Transactions of Nanjing University of Aeronautics & Astronautics
A Dynamic Matrix Controller with Feedforward for Flow Field in Intermittent Transonic Wind Tunnels
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Abstract:
Intermittent transonic wind tunnels demand high-precision and stable control of Mach number and stagnation pressure during the variation of model angle of attack， while the traditional proportional integral derivative （PID） control strategy fails to achieve the Mach number control error target of 0.001 and is inept at resisting flow field disturbances caused by rapid changes in angle of attack. Aiming at this problem， this study takes the intermittent transonic wind tunnel of China Aerodynamics Research and Development Center as the research object and optimizes the wind tunnel control system for its characteristics of multi-input multi-output （MIMO）， large time delay and nonlinearity. First， the control system structure is reconstructed by introducing ejection pressure as a controlled variable to reduce the time lag from the main pressure regulating valve to the test section， and selecting static pressure instead of Mach number as a controlled variable to weaken the nonlinear coupling between Mach number and static pressure. Second， based on the first-order plus dead time process model of the wind tunnel， a MIMO dynamic matrix controller （DMC） for wind tunnel flow field is designed. Considering the predictable nature of angle-of-attack changes， a feedforward compensation strategy is integrated into the DMC to mitigate the pressure disturbance in the test section caused by the variation of angle of attack. Third， a complete tuning strategy for DMC parameters including sampling time， prediction horizon， control horizon and weight coefficients is formulated according to the wind tunnel model parameters under different Mach numbers. Experimental validations through practical blowing tests are carried out at Mach numbers of 0.578， 0.675， 0.714 and 0.822 to compare the control performance of the proposed feedforward DMC strategy with the traditional PID control and DMC without feedforward compensation. The results show that the proposed strategy stably controls the Mach number error within 0.001， and significantly improves the stagnation pressure control accuracy and anti-disturbance capability of the wind tunnel flow field. Moreover， the strategy exhibits excellent repeatability and robustness under different Mach number conditions. This study effectively solves the problem of high-precision flow field control under the rapid change of angle of attack in intermittent transonic wind tunnels， and provides a technical reference for the flow field control of complex fluid test devices such as hypersonic wind tunnels.
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V211.74
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