Development and Analysis of Optimal Control Strategy for Gear Changing Patterns During Acceleration

摘要

Vehicle speed planning for heavy duty vehicles is a powerful tool to reduce the fuel consumption, and thereby the emissions released from the vehicle. By optimizing a driving mission for lowest possible fuel consumption, while still fulfilling the mission deadlines, the fuel consumption could be reduced over that specific mission. If the vehicle is driven by a combustion engine, the engine efficiency will be dependent on the load and speed requirements from the vehicle. By having a gearbox between the engine and the wheels, the engine operating points could be selected by choosing the appropriate gear. When optimizing gear changes, different model complexities can be used. To solve a gear change problem during acceleration, some key aspects needs to be taken into account, for example the loss of propulsion power when disengaging the clutch, how much clutch slip should be allowed, the time it takes for the gearbox to change the gear. The paper presents a method how to formulate and solve a fuel optimal acceleration of a vehicle, where the gear selections are in focus. The method is used to find which gears that should be used to perform a fuel optimal acceleration to a predefined vehicle speed.