Active Control Of Gust Load Alleviation For A Two-dimension Airfoil

GLA is short for Gust Load Alleviation.It uses the active control to reduce the influence of gust interference,and to improve the passengers ride comfort,to reduce the bending moment of airfoil and enhance the structure fatigue strength.In this paper,the process of aerodynamic servo elastic(ASE)model was studied based on three degrees of freedom and two-dimensional airfoil,which involves gust model,unsteady aerodynamic force model and airfoil's dynamic model.Based on the theory of Duhamel integral and Wagner function,the unsteady aerodynamic force for any movement of airfoil was calculated;Based on the theory of Duhamel integral and Küsser function,the unsteady aerodynamic force for airfoil's angle of attack step change was calculated.Finally,the dynamic state equation of airfoil was established and its gust response under discrete gust and continuous gust was simulated by MATLAB.For gust load alleviation(GLA)active control,the optimal controller and the H_?controller were designed respectively.Its simulation results of GLA show that both optimal controller and H_?controller can effectively reduce the interference of gust on airfoil.But through further compared of two controller's GLA efficiency founds that the H_?controller has stronger robustness to the change of wind speed,gust frequency and gust amplitude,so the H_?controller has better GLA effect in simulation.In order to create gust environment needed in wind tunnel experiments,the gust generator was designed.The wind speed can be changed in vertical direction by the motion of a set of cascade installed in the wind tunnel exit.In order to achieve GLA servo control,a set of GLA servo control system with DSP as the core controller,ultrasonic motor as the actuator of control surface was constructed.Besides,the serial communication interface was designed based on MATLAB GUI,making data acquisition and control instruction execution more efficient.Finally,the wind tunnel experiments were carried to make a further inquiry for GLA active control.During the wind tunnel experiments,the gust response and GLA efficiency of airfoil were tested.The test results show that both optimal controller and H_?controller can not only reduce the interference of gust on airfoil effectively,but also can suppress the occurrence of flutter when the wind speed is higher than the critical flutter wind speed.Furthermore,a comparison of two controller's GLA efficiency and wind speed control limit show that H_?controller always maintains the GLA efficiency more than 30% when gust frequency range from 1 Hz to 7 Hz;H_?controller stillmake the airfoil's vibration stable convergence when wind speed reaches 24m/s while optimal controller has lost control to the flutter when wind speed reaches 20m/s,so the H_?controller has stronger robustness to the change of gust frequency and higher wind speed control limit.