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Autonomous vehicles require gyroscopes for navigation and stabilization of the platform in demanding battlefield, aerospace and undersea environments. Autonomous vehicles place tough demands on gyroscope technology, including extreme ruggedness, small-size, light-weight, low-cost, and low power operation. Also, slew-rates for gyros in autonomous vehicle applications can be very high and exceed the capabilities of many gyro systems.

Figure 1. Block diagram of a typical fiber optic gyro.

Optical gyroscopes such as fiber optic gyroscopes (FOGs) and ring laser gyroscopes (RLGs) are typically used when global positioning systems (GPS) or micro-electromechanical systems (MEMS)-based gyroscopes are insufficiently precise or when GPS signal access is denied or may be jammed. The duration of time required for operation in a GPS-denied environment, combined with the motions executed by the platform and the azimuth accuracy requirement over the mission duration, drive the requirements on the gyroscope drift rate. A larger drift rate leads to faster degradation of angle errors.

For autonomous navigating vehicles operating in GPS-denied environments, such as underwater or in urban settings with the possibility of jamming, the requirements on drift-rate can be significantly better than 1 degree per hour. This requirement, in conjunction with the environmental ruggedness requirements, practically eliminates the possibility of using anything but RLGs or FOGs.

Figure 2. Optical components in a modern highly-integrated fiber optic gyro

The closest alternative technology with high performance on the order of 1 degree/hour or better is the RLG, and these are widely deployed in many aerospace and precision munition applications. However, RLGs suffer from reliability concerns due to their hermetically-sealed gas lasers, high drive voltages and larger size, weight and power. In addition, the need for mechanical “dithering” of RLGs makes them ill-suited for many applications, especially covert or undersea. Micro-Electromechanical Systems (MEMS)-based gyroscopes are another alternative typically used for lower-precision applications with drift rates on the order of 10 degrees/hour or higher, but they have significant limitations for precise, rapid, and rugged applications.

It should be noted that available open-loop FOG technology is not considered an option for most navigation applications, due to performance limited typically to the order of 1-10 degrees/hr. This may be suitable for platform stabilization, but is not typically suitable for precision navigation applications in GPS-denied environments. Open-loop FOGs are gradually being replaced by MEMs solutions which can achieve similar levels of accuracy at greatly reduced cost, size, weight and power.

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