Flexible Control Strategy Of Common Rail Diesel Engine

Electronic control technology of high pressure common rail was the only control technology of diesel engine to meet above Euro Ⅳ emission regulation, and the control strategy has gradually become complicated and flexible. The working substance of high pressure common rail diesel engine is that the injection fuel in cylinder is transformed into the external output torque through the oil combustion, and is ultimately a torque demand control. In addition, the fuel atomization in cylinder and the injection rate Impact of the fuel pressure in the common rail pipe, which affect the combustion process. Multiple injection start point and injection quantity is a important control link for the whole control system. So, by analysis of the control demand for high pressure common rail diesel engine, the flexible control strategy based on "torque the rail pressure, injection" were put forward, and the researching work were investigated as follows.(1) Researching the control strategy of flexible control architecture for torque control and control sub-modulesFuel quantity of injection was determined by the torque demand of engine. And air-fuel ratio between the intake air and fuel injection quantity was an important factor in combustion control. The main control channel and leading contol channel of information flow in torque control architecture made the control of air and fuel to unity and coordination. The main control channel was the main channel of engine torque control flow, whose data was a base value. The leading control channel was a dynamic compensation for the main control channel in the mutation condition of the engine.Through the research of the control modules for control function and boundary condition, it was established that the respective control models with a certain characteristics of flexible control.In the relevant modules of idle-speed control, it was constructed that the control subframe at idle-speed by means of the control strategy of "client-server". According to the different operating conditions of the engine, control algorithms among the PI, PD or PID switch were designed in some sub-module of torque control, and a multi-parameters selection scheme of PID control were put forward.(2) Researching the compound flexible control architecture of rail pressure control and control strategy of the sub-moduleAccording to the analysis of the rail pressure control needs, the solution of rail pressure control architecture was proposed, which was open loop control at engine start and the automatic switch to the cascade control after starting end. This architecture had some flexible features that the open loop control with the fast response was able to quickly build rail pressure, which belonged to the coarse, and cascade control was relatively complex, which belonged to fine tune.In order to change too strong or too weak effects for the integral and derivative of the conventional PID control under certain conditions, the main controller and auxiliary controller in cascade control system adopted some control algorithms with separable integral, first-order differential and variable PID parameter.(3) Researching the control strategy of flexible control architecture for accurate injection control and sub-moduleAccording to the analysis of the multiple injection control needs, a coordinate solution of the control architecture for multi-injection was proposed.With the use of injection status word, the multiple injection coordinator can select the pre injection controller, main injection and post injection controller. This solution can also resovle the combination model of multiple injection, and whether pre injection and post injection is released.For release of audit injection and accurate calculation of starting point, fuel injection quantity and injection duration, the main injection, pre injection and post injection controller was helpful to the accurate control of the combustion process of the engine. These calculations were related to the specific injection combined with minimum fuel injection quantity, the minimum injection starting point, main injection quantity.(4) The experimental verification of the flexible control strategy and related hardware driver on high pressure common rail diesel engineThe software in the loop test was run at the test platform of circuit driving board, ES1000hardware equipment. It was to be run that the torque control, rail pressure control and flexible control strategy in the engine starting, idle speed, acceleration and deceleration experiments, whose the dynamic control response and stability was better.In order to realize the software control system, it was chiefly designed that the driving circuit for the electromagnetic valve of high pressure pump and the solenoid injector. By means of the hardware driving design for the electromagnetic valve of high pressure pump, the driving current feedback of the rail pressure control system software composed the inner loop of cascade control. In the nozzle of the hardware drivers, using Infineon TLE6282as the main driving chip, was researched of the hardware driving solution for electromagnetic nozzle of "Peak-Hold" current type, and completed the engine bench test with the previous software control system.