Application of Kalman Filter in Gas Detection by Cavity Ring-Down Spectroscopy
LI De-hao1, WANG Dan1*, LI Zhi-yan1, CHEN Hao2
1.School of Microelectronics and Data Science, Anhui University of Technology, Ma'anshan 243000, China
2. School of Mechanical Engineering, Suzhou University of Science and Technology, Suzhou 215000, China
Abstract:Cavity Ring-Down Spectroscopy (CRDS) is a highly sensitive trace gas concentration measurement technique in which the processing of ring-down time is crucial. This paper adopts the Kalman filter to process the cavity ring-down spectroscopy to reduce the measurement error introduced by noise during the collection and real-time measurement process. This method preprocesses with the traditional filtering method to obtain the observation noise covariance σ2v(R) of the Kalman filter parameters, adjusts the process excitation noise covariance σ2w(Q), and evaluates the filtering effect to optimize the measurement results. Using simulated ring-down signals with white noise, the linear regression summation method (LRS) fits the background rendering-downtimesto perform Kalman filtering. From four aspects of mean, standard deviation, residual standard deviation (RMSE), and different noise levels, the appropriate Q value range is obtained, which is less than 1×10-7 and 0.001, respectively. An experimental gas detection system based on CRDS technology is constructed, using a 405 nm center wavelength diode laser and a high-reflectivity mirror with a reflectivity of over 99.99%, with NO2 as the target gas, and the background ring-down time and ring-down time are processed and analyzed using Kalman filtering. The experimental results show that: (1) Selecting a Q value less than 1×10-7 for Kalman filtering of the background ring-down time increases the lowest detection limit by 9.12 times and reaches 4.9×10-11 after filtering; (2) Taking Q value of 0.001 for processing the ring-down time retains the time response information and achieves significant noise reduction; (3) The system's time resolution is 1 s, and compared to the method of reducing time resolution to improve detection limit in the past, the Kalman filtering method improves the system's sensitivity. The agreement between experimental and simulated results verifies the effectiveness of Kalman filtering in stability and noise reduction. Applying the Kalman filtering method in the CRDS spectroscopic detection of gases is practical and provides methods and references for optimizing other gas measurement results.
李德浩,王 丹,李治艳,陈 浩. 卡尔曼滤波方法在腔衰荡光谱技术探测气体中的应用[J]. 光谱学与光谱分析, 2024, 44(10): 2727-2732.
LI De-hao, WANG Dan, LI Zhi-yan, CHEN Hao. Application of Kalman Filter in Gas Detection by Cavity Ring-Down Spectroscopy. SPECTROSCOPY AND SPECTRAL ANALYSIS, 2024, 44(10): 2727-2732.
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