Explain in detail about the importance of navigation with inertial sensors in uav.
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As explained in the Inertial Navigation: Basic Concepts article, inertial navigation requires a continuous update of position based on readings acquired from different sensors: accelerometers, gyroscopes etc. The Space Inertial Reference Earth (SPIRE) was the first inertial navigation system created in 1953 as part of the navigation system of a B-29 bomber for a flight from Boston to Los Angeles. It used gyroscopes and accelerometers to determine position without relying on the transmission or reception of external signals that might reveal the aircraft's position or make it vulnerable to enemy interference. It was the first truly successful demonstration of inertial navigation. However, it was a massive piece of equipment (1.5 m diameter and 1200 kg): Inertial navigation is vital underwater as the GNSS satellite signals cannot penetrate water and therefore any form of GNSS navigation is unavailable when the submarine is completely submerged. In 1954 an underwater version of SPIRE was released: the Shipboard Inertial Navigation System (SINS). Since then extremely accurate inertial navigation systems have been developed for submarines to allow very accurate navigation underwater for long periods of time. Another significant historical moment for inertial navigation was the APOLLO guidance computer which safely landed the Lunar Module on the Moon in 1968. Again, inertial navigation is of vital importance during space missions where it is not possible to use traditional GNSS constallations. The most precise inertial navigation sensors have been designed for use in nuclear submarines and intercontinental missiles. The most precise sensor unit was the Advanced Inertial Reference Sphere (AIRS), installed in ballistic missiles in the 70's. It has a drift rate of 1.5 x 10-5 º/ hour. However, AIRS features about 19,000 components and was extremely expensive to produce. Unsurprisingly, the general line of development over the years has been to miniaturize and improve the sensors from the type used in SPIRE to a small cube that took humankind to the moon. Nowadays, inertial sensors are tiny chips that can be integrated into many consumer devices. The progress of the technology has meant a reduction of components, less maintenance, lower costs, and more reliability. A visual representation of these trends can be seen in the following chart: This reduction in size and weight has been exploited to the full in the aeronautical industry, where sensor manufacturers produce units that can be integrated in UAV flight control systems. TYPES OF SENSOR Mechanical. Work on different mechanical principles: conservation of angular momentum for gyroscopes or Newton's second law for accelerometers. They include: RIG: Rate-integrating gyroscopes DTG: Dynamically tuned-rotor FLEX gyroscope DART: Dual-axis rate transducer. Vibration. Measure the change in heading based on the effect of the Coriolis acceleration in a vibrating mass. Optical. Based on the Sagnac-effect. This is the detection of the change in wavelength of light rays propagated in a circular path. They include: RLG: Ring Laser Gyros. FOG: Fiber-Optic Gyroscope. Cold atom sensors: Very high precision (still under development). MEMS. Microelectromechanical systems are based on integrated circuits. They incorporate miniature mechanical mechanisms at a very reduced scale, such as the following examples:
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