Simulation Model for Forestry Ground and Vegetation Damage

Sammanfattning: Training simulators are valuable tools in education of forest machine operators. One important part of the education is to learn about damages occurring due to the forest machines and how they can be avoided. Two types of damages are especially severe, soil compaction and formation of wheel ruts. Compaction reduces the amount of water and nutrients in the soil, and impedes root growth. Furthermore, water is gathered in wheel ruts, leading to transport of organic materia and heavy metals into water courses. These damages can be avoided through planning of the harvesting activities with respect to season, weather, and the conditions on the site. The main focus point is to avoid driving on wet soil, since wetness makes it more susceptible to damage.  The aim of this thesis is to investigate how this should be incorporated in a simulator. Implementations are made in Unreal Engine with AGX Dynamics for Unreal, which already has a deformable terrain called AGX Terrain. This terrain was investigated by creating two terrain materials, representing dry and wet Swedish forest soil, and driving a forwarder on them.  AGX Terrain was found to be simple to use and gave fair results, the rut depths were comparable in size with empirical results. However, it was limited in the sense that shearing was not taken into account and there was no possibility of having different material properties across the terrain. A potential solution to these problems is suggested, in which a more extensive way of computing stress propagation and the resulting damages is used. Further investigations has to be made in order to find out if this approach is of good use.