基于模型的怠速空燃比PID控制策略的研究

The Study of Model - based AFR Control Strategy on PID at Idle Speed Operation

本文借助于车载动态实验数据，采用系统辨识的方法建立喷气脉宽与空燃比之间的动态模型。在此基础上应用位置式和增量式两种PID控制策略进行反馈控制。仿真结果表明，尽管位置式PID反馈控制输出很快收敛到设定理论空燃比，并维持在理论空燃比，但考虑到其每次输出均与过去的状态有关，并对空燃比偏差进行累加，在实际使用时有可能引发重大事故；而离散增量式PID控制算法不但对控制目标的调节时间短，而且对扰动具有更好的鲁棒性，控制精度较高。

A dynamic model between CNG injection pulse width and AF ratio is established using system identification method and the data of on - board dynamic experiment. Both position - type and incremental PID controlling strategy are applied to this model. The simulation results show that it shall cause serious accidents when applied to real vehicle because that its output is relevant to the passed state and cumulate errors of the AF ratio although the output of position - type converges fast to the set stoichiometric air -fuel ratio and maintains at this ratio; while the discrete incremental type adjusts not only the controlling objective fast but also has better robustness and higher control accuracy.