Numerical solution for multivariable idle speed control of a lean burn natural gas engine

This paper proposes a numerical solution to the idle speed and air-fuel ratio control of a lean-burn natural gas engine. Since more than one variable is involved (speed and air-fuel ratio), multivariable control techniques are used. A new gain tuning method is devised for the control gain tuning of a multivariable non-decoupling PI controller. For a disturbance rejection problem, this type of controller improves the performance of one variable by compromising the other. The proposed tuning method also makes it possible for the designer to choose between the amount and type of trade offs in performance between variables. The proposed method uses an expert systems approach to numerically find the optimum control gains needed for the closed loop system to meet the specified performance level.