Research On Mode-oriented Control Strategy Architecture And Key Technologies Of Diesel Engine

Increasingly stringent emission regulations and fuel consumption standards impose more demanding requirements on efficient,clean and low-carbon operation of diesel engines.The operating performance of a diesel engine greatly depends on the control logic and control parameters of control strategy.An effective measure to achieve energy saving and emission reduction of diesel engines is synergistic application of various advanced technologies by building multiple control modes in the control strategy.Therefore,the study of control strategy architecture and the key technologies of diesel engine multi-mode control has important theoretical significance and engineering application value to achieve the energy saving,emission reducing,green manufacturing and economic development of diesel engines in the future.Synergistic application of diesel engine technologies requires the electronic control unit(ECU)contains multiple control modes,which corresponds to a series of optimal control parameters.Simultaneously,the optimal operation of diesel engines under multimode can be realized by coordinated switching between multiple groups of control parameters.However,as the control system of diesel engine becomes more and more complex,the control parameters of diesel engine constitute a large and complex data set.Because the complexity of data sets,establishing multiple data sets and achieving the switch between them in ECU have become a great challenge to realize the multi-mode optimal control of diesel engines.To achieve multi-mode optimal control of diesel engine,the strategy architecture for diesel engine control mode was deeply studied based on the self-developed ECU software and hardware platform.The coordination mechanism of control mode and the response mechanism of functional subsystem were designed.Moreover,the control strategies supporting multi-mode of fuel system and intake system were systematically studied,while the multiple data sets were established,solving the key control problems of diesel engine.The research mainly focuses on the following aspects:(1)In order to achieve multi-modes optimal control of diesel engine,a multi-mode control-oriented strategy framework was proposed,which supports up to 16 control modes and each control mode supports 8 stages.The coordination mechanism of the framework follows the sequence of mode request,mode coordination,and mode response.Subsequently,a control mode coordinator was designed,which can receive multiple mode requests simultaneously and determine the set mode for the control system.The set mode determined satisfies the conditions and has the highest priority.Furthermore,the control mode response mechanism and the method of control parameters switching for the subsystem are designed.Based on the proposed mechanism and method,the control strategies of fuel injection system and intake system which supporting multi-data sets were developed.Finally,taking DPF manual regeneration as an application case,the multi-modes control-oriented control strategy framework was validated through the DPF regeneration bench test.The results demonstrate that the framework is works well in multi-mode control of diesel engine.Especially,the framework is easy to maintain and expand,which can satisfy the control requirements of multiple intricate data sets in the control strategy.It is a system-level framework to achieve the multi-modes collaborative control of diesel engine in the future.(2)For the determination of the cycle injection quantity of diesel engine,a calculation strategy based on indicated demand torque coordination is designed.Moreover,the control strategies of limiting torque,starting torque,high and low idle speed control,constant speed control are developed.Excess air coefficient of smoke limitation strategy and set speed of constant speed control strategy were implemented the control of multiple modes.The results of the mentioned studies are as follows.Firstly,the coordination control of starting torque,accelerator pedal demand torque,high and low idle control torque,and external request torque can be achieved based on the coordination strategy of indicated demand torque.Secondly,the high and low idle speed control torque could be seamlessly combined with the accelerator pedal demand torque so that the flexible control of diesel engine high and low idle speed regulation torque intervention process could be realized.Thirdly,the protection and emission limits of diesel engine could be effectively implemented by torque limiting strategy.Additionally,the constant speed regulation of diesel engine with good stability could be implemented by constant speed control strategy through external torque request interface.Lastly,the proposed ramp control strategy of diesel engine starting torque is a better method to improve the starting performance of diesel engine,which can reduce the HC emission and shorten the starting time of starting process.(3)The injection characteristic control strategy supporting multi-mode control was researched,and the control strategy with multiple data sets of desired rail pressure,desired injection combination,desired injection quantity and desired injection starting point were developed.Dual closed-loop common rail pressure feedback control architecture based on rail pressure and the current of metering unit was designed.Moreover,the influence of pre-control and current feedback on rail pressure was explored.The pre-control of rail pressure can improve the transient response characteristics of rail pressure control.While,the current feedback of metering unit can enhance the control accuracy of rail pressure.The multi-injections control strategy and the influence of multi-injection overlap on diesel engine were deeply investigated.The overlap of two injections could adversely affect injector and diesel engine performance Therefore,an evaluation method and suppression strategy of multi-injection disturbance based on injection pulse width was proposed.It can effectively detect and prevent multiple injection disturbances and is qualified for the coordination control of injection timing of multi-injection.(4)The control strategy of the intake system supporting multi-mode control was researched.The control strategy with multiple data sets of desired boost pressure,desired intake air mass,desired actuator opening of EGR and boost pressure open-loop control strategy were developed.Besides,the EGR and VNT control strategies were designed,which is a double closed-loop control strategy based on control physical variable and actuator position feedback.The dynamic limiting strategy of the set opening of VNT turbocharger and EGR valve was researched.Subsequently,the validation experiment was carried out using the EGR valve.The results show that the dynamic limit strategy of setting opening can effectively prevent the EGR valve from hitting at the mechanical stop position and realize the mechanical stop position protection of the actuator.In addition,the experimental on the stuck of EGR was carried out.The monitoring and protection strategy of EGR sticking based on control deviation was proposed,which can effectively avoid EGR damage caused by the large driving current for a long time from EGR valve sticking.