Historical Technological UAS Advancements in Navigation

     Technology we take for granted today in our phones, cars, airplanes (autopilot), satellites, and tablets, had their beginnings in unmanned flight during the early 20th century. The first military contract for unmanned flight was received in 1917 by Lawrence and Elmer Sperry to develop an aerial torpedo for the US Navy (Blom, J. 2010). Sperry is known for designing the first gyroscope capable of keeping a plane level during flight. Elmer Sperry, who previously shared ideas with Tesla (remote control via radio waves) and had help from Glenn Hammond Curtiss during his design, displayed this marvel in June 1914 while flying his Curtis N-9 in an airplane safety competition (Soff, J. 2015). Sperry took his hands off the flight controls, raised them, and had his mechanic walk onto the wing showing that the plane was still flying straight and level. This was the first primitive expedition of what you might call “autopilot”.

     The Curtiss-Sperry Aerial Torpedo program is considered the first guided missile program in the US. The torpedo which appears as a small airplane was launched on a special track dolly and catapulted at which time the “flying bomb” would take to the skies in a somewhat autonomous state and after a certain amount of time the torpedo would drop onto a predetermined target or location (Soff, J. 2015). The successful test of the aerial torpedo on March 16th, 1918 is considered the first flight of an automatically controlled unmanned aircraft. During World War II the Germans took the concepts a bit further through the combination of gyroscopes, accelerometers, and a simple analog computer for rocket flight of the V-2 and was the worlds first long range guided ballistic missile. The technology at the time was a game changer, although primitive, but evolved into what we now call Inertial Navigation Systems or Inertial Measurement Units used in various modern day flight applications such as UAV’s, Drones, RPV’s, and unmanned (and manned) aircraft in general.

     Gyroscopes allow for stable flight of flying vehicles through maintaining and measuring angular motion. The concept in 1917 is the same as today however since the introduction of transistors and integrated circuits most gyros used are now what are called MEMS Gyroscopes. MEMS (micro-electro-mechanical systems) Gyros are the less expensive, small, lightweight, and take advantage of the piezoelectric effect for functionality through vibration converting a physical force into an electrical signal. Accelerometers measure non-gravitational acceleration such as an object sitting at a standstill and moving to any non-zero velocity. Once again the Piezoelectric effect is utilized to produce acceleration data. Types of Gyros and Accelerometers used for inertial navigation systems vary based on application from vibrating, quartz, Hemispherical, MEMS, gimballed, fiber optic, pendualr, and strapped down.

     Inertial Navigation is ideal for remotely piloted vehicles and unmanned systems due to the ability for “self referencing” meaning, a system can track its own position, orientation, and velocity, without the need of any type of external references (UST, ND). Standard IMU’s contain three accelerometers and three gyroscopes mounted orthogonally. Modern day IMU’s provide the advantage of holding up in harsh environments, don’t emit signals that are detectable, and are not susceptible to jamming. Some disadvantages include accuracy, which is based upon the type of sensors chosen for an application as well as the multitude of precious made mechanical parts that are susceptible to friction and wear (Austin, R. 2010).

     Modern day UAV’s, drones, and RPV’s such as the Global Hawk, Reaper, Predator, Hunter, and Pioneer mostly use a combination of an inertial navigation system and global position system allowing for high and medium altitude long endurance missions. Shorter range mission and line of sight operation only require radio tracking navigation but will utilize an INS in case of a lost signal (Fahlstrom, P. 2012). GPS has vastly extended the range of navigation but also has shortcomings which is why INS, TACAN, and LORAN C are used as fall-back plans and still being developed in some locations (Austin, R. 2010).

     UAS technologies have grown by leaps and bounds allowing for improved operation with navigation being a critical aspect. The UAV must be able to get to and possibly from the required destination safely which has required many years of development, testing, technology advancements, and lessons learned. Regardless of the various payloads onboard an unmanned vehicle, navigation technology is the key component for a successful flight in order for a UAV to be controlled and understand its surrounding environment regardless of location or conditions.

References

Austin, R. (2010). Unmanned aircraft systems: UAV design, development and deployment. West Sussex, United Kingdom: John Wiley & Sons.

Blom, J. (2010). Unmanned aerial systems: A historical perspective (p. 45). Fort Leavenworth, Kan.: Combat Studies Institute Press
from http://usacac.army.mil/cac2/cgsc/carl/download/csipubs/OP37.pdf (Links to an external site.)

Fahlstrom, P. (2012). Introduction to UAV Systems: 4th edition. West Sussex, United Kingdom: John Wiley & Sons.

Soff, J. (2015). Historic Aircraft and Spacecraft in Cradle of Aviation Museum. Dover Publications.

UST. (ND). Unmanned Systems Technology: Intertial Naviation Systems. Retrieved from http://www.unmannedsystemstechnology.com/category/supplier-directory/navigation-systems/inertial-navigation-systems/#introduction

Whittle, R. (2013, April). The man who invented the Predator. Air & Space Magazine. Retrieved from http://www.airspacemag.com/flight-today/the-man-who-invented-the-predator-3970502/?no-ist=&page=4