四点中心差分法在EGR阀开度PID控制算法中的应用研究

Application of Four-point Central Difference Method in EGR Valve Opening PID Control Algorithm

EGR系统通过调整阀开度实现对再循环已燃气体的流量控制,现有EGR阀开度控制算法多采用传统PID控制算法。传统PID控制算法中,差分项对数据误差和干扰较敏感,易引起振荡。针对这一问题,采用四点中心差分法代替原有一阶后向差分算法,考虑过去4个时刻的误差,通过时间加权求和得到优化的差分量,该方法可减少数据误差对差分项的干扰。采用阶跃响应曲线法对PID参数进行整定。追踪三角波目标开度的试验结果表明,利用该改进算法及参数整定方法可得到一套控制效果较好的EGR阀控制算法及控制参数,所控EGR阀可准确跟踪目标开度的快速变化,满足实际使用的要求。

The recirculating burned gas was manipulated by adjusting EGR valve opening, but the control algorithm of EGR opening usually adopted traditional PID control method. The difference term of traditional control method was sensitive to data error and disturbance so as to produce signal oscillation easily. For the problem, the four-point central difference method instead of first-order backward difference algorithm was used and the optimized difference term was acquired by the time- weighed sum of four moment errors so that the disturbance from data error reduced. The identification of control parameters was conducted with the step response curve. The results of tracing triangular wave valve opening show that the improved algo- rithm and adjusting parameter method can acquire a set of better EGR control algorithm and control parameters. The controlled EGR valve can precisely follow the rapid change of opening degree setpoint and meet the practical application requirements.