Suspended forestry machines for sustainable forestry

Sammanfattning: Cut-to-length (CTL) logging is a mechanized two-machine solution. The harvester processes treestems into smaller logs and a forwarder transports the logs from the logging site to a landing areaaccessible by trucks. The working machines for CTL logging are heavy and their suspension systemis generally rudimentary, basically the only damping is provided by the tires. To meet futuredemands on operator comfort, sustainable forestry, and climate concerns, significant challenges areto find means for reducing daily vibration dosage, soil damage, and rolling resistance.Paper A proposes a full-scale virtual model of a four-wheeled forwarder concept equipped with twopendulum axels with an actively controlled hydraulic suspension system mounted on each wheelaxle. The simulation results are then analyzed to determine the required actuation power.Paper B presents a performance comparison of a six-wheeled medium-sized pendulum-armsuspended forwarder, with three different suspension systems; active, semi-active, and passive. Amethodology to optimize and analyze forestry vehicle suspension performance based on multi-bodydynamic simulations are proposed and applied for the studied forwarder.Paper C is a model-based investigation of the dynamic behavior of a traditional eight-wheeledbogie type of forwarder with the main focus on identifying critical issues and suggesting criteria forassessing the performance of the machine while traveling on sloped and rough terrain.Paper D investigates the performance of a novel all-wheel-drive pendulum-arm suspendedmedium-sized forestry machine with passive and active chassis suspensions. The dynamicperformance of the pendulum-arm machine concept is quantified with simulations and comparedwith a “traditional” bogie-machine.Paper E investigates how to model a tracked forwarder and how the performance comparison canbe evaluated in multi-body simulation software like Adams ATV.Paper F presents a comparison of the dynamic behavior of forestry machines with different types ofpassive chassis suspensions from three perspectives: their gentleness to terrain, operator and theirpotential for improved fuel efficiency.Paper G proposes a 12 degrees-of-freedom multi-body dynamics simulation model of a standardeight-wheeled bogie type of medium-sized forwarder and verifies the simulation model withmeasured data from the field test that was carried out the actual machine.Paper H reconfigures the model presented in Paper G and compares a medium-sized forwarderequipped with two different track units with the performance of a wheeled and bogie-type offorwarder on hard rough ground, as well as on soft soil.