Advanced Modeling and Control for Aeroservoelastic Design

It is well-understood that actuator nonlinearities, such as free-play, can induce limit cycle oscillations (LCO) in otherwise stable closed-loop systems. In flight control systems, free-play specifications are set conservatively in order to preclude free-play-induced LCO. However, conservative free-play requirements can increase the manufacturing cost of actuators and give rise to a costly program of regular inspections. Given the impracticality of experimentally determining appropriate free-play limits, an analytical method to safely relax free-play specifications could reduce actuator manufacturing and lifecycle costs. Importantly, in addition to accurate aeroelastic modeling to predict LCO, proven adaptive control methods exist to mitigate the effects of uncertain actuator nonlinearities, such as free-play. Thus, maximum benefit would be derived from a tool that combines improved aeroelastic modeling that explicitly addresses uncertainty effects with adaptive control techniques to relax free-play criteria and mitigate the adverse closed-loop effects of actuator free-play. Barron Associates, Inc., ZONA Technologies, Inc., Dr. Earl Dowell, and Dr. Gang Tao propose a Phase II effort that leverages team members'' expertise in aeroelastic modeling and adaptive control in the presence of uncertainty to develop and demonstrate Advanced Modeling and Control for Aeroservoelastic Design (AMCAD) - a software tool to facilitate the case-by-case analysis of free-play specifications. BENEFIT: Improved techniques for understanding the effects of uncertainty, free-play, and adaptive control on aeroservoelastic stability have potential applications to most air vehicles, including military fixed-wing aircraft, UAVs, and commercial and general aviation aircraft. Thus, the AMCAD Toolbox and the underlying technologies will have widespread military and commercial applicability.