Active Control Of Gust Load Alleviation For A Two-dimension Airfoil With Time-delay Feedback

In the active control of the gust load alleviation,researchers usually use sensors to collect the flight state parameters for the controller,then the controller calculates the control command and send it to the actuator,and the actuator controls the aileron deflection to change the force of the aircraft for reducing gust load on the aircraft.Researchers often overlook the existence of time-delay factors during the process.In this paper,the three degrees of freedom two-dimensional wing'model is taken as the research object.Considering the influence of time-delay factors,An aeroelastic model of gust load alleviation for a two-dimension airfoil with time-delay feedback is established.The active controllers of gust load alleviation are designed,and the experimental platform of gust load alleviation is built.Combining numerical simulation with wind tunnel experiments,the effects of controller on gust load alleviation efficiency and filter group delay on gust load alleviation are verified.The main research contents are as follows.(1)The aeroelastic model for the wind load of the two-dimensional airfoil with time-delay feedback is established.The differential equations of the two-dimensional airfoil are established using the Lagrange equation.Based on the Theodorsen aerodynamic theory,Wagner function and Küsser function,the state equation of the wing based on unsteady aerodynamic force is introduced.Considering the influence of time-delay factors,the amount of time delay existing in the system is introduced into the system state equation.Transform state equations in a continuous system into discrete systems by the discretization method.(2)Design of active controller for gust load alleviation with time delay.Firstly,the time-delay system is turned into a delay-free system by discrete state transform method.Then two time-delay LQ controllers are designed based on optimal control theory.The H_? controller and ? controller are designed based on the robust control theory.Finally,the digital filter is designed to generate the group delay to construct the filtering and time lag of the system.(3)Experiment platform for gust load alleviation of the two-dimension airfoil is established.The structural parameters of the three degrees of freedom two-dimensional wing'model were measured,then the photoelectric encoder and the laser displacement sensor were selected to measure the flight state parameters.An ultrasonic motor was used as an actuator for driving the control surface,and the PID control program of the DSP was developed to control the rotation of the ultrasonic motor.Based on Qt and Python,the upper computer software is used to realize DSP and PC communication and experimental data visualization in experiments.(4)The active control system for the gust load alleviation of the two-dimensional airfoil is verified by the combination of numerical simulation and wind tunnel experiment.In the sharp-edged gust environment,the discrete effects of different discretization methods on the system equations are compared by numerical simulation.In the harmonic gust environment,the effects of filter group delay on gust load alleviation and the influence of different controllers on gust load alleviation efficiency are verified by numerical simulation and wind tunnel experiments.The simulation and experimental results are also analyzed and compared.Both simulation and experimental results show that the efficiency of the gust load alleviation is affected by the filter group delay.Reasonable use of digital filter noise reduction can improve the performance of the control system and improve the gust alleviation efficiency,but when the filter group delay become large,the gust alleviation efficiency will reduce,and even the controller failure occurs.In addition,the time-delay LQ controller based on discrete variation is more efficient against gust load alleviation than the time-delay LQ controller based on output feedback.