Simulated productivity of one- and two-armed tree planting machines

Abstract

Simulated productivity of one-and two-armed tree planting machinesErsson B. T., Jundén L., Bergsten U., Servin M. (2013). Simulated productivity of one-and two-armed tree planting machines. Silva Fennica vol. 47 no. 2 article id 958. 23 p. Highlights• Using discrete-event simulation and detailed terrain and machine models, the productivities of excavator-based one-and two-armed tree planting machines were simulated.• The machines' arms were equipped with one-and two-headed planting devices.• Two planting heads per arm rather than two arms per base machine is better for increasing the productivity of intermittently advancing planting machines on Nordic clearcuts. AbstractTo increase mechanized planting, planting machine productivity must increase in order to improve cost-efficiency. To determine if excavators with two crane arms could potentially help to increase planting machine productivity under Nordic clearcut conditions, we modelled one-armed and semiautomated two-armed excavators with one-and two-headed planting devices. Using a recently developed tool for discrete-event simulation, these machine models then mounded and planted seedlings on terrain models with moraine soil having various frequencies of obstacles (stumps, roots and stones). Compared to if the two heads were mounted pairwise on only one arm, the results showed that productivity did not increase if two planting heads were attached individually to two separate crane arms. But productivity did increase if the planting machine had four planting heads mounted pairwise on two separate arms. However, despite assuming automated mounding and crane motion between planting spots, the two-armed, four-headed model never achieved high enough productivity levels to make it more cost-efficient than one-armed machines. The simulations illustrate that our terrain models generate realistic root architecture and boulder content distributions in moraine soil, while our machine models functionally describe mechanized planting work. Based on our assumptions, we conclude that further development work on two-armed excavator-based planting machines for Nordic clearcut conditions is not warranted. Our simulations reveal that increasing the number of planting heads per crane arm rather than number of crane arms per base machine offers the greatest potential to raise the productivity of intermittently advancing planting machines.

Mechanized Tree Planting in Sweden and Finland: Current State and Key Factors for Future Growth

“…Cost-efficiency is hampered by low productivity, which originates from operator inexperience, among other reasons [12]. The choice of worksites also strongly influences productivity, and it has been reported that the presence of stones, slash, and stumps decreases the planting machines' productivity [13][14][15][16][17]. The size and spatial distribution of worksites also affects cost-competitiveness [18].…”

Simulated productivity of conceptual, multi-headed tree planting devices

“…In essence, this study used the models and discrete-event simulation tool described mainly in Ersson et al (2013) but also in Jundén (2011). Explained below are the additions and improvements made to the models for this specific study, and its experimental design.…”

“…The two-headed M-Planter attaches to an excavator's crane; mounds and then deep-plants seedlings; and has reached productivities exceeding 300 seedlings per productive work hour (pl/PWh, excluding delays) during time studies on clearcuts where stump and slash had been harvested (Laine & Rantala 2013). Ersson et al (2013) reported a theoretical productivity over 400 pl/PWh when the M-Planter was simulated on obstacle-sparse terrain, and this figure was about 60% higher than that of the one-headed Bracke Planter. Nonetheless, follow-ups of practical work with the MPlanter have noted average productivity figures only half as high as the theoretical ones (Rantala & Laine 2010).…”

“…However, most Fennoscandian forest terrain is not obstaclefree. Typical forest/clearcut terrain in southern Sweden, for example, comprises moraine soil with stumps, roots (Ersson et al 2013), surface boulders ) and overlying humus layers (also called O-horizon; Olsson et al 2009). Therefore, for novel planting devices to be realistic, they must also perform satisfactorily on clearcuts with obstacles.…”

Determining boreal clearcut object properties and characteristics for identification purposes

“…Stones, stumps, slash and roots impede e.g. site preparation and mechanized planting (Larsson 2011;Luoranen et al 2011;Ersson et al 2013) whereas some of these objects need to be located efficiently for other purposes than avoidance, e.g. during slash forwarding and stump removal.…”