Design And Development Of LNG Vehicle Cylinder Liquid Level And Pressure Monitoring System

The21st century is the century of environmental protection, and fuel vehicles will bereplaced with LNG vehicle. we have to meet the demands of changing market and take effectivemeasures to meet the coming era of LNG vehicle. As the key part of LNG vehicle fuel system,LNG vehicle cylinders have also been widespread attention. some research institutions,enterprises, colleges and universities have enhanced efforts about the measurement of LNGvehicle cylinder liquid level and pressure.In this article, through the looking into the environment in the LNG vehicle cylinder, thewriter designed and developed a perfect liquid level and pressure testing system. of LNGvehicle cylinder. The detection of LNG vehicle cylinder liquid level and pressure in this systemis based on capacitive sensor and ceramic piezoresistive pressure sensor. This system designedcircuit of detecting capacitance and the pressure signal, filtering and amplifying. And thissystem used8bits micro-controller chip MCS08SH8offered by Freescale company to detectcapacitance and the pressure signal. MCS08SH8microcontroller has built-in ACMP analogcomparator, AD converter and HCS08series of microprocessors and the chips can simplify theperipheral circuit design, reduces the cost of system development. Due to differentconfiguration of the monitor, this system designed three display drive circuit according to therequirements of different monitor, including driving simulation instrument display circuit,driving light display circuit and driving liquid crystal display (LCD) circuit. So this systemchoose different display solutions according to user requirements.On software design, this article through the researching on the framework of the wholesystem, design the corresponding software system and write the program of capacitancedetection and voltage signal acquisition,. This article also analyze the capacity and pressuresignal and process liquid level and pressure of LNG vehicle cylinder into the digital signalidentified by a microprocessor. According to the requirements of the different drive a differentdriver circuit, this system designed drive program, including simulation instrument driverprogram, PWM output driver program and RS-485communication program. RS-485communication program used the method of questions and answers between master-slave machine to realize the multiple machine communication. This system programming tool use theCodewarrior programming software provided by Freescale company, and the software cancompatible with a variety of programming languages. The program presented in this paper areall made of the C language.This article introduced test of LNG Vehicle Cylinder Liquid Level and PressureMonitoring System. The test results show that the design of LNG vehicle Cylinder liquid leveland pressure monitoring system can obtain the very good application in the actual production oflife. This system can speed up the development of LNG vehicle and effectively relieve thecontradictions of vehicle energy.