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【Scientific and Technological Achievements Promotion】 Laser Interference Grating Encoder
In the 21st century of information technology, the name of sensor is more and more familiar to us. The application field of sensor is very wide, such as electronic computer, production automation, modern information, military, transportation, chemistry, environmental protection, energy, marine development, rocker, aerospace, etc. There are many types of sensors, which are a general term for detection devices. Today, Xiao Bian is going to introduce one of the important detection device components-encoder.
Please follow the footsteps of the editor to understand the laser interference grating encoder developed by the Intelligent Displacement Sensor System Research Center of our hospital (hereinafter referred to as "Intelligence Center") after years of research and development.
science and technology research and development]
The word encoder is professional, some readers will sound strange, first let us understand what is the encoder?
The encoder is also called displacement sensor. The encoder can be divided into: resistance, inductance, capacitance, and photoelectric. Among them, their function is to convert physical quantities such as position and motion into digital or analog electrical signals. Due to the advantages of performance, the photoelectric class occupies more than 90% of the market. According to different applications, the photoelectric encoder is divided into two types: the grating ruler for measuring linear motion and the encoder for rotation. It is the "eye" of the motion control system and the core components of machine tools, robots, elevators, missiles, etc.
Traditional photoelectric encoderIt is a sensor that uses the principle of grating diffraction to realize displacement-digital conversion, and converts the mechanical geometric displacement on the output shaft into pulse digital quantity through photoelectric conversion.
A common photoelectric encoder is composed of a grating disk, a light-emitting element and a photosensitive element. The grating is actually a disc engraved with regular light transmission and opaque lines. The luminous flux received by the photosensitive element changes synchronously with the light transmission lines. After the output waveform of the photosensitive element is shaped, it becomes a pulse signal, and outputs a pulse every turn. According to the change of the pulse, the device displacement can be accurately measured and controlled.
Current status of technology at home and abroad
At present, in the world, German Heidehain Company, British Renishaw Company, American Micro-E Company, Japan Telecom Telephone Company (NTT) Electronic Application Research Institute, as well as some manufacturers and scientific research institutions in the United Kingdom and Switzerland have made many contributions to the production and research and development of photoelectric shaft angle encoders.
Among them, the products of German Heidehain company are in the world's leading level in terms of performance and sales volume. The following is the performance of its representative products.
From the analysis of the domestic situation, dozens of scientific research institutions such as Changchun Optoelectronics Institute and Astronomical Instrument Factory have also successively carried out the development and research of photoelectric encoders. A lot of work has been done in the encoder structure and principle, precision shaft system processing, design, analysis, grating manufacturing, detection, electronic processing and encoder error measurement method research, and some achievements have been made in the encoder performance improvement.
After years of research, the resolution of the domestic grating encoder can reach up to 25 bits. But the real can be applied to the industry is still the low-end products.
Traditional encoders currently have technical bottlenecks.
01 Difficult to manufacture
High-precision encoders need tens of thousands of grating lines a week, and the spacing between each grating line is at um level, which requires high processing.
02 Installation difficult
The traditional technology needs to generate bright moire fringes, and the spacing error between the light source, the diffraction mask grating and the moving grating is extremely small.
03 Signal processing difficult
Due to mechanical and electronic interference, the signal has poor ability to distinguish errors and resist interference.
science and technology innovation]
According to the technical characteristics of the current encoder, the intelligent displacement sensor system research center of our hospital has achieved technological breakthroughs in laser light source, grating engraving technology, photoelectric chip research and development, etc. The first phase of research and development products can reach 30-bit resolution and 1-second accuracy, while greatly reducing the requirements for product manufacturing and installation.
Principle of laser interference reflection
The laser light source emits laser light on the moving grating between the convex and concave phases, and the light and dark stripes are formed on the receiver through the interference between the incident light and the reflected light. The principle is shown in the figure below.
Technical advantages
1. High frequency laser light source technology
Compared with the traditional LED light source, the light spot is small, and a smaller grating can be detected.
2. High precision grating engraving technology
Phase I products 262144(2 ^ 18) raster lines per week.
3. New light source detector integration technology
The new laser light source and detector integration technology, compared with the traditional encoder, reduces the spacing between the detector and the grating requirements.
4. Automatic tracking and focusing technology
The light source and detector can automatically follow the spacing from the grating to achieve automatic focusing.
5. Multi-channel data redundancy error correction technology
The encoder can generate multiple photoelectric signals at the same time, and through intelligent algorithm processing, the system redundancy error correction capability is greatly improved, and the system has higher stability. The traditional encoder has only two signals with a phase difference of 90 °.
Product Series
At present, the Center of Intelligence has developed a variety of high-precision, high-resolution angular displacement sensors.
application value]
market prospect
For China's market, European and American products account for 55% of the high-end and high-priced market; Japanese and South Korea products account for 25% of the mid-range price market; Chinese products account for 20% of the low-end price market.
According to statistics from the industry association in 2012, the domestic industrial demand for displacement sensors is 2.8 billion yuan (3.5 million), including 1.3 billion yuan (500000) for linear grating rulers and 1.5 billion yuan (3 million) for circular grating encoders. The annual growth rate after this is 15%. The import rate of products is 80%. According to these data, the estimated scale in 2020 is 8.6 billion yuan and the import volume is 6.9 billion yuan. However, due to the emergence of direct drive motors in recent years and their requirements for high-end encoders, the actual demand is estimated to be more than 10 billion.
Application areas
CNC rotary table helicopter industrial robot
Radar Elevator Missile
Intelligent Displacement Sensor System Research Center
The Intelligent Displacement Sensor System Research Center (hereinafter referred to as "Intelligence Center") is committed to the research and development of high-end core components in the field of intelligent manufacturing, including nano-scale displacement positioning system, nano-scale crush & scratch instrument, nano-scale force measuring system, capacitive angle & displacement sensor, photoelectric angle & displacement sensor, etc. The research goal is to effectively solve the "stuck neck" problem in the field of intelligent manufacturing. The high-end core components developed by the center will be widely used in sub-sectors such as scientific research, national defense, aerospace and industrial production, and will greatly reduce China's dependence on overseas imports of core components.
Technical docking and business negotiation
Contacts: Lin Li and Sheng Lingbo
Telephone: 18610290206/15843025376
Email: linli@tsinghua-tj.org
Source | Intelligent Displacement Sensor System Research Center
Editor | Wang Xiao
The final interpretation of the above related technologies belongs to the Intelligent Displacement Sensor System Research Center.
Address: Buildings 4 and 5, Kechuang Huigu Park, Hongshun Road, Huaming High-tech Zone, Dongli District, Tianjin
Tianjin High-end Equipment Research Institute, Tsinghua University, Copyright
Website Construction: China Enterprise Power Tianjin
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