MULTIPLE-FUNCTION DIGITAL CONTROLLER SYSTEM FOR ACTIVE FLEXIBLE WING WIND-TUNNEL MODEL

A real-time multiple-function digital controller system was developed for the Active Flexible Wing program, which demonstrated through wind- tunnel tests that digital control can be used with greet versatility t o perform a multifunction task such as suppressing nutter and reducing loads during rolling maneuvers. The digital controller system (DCS) a llowed simultaneous execution of two control laws: 1) nutter suppressi on and 2) either roll trim or a rolling maneuver load control. The DCS operated within, but independently of, a slower host operating system environment, at regulated speeds up to 200 Hz. It also coordinated th e acquisition, storage, and transfer of data for near real-time contro ller performance evaluation and both open- and closed-loop plant estim ation. It synchronized the operation of four different processing unit s, allowing flexibility in the number, form, functionality, and order of control laws, and variability in selection of sensors and actuators employed. Most importantly, the DCS enabled successful demonstration of active nutter suppression to conditions approximately 26% (in dynam ic pressure) above the open-loop boundary in cases when the model was fixed-in-roll, and up to 23% when it was free-to-roll. Aggressive roll maneuvers with load control were achieved above the nutter boundary. The purpose of this article is to present the development, validation, and wind-tunnel testing of this multiple-function digital controller system.