Vehicle cruise: Improved fuel economy by periodic control

-It is shown that time-dependent periodic control can improve the fuel economy of vehicles in cruise. The time-dependent controls considered are relaxed steady-state (RSS) control, quasi-steady-state (QSS) control and quasi-relaxed steady-state (QRSS) control. Examples are given which show that QRSS control may give better performance than either RSS or QSS control. Properties of optimal cost functions, dependent on the minimum required average speed, are derived. The possibility or impossibility of improved performance through the use of QRSS, QSS and RSS control is investigated in terms of assumptions on the vehicle drag and fuelconsumption functions.