Hybrid Electric Vehicle Modeling and Control

Anthony Phillips
Vehicle Electronic Systems Dept.
Ford Research Lab.

As consumers and the government continue to demand increased fuel economy and reduced emissions from their vehicles, auto manufacturers are increasingly looking toward new technologies to meet this demand. One alternative under consideration is that of hybrid electric vehicles (HEVs). An HEV combines some of the benefits of electric vehicles (efficient and clean motive power supplied by an electric motor, regenerative braking) with the features of a conventional vehicle that consumers expect (convenient refueling, long driving range). However, these benefits come with increased complexity in the powertrain design. Instead of having one motive power source, there are two which can each act independently or in combination. The complexity of an HEV powertrain together with the vehiclebs many operating modes demand that a supervisory or hybrid controller be developed at the vehicle level to guarantee stable and consistent operation. Inherent in this controller is a logical structure to guide the vehicle through its various operating modes and a dynamic control strategy associated with each operating mode to specify the vehicle demands to each subsystem controller. Capturing all possible operating modes and guaranteeing smooth dynamic control transitions from one operating mode to the next are significant challenges in the controller design. A formal method for designing this supervisory controller has been developed. A description of the method and its application to an HEV will be presented.