大型液体火箭姿控与跷振大回路耦合动力学建模与分析

大型液体火箭结构模态的空间化分布特征导致结构振动、姿态运动和推进系统液路脉动存在相互耦合,进而影响传统姿控回路的稳定性. 针对大型液体火箭, 充分考虑姿态控制系统对箭体姿态动力学和弹性振动的影响, 以及箭体结构弹性振动与推进系统的耦合作用(跷振(POGO)), 建立了姿控与跷振大回路耦合模型. 该模型包含了推进系统、结构系统与姿控系统之间的耦合因素, 可进行姿控-结构-推进大回路耦合机理研究. 该模型具有非奇异的优点, 可以直接用于频域分析和时域仿真. 基于该模型研究了我国某型号液体捆绑火箭推进系统参数——泵增益和蓄压器能量值对姿态运动与结构振动稳定性的影响. 研究得出, 泵增益和蓄压器能量值的变化不仅导致了结构振动的不稳定, 而且也导致了姿态运动的发散. 因此, 对于大型液体捆绑火箭, 推进系统与姿控系统之间存在不可忽略的耦合作用, 在设计姿控系统时, 有必要考虑推进系统对姿控系统稳定性的影响. 

DYNAMIC MODELING AND ANALYSIS OF LARGE-LOOP COUPLED BY ATTITUDE CONTROL AND POGO FOR LARGE LIQUID ROCKETS

Coupling effect always exists between structural vibration, attitude and propulsion system because of the spatial distribution characteristics of the structural vibration mode of large liquid rockets. The coupling model of attitude control-structure-propulsion system is derived to investigate the effects of the propulsion system on the stability of attitude control system. The coupling is based on mechanism that the effects of attitude control system on the attitude motion and structural vibration as well as the interaction of propulsion system and structural vibration. By including the coupling factors between the propulsion system, structural system and attitude control system, the large-loop coupling model can be used to investigate the coupling stability of the large-loop coupling system. Besides, the coupling model can be directly used for frequency-domain analysis and time-domain simulation for the non-singularity. Based on this model, the effects of the propulsion system parameters-pump gain and accumulator energy value to the stability of attitude control system are analyzed by frequency domain analysis and time domain simulation. The results show that the variations of parameters-pump gain and accumulator energy value not only result in the instability of structural vibration but also lead to the instability of attitude motion. It is concluded that it is necessary to take the effect of POGO loop into count in the design of attitude control system.