Modern fiber optic gyroscopes include interferometric gyroscopes and resonant gyroscopes, both of which are developed according to Segnik's theory. The main point of Segnik's theory is this: when a light beam propagates in an annular channel, if the annular channel itself has a rotating speed, then the propagation time of the light beam in the rotating direction of the channel is longer than that in the opposite direction. That is to say, when the optical loop rotates, the optical path of the optical loop will change in different directions relative to the optical path of the loop at rest. Using this change of optical path, if the rotation speed of the loop is measured by the interference between lights advancing in different directions, an interferometric fiber optic gyroscope can be manufactured. If we use this change of optical path, that is, by adjusting the resonant frequency of the light in the optical fiber loop and then measuring the rotating speed of the loop to realize the interference between the circulating lights in the loop, we can manufacture the resonant fiber optic gyroscope. From this simple introduction, we can see that the optical path difference of interferometric gyroscope is small, so the light source it requires can have a larger spectral width, while the optical path difference of resonant gyroscope is large, so the light source it requires must have good monochromaticity. Since 1970s, the development of modern gyroscopes has entered a new stage. 1976 and others put forward the basic idea of modern fiber optic gyroscope. Since 1980s, modern fiber optic gyroscopes have developed very rapidly, and at the same time, laser resonant gyroscopes have also developed greatly. Because of its compact structure, high sensitivity and simple operation, fiber optic gyroscope has completely replaced mechanical traditional gyroscope in many fields and become a key component in modern navigation instruments. With the development of fiber optic gyroscopes, there are not only ring laser gyroscopes, but also modern integrated vibrating gyroscopes with higher integration and smaller volume, which is also an important development direction of modern gyroscopes.

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Modern fiber optic gyroscopes include interferometric gyroscopes and resonant gyroscopes, both of which are developed according to Segnik's theory. The main point of Segnik's theory is this: when a light beam propagates in an annular channel, if the annular channel itself has a rotating speed, then the propagation time of the light beam in the rotating direction of the channel is longer than that in the opposite direction. That is to say, when the optical loop rotates, the optical path of the optical loop will change in different directions relative to the optical path of the loop at rest. Using this change of optical path, if the rotation speed of the loop is measured by the interference between lights advancing in different directions, an interferometric fiber optic gyroscope can be manufactured. If we use this change of optical path, that is, by adjusting the resonant frequency of the light in the optical fiber loop and then measuring the rotating speed of the loop to realize the interference between the circulating lights in the loop, we can manufacture the resonant fiber optic gyroscope. From this simple introduction, we can see that the optical path difference of interferometric gyroscope is small, so the light source it requires can have a larger spectral width, while the optical path difference of resonant gyroscope is large, so the light source it requires must have good monochromaticity.

Principles for editing this paragraph

Gyroscope is basically a directional instrument made by using the property that when an object rotates at high speed, its angular momentum is very large and its rotation axis will always point in one direction stably. But it must rotate fast enough, or its inertia is large enough (that is, its angular momentum is large enough). Otherwise, as long as the torque is very small, it will seriously affect its stability. Just like in the activity on page four, we can easily change the direction of the rotating axle. Therefore, gyroscopes installed on airplanes and missiles are the internal power to keep them rotating at high speed.

The purpose of editing this paragraph

Gyroscopes are usually installed on vehicles or vehicles, such as airplanes, spaceships, missiles, satellites and submarines. , you can determine the direction of east, west, north and south. It is the main basis for judging orientation in aviation, navigation and space navigation systems. This is because under high-speed rotation, the rotating shaft of the gyroscope stably points to a fixed direction. After comparing this direction with the axis of the aircraft, the correct direction of the aircraft can be accurately obtained. Compass can't replace gyroscope, because compass can only determine the direction of plane; On the other hand, gyroscopes are more convenient than traditional compasses, because traditional compasses are oriented by the earth's magnetic field, so they will be disturbed by mineral distribution, such as iron-containing substances in aircraft fuselage or hull; On the other hand, the geographical north pole and the geomagnetic north pole will have great deviation at the poles, so at present, gyroscopes and satellite navigation systems have been used as the main instruments for orientation in aviation and navigation.

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principle

The principle of laser gyro is to measure the rotational angular velocity (Sagnac effect) by using the optical path difference. In the closed optical path, two beams of light in clockwise and counterclockwise directions from the same light source interfere with each other. By detecting the change of phase difference or interference fringe, the rotational angular velocity of the closed optical path can be measured. The basic component of laser gyro is ring laser. The ring laser consists of a triangular or square closed optical path, with one or several tubes filled with mixed gas (He-Ne gas), two opaque mirrors and a translucent mirror. The mixed gas is excited by high frequency power supply or DC power supply to generate monochromatic laser. In order to maintain the resonance of the ring, the circumference of the ring should be an integer multiple of the wavelength of the light wave. The laser is guided out of the loop by a semi-transparent and semi-reflective mirror, and two beams of laser transmitted in opposite directions interfere with each other through the mirror, and a digital signal with an angle equivalent to the output angle is input through the photodetector and the circuit. Cross the right

The schematic diagram is easier to understand. The main technical principles that laser gyro needs to break through are drift, noise and locking threshold.

Drift of laser gyro

The drift of laser gyro shows zero bias instability, and the main error sources are: the refractive index anisotropy of resonant optical path, the flow of He-Ne plasma in laser tube, the anisotropy of medium diffusion and so on.

Noise of laser gyro

The noise of laser gyro is manifested in angular velocity measurement. Noise mainly comes from two aspects: one is the spontaneous radiation of laser medium, which is the quantum limit of laser gyro noise. Secondly, mechanical dithering is the frequency biasing technology adopted by most laser gyroscopes at present. When the dithering motion changes direction, the dithering angular rate is low, which is lower than the locking threshold in a short time, which will cause the leakage of input signal and the random change of the phase angle of output signal.

Locking threshold of laser gyro

Locking threshold will affect the linearity and stability of laser gyro scale factor. The locking threshold depends on the loss in the resonant optical path, mainly the loss of the mirror. Laser gyro is a new navigation instrument developed on the basis of optical interference principle, and has become an ideal main component of a new generation of strapdown inertial navigation system, which is used to accurately locate imaginary objects. Time-sensitive flexible pendulum accelerometer is a sensitive element made of melting time. The flexible pendulum structure is equipped with a feedback amplifier and a temperature sensor to measure the linear acceleration along the axis of the carrier. The three-axis inertial measurement unit of fiber optic gyro is composed of three fiber optic gyroscopes and three flexible pendulum accelerometers, which can output the angular velocity, linear acceleration and linear velocity data of the carrier in real time, and has various working modes such as alignment, navigation, heading and attitude reference, etc., which is used for integrated navigation and positioning of the moving carrier and provides accurate data for the mechanical control device of the follow-up antenna. Main performance: the accuracy of adding tables is1×10-4g; The accuracy (drift stability) of fiber optic gyro is ≤1h; Fixed linearity of scale ≤5× 10-4. 1960 Laser first appeared in the world. From 65438 to 0962, the United States, Britain, France and the former Soviet Union began to develop a laser as a direction finder almost at the same time, which was called a laser gyro. The principle of laser gyro is to measure the rotational angular velocity (Sagnac effect) by using the optical path difference. In the closed optical path, two beams of light in clockwise and counterclockwise directions from the same light source interfere with each other. By detecting the change of phase difference or interference fringe, the rotational angular velocity of the closed optical path can be measured. The basic component of a laser gyro is a ring laser, which consists of a triangular or square closed optical path, one or several tubes filled with mixed gas (He-Ne gas), two opaque mirrors and a translucent mirror. The mixed gas is excited by high frequency power supply or DC power supply to generate monochromatic laser. In order to maintain the resonance of the ring, the circumference of the ring should be an integer multiple of the wavelength of the light wave. The laser is guided out of the loop by a semi-transparent and semi-reflective mirror. Two laser beams transmitted in opposite directions interfere with each other by the reflective mirror, and a digital signal proportional to the output angle is input through a photodetector and a circuit. [Related Technology] Control technology; Measurement technology; Semiconductor technology; Microelectronics technology; computer technology

Technical difficulties in editing this paragraph.

The main technologies that laser gyro needs to break through are drift, noise and locking threshold.

Drift of laser gyro

The drift of laser gyro shows zero bias instability, and the main error sources are: the refractive index anisotropy of resonant optical path, the flow of He-Ne plasma in laser tube, the anisotropy of medium diffusion and so on.

Noise of laser gyro

The noise of laser gyro is manifested in angular velocity measurement. Noise mainly comes from two aspects: one is the spontaneous radiation of laser medium, which is the quantum limit of laser gyro noise. Secondly, mechanical dithering is the frequency biasing technology adopted by most laser gyroscopes at present. When the dithering motion changes direction, the dithering angular rate is low, which is lower than the locking threshold in a short time, which will cause the leakage of input signal and the random change of the phase angle of output signal.

Locking threshold of laser gyro

Locking threshold will affect the linearity and stability of laser gyro scale factor. The locking threshold depends on the loss in the resonant optical path, mainly the loss of the mirror.

Edit this foreign overview.

1963, the experimental device of laser gyro was made by sperry company for the first time. From 65438 to 0966, Honeywell began to use Synchrotron as a resonant cavity, and developed a frequency offset method of alternating mechanical jitter, which made it possible to use this technology. 1972, Honeywell company developed GG- 1300 laser gyroscope. 1974, the U.S. department of defense ordered the navy and air force to jointly make a research plan, which was successfully tested on 1975 tactical aircraft and 1976 tactical missile. Since the 1980s, the US Air Force has indicated that it will firmly apply the laser gyro to the air force system, and signed two contracts with McDonald Douglas to implement a research plan called "Integrated Inertial Reference Module", the content of which is to develop a dual-box module sensor system using the laser gyro. The navy also plans to use laser gyro inertial navigation system on carrier aircraft in the 1980s, which is called CA 1NS 1. The army is going to use laser gyro in the positioning/navigation, surveillance/reconnaissance, fire control and flight control system of army aircraft. After the strategic defense plan (SDI) was put forward by the United States in 1985, the application of laser technology in military systems and space weapons has attracted much attention. According to the SDI budget, the investment in this field in fiscal year 1985 was 104 billion USD, most of which was used to carry out laser experiments, including the development of laser gyro. In 1990s, according to the requirements of advanced cruise missiles and tactical aircraft navigation, the strapdown performance of laser gyro (SPS) was studied in the United States. MacDonald Douglas was selected as the main contractor of SPS, followed by Honeywell, Litton, Rockwell, Singer Kilford and other companies. There are many research units of laser gyro abroad, among which the United States and France have a high level of development, in addition to Russia, Germany and other countries. 1. The manufacturers of laser gyroscopes in the United States are Honeywell, Litton and sperry. (1) Honeywell's ideal tactical inertial device must have the characteristics of low cost, small volume, light weight and firmness. Honeywell's GG 1308 and GG 1320 are the latest products developed for this purpose. The key technologies adopted by the company are: 1) output signal subdivision technology is improving accuracy and maintaining the required resolution in miniaturized RLG. Increase the frequency of jitter bias to increase the sampling frequency of RLG. Miniaturized RLG has small inertia and high resonance frequency, which can improve the frequency in the design of dithering polarizer. Therefore, the sampling frequency of RLG and the calculation frequency of SINS can be improved, which is beneficial to ensure the accuracy of SINS. 2) In terms of cost reduction, glass sintering process is adopted to seal the mirror and electrode. BK-7 optical glass is used to replace materials with zero expansion coefficient, such as Zerodur. Therefore, it is necessary to establish the condition of light wave resonance in the resonator and compensate the temperature error. An inertial navigation system composed of GG 1308 is HGl500-IMU. The inertial navigation system composed of GG 1320 is H-764C. (2) Based on the single-axis RLG, Kilford Company developed a miniature three-axis laser gyroscope MRLG to meet the needs of small satellites and spacecraft. The company uses force feedback accelerometer and MRLG to form inertial measurement unit IMU. This inertial navigation system can also be used in tactical weapons, including torpedoes. 2. France has strong laser gyro and system technology. France's SWXTANT Company and SAGEM Company both started to study the laser gyro technology in 1970s, and now they have formed laser gyroscopes with different sizes and accuracies. (1) sextant company sextant company began to study laser gyroscopes in 1972. The sextant laser gyro was first used in Jaguar helicopter flight in 1979. 198 1 33cm laser gyro won the bid in ANS supersonic missile project, 1987 was first used in Ariane 4 rocket flight, and 1990 sextant company won the bid in France's future strategic missile project. (2) Sachim Company Sachim Company began to study ring laser gyro from 1977. 1987 assembled the first prototype GLS32. After the technology is mature, it mainly produces strapdown inertial navigation systems for aviation and submarines. The GLC 16 prototype is assembled in 1987, which is mainly used for strapdown inertial navigation systems of helicopters and small launch vehicles.

The influence of editing this paragraph

As the core of aircraft inertial navigation system, inertial devices play a very important role in many fields of national defense technology and national economy. It takes a long time and a lot of investment for laser gyro to solve the locking problem. It was not until the early 1980s that aircraft navigation instruments were developed, and then they were quickly applied to aircraft and helicopters, replacing dynamically tuned gyroscopes and integrating mechanical gyroscopes. At present, it has been widely used in navigation, radar, guidance and other fields.