Optimization potential of the vehicle launch performance for start—stop micro-hybrid vehicles

Abstract

One of the primary features of a micro-hybrid vehicle is the automatic shutdown and restart of the engine to avoid engine idling when the vehicle is at rest. The system strategy and its calibration have important significance for the driveability of the vehicle in terms of the vehicle launch behaviour. An unsatisfactory vehicle launch is defined as an inferior launch performance of the vehicle resulting in a stalled engine, a launch with negative vehicle acceleration, and an aborted engine restart due to the inability of the vehicle to provide torque as demanded by the user. In this research, micro-hybrid system optimization for reduction in the percentage of impaired vehicle launch events in real-world usage has been conducted on a start—stop vehicle. The design for the six-sigma process was followed for the optimization study. A high-fidelity electrical and powertrain system and a longitudinal vehicle dynamics model for a start—stop vehicle have been developed. The model has been validated with experimental data. The drivers' behaviour for vehicle launch events from a customer clinic of start—stop vehicles has been used as an input to the model. Using design of experiments, the system has been optimized to maximize the percentage of successful launch events in real-world usage.