Controlling Sideslip Angle to Reduce the Radar Exposure of a Tactical, Rotary Winged UAV

This work investigates another way of contributing to the radar minimization solution for air vehicles in a threat environment. While muchresearch has been conducted on structural solutions to radar exposure minimization, not much work has been done in the area of using control tocontinuously assess and present the smallest radar cross section of an air vehicle to oncoming threat radar systems by changing the aircraft'sorientation. This work looks at the application of sideslip/beta angle feedback control of an unmanned helicopter to minimize radar crosssection exposure in a hostile radar environment. A new way of controlling aircraft trajectory is introduced that incorporates both path andorientation optimization feedback; the aircraft's heading is controlled to orient the vehicle in a way that reduces its radar cross section, whilesideslip angle is used to control the aircraft's path. A representative hostile environment is created and results show that a substantial reductionin radar cross section exposure can be achieved with beta feedback control. A linear state space model is derived for the OH-6A helicopter withthe JANRAD software program. Eigenstructure assignment is used to shape the response of the helicopter into desired response modes. AMatlab based flight control system is developed around the derived helicopter model with altitude, heading, and beta angle command signalsthat drive four conventional helicopter control inputs.

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