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  • 1.
    Dong, Xiaowei
    et al.
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    Mendoza-Trejo, Omar
    Ortiz Morales, Daniel
    Lindroos, Ola
    La Hera, Pedro
    Simulation-based comparison between two crane-bunk systems for loading work when considering energy-optimal motion planning2020In: International Journal of Forest Engineering, ISSN 1494-2119, E-ISSN 1913-2220, Vol. 31, no 1, p. 70-77Article in journal (Refereed)
    Abstract [en]

    Performing work for extended periods of time while using the lowest amount of resources is an important aspect for productivity in many industries. In forestry, the productivity of a forwarder is seen as the volume of material it can extract to a roadside landing in a certain amount of time, where the process of loading and unloading logs represents a large part of the work. During this process, the esnergy consumed by the machine is directly related to the speed of the crane. Thus, increasing productivity implies increasing the operating velocity of cranes. But according to current design of forestry cranes, this conversely leads to an undesired increase in consumption of resources (e.g. fuel). A second method is to alter the machine's design, such as rotating the log bunk. This article considers both methods through a simulation-based comparison aiming to evaluate the energy consumption of two crane-bunk systems when loading. The first simulation system considers a forestry crane with a fixed log bunk (forwarder-like crane). The second simulation system takes into account a forestry crane and a rotating log bunk (harwarder-like crane). The analysis presented considers the fundamental mathematics required to analyze the dynamics of forestry cranes and the principles required to plan energy-optimal motions. The simulation results show that energy savings of 43% to 61% can be obtained by determining energy-optimal motions and using a harwarder-like crane architecture.

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  • 2.
    Hellström, Thomas
    et al.
    Umeå University, Faculty of Science and Technology, Department of Computing Science.
    Lärkeryd, Per
    Indexator .
    Nordfjell, Tomas
    Department of Forest Resource Management, Swedish University of Agricultural Sciences.
    Ringdahl, Ola
    Umeå University, Faculty of Science and Technology, Department of Computing Science.
    Autonomous forest vehicles: historic, envisioned, and state-of-the-art2009In: International Journal of Forest Engineering, ISSN 1494-2119, E-ISSN 1913-2220, Vol. 20, no 1, p. 33-38Article in journal (Refereed)
    Abstract [en]

    The feasibility of using autonomous forest vehicles (which can be regarded as logical developments in the ongoing automation of forest machines), the systems that could be applied in them, their potential advantages and their limitations (in the foreseeable future) are considered here. The aims were to analyse: (1) the factors influencing the degree of automation in logging; (2) the technical principles that can be applied to autonomous forest machines, and (3) the feasibility of developing an autonomous path-tracking forest vehicle. A type of vehicle that is believed to have considerable commercial potential is an autonomous forwarder. The degree of automation is influenced by increased productivity, the machine operator as a bottle-neck, cost reduction, and environmental aspects. Technical principles that can be applied to autonomous forest vehicles are satellite navigation, wheel odometry, laser scanner and radar. A new path-tracking algorithm has been developed to reduce deviations from the desired path by utilizing the driver’s steering commands. The presented system has demonstrated both possibilities and difficulties associated with autonomous forest machines. It is in a field study shown that it is quite possible for them to learn and track a path previously demonstrated by an operator with an accuracy of 0.1m on flat ground and also to detect and avoid unexpected obstacles. Although the forest machine safely avoids obstacles, the study shows that further research in the field of obstacle avoidance is needed to optimize performance and ensure safe operation in a real forest environment.

  • 3.
    Jundén, Linus
    et al.
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Bergström, Dan
    Sveriges lantbruksuniversitet.
    Servin, Martin
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Bergsten, Urban
    Sveriges lantbruksuniversitet.
    Simulation of boom-corridor thinning using a double-crane system and different levels of automation2013In: International Journal of Forest Engineering, ISSN 1494-2119, E-ISSN 1913-2220, Vol. 24, no 1, p. 16-23Article in journal (Refereed)
    Abstract [en]

    This study evaluates the productivity of a harvester equipped with a double crane system for thinning with continuous felling and accumulation of whole small-diameter trees for bioenergy at different levels of automation. The simulations were performed using a discrete event simulation tool that has been developed recently and is specifically designed for simulations in forestry, incorporating spatial awareness of the simulated world. The study shows that introducing boom-corridor thinning with a semi-automatic double-crane system can significantly increase the productivity compared to conventional thinning and harvesting. For the specific harvester model used in this study, the modification that yielded the biggest productivity increase was automating the release and placement of the harvested trees. Studies on the effects of implementing automation for other forest machine operations could be analyzed using a similar approach.

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  • 4.
    Lundbäck, Mikael
    et al.
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Häggström, Carola
    Department of Forest Biomaterials and Technology, Swedish University of Agricultural Sciences, Umeå, Sweden.
    Fjeld, Dag
    Department of Forest Biomaterials and Technology, Swedish University of Agricultural Sciences, Umeå, Sweden.
    Nordfjell, Tomas
    Department of Forest Biomaterials and Technology, Swedish University of Agricultural Sciences, Umeå, Sweden.
    New configurations of the tele-extraction concept2023In: International Journal of Forest Engineering, ISSN 1494-2119, E-ISSN 1913-2220, Vol. 34, no 3, p. 397-407Article in journal (Refereed)
    Abstract [en]

    Within cut-to-length forwarding, a theoretical semi-autonomous teleoperation concept called tele-extraction, with automation of crane work and teleoperation of driving, was modeled and simulated. Both configurations modeled had greater potential for cost reduction than a previously studied alternative where the driving was automated, and crane work was teleoperated. Teledrive with teleoperated driving empty, driving loaded, and driving between log piles while loading, showed a reduced cost of 10% for five operators on ten forwarders, whereas teledrive with both loading and driving while loading automated showed a reduced cost of 18% at four operators. In both configurations, the lowest cost was reached at about 10% lower productivity compared to standard forwarding. Increased extraction distance had a negative impact on potential for cost reduction since the driving was teleoperated while terminal activities were autonomous.

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  • 5.
    Stenlund, Tobias
    et al.
    Umeå University, Faculty of Medicine, Department of Community Medicine and Rehabilitation, Section of Physiotherapy.
    Lundström, Ronnie
    Umeå University, Faculty of Medicine, Department of Radiation Sciences, Radiation Physics.
    Lindroos, Ola
    Rehn, Börje
    Umeå University, Faculty of Medicine, Department of Community Medicine and Rehabilitation, Section of Physiotherapy.
    Öhberg, Fredrik
    Umeå University, Faculty of Medicine, Department of Radiation Sciences, Radiation Physics.
    Seated postural loads caused by shock-type whole-body vibration when driving over obstacles2020In: International Journal of Forest Engineering, ISSN 1494-2119, E-ISSN 1913-2220, Vol. 31, no 3, p. 184-191Article in journal (Refereed)
    Abstract [en]

    Operators of mobile machines within forestry work long hours in seated postures while being exposed to whole-body vibration (WBV) that is associated with pain in the lower back and neck. Still, little is known about the contribution from postural loads. In this study postural loads and shock-type WBV exposure on drivers operating a forwarder during terrain-like conditions was measured and quantified using inertial measurement units (IMUs). Five male drivers drove a forwarder repeatedly over standardized steel obstacles using a predefined speed and posture followed by driving over natural obstacles along a terrain course using a self-selected speed and posture. IMUs were affixed along the spine, on the back of the head of the driver and on the seat to detect orientation, velocity, and acceleration. The result shows that the methodology for measuring WBV and postural load with IMUs is feasible. Postural loads, expressed as range of motions (ROMs), when driving over a single standardized obstacle at a speed of 3.3 km/h were up to 21 degrees in the neck segments. Increasing vehicle speed and size of obstacles increased postural loads. The terrain course resulted in higher ROMs in all body segments compared to a standardized obstacle, a difference in sideway seat acceleration but no differences regarding angular velocities of the head. Mechanical shocks at the seat were prevalent but the action limit value was exceeded only for one driver. Postural loads remained small during all conditions indicating that the spine can remain stable during exposure to shock-type WBV of this nature.

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