Utveckling av en dynamisk Simuleringsmodell av en skotare

Sammanfattning: The predominant forestry harvesting method is based on the harvester-forwarder method, the harvester folds, branches and cuts trees, and sorts the logs into piles, while a forwarder transports the logs to a landing area. This master thesis work is about realization of a dynamic forwarder simulation model, and its purpose is to provide an integrated forwarder simulation model in MATLAB/SimMechanics where the forwarder is based on a concept using pendulum arms to connect wheels and chassis. Active suspension control is developed and implemented into the simulation model, and finally compared in simulation with passive suspension. In a first step, an integrated forwarder simulation model is developed, containing a simplified forwarder model, a tire-to-ground interaction model and a test track model. The simplified forwarder model is based a rigid multi-body system with a spring-damper suspension of the pendulum arms. The tire-to-ground interaction model calculates the reaction forces, friction from the ground and applies the propulsion force. The test track model is a simplified version of the real test track in Skogforsk. The propulsion wheel torque control is used to regulate the forwarder speed. The simulation results indicate that the model works properly to show dynamic properties when the forwarder is driven on uneven terrain. In a second step, the original passive suspension system is replaced with a combined passive and active suspension system proposed in this master thesis in order to reduce undesired dynamics. The comparison shows that the combined passive and active suspension system can reduce some of the undesired dynamics. However some more advanced strategy is required for better performance. The main aim of the thesis was to develop the simulation model including the forwarder, a general test track and the tire to ground interaction. This aim has been achieved. Additionally, a graphical user interface (GUI) is developed for making the simulation model more user-friendly and modular, enabling the user to easily adjust model parameters.