Unified Mode-Based Description of Arbitrary Hybrid and Electric Powertrain Topologies

Abstract

To find the optimal powertrain design for hybrid and electric vehicles in terms of energy efficiency and performance, automatised optimisation tools are often applied. These require a mathematical model of the powertrain configuration, which is usually done on the level of components, such as planetary gear sets (PGSs), clutches and brakes. This, however, leads to a huge design space with lots of functional redundancy. In fact, each functional powertrain mode can be realised by various component combinations. In this paper, a novel mode-based modelling technique for arbitrary hybrid and electric powertrain configurations with up to one internal combustion engine (ICE) and two electrical machines (EMs) is proposed. This allows to easily analyse multi-mode hybrid and electric powertrains on a purely functional basis. Additionally, it reduces mode describing parameters to the minimum amount required. First, an existing graphical representation of hybrid powertrains with one ICE and one EM is analysed and formalised. Based on that, virtual powertrain nodes are defined. These are used to compose all hybrid and electric powertrain modes. Five of them are presented in detail and plotted within a three-dimensional ratio plot. Using a first case study, it is shown how the ratio plot can be used to analyse arbitrary multi-mode powertrains. Within a second case study, it is demonstrated how optimal parameter sets for single-mode powertrain configurations can be identified using the derived model.