Workflow development: study of the influence of an entire pedaling cycle on the stresses of an eBike motor, considering triaxial forces and electric assistancev

Sammanfattning

This work aims to develop an alternative working method, implemented to analyse the mechanical strength of an eBike electric motor. It also presents a comprehensive analysis of the influence of a complete pedaling cycle, on the stress state of an eBike motor: the drive unit. In contrast to conventional norm tests based on static or simplified load conditions, the proposed approach considers the full temporal variability of the loads induced by the cyclist's pedaling dynamics, considering also the induced stresses of the electric assistance on the motor. The study emphasizes the effects of considering triaxial stress states during electric motor operation, with respect to the 1D force standard tests conducted so far by BOSCH eBike, evaluating how significant triaxiality is in practice. Furthermore, it consists of developing an automated workflow corresponding to an in-house norm standard test, applicable and adaptable to all BOSCH electric motors.To address this, the workflow which is developed integrates real-life load cycle data treatment, finite element stress analysis thanks to the software Abaqus, Abaqus subroutines creation and use. A significant part of the study is also devoted to the complete automation of the work routine. The methodology enables the identification of critical stress regions and provides a map of the stresses on the drive unit throughout the realistic pedaling cycle. In addition, it makes it possible to identify the main sources of stress on the electric motor and to conclude that ISO standard tests are more conservative than the tests performed in the scope of this study: triaxiality of pedal forces and electric assistance induced forces have a limited impact on the drive unit in the case of this work.