Effects of Boom-Tip Control and a Rotating Cabin on Loading Efficiency of a Forwarder: A Pilot Study

Climate change and associated heat waves and droughts are causing enormous amounts of damaged wood in Central Europe. To face these challenges, mechanized timber harvesting systems consisting of single-grip-harvesters and forwarders are commonly employed due to their high productivity and work safety. Despite the advantages of these work systems, the operation of advanced forestry machines requires lengthy training and entails high levels of mental strain for machine operators. In recent years, operator assistance systems have been installed in forest machines with the intention of reducing mental workload of machine operators, thereby improving productivity. However, knowledge of the actual effect of operator assistance systems on productivity is still lacking. The present case study surveyed the effect of two recently released operator assitance features, Intelligent Boom Control (»IBC«) and a rotating cabin (»RC«), on productivity during loading cycles, by means of a time study. Therefore, IBC and RC were tested in different loading settings using a forwarder, John Deere 1210G. Three loading angles were tested (55°, 90° and 125° azimuthal and counterclockwise to the machine axis) in combination with five loading distances (4 m, 5.5 m, 7 m, 8.5 m, and 10 m distance from the crane pillar). The 15 loading positions were sampled using four variants (I: IBC off RC off, II: RC on IBC off, III: IBC on RC off, IV: IBC on RC on), capturing 10 replications for each position and variant, resulting in 600 loading cycles in total. When the operator was not supported by any system, mean time consumption per loading cycle amounted to 20.6 ± 0.114 sec. The utilization of IBC resulted in a significant reduction in time consumption of 2 seconds per loading cycle. Moreover, further time savings were observed when IBC was engaged in combination with a rotating cabin, leading to a mean time consumption of 17.8 ± 0.114 sec (or 14% improvement) per loading cycle. Although the lowest time consumption was observed when IBC and RC were engaged, the use of RC alone did not show any significant time improvements. Since loading activities occupy approximately 50% of the total cycle time in timber forwarding, potential time savings within this work element are crucial for further improvements of work productivity. This pilot case study quantified the time savings when IBC and RC were engaged during loading in an experimental setting. The results can be used as a basis for further investigations dealing with factors influencing the productivity of highly mechanized timber harvesting systems

Exploring the Use of Harvesters in Large-Diameter Hardwood-Dominated Stands

The use of fully-mechanized operations, normally targeted at coniferous species, has also been on the rise in mixed-species and continuous-cover forests comprised of a strong share of deciduous species. With special form characteristics (complex crowns, large-diameter branches, forks and sweeps, high wood density, etc.), deciduous trees can lead to wide-ranging harvesting productivities, often divergent from those originally derived from coniferous species. Due to the importance and growing interest in mechanizing operations in close-to-nature mixedwood and deciduous stands, obtaining insight on harvesting productivity in large-diameter deciduous trees was of interest. This study located in Bavaria, Germany, monitored four harvesters (two wheeled and two tracked machines) operated in four distinct harvest blocks (case studies), all of which had a high percentage of large-diameter European beech and oak trees. Harvesting productivity and volume recovery was assessed and quantified. Based on the field inventory of European beech and oak trees and continuous time-and-motion study, average harvesting productivity ranged from 29 to 43 m3/PMH0 (productive machine hours without delay), whereas volume recovery fluctuated between 73% and 85% for trees that were completely felled and processed by machines. Because of the rather limited sample size and the variable conditions between case studies, results should only be used as general orientation on the performance of the tested machines and additional research is suggested to further understand the influence of tree form characteristics on impediments to mechanized processing

Optimization potential for perception-oriented appearance classification by simulated sawing of computed tomography-scanned logs of Norway spruce

Wood, as a natural material, has favourable properties in both technical and aesthetic aspects. Due to its inherent variability,production of high-quality sawn timber demands adequate control of log conversion, which is feasible with computedtomography (CT) log scanning. Existing appearance grading rules for sawn timber might not fully reflect people’s visualperception of wood surfaces, and therefore, an alternative, more perception-oriented appearance classification could bebeneficial. An appearance classification of sawn timber based on partial least squares discriminant analysis (PLS-DA) ofknot-pattern variables was developed and tested. Knot-pattern variables derived from images of board faces were used intraining PLS-DA models against an initial classification of the board faces previously established by aid of cluster analysis.Virtual board faces obtained from simulated breakdown of 57 CT-scanned Norway spruce logs were graded according tothe developed classification. Visual assessment of the grading results indicated that the classification was largely consistentwith human perception of board appearance. An initial estimation of the potential to optimize log rotation, based on CTdata, for the established appearance grades was derived from the simulations. Considerable potential to increase the yield ofa desired appearance grade, compared to conventional log positioning, was observed.Validerad; 2015; Nivå 1; 20141111 (olof)</p

Classification of wood surfaces according to visual appearance by multivariate analysis of wood feature data

Its natural aesthetics make wood an attractivematerial for construction and design. However, there is nodetailed understanding of the relationships between humanperception of the appearance and measurable features ofwood surfaces that could be used for controlling sawntimber production. This study investigated whether woodsurfaces can be classified according to their visualappearance on the basis of wood feature measurements.Cluster analysis was used to discover a classification basedon a set of feature pattern variables in a sample of 300softwood floorboards. A finely graded visual appearancesorting provided a reference. Discriminant analysis wasapplied to identify the relevant variables from the tested setand to assess predictability of the classification. The resultsindicated that visual appearance sorting could be approximatedquite well by the variable-based classification afterpregrouping according to board position in the log.Ambivalent results were obtained for group predictionwithin the validation sample. While for boards from somegroups prediction was mostly or entirely correct, boardsfrom other groups were largely misclassified. An effect ofthe available sample was one of the surmised causes,making repetition of the analysis based on a larger sample adesirable focus of further research.Validerad; 2015; Nivå 2; 20140609 (olof)</p