Optimal engine operating power management strategy for a hybrid electric vehicle powertrain

An engine power management method for a hybrid electric vehicle powertrain having separate components including at least two of a group comprising an engine, an electric motor, a generator, a battery and power transfer gearing, the components defining power flow paths to vehicle traction wheels, the method comprising:

• determining an engine speed for a given vehicle speed and a given total power command to minimize total powertrain power losses wherein total powertrain losses are calculated based on component losses for each component using commanded total power, vehicle speed, and engine speed;
• adding the component losses together to obtain total powertrain loss;
• determining an engine speed corresponding to minimum total power loss and storing it as data in an electronic computer memory;
• and
• accessing the data to obtain a target engine speed corresponding to current total power demand and current vehicle speed to approach a minimum total power loss and maximum total powertrain efficiency.