System Identification of Pneumatic Dynamics for Active Flow Control Aircraft

Abstract

This paper applies frequency and time domain system identification techniques to formulate a reduced order transfer function that describes the internal pneumatic dynamics within an active flow control aircraft using circulation control. The identified transfer function represents a simplified model of the coupled nonlinear pneumatic flow between multiple components within a pneumatic network, including supply tanks, ducting, valves, and plenum volumes. The input to this system consists of valves modulated to affect the airflow from a pre-charged supply tank, through a network of ducts, and out of an exit slot area located at the aileron of the wing. The output of the system is the momentum coefficient that is directly related to the localized lift generated at the aileron. The system identification results indicate that two separate regions form within the open loop dynamics of this configuration and describe the charging and discharging of the system. Both the charging and discharging dynamics can be estimated from an identified transfer function that shows agreement with a second order system. An alternate identification method from the MATLAB system identification toolbox demonstrates agreement with a second order formulation with some phase angle differences.