Research And Design Of Aftertreatment Integrated Control Unit For Exhaust PM And NOx In Diesel Vehicle

In order to restrict the serious pollution brought by the widespread application of diesel engines,corresponding regulations become more stringent.A single aftertreatment system is no longer feasible and different aftertreatment systems must be combined.Diesel Particulate Filter(DPF)can reduce over 90% soot particles(PM)produced by diesel engines.Technology of Selective Catalytic Reduction(SCR)can make the NOx conversion efficiency be up to 95%.However,the main emission of diesel engines are PM and NOx respectively.Therefore,DPF and SCR systems are indispensable parts of aftertreatment systems in the future.At present,the updating of regulations exceeds the updating of technologies,resulting in the disparity between the expected and the actual performance in aftertreatment control systems.Therefore,the aftertreatment system and integrated technology need to be further studied.Based on the analysis of the advanced DPF and SCR control technology at home and abroad,the regeneration control system of the DPF is selected and the control software layer of SCR is designed according to the Euro VI limit of PM and NOx emission.Finally,make both systems integrated reasonably.The main research contents are as follows:1?The study of principle and development method of aftertreatment system in diesel engine.The basic principle and components of SCR system are expounded and the chemical reactions inside the catalyst are analyzed.It is proposed that the software layer is developed by fully automatic code generation.The active and passive regeneration mode of DPF system is elaborated and the regeneration method and time are selected according to the domestic situation.Finally,the condition of world harmonized test cycle and the European test cycle are compared.2?The development of controller underlying driver by MATLAB/Simulink.The common bottom modules of MC9S12XEP100 chip is developed by the S-Function in Simulink.The automatic code generation function is achieved by writing the TLC(Target Language Compiler)file.In additon,writting the script to achieve the target system configuration,code generation process customization and codewarrior calling is necessary.Finally,the common bottom modules are tested correctly.3 ? The development of SCR system software layer in Simulink.The architecture of application layer software of SCR system is designed.The status judgment module,basic injection quantity of urea and feedback correction module,data management module and task execution module are established in Simulink according to the strategy by using the design ideas of sub-modular,to determine the SCR system status,calculate the amount of urea injection,obtain SCR system data and drive the corresponding actuator.4?The verification of CAN bus semi-physical simulation.The process of whole code generation is analyzed and the correrponding code is compiled and downloaded to the development board to complete the SCR controller design.The CAN bus simulation software simulates the engine node and sends information about engine to controller to control the action of urea metering pump for observing changes of urea injection in the debugging platform.5?The bench experiment of aftertreatment systems.The selected DPF regeneration control system and self-developed SCR controller are organically combined to test the emission of PM and NOx in world harmonized test cycle.The result verifies whether the aftertreatment system meets Euro VI emission regulations.The result shows that the reasonable combination of the SCR control system by the fully automatic code design and the selected DPF control system can achieve the PM regeneration and the SCR system increases the NOx conversion efficiency drastically.The PM and NOx emissions can be controlled blow the limits of Euro VI regulations.