次镜调整机构作为空间望远镜主动光学调整的核心组件, 为实现在轨实时快速调整, 其调整精度和动态性能均有比较严格的要求。机构常采用Stewart平台结构形式, 基于逆运动学模型和关节空间PID控制相结合的方法, 由于受到模型的非线性和不确定性、扰动及耦合的影响, 难以取得较为满意的效果。为解决该问题, 从机电动力学模型出发, 将平台各支杆间耦合因素表征为外部干扰, 建立了互相解耦的关节机电模型。依据模型辨识结果采用乘性不确定性描述模型摄动, 依据模型误差界和性能指标要求设计混合灵敏度加权函数。针对虚轴极点问题, 采用扩展H∞方法, 将复杂动力学系统的控制器设计问题转化为堆叠S/T/KS混合灵敏度问题。在Matlab中求解得到鲁棒控制器, 并在DSP中完成数字算法实现。仿真分析及试验结果表明, 鲁棒控制器具有更好的鲁棒性、扰动抑制性能和动态特性, 能够满足空间应用的可靠性需求。

Secondary mirror adjustment mechanisms are core elements of active optics used for the adjustment of space telescopes. For real-time rapid adjustments in orbit, great demands are put on their adjusting accuracy and dynamic characteristics. Because of nonlinearity, uncertainty, disturbances, and coupling of the system, sufficient control cannot be easily achieved by traditional methods based on intermixing PID systems and inverse kinematics. Focusing on this problem, an uncoupled electromechanical model was proposed by transforming the joint couple dynamics into external disturbances. The model uncertainty was represented by the multiplicative uncertainty resulting from the system identification, and the mixed sensitivity function was designed according to the model error bound and performance index. By using the extended method to deal with the imaginary axis pole, the complex dynamic system was transformed into a stacked S/T/KS problem. A robust controller was designed by MATLAB and a digital algorithm was realized using DSP. The improved robustness, disturbance rejection, and dynamic characteristics were verified by both simulations and experimental results, proving that space-reliable application can be achieved.