Chapter 478 Except Surrender
After listening to Gao Zhendong's words, Engineer Mo nodded repeatedly: "Yes, optical devices are a big problem. This optical device is extremely simple, and only needs a suitable shaking table. From a theoretical point of view, there are no major defects, and some shortcomings can be avoided. Although each shake must pass through the locking area, overall, the error of the locking area is acceptable."

To put it simply, the lockout area means that due to some reasons, the output disappears at a certain oscillation frequency, and various frequency deviations are designed to solve this problem.

The effect of dithering frequency deviation is to fill the output of this locked area through the dithering of the optical cavity itself. However, in this locked area, there is a certain deviation between the actual output and the ideal state, and this deviation is a principle deviation that cannot be eliminated. It is just that this deviation can be processed to an acceptable level.

As the earliest practical type of laser gyroscope, mechanical jitter deviation frequency has its advantages. From what can be seen, if evaluated based on the existing environment and needs, it is basically all advantages.

Gao Zhendong didn't say much, but continued to ask: "Tell me what you think of the other options."

This is the only way to compare and select options. When choosing an option, you must point out its advantages and also state the reasons for not choosing other options. Engineer Mo is very familiar with this.

"The solution of the magnetic mirror frequency deviation seems simple and has a good quality factor, but there is a problem that the manufacture of the magnetic mirror is too troublesome."

The material problem is a long-term contradiction that always plagues scientific researchers.

The magnetic mirror utilizes the Kerr magneto-optical effect to impose a magnetic field on the reflective magneto-optical material to achieve the purpose of frequency deviation. Moreover, the magnetic field does not need to be too large, so it is relatively easy to achieve and relatively easy to control.

It seems that the magnetic mirror deviation frequency is good in every way, but Gao Zhendong knows, and Engineer Mo also knows, that there is a problem with this thing: what should be used to make a suitable magnetic mirror?

Engineer Mo only knew that there was no suitable material to make a magnetic mirror, but Gao Zhendong knew more and deeper things than he did.

There are generally two types of magnetic mirror materials used in practical laser gyroscopes: metal magnetic mirror and garnet magnetic mirror.

However, metal magnetic mirrors have poor performance, and a structural contradiction will form between the frequency deviation and the reflectivity, which is roughly the relationship between x and 1-x. This is very difficult to maintain. When the requirements are high, it is even impossible to find a balance between these two properties.

It's not that it can't be used, but it has no future. It doesn't have much advantage over the existing gyroscopes. In fact, under our technical environment, it's really adding insult to injury. It's likely to be worse than a mechanical gyroscope overall.

If the garnet mirror is processed well, it will be much better than the metal mirror. There is no direct relationship between the frequency deviation and the reflectivity. But there is a problem with the garnet mirror: it cannot be made for the time being!

To make this thing, we need to use isothermal liquid phase epitaxy technology. It is a little ahead of the times to consider this matter at this time.

Seeing that Gao Zhendong just nodded and said nothing, Engineer Mo continued to express his thoughts.

To be honest, at this point, Engineer Mo is already very impressed and fortunate to have Gao Zhendong.

Even though he explained all the plans in a very logical manner and performed various theoretical analyses skillfully, in fact, all these things came from the more than 100 pages of materials that Gao Zhendong gave them last time, including these plans, which were all written on them.

Without this, there would be nothing to talk about. Now I guess we have basically no theory at all, a complete blank, and we don’t even know where to start.

Gao Zhendong's previous life: There was a reason why we didn't develop the laser gyroscope until the 80s.

"The main problem with the quad-frequency differential laser gyroscope is that the system is too complicated. The light-combining system used for readout is also much more complicated than the mechanical dithering system. The post-processing circuit needs to process the data of two gyroscopes at the same time, which is also complicated."

Four-frequency differential and mechanical jitter are different. This thing is actually two orthogonal circularly polarized left- and right-rotating gyroscope signals in a gyroscope. Simply put, it is regarded as a pair of gyroscopes with opposite characteristic parameters.

As a dual gyroscope, the method it uses to solve the locking zone is different from that of mechanical dithering. Mechanical dithering is to fill it, while this method avoids it. It pulls the frequency deviation points of the left and right rotating gyroscopes far away from the locking zone, and then determines the rotation state through the output difference of the two gyroscopes.

In this way, there is no need to consider the error problem in the locking zone. Correspondingly, the cost is not small. New error terms will be introduced, and the complexity of the optical path is far beyond that of the mechanical jitter offset gyroscope.

If the optical resonator part of the simplest mechanical dithering frequency-biased gyroscope only requires three basically stationary optical devices, then the four-frequency differential gyroscope requires at least six under feasible conditions.

The reason why it is basically unchanged is that both require piezoelectric devices to accurately adjust parameters such as the optimal cavity length. Mechanical dithering requires one, and four-frequency differential requires two.

The troubles brought to the system by the increase of devices are not simply a multiple relationship, and the components in the cavity will also cause backscattering and loss.

Therefore, the four-frequency differential has a kind of daunting beauty. Everyone's psychological process when seeing it is probably like this.

This thing can avoid the lockout zone? Oh, good, this is good! What? So complicated? So many parameters affected? Forget it, forget it, I can't afford it.

But what’s interesting is that our first laser gyroscope is this!

And it continues to do so.

Isn’t it hard to imagine?
Specifically, it began to appear in the early 80s. To be honest, how much higher was our technology level in the 80s than in the mid- and late 60s? Those who understand will understand.

It’s interesting why they didn’t deal with mechanical jitter at that time, but instead used four-frequency differential.

Gao Zhendong didn't know what others thought, but in his opinion, among the various schemes of ring laser gyroscope, the quad-frequency differential gyroscope was a theoretical show of skill, and it was a painstaking work that relied purely on his brain to overcome the shortcomings.

It used the method of using force to defeat skills and cleverly avoided our shortcomings at the time.

One thing most people don’t realize is that the four-frequency differential is not like magnetic mirror frequency deviation. It does not require advanced materials, nor does it look like mechanical dither frequency deviation. It does not have too high or special requirements for manufacturing and control. Its realization depends purely on the understanding of the theory, repeated scrutiny, calculation and fitting, and ultimately using the brain to carve out a path in the complex theoretical forest.

Well, the drawback may be that it is quite laborious and requires diligent study of theory and matching computing power. There are really too many things to match and calculate in the design stage of the quad-frequency differential.

Also, post-processing is a bit troublesome and requires certain conditions for the computer on the vehicle.

It just so happens that our comrades are very diligent in their studies, and as for computing power, hey, when it comes to this, Gao Zhendong is no longer sleepy.

Needless to say, for us in the 60s and even decades later, the material issue was very troublesome.

The same goes for manufacturing. This is not the case after the 21s, when we have a complete industrial system and can have whatever we need.

In 1960, we had nothing. Often, some seemingly insignificant little things could not be made. This situation existed for a long time and was widespread in countries around the world in the future.

Take a joke as an example. The ball at the tip of a ballpoint pen has become a classic joke, but in fact most countries cannot make it, except for us. The reason why it has become a joke is not because it is easy to make, but because the enemy who made the joke is stupid and we are strong, that's all.

This four-frequency differential laser gyroscope is the answer our scientific researchers gave with all their efforts in that era with extremely limited conditions.

——"They have thought of everything except surrender!"

Even so, after listening to Engineer Mo's ideas, Gao Zhendong did not ask them to switch to four-frequency differential. The scientific research freedom of the comrades still had to be respected and guaranteed. Perhaps they had some way to solve this problem?

Gao Zhendong himself is not a god. If he judges that there is a problem with mechanical vibration, then there must be a problem? Not necessarily. We still have to trust our comrades first.

He nodded. "Well, initially, I basically agree with your choice of solution, but you need to do a good job of research, fully master and understand the supporting technologies required for the mechanical jitter frequency deviation method, and do in-depth study and research on the relevant theories of laser gyroscopes, just in case."

Engineer Mo understood his implication: "Chief Engineer Gao, do you mean that there might be a problem with the mechanical vibration?"

Gao Zhendong did not try to be mysterious and nodded: "Well, I am worried about whether our supporting manufacturing capabilities can make this mechanical shaking table."

If simple control is still easy to deal with, then the manufacturing and status collection of the jitter table is what Gao Zhendong is worried about. Even if there is no control and only fixed jitter parameters are output, with the current manufacturing capabilities, whether the required jitter state can be faithfully reproduced is still uncertain.

This is different from the lithography machine worktable, which does not take volume or weight into account and is not a fully dynamic system. This thing has requirements on size and weight, and it keeps shaking.

People who often do handicrafts know that it is not easy to make something big, and it is also very difficult to make something small.

After listening to Gao Zhendong's explanation, Engineer Mo was very impressed: "Chief Engineer Gao, you are indeed someone who has been working in the front line of application for a long time. You have considered these aspects much more thoroughly than we have. We will definitely follow your requirements and pay attention to these aspects at all times."

He was not ready to abandon the mechanical jitter frequency deviation technology and turn to four-frequency differential now. The main reason was that the advantages of this thing were so numerous and visible to the naked eye. As for the disadvantages, to be honest, they could not be felt unless it was done that way, or it felt like they could always be solved.

(End of this chapter)