Fuel Economy Prediction of the Two Wheeler through System Simulation

Fuel economy has become a key challenge for powertrain engineers due to increasingly stringent customer fuel economy requirements and government CO2 emissions legislation. System level simulation is vital in assessing the vehicle performance and fuel economy at an early stage of the product development life cycle. A workflow for a two-wheeler powertrain simulation is established and the relation between calibrations and fuel economy is analysed in order to provide a platform for powertrain development useful throughout the design life of a new powertrain concept. A map-based engine is modelled using the engine performance data obtained from engine dynamometer test bench setup so that actual fuel economy and emission performance is accounted for by the system level model. Design of Experiments (DOE) is carried out on the measured data with an objective of minimizing fuel consumption or maximizing brake power to arrive at an optimized set of data depending upon customer operating point demand. Exhaust temperature and knock limit are set as constraints for the DOE study. A full vehicle model is developed with the optimized map-based engine along with transmission, chassis and driver model. Desired drive cycle (WMTC) is used as a target velocity profile to the driver model along with a neutral gear selection strategy. Starter and idle speed control logic are included in the engine control module. The full vehicle model consists of manual transmission along with clutch dynamics followed by the vehicle body and tyre models. Powertrain matching analysis was performed using the system-level model to optimally trade off fuel economy with acceleration performance. The optimized engine map data is provided to the calibration team to develop a prototype engine model during the design phase. MATLAB, Simulink and other add-on products have been used as the platform to perform the virtual calibration studies.