Supervisory Controller for a Light Duty Diesel Engine with an LNT-SCR After-Treatment System

Abstract

Look ahead information can be used to improve the powertrain’s fuel consumption while efficiently controlling exhaust emissions. A passenger car propelled by a Euro 6d capable diesel engine is studied. In the conventional approach, the diesel powertrain subsystem control is rule based. It uses no information of future load requests but is operated with the objective of low engine out exhaust emission species until the Exhaust After-Treatment System (EATS) light off has occurred, even if fuel economy is compromised greatly. Upon EATS light off, the engine is operated more fuel efficiently since the EATS system is able to treat emissions effectively. This paper presents a supervisory control structure with the intended purpose to operate the complete powertrain using a minimum of fuel while improving the robustness of exhaust emissions. A supervisory controller assisted by look ahead information, and using a supervisory control interface that works in concert with low level local controllers, can make subsystems operate near optimal. The look ahead parametrized supervisory control calculates the set-points for the subsystems: Internal Combustion Engine (ICE), Lean NOx Trap (LNT) and the Selective Catalytic Reduction (SCR) based on the Emission Equivalent Fuel Consumption minimization strategy (EEFC). The controller performance is analyzed for the World wide harmonized Light vehicles Test Cycle (WLTC) and randomly sequenced WLTCs under different initial conditions. This paper extends upon the earlier work where an LNT-SCR EATS supervisory control structure was proposed that optimizes based on the EEFC strategy. The future work will focus on extending the approach to more subsystems and characterizing the look ahead information.