A Methodology for Modelling of Driveline Dynamics in Electrified Vehicles

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.