面向农产品冷链物流监测的无线气体传感器在线校准方法

Wireless Gas Sensor On-line Calibration Method for Cold Chain Logistics Monitoring of Agricultural Products

鲜活农产品冷链保鲜、保活运输过程中需要精确监测和控制运输微环境气体浓度,因此实时精准地监测运输环境中各类气体成分浓度尤为重要。在长期气体浓度监测中,传感器会发生漂移并呈现弱稳定性现象,从而造成监测精准度降低,导致保鲜、保活控制低效。针对该问题,设计基于无线传感器网络的气体传感器在线校准方法,利用融合技术对运输环境中分布式部署的无线气体传感器进行周期性选举,筛选测量准确、稳定的领袖传感器节点组作为参考,动态计算终端传感器漂移特征参数变化,并使用无线通讯技术完成各类气体感知节点输出-浓度映射函数参数的修正调节,以重新计算输出信号与气体浓度的动态映射关系。该方法可非更换地实现在线气体传感器动态校准,从整体上修正了运输微环境中气体传感器输出-浓度映射参数以提高数据获取精度。以鲟鱼低温无水休眠保活运输为试验流程,对重要环境气体CO2、O2、NH3等浓度信息进行了监测与校准试验。利用高精度、已校准的气体浓度记录仪作为运输微环境气体浓度测量标准,进行校准试验评估。试验表明传感输出信号为TTL电平的CO2传感器可提高测量精度3.28%,其精度提高程度低于线性或非线性函数输出的气体传感器;对于输出-浓度映射为非线性信号的NH3气体监测精度可提高4.14%;针对传感输出为线性函数关系的O2传感器校准效果最优,其监测精度可提高4.71%。综合对比运输气体变化监测数据,验证了在不更换传感器进行离线气调校准的情况下,所提方法可较显著地提高气体浓度监测精度,为有效精准调节冷链运输微环境气体浓度提供了调控依据。

Fresh agricultural products and keeping live transportation in the process of cold chain requires accurate monitoring and controlling of transport micro-environmental gas concentration,thus real-time accurate monitoring and controlling all kinds of micro-environmental gas concentration is particularly important. In the long-term monitoring of gas concentration, the sensor will drift and show the phenomenon of weak stability, resulting in reduction of monitoring accuracy and low efficiency of controlling for preservation. Aiming at this problem,the design was based on wireless sensor network gas sensor for on-line calibration method,fusion techniques were used to do periodic election of logistics monitoring with distributed deployment of wireless gas sensor,measurement accuracy and stability of theleader of sensor node group were selected as a reference,dynamically calculated the change of terminal sensor drift characteristic parameters,and wireless communication technology was used to complete correction of various types of gas sensing output mapping parameters in order to calculate dynamic mapping between output signal and gas concentration. The method can realize dynamic calibration of online gas concentration sensing without replacing gas sensor,and output of gas sensor in the transportation was optimized as a whole to improve the accuracy of acquisition. The method was verified by lowtemperature sturgeon water-free dormant keep-live transportation tests,monitoring and calibration of concentration information for the important environmental gas CO2,O2,NH3 and so on. The evaluation test was carried out by using high precision and calibrated gas concentration data recorder as standard for measurement of gas concentration for the micro environment of transportation. Experiments show that the sensor output signal for TTL level of CO2 sensor can improve the measurement accuracy by 3. 28%. The precision was inferior to linear or nonlinear output functions of gas sensor; for concentration output mapping of nonlinear signal, the NH3 gas monitoring accuracy can be improved by 4. 14%. The calibration method for sensor output concentration mapping for linear function of oxygen gas sensors ＇calibration was the best and the monitoring precision can be improved by 4. 71%. Comprehensively comparing the monitoring data of gas concentration change,this method can significantly improve the accuracy of gas monitoring,which provided basis for precise monitoring and controlling of cold chain transportation micro environment gas concentration.