Abstract
Research and/or Engineering Questions/Objective
For “Blended-type” PHEVs, the engine is started on CD/CS, but the timing and purpose of the two stages are significant different. With the engine on/off, two kinds of energy sources are adjusted on CD, the engine working point and the thermal efficiency are optimized in CS. Along with the engine on/off, mode switching to different power demand conditions is achieved. The primary objective of this study is to analyze factors that affect the engine to be on/off, to discuss the control of engine working range through mode switching, and to gain energy distribution and efficiency optimization of the “Blended-type” PHEV.
Methodology
Utilizing Advanced Powertrain Research Facility (APRF) at Argonne National Laboratory (ANL), Full Charge Test (FCT) under different environment temperatures was designed to test the MY2012 Toyota Prius PHEV. Mechanical power flow signals (torque, speed and power of the mechanical components), electrical power flow signals (current, voltage, power of the electric components), temperature signals, emission analyzer signals, and CAN bus signals were collected. Component working characteristics, power distribution characteristics, mode switching and efficiency calculation of CD/CS were analyzed. Engine on/off and mode switching control strategy of the “Blended-type” PHEV were evaluated.
Results
The results show that as a kind of PHEV using blended control strategy, there is significant difference in timing and purpose engine on/off on CD/CS, which is mainly because of vehicle power demand (such as velocity and accelerator pedal opening), component working characteristics (such as engine coolant temperature and battery SOC), accessories power demand (such as air conditioning using in high and low temperature). With engine on/off, the vehicle enables three powertrain modes, and with mode switching, the power distribution of engine and battery is adjusted. Engine is controlled to work in a narrow range, hence its high heat efficiency and low fuel consumption are maintained while meeting the demand of various driving power.
Limitations of this study
The limitation of this study is that the testing design and control strategy analysis are based on standard environmental temperature and cycles. In the future, it is necessary to add more environmental temperatures and more complex transient nonstandard cycles, to evaluate the characteristics of energy distribution and efficiency optimization, thus excluding the influence of vehicle calibration process which is based on standard cycles on control strategies.
What does the paper offer that is new in the field including in comparison to other work by the authors?
Compared with other research results, the paper based on standard testing cycles, from three perspectives of vehicle power demand, component working characteristics and accessories power demand, combines engine on/off and mode switching, and analyzes the energy management problem for “Blended-type” PHEV.
Conclusions
As a “Blended-type” PHEV, Prius PHEV shows obvious difference at the timing of engine on/off on CD/CS, which is mainly because of vehicle power demand, component working characteristics and accessories power demand. With the engine on/off, the vehicle switches the powertrain mode and controls the engine working in a narrow range to reduce the fuel consumption. Generally, the results provide significant references for energy management strategy development for blended-type PHEVs.
Key Words : Blended control strategy; Engine on/off; Mode switching; Power distribution