1. Overview of Missiles
A missile is a typical precision guided weapon. It relies on its own power system for propulsion and uses a professional guidance system to control its flight trajectory, accurately guiding the warhead to strike and destroy targets. Featuring long range, high speed, outstanding accuracy and powerful strike capability, missiles are core equipment of modern precision combat.
According to flight and attack modes, missiles are divided into two categories: winged missiles that strike targets as a complete integrated body, and ballistic missiles that separate the warhead from the missile body after reaching a preset altitude and position, with the independent warhead completing the final strike. In terms of combat payload, missiles are classified as conventional missiles equipped with ordinary explosives and nuclear missiles carrying nuclear warheads.
2. Core Principle of Inertial Guidance
Inertial guidance is the most fundamental and mainstream autonomous guidance technology for missiles and launch vehicles. Based on inertial mechanics principles, it calculates real-time motion parameters of the carrier through high-precision inertial measurement devices, generates guidance commands via onboard computers, and adjusts the magnitude, direction and duration of engine thrust to automatically guide the missile to the preset target area.
The most prominent advantage of inertial guidance is full autonomy. The entire navigation and guidance process requires no external signal or environmental information, completely isolating from external interference. It has excellent anti-jamming capability and high concealment, making it the standard guidance solution for modern ground-to-ground tactical missiles, strategic ballistic missiles and aerospace launch vehicles.
A complete inertial guidance system consists of three core parts: inertial measurement unit (IMU), missile-borne computer, and servo actuator, all fully integrated inside the missile carrier.
3. Composition and Working Mechanism of Inertial Measurement Unit
The inertial measurement unit is the core sensing component of the inertial guidance system, mainly composed of a three-axis accelerometer and a three-axis gyroscope. It continuously outputs real-time three-axis acceleration and three-axis angular velocity data under the carrier coordinate system, providing all original motion sensing data for attitude solving and navigation calculation.
Through data solving and algorithm fusion, the IMU can obtain complete carrier attitude and motion information: acceleration data solves the roll and pitch angles, with Kalman filtering applied to eliminate sensor noise and improve stability; angular velocity data solves the yaw angle, which is further calibrated and compensated by a three-axis magnetometer. Real-time flight speed and cumulative rotation angle of each axis can be obtained by integrating acceleration and angular velocity data respectively.
3.1 Three-Axis Accelerometer Working Principle
The working mechanism of an accelerometer can be visualized through a simplified mechanical model: a mass ball is fixed at the center of a cubic shell by elastic springs. In a weightless static environment, the mass ball remains centered with zero acceleration on all three axes.
When the carrier generates linear acceleration, the shell moves synchronously with the carrier, while the internal mass ball stays relatively stationary due to inertia, clinging to the corresponding side of the shell. The sensor captures the offset of the mass ball and converts the mechanical displacement into electrical signals, solving the linear acceleration of the three orthogonal axes of the carrier.
3.2 Three-Axis Gyroscope Working Principle
Gyroscopes are core sensors for measuring carrier angular velocity and attitude deflection. Common types include mechanical gyroscopes, fiber optic gyroscopes (FOG) and MEMS micro-electromechanical gyroscopes. Its basic physical principle is the gyroscopic effect: under initial rotation and external torque, the high-speed rotating gyro rotor maintains a fixed axis direction and generates precession around the fixed axis.
By capturing the precession state of the rotor, the gyroscope can accurately detect the angular velocity and rotation angle of the carrier’s three-axis attitude changes, realizing real-time monitoring of flight deflection and attitude rotation.
4. IMU Attitude Solving Method
Taking the mainstream MPU6050 high-precision attitude sensor as an example, the device integrates a three-axis accelerometer and a three-axis gyroscope to complete full-dimensional attitude perception. When the sensor is fixedly installed coinciding with the missile body coordinate system (Z-axis vertically upward), the acceleration vector a(x, y, z) in the vertical direction can be acquired in a uniform motion state.
Based on vector inner product operation and geometric calculation, two core attitude angles of the missile can be accurately solved: thepitch angle is the included angle between the acceleration vector and its projection on the yaw plane; the roll angle is the included angle between the acceleration vector and the XOZ plane. Combined with gyroscope angular velocity data and Kalman filtering algorithm, high-precision, low-noise and stable full-attitude data output is finally realized.
5. Technical Summary
Missile inertial navigation relies on the autonomous sensing capability of accelerometers and gyroscopes. Without relying on any external navigation signals, it realizes full-process autonomous attitude solving, trajectory calculation and closed-loop guidance control. Its unique advantages of autonomy, anti-interference and high concealment make inertial guidance irreplaceable in the field of precision strike weapons and aerospace vehicle navigation.
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