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为提高控制策略的效率,考虑航天器的平动和转动与柔性附件的振动相互耦合作用,对一种用于估计柔性附件对自由漂浮航天器主体平动和姿态转动影响的非线性扰动观测器(NDO)设计进行了研究。将自由漂浮航天器简化为自由运动的中心刚体柔性梁(FHB)系统,用浮动坐标系建立了系统的动力学模型,并用假设模态法对柔性附件进行离散以方便计算。将与不可观测状态相关的项作为等效扰动项,并假设其为慢变且有界,设计了扰动观测器。因考虑了柔性附件对航天位姿的扰动,设计的扰动观测器具渐近收敛性和鲁棒性。构建了Lyapunov函数,从理论上证明了该观测器的收敛性。用无外力输入的自由运动和受迫运动两个数值仿真算例验证扰动观测器的有效性,结果表明设计的扰动观测器估值与真实值基本一致。研究为后续包含扰动补偿的控制器设计奠定了基础。
In order to improve the efficiency of control strategy, considering the interaction between the translation and rotation of the spacecraft and the vibration of the flexible attachment, a nonlinear perturbation observer for estimating the influence of the flexible attachment on the translation and attitude rotation of the free floating spacecraft (NDO) design was studied. The free floating spacecraft is reduced to a free-moving center rigid-body flexible beam (FHB) system. The dynamic model of the system is established by using a floating coordinate system. The flexible attachment is discretized by using the modal method to facilitate the calculation. The term related to the unobservable state is regarded as the equivalent perturbation term, and the disturbance observer is designed assuming it to be slow and bounded. Due to the perturbation of attitude and attitude of the flexible attachment, the asymptotic convergence and robustness of the designed disturbance observer are considered. The Lyapunov function is constructed, and the convergence of the observer is proved theoretically. The validity of the disturbance observer is verified by two numerical examples of free and forced motions without external input. The results show that the designed disturbance observer is basically consistent with the true value. The research lays the foundation for the design of the controller with disturbance compensation.