NVH Simulation and Validation of eBike Drive Units

Nowadays, transportation alternatives are getting more and more critical. Electric bikes (e-bikes) have shown their potential in terms of sustainable mobility. Therefore, the customer market grows accompanied by higher product expectations, such as having a rather silent ride without disturbing noise and vibrations. In this contribution, we create an elastic multi-body-model of an e-bike drive unit. The aim is to predict the noise and vibrations during operation within a transient calculation. Simplified models are used to verify and identify impact parameters, ending up in one complex and validated model solution. The final model contains the moving components of the rotor, gear stages, bearings, and free-wheel, as well as the non-movable components of e.g. stator, cover, and housing. Our approach consists of creating modal-reduced substructures, assembling bearings and gears by pre-processed replace systems containing their non-linear stiffness information and insert different forces and moments for both the electrical engine (input) and the pedal (output). This setup will be the basis for experimental validation. Thereby, its dynamical behavior is physically measured within a designed test rig. Accelerometers are used for capturing the test rig vibrations, and a laser-Doppler-vibrometer for the turning shaft vibrations. This setup will also be used for basic simulations investigations to identify dynamic system resonances, investigate the impact of the bearings’ clearance and position, and identify the impact of the different load scenarios. Once done, the test rig shall be replaced by the normal drive unit’s housing components , and validations with complete drive units shall be done. The goal is to show which model assumptions need to be made for creating an elastic multi-body dynamic model of an e-bike drive unit and to present critical dynamical states.