Application-Oriented Stochastic Energy Management for Plug-in Hybrid Electric Bus With AMT

Abstract

Taking the complex but regular characteristic of bus routine into account, the stochastic dynamic programming (SDP) might be a more potential method to optimize the energy management for plug-in hybrid electric bus (PHEB). However, the discrete transmission system and the continuous power system make it a complicated multi-dimensional optimal problem especially for PHEB with automated mechanical transmission (AMT), and the optimal decisions, which obtained based on historical data, might not always well satisfy the driver's expectation to vehicle maneuverability under various driving conditions. To solve these problems, an adaptive approach based on the SDP is proposed in this paper. Exhaustively, the SDP is propelled into the input of the transmission to only optimize the torque-split under the special gearshift logic, which reduces the dimensions of optimization and obtains more applicable optimal sequences. Then, an adaptive factor, which trade-off the vehicle fuel economy and drivability in real time by dynamically adjusting the gearshift points and the torque split, is developed for the variation of the complicated bus driving cycles. The simulation results demonstrate that the proposed method could well respond the variations of the driving conditions (e.g. road grade and vehicle load etc.). Furthermore, the performance of the proposed method is detailed discussed by comparing with different control strategies. More significantly, the proposed approach has a great potential to apply in actual.Index Terms-Plug-in hybrid electric bus (PHEB), stochastic dynamic programming (SDP), adaptive factor, optimal energy management.W 0018-9545 (c) be obtained from the IEEE by sending a request to pubs-permissions@ieee.org.2 Furthermore, R. Johri et al. proposed a simultaneous optimization of power split and gear shift logic for HEV using SDP [21]. Great contributes have been made for above researches on optimizing the power management to some extent. However, most of them mainly concentrate on the conventional HEVs or PHEVs without transmission and seldom take the bus routine into account. Considering the versatile characteristic of driving conditions, it is a complicated multi-dimensional optimal problem especially for energy management of PHEB with AMT.[21] proposed a good method to simultaneous optimal the power split and gear shift, however, the optimal results, which are mapped as two independent and constant lookup-tables, might not always well respond the variable driving conditions. Due to the strictly inter-corresponding relationship between power split and gearshift, it would break the optimal decisions and highly deteriorate the vehicle fuel economy if any changes happened on the optimal gearshift to obtain the good maneuverability. Moreover, the simultaneous optimization would highly increase the calculate burden, and the complicated optimized results would jeopardize the real-time operation. Therefore it is necessary to decouple the gearshift logic from the whole optimization.This paper proposes an adaptive...

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