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Analysis of Unconventional Powertrain Systems
Sector:
Event:
22nd FISITA Congress
Language:
English
Abstract
A system optimization approach has been developed to configure
and analyze hydraulic energy-storage based propulsion systems. The
powertrain synthesis problem is formulated as an optimization
problem of minimizing the engine fuel rate over a finite time
interval. The solution process is driven by energy management and
control strategies, which determine the transmission ratio and the
hydrostatic pump/motor unit displacement such that the engine can
be operated at its minimum fuel rate.
This approach has identified a powertrain consisting of an
automatic four-speed transmission plus a hydrostatic pump/motor
unit and accumulator used to regenerate and store vehicle kinetic
energy. Within the limitations of our analysis, the hydraulic
hybrid system has shown potential for significant improvement in
fuel economy over a conventional system. These limitations are: the
use of an optimum energy management strategy which may be difficult
to capture in a real-time controller; the practicality and
transient effects of turning the engine on and off; the packaging
of all the subsystems into a vehicle; and the lack of hydraulic
noise assessment. Using the approach in this paper, optimal energy
management and control strategies have been developed and their
effects on fuel economy have been quantified. The analysis has
shown that the fuel economy gains are due to turning the engine on
and off and to using stored energy to power the accessories and/or
launch the vehicle.
This research effort has assessed the potential of a hydraulic
hybrid powertrain vehicle system. Bounds on the predicted fuel
economy gain were determined as a function of sensitivities to
subsystem parameters.