TITLE:
Generation and Analysis of Hybrid-Electric Vehicle Transmission Shift Schedules with a Torque Split Algorithm
AUTHORS:
Nicholas J. Connelly, Derek I. George, Andrew C. Nix, W. Scott Wayne
KEYWORDS:
Hybrid-Electric Vehicles, Torque Split Algorithm, Shift Schedule, Shift Map, Cost Function, SOC Dependent
JOURNAL NAME:
Journal of Transportation Technologies,
Vol.10 No.1,
January
7,
2020
ABSTRACT: The increased concern over global climate change and
lack of long-term sustainability of fossil fuels in the projected future has
prompted further research into advanced alternative fuel vehicles to reduce
vehicle emissions and fuel consumption. One of the primary advanced vehicle
research areas involves electrification and hybridization of vehicles. As
hybrid-electric vehicle technology has advanced, so has the need for more
innovative control schemes for hybrid vehicles, including the development and
optimization of hybrid powertrain transmission shift schedules. The hybrid
shift schedule works in tandem with a cost function-based torque split
algorithm that dynamically determines the optimal torque command for the
electric motor and engine. The focus of this work is to develop and analyze the
benefits and limitations of two different shift schedules for a position-3 (P3)
parallel hybrid-electric vehicle. a traditional two-parameter shift schedule
that operates as a function of vehicle accelerator position and vehicle speed
(state of charge (SOC) independent shift schedule), and a three-parameter shift
schedule that also adapts to fluctuations in the state of charge of the high
voltage batteries (SOC dependent shift schedule). The shift schedules were generated
using an exhaustive search coupled with a fitness function to evaluate all
possible vehicle operating points. The generated shift schedules were then
tested in the software-in-the-loop (SIL) environment and the
vehicle-in-the-loop (VIL) environment and compared to each other, as well as to
the stock 8L45 8-speed transmission shift schedule. The results show that both
generated shift schedules improved upon the stock transmission shift schedule
used in the hybrid powertrain comparing component efficiency, vehicle
efficiency, engine fuel economy, and vehicle fuel economy.