基于新型双曲正切趋近律的固定/有限时间姿态控制

本文研究了基于一种新型双曲正切趋近律和非奇异固定时间终端滑模面的固定/有限时间姿态控制方法. 对没有外部干扰的航天器姿态控制问题，本文基于双曲正切函数提出了一种新型的固定时间趋近律，该趋近律只需调节控制参数就可保证滑模变量在固定时间内收敛于原点，接着结合非奇异终端滑模面设计了固定时间姿态控制器，保证航天器姿态在固定时间内收敛于原点. 对存在未知外部干扰的情况，设计了双层自适应有限时间滑模观测器估计外部扰动，基于观测器的输出设计了基于非奇异固定时间滑模面与新型双曲趋近律的控制器来对扰动进行补偿. 数值仿真验证了所提控制方法的有效性. 

Fixed/Finite-Time Attitude Control Based on a Novel Hyperbolic Tangent Reaching Law

To deal with the attitude control problem for rigid spacecraft, a method was proposed based on novel hyperbolic tangent reaching law and non-singular fixed time sliding mode surface. Firstly, for the spacecraft attitude control problem without disturbance, a novel fixed-time reaching law was designed based on hyperbolic tangent function, making the sliding mode variables converge to the origin in fixed-time by adjusting parameters only. Then, combined with the non-singular terminal sliding mode surface, a fixed time attitude controller was designed to make the spacecraft attitude converge to the origin in fixed-time for the attitude control problem without disturbance. Next, for attitude control problem in the presence of unknown disturbance, a two-layer adaptive finite-time sliding mode observer was designed to estimate external disturbances. And then, based on the output of the observer, a controller was designed with non-singular terminal sliding mode surface hyperbolic tangent reaching law to compensate the disturbances, and make the attitude converge to the origin in finite time. Finally, some numerical examples were illustrated to demonstrate the effectiveness of the proposed control scheme. Finally, numerical examples are illustrated to demonstrate the effectiveness the proposed control scheme.