Nowadays, natural gas conforms to the conditions of environmental protection and renewable energy, which plays a significant role in the future development of mankind. It has made some progress in applying natural gas to the automotive industry. As we all know that the source power of automobile comes from engine, therefore, based on the study on the control algorithm of gas engine, this paper aims to provide theoretical basis for further application of gas engine. This paper analyzed PID control algorithm, fuzzy control algorithm and fuzzy PID control algorithm, designed corresponding controllers based on the algorithm principles, applied these three algorithms to the idle control process of the automobile gas engine. This paper concluded that the fuzzy PID control algorithm is of higher superiority through contrastive analysis on the control effects of theses three algorithm in the process of cooling high idle start, switching high idle to low idle and switching low idle to high idle.

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With the increasing number of vehicles, society and environmental problems become much more seriously. Aiming at the serious problems, CNG engine, which has better emission performance, has been paid much more attention. However, the CNG engine also has its own disadvantages, such as engine power deterioration, great influence of different mixture ratios of the gas and air on the optimum ignition time of the engine, and so on. Therefore, adaptive control for the air-fuel ratio and ignition timing should be properly adjusted with the consideration of the engine power, economy and emissions. There are two methods of controlling the ignition timing: mechanical and electronic control. In this paper, we develop an adoptive control method based on electronic control. According to the verification, the method can improve the efficiency of the CNG engine. It can be shown the validity of the adoptive method.