2018-01-1006 Published 0 3 Apr 2018 © 2018 SAE International. All Rights Reserved.A Development of Fuel Saving Driving Technique for Parallel HEV Jeong Soo Eo, Sung Jae Kim, Jiwon Oh, Yeon Kwang Chung, and Young Joon Chang Hyundai Motor Company Citation: Eo, J.S., Kim, S.J., Oh, J., Chung, Y.K. et al., “A Development of Fuel Saving Driving Technique for Parallel HEV,” SAE Technical Paper 2018-01-1006, 2018, doi:10.4271/2018-01-1006. Abstract This paper examines the effect of pulse-and-glide (PnG) driving strategies on the fuel efficiency when applied on parallel HEVs. Several PnG strategies are proposed, and these include the electrical, mechanical, and combined PnG strategies. The electrical PnG strategy denotes the hybrid powertrain control tactics in which the battery is charged or discharged according to the power demanded while main - taining the constant vehicle speed. On the other hand, the mechanical PnG strategy denotes the powertrain control tactics in which the vehicle accelerates or decelerates according to the power load while minimizing the battery usage. The combined PnG strategy involves both electrical and mechan - ical strategies to find a balanced point in between them. Here, a tradeoff relationship between the fuel efficiency and the vehicle drivability related to the tracking performance of the desired target speed is revealed. In the assessment of the feasi - bility of applying each of the formerly mentioned hybrid driving strategies, the causes of driveline heat loss are recorded and analyzed by their types. These include the engine heat loss, engine friction loss, motor loss, and the resistance loss. The motor loss includes all of the electrical energy loss induced in the powertrain electronics, and the resistance loss includes the loads acting on the vehicle such as the aerodynamic drag and rolling resistance. These factors are quantitatively analyzed for different driving strategies along with the related fuel efficiency in an integrated manner. The experimental validation is conducted using a real HEV equipped with a gasoline spark-ignition engine, transmission-mounted electric drive, and a 6-speed dual clutch transmission. 1. Introduction Along with the reinforcement of the vehicle regulation related with emission gas and fuel mileage, eco-friendly vehicle technology has been drawing increased attention. Such trend has also caused daily drivers to explore and share various driving techniques [ 1, 2, 3, 4, 5] for fuel mileage improvement. Pulse and glide (PnG) driving skill is an example, and this has been practiced by the hyper - milers throughout the world. Cruise control function in conventional vehicles uses a fixed engine operating point for a given load, and it may not be placed so close to the engine OOL (optimum operating line). So to improve such shortcoming, hypermilers repeat the cycle of acceleration and deceleration while keeping the average vehicle speed as the same as that when using the cruise control function. Such maneuver may truly improve the fuel mileage by shifting the engine operating point closer to the OOL. However, this currently must be implemented passively by the drivers, which may increase driver’s fatigue and lead to inconsistent result in fuel mileage improvement due to the driver’s inappropriate application of the PnG skill. Hence car manufacturers have launched automated PnG control function [ 6, 7, 8] with ACC [ 9, 10, 11] and platoon control [ 12], but most of them were aimed for the application in conventional vehicles driven by internal combustion engines. So this study focuses on validating the effect of PnG driving strategy applied in parallel hybrid electric vehicles (HEV), and analyzing its future applicability. The engines in HEVs are generally designed to operate along the OOL [ 13, 14, 15] by using the motor to level the load. However, such strategy inevitably involves energy loss in the power electronics (PE) during the charging and dischargi