Experimental analysis of wheel bearing friction losses under realistic driving cycles on a component and roller test bench

The ongoing electrification of vehicle powertrains brings attention to components with a minor contribution to overall friction losses in research and development. To optimize the overall energy efficiency, it is essential to analyze and reduce the losses in these components. Wheel bearings are of particular interest in this context, as their friction losses affect both the driving and recuperation phases. These losses are dependent on temperature, mechanical loads and the bearing mounting situation into the vehicle. The analysis of friction losses and their dependency on the factors mentioned above is usually conducted by measurements on component test benches to allow an isolated evaluation. In contrast, the friction losses of the complete drive system are measured on powertrain or roller test benches. In this context, the factors affecting the losses in wheel bearings may deviate from the measurements obtained on component test benches. The purpose of this paper is to analyses the effect of two different measurement methods on the resulting wheel bearing friction losses, depending on the operating conditions. To evaluate the differences, vehicle measurements were performed on a climate-controlled roller test bench, as well as component measurements on a friction torque test bench for identical driving profiles. The losses occurring on the roller test bench are determined by using a data-driven methodology developed for this purpose, taking various influencing factors into account. In contrast, a methodology based on direct force sensor measurement technology is applied to determine the losses on the component test bench. Finally, the measured friction losses are compared with regard to the driving profiles and the influencing factors, and analyzed de-pending on the test benches and methods used. The results show both methods enable a reliable determination of wheel bearing friction losses, but the losses deviate depending on whether the measurements are performed on the climate-controlled roller test bench or component test bench.