刚体航天器预设时间预设精度姿态跟踪控制

Predefined-time predefined-bounded control for attitude tracking of rigid spacecraft

摘要:

为研究刚体航天器在上界已知的外部扰动力矩作用下的姿态跟踪控制问题,提出了一种可以指定跟踪精度的预设时间姿态跟踪控制策略。首先,设计了一种预设时间扰动观测器,此观测器可以在指定的时间以内实现对有界外部扰动的高精度在线估计,利用其估计值可以对外部扰动力矩进行补偿。然后,在此扰动观测器的基础上,运用终端滑模控制方法,设计了一个（准）终端滑模面并构造了一个连续非奇异终端滑模姿态跟踪控制器。Lyapunov理论分析表明,本研究所提观测器、滑模面和控制器的收敛时间上界以及收敛完成以后姿态跟踪的误差上界均显式存在于观测器、滑模面和控制器的有关参数中,因而可以在控制器设计过程中很方便地对其进行调节,且不受初始条件的制约。最后,通过数值仿真验证了所提控制策略的性能。仿真结果表明,无论是收敛速度还是跟踪精度,预设值都是一个比较宽松的上界,实际性能有可能远远优于预设值,并且此算法对系统的建模不确定性也有比较好的鲁棒性。

Abstract:

To investigate the attitude tracking control problem of rigid spacecraft under the action of external disturbances torque with known upper bound, this paper proposes a predefined-time attitude tracking control scheme, in which the tracking accuracy can be specified in advance. Firstly, a predefined-time disturbance observer which can realize high-precision online estimation for the bounded external disturbances within the specified time is designed to compensate the external disturbances using its estimated information. Then based on this observer, a quasi-terminal sliding mode and a continuous nonsingular controller is designed using terminal sliding mode control method. Lyapunov theoretical analysis results show that the upper bounds of observers, sliding modes and the controllers convergence time and the accuracy of attitude tracking all explicitly exist in the relevant parameters, so they can be easily adjusted during the design of the controller without being restricted by the initial conditions. Finally, the performance of proposed control scheme is evaluated by using numerical simulation. Simulation results show that the predefined values are loose upper boundaries, for either convergence speed or tracking accuracy, the actual performance may be far better than predefined values. Furthermore, this algorithm is also quite robust to the uncertainty of system modeling.