Propagation properties of high-power fiber laser with high-order-mode(HOM) content are studied numerically for the first time to the best of our knowledge. The effect of HOM on the propagation property is evaluated by...Propagation properties of high-power fiber laser with high-order-mode(HOM) content are studied numerically for the first time to the best of our knowledge. The effect of HOM on the propagation property is evaluated by the power in the bucket(PIB) metric. It is shown that PIB is mainly dependent on HOM content rather than the relative phase between the fundamental mode and HOM. The PIB in vacuum is more than 80% when the power fraction of the HOM is controlled to be less than 50% at 5 km. The relative phase has an impact on the peak intensity position and concentration of the far-field intensity distribution. If an adaptive optics system is used to correct the peak intensity deviation, the results indicate that there exists a maximal value of PIB as relative phase increases. Such effect is weakened when propagating in turbulence. Compared to the laser beams without HOM, laser beams with HOM content are less influenced by the turbulence and can reduce average intensity fluctuation. The results may be useful in the design of a high-power fiber laser system.展开更多
针对永磁同步电机在传统无传感器滑模控制系统中存在的抖振、相位延迟和鲁棒性差等问题,设计了一种双自适应二阶广义积分器和归一化锁相环(dual adaptive second order generalized integrator and quadrature phase locked loop,DASOGI...针对永磁同步电机在传统无传感器滑模控制系统中存在的抖振、相位延迟和鲁棒性差等问题,设计了一种双自适应二阶广义积分器和归一化锁相环(dual adaptive second order generalized integrator and quadrature phase locked loop,DASOGI-QPLL)的改进高阶滑模观测器的控制方法。首先,双广义二阶积分器的锁相环结构,作为一种闭环PLL方案能够在电网电压不平衡、产生畸变、频率跳动等场合准确获取正、负分量的相位、频率和幅度值信息,将其利用在滑模控制当中,能有效滤除其滑模面产生的高频脉振,并能有效抑制电机波动时的电流(电压)波形畸变;其次,对传统高阶滑模观测器引入基于转子转速的自适应高阶滑模增益;最后,采用归一化正交锁相环对电机的转速和转子位置进行估计。仿真结果表明,所设计的DASOGI-QPLL能很好地解决这一问题,在对滑模面高频脉振进行滤波的同时能够快速准确跟踪到电流(电压)波形的幅值和相位,提高了电机的控制精度和运行的动态性能。展开更多
基金sponsored by the Innovation Foundation for Excellent Graduates in the National University of Defense Technology under grant no. B120704the Open Research Fund of Key Laboratory of Atmospheric Composition and Optical Radiation under grant no.2012JJ05
文摘Propagation properties of high-power fiber laser with high-order-mode(HOM) content are studied numerically for the first time to the best of our knowledge. The effect of HOM on the propagation property is evaluated by the power in the bucket(PIB) metric. It is shown that PIB is mainly dependent on HOM content rather than the relative phase between the fundamental mode and HOM. The PIB in vacuum is more than 80% when the power fraction of the HOM is controlled to be less than 50% at 5 km. The relative phase has an impact on the peak intensity position and concentration of the far-field intensity distribution. If an adaptive optics system is used to correct the peak intensity deviation, the results indicate that there exists a maximal value of PIB as relative phase increases. Such effect is weakened when propagating in turbulence. Compared to the laser beams without HOM, laser beams with HOM content are less influenced by the turbulence and can reduce average intensity fluctuation. The results may be useful in the design of a high-power fiber laser system.
文摘针对永磁同步电机在传统无传感器滑模控制系统中存在的抖振、相位延迟和鲁棒性差等问题,设计了一种双自适应二阶广义积分器和归一化锁相环(dual adaptive second order generalized integrator and quadrature phase locked loop,DASOGI-QPLL)的改进高阶滑模观测器的控制方法。首先,双广义二阶积分器的锁相环结构,作为一种闭环PLL方案能够在电网电压不平衡、产生畸变、频率跳动等场合准确获取正、负分量的相位、频率和幅度值信息,将其利用在滑模控制当中,能有效滤除其滑模面产生的高频脉振,并能有效抑制电机波动时的电流(电压)波形畸变;其次,对传统高阶滑模观测器引入基于转子转速的自适应高阶滑模增益;最后,采用归一化正交锁相环对电机的转速和转子位置进行估计。仿真结果表明,所设计的DASOGI-QPLL能很好地解决这一问题,在对滑模面高频脉振进行滤波的同时能够快速准确跟踪到电流(电压)波形的幅值和相位,提高了电机的控制精度和运行的动态性能。
