Chapter 487 The core device of the photoelectric encoder
Gao Zhendong’s words were originally to explain why the incremental encoder was made first, but to the ears of the Guangyang factory, although he did not understand what an incremental encoder was, But the first reaction was a little embarrassed.
Our skills are still not good enough. In order for us to keep up, Chief Engineer Gao had to teach us simple things.
"Mr. Gao, can you explain the increments and multi-turns you mentioned?"
You can also guess the multi-turns. It probably means that it can rotate many turns.
But if the increment is not explained, they will not understand it. If this kind of technical terminology is not asked clearly, random guessing will sometimes go in the wrong or even the opposite direction.
For example, "holotype fossil replica", the "positive" of this holotype has nothing to do with the direction, but when connected with the "model" and "copy" at the back, quite a few people rely on Intuition will make you guess wrong.
But what this thing really means is "a copy of a holotype fossil", not a "copy of a holotype fossil", and holotype fossil is a special term, for ordinary people , can be loosely understood as the standard fossil of a species, and it has nothing to do with direction, forward and reverse molds, etc.
Gao Zhendong briefly explained what an incremental encoder is and what an absolute encoder is.
“I understand, increment means that it can only measure the change in rotation, but it cannot directly output the specific angle of rotation.” said a technician from Gwangyang Factory.
Gao Zhendong shook his head: "That's not entirely true. The external manifestation of the core difference between them is what you said, but the real core is not like that. It needs to be deeper."
Meet everyone Somewhat puzzled, he continued: "The real core is that the output of the incremental encoder is only the output increment, and the output data does not correspond to the position of the encoder shaft. That is, it is impossible to directly judge the current position and the initial position. The relationship between the positions. "
Comrades in Guangyang Factory are aware of the problem: "How to solve it in practical applications? "
"Technically, a counting circuit can be added externally. to judge, but if part of the incremental output signal is lost due to interference, power-off signal line failure, active shutdown, etc., then the accumulated rotation angle value at this time will be wrong and needs to be weakened through other technical means or management means. Or recalibration, for example, it needs to be reset to zero after active shutdown, but this still cannot completely eliminate its disadvantages.”
Gao Zhendong explained in more detail, after all, the comrades in Guangyang Factory were all in contact with it for the first time. This thing.
"Ah, I understand. The output data of an absolute encoder corresponds to the position of the rotating shaft one-to-one. By directly reading the output data, you will know how many degrees it has rotated."
"Yes, regardless of a single turn Or multi-turn, the output of the absolute encoder corresponds to the angle of rotation of the shaft. At the same time, the output of the absolute encoder is basically a digital output, which is very convenient for future computer-centered control systems. "
The reason why it is called "basic" is because there are absolute encoders that also have analog outputs due to compatibility reasons, such as 4~20mA, 0~5V analog outputs.
However, this analog interface is generally not used under normal circumstances, which increases system complexity and introduces errors.
After listening to this, Mr. Yang had an idea: "General Engineer Gao, since relative encoders have so many defects, why don't we just make absolute encoders?"
Gao Zhendong smiled. This is a mistake that many people tend to make when they first come into contact with encoders. They think that incremental encoders and absolute encoders are binary opposites.
Increments have incremental uses, and absolutes have absolute environments.
He shook his head: "Mr. Yang, there is actually no distinction between incremental encoders and absolute encoders. The main reason is that the application scenarios are different, and it is difficult to completely replace each other. But between the two, theoretically They can be converted to each other through certain technical means. I suggest you start with incremental encoders because most of the current control systems are mainly based on analog methods and there are not so many digital control environments to support absolute encoders. , in this regard, the incremental encoder is better."
After that, he explained the reason to Mr. Yang in depth.
Although the incremental encoder also outputs digital pulses, introducing digital pulses into the analog control system is much simpler than converting a series of numbers and then introducing them into the analog control system.
Moreover, the advantage of the absolute encoder is that it is an absolute quantity, and its core advantage is to participate in calculations and comparisons. However, this core advantage cannot be fully utilized in analog control systems.
Mr. Yang listened and nodded repeatedly: "Mr. Gao is still thoughtful. When we develop new things, we must not only look at the technology itself, but also whether the application environment can match it. I have learned a lesson."
Gao Zhendong nodded and said another reason for not developing absolute encoders for the time being: "Moreover, the technology of absolute encoders is more troublesome. You first develop incremental encoders. Once you have experience, we will Consider the absolute encoder. "
I have the technology, but you may not be able to accept it at once. Let's take it step by step.
The comrades in Guangyang Factory are a little bit dumbfounded. The reason for co-writing is that we are too naive and old-hearted!
A comrade from the Guangyang Factory had an idea: "General Engineer Gao, if an absolute encoder must be used due to need, can we use a set of digital circuits to count the output of the incremental encoder, and then output the digital value? ? At the same time, use batteries and other means to ensure that the digital data is maintained when power is turned off? "
Hey, this little comrade is good, he still has a lot of ideas.
“Haha, your idea is good. Although it cannot completely solve the problem, it can meet the requirements to a certain extent. This is why I said that theoretically the two can be converted into each other. Your factory is engaged in simulation Device, but it seems that you also have some research on digital circuits.”
This comrade does not seem to have just graduated, so it is unlikely that he has systematically studied digital circuits in school.
"Hey, I saw a book called "Logic Operation and Design of Digital Circuits" in the bookstore last year. I thought it was very interesting and it was the direction of future development, so I bought it and studied it on my own."
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Gao Zhendong smiled and nodded, well, the young man is still very easy to learn! Having said this, the comrade from the Guangyang Factory suddenly remembered something.
“Ah, I remembered, Chief Engineer Gao, the author of that book is you, right?”
Other comrades looked at Gao Zhendong, I was immediately in awe. I knew that this was a technical expert who was very valued in the ministry, but to what extent his skills were, except for the encoder-related content of the exchange, I could not yet feel it.
But now, I have a deep feeling. It is really incredible that someone can directly publish a book about digital circuit logic operations, which sounds high-tech at first glance.
Only Mr. Yang looked at this comrade with an expression that said, "You can do it, the road is getting wider."
He cleared his throat: "Mr. Gao, Xiao Xu is the young technical backbone of our factory. He has always been diligent and studious, and has many ideas."
Although this "young backbone" is actually better than Gao Zhendong He is still a little older, but it does not affect him at all from introducing him to Gao Zhendong in the name of "Xiao Xu".
Gao Zhendong is still in a good mood. As long as a normal person hears others recognizing his real achievements, he will not feel unhappy.
“Well, Comrade Xu is good. You can work harder in this area. The design and application of photoelectric encoders are also more digital. It will be good for this work to know more about digital circuits. "Yes." Gao Zhendong encouraged.
Mr. Yang nodded: "Well, when we work, we will pay attention to giving full play to the strengths of our comrades and tapping their potential."
Other people in Guangyang Factory looked at Xiao Xu with envy in their eyes. But jealousy is not a problem.
This is what he deserves. In the entire team, he is the only one who can tell this book and come up with the idea of using incremental encoders to replace absolute encoders at low levels. This is the ability and this is the skill.
Practice more and be jealous of others will have no effect on improving your own situation. Everyone's heart is still very righteous.
Seeing that everyone had their own understanding and ideas about incremental encoders, Gao Zhendong took out a pen and paper and drew a picture.
"Comrades, this is the core of the photoelectric encoder, the photoelectric encoding disk."
Everyone came up and wanted to take a closer look. Is the progress so fast? This teaches us all the core things?
The picture shows a disc with a total of three circles of elongated holes from the outside to the inside.
The outermost ring is evenly distributed along the circumference.
Looking inward, it looks like the number of holes is the same as that of the outer ring, but in detail, it is not radially aligned with the outer ring, but is staggered by a small angle.
The innermost circle is special, with only one hole.
It looks very simple and the processing is not complicated.
Looking at this "core device", Yang finally understood why Gao Zhendong asked them to make an incremental photoelectric encoder first. This thing seemed really simple.
For them, the difficulty lies in figuring out the principles and appropriate structure, but when it comes to processing, it is actually not very difficult.
Looking at this disk, everyone was discussing what it meant and how to achieve incremental output.
"This should be when the encoding disk rotates, causing the light to turn on and off, and through the photosensitive element, the pulse signal will be naturally output."
"It seems very simple, but the idea is wonderful."
“I don’t think it’s that simple, otherwise there wouldn’t be three circles.”
Comrade Xiao Xu looked at this and thought for a while, then said: “I know the function of the second circle!”< br>
Everyone looked at him, including Gao Zhendong, wanting to see if his idea was right.
"The pulse output of this second circle has a phase difference from the first circle. By detecting the phase difference between the two, the direction of rotation can be determined."
After listening to his statement, Everyone looked at Gao Zhendong, wondering if he was right.
Gao Zhendong smiled and nodded: "Well, you are right, not bad, not bad, very sharp, and the basic skills are very solid."
(End of this chapter)