Research On Predictive Control Method Of Flow Field Of High Mach Number In FL-26 Wind Tunnel

It needs to do high precision aerodynamics tests in wind tunnel for the design and development of China's large aircraft.It is an important guarantee for the successful development of large aircraft in the condition of high Mach number,which the precision of Mach number in the wind tunnel is 0.001.And the FL-26 wind tunnel is the only platform for the development of large aircraft,its control precision of the PID control algorithm can reach 0.003 of the Mach number.Then we designed a predictive controller with compensation model of angle of attack and achieved the precision of 0.001 in the condition of normal pressure and low Mach number.But the real test needs to be carried out in the condition of high Mach number and high total pressure.So we study the characteristics of the flow field of high Mach number and high total pressure,and use a way of correcting the angle of attack compensation model to make it.Firstly,we study the physical quantity which affect Mach number,consider the structure of wind tunnel and characteristics of angle of attack.So we use predictive control algorithm to control the system of two inputs and two outputs,which main exhaust valve and choke finger are inputs,total pressure and static pressure are outputs.It is necessary to study predictive control algorithm in the condition of high Mach number and high total pressure.It boosts the gas compressibility under the condition of high Mach number and high total pressure,the static pressure at the measuring point is more difficult to control with the increase of the gas compressibility when angle of attack changes.So we have to choose step response data as a prediction model.And we use compensation model of angle of attack to decrease disturbance caused by angle of attack.Because we have known the influence of angle of attack to static pressure is the main disturbance in flow field.Secondly,we lack compensation model of large angle of attack in the condition of high Mach number because of the intense vibration of the aircraft model tail,so we use an approximate model to replace it and get the data.Consider the predictive control algorithm and the data,we use genetic algorithm to correct the approximate model again and again to make Mach number maintain at a certain accuracy.When the supporting way of the aircraft change from the rear support into abdominal support,the compensation model of large angle of attack changes a lot,we use the correction method for angle of attack compensation model in this condition.And we get a good result.It proves the effectiveness of the method.Last but not least,we design the high Mach number controller in flow field based on Labview,to make the testing process clearer,we add many convenient and practical operation functions in the main display interface,controller parameter setting interface,parameter display interface.It enhances the operability of the controller.We show the effect of controlling the Mach number in many conditions and achieve the goal of Mach number accuracy to 0.001.