Vibration reduction in electric bus during acceleration and gear shifting

Abstract

Electric vehicles have replaced many gasoline vehicles in urban environments. The magnitude of vibrations and emissions from electric vehicles are less than those from conventional gasoline-powered vehicles. However, electric vehicles still have mechanical vibrations, such as those created by the power system. During vehicle acceleration, driveline vibration is very prominent. This work focuses on vehicle vibration caused by the electric powertrain in electric vehicles under rapid acceleration/deceleration and gear shifting. Since the dynamic response of an electric motor is rapid, driving torsional vibration arising from acceleration/deceleration and gear shifting is typically transmitted from driveline to vehicle’s body, adversely affecting a driver’s comfort. This work presents a novel effective control logic that reduces vibrations from an electric driveline system. This system controls the electric motor to suppress driveline torsional vibration transmitted to the driver’s seat, effectively reducing vertical vibrations and enhancing driver comfort. This work conducts simulations and hardware tests. In the development of the driveline and motor control logic, Adaptive Modeling Environment for Simulation analytical software is applied to create the driveline system model. To model structural vibrations, HyperMesh is used, and LS DYNA is applied to simulate free vibration and forced vibration. The analytical results for free vibration are compared with empirical data. The analytical results for driveline dynamics are applied as input for the finite element model to analyze forced vibration. Vibrations from the electric driveline move through the motor mount and frame to the driver’s seat track. The simulation results demonstrate this control logic strategy applied to an electric bus motor controller effectively reduces fluctuation in driveline torque during acceleration by up to 84.19% and during gear shifting by up to 44.96%. The reduction in vibration of the driver’s seat track during fixed-gear acceleration was maximal at 45.96%, and the reduction during gear shifting was 24.11%.