Chapter 478 In addition to surrender
After listening to Gao Zhendong’s words, Mo Gong nodded repeatedly: “Yes, optical devices are a big trouble. This optical device is extremely simple and only requires a suitable shaking table. From In principle, there are no major flaws, and some shortcomings can be avoided. Although each jitter has to pass through the locking zone, the overall error in the locking zone is acceptable. ”
Latching. To put it simply, for some reasons, the output disappears at a certain oscillation frequency, and various offset frequencies are designed to solve this problem.
The effect of dithering and biasing frequency is to fill the output of this blocking area through the dithering of the optical cavity itself. However, in the blocking area, the actual output has a certain deviation from the ideal state, and This deviation is a principle deviation that cannot be eliminated, but it can be dealt with to an acceptable level.
Mechanical jitter bias frequency, as the earliest practical type of laser gyroscope, naturally has its advantages. From what can be seen, judging from the existing environment and needs, basically all benefit.
Gao Zhendong didn't say too much, but continued to ask: "Tell me what you think of the other options."
This is the only way to compare and select options. To choose a plan, you must say it. It is good, and at the same time, it must give reasons for not choosing other options. Mo Gong is also very familiar with this.
“The magnetic mirror offset scheme seems simple and has a good quality factor, but one problem is that the manufacturing of the magnetic mirror is really troublesome.”
Material issues, This is a long-term contradiction that has always troubled scientific researchers.
The magnetic mirror uses the Kerr magneto-optical effect to apply a magnetic field on the reflective magneto-optical material to achieve the purpose of frequency bias. Moreover, the magnetic field does not need to be too large, so it is easier to implement and easier to control. .
It seems that the bias frequency of the magnetic mirror is good anywhere, but Gao Zhendong knows, and Mo Gong also knows, there is a problem with this thing: What to use to make a suitable magnetic mirror?
Mo Gong only knew that there was no suitable material to make a magnetic mirror, but Gao Zhendong knew more and deeper things than he did.
Laser gyroscopes use practical magnetic mirror materials. Generally speaking, there are two types, one is a metal magnetic mirror and the other is a garnet magnetic mirror.
However, the performance of metal magnetic mirrors is poor. There will be a structural contradiction between the offset frequency and the reflectivity, which is probably the relationship between x and 1-x. This is very difficult to deal with. In the requirements When it is high, there is no balance between these two performances.
It’s not that it can’t be used, but it has no future and has little advantage over existing gyroscopes. Even in our technical environment, it is really adding insult to injury. It is highly likely that it will not be as good as mechanical gyroscopes overall.
If the garnet magnetic mirror is processed well, it will be much stronger than the metal magnetic mirror. There is no direct connection between the offset frequency and the reflectivity. But there is a problem with the garnet magnetic mirror: it cannot be made for the time being!
To create this thing, it is necessary to use isothermal liquid phase epitaxy technology. It is a little advanced to consider this matter at this time.
Seeing that Gao Zhendong just nodded and said nothing, Mo Gong continued to express his thoughts.
To be honest, when it comes to this, Mo Gong is already very impressed and lucky to have Gao Zhendong.
Although he explained all the plans in a succinct manner and calculated various theoretical analyses, in fact, all these things came from the more than 100 pages of materials Gao Zhendong gave them last time, including these plans. , it’s all written on it.
Without this, there would be nothing to talk about. It is estimated that even the theory is basically 0, completely blank, and I don’t even know where to start.
In Gao Zhendong’s previous life, we did not develop laser gyroscopes until the 1980s. It was not without reason.
“The main problem of the four-frequency differential laser gyroscope is that the system is too complicated. At the same time, the light combining system used for reading is also much more complicated than the mechanical jitter. In the post-processing circuit, the two gyroscopes need to be processed at the same time. The data is also complex. "
Four-frequency differential and mechanical jitter are different. This thing is actually two orthogonal circularly polarized left-handed gyro signals in a gyro. Simply put, it can be regarded as A pair of gyroscopes with opposite characteristic parameters.
As a dual gyro, its method of solving the locking area is different from mechanical jitter. The mechanical jitter is to compensate, while it is to avoid it, pulling the bias points of the left and right gyros far away from the locking area. area, and then determine 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 blocking area. Correspondingly, the cost is not small, new error terms will be introduced, and the complexity of the optical path is far beyond that of a mechanical jitter bias gyro.
If the simplest mechanical dithering biased frequency gyroscope only requires three basically immobile optical devices in its optical resonant cavity, then the four-frequency differential requires at least six under achievable conditions.
The reason why it is said to be basically immobile is because both require piezoelectric devices to accurately adjust parameters such as the optimal cavity length, one for mechanical jitter and two for four-frequency differential.
The trouble brought by the increase of devices to the system is not a simple multiple relationship, but the components in the cavity will also bring back scattering and loss.
So the four-band differential has a daunting beauty. When everyone sees it, the general psychological process is like this.
Can this thing avoid the locked area? Oh yo, okay, this is good! . What? So complicated? Does it affect so many parameters? Forget it, forget it, I can't afford to offend you.
But what’s interesting is that our first laser gyroscope is this one!
And it continues.
Isn’t it hard to imagine?
Specifically, it began to appear in the early 1980s. To be honest, how much has our technological level improved in the 1980s compared to the mid- to late 1960s? Everyone who understands understands.
It’s interesting why mechanical jitter was not implemented at that time, but instead it was this four-frequency differential.
Gao Zhendong doesn’t know what other people think, but in his own opinion, among the various solutions for ring laser gyroscopes, the four-frequency differential gyroscope is a theoretical show-off that relies purely on brain power. An effort to smooth out the shortcomings.
It adopted the method of defeating ten with one force, cleverly avoiding our shortcomings at the time.
One problem that most people don’t realize is that this four-frequency differential is not like magnetic mirror bias. It does not require advanced materials, nor is it like mechanical jitter bias. It has no manufacturing and control capabilities. The requirements are too high and too special, and its realization relies purely on the understanding of the theory, repeated deliberation, calculation and fitting, and finally, in the complicated theoretical forest, you can use your brain to find a way.
Well, the disadvantage may be that it is more troublesome and requires hard study of theory and supporting computing power. There are too many things to match and calculate in the design stage of four-frequency differential.
There is also the post-processing, which is a little troublesome and requires certain requirements for the computer on the vehicle.
It just so happens that our comrades are full of hard work, and computing power, hehe, when it comes to this, Gao Zhendong is not sleepy.
It goes without saying that for us in the 1960s and even decades later, the problem of materials was very troublesome.
The same goes for manufacturing. This is not the case after the 2010s when our entire industrial system will be complete and everything we need will be available.
In 1960, we wanted nothing, and often small things that seemed inconspicuous were actually impossible to make. This situation has long been common in all countries in the world.
Take a joke as an example. Although the bead on the tip of the ballpoint pen has become a classic joke, in fact most countries cannot make it, but we are not among them. The reason why it became a joke is not that it is easy to make, but because the enemy who made the joke is stupid and we are strong, that's all.
And this four-frequency differential laser gyroscope is the answer that our scientific researchers, in that era of extremely limited conditions, tried their best to deliver.
——"They have thought of everything except surrender!"
Even so, after Gao Zhendong listened to Mo Gong's idea, he did not ask them to switch to four-band differential. Comrades' freedom in scientific research must still be respected and guaranteed. Maybe they have some way to solve this problem?
Gao Zhendong himself is not a god, so he judged that there must be a problem if there is a problem with mechanical vibration? Not necessarily, you still have to trust your comrades first.
He nodded: "Well, initially, I basically agree with your choice of solution, but you must do a good job in research and fully master and understand the supporting technologies required for the mechanical dither offset method. , and at the same time do in-depth study and research on the relevant theories of laser gyroscopes, just in case."
Mo Gong heard the implication: "General Engineer Gao, you mean that mechanical vibration may occur. Have a problem?”
Gao Zhendong didn’t make any excuses and nodded: “Well, what I’m worried about is whether our supporting manufacturing capabilities can complete this mechanical shaking table.”
If it’s simple. If the control is okay, Gao Zhendong is worried about the manufacturing and status collection of the jitter table. Even if he does not control it and only outputs fixed jitter parameters, with the current manufacturing capabilities, can he faithfully reproduce the required jitter state? Also in between.
This is different from the lithography machine workpiece stage, which does not care about volume or weight, and is not fully dynamic. This thing has requirements for size and weight, and it keeps shaking and shaking.
Anyone who often does handicrafts knows 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, Mo Gong was very impressed: “General Manager Gao, you are indeed someone who has been working hard in the application field for a long time. You have considered these aspects much more carefully than us. We Be sure to follow your requirements and always pay attention to these aspects."
He is not ready to give up the mechanical dither offset technology and switch to four-band differential now. The main reason is that the benefits of this thing are really visible to the naked eye. There are too many. The downside is, to be honest, if you don’t get to that point, you really can’t feel it, or it feels like it can always be solved.
(End of this chapter)