On-line identification of vehicle fuel consumption for energy and emission management: An LTP system analysis

An Energy Management (EM) system traditionally relies on (quasi) static maps offering efficiency parameters of the vehicle powertrain. During a vehicle´s life span, these maps lose validity, so optimal performance for EM is not assured. This paper presents a proof-of-concept for a novel measurement system, estimating important engine and generator characteristics on-line during driving. The generator applies a small excitation signal to the combustion engine and by means of correlation techniques and feedback control, the incremental fuel cost for generating electric power is estimated. This information is very relevant for EM in Hybrid Electric Vehicles. No additional sensors (e.g. torque estimators) are needed. Under mild assumptions it is shown that the measurement system satisfies a Linear Time Periodic (LTP) System. Harmonic analysis as well as Floquet Theory are used to analyze performance and stability criteria. Simulation results support this analysis and demonstrate good noise rejection of the system.