An individual cylinder AFR estimator using a single proportional oxygen sensor (UEGO) situated at the confluence point of the exhaust manifold has previously been described ([1],[2]). As this model is nonlinear, it proposes a linear slicing by zone [3], enabling it to apply the estimator to the entire range of engine speeds.
However, several problems remain; the model [3] is complicated and therefore difficult to program in an electronic engine control, the model is no longer valid with the ageing of sensors, injectors, or the motor, it is impossible to diagnostic the defaulting organ or one which deviates.
The work set out in this article describes a model, and the conditions for its identification, which resolve these. The resultats obtained on engine tests show that the model is robust, precise and capable of estimating cylinder AFR as well as diagnosticing an injector or UEGO sensor deviation.