Study On Air Path Control Algorithm Of Gasoline Engine

With the development of the electronic technology and upgrade emission regulations as well as fuel prices continue to rise, the control of the engine have become increasingly. In the premise of ensuring the best fuel economy and lowest exhaust emissions, it re-quires that the engine has good transient characteristics and dynamic output. To meet the control requirements, many scholars and car manufacturers get together to acceler-ate the research and development of the automobile engine control systems and related technology products. And with the increase of electronic systems in motor vehicles, auto-motive products have been developed from simple mechanical products to mechatronical products. Engine control system also changes to the centralized control from a single-function control. These show that the engine mechanical structure and electric control system are becoming greatly complicated. The traditional engine control systems cannot well coordinate conflict demands of the torques, and they have low extensibility and poor flexibility. In this case, the torque-based engine control system of a modern engine control is becoming to be an inevitable trend of development. The control thought of the torque demand as the center considers the torque demands the driver and the vehicle together during the car running in the roads, and through the air path control, ignition angle con-trol and fuel injection control to achieve the specified torque, and then to ensure that the engine can achieve optimal emissions and fuel consumption in various conditions. Under the Torque-based engine control system, the rapid and accurate air path control affects not only the adjustment of the ignition angle but also the precise control of air-fuel ratio. Therefore, Either from the development trend of the engine control system or from the gas and the air-fuel ratio control of the ignition angle into account, the modeling and control of air path system are critically important.In this paper, we consider the traditional four-cylinder PFI gasoline engine as the research object. Adopting for torque demand as the central control strategy, air path system modeling and control algorithm of gasoline are developed. First of all, according to air path tracking requirements, both of the air path system based on inverse-dynamics and the dual-closed-loop are designed in order to manage the output of engine torque. Secondly, offline simulation experiments are carried out which show that dual-loop air path control system has a better tracking performance. Finally, we set up an engine hardware in-the-loop simulation platform in which the real throttle is embedded. The platform experiments verify that dual-closed-loop air path control system not only ensures a good quality of the performance for reliability in real-time but also the effectiveness in practical application.Firstly, take all issues in to consideration such as dynamic coupling, difficulty of mathematical description for engine volumetric efficiency ect, a mixed description of mech-anism/MAP engine model is established in using the mean value modeling theory and experimental data chart commonly utilized in automobile engineering. The engine dy-namic model enDYNA which has high precision is used as a virtual engine to calibrate the parameters of engine model and data of the MAPs required in modeling and controllingThen, the gasoline engine model is tested by enDYNA under the same throttle opening and speed conditions. The results verify that the mean value model has good accuracy and validity.For the characteristics during the actual working process of the engine, analysis is carried out based on the mean value engine model. Contribute to engine torque demands and control requirements of the air path, the control system based on inverse-dynamic is designed, including the intake manifold pressure planning, throttle opening planning and tracking. And then, experiments of offline simulation in the environment of gasoline engine model and high-precision engine dynamics model enDYNA are given. Experiment results show that the air control system based on the dynamics can be applied in the case of simple structured controller, easy realization in hardware, and low precision of systems.Additionally, dealing with the problems that the control system mentioned above can't satisfy the tracking control requirements of enDYNA or even more complex system, throttle opening tracking control is retained and an out-loop controller with Lyapunov stability is designed by using feedback linearization method, which constitute a dual-closed-loop air path control system. Moreover, in order to illustrate dual-closed-loop air path control system has a better tracking performance than the inverse-dynamics one, mean experiments, experiments of comparison and all speed condition under the enDYNA environment are given respectively. The simulation results indicate that the dual-closed-loop system can meet the requirements of precision tracking control in both steady and transient conditions with satisfactory performances.In order to further test the controller's validity in real-time and the effectiveness in realistic condition, the hardware in-the-loop platform based on xPC-Target and dSPACE real-time system is constructed. On one hand, the controller rapid prototyping experi- ments are carried out to validate the dual-closed-loop controller's real time capacity. On the other hand, the real throttle is embedded to the platform in which the dual-closed-loop experiments for the dual-closed-loop air path controller are developed. The result of the experiment show that the control system mentioned above gives a good tracking performance even in a more authentic condition. And it is emphasized that this study is of great worth in practical application.However, further research needs to be done since some problems are still remain to be solved gradually. For example, in this paper, a fixed set of PID parameters is committed for the throttle tracking controller while it cannot satisfy the precision tracking control requirements of throttle in the real vehicle. Instead of the fixed parameters, varying PID parameters should be adopted to meet high-precision tracking control requirements. Due to uncertainty of the road conditions, traffic lights, pedestrians and other factors in the urban road, the engine will be operated on the transient conditions such as acceleration, deceleration, starting etc. Therefore, the MAPs which are calibrated in the conditions of steady-state and ambient temperature need real-time correction to confirm the changes of engine speed conditions and temperature. Moreover, during the modeling process, the modeling error of air flow through the throttle is ignored as well as the changes of the intake manifold temperature. In addition, in the electronic throttle modeling part, the nonlinearity of the return spring and throttle friction are considered, but no attention are paid to the nonlinearity of the gear backlash. Hence, the robust controller and robust stability analysis can be on a topic of the further research.