Multivariable PI tuning and application to engine idle speed control

A multivariable proportional-integral (PI) tuning strategy is developed and the advantage of the design is illustrated in an automotive application. The multivariable control design technique developed has disturbance rejection as its main objective rather than set-point tracking, which is the focus of most of the MIMO PI tuning techniques so far in the literature. The benefit of the design is that it does not try to minimize interactions in a multivariable plant and instead uses the interactions to achieve better disturbance rejection. The application of the control design technique is in multivariable speed and air-to-fuel ratio (A/F) control of a lean-burn natural gas engine to achieve less speed drop during load transients at idle