Research On Multiple Injection Control Of High Pressure Common Rail Diesel Engine Based On Fuzzy Adaptive Theory

Diesel engines are widely used in the engineering field due to their advantages of strong power,good economy,wide adaptability and easy maintenance.However,environmental problems are becoming more and more serious.In addition to sophisticated hardware facilities,it also need to develop more stringent control strategies to improve the efficiency of diesel engines.The quality of the control strategy of the electronically controlled injection system has a great influence on the performance of the diesel engine and the emission of pollutants.Therefore,it is of great significance to design multiple injection control strategy based on the injector with fast dynamic response.The main work content and achievements of this article are:By analyzing the composition of the fuel injection system of the high-pressure common rail diesel engine and the working process of each component,based on the operating characteristics of its fuel injection system,the traditional solenoid valve injector was replaced with a piezoelectric injection.Due to the nonlinear variation of the piezoelectric ceramic stack of the actuator part of the piezoelectric injector,the needle valve lift error is too large.Therefore,the fuzzy adaptive PID control algorithm is introduced to carry out the voltage across the piezoelectric ceramic stack precise control,thereby improving the stability of multiple injection control.Using the Matlab fuzzy control toolbox to establish the fuzzy adaptive PID control module,first set the fuzzy theory of the voltage deviation,the voltage deviation change rate and the three parameter corrections in the PID of the piezoelectric ceramic stack in the piezoelectric injector domain and membership function,and then determine the fuzzy control rules,and finally through the center of gravity method to get fuzzy,to obtain a certain amount of voltage control,according to the control requirements in Simulink environment construction conditions and rail pressure state judgment module and rail pressure,fuel injection control module.In order to verify the effectiveness and feasibility of the control model,a controlled physical model needs to be established.AMESim is selected as the modeling software of the high-pressure common rail system.And use the secondary development function in AMESim and the interference signal under Simulnk to simulate the nonlinear changes of the piezoelectric ceramic stack.The common rail system is divided into three parts: a high-pressure oil pump,a common rail tube,and a piezoelectric injector,and then each part is assembled into a complete common rail system.Through the interface setting,the simulation model of the control model under Simulink environment and the controlled physical model under AMESim environment is conducted.Before co-simulation,unit test the control module under Simulink environment to verify whether the unit module conforms to the designed logic function;then integrate the unit module,and verify the control model through co-simulation test.The results show that the control model can be judged and execute multiple injection based on multiple parameters such as diesel engine speed,minimum injection rail pressure,etc.In order to check the control effect of the fuzzy adaptive PID control algorithm in the target stable state,the target displacement of the piezoelectric actuator is set to 0.5?m,and the maximum relative error from the target displacement in the stable state is 0.85%;At the same time,in order to check the control effect of the target in a dynamic state,a sinusoidal signal tracking test is set for the piezoelectric actuator,The amplitude is 0.2 ?m,the initial value is 0.2 ?m,the frequency is 250 Hz,the maximum The error is 2.42%;in the multiple injection co-simulation process,the needle valve lift target displacement is set to 0.19 mm,and the needle valve lift in the main injection state is selected for analysis in multiple injection.The maximum lift of needle valve is 0.19587 mm when there is no fuzzy PID control,and the relative error is 3.09%.Under fuzzy adaptive PID control,the maximum lift of the needle valve is 0.19211 mm,and the relative error is 1.11%.The fluctuation amplitude of needle valve lift under the action of fuzzy adaptive PID control algorithm is significantly smaller than that of the needle valve lift under no fuzzy adaptive PID control algorithm.It can better improve the injection stability and control accuracy of the piezoelectric injector in multiple injection.