Research On Predictive Control For Wind Tunnel Flow Field

Developing large aircrafts puts forward almost harsh requirements for wind tunnel flow field precision,but existing control methods cannot meet the high-precision requirements in flow field.Predictive Control is able to realize high-precision control because it optimizes control law based on predictive future control deviation.Therefore,this thesis takes an intermittent transonic wind tunnel as the plant,and researches employing Predictive Control to realize high-precision wind tunnel flow field.The structure of this intermittent wind tunnel and the features of its blowing tests are analyzed in this thesis.Considering the diminishing air source pressure will change the flow field characteristics over time,the main ejection pressure loop is introduced in the control system,which contributes to eliminating the impact of the diminishing air source pressure on the flow field.As Mach number is calculated by a nonlinear equation,the controlled variables are selected as stagnation pressure and static pressure to reduce nonlinearity.By analyzing the step response data,it is found that the flow field is a plant with coupling and time-lag.Predictive Control combines plant dynamic characteristics,so it can cope with the coupling and time-lag easily,and thus employing Predictive Control to regulate wind tunnel flow field is reasonable.Because step response model can exactly describe plant dynamic characteristics and it is feasible to measure step response data in the wind tunnel flow field,step response model is used as the predictive model.Considering the main task of wind tunnel controller is to eliminate control deviation,the traditional quadratic index is selected as the optimal cost index.As the intermittent wind tunnel tests require the control system can regulate the flow field rapidly,the controller adopts the less-calculation feedback correction based on predictive control errors.Based on the above-mentioned,the Multivariable Dynamic Matrix Control is selected as the wind tunnel controller.In order to improve the capacity of the wind tunnel to resist the disturbance caused by the angle of attack,this angle is used to compensate the prediction of static pressure.Consequently,the wind tunnel flow field feedforward dynamic matrix controller is constructed.According to the wind tunnel flow field approximation model,the angle of attack approximation model,and engineering experience,the method to tune wind tunnel flow field controller parameters is researched.The designed wind tunnel predictive controller is realized by Lab VIEW software.It is verified that the controller can effectively regulate the wind tunnel flow field and ensure wind tunnel tests reach the required precision,which illustrates the proposed controller is effective.Furthermore,the repeatability and the robustness are verified in the corresponding practical wind tunnel tests respectively.