METHOD AND APPARATUS FOR CONTROLLING A MULTI-MODE POWERTRAIN SYSTEM

A method for operating a powertrain system includes selecting a plurality of candidate transmission ranges associated with a present powertrain operating point and deselecting candidate transmission ranges not associated with the present powertrain operating point. A high resolution engine speed/torque search is executed for each of the selected candidate transmission ranges. A low resolution engine speed/torque search is executed for each of the deselected candidate transmission ranges. Each search is executed to determine a respective minimum power cost for operating the powertrain system in one of the candidate transmission ranges in response to an output torque request and output speed. A preferred transmission range is determined from the candidate transmission ranges. A preferred engine operating point is determined corresponding to the minimum power cost for the preferred transmission range. The powertrain system is controlled in the preferred transmission range with the engine operating at the preferred engine operating point.