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  • 1.
    Axelsson, Ann
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Fredriksson, Magnus
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Potential for increasing volume yield by reducing planing allowance2017In: Wood Material Science & Engineering, ISSN 1748-0272, E-ISSN 1748-0280, Vol. 12, no 5, p. 301-306Article in journal (Refereed)
    Abstract [en]

    About half the volume of sawlogs ends up as sawn and planed timber. The rest is lost due to drying shrinkage or is turned into by products. As the raw material is a major expense for a sawmill, it is important to reduce waste.

    To investigate how much the volume yield in the production of sawn and planed timber could be increased by reducing the target dimensions in the sawing stage in a sawmill, two groups of sawn timber were planed under similar conditions. One group consisted of sawn Scots pine timber with a large variation in twist. The other group consisted of sawn Norway spruce timber planed under different pressure settings. Using X-ray images, the minimum dimension for avoiding planer misses was calculated for each board, to find the smallest green target dimension. This was compared to actual measured dimensions.

    It was found that most sawn timber had unnecessarily large dimensions, and it was also found that a reduction in the target dimensions could increase the volume yield for sawn and planed timber by more than 3 percentage points. Boards with large twist would however need a higher planing allowance. The effect of the planer pressure setting was negligible.

  • 2.
    Axelsson, Ann
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Fredriksson, Magnus
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Potential for waste reduction when planing wood2014Conference paper (Refereed)
  • 3.
    Berglund, Anders
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Broman, Olof
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Grönlund, Anders
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Fredriksson, Magnus
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Improved log rotation using information from a computed tomography scanner2013In: Computers and Electronics in Agriculture, ISSN 0168-1699, E-ISSN 1872-7107, Vol. 90, p. 152-158Article in journal (Refereed)
    Abstract [en]

    The development of an industrial computed tomography scanner for the sawmilling industry raises the question of how to find a production strategy that uses a computed tomography scanner in the sawmill production line to its full potential. This study was focused on a Scandinavian sawmill processing Scots pine (Pinus sylvestris) and Norway spruce (Picea abies). The potential value increase when allowing an alternative log rotation other than the horns down position was investigated using a log breakdown simulation. The resulting data was analysed with respect to the size of the log rotational step, an introduced rotational error of the sawing machine and different price differences between the quality grades. It was also of interest to define the outer log properties that characterise the logs sawn for the greatest profit return close to the horns down position compared to logs sawn for a greater profit return in a different log rotation. Such characteristics can be used to reduce the number of degrees of freedom in an optimisation and consider instead other parameters, such as positioning and sawing pattern. Other defects such as pitch pockets, splits and rot are also of interest. The results shows that there is a potential value increase when applying the log rotation that maximises the value for each log instead of processing all logs in the horns down position. However, the potential value increase depends on the rotational error of the used sawing machine and the price differences between the quality grades. The log properties that differ between logs sawn for the greatest profit return close to the horns down position compared to a different log rotation are the bow height and the log taper. Unfortunately, predictability of log rotation for greatest profit return based on the outer properties of logs is poor. It is not possible to differentiate logs which would be sawn for the greatest profit return close to the horns down position from those where a different log rotation results in the greatest profit return, based only on their outer properties.

  • 4. Berglund, Anders
    et al.
    Fredriksson, Magnus
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Broman, Olof
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Grönlund, Anders
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Project: CT-Pro2012Other (Other (popular science, discussion, etc.))
    Abstract [sv]

    Projektet är finansierat av WoodWisdom-Net, VINNOVA, Fachagentur Nachwachsende Rohstoffe e. V. och medverkande företag. Syftet med projektet är att visa att det är möjligt att extrahera ut viktig och detaljerad information från en timmerstock med hjälp av en speciellt utvecklad röntgenskanner och sedan utnyttja denna information i produktionsstategier för att öka värdet i den träindustiella värdekedjan.

  • 5.
    Broman, Olof
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics.
    Fredriksson, Magnus
    Luleå University of Technology, Department of Engineering Sciences and Mathematics.
    Effect of Raw Material on Yield in a Furniture Production Process2015In: Proceedings of the 22nd International Wood Machining Seminar, June 14-17, 2015 Qebec City, Canada / [ed] Roger Hernández; Claudia Cáceres, Quebec City: Universite Laval , 2015, p. 311-322Conference paper (Other academic)
    Abstract [en]

    In the process of wood manufacturing, each step affects the material utilization and the cost efficiency. Wood has got high diversity in its inherent features and the different manufacturing steps must be able to handle this. In most end products the proportion of the raw material cost is high. Thus, material utilization and cost efficient processes are of great importance. The overall aim of this project was to study the potential in a manufacturing production process in terms of material utilization efficiency. A production process of finger-jointed furniture components was chosen as a study case. Its chain of production units consists of: a sawmill, a finger-joint plant producing components and finally a furniture company that produce the end product. The aim of this article is to describe the impact of different raw material (log type and board quality) and what wood features affect the total yield of a manufactured product.In total 105 logs of three different types were tested: butt, intermediate and top logs. The logs were sawn with two different sawing patterns, 3X- and 2X-log. The quality of the wood material was measured by aid of 3D-scanning and X-ray (logs), manual grading (boards), and WoodEye (boards/components) and manual inspection of the final products. With a data collection with traceability the quality of the test material was followed through all steps in the manufacturing chain.The result show differences between log types in down-grade causes, reject volume and the final yield of accepted products. Different ways of improving the raw material efficiency of the studied chain of operations are also discussed.

  • 6.
    Broman, Olof
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Fredriksson, Magnus
    Luleå University of Technology, Department of Engineering Sciences and Mathematics.
    Wood material features and technical defects that affect the yield in a finger joint production process2011Conference paper (Refereed)
    Abstract [en]

    A cost efficient process is the goal for every production process. In wood manufacturing, each step in the process may affect the material utilization and the cost efficiency. Wood as a material has got high diversity in its inherent features and the different manufacturing steps must be able to handle this. In most end products the proportion of the raw material cost is high. Thus, material utilization and cost efficient processes are of great importance. The overall aim of the project was to study the potential and problems in manufacturing production processes in terms of material utilization efficiency. A production process of finger jointed bed sides for IKEA was chosen as a study case and its chain of production units are; a sawmill for plank production, a finger joint company producing components and finally a furniture company that produce the end product. The aim of this article is to describe the impact of different raw material and what wood and technical defects that affect the total yield of a manufactured product. In total 177 logs of three different log types were tested; butt logs, intermediate logs and fresh knot logs. The quality of the wood material was detected and measured by aid of 3D-scanning and X-ray (logs), FinScan (planks), and WoodEye (planks/components) and manual inspection of the final products. With a full traceability data collection the quality of the test material was followed through all steps in the manufacturing chain. The result show differences between log types in down-grade causes, reject volume and the final yield of accepted products. Also, the test material showed high levels of reject with non-biological background which suggest the need of technical improvements in the finger joint and the furniture manufacturing process. The intermediate log group showed overall the best result.

  • 7.
    Broman, Olof
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Fredriksson, Magnus
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Wood material features and technical defects that affect yield in a finger joint production process2012In: Wood Material Science & Engineering, ISSN 1748-0272, E-ISSN 1748-0280, Vol. 7, no 4, p. 167-175Article in journal (Refereed)
    Abstract [en]

    A cost efficient process is the goal of all production, and each manufacturing step affects the material utilization and cost efficiency. There is high diversity in the inherent features of wood, and manufacturing steps must be able to handle this. The overall objective was to study the potential and problems in manufacturing production processes in terms of material utilization efficiency. The production of finger jointed bed sides was chosen as a study case, where the chain of production units are the sawmill, finger joint plant and furniture plant. This article describes the impact of raw material and wood defects that could affect the total yield. A total of 177 logs of three types were tested: butt, intermediate and fresh knot logs. The test material quality was detected and measured through all steps in the manufacturing chain. The results show differences between log types in down-grade causes, reject volume and final yield. Also, the test material showed high levels of defective components with process-related defects, which suggested the need for technical improvement in the manufacturing process. The intermediate log group showed the overall best result.

  • 8.
    Cool, Julie
    et al.
    University of British Columbia.
    Fredriksson, Magnus
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Avramidis, Stavros
    University of British Columbia.
    Automatic knot detection in coarse resolution cone-beam CT images of softwood logs2019In: Forest products journal, ISSN 0015-7473Article in journal (Refereed)
  • 9.
    Cool, Julie
    et al.
    University of British Columbia.
    Fredriksson, Magnus
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Avramidis, Stavros
    University of British Columbia.
    Knot detection in coarse resolution CT images of logs2017In: International Wood Machining Seminar (IWMS-23), 2017Conference paper (Refereed)
    Abstract [en]

    The use of X-ray computed tomography (CT) scanning of logs in sawmill is becoming a reality in the last few years, usually with rather costly and complex machines resembling medical scanners. However, a scanning solution has been developed that is less costly and more robust, and therefore more suited for sawmill needs. The rather coarse data from this machine has not been fully evaluated regarding possibilities to detect internal features such as knots. In this study, a knot detection algorithm developed for medical scanners was applied to images from a coarse resolution scanner, from four different logs of various species, and with different image resolution. The objective was to see if it was possible to detect knots automatically in the images. If so, the aim was to calculate the knot detection rate and the accuracy of detected knot size and position. These numbers were calculated compared to manually measured reference knots. This resulted in a knot detection rate of about 53 % overall, and a well detected knot position, but poorly detected knot size. It is possible to observe a certain difference between species and reconstruction resolution, however the material is too small to draw any definite conclusions. As a preliminary study, it provides input for further investigation on knot detection in coarse resolution X-ray CT images. Future work involves scanning more logs to get more data, and to pinpoint the resolution needed for accurate knot detection using the current algorithm.

  • 10.
    Cool, Julie
    et al.
    University of British Columbia.
    Fredriksson, Magnus
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Stephen, James D
    Queen’s University.
    Mabee, Warren E
    Queen’s University.
    Avramidis, Stavros
    University of British Columbia.
    Bull, Gary Q
    University of British Columbia.
    An Integrated Forest Products Cluster for Off-Grid Lumber Production Using Biomass CHP in Remote Indigenous Communities2017Conference paper (Refereed)
  • 11.
    Fredriksson, Magnus
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    A simulation tool for the finger jointing of boards2011Conference paper (Refereed)
    Abstract [en]

    Knowledge about how tree properties affect the final product is necessary to utilise each log and tree in the forestry production chain fully. So far, the Swedish Pine Stem Bank (SPSB) has been used extensively for sawing simulation, but not for simulation further down the production process. Hence, it is desirable to model the further processing of sawn timber using the SPSB. In this study, a simulation tool for cross cutting and finger jointing of boards has been developed and tested. The simulation program utilises the SPSB and the results from a sawmill simulation program to simulate a cross-cutting and finger-jointing process. The tool has been tested against an empirical material consisting of defect data from an industrial scanner, used at a producer of finger-jointed furniture products. To illustrate the potential use of the finger-jointing simulation program, two investigations have also been carried out. The first deals with comparing the recovery for finger jointing and cutting of solid boards for different products. The second investigation is an attempt to estimate the impact of process-related defects on the recovery of finger-jointed products. The results show that the simulation tool produces similar results as the real process, and the use of the SPSB provides adequate predictions of the real system’s behaviour. The first of the investigations shows that finger jointing generally has a better recovery than cutting of solid boards, but for short products, the latter might be a viable option. The second investigation suggests that process-related defects reduce recovery by up to 5% units in the finger-joint process studied. Thus, there is future potential for using the finger-jointing simulation tool to investigate production strategies and/or raw material selection in the forestry production chain.

  • 12.
    Fredriksson, Magnus
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Computer simulation in the forestry-wood chain2012Licentiate thesis, comprehensive summary (Other academic)
    Abstract [en]

    The forestry-wood chain today involves many actors, and the decisions taken in the process of making trees into finished products are so many that the effect of each individual decision is difficult to assess, especially if the natural variation of the input material is considered.This means that a simulation approach to the forestry-wood chain is suitable, since it makes it possible to evaluate the effects of decisions in a short timeframe, while the input material can be kept constant for different production setups. The long term aim is to connect tree and log properties to the quality of a final product through simulation, depending on the various operations involved in making the product.A part of this is realized through this thesis. It is shown that a simulation model of a cross-cutting and finger-jointing process is representative of a real process. The model is used to evaluate an adaptive strategy for setting the safety zone size between finger-joints and sound knots, a strategy which improves recovery in a finger-jointing operation by 3 %.Another issue addressed in this thesis is that of simulation input data. The sawing simulation tool used to a large extent in research today, Saw2003, usesthe Swedish Pine Stem Bank as input data. This is a very well-documented datasource, and computed tomography (CT) scanning of the stem bank logs allows wood features such as knots to be represented in a realistic way in Saw2003. There are limitations to the stem bank, however, mostly due to the fact that CT scanning is a time consuming process, which means that the amount of scanned logs is relatively small. In this thesis, it is shown that it is possible to use a small amount of log features for determining the knot structure in a log, which opens up possibilities for using industrial data from two-directional X-ray scanners. This would increase the amount of logs to be used as simulation input data.A second set of data used for simulation was also collected in a study of a production process, where the wood raw material was followed from the logyard through all production operations of making finger-jointed furniture components. Each individual piece of wood was traced through the operations, thus ensuring a link between the properties of logs and those of the finished product. This second data set was collected by grey-scale camera scanning of boards prior to cross-cutting and finger-jointing, and was used in the development of cross-cutting and finger-jointing simulation. It contains information on non-clearwood features of the board surfaces such as knots, cracks, and pitch pockets.It can be concluded from this thesis that it is possible to increase bothfunctionality and the amount of input data in the simulation of the forestry-wood chain, and by doing so production strategies and decisions can be evaluated. Wood quality discussions may be simplified by being able to assess the effects on the production process of decisions being made. Future work involves adding more functionality to the simulation environment as well as evaluating the methods proposed in this thesis industrially. The long term vision is to be able to integrate the forestry-wood chain from log to finished product in one simulation model.

  • 13.
    Fredriksson, Magnus
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Handling positioning errors when optimizing sawing of Scots pine and Norway spruce logs using CT scanning2016In: Journal of Wood Science, ISSN 1435-0211, E-ISSN 1611-4663, Vol. 62, no 5, p. 400-406Article in journal (Refereed)
    Abstract [en]

    Since computed tomography (CT) X-ray scanning is becoming a reality in sawmills, different studies have been made to establish how well the sawing position of a log can be optimized using CT data. It is also known that positioning errors have an adverse effect on optimization, since the optimization methods used are rather sensitive to positioning errors. To mitigate the effect of positioning errors, a method is proposed in this article that filters results produced by sawing simulation, using a Gaussian filter of a size according to the positioning error. Using these filtered values for optimization, it is possible to retain two percent extra value of the sawn timber, when rotation and offset errors are present, compared to a regular optimization method. A method more robust to positioning errors is more useful in practice, since positioning errors of various magnitudes are always present in sawmills. The main contribution of this paper is, therefore, an optimization method that reduces the effect of positioning errors.

  • 14.
    Fredriksson, Magnus
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Log Positioning by Aid of Computed Tomography Data and Sawing Simulation2013Conference paper (Refereed)
  • 15.
    Fredriksson, Magnus
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Log Sawing Position Optimization using Computed Tomography Scanning2014In: Wood Material Science & Engineering, ISSN 1748-0272, E-ISSN 1748-0280, Vol. 9, no 2, p. 110-119Article in journal (Refereed)
    Abstract [en]

    When disjoining a log, several factors affect the value of the sawn timber. There are log features, such as outer shape, knots, rot, and so on. There are also sawing parameters, such as sawing pattern, log position, and so on. If full information about log features is available, sawing parameters can be adapted in order to maximize product value in sawmills. This is soon possible, since computed tomography (CT) scanners for the sawmill industry are being realized. This study aimed at investigating how CT data can be used to choose rotational position, parallel displacement, and skew of sawlogs, to maximize the value of the sawn products. The study was made by sawing simulation of 269 CT scanned logs of Scots pine (Pinus sylvestris L.) and Norway spruce (Picea abies [L.] H. Karst.). The results showed that value recovery could be improved by 13% in average, compared to a sawing position based on log outer shape, and 21% compared to sawing logs centered and horns down. It can be concluded that a CT scanner, used in a sawline to optimize sawing parameters, has a large potential for increasing value recovery and thus profit.

  • 16.
    Fredriksson, Magnus
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Optimizing sawing of boards for furniture production using CT scanning technique2015In: Journal of Wood Science, ISSN 1435-0211, E-ISSN 1611-4663, Vol. 61, no 5, p. 474-480Article in journal (Refereed)
    Abstract [en]

    The inherent variability of wood material together with sub-optimization in production processes means that a lot of potential value is lost. Computed tomography scanning together with simulation models of the production processes could remedy this, and ensure optimization of the entire production process. Therefore, the purpose of this study was to investigate if such methods can be used to optimize the sawing position of logs in a production process including further processing, in this case crosscutting to make a furniture product with strict quality requirements on dead knots. This was done on 47 Scots pine (Pinus sylvestris L.) logs. The results show a potential yield increase of more than 11 % points in the crosscutting operation and more than 4 % points when viewing the process as a whole, compared to sawing the logs horns down and centered

  • 17.
    Fredriksson, Magnus
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Reconstruction of Pinus Sylvestris knots using measurable log features in the Swedish Pine Stem Bank2012In: Scandinavian Journal of Forest Research, ISSN 0282-7581, E-ISSN 1651-1891, Vol. 27, no 5, p. 481-491Article in journal (Refereed)
    Abstract [en]

    The objective of this study was to develop a method for reconstruction of parametrically described whorls and knots from data possible to extract from industrial scanning of logs, using X-ray scanners. The method was conceived using the logs in the Swedish Pine Stem Bank as a foundation, and was based on a few predictor features extracted from these logs; namely whorl volume, distance between whorls and distance between pith and surface. These features were not measured in images but calculated from existing parameterised knots. Simulated test sawing shows that the reconstruction method results in a representative model of the knot structure in the log, when considering the grade distribution of the sawn timber produced by the simulation program. The results of this study could, for instance, be used for improved online quality predictions at sawmills. One step in this direction is to use industrial X-ray data to enlarge the amount of log data available for sawing simulation research. Future work can, therefore, focus on developing a practical application of the results presented here.

  • 18.
    Fredriksson, Magnus
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    The Value of Wood: Production Strategies in the Forestry-Wood Chain Using X-ray Scanning and Computer Simulation2014Doctoral thesis, comprehensive summary (Other academic)
  • 19.
    Fredriksson, Magnus
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Using a Gaussian filter to reduce the effect of positioning errors when optimizing sawing of CT scanned Scots pine and Norway spruce logs2017In: International Wood Machining Seminar (IWMS-23), 2017Conference paper (Refereed)
    Abstract [en]

    Computed tomography (CT) scanning of logs is being introduced in sawmills, so there is reason to study how log positioning can be controlled using information from CT. However, positioning errors affect this positioning optimization in a negative way. To reduce this effect, a method was developed using sawing simulation, where logs were sawn in a large number of positions, varying rotation and centering. This resulted in three-dimensional surfaces, with the sawn timber value, rotation and centering on the axes. The surfaces were filtered with a Gaussian filter using a distribution corresponding to that of the positioning error. The filtered values were used for optimization, choosing the global maximum. This resulted in a value recovery that was about two percent higher compared to a simpler optimization without filtering, for a normally distributed rotational error of 5 – 15° standard deviation and a ditto centering error of 3.5 – 10.5 mm standard deviation. This was tested using sawing simulation, using the optimal log position for the two methods, with an added positioning error. Furthermore, the robust method has been tested on a smaller number of rotational positions, starting from horns down, to reduce the number of necessary calculations. The result of this was that at least ± 60 ° in the rotational direction should be evaluated for the robust method to result in a higher recovery than the simpler optimization. The robust method was better than sawing horns down and centered, no matter the positioning error, using only 65 evaluated positions per log.

  • 20.
    Fredriksson, Magnus
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Berglund, Anders
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Broman, Olof
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Validating a crosscutting simulation program based on computed tomography scanning of logs2015In: European Journal of Wood and Wood Products, ISSN 0018-3768, E-ISSN 1436-736X, Vol. 73, no 2, p. 143-150Article in journal (Refereed)
    Abstract [en]

    Wood scanners and software for calculating crosscutting positions have been used in the wood industry for some years now. The scanners are used to detect biological and geometrical deviations on the sawn timber, which makes it possible to remove undesired defects using crosscut saws. Yield calculations for crosscutting have not been investigated to the same extent as sawing yield calculations for primary breakdown of logs, especially if the whole chain from log to end product is considered. The objective of this study was to validate the result of a computer program developed for simulating crosscutting of boards. The crosscut simulations were performed with respect to knot characteristics on Scots pine (Pinus sylvestris L.) board surfaces. Validating a crosscutting simulation program would mean that it can be used to investigate how raw material and customization of quality rules affect the yield in a wood production chain from log to crosscut end product. The validation showed that crosscutting yield for boards could be predicted with a root mean square error of 13 percentage points, and the technique can be used to identify unsuitable logs for a certain product at an early stage of production.

  • 21.
    Fredriksson, Magnus
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Bomark, Peter
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Broman, Olof
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Grönlund, Anders
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    A trapeze edging method for cross laminated timber panel production2015In: Proceedings of the 22nd International Wood Machining Seminar / [ed] Roger Hernández; Claudia Cáceres, Quebec city, Kanada: Universite Laval , 2015, p. 323-332Conference paper (Refereed)
  • 22.
    Fredriksson, Magnus
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Bomark, Peter
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Broman, Olof
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Grönlund, Anders
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Using Small Diameter Logs for Cross Laminated Timber Production2015In: BioResources, ISSN 1930-2126, E-ISSN 1930-2126, Vol. 10, no 1, p. 1477-1486Article in journal (Refereed)
    Abstract [en]

    Sawing small diameter logs results in lower yield compared to sawing large diameter logs. This is due to geometry; fitting rectangular blocks inside an approximately cylindrical shape is more difficult for small than for large diameters. If small diameter logs were sawn in a way that follows the outer shape, yield would increase. The present study considers whether this can be done by sawing flitches into trapeze shapes. These can be glued together into rectangular products. Cross laminated timber (CLT) products are suitable for this. The study was based on 4,860 softwood logs that where scanned, and the scanning data was used for sawing simulation. The log top diameters ranged from 92 to 434 mm. The volume yield of CLT production using trapeze edging was compared to cant sawing of boards. The trapeze edging and CLT production process improved yield compared to cant sawing by 17.4 percent units, for logs of a top diameter smaller than 185 mm. For all logs, the yield decreased using the trapeze edging method. To conclude, a trapeze edging method shows promise in terms of increasing volume yield for small diameter logs, if boards can be properly taken care of in a CLT production process

  • 23.
    Fredriksson, Magnus
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Broman, Olof
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Persson, Fredrik
    SP Trä.
    Axelsson, Ann
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Ah Shenga, Pedro
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Rotational Position of Curved Saw Logs and Warp of the Sawn Timber2014In: Wood Material Science & Engineering, ISSN 1748-0272, E-ISSN 1748-0280, Vol. 9, no 1, p. 31-39Article in journal (Refereed)
    Abstract [en]

    With the development of scanning technology in sawmills, it is possible to optimise log rotational position when sawing. However, choosing a different rotational position than horns down might be detrimental for the board shape after drying, especially for curved logs. Thus, there is a need to investigate at what level of log curve it is possible to freely rotate logs without causing board warp. This study was carried out through a test sawing that was conducted at a sawmill situated in the middle of Sweden. The tests were made on 177 Norway spruce logs, with varying amount of curve. Half of the logs were sawn in the horns-down position, half were sawn rotated perpendicular to horns down. Log shape and warp of the dried boards were measured. The results indicated a relationship between board spring, log curve and choice of rotational position. Furthermore, board bow was related to log curve but not rotational position. It can be concluded that for straight logs, with a bow height of less than 15 mm, an unconventional rotational position does not cause excess spring in the boards. Bow and twist are not affected by the rotational position at all.

  • 24.
    Fredriksson, Magnus
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Brännström, Mattias
    Technical solutions to increase competitiveness of cross-laminated timber from the Nordic countries: an overview2018Conference paper (Refereed)
  • 25.
    Fredriksson, Magnus
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Cool, Julie
    University of British Columbia.
    Avramidis, Stavros
    University of British Columbia.
    Knot detection in computed tomography images of partially dried Jack pine (Pinus banksiana Lamb.) and white spruce (Picea glauca (Moench) Voss) logs2017In: International Wood Machining Seminar (IWMS-23), 2017Conference paper (Refereed)
    Abstract [en]

    X-ray computed tomography (CT) of logs means possibilities for optimizing breakdown in sawmills. This depends on accurate detection of knots to assess internal quality. However, as logs are stored in the log yard they dry to a certain extent, and this drying affects the density variation in the log, and therefore the X-ray images. For this reason, it is hypothetically difficult to detect log features in partially dried logs using X-ray CT. The objective of this research was to investigate the effect of drying on knot detection in Jack pine (Pinus banksiana Lamb.) and white spruce (Picea glauca (Moench) Voss) logs from New Brunswick, Canada. An automatic knot detection algorithm was compared to manual measurements for this purpose, and the results show that knot detection was clearly affected by partial drying. Because dried heartwood and sapwood have similar densities, the algorithm had difficulties detecting the heartwood-sapwood border. Based on how well the heartwood-sapwood border was detected, it was statistically possible to sort logs into two groups: 1) Low knot detection rate, and 2) High knot detection rate. In that way, a decision can be made whether or not to trust the knot models obtained from CT scanning. Therefore, logs that are partially dried out and fall in the low knot detection rate should be handled cautiously because the optimization results based on CT knot detection cannot be fully trusted. Sawing of these logs could be optimized using only their outer shape, ignoring internal quality. Similarly, only logs having a regular heartwood shape should be used when scanning logs for research purposes or in databases of CT scanned logs. Finally, a larger knot detection rate was obtained for Jack pine. This could have been facilitated by the fact that pine trees usually have larger but less numerous knots than spruce trees.

  • 26.
    Fredriksson, Magnus
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Cool, Julie
    University of British Columbia, Vancouver .
    Duchesne, Isabelle
    Natural Resources Canada, Canadian Wood Fibre Centre, Québec, Canada.
    Belley, Denis
    Ministère des Forêts, de la Faune et des Parcs, Québec, Canada.
    Knot detection in computed tomography images of partially dried Jack pine (Pinus banksiana Lamb.) and white spruce (Picea glauca (Moench) Voss) logs from a Nelder type plantation2017In: Canadian Journal of Forest Research, ISSN 0045-5067, E-ISSN 1208-6037, Vol. 47, no 7, p. 910-915Article in journal (Refereed)
    Abstract [en]

    X-ray computed tomography (CT) of logs means possibilities for optimizing breakdown in sawmills. This depends on accurate detection of knots to assess internal quality. However, as logs are stored they dry to some extent, and this drying affects the density variation in the log, and therefore the X-ray images. For this reason it is hypothetically difficult to detect log features in partially dried logs using X-ray CT. This paper investigates the effect of improper heartwood-sapwood border detection, possibly due to partial drying, on knot detection in jack pine (Pinus banksiana Lamb.) and white spruce (Picea glauca (Moench) Voss) logs from New Brunswick, Canada. An automatic knot detection algorithm was compared to manual reference knot measurements, and the results showed that knot detection was affected by detected heartwood shape. It was also shown that logs can be sorted into two groups based on how well the heartwood-sapwood border is detected, to separate logs with a high knot detection rate from those with a low detection rate. In that way, a decision can be made whether or not to trust the knot models obtained from CT scanning. This can potentially aid both sawmills and researchers working with log models based on CT.

  • 27.
    Fredriksson, Magnus
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Cool, Julie
    Univ British Columbia, Dept Wood Sci, Fac Forestry, Vancouver, BC, Canada.
    Stavros, Avramidis
    Univ British Columbia, Dept Wood Sci, Fac Forestry, Vancouver, BC, Canada. Forest Prod Soc, Peachtree Corners, GA USA.
    Automatic Knot Detection in Coarse-Resolution Cone-Beam Computed Tomography Images of Softwood Logs2019In: Forest products journal, ISSN 0015-7473, Vol. 69, no 3, p. 185-187Article in journal (Refereed)
    Abstract [en]

    X-ray computed tomography (CT) scanning of sawmill logs is associated with costly and complex machines. An alternative scanning solution was developed, but its data have not been evaluated regarding detection of internal features. In this exploratory study, a knot detection algorithm was applied to images of four logs to evaluate its performance in terms of knot position and size. The results were a detection rate of 67 percent, accurate position, and inaccurate size. Although the sample size was small, it was concluded that automatic knot detection in coarse resolution CT images of softwoods is feasible, albeit for knots of sufficient size.

  • 28.
    Fredriksson, Magnus
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Grönlund, Anders
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Fingerjointing simulation: first step to complete integration2011In: F D M Asia, ISSN 0218-7663, no Oct, p. 34-37Article in journal (Other (popular science, discussion, etc.))
  • 29.
    Fredriksson, Magnus
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Johansson, Erik
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Berglund, Anders
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Rotating Pinus sylvestris sawlogs by projecting knots from computed tomography images onto a plane2014In: BioResources, ISSN 1930-2126, E-ISSN 1930-2126, Vol. 9, no 1, p. 816-827Article in journal (Refereed)
  • 30.
    Fredriksson, Magnus
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Skog, Johan
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Reconstruction of knots from simulated discrete x-ray images of Pinus Sylvestris logs2012Conference paper (Refereed)
    Abstract [en]

    For many years it has been of interest to be able to predict the properties of sawn wood products from tree features. X-ray technology has made it possible to measure internal as well as external features of saw logs, and to use these features for predicting log quality. However, data available for simulation of the sawing process and prediction of sawn timber quality has, until now, been limited to logs scanned using computed tomography.The objective of this study is to develop a method for reconstruction of parametrically described whorls and knots from industrial scanning of Scots pine (Pinus sylvestris L.) logs, using discrete Xray images. The method is designed using the logs in the Swedish pine stem bank (SPSB) as data basis, and is based on a few predictor features extracted from these logs, namely whorl volume, distance between whorls, and distance between pith and surface. These features are measured in simulated discrete X-ray images of the logs in the SPSB, and virtual models of the whorls and knots are created, using a feature- and knowledge based model. Virtual logs are then composed using the reconstructed knots within the original shape of the logs. Simulated test sawing of the virtual logs shows that the reconstruction method results in a representative model of the knot structure in the log, when considering the grade distribution of the sawn timber produced by the simulation program. The results of this study can for instance be used for improved online quality predictions at sawmills. One step in this direction is to use industrial X-ray data to enlarge the amount of log data available for sawing simulation research. Future work should focus on developing practical applications of the results presented here.

  • 31.
    Fredriksson, Magnus
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Öhman, Micael
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Song, Haitong
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Determination of crosscutting safety zone for finger-jointed Pinus sylvestris furniture components2012In: Forest products journal, ISSN 0015-7473, Vol. 62, no 2, p. 107-113Article in journal (Refereed)
    Abstract [en]

    A common problem with finger-jointed wooden furniture components is chipping in the finger joints due to fiber deviations around sound knots. To avoid this, a fixed size safety zone between defects and crosscuts is used, but can lead to an excess of material cut away in the crosscutting operation. To reduce chippings in finger joints while maximizing recovery, an adaptive strategy was developed for setting the safety zone size between sound knots and finger joints in Scots pine (Pinus sylvestris L.) furniture components. The strategy was based upon modeling the risk of chipping the finger joint depending on the knot measurement. The model was used in an adaptive strategy in order to minimize the expected loss due to cutting away material around knots, compared with the cost of rejecting components in later stages due to chipped finger joints. Thus, each knot was assigned a unique safety zone. The strategy was tested using computer simulation of the finger-jointing process, and a sensitivity analysis was performed in order to quantify the effect of variations in the input data. The results show that the adaptive strategy improves recovery by at least 3 percent in the process of turning lumber into finger-jointed furniture components. It is very robust toward variations in knot size measurements (e.g., by scanning equipment), but less robust toward variations in crosscutting precision.

  • 32.
    Johansson, Erik
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Johansson, Dennis
    SP Technical Research Institute of Sweden, Skellefteå.
    Skog, Johan
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Fredriksson, Magnus
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Automated knot detection for high speed computed tomography on Pinus sylvestris L. and Picea abies (L.) Karst. using ellipse fitting in concentric surfaces2013In: Computers and Electronics in Agriculture, ISSN 0168-1699, E-ISSN 1872-7107, Vol. 96, p. 238-245Article in journal (Refereed)
    Abstract [en]

    High speed industrial computed tomography (CT) scanning of sawlogs is new to the sawmill industry and therefore there are no properly evaluated algorithms for detecting knots in such images. This article presents an algorithm that detects knots in CT images of logs by segmenting the knots with variable thresholds on cylindrical shells of the CT images. The knots are fitted to ellipses and matched between several cylindrical shells. Parameterized knots are constructed using regression models from the matched knot ellipses. The algorithm was tested on a variety of Scandinavian Scots pine (Pinus sylvestris L.) and Norway spruce (Picea abies (L.) Karst.) with a knot detection rate of 88–94% and generating about 1% falsely detected knots.

  • 33.
    Lövf, Eva
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Axelsson, Ann
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Fredriksson, Magnus
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Studentlyftet - en bro till universitetsstudier i matematik: Slutrapport pedagogiskt utvecklingsprojekt LTU2014Report (Other academic)
    Abstract [sv]

    Vid ingenjörsprogrammen vid LTU har det noterats att det finns brister i matematikkunskaperna hos nyantagna studenter. För att undersöka detta har vanliga problem kartlagts med hjälp av intervjuer med lärare samt en enkätundersökning bland studenter. Både lärare och studenter pekar på bristande kunskaper inom främst algebra.För att åtgärda de påpekade kunskapsluckorna har även studenternas studievanor undersöks dels genom den tidigare nämnda enkätundersökningen samt genom intervjuer med studenter. Ett återkommande tema är att många studenter föredrar att räkna i grupp, men även att det är viktigt med tillgång till föreläsningar, både i form av en klassisk föreläsningssituation och som inspelade filmer.Med den inhämtade kunskapen om problemområden och studievanor togs en prototyp till ett diagnosverktyg fram i Maple TA med ledtrådar i form av videoklipp inom det aktuella området. Diagnosverktyget testades av en frivillig grupp studenter med övervägande positivt mottagande vilket visar att det finns stor potential för fortsatt arbete.

  • 34.
    Lövf, Eva
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Axelsson, Ann
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Fredriksson, Magnus
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Studentlyftet: en bro till självständiga universitetsstudier i matematik2014In: NU 2014: Umeå 8-10 oktober : abstracts, Umeå: Umeå universitet. Pedagogiska institutionen , 2014, p. 56-Conference paper (Refereed)
  • 35.
    Markström, Emilia
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Bystedt, Anders
    Department of Sustainable Built Environment, SP Swedish Technical Research Institute.
    Fredriksson, Magnus
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Sandberg, Dick
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Drivers and barriers for an increased use of bio-based buildning materials in Sweden2016In: Proceedings of the 12th meeting of the Northern European Network for Wood Science and Engineering (WSE): Wood science and engineering – a key factor on the transition to Bioeconomy, Riga, September 12-13 2016 / [ed] Andersons B. & Kokorevics A. (Eds.), Riga: Latvian State Institute of Wood Chemistry , 2016, p. 15-21Conference paper (Refereed)
    Abstract [en]

    To limit the climate impact of buildings, low carbon materials such as bio-based materials could be used. This study intends to contribute to the understanding of drivers and barriers for an increased use of bio-based building materials in apartment buildings. For this purpose, semi-structured interviews with Swedish architects, contractors and developers were conducted. The results indicate weak drivers for selecting bio-based materials at present and that the key barriers are insufficient incentives, lack of knowledge and experience, bad examples, issues regarding performance, and construction-related culture and habits. Important future drivers could be green building certificates and other environmental standards and regulations, evidence that the materials keep a certain quality over time, and educational support from municipalities.

  • 36.
    Markström, Emilia
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Bystedt, Anders
    SP Trä.
    Fredriksson, Magnus
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Sandberg, Dick
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Use of bio-based building materials: perceptions of Swedish architects and contractors2016In: New Horizons for the Forest Products Industry.: 70th Forest Products Society International Convention, Madison: Forest Products Society, 2016Conference paper (Refereed)
    Abstract [en]

    This study is intended to contribute to the understanding of the probability that bio-based materials are chosen in residential buildings and to the understanding of the drivers and barriers for an increased use of bio-based building materials. For this purpose, semi-structured interviews were held with Swedish architects and contractors. The results indicate a low probability of selection of bio-based materials in Swedish residential building, mainly due to insufficient incentives, lack of knowledge and experience, bad examples, issues regarding performance and construction-related culture and habit. However, the attitude among contractors has started to change in a more positive direction. Green building certificates, as well as other environmental standards and regulations, were seen as a promising way to increase the use of bio-based materials. Evidence that the materials maintain a certain quality over time was also identified as an important measure to increase the incentives to select bio-based materials.

  • 37.
    Markström, Emillia
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Bystedt, Anders
    SP Swedish Technical Research Institute.
    Fredriksson, Magnus
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Sandberg, Dick
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Perceptions of Swedish architects and contractors for the use of bio-based building materials2016In: Innovative production technologies and increased wood products recycling and reuse / [ed] Eds. Kutnar A., Schwarzkopf M., Burnard M., Sebera V. & Troppová E., Brno: Mendel University in Brno, Czech Republic , 2016, p. 19-20Conference paper (Refereed)
  • 38.
    Olofsson, Linus
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Broman, Olof
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Fredriksson, Magnus
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Skog, Johan
    RISE Bioeconomy, Research Institutes of Sweden.
    Sandberg, Dick
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Customer adapted grading of Scots pine sawn timber: a multivariate method approach2017In: 23rd International wood machining seminar: proceedings : 28. - 31. 5. 2017, Warsaw, Poland / [ed] Zbiec M & Orlowski K, Warsaw: Warsaw university of life sciences , 2017, p. 360-361Conference paper (Refereed)
    Abstract [en]

    At Scandinavian softwood sawmills, the most common system for grading of sawn timber in dry conditions is optical scanning equipment together with a rule-based automatic grading system (RBAG). The procedure to define new grading rules towards a customer with specified requirements is a time-consuming work for sawmills and is rarely implemented in a satisfactory way neither for the customer nor for the sawmill. An important consequence is that sawmills will, in general, not be able to deliver products that utilize the full potential of the quality distribution of the sawn timber produced at the sawmill. Their customers will get products with mismatch in desired and delivered quality grades. Thus, there is a need for a methodology that facilitates time and cost effective grading toward specific customers’ needs. The objective of the study was to further develop and validate a method that complements the RBAG by a holistic-subjective automatic grading (HSAG) approach - using multivariate regression models.In the study, 790 Scots pine boards with cross-section dimensions of 38×150 mm and length between 3.4 m and 5.6 m were manually graded according to the preferences of a large-volume customer, and also scanned and graded by an RBAG system calibrated for the same customer. Multivariate models for prediction of board grade, based on aggregated knot variables obtained from the scanning, were calibrated using partial least squares regression. The results show that prediction of board grades by the multivariate models were more correct than the grading by the RBAG system. The prediction of board grades based on multivariate models resulted in 84% of the boards graded correctly, according to the manual grading, while the corresponding number was 64% for the RBAG system. In a follow up grading test the accuracy of the two systems were 95% and 81%, respectively.

  • 39.
    Olofsson, Linus
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Broman, Olof
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Skog, Johan
    RISE Bioeconomy, Research Institutes of Sweden, Skellefteå, Sweden.
    Fredriksson, Magnus
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Sandberg, Dick
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Multivariate product adapted grading of Scots pine sawn timber for an industrial customer, part 1: Method development2019In: Wood Material Science & Engineering, ISSN 1748-0272, E-ISSN 1748-0280, Vol. 14, no 6, p. 428-436Article in journal (Refereed)
    Abstract [en]

    Rule-based automatic grading (RBAG) of sawn timber is a common type of sorting system used in sawmills, which is intricate to customise for specific customers. This study further develops an automatic grading method to grade sawn timber according to a customer’s resulting product quality. A sawmill’s automatic sorting system used cameras to scan the 308 planks included in the study. Each plank was split at a planing mill into three boards, each planed, milled, and manually graded as desirable or not. The plank grade was correlated by multivariate partial least squares regression to aggregated variables, created from the sorting system’s measurements at the sawmill. Grading models were trained and tested independently using 5-fold cross-validation to evaluate the grading accuracy of the holistic-subjective automatic grading (HSAG), and compared with a resubstitution test. Results showed that using the HSAG method at the sawmill graded on average 74% of planks correctly, while 83% of desirable planks were correctly identified. Results implied that a sawmill sorting station could grade planks according to a customer’s product quality grade with similar accuracy to HSAG conforming with manual grading of standardised sorting classes, even when the customer is processing the planks further.

  • 40.
    Olofsson, Linus
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Broman, Olof
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Skog, Johan
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Fredriksson, Magnus
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Sandberg, Dick
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Multivariate Product Adapted Grading of Scots Pine Sawn Timber for an Industrial Customer, Part 2: Robustness to Disturbances2019In: Wood Material Science & Engineering, ISSN 1748-0272, E-ISSN 1748-0280Article in journal (Refereed)
    Abstract [en]

    Holistic-subjective automatic grading (HSAG) of sawn timber by an industrial customer's product outcome is possible through the use of multivariate partial least squares discriminant analysis (PLS-DA), shown by part one of this two-part study. This second part of the study aimed at testing the robustness to disturbances of such an HSAG system when grading Scots Pine sawn timber partially covered in dust. The set of 308 clean planks from part one of this study, and a set of 310 dusty planks, that by being stored inside a sawmill accumulated a layer of dust, were used. Cameras scanned each plank in a sawmill's automatic sorting system that detected selected feature variables. The planks were then split and processed at a planing mill, and the product grade was correlated to the measured feature variables by partial least squares regression. Prediction models were tested using 5-fold cross-validation in four tests and compared to the reference result of part one of this study. The tests showed that the product adapted HSAG could grade dusty planks with similar or lower grading accuracy compared to grading clean planks. In tests grading dusty planks, the disturbing effect of the dust was difficult to capture through training.

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