• Chinese Journal of Lasers
  • Vol. 48, Issue 24, 2401003 (2021)
Wenhui Cui1、2、*, Jianqiang Zhu1、**, Yuanqi He1、2, Zhigang Liu1, Quantang Fan1, Weiheng Lin1、2, and Ziming Dong1
Author Affiliations
  • 1Joint Laboratory on High Power Laser and Physics, Shanghai Institute of Optics and Fine Mechanics, Chinese Academy of Sciences, Shanghai 201800, China
  • 2University of Chinese Academy of Sciences, Beijing 100049, China
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    DOI: 10.3788/CJL202148.2401003 Cite this Article Set citation alerts
    Wenhui Cui, Jianqiang Zhu, Yuanqi He, Zhigang Liu, Quantang Fan, Weiheng Lin, Ziming Dong. Target Deviation of SG Facility Based on Active Vibration Absorption Control[J]. Chinese Journal of Lasers, 2021, 48(24): 2401003 Copy Citation Text show less

    Abstract

    Objective The high power laser facility for inertial confinement fusion (ICF) is a large scientific project with ultraprecision, long optical path, and many precision components. Any optical interference caused by environmental vibration, acoustic vibration, or thermal gradient reduces the aiming accuracy and success rate. The confocal lens pair in the spatial filter is the most important component of SG-Ⅱ series devices. Considering the phenomenon where the beam propagation of the confocal lens pair of the long optical path spatial filter deviates from the ideal optical axis and causes poor pointing stability, the existing solutions involve processing the optical elements with higher accuracy or using the beam stabilization technology. Neither of the two solutions starts from the root, and the vibration response of the optomechanical structure affects the beam-pointing stability. The beam-pointing stability has been analyzed by assuming that the structure’s vibration is known but the structure’s transmission characteristics under excitation have not been analyzed. Further, active damping dynamic vibration absorption can be used to analyze the pointing stability of the ICF facility, but the theoretical analysis has not been reported. Therefore, studying the beam-pointing convergence accuracy from the perspective of optical mechanical structure vibration control is necessary.

    Methods The full link beam propagation model of SG-Ⅱ series facilities was established, and an optomechanical coupling system of spatial filter based on active damping dynamic vibration absorption principle was provided. The peak value formula of the spatial filter’s output optical angular response was derived, and an adaptive fuzzy proportional-integral-derivative (PID) active controller was designed to realize control parameter self-tuning. The influence of active control parameters on the peak value of output optical angular response was analyzed. The control efficiency was defined, and the control parameters were optimized. The adaptive fuzzy PID control algorithm realized the adaptive tuning of the damping. The active damping dynamic vibration absorption control was conducted for the shooting deviation of SG-Ⅱ series facilities. The calculation formula of the shooting deviation of the spatial filter was derived. It analyzed the control effect of space filter shooting deviation of SG-Ⅱ series facilities before and after active damping dynamic vibration absorption by adaptive fuzzy PID control.

    Results and Discussions The peak value of output optical angular response degenerates from two formants to one formant with the change of excitation frequency, and velocity feedback gains control parameter gP. With increasing control parameters, the maximum value of output optical angular response first decreases and then increases, indicating that there is an optimal velocity feedback gain to minimize the peak value of output optical angular response. The response amplitude of the entire frequency domain is controlled below the optimal parameter’s peak value [Fig. 8(a)]. When gP is 80, the parameters are optimal, and the control efficiency is the highest, reaching 75.9% [Fig. 9(a)]. When the excitation frequency and the displacement feedback gain control parameter gI change, the peak value of the output optical angle response is positively correlated in 18--20 Hz and above 28 Hz and negatively correlated below 18 Hz and in 20--28 Hz. The overall tuning control amplitude is small, and the narrow-band excitation frequency band even increases the peak value of the output optical angle response, making it unsuitable for peak value control of the output optical in the full frequency domain [Figs. 8(b) and 9(b)]. The maximum target deviation of the spatial filter of the SG-Ⅱ facility appears in the sixth stage, and the output deviation after optimal control of active damping dynamic vibration absorption is 1.23 μm (Table 4 and Fig. 11). The maximum target deviation of the spatial filter of the SG-Ⅱ high-energy laser system appears in the seventh level, and the output deviation after the optimal control of active damping dynamic vibration absorption is 4.52 μm (Table 5 and Fig. 12). Compared with the later spatial filters, the 0-, 1-, and 2-stage spatial filters can achieve the function of shooting deviation without dynamic vibration absorber, and the 3-stage spatial filter only requires a passive damping dynamic vibration absorber. The maximum target deviation of the SG-Ⅱ spatial filter upgrading facility appears in the fifth to eighth level. After optimal control of active damping dynamic vibration absorption, the output deviation is 3.29 μm (Table 6 and Fig. 13). After controlling the active damping absorber, the shooting accuracy of the SG-Ⅱ facility is reduced from 5.42 μm to 1.30 μm, the shooting accuracy of the SG-Ⅱ high energy laser system is reduced from 7.67 μm to 1.87 μm, and the shooting accuracy of SG-Ⅱ upgrading facility is reduced from 6.52 μm to 1.57 μm. After designing the passive damping absorber, the active damping absorber can tune the damping to the optimal value according to the specific working conditions. Therefore, the effect of dynamic vibration absorbers is better than that of passive damping (Table 7).

    Conclusions When the active damping dynamic vibration absorber is tuned to optimal damping, the shooting deviation is reduced by 75.9% compared with the traditional method. At the same time, the passive damping dynamic vibration absorber reduces shooting deviation by about 31% compared with the traditional method. Additionally, the active damping dynamic vibration absorber can adjust the velocity feedback gain based on the shooting deviation. Consequently, the control efficiency varies from 31.0% to 75.9%, which realizes the feedback function of adaptive adjustment. Therefore, this method has a good application prospect for improving the shooting performance of laser facilities in service.

    Wenhui Cui, Jianqiang Zhu, Yuanqi He, Zhigang Liu, Quantang Fan, Weiheng Lin, Ziming Dong. Target Deviation of SG Facility Based on Active Vibration Absorption Control[J]. Chinese Journal of Lasers, 2021, 48(24): 2401003
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