Gasoline Engine Idle Speed Modeling And Control

Most of the contamination is produced and 30 percent of total fuel is consumed by the engine in an idle state. So idle speed control (ISC) is the currently research hotspot. The main aim of ISC is maintaining the natural idle speed at the targeted idle speed. There are many unmeasured torque disturbances acting on the engine in an idle state, for example, little torque disturbances brought by electric windows and car heat seats, large torque disturbances brought by air conditioner and power steering. ISC is more and more difficult as more and more car electronic equipments.A four-cylinder engine is researched. A mean-value model for gasoline engine ISC is built by system identification method with an in-depth analysis of the engine in an idle state. As it is a nonlinear model, differential geometry method is applied to make the nonlinear model to be linear. As the features of the disturbances, a robust H-inf controller is designed.The mean-value model for gasoline engine ISC is built by extracting advantage from theoretical modeling method and system identification method. This model is as precise as others built by system identification method. And it is also continuous like others built by theoretical modeling method. It is suitable for control system design.The essence of feedback linearization by differential geometry method is finding new state variables for the system which will make the nonlinear model to be linear. The physical meaning of the new state variables is analyzed and the linear model of the idle speed model with disturbances is given.The disturbances acting on engine in an idle state are produced by vehicle equipments; for example, air condition, power steering and so on. They are uncertain and have limited energy. So the idle speed controller is designed based on the H-inf control theory. The simulation results show that this controller is very efficient.