On power loss minimisation for heavy vehicles with axle-wise and modular electrical propulsion and friction braking

Licentiate thesis, 2023

The main challenges for battery electric heavy vehicles are improving the payload capacity and driving range for different applications. These are mainly influenced because of battery power density, different vehicle configurations, and powertrain design. Therefore, a unique powertrain design for various vehicle configurations leads to a compromised driving range. Exploiting the features of the number of driven wheels and cost-neutral scalability of the electric machines adds to the over-actuation and provides opportunities to minimise the power losses.
       In this thesis, to explore the potential of minimising the power losses, two powertrain topologies are analysed, namely, single e-axle group and multiple e-axle group. Additionally, a configuration of the multiple e-axle group called cruise and startability axles, with two different types of electric machines and gear ratios, is also presented. To coordinate the usage of actuators within these topologies, an algorithm that minimises the power losses of electric machines and friction brakes, while considering axle force limits, is introduced.
       The power loss minimisation algorithm is then evaluated for a vehicle configuration using inputs, representing real-world operating points. The results show that the axle force limits introduced as constraints in the algorithm, influence the power loss minimisation potential of the topologies. For the inputs under study, the single e-axle group uses a large proportion of friction brakes instead of regenerative braking, resulting in high losses. Furthermore, it is shown that using multiple e-axle group topology with power loss minimisation increases the regeneration capabilities and vehicle performance.