针对卫星控制系统执行器故障,考虑干扰与不确定性影响,设计了一种自适应模糊滑模容错控制器(AFSMC)。首先,将执行器故障、干扰以及模型不确定性统一描述为系统的广义总干扰;然后,为使系统能够在有限时间内快速稳定且避免奇异,设计了非奇异快速终端滑模控制器(NFTSMC);其次,针对滑模系统固有的抖振现象,设计了自适应算法对系统广义总干扰进行补偿,减小了切换增益,并以自适应模糊系统逼近切换函数,柔化了输入信号,从而有效削弱了系统抖振,大大提高了控制精度;最后,对所提方法进行了数值仿真验证。
An adaptive fuzzy sliding mode controller( AFSMC) is designed for the satellite regarding the actuator faults,disturbance and model uncertainty during the attitude tracking process. Firstly,the tracking error dynamic and kinematic models are built based on quaternion error,where the actuator faults,disturbance and model uncertainty are combined with a general interference. Then,a nonsingular and fast terminal sliding mode controller( NFTSMC) is derived as the main controller to guarantee the system stability in limited time for avoiding the singularity. By considering the chattering inherent in sliding mode structure,an adaptive law is introduced to compensate the general interference which efficiently weakens the chattering by reducing the switch gain. In order to further improve the precision of the system,an adaptive fuzzy system is used to approximate the symbolic function in the sliding mode control. Finally,numerical simulations on the attitude tracking control of spacecraft in the presence of environmental disturbance and parameters uncertainties are performed,whose results show the system using AFSMC can stabilize within 13-and the precision of attitude angle and angular velocity can be 0. 001°and 0. 0008( °)/s,respectively. In addition,this method can meet the requirements of fault-tolerance with faster convergence speed and better robustness by comparing with the conventional NFTSMC.