带有输入死区的航天器姿态有限时间控制

死区非线性是航天器姿态控制系统中一种普遍存在的执行机构非线性,它的存在会降低姿态控制系统的性能,甚至可能破坏系统的稳定性.为了解决带有输入死区非线性的航天器的高精度姿态控制问题,给出了一种有限时间控制方法,并且考虑航天器姿态控制模型中含有有界的不确定性且输入死区非线性仅部分信息已知.通过引入一个在指定时间内收敛到零的期望姿态变化曲线,并基于时变滑模控制理论设计鲁棒控制算法使得实际姿态和期望姿态之间的偏差始终保持足够小,从而保证实际姿态在指定的时间内收敛到原点附近.严格的理论分析表明,所设计控制律不仅可以保证闭环系统的信号有界而且可以使得实际姿态在指定的时间内收敛到并以指定的精度保持在原点附近.数值仿真结果表明,所提控制方法是有效的,该方法不仅能够保证系统状态具有很快的收敛速度、很高的控制精度,而且对于系统的不确定性具有很强的鲁棒性和抗干扰能力,因而在航天器的姿态控制中具有良好的潜在应用价值.

Finite-time attitude control of spacecrafts with input dead-zone nonlinearities

Dead-zone nonlinearities are a kind of common nonlinear characteristics of the actuator nonlinearities of spacecraft attitude control systems. They could degrade the performance, and even lead to un-stability of spacecraft attitude control systems. To solve the high precision attitude control problem for spacecraft with input dead-zone nonlinearities, this paper proposes a kind of finite time control approach. The attitude control model of the spacecraft considered in this paper is with bounded uncertainties and the information of the input dead-zone nonlinearities is only partially known. A desired attitude curve which converges to zero in the given time is introduced. A robust finite-time control algorithm is proposed based on the time-varying sliding mode approach to ensure the error between the actual attitude and the desired one keep small enough all the time. This further ensures that the actual attitude converges to the nearby of zero in the given time. By rigorous analysis, it is proved in theory that all of the signals in the closed-loop system are bounded and the attitude error can be driven into a small given neighborhood of the origin in the pre-specified time and stay there thereafter. The numerical simulation results show that the proposed control method is effective. It could guarantee that the system possesses fast state convergence speed, high control precision, and good robustness with respect to uncertainties and disturbances, so it has good potential application value in the attitude control of spacecraft.