Smooth Mode-switch Control for the Powertrain of Parallel Hybrid Electric Vehicle

Changqing Du, Fuwu Yan, Zhengce Cao, Sen Wu

School of automotive engineering

Wuhan university of technology

Wuhan 430070 China

Email: cq_du@yahoo.com.cn

Abstract—Th

e coordinat

e

d control of int

e

rnal

combustion ngin and l ctric machin is vital to improve drive ability and re liability of Paralle l hybrid l ctric v hicl (PHEV). This pap r addr ss to th mode-switch problem for powertrain of PHEV, construct a model-based rapid control prototype as a controller by MATLAB/SIMULINK software and dSPACE system for mode-switch control, come up with a mode-switch control strate gy which e mploy the quick transie nt re sponse of electric machine to compensate the deficiency of transient

torqu

e p

e

rformanc

e

of int

e

rnal combustion

e

ngin

e

.

Aiming at the ge ne ral characte rs of mode-switch, a experiment schedule was implemented on the PHEV test be nch, Comparing to the control me thod by e stimating the engine toque with steady torque map, the experiment re sult show that the control strate gy propose d in this pap r can r duc th torqu and sp d fluctuation significantly during the course of mode switching in PHEV.

Keywords-parallel hybrid electric vehicle; mode-switch; control strategy

I. INTRODUCTION

Hybrid electric vehicle gets high attention of researchers and automobile factories currently due to it’s feasibility of mass production as well as low emission and high economy. Energy management strategy and the coordinated control of multi mechanical power sources are the two key problems for HEV. Energy management strategy has been researched widely[1], but for the other one, far less reports are presented. Some studies on this problem has been done just by simulations[2],[3]. This paper address the smooth mode-switch control for the powertrain of PHEV by experiment to improve the driveability, comfort and reliability of PHEV. The second part of this paper will explain the control problem addressed by this paper; the third part presents the control strategy; the forth part focus on the way how to get the real time engine torque and construct the rapid control prototype of parallel hybrid powertrain by MA TLAB/SIMULINK; the fifth part introduces the test equipment; the sixth part gives out the experiment method, test results and discussion; finally some conclusions are made in the seventh part.

II.MODE-SWITCH CONTROL PROBLEM FOR

POWERTRAIN OF PHEV

PHEV has electric machine alone, engine alone, engine drive and charge battery, engine and electric machine drive together, and regeneration brake 5 work modes. The powertrian of PHEV switch between these modes according to the pedal position, vehicle state and SOC of batteries and with the start/stop of engine if need. The target of mode-switch control is eliminating the shock caused by torque oscillation in the powertrain through coordinated control of IC engine and electric machine[4]. The reason causing total torque oscillation is the difference of torque response performance between IC engine and electric machine[5]. Considering the duration of mode-switch is very short and the vehicle speed can’t change much, the speed of the engine can be regarded as constant during the cause of mode switching. The interpretation about mode switch problem below is based on this premise.

Figure 1 Torque response of AC motor Figure 2 Gasoline engine

Figure 1 is the torque response curve on throttle

position(denoted by ) command of an AC motor, which demonstrate that the delay time is very short, not more than several milliseconds.

Figure 2 is the torque response curve on throttle command

of a gasoline engine, the curve show that the response time is more man 100 milliseconds

Maintaining the speed at 2750r.min-1, torque of a gasoline engine decrease with the rise of d /dt, even becomes unstable when d /dt is high, see figure 3.

Figure 3 Transient torque performance of a gasoline Engine

The difference of torque performance between IC engine and electric machine will cause torque oscillation and impact in the powertrain of PHEV without special handling[6], it will result in decrease of comfort, driveability and durability of

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