Study On Control Methods For Variable Flow Ducted Rockets

The control of gas generator is a key technology for ducted rockets. With the improved performance of ducted rocteks, research on gas control of gas generator has been enhanced in resently years. The gas regulation and engine control for variable flow ducted rockets were investigated in the paper.Firstly, the structure of pneumatic needle-type gas control valve was deisigned, and the regulating property of gas control valve was analyzed. With respect to the basic structure of gas control valve, the design methods and design results were presented. The sealing material of gas control valve and pressure control valve were selected. The regulation property of gas control valve was analyzed through numerical simulation, and the parametric expression of regulating property for gas control valve was obtained.Secondly, the modeling and control system of gas regualtion system were studied. The dynamic models of two regulating modes of gas regulation system were established, and the characteristic of these two modes were compared by introducting nonlinearity measure. The parameter varying characteristic and negative modulation were analyzed. Studies show that the nonlinearity of the pressure-balanced mode is weaker and the output is less sensitive to parameter uncertainty. The introduction of high-gain feedback suppresses the effects of nonlinearity and uncertainties of the pneumatic servo system and a proportional-integral (PI) controller for gas regulating system was designed. Two friction compensation methods were studied in the paper, one method is based on the adaptive dither signals, and the other is based on the quasi-integral controller. Simulations show that these two methods can compensate the friction in gas regulation system.Then, cold experiments and hot experiments of gas regulation system were conducted. Firstly, cold test-bed and hot test-bed were designed. The cold experiments of friction compensation based on dither signals and control of pneumatic servo system were conducted. And the hot experiments of gas depositon and gas consumption in gas regulation systm were controducted. The method of reducing gas consumption and the fluence of structure and material of control valve to gas depositon were analyzed. Extensive closed-loop control experiments were conducted, and the results of experiment show that pneumatic needle-type gas control valve can effectively control the pressure in gas generator, and gas control system has good performance. The turndown ratio of mass flow is up to 4.36:1, and the time of gas regulation is greater than 100 seconds.Finally, the basic control structure of variable flow ducted rockets was proposed, and the control system of ducted rockets was investigated. A dynamic model of varlable flow ducted rockets was established. Based on the model, the parameter varying characteristic and negative regulation were analyzed. According to the characteristic of non-minimum phase system extised in variable flow ducted rockets, a thrust contol method based on data fusion in frequency domain and the unstart margin control of hypersonic inlets were proposed for preventing inlet unstart. The defference of inlet unstart margin control was discussed because of negative regulation in ducted rockets. And switch system of ducted rockets was investigated, the switch process of thrust control loop and inlet unstart control loop was analyzed, and the fluence of integration limits in thrust loop and inlet margin loop to switch process was discussed.