Transmission and Control Strategy Optimization for a Parallel Hybrid Electric Micro-Utility Vehicle in Urban Drive Cycles

The aim of this work is to optimize the transmission design and control strategy for a post-transmission parallel hybrid micro-utility vehicle in congested urban driving conditions that are typical of India and other countries. The powertrain of the hybrid vehicle is modeled using a backward modeling approach. A simple gear shifting strategy for the manual transmission based on gear shifting maps is developed. Optimum operation lines for operating the IC engine in hybrid modes are determined. A rule-based battery charge sustaining control strategy is developed. The equivalent fuel consumption of the baseline hybrid powertrain is found to be substantially lower than that of its conventional counterpart for three low speed urban drive cycles that have frequent starts and stops. To further improve the performance, the transmission and control strategy parameters are optimized using a genetic algorithm with the objective of minimizing the equivalent fuel consumption per unit distance traveled over these three representative drive cycles. The fitness function value for the optimized hybrid powertrain is found to be 22.8% better than that of the baseline hybrid powertrain.