Subsonic and Transonic Mach Number Tracking Control Strategy Design and Application in an Intermittent Wind Tunnel

In order to ensure the quality of test data, the Mach number control deviation should be kept within a given range during the continuous-traverse mode force measurement test in a wind tunnel. Currently, when establishing the continuous-traverse mode force measurement test technique in a one-meter-scale sub-transonic and supersonic wind tunnel, the maximum Mach number control deviation exceeds the given range (0.003) under the conditions of sub-transonic speed, large model blockage ratio and wide angle of attack range. This deviation fails to meet the test requirements. By analyzing the process of sub-transonic Mach number adjustment, it is found that the significant Mach number control deviation arises due to two main factors: first, the static pressure fluctuates substantially as a result of changes in the angle of attack; second, the choke finger fails to adjust accurately and eliminate these static pressure fluctuations in real time. To achieve Mach number control deviation less than 0.003, a Mach number tracking control strategy has been proposed, which is based on the choke finger model predictive control algorithm with feedforward-feedback structure and choke finger compensation algorithm. The proposed strategy has been successfully implemented in continuous-traverse mode force measurement test. The test results show that the Mach number control deviation remains within the given range of 0.003 by using Mach number tracking control strategy, and the strategy has good robustness under the condition that the model blockage ratio is less than 0.69%.