The Study Of Closed-loop Control Strategy For FAI Motorcycle

With the rapid development of computer, electronic technology, as well as emission regulations'being stricter, the EFI motorcycle technology becomes the inevitable trend of future motorcycle's application. Between two control modes utilized in EFI system, the open-loop control will gradually be replaced by closed-loop control, which is more precise. In this thesis, the study is based on the closed-loop EFI motorcycle with switch type oxygen sensor (STOS) installed and the PID control theory. The Fuel injection amount feedback correction value control system which is based on the feedback signal of the STOS, is developed in order to achieve precise control of the air-fuel ratio (AFR) in different conditions.In this thesis both the STOS'working principle and the characteristic of the output signal is analyzed. With PI control theory, the logic between the fuel injection amount feedback correction value (FIAFCV) and STOS feedback signal is defined. A control strategy which could achieve rich or lean control on AFR is proposed by analyzing STOS feedback signal. Through calculating the duration of integral mode's running, with which to compare with theoretical time, the proportional parameters could be adjusted. Not only could the AFR stay rich or lean, its margin could also be controlled dynamically and accurately. So a new method is provided for the EGR technology's applying on the closed-loop EFI Motorcycles.In this thesis Fuel injection amount feedback correction value control system is developed, which is consisted of the hardware and software. The hardware is consisted of A/D conditioning circuit used for measuring the STOS's signal. The software is consisted of oxygen sensor failure diagnosis module (OSFDM), rich or lean determining module (ROLDM), and FIAFCV calculation module. OSFDM could adjust fuel injection quantity and give fault display instructions when abnormal oxygen sensor signal emerges. FIAFCV calculation module has the function of making the AFR richer or leaner besides just close to equivalence ratio by keeping the FIAFCV, so that the rich or lean control could be achieved by making the AFR kept deviating from equivalence ratio at a constant amplitude and duration.Through QJ150 motorcycle chassis test, whether the oxygen sensor failure diagnosis module could make the expected response rapidly according to the particular failure mode is verified. The actual AFR under different PI control parameters could be detected by using lambda meter. By comparing and analyzing the actual AFR, the foundation of formulating PI control parameters in the equivalence ratio, rich and lean control is laid.