Optimal control solution of the automotive emission-constrained minimum fuel problem

The automotive industry is confronted with the conflicting goals of improving fuel economy, reducing exhaust emissions, and maintaining vehicle driveability. Difficulties arise in the application of optimal control theory to this problem because transient models of the fuel, emission and driveability responses do not exist. To circumvent these difficulties, the mathematical models are replaced by a sophisticated experimental test setup. To demonstrate the applicability of the optimal control approach without a mathematical model, the problem of the hot-start optimization of fuel economy subject to emission constraints problem is solved. Operational considerations necessitate the direct incorporation of the control functions into the gradient-type solution algorithm. The solution of this problem demonstrates the feasibility of the experimental optimal control approach. The second problem involves the cold-start portion of the Federal Test Procedure (FTP). The transient influences of the engine and catalytic converter warmup are analyzed by the optimization procedure and are reflected in the optimized control functions. Finally, the hot-start optimization program is generalized to include an explicit surge-type driveability constraints on the controls. Comparison of the results of the hot-start problems reveals the trade-off between fuel economy and driveability.