Wideband SI Engine Lambda Control

Long term control of the AFR (Air/Fuel Ratio) of spark ignition engines is currently accomplished with a self-oscialling PI control loop. Because of the intake/exhaust time delay, the oscillation frequency and hence bandwidth of this loop is small. This paper describes a new approach to the design of this control loop using a novel observer system.

In this way the bandwidth of this important loop is increased by a factor of 2 - 6 times, leading to more accurate oberall AFR control. Moreover the observer approach is so robust and allows such feedback levels that it reduces significantly the accuracy required in the calibration of the base fuel contrl system with which it is to be used.

It can be used with either convention- or advanced observer based- base fuel strategies.