Will MEMS repeat the cycle?
This is a question worth exploring, considering that MEMS technology has advanced a lot in recent years, with MEMS gyroscope sensors achieving higher accuracy, improved error characteristics, and better g sensitivity, thereby significantly improving the overall MEMS performance. These two technologies are now routinely going head-to-head in tactical and navigation-level applications, with no clear winner.
Choosing inertial technology used to be an easy decision, but as the competition between the two approaches heats up, navigation engineers are now forced to consider many factors before choosing either solution, depending on their specific application.
FOGs still dominate in critical applications
Fiber remains the proven solution for high-end applications, gradually replacing aging RLG technology where possible. The technology still offers unrivaled performance thanks to its extremely low-noise fiber optic gyroscope for extremely precise navigation, and low bias instability and drift relative to other technologies, which is critical in GNSS-denied environments Staying up and running is critical.
FOG INS is indeed considered more suitable for critical navigation solutions such as deep sea underwater navigation and aerospace applications. While its high cost makes it prohibitive for the low-end market, less price-sensitive end users such as military and commercial aircraft manufacturers are happy to pay more for the added extra precision. Its inherently lower drift also makes it the first choice for long-duration GNSS denial applications, as the overall error margin is lower than even the most accurate MEMS INS available.
Due to its fixed mount and lack of moving parts, the FOG is also well suited for stealthy operations, where any type of low frequency vibration can give away its position to an enemy. This is especially true for older mechanical inertial navigation systems, but less so for newer generations of MEMS that now offer negligible vibration levels for such applications.
Another feature unique to FOG that makes this technology so attractive is its ability to find north, even in strong magnetic environments. Contrary to MEMS technology, which relies on magnetometers for accurate heading, FOG precisely measures the Earth's angular rate of rotation, even while in motion, and can accurately determine north in minutes. This is a particularly welcome feature for subsea applications that cannot rely on any GNSS signals for extended periods of time.
Both FOG and MEMS accuracy are affected by temperature changes. This problem can often be mitigated by calibrating the system over a range of extreme temperatures. However, be aware that due to the mechanical nature of MEMS, it may be more difficult to properly calibrate MEMS. FOG, properly insulated and calibrated, will perform better.
Finally, FOG INS is not immune to errors in vibration-prone environments. However, since FOGs don't have any moving parts, they can handle vibration better than their MEMS counterparts. As such, FOG is the method of choice for heavy equipment stabilization in mining and industrial applications, as well as in aerospace, where aircraft, especially their wings, are subject to very high vibrations.
