Development of Optimization Based Control Strategy for P2 Hybrid Electric Vehicle including Transient Characteristics of Engine

Abstract

Models based on steady-state maps estimate fuel consumption to be 2–8% lower than real experimental measured values. This is due to the fact that during transient phases, the engine consumes more fuel than in steady phases. Some literature has addressed the conventional vehicle engine model that improves fuel consumption estimation’s accuracy during the transient state. However, the characteristics of the engine in the scope of hybrid electric vehicles (HEVs) with an integrated control strategy is yet to be covered. The controller is designed to minimize engine operation in the transient phase to enhance energy savings. In this paper, the correlation between fuel enrichment in transient and steady-state fuel estimation is established as transient correction factor (TCF). Its explanatory variable was the engine torque change rate. This paper describes the influence of engine transient characteristics on the fuel consumption of a mild HEV. The work attempts to improve the fuel economy of the HEV by introducing a penalty factor in the controller to optimize the use of the engine in transient regimes. A backward vehicle model was developed for a production vehicle with a conventional powertrain and validated experimentally using data available online. The corresponding hybrid vehicle model was developed by integrating the electric motor and battery components with the conventional vehicle model. A P2 off-axis configuration was chosen to this end as the HEV architecture. A conventional equivalent consumption minimization strategy (ECMS) was used to split the torque request between the engine and the electric motor. This control strategy was modified with TCF to penalize the engine torque change rate. The results of the simulation show that due to less transient operation of the engine, the fuel consumption was reduced from 923 g to 918 g under the US06 driving cycle. The fuel economy of the model has been simulated for UDDS and HW drive cycles too, and fuel consumption improved by 4.4 g and 3.2 g, respectively. It has been verified that by increasing the battery capacity twice (14s24p), the limitations imposed by the battery capacity can be minimized and the fuel usage can be reduced by 9 g in the UDDS cycle.

Impact of Engine Inertia on P2 Mild HEV Fuel Consumption

“…Several works can be found in the literature that are dedicated to the accurate estimation of the actual fuel consumption of the engine by optimising the torque or the power split. In [23,24], the precision of HEV fuel economy calculation was improved by integrating a transient behaviour of the engine. Moreover, by incorporating the engine transient behaviour in the controller, the reduction in its transient operation was achieved, resulting in more stable operation.…”

“…The works that consider the transient operation of the engine [23,25,27,28] mainly apply transient correction factors to quasi-static fuel consumption [23,27] determined by extensive experimental data [25].…”

Optimal Control of a PHEV Based on Backward-Looking Model Extended with Powertrain Transient Effects

“…To smooth out the engine transients and suppress the related losses, the ECMS presented in [14] for an extended range electric vehicle (EREV) introduces an additional term in the cost function which penalizes the engine speed difference between two consecutive sampling intervals. In [15], an ECMS is developed for a parallel PHEV, which minimizes additional fuel consumption during engine transient. Control strategy in [16] improves upon the gear shift performance of a parallel-type HEV with double clutch transmission thus improving both the driving comfort and energy efficiency.…”

“…Energies 2022,15, x FOR PEER REVIEW 15 of 26 is proposed in this section. The BWD model extension relates to capturing the powertrain transient effects, with emphasis on transient power losses.…”