Model-based temperature control of a diesel oxidation catalyst

The problem studied in this article is the control of a DOC (diesel oxidation catalyst) as used in aftertreatment systems of diesel vehicles. This system is inherently a distributed parameter system due to its elongated geometry where a gas stream is in contact with a spatially distributed catalyst. A first contribution is a model for the DOC system. It is obtained by successive simplifications justified either experimentally (from observations, estimates of orders of magnitude) or by an analysis of governing equations (through asymptotic developments and changes of variables). This model can reproduce the complex temperature response of DOC output to changes in input variables. In particular, the effects of gas velocity variations, inlet temperature and inlet hydrocarbons are well represented. A second contribution is a combination of algorithms (feedback, feedforward, and synchronization) designed to control the thermal phenomena in the DOC. Both contributions have been tested and validated experimentally. In conclusion, the outcomes are evaluated: using the approach presented in this article, it is possible to control, in conditions representative of vehicle driving conditions, the outlet temperature of the DOC within ±15 °C.