The principle of the laser gyroscope is to use the optical path difference to measure the rotation angular velocity (Sagnac effect). In a closed optical path, two beams of light transmitted in clockwise and counterclockwise directions emitted by the same light source interfere with the light. By detecting the phase difference or changes in interference fringes, the rotation angular velocity of the closed optical path can be measured. The basic component of the laser gyroscope is a ring laser. The ring laser consists of a closed optical path made of triangular or square quartz. There are one or several tubes filled with mixed gas (helium and neon gas), two opaque reflectors and A translucent mirror. Use a high-frequency power supply or a DC power supply to excite the mixed gas to produce a monochromatic laser. To maintain loop resonance, the perimeter of the loop should be an integer multiple of the wavelength of the light wave. A semi-transparent mirror is used to guide the laser out of the loop, and the two oppositely transmitted laser beams are interfered through the reflecting mirror, and a digital signal proportional to the output angle is input through the photodetector and circuit.
It is easier to understand through the schematic diagram on the right.
The structure of the laser gyroscope
The optical loop of the laser gyroscope is actually an optical oscillator. According to the shape of the optical cavity, there are triangular gyroscopes and square gyroscopes. The cavity structure is There are two types: component type and integral type. Generally, the triangular laser gyroscope is used the most. The structure of a typical laser gyroscope is as follows: its base is a triangular ceramic glass with a low expansion coefficient, and an equilateral triangular optical cavity is processed on it. The gyroscope is composed of such a closed triangular optical cavity, with the sides of the triangle The output mirror is installed at each corner, the control mirror and the offset mirror are defined, and a plasma tube filled with a low-pressure helium-neon mixed gas is installed on one side of the triangle.
Characteristics of the laser gyroscope
The laser gyroscope has no rotating rotor components, no angular momentum, and does not require a direction ring frame, frame servo mechanism, rotating bearing, conductive ring and torque It has simple structure, long working life, easy maintenance and high reliability. The average trouble-free working time of the laser gyroscope has reached more than 90,000 hours.
The dynamic range of the laser gyroscope is very wide, the measured rate is ±1500 degrees per second, the minimum sensitive angular velocity is less than ±0.001 degrees per hour, the resolution is of the order of /radical second, and the inherent digital increment The angle and angular velocity information of the quantitative output carrier does not require a precise analog-to-digital converter and can be easily converted into digital form, which is convenient for interfacing with the computer and is suitable for use in strapdown systems.
The operating temperature range of the laser gyroscope is very wide (from -55℃~﹢95℃), no heating is required, the startup process time is short, the system response time is fast, and it can be put into use in a few seconds after the power is turned on. Works normally. It only takes 50 milliseconds to achieve an accuracy of 0.5 degrees per hour, which is very valuable for the guidance of weapon systems.
The laser gyroscope has no moving parts and no mass imbalance problem, so it is not sensitive to the vibration and impact acceleration of the carrier, and its sensitivity to gravity acceleration is negligible, so there is no need for an imbalance compensation system , the output signal has no cross-coupling terms, high accuracy, the offset value is less than 0.001 degrees per hour, the random drift is less than 0.001 degrees per hour, the long-term accuracy and stability are good, there is no change in the output within 9 years, and the repeatability is excellent.
Laser gyroscopes have no precision parts. The parts that make up the gyroscope are small in variety and quantity, require less mechanical processing, are easy to mass produce and automate, and cost about one-third of conventional gyroscopes.
The main technical principles that laser gyroscopes need to break through are drift, noise and latch-up threshold. The latch-up threshold will affect the linearity and stability of the laser gyroscope's scale factor. The latching threshold depends on the loss in the resonant optical path, mainly the loss of the mirror. The laser gyro is a new navigation instrument developed based on the principle of optical interference. It has become an ideal main component of the new generation of strapdown inertial navigation system and is used for all The imagined object is precisely positioned. The quartz flexible pendulum accelerometer is a sensitive element made of fused quartz. The flexible pendulum structure is equipped with a feedback amplifier and a temperature sensor for measuring linear acceleration along one axis of the carrier.
The laser gyro three-axis inertial measurement combination consists of three fiber optic gyroscopes and three quartz flexible pendulum accelerometers. It can output the angular velocity, linear acceleration, linear velocity and other data of the carrier in real time, and has the ability to It can be used for combined navigation and positioning of mobile carriers, and provides accurate data for the mechanical control device of the following antenna. Main performance: metering accuracy 1×10-4g; fiber optic gyroscope accuracy (drift stability) ≤1°/h; scale solid linearity ≤5×10-4.
Lasers first appeared in the world in 1960. In 1962, the United States, Britain, France, and the former Soviet Union began to develop the use of lasers as azimuth and direction finders at almost the same time, called laser gyroscopes.
Related technologies: control technology; measurement technology; semiconductor technology; microelectronics technology; computer technology.