Extending the Inverse Vehicle Propulsion Simulation Concept-To Improve Simulation Performance
Drive cycle simulations of longitudinal vehicle models is an important
tool for design and analysis of power trains. On the market today
there are several tools for such simulations, and these tools use
mainly two different methods of simulation, forward dynamic or
quasi-static inverse simulation. Forward dynamic simulation is
capable of describing the dynamic behavior of a system to a high level
of detail, but suffers from long simulation times. On the other hand,
quasi-static inverse simulations are very fast, but lack the ability
of describing additional dynamics in a good way. Here known theory for
stable inversion of non linear systems is used in order to try to
combine the fast simulation times of the quasi-static inverse
simulation with the ability of describing the dynamics as in the
forward dynamic simulation. The stable inversion technique together
with a new implicit driver model forms a new concept, inverse dynamic
simulation. Using this technique the need to develop dedicated inverse
models is reduced, and it is shown that a large class of models that
can be simulated in forward dynamic simulation also can be simulated
in inverse dynamic simulation. In this respect, three powertrain
applications are used that include important dynamics that can not be
handled using quasi-static inverse simulation. The extensions are
engine dynamics, drive line dynamics, and gas flow dynamics around
diesel engines. These three cases also represent interesting
mathematical properties such as zero dynamics, resonances, and
non-minimum phase systems, i.e. unstable zero dynamics. The inversion
technique is demonstrated on all three examples, and the feasibility
of inverse dynamic simulation of these systems is shown. Moreover,
using the three examples, inverse dynamic simulation is compared to
forward dynamic simulation regarding simulation set-up effort,
simulation time, and parameter-result dependency. It is shown that
inverse dynamic simulation is easy to set up, gives short simulation
times, and gives consistent result for design space exploration. This
makes inverse dynamic simulation a suitable method to use for drive
cycle simulation, and especially in situations requiring many
simulations, such as optimization over design space, powertrain
configuration optimization, or development of powertrain control
strategies.
Anders Fröberg
2005
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Last updated: 2021-11-10
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