuff):

 - IF altitude is > 8km
 - AND IF signal is lost
 - AND IF vertical speed is negative for 20 seconds
    * move one channel (servo controlling detachment) (and keep it here for 10 seconds)
    * 1s after servo move (not waiting 10 seconds) initiate RTH procedure (WP HOME)
    * before releasing servo - check if plane is not inverted, if inverted - do not release and re-check after some time, if in normal, leved position - release and forget
 - ENDIF; ENDIF; ENDIF

Something like this, on AUAV3 - but have no idea how tasks are done (in loops?). Still no need this code - need to finish last prototype first and test it in air, but thinking about logic and failsafe anyway.
So, in short - hard task to implement such logic, or simple (again, no idea how scheduling is done on MP, not checked in code yet)?

Thanks!

[William Premerlani]

Andrius,

I am forwarding your note to Florin, who has done quite a few "balloon drop" launches of his glider.

I am also forwarding your note to uavdevboard group.

MatrixPilot has a full implementation of LOGO, thanks to Ben. I think it would be entirely possible to write a LOGO script to do what you ant. Several of UDB users have used LOGO to do similar things. For example, one user has figured out a way to do thermal seeking. Anyway, I invite them to comment.

Best regards,

Bill

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[Kees Guijt]

Hi Bill, Adrius,

Making LOGO do what you outlined should be doable. However, not all functions are implemented in LOGO.
Maybe we can work around this, or some custom code could be written.

- Do you mean RC control by "signal is lost"? This brings MP in failsafe mode.
- check if plane is not inverted: LOGO cannot detect orientation.
- timing x seconds is not implemented, but could we use an estimated airspeed for the balloon at >8km altitude, say 20 m/s?

The basic program could look like this:

// RTL Flight Plan
REPEAT_FOREVER
    IF_GT(ALT,8000)
        PARAM_SET(0)
        REPEAT(20)
            IF_LT(AIR_SPEED_Z,0)
                PARAM_ADD(1)
                USE_CURRENT_ANGLE
                FD(20) //expect to move 20 m/s, this takes ~1 second
            END
        END
         IF_GE_PARAM(20)
            FLAG_TOGGLE(F_TRIGGER)  //release
            USE ANGLE TO HOME
            FD(200) //~10 sec
            FLAG_TOGGLE(F_TRIGGER) 
            HOME
            // Once we arrive home, aim the turtle in the
            // direction that the plane is already moving.
            USE_CURRENT_ANGLE
            REPEAT_FOREVER
                // Fly a circle (36-point regular polygon)
                REPEAT(36)
                    RT(10)
                    FD(8)
                END
            END
        END
    END
END
END

Please not that like this, the failsafe will only function when triggered above 8km.

Best wishes,
Kees
Op dinsdag 27 september 2016 00:46:24 UTC+2 schreef William Premerlani:

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[Andrius Narbutas]

Thanks GliderUav! My comments below:

> - Do you mean RC control by "signal is lost"? This brings MP in failsafe mode.

Yes, but lost control signal should override default RTL (in other words - when control signal is lost - plane should not only RTL, but also do things (release from balloon, etc)
IIRC there is flag in config for that so this is not issue.

- check if plane is not inverted: LOGO cannot detect orientation.

Well, bad, but maybe i can think another idea how to check if everything goes well.
Why do i need orientation? So far, glider (flying wing actually) is mounted on 3 points (wing ends and nose) and should lift up in "horizontal" position.
(this is probably not optimal, but after getting into strong winds in high altitude, i think that just hanging wing on tail is even more dangerous, because it will be ripped from balloon by airstream)
If balloon (or it's remains - it can explode at high alt) is not detached properly - RTH with enough forward speed will cause plane to spin around wires/invert. Need some proper way to check if everything goes well (again, this is "emergency situation" - signal lost for some reason, i'm at high altitude, need to detach asap and go home) and wires are detached.
Alternative - i can do mechanical release locks - as soon as they trigger - they remain in unlocked position - but this hurts reliability i think.
Need to be sure wing is free from cables before initiating RTH, i will think about that.
 

- timing x seconds is not implemented, but could we use an estimated airspeed for the balloon at >8km altitude, say 20 m/s?

Well, nobody knows if plane is detached ;-)
Maybe it's going up at this time (balloon is fine, just signal is lost and vertical speed loss was a glitch?)
Maybe it's going down (balloon exploded)
Maybe it's stuck at one position...

Need to re-think entire logic then - maybe just do one-time locks for release, then logic is very simple:

 - IF altitude is > 8km
 - AND IF signal is lost

 - AND IF glider lost 200m altitude (not sure how reliable will be baro altitude measurement at high (20km?) altitudes - negative vertical speed over time is more reliable IMO)
    * move one channel
    * initiate RTL
 - ENDIF; ENDIF; ENDIF
 

Thanks for program, i will try to re-think logic without using time.