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为了验证设计的反步滑模控制方法对机载激光通信系统的控制效果,采用提出的方法与参考文献[16]的分数阶PID控制方法进行对比实验。整个仿真过程持续10 s,机载激光通信系统的初始状态均为0。设置仿真环境参数如下:
通信对象的坐标指令:
复合扰动:
控制律参数如表1所示。
Parameters Value Parameters Value k1 diag{3,5,6} k2 diag{2,1,3} k3 diag{4,3,5} k4 diag{5,7,2} k5 diag{8,6,3} k6 diag{2,5,7} k7 diag{9,2,5} k8 diag{4,2,7} k9 diag{4,2,6} -- -- Table 1. Control law parameters
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由于激光通信质量取决于视轴能否对准通信对象方位坐标,实验将机载激光通信系统视轴与通信坐标对象的对准情况进行仿真,得到的空间对准结果如图3所示。
由空间对准仿真结果可看出:在参考文献[16]控制方法的作用下,机载激光通信系统能够在1 s后大致跟踪通信对象的坐标变化趋势,但是会在指令pc附近剧烈振荡,最大振荡误差为5 m;而在文中反步滑模控制方法的作用下,机载激光通信系统能够在0.4 s内准确跟踪通信对象的坐标指令pc,最大误差仅为0.3 m。
为了进一步突出文中方法的优越性,给出x、y和z坐标对准结果如图4~6所示。
由仿真结果图4~图6中的x、y、z坐标对准可看出:在参考文献[16]控制方法的作用下,机载激光通信系统能够在1 s后大致跟踪通信对象的坐标变化趋势,但会在指令附近剧烈振荡,最大振荡误差分别为4 m、4 m和4.5 m;而在文中反步滑模控制方法的作用下,机载激光通信系统能够在0.4 s内准确跟踪通信对象的坐标指令,最大误差仅为0.3 m。
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为了进一步验证文中所设计的滑模观测器的有效性,给出扰动估计结果如图7~9所示。
由仿真图可看出:设计的滑模观测器能够在0.3 s内准确估计扰动值,最大估计误差分别仅为0.1 m/s、0.06 (°)/s2和0.07 A/s,估计速度和估计精度均较高。
Precision control of airborne laser communication optical axis using sliding mode observer
doi: 10.3788/IRLA20210460
- Received Date: 2021-12-07
- Rev Recd Date: 2022-01-20
- Publish Date: 2022-04-07
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Key words:
- airborne laser communication system /
- optical axis alignment /
- disturbance /
- sliding mode observer /
- back-stepping sliding mode control
Abstract: To improve the optical axis alignment accuracy of airborne laser communication system under the disturbance of body vibration and mechanical friction, a back-stepping sliding mode control method based on sliding mode observer was proposed. Firstly, the mathematical model of the airborne laser communication system was established, and then the disturbance value was estimated by the designed sliding mode observer. At the same time, the back-stepping sliding mode control law was gradually designed for the command conversion module, laser communication module and motor module, which realized the high-precision control for the optical axis of the airborne laser communication system. The experimental results show that the proposed method has better rapidity and accuracy than the fractional PID control method, the response time is only 0.4 s, the maximum space alignment error is only 0.3 m, the designed sliding mode observer can estimate the disturbance value quickly and accurately, the response time is only 0.3 s, and the maximum estimation error is only 0.1 m/s, 0.06 (°)/s2 and 0.07 A/s, which greatly improves the alignment accuracy of the optical axis in the airborne laser communication system.