Abstract
A multi-mode power-split (MMPS) hybrid electric vehicle (HEV) has two planetary gearsets and clutches/grounds which results in several operation modes with enhanced electric drive capability and better fuel economy. Basically, the battery storage system is involved in different operation modes to satisfy the power demand and minimize the fuel consumption, whereas the complicated operation modes with frequent charging/discharging will absolutely influence the battery life because of degradation. In this paper, firstly, we introduce the solid electrolyte interface (SEI) film growth model based on the previous study of the battery degradation principles and was verified according to the test data. We consider both the fuel economy and battery degradation as a multi-objective problem for MMPS HEV by normalization with a weighting factor. An instantaneous optimization is implemented based on the equivalent fuel consumption concept. Then the control strategy is implemented on a simulation framework integrating the MMPS powertrain model and the SEI film growth map model over some typical driving cycles, such as New European Driving Cycle (NEDC) and Urban Dynamometer Driving Schedule (UDDS). Finally, the result demonstrates that these two objectives are conflicting and the trade-off reduces the battery degradation with fuel sacrifice. Additionally, the analysis reveals how the mode selection will reflect the battery degradation.
Highlights
Electrification is the trend in clean and efficient vehicle development [1]
The second-generation Volt reforms the hybrid transmission, which has been researched as a Multi-Mode Power-Split (MMPS) configuration with two planetary gearsets [6,7]
To evaluate the effect of the Multi-Objective Optimization (MOO) control strategy, two solutions are obtained with factors α = 0.3 and α = 0 which, respectively, correspond to emphasizing fuel saving and a balance between consumption and battery aging
Summary
Electrification is the trend in clean and efficient vehicle development [1]. Considering the battery cost and customers’ anxiety of driving mileage, hybrid electric vehicles are still the key technology from an industrial viewpoint. Two representative power-split hybrid vehicles are Toyota’s Prius and the Chevrolet Volt The former uses an input-split configuration with single planetary gearset (PG) [4]. The second-generation Volt reforms the hybrid transmission, which has been researched as a Multi-Mode Power-Split (MMPS) configuration with two planetary gearsets [6,7]. The MMPS HEV can dominate the degree of electrification among the operation modes, e.g., parallel, power-split, electric driving. A typical design is picked that transforms the basic Ravigneaux configuration into a new four-shaft hybrid transmission working as a power-split device [24], as shown in Figure 1a.The simplified lever scheme is shown, where PS1 is the sun gear in the first planetary gearset (PG1) connecting with. Here we assume that the ratio between the output shaft and EMB in the Single EM mode is the same as in the parallel mode
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