Real-time multibody application for tree harvester truck simulator

A real-time simulator for a tree harvester has been developed for training in more effective vehicle and cutter operation and tree management. The equations of motion of the constrained mechanical system of the tree harvester are expressed using a recursive formulation. The hydraulic actuator modelling of the harvester is based on lumped fluid theory, in which the hydraulic circuit is divided into discrete volumes where pressures are assumed to be distributed equally, while pressure wave propagation in pipes and hoses is assumed to be negligible. For modelling purposes, valves are broken up into a number of adjustable restrictors, which can be modelled separately. The contact model used comprises two parts: collision detection and response. Collision detection identifies whether, when and where moving bodies may come in contact. Collision response prevents penetration when contact occurs and identifies how it should behave after collision. A penalty method is used in this study to establish object collision events. The major achievement of this study is combining these three modelling methods in the application of a real-time simulator.