Time-delay effect and design of closed-loop control system of circulation control airfoil

In this paper, unsteady numerical simulation of jet Circulation Control (CC) is carried out with the NACA0012-CC airfoil as the research object. The dynamic process from the opening of jet slot and adjustment of jet intensity to the stable state of jet control effect is explored. The time-delay effect and flow mechanism of jet are analyzed. The mechanism of jet momentum coefficient and moment coefficient fluctuating with time is revealed. The fluctuation of jet momentum coefficient is caused by the change of the pressure coefficient distribution on the Coanda surface or the structure of the wave system inside the jet, and the oscillation frequency of the wave system structure of the under-expansion supersonic jet reaches 1481 Hz at the opening moment. Based on the aerodynamic model and Proportional-Integral-Derivative (PID) control theory, the closed-loop control system of CC airfoil is designed. The parameters of PID control system are adjusted by the Genetic Algorithm (GA), which significantly improves the response ability of the control system to step, ramp and sine signals, and improves the dynamic performance of the system. Aimed at the special time-delay effect of jet control, Long Short-Term Memory (LSTM) neural network module is added to the control system to predict the target input signal, which strengthens the prediction ability of GA-PID control system to the target signal at the next time moment. By using LSTM neural network correction, the control hysteresis caused by jet time-delay effect is alleviated, and the response ability of the control system is effectively improved. Finally, the designed LSTM-GA-PID control system is applied to the NACA0012-CC airfoil for the pitch control simulation test. The test results show that the control system designed in this paper has good dynamic performance and can respond quickly and accurately to complex input signals, which confirms the effectiveness of the control system.