Book Description
In this paper, the need to develop a control strategy and test apparatus for nextgeneration hybrid vehicles was realized. The complexity of today's and future hybridvehicles necessitates the need for an equally advanced method of control that can extractthe optimal fuel economy from the system as a whole. A review of existing hybrid vehicle control strategies was performed. Overall, muchresearch has been done on the optimization of series and parallel type vehicles, butvirtually no information was found on the optimal use of advanced powersplit drivetrains. However, the control strategy concepts explored in the literature are useful, and can beextended to complex architectures like the General Motors Two-Mode design. Theequivalent consumption minimization strategy (ECMS) method developed by Rizzoni etal at the Ohio State University has proven to be a well developed control strategy that hasseen much progress over the last decade. Although it has been only demonstrated onparallel-type vehicles, it was chosen as the basis for the control strategy methodology. An in-depth analysis on the Two-Mode transmission operation was performed. Thefundamental equations for each of its range states were derived for future use indeveloping a plant model, and for use in control strategy development. The torque andspeed capabilities of each of its modes and gears were analysed. A detailed plant model was created to form a virtual test bed for control strategy development purposes. The models use empirical data provided by manufactures, which ensures a reasonable level of accuracy in portraying component constraints and efficiencies. Building on the ECMS, a similar hybrid vehicle control strategy was developed forTwo-Mode transmission based vehicles. It was modified to handle two degrees offreedom as required by the system. Its objective is to constantly minimize the totalequivalent power use in the system which is defined as the sum of the chemical power inthe fuel and the power used by the battery multiplied by an equivalency factor. Overall, the control strategy provides a strong basis for the optimal control of nextgenerationhybrid vehicles incorporating powersplit transmissions. It is suggested thatfurther research be explored in combining rule-based control methods with the developedoptimization based method since rule-based methods can add the stability required forenhanced drivability.