| The paper focuses on how to evaluate the tank vehicle’s safety state for hazardous chemicals transportation. A distributed and multi-sensor monitoring system is designed and a gas sensor calibration system is established, an analytical model for the tank vehicle’s safety status is proposed, and muiti-sensor information algrithems are studied to evaluate the safety status.First of all, a data acquisition network system is designed to collect the running status of the vehicle and the safety parameters of the hazardous chemicals. The network system includes a data acquisition terminal and a remote central control unit. The signals from eight kinds of sensors distributed in different positions are collected in the data acquisition terminal. These sensors can be divided into four sections. The first section is an acceleration sensor and an angle sensor for detecting the tank vehicles’running status. The second section is a gas sensor, a pressure sensor and a liquid level sensor for monitorting the safety status of the hazardous chemiclas in the tank. The third section is a temperature sensor and a humidity sensor for obtaining the ambient environment. The last section is a door switch sensor for an illegal operation. Remote central control unit is used to wirelessly receive data from the data acquisition terminals and evaluat the safety status of the vehicles comprehensively. If a danger occurred, the managers can receive a forecasting or an alarm message. According to the characteristics of the sensors, suitable pre-processing methods are approved for different sensors. And the correlation coefficient between different sensors and a safety status was gained by signals correlations. Furthmore, a new method based on the multi-sensor signal correlation was put forward to detect the vehicle’s safety status.Secondly, the gas sensor is the core element to assess the state of the leakage. In order to guarantee the accuracy of the gas sensor, a gas sensor calibration system is designed and established. This system can configure gas concentration in a closed loop automaticly and continuously with a high precision. And this system can calibrate fourty gas sensors one time. This system consists of a quadrupole mass spectrometer, multiple mass flow controllers, a tempreture and humidity regulator unit and a computer. It can regulate the tempreture range from0to100℃, and the humidity from0to100%RH. Meanwhile, it can control the outputs of the mass flow controllers by dealing with the data from the quadrupole mass spectrometer by the least squares. In order to validate the accuracy of the system,132samples of12kinds of hazardous chemicals gas with different concentrations are sampled. And all these samples were tested by the Agilent6890gas chromatograph.The minimum relative error of the system is0.01%, the maximum relative error was10.61%. According to the results, the relationship between the system accuracy and the ambient environmental temperature humidity conditions is studied.Thirdly, from the respective of set theory, several evaluation algorithms are studied. A threshold method, a ratio threshold method and a revised C4.5decision tree algorithm are studied.The threshold method is simple with higher false rate. While, the ratio threshold method due to the increment trend judgment decreased the false rate rapidly.And the lowest false rate appeared on the revised C4.5decision tree algorithm with a high ability to deal with missing data and noise data. In order to eliminate the false rate, a novel distributed multi-sensor analysis model is put forward based on the system theory, and a fuzzy comprehensive evaluation algorithm and an extension engineering algorithm are studied. The fuzzy evaluation algorithm consists of a error function and a fuzzy evaluation function. The error function expresses the relation between a sensor and other sensors, and the fuzzy evaluation function displays the relation between a sensor and a safety status. A data set containing leakeage status and normal status is analyzed. Compared with the threshold method, the risk judgment accuracy rate of this algorithm is100%. Owing to the signals limited in strict boundary conditions, the fuzzy comprehensive algorithm only can predict two safety statuses. Extension engineering function algorithm is studied. It consists of an analytic hierarchy process and an extension function. The same data set used in the fuzzy function algorithm is analyzed, risk judgment accuracy rate is also100%. Meanwhile, a tendency of the safety status is given precisely in real time.Finally, in order to validate the robustness and reliability of the algorithms, a small-scale tin box experiment system is carried out. And a large number of vehicle experimental researches are simulated and tested. Meanwhile, these algorithms are adopted in an exercises launched by the863project team.Research results show that the algorithms can be used to evaluate the safety status in hazardous chemicals transportation by tank vehicles. |
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