Model-Based Feedforward Control of Large Deformable Mirrors
Model-Based Feedforward Control of Large Deformable Mirrors
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DOI：
10.3166/ejc.17.261-272
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发表时间：
2011
期刊：
影响因子：
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通讯作者：
T. Ruppel;W. Osten;O. Sawodny
中科院分区：
文献类型：
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作者：
T. Ruppel;W. Osten;O. Sawodny
本文提出了一种基于模型的前馈控制方法，用于大变形镜的快速调定点控制。它考虑到本地位置控制回路的激励致动器和模式依赖的刚度变化的镜壳。基于变形镜的时间和空间行为的偏微分方程，进行了镜动力学的模态近似。它示出的本征模动态的二阶近似是适当的低阶模式，即使当额外的系统组件延迟，数模转换器，电流驱动器，致动器磁铁的效率，电容传感器，和模数转换器包括在内。特别是，适当的传递函数与所提出的模态模型的系数确定为45致动器原型的大双目望远镜自适应次镜（P45）。此外，基于模型的前馈控制的实验结果。P45的所识别的动态模型最终用于导出用于斩波的基于平坦度的前馈命令。
In this paper, a model-based feedforward control concept for fast set-point changes of large deformable mirrors is proposed. It takes into account local position control loops of excited actuators and mode-dependent stiffness variations of the mirror shell. Based on partial differential equations for the temporal and spatial behavior of the deformable mirror, a modal approximation of the mirror dynamics is performed. It is shown that a second order approximation of the eigenmode dynamics is appropriate for low-order modes even when additional system components as delays, digital-to-analog converters, current drivers, actuator-magnet efficiencies, capacitive sensors, and analog-to-digital converters are included. In particular, appropriate transfer functions with identified coefficients of the proposed modal models are presented for a 45-actuator prototype of the Large Binocular Telescope adaptive secondary mirror (P45). Additionally, experimental results with model-based feedforward control are presented. The identified dynamic model of the P45 is finally used to derive flatness based feedforward commands for chopping.