North seeker measures the angular velocity component of the earth's rotation and can obtain the north direction information of the carrier through calculation and analysis. The north seeker can quickly and accurately determine the local vertical line and true north direction on the carrier using a relatively low-cost inertial sensor without any external information.
Dynamic north finding refers to the continuous constant speed rotation of the fiber optic gyroscope around the vertical central axis of the turntable during the north seeking process, and the initial azimuth angle is calculated based on the output signal of the gyroscope in the horizontal or inclined plane. The advantage of dynamic north seeking is that it changes static measurement into dynamic measurement. Through the continuous rotation of the turntable, the zero deviation and random drift of the gyroscope are periodically predicted. It can be eliminated through integration, which greatly improves the speed and accuracy of north seeking.
Dynamic north seeker system composition and working principle:
As shown in Figure, the fiber optic gyroscope is installed vertically on the turntable, the turntable plane is parallel to the horizontal plane, and the sensitive axis of the gyroscope is parallel to the turntable plane. Assume that the angle between the gyro sensitive axis and the true north direction is θ, the geographical latitude of the location is φ, and a torque motor is used to drive the turntable to rotate at a continuous constant speed with a speed of ω.
Define the directions of coordinates X, Y, and Z to point to the east, north, and sky's directions respectively.If three fiber optic gyroscopes are installed so that they are respectively sensitive to the projection of the earth's rotation angular velocity in these three directions, then the output mathematical model of these three gyroscopes at the initial moment is (k is the scaling factor of the fiber optic gyroscope):
When performing dynamic north search, the gyro rotates around the vertical axis of the turntable at a constant speed. The dynamic output of the gyro during the rotation is
In the second formula, α is the angle the gyroscope rotates relative to its initial position at a certain moment, α = 2πnft, and ε(t) is the drift of the gyroscope, including random drift and zero bias.
Internal structure:
Ericco's high-performance dynamic fiber optic north seeker is composed of high-performance fiber optic gyroscope and quartz accelerometer as core components. The three-axis fiber optic gyroscope is used to detect the angular motion of the carrier and output a digital signal proportional to the angular velocity of the carrier. The linear acceleration of three orthogonally arranged quartz flexure accelerometers is proportional to the current signal and the current signal. The I/F conversion circuit converts the frequency signal into the navigation computer. The navigation computer completes gyroscope, accelerometer, external GPS data reception, system error compensation calculation, navigation solution, and sends real-time navigation information such as speed, position, and attitude through the monitoring port at a predetermined period.
Its main working mode is dynamic, that is, when the carrier is running, it can perform initial direction alignment in a dynamic way. It is currently Ericco's most accurate north finder. However, there are still some shortcomings, such as large size and high energy consumption. For customers with limited monitoring environment, this product may not be suitable for you. You can ask us your specific needs and we will also recommend the most suitable product for you.
Application fields:
Dynamic fiber optic gyro north seekers are commonly used in navigation and control, attitude reference systems, guidance, attitude measurement of vehicles and ships, positioning of rockets and tanks, inertial/satellite integrated navigation systems, drilling systems, mobile surveying and mapping systems, etc.
Among all north-seeking schemes, the dynamic north-seeking scheme has attracted the attention of researchers because of its advantages that static north-seeking cannot match. In response to the demand for both high accuracy and rapidity of dynamic north seeking, we will continue to optimize north seeking accuracy and north seeking time in the future.
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