"Huh?"

It wasn't Xu Yang who made this exclamation.

In fact, she just glanced up at Chang Haonan with some surprise, and her expression didn't even change much.

On the contrary, the other 624 technicians standing next to them were looking at Chang Haonan and Xu Yang who were sitting on both sides of a table with a somewhat blank gaze.

To be reasonable, they can't be blamed for this.

The communication between these two people just now didn't even use a pen during the whole process, and it was really unfriendly to the other people around them.

Even though a considerable part of them are directly involved in the design of this simulation verification program, it is still difficult to keep up with Xu Yang's introduction just now.

As a result, the previous content has not been fully understood, and Chang Haonan's opinions have already been given.

Naturally, there is a feeling of "I bowed my head and picked up a pen in math class".

Facing Xu Yang's inquiring eyes, Chang Haonan finally picked up a pen from the side:

"The algorithm and the control logic of the verification program are fine, I mean, there are some tests that are not taken into account."

Seeing this scene, the group of people who had just been scattered around the room took a few steps forward almost uniformly and surrounded behind the two.

Chang Haonan instantly felt that the light on the paper had dimmed......

"Ahem...... Engines equipped with a full-authority digital control system are generally no longer equipped with a complete mechanical control system, so they must take into account the various operating conditions they may face, such as network-induced delays and packet loss during flight for various reasons. ”

"Needless to say, if there is a significant gap between the control command from the operation end and the response from the action end, I am afraid that no matter how good the pilot is, he will not be able to control the aircraft normally."

"As for packet loss...... For the TTCAN bus used by FADEC, if the packet fails to be sent, the protocol will only allow the reference message to be resent immediately, but the other data will not, which will significantly affect the accuracy and speed of system control, and even cause the system to be unstable. ”

Chang Haonan explained while writing the dragon and snake:

"For example, we can first analyze the simplest form of delay and packet loss, assuming that the delay is a short delay and is constant in each sampling cycle, and the number of consecutive packet losses is also capped n, then there may be two ...... in the output of the controller reaching the actuator in one sampling cycle."

“……”

"The dynamic characteristics of the engine operating near the steady-state point can be described simply by a continuous state space equation, and then this equation is discretized, and a 2n+1 seed system will appear, and the actual engine operating characteristics will jump randomly and continuously between these 2n+1 types, which will significantly prolong the convergence process of the steady-state system......"

Speaking of this, Chang Haonan stopped the pen in his hand, pushed the two pieces of paper that had been filled with formulas to the front, and then raised his head.

This calculation made the people around him directly stunned.

But fortunately, this time at least I was talking and writing, and there was a lot of content on paper, so compared to the complete confusion just now, at least a few people understood the key.

"We have a remote connection, so there shouldn't be any exaggerated latency or packet loss......

One asked with some hesitation.

Chang Haonan just drank a sip of water at this time, quickly swallowed it, and then shook his head:

"In fact, just like our normal computer Internet access, the signal transmission bandwidth of the ECU unit and cable of the engine is actually not as good as that of the home computer and network cable, so even in the normal flight process, it is normal for the problem of poor information transmission."

"So what about that...... Doesn't it mean that FADEC has a hard flaw in terms of stability? ”

The other voice was noticeably a little shaky:

"After all, the delay of the mechanical control system is certain, as long as it is adapted, and there is no possibility of data loss, but these are random appearances of the electronic control, do you still need to keep a complete mechanical system for backup?"

One of the great advantages of FADEC is the weight reduction, which is naturally not practical to keep a mechanical backup.

However, since Chang Haonan has raised this problem, there must be a solution:

"Although the delay and packet loss of the electronic control occur randomly, the impact on performance can still be reduced or even eliminated through the highly robust control algorithm."

"So when I designed the engine control program, I used a distributed control gain matrix to improve the stability margin for delay and packet loss, but how much this margin is and whether it can meet the needs of fighters under various working conditions still needs to be verified during the test process."

"If the stability margin is not enough, then it is necessary to add another engine control unit, and if the margin is excessive, it may have to be reduced by one, after all, a set of ECUs and related cables together also has a weight of tens of kilograms......"

"Distributed Control Gain Matrix...... This...... Can it be like this? ”

Jiang Fuhe, who had been sitting next to Chang Haonan just now, suddenly flashed a hint of enlightenment in his eyes.

After the R&D focus of the 624 Institute shifted to the VTOL engine last year, the biggest problem in front of him was the control response and stability of the engine in the process of vertical output power.

You know, vertical take-off and landing is not like level flight, the thrust is large and the impact is not great, if the thrust output is unbalanced in the process, the aircraft will crash directly if it is unstable and heavy.

However, the high-pressure gas in the vertical take-off and landing process has to go through a deflection of 90° or even more, and the external disturbance that may be affected is more complicated......

Therefore, the requirements for the engine control system are much higher than those of ordinary engines.

In the current testing process with the external vertical nozzle of the old turbojet 7 engine, even if the electronic control unit is used, the reliability of the vertical output process is still not guaranteed.

But Chang Haonan just gave him a complete idea.

Jiang Fuhe only feels that it is a pity that he is not an expert in the field of control algorithms, so he has an idea now, but it is difficult to implement it......

Xu Yang, who was sitting opposite, had just taken the two pieces of paper in her hand, and others were still asking questions, and she had already read the above content quickly:

"In this case, I just need to add a packet loss and delay simulation to the test control system...... And essentially, packet loss can also be equated to the input delay of the engine......"

"Therefore, it can be assumed that there is a delay at the input of the engine that increases synchronously over time, so that the control input signal received by the engine is only related to the measured value......"

"Of course, the result of this method is the maximum number of consecutive packet loss allowed by the system, not the packet loss rate, so it should be fine, right?"

"Yes."

Chang Haonan nodded decisively:

"With the maximum number of consecutive packet loss, you just need to change the limit parameter setting logic a little, which is a completely independent unit, and it is only a matter of a few hours."

"Then wait for my news, and I'll get it for you in two days."

Xu Yang threw the two pieces of paper on the table, stood up and named several engineers from the 624 Institute, and hurriedly left the control room with them.

"Mr. Chang."

After the room became deserted again, Jiang Fuhe found Chang Haonan again:

"Can you give us a full idea of the distributed control gain matrix you just mentioned?"

The latter was slightly stunned.

The main thing is that I didn't expect anyone to ask this kind of question.

Because it's part of the design process.

However, it is reasonable to think about it, after all, the 624 Institute is not only for aviation testing, they are also turbine power research institutions.

Even in the last life, there were many core machines that were made by 624.

It's just that now because of him, people have almost become a little transparent......

"This is actually inspired by the flight controller algorithm on the host side......"

Chang Haonan said and took the pen and paper again.

He didn't lie about it.

It was indeed inspired by the flight control program.

It's just that it's not its own flight control program, it's American's.

A huge problem with the flight control of the later F35 fighter jets is that there will be a huge delay in rudder surface control under certain flight conditions.

Until Chang Haonan was reborn, this problem had not been solved......

So when he was developing the turbofan 10 control program, he was almost the first to think of this problem.

Of course, it is impossible to tell these contents to Jiang Fuhe, so Chang Haonan changed to another version of the story.

Anyway, as long as the knowledge is correct.

Looking at the scratch paper that was gradually filling up in front of him, Jiang Fu and his heart, which was still a little resentful before, became more and more calm.

"Mr. Chang, our hospital now has a VTOL engine project at hand, you see...... When the turbofan 10 is over, are you interested in taking over? ”

People must always learn to reconcile with reality.

If you can't beat it, join it, and there is no shame......

(End of chapter)