Fly-By Wire Control System (not SAS)

[IMLL1]

My suggestion in a fly-by wire avionics system, and I'm not referring to SAS. It could be implemented into stock or made into a mod. This way an aircraft with, say, a broken elevator or missing canard, could fly. Heck, if the system were properly implemented, you could fly an aircraft that is facing backward without the control surfaces going the wrong way, or even fly an inherently unstable aircraft!

Some background info (especially for those who don't know what an actual fly-by wire system is):

Quote

Fly-by-wire (FBW) is a system that replaces the conventional manual flight controls of an aircraft with an electronic interface. The movements of flight controls are converted to electronic signals transmitted by wires (hence the fly-by-wire term), and flight control computers determine how to move the actuators at each control surface to provide the ordered response. It can use mechanical flight control backup systems (Boeing 777) or use fully fly-by-wire controls.^[1]

Improved fully fly-by-wire systems interpret the pilot's control inputs as a desired outcome and calculate the control surface positions required to achieve that outcome; this results in various combinations of rudder, elevator, aileron, flaps and engine controls in different situations using a closed (feedback) loop. The pilot may not be fully aware of all the control outputs acting to effect the outcome, only that the aircraft is reacting as expected. The fly-by-wire computers act to stabilise the aircraft and adjust the flying characteristics without the pilot's involvement and to prevent the pilot operating outside of the aircraft's safe performance envelope.^[2][3]

 

 

From Wikipedia

 

TL;DR: Instead of the aircraft responding to the stick being pulled (or in this case [ S ] being held) by deploying elevators, the aircraft just calculates what control surface movements would actually accomplish this pitch up.

Here's a hypothetical situation to demonstrate what I mean:

You're flying an F-16, but (oh no!) your right stabilator isn't moving, no matter what you do. Now, whenever you try to pitch up, it also rolls the aircraft left. A fly-by wire system would accommodate this by also using the ailerons to stop the roll before it even happens.

Another example:

you're flying an Aeris 3A (modified to be supermanueverable), and now after pitching up to vertical, you have stalled, but your attitude is still nose straight up. You try to pitch back, and the canards face leading-edge up and the elevators face trailing-edge up. When flying normally, this would do the right thing. But because you are falling backward, it causes a new pitch down. Similarly, roll is also reversed!

To simplify it further, the fly-by wire system makes it so that the aircraft does what it thinks you want, instead of what you asked for.

 

 

 

KSP could gain so much from a fly-by wire system. Even if you don't fly aircraft, it'd still be useful. Vertically landing rockets would be so much easier because you wouldn't have to fiddle with a negative authority limiter on control surfaces.s2

[FleshJeb]

That's an excellent suggestion. In fact, the excellent Atmosphere Autopilot mod does this.

My one concern is that it will be used as a crutch for bad design, tuning, and piloting. The average aircraft I see from people is very unstable, and badly overcontrolled.

(That said, I'm a horrible aero snob.)

 

[EchoLima]

I'd love to see this integrated in stock.

On 6/13/2019 at 5:28 PM, IMLL1 said:

But because you are falling backward, it causes a new pitch down

But what if you recognize that the controls are reversed?

[IMLL1]

10 hours ago, EchoLima said:

I'd love to see this integrated in stock.

But what if you recognize that the controls are reversed?

Ok, but what if you also have thrust vectoring? They’ll cancel each other out, and you won’t move.

[Aeroboi]

11 hours ago, EchoLima said:

I'd love to see this integrated in stock.

But what if you recognize that the controls are reversed?

Real planes for which FBW is created tend not to purposely stall and thus fall backwards, ever. So why the comparison? Since FBW is created for actual planes and not KSP the point is moot.
If you are intending to stall your ksp plane to fall backward your playing the game wrong and false FBW inputs are of consequence.

AFAIK when a emergency happens beyond a specific flight plan it disengages the autopilot. The more modern the FBW is on such craft the more safety measures it has in that regard. But even all functions aren't present on dedicated payware flight sim aircraft so why babble about the perfect details when a potential new FBW autopilot version is logically a simple one. More or less a Gramax version with added tweaks, easier UI perhaps and a stock skin.

KSP's legacy is stock alike simple features with expectation of low level intuition. If your FBW errors when stalling and falling backwards you should disengage the autopilot, not ask for sophisticated code to make it do automatic switching miracles.
 

[EchoLima]

30 minutes ago, Aeroboi said:

why babble about the perfect details

I don't think I was babbling. I only asked a simple question for clarification. 

[SRB]

I wonder if KOS could be used to do this, at least to some degree.  I also wonder if it could be used to do something like this: https://pdfs.semanticscholar.org/6372/339763dbf3977cb31fe105ad09b30c29e721.pdf

 

[Gavin786]

KSP already does something similar surely?

Each aileron or control surface is correctly mapped to input without having to manually configure it.  It knows that if a control surface is behind the COM that a pitch up means the surface pitches down and vice versa.  I am actually quite impressed with it so far.

As far as a more advanced version goes that can compensate for flying at flight envelopes where your aircraft can get into a lot of trouble :

1. Yes, I would like to see scripting of some kind as a standard feature, then it would be possible to "roll your own" such features if need be.  Some aircraft in real life like F117 nighthawk etc had a very dynamically unstable airframe and did use this type of software to keep stable.  But it maybe was not a truly necessary requirement, the aircraft doubtless could have been flown without it, just that life limb and coin are at stake, and having it turns a very dangerously difficult(yet by no means impossible) to fly aircraft into one that handles a lot better and more importantly safely.

2. And there are a lot of KSP designs that do require careful flying with tight flight envelopes.  That is fine.

I think the point I am trying to make is that these "Fly by Wire" systems are not essential, they are only really needed when IRL when life and limb is on the line.  In KSP good flying and understanding the characteristics of your aircraft aught to be a valid substitute for it.  Your aircraft will stall at a given speed and AOA.  Make sure that does not happen.  Understand where when and why.  In life yes a computer should do it to protect limb and property but in KSP good flying aught to suffice.  If you truly cant fly the aircraft then it needs redesigned an no amount of assistance will help you.

AND it would also also be cool to have some scripting options there to make a more sophisticated flight control system if one wished.

3. There is a great mod, https://spacedock.info/mod/1927/Kerbal Wind Tunnel which IMHO is absolutely essential for designing and flying any type of aircraft.  Surprised it has not been mentioned in thread already.  You can see a lot about where thrust will be low and its quite surprising a lot of the time just how the craft will perform at different heights and speeds.  You can understand loads about how your aircraft will handle just by using this mod without having to go out and fly your craft.  It is superb.

Just my 2 cents.

Gavin786

Edited June 21, 2019 by Gavin786

[Nuke]

would be cool if i could override gimbals control surfaces and reaction wheels with the action axes. 

Edited June 22, 2019 by Nuke

[Flibble]

12 hours ago, SRB said:

I wonder if KOS could be used to do this, at least to some degree.  I also wonder if it could be used to do something like this: https://pdfs.semanticscholar.org/6372/339763dbf3977cb31fe105ad09b30c29e721.pdf

 

It should be able to, if you set up the control loops correctly.

[SRB]

Now that I think more about it, stock SAS is pretty good.  However, it would be nice to be able to combine it with trim, to manually apply more of one control surface while keeping the other SAS-controlled, and to set a new neutral position in case of wing/control surface damage.  Also, it should be able to let me manually alter a a control surface’s position short-term, so that I can apply node-down elevator, for example , to recover from a stall without losing help in the other axis.

[IMLL1]

On 6/20/2019 at 11:42 PM, Gavin786 said:

KSP already does something similar surely?

Each aileron or control surface is correctly mapped to input without having to manually configure it.  It knows that if a control surface is behind the COM that a pitch up means the surface pitches down and vice versa.  I am actually quite impressed with it so far.

As far as a more advanced version goes that can compensate for flying at flight envelopes where your aircraft can get into a lot of trouble :

1. Yes, I would like to see scripting of some kind as a standard feature, then it would be possible to "roll your own" such features if need be.  Some aircraft in real life like F117 nighthawk etc had a very dynamically unstable airframe and did use this type of software to keep stable.  But it maybe was not a truly necessary requirement, the aircraft doubtless could have been flown without it, just that life limb and coin are at stake, and having it turns a very dangerously difficult(yet by no means impossible) to fly aircraft into one that handles a lot better and more importantly safely.

 2. And there are a lot of KSP designs that do require careful flying with tight flight envelopes.  That is fine.

I think the point I am trying to make is that these "Fly by Wire" systems are not essential, they are only really needed when IRL when life and limb is on the line.  In KSP good flying and understanding the characteristics of your aircraft aught to be a valid substitute for it.  Your aircraft will stall at a given speed and AOA.  Make sure that does not happen.  Understand where when and why.  In life yes a computer should do it to protect limb and property but in KSP good flying aught to suffice.  If you truly cant fly the aircraft then it needs redesigned an no amount of assistance will help you.

 AND it would also also be cool to have some scripting options there to make a more sophisticated flight control system if one wished.

3. There is a great mod, https://spacedock.info/mod/1927/Kerbal Wind Tunnel which IMHO is absolutely essential for designing and flying any type of aircraft.  Surprised it has not been mentioned in thread already.  You can see a lot about where thrust will be low and its quite surprising a lot of the time just how the craft will perform at different heights and speeds.  You can understand loads about how your aircraft will handle just by using this mod without having to go out and fly your craft.  It is superb.

Just my 2 cents.

Gavin786

On your third point, I tried to use wind tunnel once, but I just can't make myself like it. For instance, it has a hard time actually predicting max speed. I made an aircraft with a max speed of over 2100 m/s, but it said the max speed should be about 1900 m/s. Also, stall characteristics in KSP are almost nonexistent. The only time an aircraft really stalls is when it's nose up to the heavens.

[Gavin786]

5 minutes ago, IMLL1 said:

On your third point, I tried to use wind tunnel once, but I just can't make myself like it. For instance, it has a hard time actually predicting max speed. I made an aircraft with a max speed of over 2100 m/s, but it said the max speed should be about 1900 m/s. Also, stall characteristics in KSP are almost nonexistent. The only time an aircraft really stalls is when it's nose up to the heavens.

I never saw wind tunnel present a max speed.  It shows excess thrust at various speeds and altitudes.

Its about excess thrust primarily(main display anyway), which is related to acceleration and not top speed.  For example you fly high and you have an aircraft with low drag, you then point nose down, you may very well get upto higher speed than the positive excess thrust(greyed area on the graph) but you wont be able to accelerate or maintain that speed at horizontal flying as there will be a negative excess thrust and you will lose energy until you get to the speed indicated at which you have 0 excess thrust.

11 minutes ago, IMLL1 said:

On your third point, I tried to use wind tunnel once, but I just can't make myself like it. For instance, it has a hard time actually predicting max speed. I made an aircraft with a max speed of over 2100 m/s, but it said the max speed should be about 1900 m/s. Also, stall characteristics in KSP are almost nonexistent. The only time an aircraft really stalls is when it's nose up to the heavens.

The other thing wind tunnel shows often is dual humb backed or strangely shaped flight profile.

Have you ever noticed that you are at a low speed and you just cant climb above a certain altitude, but sometimes you can ?

That is about the flight envelope of your craft and that wind tunnel shows you.  Often you can get into "traps" in the flight envelope where you just cant go any faster BUT if you went to a lower altitude, then accelerated you could break the "barrier" at which your thrust increases and you can get upto those speeds and heights.

Wind tunnel shows you exactly where these areas are and how you need to fly to get the best performance out of your craft.

I maybe post example of that later to show what I mean or maybe someone else can.  Its important information I think for most aircraft designers.

 

[IMLL1]

26 minutes ago, Gavin786 said:

I never saw wind tunnel present a max speed.  It shows excess thrust at various speeds and altitudes.

Its about excess thrust primarily(main display anyway), which is related to acceleration and not top speed.  For example you fly high and you have an aircraft with low drag, you then point nose down, you may very well get upto higher speed than the positive excess thrust(greyed area on the graph) but you wont be able to accelerate or maintain that speed at horizontal flying as there will be a negative excess thrust and you will lose energy until you get to the speed indicated at which you have 0 excess thrust.

The other thing wind tunnel shows often is dual humb backed or strangely shaped flight profile.

Have you ever noticed that you are at a low speed and you just cant climb above a certain altitude, but sometimes you can ?

That is about the flight envelope of your craft and that wind tunnel shows you.  Often you can get into "traps" in the flight envelope where you just cant go any faster BUT if you went to a lower altitude, then accelerated you could break the "barrier" at which your thrust increases and you can get upto those speeds and heights.

Wind tunnel shows you exactly where these areas are and how you need to fly to get the best performance out of your craft.

I maybe post example of that later to show what I mean or maybe someone else can.  Its important information I think for most aircraft designers.

 

The speed I reached was in level flight, not a dive.

[Gavin786]

2 hours ago, IMLL1 said:

The speed I reached was in level flight, not a dive.

Let us take this aircraft as an example.  It is very difficult to fly.

In fact it would not be possible at all without the power curve shown above.  I need to take the data from that and make a set of written instructions for myself as to what to do at what altitude.

This graph shows how much excess energy(in practice acceleration) the craft will have at different heights and speeds.

Basically this graph can be divided into two areas.  There is the spike on the left that peaks out at about 12000m and 250ms, and the other which peaks(for my purposes) at about 14000 m and 16000ms.

Now there are two ascent curves that one can fly.  One will get you to 12000m at 250ms and the other will get me to the 1600ms at 14000(which I can then use to get to orbit).

And to get to that second ascent curve is not easy, there is only a very narrow window that will get you there.  it is important to keep low, under 1000m actually before one gets to 450 or so ms at which point there starts to be a lot of excess thrust and once can begin the climb inside that red/yellow area where the aircraft has the maximum excess thrust(accelleration) to get nicely and easily to required speed. 

Now without this software and without this graph, I would posit that it would be at minimum a serious pita to get the correct flight profile to get to speed.  In fact most likely people would give up as its a counter intuitive profile.  Getting to speed of 500ms at under 1000m is generally not the done thing.

Now if one just creates purely OP craft I agree probably one could just dispense with this tool.

I like to create craft that push the envelope one way or another and this allows me to do that and see how it will perform at all altitudes and speeds without having to actually go out and fly the craft.  And more than that it allows me to find out a lot about how my aircraft will perform that I would never have found out otherwise.

It also shows me the maximum (14000m) height I need to keep and not to go higher so I can get to speed.  This craft will actually go to 32000m still using the air breathing engines and have a speed still of about 1300ms+ that allows me easily to power to orbit.  It does not mean the graph is wrong, it means it is correct.  The graph shows me the perfect place to begin my ascent to try and transform that horizontal velocity into vertical velocity to get as high as I can to power to orbit.

Why I call this an essential tool.

Gavin786

[Red Iron Crown]

On 6/16/2019 at 1:04 PM, Aeroboi said:

your playing the game wrong

Don't inflict your lack of imagination on others. I can imagine a number of scenarios where FBW functioning correctly in reversed flight would be desirable, the simplest of which is landing a tail-sitter VTOL. There are real aircraft prototypes designed to function so. 

[Gavin786]

On 6/21/2019 at 7:42 AM, Gavin786 said:

I think the point I am trying to make is that these "Fly by Wire" systems are not essential, they are only really needed when IRL when life and limb is on the line.  In KSP good flying and understanding the characteristics of your aircraft aught to be a valid substitute for it.  Your aircraft will stall at a given speed and AOA.  Make sure that does not happen.  Understand where when and why.  In life yes a computer should do it to protect limb and property but in KSP good flying aught to suffice.  If you truly cant fly the aircraft then it needs redesigned an no amount of assistance will help you.

So I had some pretty strong opinions saying this type of feature was not needed, that pilot skill etc etc could compensate for it.

After having created quite a lot of aircraft now especially with new breaking ground features I just want to say -

I was wrong.

Having some kind of feature where the motion vectors of the craft could be fed to user-programmable software system that can then control the actuators would be super useful and essential to make some designs flyable.  Especially on my dual car there are loads of things that it just cant do that it would be able to if i could program the actuators in response to vector/input. And I am sat wishing just such a feature or mod that this thread talks about does in fact exist.

Anyway, just saying having some proper fly-by-wire in stock would be wonderful, if not a mod would def be great.  A lot more craft types could be made and existing ones could fly more stably or have different performance characteristics.  And player skill and craft knowledge can never compensate for a lot of situations where a fly-by-wire system would be needed.

So I have rethought things and changed my mind by 180 degrees from above, only fair to OP and others I say so.

Gavin786

[kennyboy]

this is all fine.  lol, but could anyone direct me to a manual or some other information on "how to use and set up this mod?" as an example, my hotas throttle pack is backwards in ksp and there is no way that I've found where I can reverse the input?   

 

[IMLL1]

30 minutes ago, kennyboy said:

this is all fine.  lol, but could anyone direct me to a manual or some other information on "how to use and set up this mod?" as an example, my hotas throttle pack is backwards in ksp and there is no way that I've found where I can reverse the input?   

 

Well it’s not a mod (at least not yet), it’s simply a proposal for one. As for how to fix your HOTAS, I believe there is a preexisting mod that allows HOTASs to interface with KSP better, but I can’t remember what the mod is called.

[kennyboy]

I’m definitely confused, I clearly typed in the wrong search......

I installed FBW by linuxgurugamer, of which that mod allows for more customizable keyboard and hotas setups, and as I was trying to set my throttle up I couldn’t reverse the setting, ie it was backwards