Control of Blow-Down Wind Tunnel Using Combined Extended and Nonlinear Predictive Filters

Abstract

A blow-down wind tunnel is a typical nonlinear time-variant system facing the coupling of the pressure and temperature during a short duration. The control of blow-down wind tunnels has been discussed for long time and a satisfactory general solution to this problem is still under developing. This paper aims to model the internal relationship of the state variables of the wind tunnel by using thermodynamic theories. With the developed model, a new control method combining Extended Kalman Filter (EKF) together with auxiliary Nonlinear Predictive Filter (NPF) is proposed to improve the control performance of the blow-down wind tunnel controller in terms of precision and robustness. The transient coupling effects between the pressure and temperature are fully considered by the proposed approach. The results both from the simulation and experiments are consistent and prove that the EKF combined together with NPF can work better than previously proposed EKF-based method.