Model-based Control Design of a Diesel Oxidation Catalyst

This paper proposes a control strategy for a Diesel Oxidation Catalyst (DOC) which is grounded on a one-dimensional distributed parameter model. This first principles model for the propagation of the temperature variations accounts for spatially distributed heat generation (due to oxidation of reductants). As is discussed, heat generation can be regarded as equivalent inlet temperature variations. This fact is supported by experimental results. By nature, DOC outlet temperature response includes long and timevarying delays. An approximation of the proposed model allows to derive delays analytically, and can be used to schedule control parameters. As a consequence, it is easy to design several standard controllers for the DOC outlet temperature which account for the effects of the inlet temperature (disturbance) and the reductant (control). In this paper, simulation results are presented for a PI, a PID, and a Smith predictor. Interestingly, the three controllers use solely parameters determined from the previous analysis and do not need any extra tuning parameter. The strategies are tested on a standard NEDC driving cycle in simulation. It appears that, among these standard strategies, the DOC partial derivative equations can be efficiently controlled using the presented Smith predictor.