Application Case

Application of ER-FOG25 In Tank Stabilization System

1. Fiber optic gyroscope

The fiber optic gyroscope is a fiber optic interferometer based on the Sagnac effect, that is, two beams of light that are transmitted in opposite directionsin the same fiber sensing ring to form a fiber Sagnac interferometer, as shown in FIG. 2 .

Figure 2 Schematic diagram of fiber optic gyro

The light beam from the light source is split into two beams by the splitter/combiner, which are respectively coupled into the fiber sensitive coil from both ends of the fiber loop, and propagate in the forward and counterclockwise directions. The two beams coming out from the two ends of the fiber ring are superimposed by the splitter/combiner to generate interference, and the phase difference 1 generated is proportional to the angular velocity 2 of the ring:


among them,

Lfiber length;

The average diameter of the D fiber optic ring;

The wavelength of light in a vacuum;

The speed of light in a vacuum.

The information of the angular rate 2 can be obtained by detecting the phase difference 1 (i.e., the intensity of the interference light), where the 4 term is the scale factor of the gyro.

Figure 3 fiber ring physical map

Fiber optic gyroscopes are photoelectric sensors that differ from conventional electromechanical gyroscopes. It has the advantages of no moving parts, wide dynamic range, direct digital output and networking with computer interface, and is ideal for mobile carriers and military applications. The feature is that the fiber optic gyroscope is directly connected to the carrier and can directly bear the various working environments of the carrier.

2. The main role of fiber optic gyroscope in attitude measurement system

1. Through the motion information of the fiber optic gyroscope’s sensitive motion device around its center of mass, it is ensured that the motion device can achieve stable flight under the action of internal and external interference, and its attitude change is controlled within the allowable range. The motion of the motion device around the centroid can be decomposed into angular motions around its three axes. Therefore, the corresponding three basic measurement channels measure and stabilize the pitch, yaw and roll axes of the motion device. The three measurement channels are basically the same, and each consists of a single-axis fiber gyroscope and its information processing system (or three-axis fiber gyroscope and information processing system) to achieve continuous measurement of the output attitude information of the motion device.

2. Then there is the fiber optic gyroscope as a rate gyro, whose output information can be directly used as the attitude control signal of the artillery or tank; at the same time, as an important part of the carrier attitude control, it passes the sensitive angular velocity signal to the carrier attitude stabilization system. Advance control provides conditions. It mainly plays the following roles:

1) Through the three angular angular velocities of the pitch, yaw and roll of the sensitive carrier, and output an analog voltage proportional to the angular velocity through the signal conversion, and send the signal to the carrier computer to adjust the carrier attitude through servo control to achieve Stable flight or operation of the carrier.

2) Provide sufficient damping ratio for the attitude control loop, the damping coefficient is generally not more than 0.10~0.15, and the overshoot of the attitude angle is generally not more than 30%.

3、The main requirements of fiber optic gyroscopes used in attitude control loops:

1) Determine the kinematics of the carrier, including the height, velocity and overload of the carrier, to determine the open-loop transfer coefficient of the system loop and the stability margin of the system.

2) The system has a certain bandwidth bandwidth requirement, which is mainly determined by the operating conditions of the system.

3) The system should be able to effectively suppress external interference on the carrier and stabilize internal interference of the system equipment.

4) The system also needs to limit the maximum overload of the carrier to a given value, which is determined by the structural strength of the carrier and the structural components of the system equipment.

5) For carriers with a large angle of attack, limit their maximum use angle of attack to ensure system stability and other performance requirements.

6) The fiber optic gyroscope is used as a rate gyro to the angular velocity command system. The attitude control loop system gain provides a unity acceleration transmission gain. Normally, the loop gain is less than 1, the system is particularly sensitive to speed changes. In addition, any noise of the system command is amplified by high gain, and, in order to avoid noise saturation, actuator electronics have a large dynamic range.

4. Introduction to ER-FOG25

4.1. Overview

ER-FOG25 fiber optic gyroscope contains five optical devices, a set of structures, a signal detection front plate, and a light source control circuit board. The structure is integrated with optical system and circuit system. It is simple to install, easy to use, stable and reliable. Users only need to use a plug to provide power supply, external motherboard, and receive gyro output data.The product can be used for attitude measurement, navigation, guidance and other fields.

4.2. Main Performance Indicators (typical values)

A)  Measuring range: not less than 500 ° / s, can be adjusted according to user requirements;

B)  Zero bias stability of (1σ) : 1 ° / h;

C)  Resolution: 0.5 ° / h;

D)  Scale factor non-linearity (1σ) : 300ppm;

E)  Random walk coefficient: 0.1 (°/√h);

F)  Bandth: not less than 400Hz;

G) Power consumption: less than 3W;

H) Working temperature:M1A: -40°C to +60°C;

M2: -55°C~+85°C;

4.3. Dimensions

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