Gliding airspeed control

[crashmatt]

Gliding airspeed control option has been added to trunk for those who like to fly engine off.  This might also be useful for better RTL and autolanding control.

It was flight tested today with excellent results.  It nicely fixed airspeed at near minimum sink enabling great thermal tracking.  So very good that I really can't share the datalog.

It was not completely without trouble.  In turbulent air the low airspeed resulted in stalling.  RTL resulted in a series of tip stalls in the general direction of home.  Variable desiredSpeed dependent on flight condition will fix this.

If anyone wishes to test this feature, I suggest adding some control of desiredSpeed using logo and a suitable RC input.  In the long term I will be adding some hard coded features to fix this.

The gliding airspeed control feature is enabled with an option, not a flag. It can't be enabled/disabled with Logo or a switch. This can change if needed.

[Riccardo Kuebler]

Hi Matt,

could you please explain which condition triggers gliding airspeed ?

Btw today I had the very first real thermal flight with my LOGO program. More than 100m gained autonomously and then some more while switched to RTL :O
Thermals appear very seldom in the field where I usually fly.

No, not the Proxima II, the Easystar !

Best regards,

Ric

2012/7/3 crashmatt <uavfligh...@gmail.com>

--

[ben levitt]

Awesome! :) It's really exciting to hear everyone's ideas and
achievements using LOGO flightplans. Also, a quick request that if
you make a cool, general, reusable LOGO flightplan, then please do
send it to Ric for his repository of LOGO flightplans!

Ben

> --

[Daniel]

Hi Matt.

Quick one: Is this a function that can be flagged on and off? Sample script pls.?

I've worked in my Logo some speed controls (e.g., Speed_increase, set_speed(x), etc.) for patterns for my gliders
(including Ric's thermal lib) but being my first try, am not exactly sure how this will work.

Probably will try it first with Hillsim.. as prev. suggested.

Many thanks in advance.
All the best.
Daniel

[crashmatt]

Daniel,

It can't be flagged but it is only active during stabilize/auto when the throttle is low.  We can change this.

The set_speed(x) did not work before when gliding, only during powered flight when within the linear height gain margin.  HILSIM is definitely the right place to start.

My plan is to have the airspeed set by the camber setting but then modulated by the pitch/elevator.  The elevator would then be removed from direct control.  When gliding you will generally get the correct airspeed for your flap setting but then you have the option to trim airspeed with elevator.

Regards Matt

[Daniel]

Thanks again Matt for the clarifications.

Planned enhancements sounds exciting, as they, if I understood them correctly, parallels an aileron/flaps and elevator mixing
and will be auto invoked/modulated by a logo flight plan defined and/or captured airspeed (or any condition) parm. And this
likewise, could be under different Logo routines and flight patterns, conditional and/or user switched.

WOW, can't wait for these to become available. 

Right now, FYI,  as a pilot prj.,  I'm embellishing a Ventus (2.4m) foam glider with UDB4 from UDB3.  This glider has ailerons
and separate flaps, currently mixed for: crow, flap-elevator pitch, full aileron, and camber and reflex custom mixes (in my
MPX TX) activated under different flight modes.. Main wing profile is narrow, but airfoil as well as wingloading is such it can also
catch/float on quite a bit of thermal (when strong enough).

Crow can really slow down an otherwise fast approach and gives me very predictable control during approaches and
landing.

Perhaps a crow function or mix option might also be worth considering downstream..

I've flown this with a vanilla UDB3 and I still have to work out some kinks to iron out certain behaviors that didn't pan out well
under waypoint... otherwise stabilized works well.

Kindest regards.
Daniel

[crashmatt]

Daniel,

I would not trust mixing or any other control loop activity to logo.  This does not mean that logo is bad.  Logo is run at a relatively low priority. It is great for making route plans i.e. what pattern to fly and at what airspeed. You also don't want to mess up your mixing while editing a flight plan.  The two things should be kept separate.

Flexifunctions is the only option I know of right now to do full house glider mixing on UDB4.  This is not the easiest option to get started with.

I will not be support full wing mixing in the standard options.  Doing hard coded mixers is very restrictive.  Flexifunctions is a list of freely assignable mixers where each mix has any function you can write.  I am currently using a mix of 3,4 and 5 point mixers to describe the servo paths for airbrakes.  This is simply not possible on anything but the very most expensive radios.  There is also a GUI available for trimming with flexifunctions.  With hard coded mixers you need to re-compile and re-program.

I have spoilers combined with crow on my latest model.  I have not liked spoilers in the past but I am warming up to them on this aircraft since it keeps the landing tidy.

https://picasaweb.google.com/101029894981212633965/BarkabyFlying290412#5738016246994860882 

Regards Matt

[Daniel]

Matt.

Based on your recommendations below, I'm now trying to get a basic mix working with FlexiFunctions.. not the easiest/straightforward thing to deal with, as I'm discovering, poking around with an excel sheet like interface, with a humongous amount of (undefined) parameters to cover... so I do need I think some (understatement of the year! ;o) guidance.

I've created a separate topic: "FlexiFunction questions"  which hopefully, will be a go-to knowledge base discussion for those who may be probing into the complexity but very nice utilitiy you've created for mixes, etc... I'm may be missing some links but I've also searched the online link you've previously indicated but they seem to have very scanty set of instructions.

...will appreciate it if you can a great favor of spending some time responding to the question in the topic, for starters.

Kindest regards.
Daniel