Analysis of the Application Overview of Laser Gyroscope Inertial Navigation Systems at Home and Abroad

1. Development History of Laser Gyroscopes

In 1913, French scientist Sagnac conducted an experiment on the change of interference fringes caused by external rotation in a circular light path and theoretically explained this phenomenon, proposing the Sagnac effect. However, for a long time afterward, due to the lack of suitable coherent light sources, research on the optical Sagnac effect made little progress. It wasn't until 1960 that lasers appeared for the first time in the world, and laser gyroscopes became a hot research topic in various countries as an important application of laser technology. In 1961, American scientist C.V. Heer published the world's first report on laser gyroscopes at the American Physical Society. He introduced the method of measuring the frequency difference between the forward and reverse beams of laser operating in a circular laser resonant cavity to sense changes in external input angular velocity. Subsequently, Sperry Corporation in the United States first developed an experimental device for laser gyroscopes in 1963. In 1966, Honeywell began using quartz as the cavity material and developed the alternating mechanical jitter frequency method, making this technology practically feasible. After more than 40 years of development and improvement, laser gyroscope inertial navigation systems are now widely used in military and civilian applications. In China, the dual-frequency mechanical jitter laser gyroscope technology has also matured and will serve as a key component in future information-based weaponry.

2. Advantages of Laser Gyroscopes

Traditional gyroscopes use the orientation and precession of high-speed rotating mechanical rotors to determine the rotational speed and orientation relative to inertial space. However, the presence of high-speed rotors brings defects such as poor shock and vibration resistance, and acceleration effects, which limit their application in inertial navigation and hinder further development. In contrast, the working principle of laser gyroscopes is completely different from that of conventional electromechanical gyroscopes, and they have the following advantages:

1. Stable performance and strong anti-interference ability. Laser gyroscopes are robust and reliable, resistant to shock and vibration, and have good acceleration performance due to the absence of high-speed rotors.

2. High precision. High-precision laser gyroscopes in the United States achieve 0.0005°/h, while mid-to-high precision products have zero drift between 0.001° and 0.01°/h.

3. Wide dynamic range, capable of measuring high dynamic rotational speed.

4. Long lifespan. Good reliability. Foreign products have a lifespan of over 100,000 hours, with an average time between failures (MTBF) better than 10,000 hours.

5. Stable scale factor. The scale factor stability of foreign laser gyroscopes reaches up to 1 ppm, while domestic laser gyroscopes have also reached a stability of 10 ppm.

6. Quick startup. Since there is no motor startup and stabilization issue like in electromechanical gyroscopes, laser gyroscopes can output information within a short time (3-8 seconds) after startup.

7. Digital output, no need for analog-to-digital conversion. The output signal of laser gyroscopes is in pulse form, and counting the pulses gives the corresponding rotational angle in digital form, making it easy for computer processing without the need for high-precision AD circuits.

8. For the same precision and performance requirements, the cost of laser gyroscopes is lower than that of electromechanical gyroscopes.

9. Low power consumption, small size, and lightweight.

10. Functions as both a rate gyroscope and a position gyroscope. Flexible use and wide application range.

3. Application of Laser Gyroscopes Abroad

Currently, the main countries developing and producing laser gyroscopes and their systems include the United States, the United Kingdom, Germany, France, Japan, and Russia, with the United States and France having the highest development levels. The technology for laser gyroscopes is very mature, forming a series of products such as dual-frequency mechanical jitter, four-frequency differential, spatial three-axis, and Zeeman gyroscopes. The highest level of zero drift has reached 0.00015°/h, with a dynamic input rate range of ±1500°/s and a lifespan of over 200,000 hours, with input axis alignment stability reaching the micro-arc level.

In the United States, manufacturers of laser gyroscopes include Honeywell, Litton, Sperry, and Singer, among others. Sperry first developed an experimental device for laser gyroscopes in 1963. In 1972, Honeywell developed the GO-1300 laser gyroscope. In 1974, the U.S. Department of Defense ordered the Navy and Air Force to jointly formulate a research plan, and in 1975, it successfully tested tactical aircraft, followed by successful tests on tactical missiles in 1976. Since then, laser gyroscopes have been widely used in aviation, aerospace, navigation, and vehicle positioning.

The French company SEXTANT began researching laser gyroscopes in 1972, successfully applying them to the "Tiger" helicopter, ANS supersonic missile, and Ariane 4 rocket, and winning a bid for France's future strategic missile project. SAGEM began researching ring laser gyroscopes in 1977, applying them to inertial navigation systems for aviation and submarines; the GLCl6 prototype they produced is mainly used for inertial navigation systems in helicopters and small launch vehicles. In February 1994, Japan's H2 launch vehicle soared into the sky, marking the first time laser gyroscopes replaced flexible gyroscopes in space launch vehicles. The performance parameters of practical foreign laser gyroscopes are shown in Table 1.1.

Most of the U.S. military's active fighter jets and air-guided weapons are equipped with laser gyroscope inertial navigation systems. To improve the accuracy and reliability of these systems, the U.S. military combines GPS with them to enhance navigation precision, allowing for a high-precision navigation system through a low-cost, medium-precision inertial navigation system combined with GPS. During the Kosovo War, various combat aircraft, Tomahawk II cruise missiles, and GBU-15 guided bombs used by the U.S. military all adopted laser gyroscope inertial navigation/GPS combined navigation systems. When using P(Ⅵ code GPS, the accuracy of the combined navigation system can reach 8m (CEP). After the Kosovo War, the U.S. military increased the production of laser gyroscope inertial navigation/GPS combined navigation systems to meet the demand for guided weapons, and plans to improve the accuracy of the combined navigation system to 3m (CEP) in the next decade.

4. Application of Laser Gyroscopes in China

The domestic laser gyroscope started in the 1960s. Around the early 1970s, Tsinghua University, National University of Defense Technology, Suzhou First Optical Instrument, China Academy of Metrology, and the 303 Institute of the Ministry of Aviation began research on laser gyroscopes. They conducted experiments on jitter frequency, four-frequency differential laser gyroscopes, and explored the basic theory of laser gyroscopes. In the 1980s, the 618 Institute of the Ministry of Aviation, the 12 Institute of the Ministry of Aerospace, National University of Defense Technology, and Tsinghua University began the first round of laser gyroscope research. By the "Eighth Five-Year Plan" period, the National University of Defense Technology and the 618 Institute of the Ministry of Aviation conducted technical appraisals. During and after the "Ninth Five-Year Plan" period, the main units engaged in the development of laser gyroscope components and complete systems were: the 618 Institute of China Aviation Industry and National University of Defense Technology. In the field of technology research for laser gyroscope inertial navigation systems, domestic efforts began in the early 1980s, with a small number of two-frequency jitter laser gyroscopes introduced from the former Soviet Union at the end of the 1980s to conduct research on key technologies. After the successful development of domestic laser gyroscope prototypes, the focus shifted to system research primarily targeting domestic laser gyroscopes.

To date, domestic laser gyroscopes have been successfully applied to the modification of active weaponry and the development of new weapon systems. In the early "Eighth Five-Year Plan" period, the National University of Defense Technology took the lead in introducing the KM2 type two-frequency jitter laser gyroscope produced in Russia, developing the first set of domestic laser gyroscope inertial navigation systems, which were successfully applied to unmanned nuclear reconnaissance armored vehicles. Subsequently, the e3 two-frequency jitter laser gyroscope produced in Russia was introduced to develop a laser gyroscope positioning and orientation navigation system, which was successfully applied to military robot systems. The laser gyroscope inertial positioning and orientation system prototypes developed during the same period have also been successfully applied to the "positioning measurement subsystem, solving the positioning, orientation, and navigation problems of weapon systems in complex meteorological and geographical environments, enhancing the response capabilities of the troops. Currently, research is also being conducted on long-range airborne and shipborne laser gyroscope inertial measurement combination systems by research institutes such as the National University of Defense Technology.

 

中科科美制造陀螺混气台

As a developing country, China has established a war view aimed at winning local wars under high-tech conditions, which determines that the development of our military equipment must adhere to a strategy of doing what is necessary and not doing what is unnecessary. The core of what is necessary is to effectively strike the enemy coming from the air. To achieve this basic goal, it is essential to strengthen the development of tactical missile weapons such as air-to-air, surface-to-air, ground-to-air, and ship-to-air, and to enhance the platforms and information technologies for using these weapons. At the same time, it is necessary to have a certain deterrent counterattack capability and correspondingly strengthen the development of ground-to-ground missiles and anti-ship weapons.

In the equipment and development of the aforementioned tactical missile weapons abroad, almost without exception, inertial measurement units (IMUs) are used as the core components of mid-course guidance. Through combinations of inertial + GPS, inertial + radio commands, inertial + radar, inertial + infrared/laser, inertial + imagery, etc., precise strikes and intelligence of missiles have been achieved, enabling off-axis launches and new air combat modes that do not require guidance after launch, as well as surface air defense and surface anti-missile capabilities. Typical equipment includes Tomahawk, Patriot, AM.1 20, HUMRAAM (high mobility air defense system), R.27, R.77, PBB—AE, S-300, X-59, Granite, SS.N.12, Harpoon, MICA, Arrow 1/2, etc.

Therefore, the inertial measurement unit (IMU) has become the core sensor of tactical weapons and is a key technology and link that must be prioritized and vigorously strengthened in today's high-tech weaponry.

Currently, the inertial technology of China's tactical weapons is mainly based on flexible gyroscopes, which have major issues such as small dynamic range, long preparation time, poor environmental adaptability, low reliability, and short calibration cycles.

Inertial measurement units based on laser gyroscopes can effectively address the above issues.

After more than 20 years of development, domestic laser gyroscopes have gradually formed several core development units, and some units have already established a certain small-scale production capacity. Among them, the laser gyroscope assembly for a key fighter model developed by the 618 Institute has already been delivered in batches. The laser gyroscope for a key model developed by the 33 Institute of Aerospace has undergone target testing, and the inertial navigation system of the 13 Institute of Aerospace has also conducted flight tests. Currently, in addition to aircraft, there is a strong demand for laser gyroscope inertial measurement units in various tactical missile weapons such as short-range ground-to-ground missiles, medium-range air-to-air missiles, long-range air-to-air missiles, ground-to-air missiles, ship-to-air missiles, anti-ship missiles, cruise missiles, and torpedo weapons.

The performance of the laser gyroscopes developed and produced in China has also reached a certain level. For example, the laser gyroscope developed by the 618 Institute has reduced the size and weight of the laser gyroscope by using a microprocessor electronic control module, while also expanding the working temperature range of the laser gyroscope, improving the repeatability of drift to 0.01°～0.005°/h, and reducing the random walk of the laser gyroscope to 0.002°～0.003°/h (comparison indicators are shown in Table 1).

Key Equipment for Laser Gyroscope Production

In the production process of laser gyroscopes, devices such as gyroscope detection devices, gyroscope oil filling devices, gyroscope gas filling and exhaust platforms, and high vacuum brazing annealing furnaces are used. Beijing Zhongke Kemei Technology Co., Ltd. is one of the earliest manufacturers engaged in the production of gyroscope equipment in China, and its equipment is widely used in various gyroscope production enterprises and research institutes across the country. The market share of gyroscope production equipment exceeds 80%. Below are introductions to several key gyroscope production devices.

5.1 Special Detection Device for Gyroscopes

Used for degassing, filling, and sealing leak testing of gyroscopes. Widely used in military and civilian fields such as aviation, aerospace, and shipbuilding. The system has explosion-proof safety measures; it uses an oil filtration device and has environmental protection measures, with a toxic gas filter installed at the pump's exhaust port.

 

 

Technical Parameters

1. System ultimate vacuum: 1×10^-5Pa;

2. System working vacuum: 1×10^-4Pa;

3. System leakage rate: ≤1×10^-10Pa•m³/s;

4. System exhaust rate: ≤1×10^-7Pa•m³/s;

5. Inflatable pressure range: 100Pa-100kPa;

6. System continuous working time: ≥36 h;

7. Vacuum storage tank pressure resistance: ≤20atm;

8. Gas dew point in the vacuum storage tank ≤-65℃.

5.2 Gyroscope vacuum oil dripping platform

Application field

The high vacuum oil dripping platform can provide a clean and oil-free high vacuum environment, suitable for precision instruments, gyroscopes, precision sensors, and transmitters that require filling with high-purity oil, achieving heating, degassing, and oil filling.

 

 

Technical Parameters

1. No-load cold state limit vacuum: better than 5.0×10^-5Pa;

2. Heating temperature: 20℃～600℃;

3. Oil filling speed controllable: 1～10 drops/min (adjustable) or customized as required.

5.3 Laser gyroscope charging and exhausting platform

Application overview

Mainly used for vacuum processing of the cathode in the laser gyroscope resonant cavity. It features oil-free vapor pollution, fast exhaust speed, high limit vacuum degree, and has automatic protection alarm for water and power outages, as well as system overpressure protection.

 

 

Technical Parameters

1. System limit vacuum degree: 5×10^-7Pa;

2. Bell jar limit vacuum degree: 5×10^-4Pa;

3. Baking temperature: 400℃ controllable and adjustable;

4. Inner diameter of the bell jar: customizable;

5. Lifting height: as required;

6. Number of workpieces: 5-10;

5.4 High vacuum brazing annealing furnace system

Product description

This series of equipment is mainly used for gyroscopic instruments, performing processes such as brazing and annealing in a vacuum environment.

 

 

Technical Parameters

1. System limit vacuum degree 5×10^-5Pa;

2. Working vacuum degree 1×10^-4Pa.

3. System leakage rate ≤1×10-10Pam³/S;

4. Maximum heating temperature ≥1000℃;

5. Heating rate 0.5～10℃/min;

6. Temperature uniformity ≤±5℃;

7. Temperature control accuracy ≤±2℃;

8. Uniform temperature zone range ≥∅250mm×400mm.