Influence of driver, route and vehicle mass on hybrid electric truck fuel economy

A broadly applicable procedure for measuring fuel economy of heavy-duty Hybrid ElectricVehicles (HEVs) is lacking. The classical approach of fuel economy testing is to follow a velocitytimesequence (drive cycle) with the vehicle on a dynamo test bench. However, these velocity-timesequences do not reveal hybrid drive train performance under different operating conditions. In thispaper, a distance-based method is suggested to test heavy-duty HEV fuel economy. It is herebystandard practice that heavy-duty vehicles tend to use full throttle during acceleration, regardlesstheir current power-to-weight ratio. Using this method, the sequence/cycle is evaluated for differentvehicle masses, and for both optimal decelerations, which maximizes the recoverable energy, aswell as legal maximum deceleration rates, which minimizes the route drive time. Simulationsreveal that these operating conditions have large influence on the hybrid system performance; fueleconomy improvement of heavy-duty HEV, compared to conventional heavy-duty vehicles, underdifferent operating conditions could vary as much as 1 to 40 %.