Perturbation Analysis and Control of Mach Number 2.4-Meter Transonic Wind Tunnel

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Perturbation Analysis and Control of Mach Number 2.4-Meter Transonic Wind Tunnel

Yu, Wenshan / Du, Ning / Rao, Zhengzhou / Wei, Zhi / Yuan, Ping

Because of the large domestic civil aircraft projects started in China a decade ago, there is a greater need to control the accuracy of the Mach number in aerodynamic tests, especially near the designed cruise point of large commercial aircraft. Nowadays the control accuracy of China Aerodynamics Research and Development Center 2.4-meter transonic wind tunnel Mach number is in the range of $\pm 0.002$ to $\pm 0.003$ when $M \leq 0.9$ , which is far from the measurement accuracy of drag coefficient required for testing advanced aircraft. This value should result in a better-than-one drag count. As a consequence, it is imperative to improve the control accuracy of Mach number urgently. The nonlinearity, large time delays, and strong coupling of wind tunnel flowfield control, along with the variation of the model angle of attack, could cause the Mach number to deviate from the expected value. To solve these problems, a model predictive control method based on dynamic matrix control algorithm is proposed. This method builds a prediction model based on step response test. The accuracy of Mach number predictive control can be efficiently improved by performance optimization in the form of vector norms, rolling optimization, and feed-forward compensation. This control strategy has been successfully tested in the wind tunnel, and the control accuracy of Mach number has been remarkably enhanced, to the point where it can be controlled to within $\pm 0.0015$ . This value satisfies the requirements of aerodynamic aircraft testing.