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Meeting	ACGS Committee Meeting 104 - Charlottesville - October 2009
Agenda Location	4 GENERAL COMMITTEE TECHNICAL SESSION 4.1 Research Institutions, Industry, and University Reports 4.1.1 Research Institutes and Companies 4.1.1.5 Systems Technology Inc.
Title	Systems Technology Inc.
Presenter	David Klyde
Available Downloads*	presentation
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Abstract	Current Activities at Systems Technology Inc. A Complete Aeroservoelastic Model: Incorporation of Oscillation-Reduction-Control into a High-Order CFD/FEM Fighter Aircraft Model Flight testing for aeroservoelastic clearance is an expensive and time consuming process. Large degree-of-freedom nonlinear aircraft models using Computational Fluid Dynamics coupled with Finite Element Models (CFD/FEM) can be used for accurately predicting inviscid aeroelastic phenomena in all flight regimes including subsonic, supersonic and transonic. With the incorporation of an active feedback control system (FCS), these models can be utilized to reduce the flight test time needed for aeroservoelastic clearance. A complete CFD/FEM/FCS model can be used for full simulations including the dynamics of the fluid, the airframe, the actuators, and the FCS. Accurate CFD/FEM models are computationally complex, rendering their runtime illsuited for adequate FCS design. In this work, a complex, large-degree-of-freedom, transonic, inviscid CFD/FEM model of a fighter aircraft is fitted with a FCS for oscillation reduction. A linear reduced order model (ROM) of the complete aeroelastic aircraft dynamic system is produced directly from the high-order non-linear CFD/FEM model. This rapid runtime ROM is utilized for the design of the FCS, which includes models of the actuators and common nonlinearities in the form of rate limiting and saturation. An oscillation reduction controller is successfully demonstrated via a simulated flight test utilizing the high-order non-linear CFD/FEM/FCS model. Free Fall Analysis and Simulation Tool (FAST) Military Freefall (MFF), which includes both HALO (High Altitude Low Opening) and HAHO (High Altitude High Opening High Opening) operations, is among the most versatile techniques used by Army Airborne Special Forces. A spike in MC-4 main pilot parachute hesitation incidents in training led to a series of wind and water tunnel experiments. This work in turn suggested that digital simulation capability, specific to the aerodynamics and dynamics of MFF, would be valuable. This paper describes the initial development of the Free Fall Analysis and Simulation Tool (FAST) intended to meet this need. The core of FAST is a Computational Fluid Dynamics (CFD) program that implements the Cartesian grid immersed boundary method to simplify grid generation for complex and potentially non-rigid body shapes. Particular emphasis is being devoted to turbulence modeling for the complex and energetic wake. FAST includes a “digital manikin” that simplifies the generation of equipped body shapes in arbitrary poses for input to the CFD program. The digital manikin will also estimate the mass properties of the parachutist plus equipment. Capability will be implemented to combine the aerodynamic predictions from CFD with the mass properties to analyze free fall stability and control using linearized dynamics and nonlinear simulation.