The positioning process of the GPS system can be described as: knowing the position of the satellite (implemented by using the ephemeris parameter EPH and almanac parameter ALM to describe the satellite motion), measuring the relative position between the satellite and the user (using the navigation equation), The most reliable position of the user is obtained by solving the navigation algorithm (using the least square method or Kalman filtering method).
The flexible gyro is driven by a flexible rod (very thin and soft), and the rotor rotates at a speed of 12000 r/min. When the base rotates at an angle H, due to the stability of the rotor and the flexible rod very If it is soft, the rotor remains stationary relative to the inertial space, so that the gyro can perceive the angle H of the base rotation.
The gyroscope is also equipped with 2 annunciators and 2 torquers. The 2 annunciators sense the rotation of the base around the X and Y axes and give corresponding signals. The two torquers can apply torque to the gyro to make it precess along the X and Y axes respectively. The inertial platform is a four-ring full-attitude platform stabilized by two two-degree-of-freedom gyroscopes. The platform can isolate the three-axis angular motion of the aircraft, and can accurately track the local horizontal plane and keep the azimuth unchanged (or point to true north) according to the aircraft motion and the rotation of the earth, so that the platform can be stabilized in the geographic coordinate system.
2. Beidou and INS combined system
The Beidou Double Star Positioning System is a regional satellite navigation and positioning system independently developed by my country, which can accurately locate the territory of my country and its surrounding areas. It is composed of three geostationary satellites (one of which is a backup star), a ground central station, and a user. When positioning the system, the user first sends a request to the ground central station, and the ground central station locates it and broadcasts the location information for the user to obtain. The dual-satellite positioning system is active (response type), and needs to establish contact with the central station to locate, so there are two disadvantages of easy exposure of user locations and easy saturation of the number of system users.
Beidou dual-satellite navigation system/inertial navigation system is composed of Beidou receiver, inertial navigation sensor (accelerometer, gyroscope, etc.) and combined filter. The optimal real-time navigation solution is obtained.
It overcomes the shortcomings of easy exposure of user locations and easy saturation of the number of system users. At the same time, the Kalman filter method is used to combine BeiDou/INS to obtain overall higher accuracy and stability. The combined system can reduce the precision requirements for inertial navigation, so the cost of the combined system can be reduced.
