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Development of inertial navigation systems
Dec 11, 2018


The inertial system is an autonomous dead reckoning navigation system that uses inertial sensors, reference directions, and initial position information to determine the orientation, position, and velocity of the vehicle. It consists of at least one inertial measurement unit, a digital computer and a control display unit, and a dedicated precision power supply. The movement of the carrier is carried out in three dimensions, and its form of motion, one is linear motion and the other is angular motion. Whether the line motion or the angular motion is three-dimensional, to establish a three-dimensional space coordinate system, it is necessary to establish a three-axis inertial platform. A three-axis inertial platform is available to provide a baseline for measuring the three-degree-of-freedom line acceleration. The three linear acceleration components of the known azimuth are measured, and the moving speed and position of the carrier are calculated by a computer. Therefore, the first large class of inertial navigation system scheme is a platform inertial navigation system. Without the “electromechanical” platform, the inertial component gyroscope and accelerometer are directly mounted on the carrier, and a “mathematical” platform is established in the computer to obtain the speed and position of the carrier through complex calculation and transformation. Inertial navigation system is the second largest class of inertial navigation system, called the strapdown inertial navigation system .

In a broad sense, the process of directing a navigation carrier from a starting point to a destination is collectively referred to as navigation. Navigation in a narrow sense refers to techniques and methods for providing real-time attitude, speed and position information to a navigation vehicle. In the early days, people relied on astronomical and geophysical methods such as geomagnetic field, starlight, and solar height to obtain localization and orientation information. With the development of science and technology, technologies such as radio navigation, inertial navigation, and satellite navigation have been introduced, and they have been widely used in military and civilian fields. Among them, inertial navigation is a technical method of measuring the attitude, speed, position, and the like of a carrier using a gyroscope and an accelerometer mounted on a carrier. The software and hardware devices that realize inertial navigation are called inertial navigation systems, referred to as inertial navigation systems.

The Strap-down Inertial Navigation System (SINS) is to mount the accelerometer and the gyroscope directly on the carrier, and calculate the attitude matrix in real time in the computer, that is, calculate the carrier coordinate system and the navigation coordinate system. The relationship, thereby converting the accelerometer information of the carrier coordinate system into information in the navigation coordinate system, and then performing navigation calculation. Due to its high reliability, strong function, light weight, low cost, high precision and flexible use, SINS has become the mainstream of today's inertial navigation system development. The Inertial Measurement Unit (IMU) is the core component of the inertial navigation system. The accuracy of the output information of the IMU largely determines the accuracy of the system.

Gyroscopes and accelerometers are indispensable core measurement devices in inertial navigation systems. Modern high-precision inertial navigation systems place high demands on the gyroscopes and accelerometers used, because the drift error of the gyroscope and the zero offset of the accelerometer are the most direct and important factors affecting the accuracy of the inertial navigation system. The factors, therefore how to improve the performance of inertial devices, improve the measurement accuracy of inertial components, especially the measurement accuracy of gyroscopes, has always been the focus of research in the field of inertial navigation. The development of gyroscopes has gone through several stages. The original ball-bearing gyro has a drift rate of (l-2) ° / h, and the air float, liquid float and maglev gyroscope developed by the inertial instrument support technology can achieve an accuracy of 0.001 ° / h, and The accuracy of the electrostatically supported gyro can be better than 0.0001 ° / h. Since the 1960s, the development of flexible gyros has begun, with drift accuracy better than 0.05°/h, and the best level can reach 0.001°/h.

In 1960, the laser gyro was successfully developed for the first time, marking the beginning of the optical gyro to dominate the gyro market. At present, the laser gyro has a zero-bias stability of up to 0.0005°/h. The biggest problem faced by the laser gyro is that its manufacturing process is relatively complicated, resulting in high cost, and its volume and weight are also large. It has limited its development and application in certain fields, and on the other hand, it has promoted the development of laser gyros in the direction of low cost, miniaturization and triaxial integration. Another optical gyro-fiber gyro not only has many advantages of laser gyro, but also has the characteristics of simple manufacturing process, low cost and light weight, and is now becoming the fastest growing optical gyro.

Development of inertial navigation systems

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