LibrePilot Forum

General Category => General Discussion => Topic started by: Filippo94 on April 07, 2016, 09:16:41 pm

Title: Inverted Rattitude?
Post by: Filippo94 on April 07, 2016, 09:16:41 pm: Hi guys, just a thought. Since with Rattitude mode it's possible to flip your model, yet having it self balancing when leaving the sticks, have you ever thought about a variation of Rattitude that allows for Variable pitch helis or quads to self-level in inverted flight, if it's closer to being up-right?

To me it looks not like something "revolutionary", so I think someone already had the idea and decided not supporting it. I wonder, what could be bad sides of a similar way to fly?

Usually Attitude is suggested for people who are learning to fly, so that they can safely leave the sticks to regain control of the model. Of course this is not the only way to use Attitude, but when you get better you could try Rattitude or Rate, to have complete control over the model's orientation.

Thinking as a heli user, when you start doing flips (let's keep the simulator out for now) or inverted fly, you have not the same tools that the CC3D offers to learn the up-right way, having to deal with a quite dangerous Rattitute (which I think would be completely unsafe to use in inverted flight) or Rate, where you of course have to be able to handle instinctively all the situations.

Of course it's not a request, just a consideration on the matter, and an argument on which to discuss :).
Title: Re: Inverted Rattitude?
Post by: f5soh on April 07, 2016, 10:33:07 pm: What you find is CruiseControl, nothing related to Rattitude.
Rattitude return always to level, not inverted.

https://librepilot.atlassian.net/wiki/display/LPDOC/Cruise+Control

InvertedThrustReverse should be set to Reversed
InvertedPower to Normal (Throttle stick)
You need to be brave, reversed options are untested for what i know :)

Edit: Currently CruiseControl is not allowed with Rate modes so you cannot test inverted using CruizeControl
Title: Re: Inverted Rattitude?
Post by: Filippo94 on April 08, 2016, 03:01:54 pm: Nope, Cruise control allows to keep the same altitude just by adding trust according to the tilt, from what I've understood. What I'm talking about is a completely different thing. If you flip the model, and it is upside down, and you let the sticks, in Rattitude it would flip again to self level, right? What I mean is that instead of trying to level the model the up-right direction, since it's inclination is past 180° according to the accelerometers, it will from now try to self level it upside down, so if you let the sticks it will stay in inverted hovering, untill you manually get past 180° again, so it will self level the normal way.

Inputs are not inverted at all, when the model is upside down, you still have to give it the right inputs, like if you were in rate, but instead you get a bit of self leveling, so if you loose control, the model has much more possibilities to restabilize itself, rather than trying a flip, which could even be too late.
Title: Re: Inverted Rattitude?
Post by: Mateusz on April 08, 2016, 03:10:54 pm: Maybe you are talking about AlwaysStabilizedWhenArmed https://forum.librepilot.org/index.php?topic=1246.msg9116#msg9116
Which is not very safe, and you should be careful.
Title: Re: Inverted Rattitude?
Post by: Filippo94 on April 08, 2016, 04:14:01 pm: hmm, that looks again like another thing, which lets you have the quad self leveling even if there's no throttle. That's again another thing, not what I'm talking about.
Also I'm talking about a vehicle which is able to fly inverted, and usual quads which you are referring to are not able to fly inverted.

Here there are some example of inverted flight capable models:

https://youtu.be/TnGhEInTXYc?t=4m1s

https://youtu.be/pMiv-Kn24YE?t=10s

Here you can see these models are actually able to fly inverted. They're not the only ones, of course, it's just an example. What I'm talking about is a Rattitude mode that levels the model upright when its "Z axis" (the vertical one) angle distance compared to the gravity vector is less than 90°, and levels upside down when the angle distance is more than 90°.

(https://dl.dropboxusercontent.com/s/dl0pdgg04drmrit/2016-04-08_16-13-06.gif?dl=0)

Just to clear out, this should not act on the thrust vector (throttle or pitch), but on the ciclic, handling pitch and roll to stabilize the model the same way Rattitude does, but also inverted when the circumstances require it.
Title: Re: Inverted Rattitude?
Post by: Mateusz on April 08, 2016, 05:03:29 pm: I am not sure if current firmware has feature to support variable pitch aircrafts in a way to allow flying them up-side-down in case if you can have negative pitch. Maybe someone else knows, if it's not possible yet, would be pretty cool feature to develop.
Title: Re: Inverted Rattitude?
Post by: @marc on April 08, 2016, 05:29:13 pm: On a quad with fixed props you'd have to reverse the motor directions. Some toys can do that (Floureon 101), but I am not sure if that's possible with big, ESC controlled motors.
Title: Re: Inverted Rattitude?
Post by: Filippo94 on April 08, 2016, 05:47:01 pm: Every motor has usually an ESC driving it. I agree though, bigger props might have a really hard time inverting their spinning at a valuable speed. Also the Nano QX 3D (https://youtu.be/gfqrfA0gr-g?t=1m) inverts its motor direction to fly inverted.

That opens another discussion: Do ESC need a negative value to make the engine spin at negative direction? Or would them work out of the box with the CC3D and usual output? Shouldn't the CC3D output oscillate around 0 (-1/1) or 0.5 (0/1) to make it work? At take off engines would need a middle value to stay still...

Yet there's no way to bring Rattitude upside down during flight, even with a 6ch heli which would already be capable of inverted flying with current software. (I'm speaking about Rattitude and not Attitude because with Attitude it's not possible to flip the model, hence swapping from normal to inverted fly)
Title: Re: Inverted Rattitude?
Post by: liftbag on April 08, 2016, 10:22:55 pm: Quote from: Filippo94 on April 08, 2016, 05:47:01 pm
Every motor has usually an ESC driving it. I agree though, bigger props might have a really hard time inverting their spinning at a valuable speed. Also the Nano QX 3D (https://youtu.be/gfqrfA0gr-g?t=1m) inverts its motor direction to fly inverted.

That opens another discussion: Do ESC need a negative value to make the engine spin at negative direction? Or would them work out of the box with the CC3D and usual output? Shouldn't the CC3D output oscillate around 0 (-1/1) or 0.5 (0/1) to make it work? At take off engines would need a middle value to stay still...

Yet there's no way to bring Rattitude upside down during flight, even with a 6ch heli which would already be capable of inverted flying with current software. (I'm speaking about Rattitude and not Attitude because with Attitude it's not possible to flip the model, hence swapping from normal to inverted fly)

Ciao Filippo.

Flyduino ESCs can change spin direction, some of them are optimized for fast inversion (3D version). BLHeli too has the 3D option (fast inversion) on suitable ESCs.
To activate 3D mode you have to perform a proper calibration, described in the ESC manual.
When 3D mode is active, on regular pwm the neutral pulse is 1500 µS. If you go higher (1500-2000) motor spins regular, if you go lower (1500-1000) motor spins inverted.
We don't have an inverterted flight mode. I think cleanflight has it, and 3D is one of the three flight modes available with KISS flight controller. Don't know if cleanflight has the autolevel inverted flight mode, what I suppose you mean with inverted rattitude.
Title: Re: Inverted Rattitude?
Post by: Filippo94 on April 08, 2016, 10:53:26 pm: So the ESC needs to behave accordingly, rescaling their range, and the controller has to be aware of having the possibility if inverted trust. It's needed collaboration from both.

About the self leveling, I was thinking that other than bank angle, would be useful to take angular velocity into account. Think about a flip, but you leave the sticks just a bit too early, the model will try to level out about 90° of banking, inverting the current rotation, maybe even not being fast enough, and thus going past 90°, where then the stabilization would be flipped all of a sudden, causing some strange oscillation in one of the most dangerous positions...
Title: Re: Inverted Rattitude?
Post by: liftbag on April 08, 2016, 11:03:22 pm: Quote from: liftbag on April 08, 2016, 10:22:55 pm

We don't have an inverterted flight mode. I think cleanflight has it, and 3D is one of the three flight modes available with KISS flight controller.

Just to clarify. I speak of multirotor. You can fly inverted with helis as with any flybarless controller, but not in autolevel mode.