A Methodology for Modelling of Driveline Dynamics in Electrified
Vehicles 2021-01-0711
The assessment and control of driveline dynamics is only possible if a representative model
is available. A driveline model enables engineers to estimate the system’s reactions for
different torque inputs and shows how those inputs impact drivability and comfort. Modelling
methods in literature are frequently designed only for internal combustion engine vehicles,
disregarding electrified powertrains. To remedy that, a modelling method for electrified
drivelines is presented. It simplifies the inclusion of dynamic factors such as road
resistances, flexibility, friction, and inertias. The method consists in drawing a vertical
diagram of the drivetrain topology where each key component is represented as a block. Newton’s
second law is used to balance torque in each block connection, from propelling systems to the
wheels. State variables and inputs are defined accounting for the powertrain topology. The
result is an observable and controllable state-space model that can be further used for
driveline control or state estimation, depending on the application. This paper shows in detail
the steps to achieve such driveline models. It also proves the controllability and
observability of the models developed. Finally, the method is applied to model three commonly
used electrified driveline topologies - the series hybrid, the parallel hybrid, and the split
hybrid. The outcomes of this study are an intuitive method for driveline modeling as well as
ready-to-use state-space models of three commonly used electrified driveline topologies that
can be used for drivability analysis.