Introduction

An Inertial Navigation System (INS) is an autonomous navigation technology that relies on inertial sensors—mainly gyroscopes and accelerometers.
Since INS does not depend on external signals, it offers:

• High stealth
• Strong anti-interference capability
• All-weather operation

INS is widely used in aerospace, UAVs, marine navigation, autonomous vehicles, robotics, and defense.
A solid understanding of INS begins with Newton’s Laws of Motion, which form the theoretical foundation of inertial navigation.

Keywords: Inertial Navigation, Inertial Sensors, INS, Newton’s Laws, UAV Navigation, Autonomous Vehicles

1. Theoretical Basis: Newton’s Three Laws

1.1 Newton’s First Law – Law of Inertia

“An object at rest stays at rest, and an object in motion continues in uniform motion unless acted upon by an external force.”

This law reveals the inertia property of objects.
INS uses this principle to measure changes in the motion state of the carrier in inertial space and calculate position, velocity, and attitude.

Keywords: Inertia, Motion State Estimation, Inertial Sensors, INS

1.2 Newton’s Second Law – Dynamics

“The acceleration of an object is proportional to the applied force and inversely proportional to its mass, a = F/m.”

Accelerometers work based on this principle by measuring specific force, which is integrated to obtain velocity and displacement.

Keywords: Accelerometer, Dynamics, Specific Force Measurement, IMU, Motion Equations

1.3 Newton’s Third Law – Action and Reaction

“For every action, there is an equal and opposite reaction.”

In INS, this principle appears as the mechanical coupling between sensors and the carrier—crucial for vibration control, error compensation, and system modeling.

Keywords: Mechanical Coupling, Error Compensation, Inertial Navigation Algorithm

2. Inertial Frame: Reference for Navigation

Newton’s Laws are valid only within an inertial reference frame.
INS typically uses:

• Earth-Centered Inertial (ECI) frame
• Navigation frames, such as NED (North–East–Down)

These frames allow accurate trajectory calculation.

Keywords: Inertial Frame, ECI, NED, Reference System, Trajectory Calculation

3. Components and Key Technologies of INS

A standard Inertial Navigation System consists of:

• IMU (Inertial Measurement Unit)

3-axis gyroscopes + 3-axis accelerometers

• Navigation Computer

Runs Strapdown Inertial Navigation System (SINS) algorithms

• Kalman Filter

Provides multi-sensor fusion and systematic error correction

Advancement in MEMS technologies has made INS more compact, cost-effective, and precise, enabling broader applications in:

• Autonomous vehicles
• Robotics
• UAVs
• Wearable intelligent devices