A Look at Gyroscopes in INS

Navigational Map

An inertial navigation system (INS) has been around since World War II. Its original purpose was to guide rockets, and it does not need an outside source of information. This makes it immune from hacking or disruption.

However, its moving parts can cause problems in accuracy rates over time. This is particularly true for gyroscopes. An INS simulator tests the extent of these errors depending on the type of gyroscope. Here are the three basic types:

Mechanical

The mechanical gyroscope is the oldest type of INS gyroscope and is used to measure direction. It has a spinning wheel on two gimbals, which allow the wheel to rotate in a clockwise motion. The gimbals keep changes of direction from affecting the wheel. This means that the gimbals change position, while the wheel keeps pointing in one direction the whole time.

Optical

An optical gyroscope measures angular velocity or rate of change in the angle of whatever is rotating. It doesn’t measure direction like a mechanical gyroscope. It also does not have moving parts. It uses the Sagnac effect on light to measure the angular velocity.

The Sagnac effect has something to do with how a spinning disc affects the speed at which light travels. The light around a spinning disc tends to take longer to travel in the same direction as the disc. In a fiber optic gyroscope (FOG) INS, the spinning disc is the Earth and the light is a fiber optic cable with light beams fired in opposite directions. The computer can sense a change in the angle by measuring the power of the light coming out.

MEMS

A micro-machined electromechanical system (MEMS) gyroscope uses silicone to measure vibrations. It also measures angular velocity like optical gyroscopes. However, it uses the Coriolis effect instead. This has to do with an interesting thing that happens with a free moving object. If it is moving towards the north, it will deflect to the right. If it is moving towards the south, it will deflect to the left. MEMS gyroscope is a new INS technology, so it’s not yet as accurate as optical gyroscopes are.

These three types of gyroscopes use different things to figure out how something is moving. This means each one will require a different type of INS simulator.