Three-parameter transmission gear-shifting schedule for improved fuel economy

Traditionally the transmission gear-shifting schedule is based upon the throttle position and the vehicle (or engine) speed. This paper proposes to add a third parameter, called the terrain coefficient, to form a three-parameter gear-shifting schedule for improving the fuel economy of a vehicle. The terrain coefficient is a compound parameter consisting of the road grade and the rolling resistance coefficient. It can be estimated in real time by the proposed multi-step recursive least-squares method. The dynamic programming and the moving least-squares method are adopted to optimize the gear sequences and to generate the three-parameter gear-shifting schedule. The proposed gear-shifting schedule is evaluated against the traditional two-parameter gear-shifting schedule via Simulink simulations and on-road experiments using a heavy-duty vehicle. The simulation results for the Urban Dynamometer Driving Schedule and the US06 Supplemental Federal Test Procedure driving cycles show that the fuel economies of the proposed gear-shifting schedule are improved by 3.3% and 2.7% respectively over that of the traditional two-parameter schedule. The experimental results indicate that the three-parameter gear-shifting schedule improves the fuel economy by 3.5% over the traditional schedule with a satisfactory acceleration performance.