Time 2023-09-07

Using inertial components (accelerometers) to measure the acceleration of the carrier itself, the velocity and position are obtained through integration and operation, thereby achieving the purpose of navigation and positioning of the carrier. The equipment that makes up the inertial navigation system is installed in the carrier body, and it does not rely on external information or radiate energy to the outside world during operation, making it less susceptible to interference. It is an autonomous navigation system. Inertial navigation systems typically consist of inertial measurement devices, computers, control displays, etc. Inertial measurement devices include accelerometers and gyroscopes, also known as inertial measurement units. Three degrees of freedom gyroscopes are used to measure the three rotational movements of the carrier; Three accelerometers are used to measure the acceleration of three translational movements of the carrier. The computer calculates the speed and position data of the carrier based on the measured acceleration signal. Control the display to display various navigation parameters. According to the installation method of the inertial measurement unit on the carrier, it is divided into platform type inertial navigation system (where the inertial measurement unit is installed on the platform of the inertial platform) and strapdown inertial navigation system (where the inertial measurement unit is directly installed on the carrier); The latter eliminates the need for platforms, resulting in poor instrument working conditions (affecting accuracy) and a large computational workload.

inertial navigation

The technology of obtaining instantaneous velocity and position data of aircraft by measuring the acceleration (inertia) of the aircraft and automatically performing integration operations.

In the 17th century, I. Newton studied the mechanical problems of high-speed rotating rigid bodies. Newton's laws of mechanics are the theoretical foundation of inertial navigation. In 1852, J. Foucault referred to this rigid body as a gyroscope, which later became a gyroscope for attitude measurement. In 1906, H. Anchez manufactured a gyroscope with a rotating axis that could point in a fixed direction. In 1907, he added swing to the steering wheel and made a gyrocompass. These achievements have become the pioneers of inertial navigation systems. In 1923, M. Shula published the "Shula Pendulum" theory, which solved the problem of establishing a perpendicular line on a moving carrier, so that the error of the accelerometer would not cause the divergence of inertial navigation system errors, providing a theoretical basis for achieving inertial navigation in engineering. In 1954, the inertial navigation system was successfully tested on an aircraft. In 1958, the submarine "Nautilus" relied on inertial navigation to navigate through the Arctic and navigate under the ice for 21 days. China began developing inertial navigation systems in 1956, and since 1970, it has adopted domestically developed inertial navigation systems on multiple launches of artificial Earth satellites, rockets, and various aircraft.

Inertial navigation system belongs to a type of predictive navigation method, which calculates the position of the next point from a known point based on continuously measured carrier heading angle and velocity. Therefore, the current position of the moving object can be continuously measured. The gyroscope in the inertial navigation system is used to form a navigation coordinate system to stabilize the measurement axis of the accelerometer in this coordinate system and provide heading and attitude angles; Accelerometers are used to measure the acceleration of a moving body and obtain velocity by integrating it with time. The velocity is then integrated with time to obtain distance. The inertial navigation system has the following main advantages: (1) As it is an autonomous system that does not rely on any external information and does not radiate energy to the outside, it has good concealment and is not affected by external electromagnetic interference; (2) It can work in the air, Earth's surface, and even underwater all day, all weather, all time. (3) It can provide position, speed, heading, and attitude angle data, resulting in good continuity and low noise of navigation information. (4) The data update rate is high, and short-term accuracy and stability are good. Its disadvantages are: (1) Due to the integration of navigation information, positioning error increases over time, and long-term accuracy is poor; (2) Long initial alignment time is required before each use; (3) The price of equipment is relatively expensive; (4) Unable to provide time information.