Development Of Engine Timing Signal Source And Research Of Timing Synchronization Strategy

With increasingly stringent emissions regulations,engine control has been put forward higher requirement for real-time,fault tolerance and precision. In the gasoline engine management system (EMS),the crankshaft position sensor and camshaft position sensor signal are two key input signal. The two signals are fundamental basis of the electronic control unit(ECU) for judging cyclinder NO and accurately ignition timing control,fuel injection timing and variable valve timing(VVT) mechanism camshaft phase. Therefore, the research of engine position management for application layer is critical. Further in the ECU software debugging stage in order to test correctness, stability and reliability, provide different timing signals by a small signal resource to verify signal recognition and diagnosis, determine the position(cylinder judgment), calculate the position of synchronization, detect the phase and verify algorithms of speed and gradient of speed. It makes software debugging space unlimited and saves cost.Based on the16-bit,double-core microcontroller MC9S12XET256develop a portable timing source to produce two-way pulse and realize angle-time synchronization control and phase adjustment, to generate crankshaft and camshaft position sensor signal of any speed. On this basis,study the control strategy of engine position management system. The main contents are as follows:(1) Based on the basic needs of the timing signal source, design the hardware system, including the minimum system of microcontroller, power module, D/A conversion and bipolar conversion circuit, output driver circuit, LCD display driver circuit and Ethernet communication interface circuit, etc.(2) Task-based scheduling mechanism and interrupt service system, divide software system tasks and assign task priority. In accordance with the modular principles design signal source software including system initialization settings, the signal output, LCD display, the input analog quanity gathering and network communication function and so on. Based on Visual Basic6development environment, develop backstage management software on the basis of Ethernet communication way to set output signal mode, signal frequency and the parameters of phase.(3) Build the basic structure of engine position management system, determine the process of mode judgement, propose signal processing and plausibility check method and synchronization strategy of crankshaft and camshaft signal. Including camshaft signal encoding and signal synchronization method. In three synchronization engine modes (normal mode、failure mode of camshaft and crankshaft), study the synchronization strategy of various modes. Based on ASCAT software platform build the model of engine timing strategy, and build a crankshaft-camshaft signal source for co-simulation.(4) Through joint commissioning of hardware and software of system, acquire the output signal by oscilloscope to demonstrate the feasibility and reliability of the timing source by comparison of the speed of crankshaft signal and the phase of camshaft signal providing ECU the test and debugging tools. The research of engine position management control strategy provide basic groundwork for development of engine ECU software. By building the model of strategy verify the correctness of engine timing strategy through simulation debugging.