Multivariable control of regeneratively-cooled scramjet engine with two-stage kerosene injection based on H∞ method

Aimed at diversity of hypersonic flight mission, this paper discusses the multivariable control of regeneratively-cooled scramjet engine with two-stage kerosene injection for both safety operation and high performance. Firstly, the multivariable control strategy is proposed to solve the inlet unstart and overtemperature control issues. There are two linear models identified for different control objects because of the control strategy. Among them, the inputs are two-stage fuel equivalence ratios, and the outputs are thrust, inlet steady margin, and thrust and kerosene temperature at cooling channels outlet, respectively. Secondly, H∞ multivariable control method is introduced. The standard H∞ control problem with structural uncertainty is constructed in detail. In order to settle the issue that the control strategy selects various controlled output variables under different flight missions, a switching controller based on controller output reset is proposed. Lastly, not only thrust and steady margin control loop, but also thrust and fuel temperature control loop of the regeneratively-cooled scramjet engine are established. Simultaneously, the switching system with the two control loops is designed in this paper. Simulation results indicate that rapid responses of control system, smooth and steady switching between different loops are realized. The engine with control system can operate steadily with high performance at both specific and variable operating conditions.