Multispeed EV Transmission – Gear Shift Simulation and Validation

The advancement of electric vehicle (EV) transmission systems is currently a prominent trend aimed at decreasing carbon emissions and providing eco-friendly transportation alternatives. Most of the EV transmissions are single speed, but research conducted on multi speed EV transmissions show higher efficiency, good performance, high speed and torque demand when compared with single speed counterparts. Most of the multi speed EV transmissions that are developed are of non-synchromesh type, which have direct effect on NVH, driving dynamics and durability of drivetrain components. Due to aforementioned factors, gearshift analysis becomes critical for development. Simulation model is developed at early development phase for initial feedback. Using the feedback, drivetrain can be optimized furthermore and test on physical parts can be conducted for final verification. This paper provides a simulation based approach for modelling non-synchromesh two speed EV transmission using Simulation X. The model consists complete vehicle from prime mover, gear box to wheels. Non-synchromesh gearboxes lack synchronizers, which are essential for matching the speeds of the input and output shafts during a gear change, the model is capable of 3D visualization of gear synchro ring and shifter sleeve teeth during gear shift event, which is vital to observe any gear crashing phenomenon during gear shift event and will compute parameters such as forces acting on synchro pack, synchronization time and jerk on vehicle during engagement. Additionally, this paper gives details of bench test setup for gearshift quality tuning and system level validation with vehicle controller. Simulation results show good correlation with bench level data and serve as vital feedback for initial gearshift quality assessment. Multiple iterations can be carried out on simulation model by changing design parameters of synchro pack and speed difference between input and output shafts to observe the effect on gear shift quality and validated on final prototypes.