基于二分迭代递推的多光谱辐射测温反演算法

Research on Inversion Algorithm of Multispectral Radiation Temperature Measurement Based on Bisection Iterative Recursion

多光谱辐射测温是高温测量的最有力工具之一,它通过光学瞄准系统对准待测点,经分光光路后获得多个光谱通道的辐射信息,利用光电探测器转化为电信号,通过对多个光谱辐射通道的电信号进行数据处理后同时获得待测目标的真实温度和光谱发射率。待测目标的温度反演结果受未知的发射率影响难以直接反演。为解决待测目标发射率模型难以确定的问题,基于参考温度模型,提出一种无需假设发射率模型的多光谱辐射测温数据处理方法。利用同一时刻获得的各个通道反演的温度值与平均值的差值趋近于“零”的约束条件,根据精度要求,设置合理的截止条件,设计合适的发射率迭代步长,可以使反演精度满足实际要求。在提高反演速度方面,提出“二分法”,即在上一次发射率获得温度与平均温度偏差结果引导下,利用“二分法”快速减小发射率搜索区间,直到满足截止条件,即每个光谱通道反演温度趋于相等,从而实现快速反演的目标。基于二分迭代法的多光谱辐射测温反演新算法在未知发射率先验知识的情况下,可实现多光谱辐射测温数据的真实温度反演。基于光纤光谱仪设计了一套多光谱辐射测温实验装置,利用成像透镜将目标聚焦于分化板上的十字叉丝处,叉丝处粘贴有一个45°反射棱镜,将辐射信息反射至光纤后进入光谱仪实现多光谱测温。对一生物质锅炉炉膛火焰通过观察窗进行温度测量并与热电偶测量结果进行比对,结果表明与热电偶测量结果(1000 K左右)相对误差小于4.4%。同时用普通计算机课实现毫秒级实时反演,表明该算法满足在线测量要求,算法进一步完善了多光谱辐射测温理论,为多光谱辐射测温技术在生物质火焰高温测量领域的应用提供了理论支撑。

Multispectral radiation temperature measurement is one of the most powerful tools for high temperature measurement.It aims at the point to be measured through the optical aiming system,obtains the radiation information of multiple spectral channels through the light-splitting path,uses the photodetector to convert it into electrical signals,and obtains the real temperature and spectral emissivity of the target to be measured at the same time after data processing the electrical signals of multiple spectral radiation channels.The temperature inversion result of the target to be measured is affected by the unknown emissivity,which is difficult to be retrieved directly.In order to solve the problem that it is difficult to determine the emissivity model of the target to be measured,based on the reference temperature model,a multispectral radiation temperature measurement data processing method without assuming the emissivity model is proposed.Using the constraint condition that the difference between the retrieved temperature value and the average value of each channel obtained at the same time approaches“zero”,a reasonable cut-off condition is set according to the accuracy requirements,and an appropriate emissivity iteration step size is designed,The inversion accuracy can meet the actual requirements.In terms of improving the inversion speed,the“dichotomy”is proposed.That is,under the guidance of the deviation between the last emissivity temperature and the average temperature,the“dichotomy”is used to quickly reduce the emissivity search interval until the cut-off condition is met,that is,the inversion temperature of each spectral channel tends to be equal,to achieve the goal of fast inversion.The new inversion algorithm of multispectral radiation temperature measurement based on the bisection iterative method can realize the real temperature inversion of multispectral radiation temperature measurement data without prior knowledge of emissivity.Based on the optical fiber spectrometer,a multispectral radiation temperature measurement experimental devices is designed.The target is focused on the cross wire on the differentiation plate by using the imaging lens.A 45°reflection prism is pasted at the cross wire.After reflecting the radiation information to the optical fiber,it enters the spectrometer to realize multispectral temperature measurement.The experiment measured the furnace flame of the boiler through the observation window and compared it with the thermocouple measurement results.The results show that the relative error with the thermocouple measurement results(about 1000 K)is less than 4.4%.At the same time,the millisecond real-time inversion is realized with the ordinary computer course,which shows that the algorithm meets the requirements of on-line measurement,and the algorithm further improves the theory of multispectral radiation temperature measurement.It provides theoretical support for the application of multispectral radiation temperature measurement technology in the field of biomass flame high-temperature measurement.