Fuel Savings by Closed Loop Control

摘要

A new control concept was developed to minimize the power losses of the drive line for off-road vehicles, which consists of a combustion engine and a hydrostatic transmission. This paper discusses the use of the developed control concept for a drive line, which consists of a combustion engine and a power split drive, where a hydrostatic transmission is used in combination with planetary gears. The drive line control concept is based on two separate closed loop controls, one for the power split drive and another for the combustion engine. The command values for both control loops are calculated under consideration of the characteristic curves of the combustion engine and the losses within the power split drive, including the loss characteristics of the hydrostatic transmission and the mechanical gear losses. Using an online working optimization procedure, the command values of the drive line control are determined without limiting the vehicles driving power. Therefore, the effective specific fuel consumption of the combustion engine is introduced as an indicator to be optimized in order to minimize the power losses for the whole power range. To optimize the fuel consumption we need a model as the target function of the optimization procedure, which will also be presented here. Based on this target function, a direct optimization procedure will be introduced to solve the optimization task online. The realization and potential of the control concept including the optimization procedure and the closed loop controls will be presented based on the investigation of a realistic typical drive maneuver for off-road vehicles. Therefore, a comparison of simulation results for this maneuver will be presented to show the effectiveness of the developed drive line control and to analyze the driving behavior and the fuel savings potential.