一种轮控卫星姿态机动变结构控制器

针对小卫星3轴反作用轮姿态控制系统的非线性特性，应用误差四元数来描述姿态运动，将星体大角度姿态机动问题转化为误差四元数的调节问题．利用误差四元数和误差角速度建立滑动模态，并基于Lyapunov定理推导出一种姿态机动的引入角加速度负反馈的变结构控制律．仿真结果表明，该控制律能够提高收敛速度，降低机动过程中角速度的超调量和对起始力矩的要求．同时，在模型参数不确定和有外干扰的情况下该控制律也具有全局稳定性和鲁棒性．

A Variable-Structure Controller of Small Satellite Attitude Maneuver With Reaction Wheels

Generally speaking, the Euler angle is usually used to describe the attitude of small satellites. In this case, however, singularity exists during large angle maneuver of small satellites. In contrast, such singularity can be avoided when the attitude is described by the quaternion. In this article, with regard to nonlinear properties of small satellite attitude contol systems actuated by reaction wheels, the attitude kinematics is described by the error-quaternion so that the large angle maneuver of the satellite can be converted into the problem of regulation of the error-quaternion. Sliding surfaces were designed on the basis of error-quaternion and an equivalent variable-structure controller introducing angular velocity acceleration feedback term was derived based on Lyapunov theorem. Simulation results show that the the proposed SMC law can improve the convergence rate, reduce the overshoot value of angular volecity during the maneuver and the demand of initial control torquer. In the meanwhile global stability and robustness of the method considering parameter uncerties and external disturbances such as sunlight pressure moment, the surplus magnetism moment of satellite and the pneumatic moment can also be guaranteed.