Prestudy of a Power Management of a Cut-To-Length Forest Harvester with a Hydraulic Hybrid System

A Cut-To-Length (CTL) forest harvester is used for felling, delimbing and bucking of the tree stems as forwarder is used to forward the logs cut to length to roadside landing for highway transport to the refining facilities like saw- and pulp & paper mills. Fuel consumption of forest harvesting operation is becoming a more and more important cost factor as the fuel prices are raising constantly. A number of studies exist on various hybrid systems related to on- & off-highway vehicles and work machines. This paper deals with technological possibilities and potential to cut down fuel consumption of a CTL harvester by implementation of a hydraulic hybrid system that is mainly designed to take care of the highest power demands. In order to be successful in this aim, a detailed analysis of the work cycle and present power management and transmission systems are needed. Engine load data together with relevant Arcnet and CAN bus messages as well as needed hydraulic system parameters are logged during actual work in order to understand the actual nature of the application in terms of work cycle. This study is focusing on a hydraulic hybrid system, as it seems to be an applicable solution to mobile work machinery in question. However – a background review of other hybrid solutions is also given. Some of the relevant advantages of a hydraulic hybrid system in forest machine application are also explained in this paper. Based on the prestudy and analysis on the work cycle – a promising potential for hydraulic hybrid system can be seen in a CTL harvester. Future work to be done is proposed to include simulations to make a more detailed dimensioning of the components and design of the system possible already before building an actual test setup.