India’s growing research potential in control theory and implications for flight control

[Joe Shearer]

Done.

@LeGenD

You THE MAN!

 

[Chak Bamu]

@Chak Bamu @Jungibaaz were not you talking of Indians trolling on this forum. See what a good thread has turned into ? It was all started from the very first post by a Pakistani.

I am late to the party my friend & clean up has already been done. I've seen references from some deleted posts (1 from @PradoTLC that was of zero value in a technical thread).

Its sad that some infantile members try so very hard to keep this place like a kids play ground. Its a shame really. This thread could have been a learning experience to put many things in context.

Appreciate @amardeep mishra for starting this thread. I know nothing technical about control theory or FCS or FBW & this could have helped me in starting to dig more information.

 

[.King.]

I saw some interesting FCS development in India for stealth planes, using flexible wing surfaces actuated from inside the wing to remove joints entirely and have better stealth characteristics. Interesting to see how that develops in the future.

 

[Joe Shearer]

I am late to the party my friend & clean up has already been done. I've seen references from some deleted posts (1 from @PradoTLC that was of zero value in a technical thread).

Its sad that some infantile members try so very hard to keep this place like a kids play ground. Its a shame really. This thread could have been a learning experience to put many things in context.

Appreciate @amardeep mishra for starting this thread. I know nothing technical about control theory or FCS or FBW & this could have helped me in starting to dig more information.

I'm afraid indications are that we've lost him forever. He did not respond favourably to encouragement. These are scientists not interested in becoming scum-bait. Pity.

Nevertheless, hope he comes back.

 

[amardeep mishra]

I am late to the party my friend & clean up has already been done. I've seen references from some deleted posts (1 from @PradoTLC that was of zero value in a technical thread).

Its sad that some infantile members try so very hard to keep this place like a kids play ground. Its a shame really. This thread could have been a learning experience to put many things in context.

Appreciate @amardeep mishra for starting this thread. I know nothing technical about control theory or FCS or FBW & this could have helped me in starting to dig more information.

Hi @Chak Bamu ,
There are two facets of any control design: (1) Understanding the dynamics and (2) Understanding the control theory. First and foremost, one must understand the dynamics of the system. This could be achieved by going through any decent book on flight dynamics. A full nonlinear 6 DoF nonlinear model with 12 nonlinear differential equations can capture a host of rich nonlinear phenomenon such as self sustaining limit cycles, flutter etc etc. However, to understand the broad behavior of the dynamics a linearized model could be studied. This makes the job easier at the cost of capturing the real phenomenon. You may refer to various good books on the subject such as those by Nelson, Cook, Etkin, Beard/Mc'Lain etc etc.

Once you have developed thorough understanding of the dynamics, then you may proceed to control theory. It is nothing but applied mathematics. It deals with the study of flows generated by control differential equations on a differentiable manifold or in other terms how can we alter the behavior of a given system by manipulating a variable known as "control". Usually you have to alter the behaviour under various constraints, under the presence of noises, disturbances, variations in dynamics, or sometimes you have to alter the behaviour while extremizing a functional. While this is mathematically very dense, usually a simpler approach is adopted to implement flight control on a real aircraft. This involves using a linearized model to develop either a full state feedback control or PID for a certain operating point. This notion is extended for the entire flight envelop i.e., lets say you have 100s of operating points of interest in your flight envelop, you find the optimal gains for all these 100 points and then use it in your PID/ state feedback controllers. You switch from one set of gains to another as your aircraft moves from one regime to another.

There is a cool way to do it continuously via adaptive control instead of some fixed points in your flight envelop. So, in adaptive control, you learn the gains in flight to do a particular task (for instance minimizing the state error, minimizing the neural net approximation error or to ensure the Lyapunov stability etc.). This approach is very challenging and one can extract far more advanced performance from the aircraft especially in high AoA regimes.

Just as an example, Tejas uses gain scheduling in primary FBW and several more fancy controllers in other auxiliary control tasks. This FBW suite along with its ground-based test bed known as "iron bird" took almost 20 years to master and fine tune. But this taught lot of valuable lessons to Indian designers, i.e., how to fight time delays, how to fight sensor noises, how to recover the plane and bring it back to the level flight. In addition, since the control laws took a lot of time to mature, the wealth of knowledge gained overtime has found its way into other programs namely Tejas Mk2 (with delta canard configuration), TEDBF as first twin engine design and then AMCA as twin engine stealth aircraft. Another project that involves lot of advanced control development is tail-less UAV that was taxi trialed couple of months ago. Since, it is tail-less, the yaw-stability needs to be actively maintained. In addition, the control authority of eilerons/ flaps is shared between rolling, pitching and yawing.

 

[amardeep mishra]

Hi @Chak Bamu ,
There are two facets of any control design: (1) Understanding the dynamics and (2) Understanding the control theory. First and foremost, one must understand the dynamics of the system. This could be achieved by going through any decent book on flight dynamics. A full nonlinear 6 DoF nonlinear model with 12 nonlinear differential equations can capture a host of rich nonlinear phenomenon such as self sustaining limit cycles, flutter etc etc. However, to understand the broad behavior of the dynamics a linearized model could be studied. This makes the job easier at the cost of capturing the real phenomenon. You may refer to various good books on the subject such as those by Nelson, Cook, Etkin, Beard/Mc'Lain etc etc.

Once you have developed thorough understanding of the dynamics, then you may proceed to control theory. It is nothing but applied mathematics. It deals with the study of flows generated by control differential equations on a differentiable manifold or in other terms how can we alter the behavior of a given system by manipulating a variable known as "control". Usually you have to alter the behaviour under various constraints, under the presence of noises, disturbances, variations in dynamics, or sometimes you have to alter the behaviour while extremizing a functional. While this is mathematically very dense, usually a simpler approach is adopted to implement flight control on a real aircraft. This involves using a linearized model to develop either a full state feedback control or PID for a certain operating point. This notion is extended for the entire flight envelop i.e., lets say you have 100s of operating points of interest in your flight envelop, you find the optimal gains for all these 100 points and then use it in your PID/ state feedback controllers. You switch from one set of gains to another as your aircraft moves from one regime to another.

There is a cool way to do it continuously via adaptive control instead of some fixed points in your flight envelop. So, in adaptive control, you learn the gains in flight to do a particular task (for instance minimizing the state error, minimizing the neural net approximation error or to ensure the Lyapunov stability etc.). This approach is very challenging and one can extract far more advanced performance from the aircraft especially in high AoA regimes.

Just as an example, Tejas uses gain scheduling in primary FBW and several more fancy controllers in other auxiliary control tasks. This FBW suite along with its ground-based test bed known as "iron bird" took almost 20 years to master and fine tune. But this taught lot of valuable lessons to Indian designers, i.e., how to fight time delays, how to fight sensor noises, how to recover the plane and bring it back to the level flight. In addition, since the control laws took a lot of time to mature, the wealth of knowledge gained overtime has found its way into other programs namely Tejas Mk2 (with delta canard configuration), TEDBF as first twin engine design and then AMCA as twin engine stealth aircraft. Another project that involves lot of advanced control development is tail-less UAV that was taxi trialed couple of months ago. Since, it is tail-less, the yaw-stability needs to be actively maintained. In addition, the control authority of elevators/ flaps is shared between rolling, pitching and yawing.

@Chak Bamu
I edited the last para.

 

[Bratva]

I am late to the party my friend & clean up has already been done. I've seen references from some deleted posts (1 from @PradoTLC that was of zero value in a technical thread).

Its sad that some infantile members try so very hard to keep this place like a kids play ground. Its a shame really. This thread could have been a learning experience to put many things in context.

Appreciate @amardeep mishra for starting this thread. I know nothing technical about control theory or FCS or FBW & this could have helped me in starting to dig more information.

So A guy who made scathing remarks on Pakistani Engine developments is a technical guy. Nice

@LeGenD Did you happen to see the post I gave negative rate? You forgot to clean that up

Hi @Joe Shearer
I was inactive on this forum for more than 3-4 years and I decided to reopen and post something useful that would lead to constructive remarks and fact-based discussion. But no! How can I forget I am still in a forum where members have the conviction that their country can design and manufacture micro gas turbines for CM applications (*cough* WS-500 *cough*) just because some Jack happened to have seen a poster on a def expo or heard a rumour about the same. I mean the extrapolation level is extraordinary here! Anyways, I dont think I will ever comment again. Take care Joe!

And you have something to refute Pakistan is not making engines or that micro engines happens to be WS-500? From the get go you started posting on pdf, you had a habit of engaging in logorrhea on this forum, and talking from your behind when come to things across the border . Belittling whatever pakistan did. And we can see in all its glory you did that again. Guess some habits never change. Do one thing, Dont post again on a Pakistani forum. Cuz You are not qualified enough to comment on the Engine development Pakistan is making. You have jack shyte idea actually about What Pakistan is making.

you have a habit of making wild accusations. And when Pakistan proves something E.G Babur SLCM. You had to eat your shyte later on. Same is happening once again here.

Your constructive and fact based loghorrhea is just Uni-Dimensional. India did this, india did that. And Pass the scathing remarks on any and everything Pakistani. and reach to an amazing extrapolation that it is WS-500. This is some next level Extrapolation happening here. Pass me whatever your smoking. I wanna make some extrapolations too

You have been rebutted many times by @JamD , @SQ8 , @gambit @Detterent back in the day or past

Unless you had a chance to talk to same Pakistani organization, the jack did, who are making progress, don't comment or open your mouth and spread diarrhea about things Pakistanis are making.

Thankyou

 

[Chak Bamu]

So A guy who made scathing remarks on Pakistani Engine developments is a technical guy. Nice

@LeGenD Did you happen to see the post I gave negative rate? You forgot to clean that up

Well, he was provoked. Feel free to engage him to remove his misconception.

A negative rating is for a flagrant violation, not for adding information even if it contested. If anything his post gave me some material to work with. That can't be a total waste.

If we must have people from multiple nationalities on the forum, then we must also tolerate their contrary opinions on technical matters.

I respectfully suggest that you remove that negative rating. Thanks.

 

[Bratva]

Well, he was provoked. Feel free to engage him to remove his misconception.

A negative rating is for a flagrant violation, not for adding information even if it contested. If anything his post gave me some material to work with. That can't be a total waste.

If we must have people from multiple nationalities on the forum, then we must also tolerate their contrary opinions on technical matters.

I respectfully suggest that you remove that negative rating. Thanks.

Respectfully stating. You are just making excuses on behalf of that respected logorrhea and normalizing his behavior . It was a matter of when not if , that whenever he pops up, he gonna do something similar, which he actually did. Nothing technical he said about Pakistani engine development.

Difference of opinion happens when someone points out the "JACK" directly in that thread where claims are made. Not backbite. Dont belittle or make wild claims about something the respected logorrhea cant backup with. I

I guess common sense is not so common now a days

 

[amardeep mishra]

And you have something to refute Pakistan is not making engines or that micro engines happens to be WS-500? From the get go you started posting on pdf, you had a habit of engaging in logorrhea on this forum, and talking from your behind when come to things across the border . Belittling whatever pakistan did. And we can see in all its glory you did that again. Guess some habits never change. Do one thing, Dont post again on a Pakistani forum. Cuz You are not qualified enough to comment on the Engine development Pakistan is making. You have jack shyte idea actually about What Pakistan is making.

you have a habit of making wild accusations. And when Pakistan proves something E.G Babur SLCM. You had to eat your shyte later on. Same is happening once again here.

Your constructive and fact based loghorrhea is just Uni-Dimensional. India did this, india did that. And Pass the scathing remarks on any and everything Pakistani. and reach to an amazing extrapolation that it is WS-500. This is some next level Extrapolation happening here. Pass me whatever your smoking. I wanna make some extrapolations too

You have been rebutted many times by @JamD , @SQ8 , @gambit @Detterent back in the day or past

Unless you had a chance to talk to same Pakistani organization, the jack did, who are making progress, don't comment or open your mouth and spread diarrhea about things Pakistanis are making.

Thankyou

Hi @Bratva
Lets get down to deconstructing what you wrote shall we? And for a second lets be civilized. If there is indeed a Pakistani designed micro turbine as you have pointed out, dont you think there would be at least:
(1) One test firing on the ground-based test facility?
(2) Some related research development resulting in publication of some sort (as highlighted by @JamD via various papers for instance there is a very good paper on terrain following by a Pakistani UAV published in some reputable Journal).
(3) Some patents.
Also, before you accuse me of belittling Pakistan, I certainly do not have any intention of belittling anyone. All I ever asked was hard facts and not rumuors.
You have no clue, my dear friend, I have been to numerous such defence expos not just in India but in Israel. I certainly do not take everything for granted.
Before you jump the gun and resort to un necessary name calling you should carefully look at my contributions in the field of control theory and my pending patents.

Also, we to this day do not know which under water platform was the Babur cruise missile fired from? In the absence of an autonomous mechanism to audit Pakistani weapons development programs (something similar to Indian CAG), there is a tendency to accept whatever video is shared by DG ISPR without even questioning the authenticity, engineering possibility etc.
My concern with the Babur SLCM to this day has been with respect to the launch platform and nothing else:
1. If the Babur was indeed fired from Agusta90B instead of a submerged pontoon, then the CM must be integrated with the fire control system of Agusta 90B. Why is this necessary?
Well, any CM requires "transfer alignment (TA)" before launch from a moving platform. The transfer alignment is a scheme that basically estimates the error model of the CM's inertial navigation system (INS) using extended Kalman filter or Sigma point Kalman filter. In the absence of comparison of the INS of a CM with that of the launch platform (the launch platform generally has a much more expensive and accurate INS), the errors in CM's INS couldnt be accurately estimated. Due to inaccurate error estimation, the drift sets in and you land way off.
Now you surely can use terrain aided navigation (TAN) such as TERCOM, DSMAC etc to correct your position (calculated via dead reconing), however such schemes are of no use over sea. So, over sea, you would have to rely on either (1) Pure INS or (2) GPS-aided INS.
In #2, the launch platform must write the target coordinates into the CM before launch. For #1, however, the launch platform must specify the target's location as observed from the launch platform (frame conversion via SO(3) rot). In either of these scenarios, there must exist a link between the CM and the fire control system of the submarine. And, I firmly believe that PN can not modify the fire control system without the prior consent of the OEM i.e., the DCNS.

 

[amardeep mishra]

Nothing technical he said about Pakistani engine development.

I am not the one who ever said that Pakistan has designed and manufactured a micro turbofan. It was you (based on perhaps def expo interactions). So the burden of responsibility squarely lies on the person making the claim with concrete evidences much like how certain other members do

India did this, india did that. And Pass the scathing remarks on any and everything Pakistani.

Actually no, whatever I say about India is based on solid verifiable evidence, tests, failures, papers, patents etc. I expect the same rigor in Pakistani development or else its IPRs rest somewhere else!

 

[Chak Bamu]

I am not the one who ever said that Pakistan has designed and manufactured a micro turbofan. It was you (based on perhaps def expo interactions). So the burden of responsibility squarely lies on the person making the claim with concrete evidences much like how certain other members do


Actually no, whatever I say about India is based on solid verifiable evidence, tests, failures, papers, patents etc. I expect the same rigor in Pakistani development or else its IPRs rest somewhere else!

I think you are expecting too much from Pakistan here. I would not want Pakistan's military-industrial complex to be so open as to invite auditing / interrogation from outside. Some things are best kept under wraps for sake of security. If that means that you have a hard time accepting claims, then so be it.

If Pakistan were to proceed as you wish here, there never would be a successful Nuclear weapons program.

 

[LeGenD]

@LeGenD Did you happen to see the post I gave negative rate? You forgot to clean that up

Sir, noted and addressed. Thanks.

 

[Al_Muhannad]

I think you are expecting too much from Pakistan here. I would not want Pakistan's military-industrial complex to be so open as to invite auditing / interrogation from outside. Some things are best kept under wraps for sake of security. If that means that you have a hard time accepting claims, then so be it.

If Pakistan were to proceed as you wish here, there never would be a successful Nuclear weapons program.

Secrecy is required for Mil. applications. I wish we had a functioning civil sector where anything from home-built aircrafts (e.g. for agriculture) to new mil- prototypes are presented at venues like Oshkosh.

 

[casual]

Wind tunnel specs? Now aware India had any high speed wind tunnels.