The Study Of Control Strategy Based On Single-Point Injeetion

As an advanced diesel injection system, high-pressure common rail injection system offers a good control over the volume and number of shots in each injection cycle, which helps reduce emission and fuel consumption. The injection flow meter designed here is required to exert a reliable control over the injections in each injection circle and accurately measure the injection volume and laws.The paper offers a presentation of research status as well as research background concerning the injection flow meter both home and abroad. Also, insights are given into the functions of the injection flow meter and research aims along with contents of the present paper. The mains contents are as follows:A detailed analysis of measurement principle is made from the perspective of structure and methods of measurement and control are proposed in the paper. And also, comments are made on advantages of the chosen measurement schemes in terms of accuracy and efficiency. On the meanwhile, three crucial components are discussed, namely:piston cylinder, oil discharge magnetic valve and displacement transducers.Based on the function and main parameters, a systematic explanation is made concerning injection flow meter in terms of hardware circuit, which is divided into MCU control circuit, displacement signal acquisition circuit, magnetic drive circuit and communication interface circuit. In the present research, each component is carefully chosen and introduced. Power supply, reset circuit, clock circuit, and highly sophisticated displacement signal acquisition circuit are presented in the paper. Furthermore, working principle of displacement transducer is explained in detail. Calibrated results and experiment results are compared. Moreover, noise-preventing circuit is designed against noise distraction in the lab.Large current is employed to realize the quick start-up of high-speed magnetic valve as the result of the fact that the time of fuel injection is comparatively short. In order to reduce power loss, the current through coil goes from high to low which helps guarantee the operation of injection system. However, large current easily causes the coil to heat up. In order to avoid this, current used to maintain the valve working is minimized to reduce loss.The injection flow meter, adopting RS232-CAN bus protocol as its communication protocol, has MCU as the core. In this research, communication converter was designed according to the characteristics of RS232 interface and CAN bus. And the proper conversion of communication protocol is realized with the help of hardware circuit and software programs. RS232 is rather fragile as the main PC interface with a short-distance transmission. CAN bus is characterized with distant transmission, strong calibrating power, multi-nod communication and convenient networking as well as better match with other control system. Therefore, the combination of the two buses contributes to the operation of the whole system.In the final part, what is analyzed include anti-interference of the hardware, especially the setup of components, routing of PCB, production reliability. Based on the shortest life period of five years and the worst series connection, the result of reliability analysis is predicted to be 0.9878, which can satisfy industrial needs.