Simulation study of wheel bearing friction losses at vehicle level

With the ongoing electrification of vehicles, components contributing a minor share of overall drivetrain losses are coming into focus. Analyzing these losses is crucial for enhancing the energy efficiency of modern vehicles and meeting the increasing demands for sustainability and extended driving range. These components include wheel bearings, whose friction losses are influenced by parameters such as temperature, mechanical loads, and mounting situation. Therefore, it is essential to analyze the resulting friction losses and their dependence on the mentioned influencing parameters at an early stage of development, both through test bench measurements and with the help of simulation models. To achieve these objectives, this submission presents a methodology that combines test bench measurements with a measurement-based simulation of the friction losses of wheel bearings occurring in the vehicle as a complete system under varying driving cycles and parameters. For this purpose, an existing complete vehicle simulation model is extended by a loss and thermal model of wheel bearings. The integrated loss model of the bearings is based on a measurement data- based loss map that takes the influencing parameters into account. The thermal behavior of the bearings is implemented in the model by using thermodynamic equations and is validated with test bench measurement data. Finally, the losses determined by using the simulation model are compared as a function of the driving cycles and the effects of influencing parameters such as environment temperature, vehicle speed and wheel load in order to quantify the impact of the boundary conditions on the friction losses. With the help of the simulation model, it is possible to quantify the influence of wheel bearing losses on overall drivetrain efficiency for various parameters in a cost- and time efficient manner. The presented methodology can also be applied to other bearings in the vehicle with slight modifications.