中南大学自动化学院，湖南 长沙 410083
School of automation， central south university 410038， China
Supported by the National Natural Science Foundation of China （61873282）
玻璃药瓶中的氧气残留对瓶中药品的无菌特性造成了严重的威胁。采用波长调制光谱（Wavelength modulated spectrum， WMS）技术解调得到的二次谐波信号峰高值作为氧浓度反演的基础。然而，在用二次谐波信号测量气体浓度时，由于调制深度的变化会导致二次谐波峰值的变化，这通常会给系统带来误差，进而降低浓度的反演精度。而调制深度受调制电流波动、温度和压强变化等因素的影响不能直接计算获得进而修正。针对这一问题，本文成功的将调制深度与二次谐波峰高的关系转换为二次谐波峰宽和峰高的关系。然后，利用峰宽校正后的谐波峰高对气体浓度进行反演。初步实验表明，利用峰宽校正后的谐波峰高对瓶内气体浓度进行预测的准确性提高了2.1%，且系统的整体鲁棒性也得以提升。本文提出的校正方法不需要系统参数信息与气体成分信息，可以直接从谐波信号本身出发对调制深度进行校正，十分适合于工业现场的在线氧气浓度预测。
The oxygen residue in the glass medicine vial poses a serious threat to the sterility of the medicine in the vial. In this paper， the peak height of the second harmonic signal demodulated by wavelength modulated spectrum （WMS） technology is used as the basis of oxygen concentration inversion. However， when measuring gas concentration with second harmonic signal， the change of modulation depth will lead to the change of second harmonic peak， which will usually bring errors to the system and reduce the inversion accuracy of concentration. However， the modulation depth is affected by the fluctuation of modulation current， temperature and pressure， and cannot be calculated directly. To solve this problem， we first successfully convert the relationship between modulation depth and secondary harmonic peak height into the relationship between secondary harmonic peak width and peak height. Then， the gas concentration is inversed by using the harmonic peak height after being corrected by peak width. Preliminary experiments show that when using the harmonic peak height after peak width correction to predict the gas concentration in the vial， not only the accuracy of the system is improved by 2.1%， but also the overall robustness of the system is improved.