快速光滑终端滑模在空天飞机姿态角控制器中的应用研究

Application of Attitude Controller Based on Fast Smooth Terminal Sliding Mode in Aerospace Plane

针对空天飞机再入飞行阶段存在模型参数不确定和外部扰动情况下的姿态跟踪控制问题,分析、建立了考虑地球自转的空天飞机六自由度动力学模型;以此为基础,利用非线性三阶扩张状态观测器可实时在线估计姿态角速度和系统扰动的显著优点,导出了适用于控制系统设计的数学模型;利用该模型,设计了一种基于非线性三阶扩张状态观测器的快速光滑终端滑模控制算法。然后,基于李雅普诺夫理论,严格证明了系统的稳定性。控制算法利用快速光滑终端滑模控制无需惯常终端滑模控制所需的控制量系数矩阵的求逆计算,提高了控制算法的计算实时性;同时,采用光滑滑模趋近律能够在有限时间内收敛到滑模面且有效地消除抖振,对系统的参数摄动及扰动具有很强的自适应性。仿真结果表明,相比基于非线性三阶扩张状态观测器的传统非线性反馈控制算法,文中所提出的控制算法调整时间短,超调量小,并且具有良好的跟踪精度,具有一定的工程应用价值。

The aerospace plane can greatly enhance the capacity of manned space transportation and space support capacity. The uncertainty of model parameters and the attitude control problems under external disturbance during reentry of aerospace plane were discussed in this paper. A six-degree-of-freedom dynamics model of LEO aerospace plane with symmetric outline was analyzed and established with the consideration of the effects of earth rotation. On this basis,a mathematical model suitable for the control system design was derived taking advantage of the real-time estimation of angular velocity of attitude angle and system disturbance by nonlinear third-order extended state observer. Then based on the nonlinear third-order extended state observer,a smooth fast terminal sliding model control algorithm was designed with the above mathematical model. The stability of system was strictly proved according to Lyapunov theory. By using of smooth fast terminal sliding model control algorithm,the real-time calculation of the control algorithm was improved,because the inverse calculation of the control quantity coefficient matrix that the sliding model control usually required was no longer needed. Adopting the smooth sliding model reaching law,the convergence to the sliding model surface could be realized within the limited time and the buffeting could be eliminated efficiently. It had high adaptability against the system parameter perturbation and disturbance. The simulation results showed that,as compared with the traditional nonlinear feedback control algorithm based on nonlinear thirdorder extended state observer,the design with the proposed control algorithm had shorter adjustment time,faster response,smaller overshoot,better tracking precision. It was promising for practical engineering application.