Uniformity Control Of Each Cylinder Of Diesel Engine Based On Instantaneous Speed Signal Of Crankshaft

With the increasingly prominent of China’s energy and environmental problems,the emission regulations of internal combustion engine have become more and more strict.The advancement of internet technology and power battery technology has enabled the rapid development of new energy vehicles and pure electric vehicles,while traditional vehicles have more room for technological breakthroughs with the help of more precise electronic control technology.Diesel engines have been widely used in many fields by virtue of their superior power,economy,durability and reliability.The idle speed condition is an important working condition of the diesel engine for vehicles.When the diesel engine runs at idle speed,the body vibrates strongly,the noise is obvious,and the emission is poor.This is not only due to poor combustion conditions at idle speed,but also the inconsistent combustion and different expolsion pressure of each cylinder,resulting in uneven transient torque output by each cylinder,and a large range of fluctuations in the instantaneous speed of the crankshaft,resulting in vibration and noise,which directly affect Vehicle idling comfort and emissions.In order to reduce the fluctuation of the instantaneous speed,maintain the consistency of the instantaneous speed fluctuation of each cylinder,improve the vibration and noise of the diesel engine at idle speed,and promote the localization of electronic control system of the diesel engine.Based on the domestic open ECU-HT5 control unit development platform and GW2.8TC high pressure common rail diesel engine,this paper develops and studies the inhomogeneity control strategy of each cylinder under idle speed conditions.According to the characteristics of idling condition of diesel engine,this paper firstly introduces the principles of the main sensors,gives the tooth judgment logic,put forward the calculation formula of instantaneous speed and average speed,the processing method of air flow signal,the calculation formula of single-cylinder intake air volume and the fuel injection quantity control strategy based on the target torque;meanwhile,in order to realize the stable control of the rail pressure,the rail pressure open-loop control model of the starting stage,the target rail pressure calculation method,and the rail pressure feedforward and PID closed-loop control model are built,which is of great significance for realizing the consistent control of the fuel injection amount of each cylinder under the idling condition.Secondly,the bench test is carried out and the test data is analyzed.By processing the instantaneous speed signal of the crankshaft,the difference between the peak value and the valley value of the instantaneous speed of the power stroke of each cylinder of the diesel engine is calculated,that is,the maximum fluctuation of the instantaneous speed of each cylinder,and use the deviation of the maximum fluctuation of the instantaneous speed of each cylinder and the mean value of the fluctuation in a cycle to characterize the degree of unevenness of the rotational among the cylinders.Finally,on the basis of the torque-based PID idle speed control strategy developed by the research group in the early stage,the fuzzy control method is used to control the non-uniformity of each cylinder.The fluctuation deviation is used as the input of the fuzzy controller,and the output is the compensation value of fuel injection quantity of each cylinder.If the rotational speed fluctuation of a certain cylinder is greater than the average rotational speed fluctuation of the cycle,it means the ignition pressure of the cylinder is too large,and the decrement correction control is required;otherwise,the incremental correction control is performed.The simulation model of the control strategy developed in this study is built through Matlab/Simulink,and on this basis,the control strategy is integrated into the control program of the prototype control software development system in the form of control code,and then the control program is executed in the Codewarrior software compiler.After the debugging is completed,it is burned into the ECU（HT5）,and the bench test is carried out on the test prototype.The research results show that the use of fuzzy control method for fuel compensation control can effectively reduce the fluctuation of rotational speed between cylinders in the cycle under idle speed conditions,effectively improve the unevenness of each cylinder and make the working process of the diesel engine more stable,reduce vibration noise and improve the performance of the whole machine.