The Development And Applied Research Of Electronic Controlling System For CNG Single Fuel Engine

Energy crisis and environmental protection are two major issues people facing in the21st century. Vehicles fuelled with natural gas are energy-saving, and have a loweremissions and a higher efficiency so that they are widely used. With the boomingdevelopment of electronic control technology and promoting the use of natural gasvehicles, demands for control functions of compressed natural gas (CNG) enginecontrol system are higher. Therefore, the research on high-performance electroniccontrol system of CNG engines has become a hotspot.This paper develops a presentence sub-cylinder control strategy depending on theadvantages and disadvantages of common sub-cylinder strategies. It is faster and morereliable. The control requirements of multi-point sequential injection and individualignition of each cylinder are achieved on CNG engines.On the basis of the analysis of LSU4.2wide-range oxygen sensor, closed-loop controlof the air-fuel ratio was achieved by the method of combining incremental PID andfuzzy PID. Self-learning function was developed based on LSU4.2wide-range oxygensensor. By combining self-learning function with the closed-loop control, air-fuel ratiocan be controlled precisely in CNG engine. Self-learning function can also assist ECUin adjusting the jet MAP icon. Calibration cycle can be reduced greatly and thecalibration method becomes easier.This paper develops automatic calibration function of ignition timing based on thefeedback of speed and fast calibration for optimum ignition MAP chart was achieved.Online ignition advance angle correction function is developed to optimize ignitiontiming offset problems caused of the wear or other causes of engines.In order to increase the scope of application of the electronic control system, thispaper develops a constant speed control system with natural gas engine based onCascade PID for generators. According to the changes in engine operating conditionsand external load, it changes the amount of the gas (air and natural-gas) throughreal-time adjustment of the electronic throttle opening. With this method, it willstabilize the engine speed within the set speed range quickly to adapt the requirementsof the actual operation of the generators.In order to reduce the development time of ECU and cut down on workload of thetest, this paper has developed a communications module calibration between the systemand the ECU based on the serial communication protocol to achieve a calibration system software for ECU memory data read and write operations. It conductselectronically controlled systems and CNG engine bench testing and debugging match,and completes a preliminary calibration of the injection and the MAP of ignition。Theresults of bench test indicate that the engine runs stationary and the effect of eachfunctional module of electronic control system has been tested normal.