Small Non-road SI Engine Control Model And Optimization Research

Due to numerous advantages, such as reliable performance, compact structure, low cost, convenient for carrying and operation, Small non-road SI engines are widely used in the fields of garden pruning, agricultural irrigation, emergency power and small construction machinery. Theses have brought about a boom in the production. However, because energy shortage and environment issues have aroused much more focus from different levels, the formulation of more strict emission regulations accelerates accordingly, enabling electronic control system for small non-road SI engine to become one of the most effective method to solve this problem.Based on the concept of model design, Simulink software is used to establish a small non-road SI engine control model, which is divided into four basic modules including data acquisition module, engine parameter calculation module, the state management module and synchronization task scheduling module. These modules mentioned are respectively responsible for data acquisition, work condition judgment, injection and ignition parameters calculation, and crankshaft state judgment. During the design process of this model, simulation test is applied to improve the reliability.Basic model is built for calculating the fuel injection pulse width based on the average gasoline modeling ideas. Firstly, according to the conservation of energy inside the air intake system, basic model is transformed from the air charge coefficient mathematical expressions to adapt of 170 F small gasoline engine by analysis and the related parameters are simplified. And the inflatable coefficient calculation model is set up to calculate for the air volume into engine cycle. Secondly, the fuel injection flow rate is obtained by fuel evaporation and oil film formation algorithm. Eventually, basic injection pulse width of diverse working condition is established through the injection flow characteristic and cycle fuel injection quantity.In order to improve the control precision for fuel injection volume and spark timing, the basic fuel injection pulse-width, basic ignition advance angle and ignition energy are revised by considering different working conditions and environmental factors. What is more, revision strategies are determined and corresponding revision models are built up. The basic injection pulse width correction model contains the battery voltage correction, inlet temperature correction, body temperature correction, working condition of starting correction, idle speed condition correction and transient conditions correction. The basic ignition advance angle correction model is comprised of the body temperature correction, inlet temperature correction and idle speed condition correction.The control model was verified for hardware-in-loop through the engine simulation platform. Then a 170 F gasoline engine was selected as the prototype to validate and to optimize the control model. Calibrations for the MAP data in the model were conducted and engine performance was also tested. The results show that the control model can achieve good control quality for small non-road SI engine and meet all requirements for power, economy and emissions performance.