Road topography has a remarkable impact on vehicle fuel consumption for both passenger and heavy duty vehicles. In addition, erroneous or non-optimized scheduling of both velocity set-point and gear shifting may be detrimental for fuel consumption and performance. Recent technologies have made road data, such as elevation or slope, either available or measurable on board, thus making possible the exploitation of this additional information in innovative controllers.
The aim of this paper is the development of a smart, fuel-economy oriented controller adapting cruising speed and engaged gear to current road load (i.e. local slope). Unlike traditional cruise controllers, the velocity set-point is not constant, but it is set by applying a mathematical transformation of the current slope, accounting for the mission time duration as well. A smart shifting logic operation has also been implemented according to the following rules: i) avoid excessive shifting; ii) choose suitable gear to deal with road load while iii) respecting engine operation constraints and iv) keep the engine speed in its maximum efficiency range. Furthermore, in order to enhance fuel economy, the opportunity to decouple the engine from the driveline (i.e. using the neutral gear), when resistant load is below a given threshold, has been explored.
The proposed controller is assessed in terms of both fuel savings and travel time through an exhaustive simulation analysis carried out for a heavy duty truck running on different test routes and for multiple payload configurations.