Sequential Optimization of Eco-Driving Taking Into Account Fuel Economy and Emissions

Abstract

The regulations for diesel vehicles are expected to become increasingly more stringent. However, how to coordinate eco-driving, the diesel engine and the urea selective catalytic reduction (urea-SCR) system for fuel economy improvement and emissions reduction remains a formidable challenge. In this paper, a sequential optimization control method with three stages is designed. In stage I, the optimal driving force and braking force are obtained by solving a nonlinear optimization problem of tracking the vehicle velocity profile. In stage II, a real-time reference estimation model is designed to provide the optimal ammonia coverage ratio target. In stage III, to implement the driving force requirement and ammonia coverage ratio target, an integrated engine and urea-SCR system control method and a distributed method are proposed, respectively. The distributed method consists of a fuel injection controller utilizing a data-driven predictive method and a NH3 dosing controller utilizing nonlinear model predictive control (NMPC). The control model of the integrated method is represented by the first-order ammonia coverage ratio dynamics only. The results show that the fuel consumption is improved by 5.3% and the PM emission is reduced by 11.56% during the partial transient acceleration process, and that the fuel consumption and emissions of the integrated control method can accomplish the level of the distributed method and achieve the trade-off between the multi-objective. However, the integrated control method incurs an average computational time penalty of 15.47%.

Keywords

• Diesel vehicles
• urea selective catalytic reduction (urea-SCR) system
• sequential optimization
• nonlinear model predictive control (NMPC)
• Pontryagin’s minimum principle (PMP)