Micro and Mild Hybrid Systems is a bracket term, which covers functions like Engine Stop/Start (ESS), Intelligent Alternator Control (IAC), and many others, which collectively aim at optimizing the fuel consumption by preventing the wasteful running of the engine. Engine Stop/Start system is the prominent part of the Micro/Mild hybrid systems and is the most significant contributor while reducing the fuel consumption and greenhouse gas emissions.
In the previous work of the Authors, various issues related to ESS were discussed in detail. ESS is not so popular among the customers, due to the complexities of the system operation and poor integration of the system design with the customer behavior. In addition, due to various functional safety conditions, and the traffic conditions, the actual benefits of ESS are negatively impacted. Therefore, it becomes necessary to have a different approach to the design of the systems like ESS. A different approach was implemented to design the control algorithm for the ESS, by implementing Design Thinking, in which a detailed study was performed to assess how customers actually behave during an idle stop and inputs were generated for the control algorithm design. This effort resulted in a better system design with increased improvement of fuel efficiency and better integration of the system functionality with the user behavior.
In this paper, the technical aspects of the system design are discussed in detail, with analysis of the on road data of customer behavior, analysis of the problem areas, and methods devised to improve the integration of the system functionality with the customer behavior, customer experience with the ESS, and to reduce the negative impact of the functional safety parameters, including the implementation of the system in a technology demonstrator vehicle and its performance test results. The vehicle with the new control algorithm returned a fuel economy improvement of approximately 18% over conventional vehicle, and 13% compared to the base ESS control algorithm, under actual on-road conditions.