Optimal short driving mission control for a diesel-electric powertrain

Abstract

Time and fuel optimal control for a diesel-electric powertrain in transient operation is studied using a four state, three controls non-linear mean value engine model. In the studied transients the engine starts at idle and stops when the generated energy fulfills the driving mission requirement. During the driving mission both the engine speed and output power are allowed to vary, but with a constraint on power. Two strategies are then developed and evaluated. One where the driving mission is optimized with the generator power considered a free variable, and a second strategy where the accelerating phase of the transient is first optimized and then the optimal controls for a fixed generator power are used. The time optimal control is shown to be almost as fuel efficient as the fuel optimal control even though the gain in time is large. The time optimal control also has the advantage of using constant power output, making it simple and easily implementable, whilst the fuel optimal control is more complex and changes with the length of the driving mission.