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  • 1. Axelsson, B.
    et al.
    Grundberg, Stig
    Grönlund, Anders
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Lateral forces in wood cutting1991In: Proceedings of the Tenth International Wood Machining Seminar : Oktober 21 - 23, 1991 / [ed] Richard L. Lemaster, University of California at Berkeley , 1991Conference paper (Refereed)
  • 2.
    Axelsson, B.O.M.
    et al.
    Luleå tekniska universitet.
    Grundberg, Stig
    Grönlund, Anders
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    The use of gray scale images when evaluating disturbances in cutting force due to changes in wood structure and tool shape1991In: European Journal of Wood and Wood Products, ISSN 0018-3768, E-ISSN 1436-736X, Vol. 49, no 12Article in journal (Refereed)
    Abstract [en]

    A method is presented for studying the effect of momentary disturbances due to variations in wood structure on the cutting force near the cutting edge. Force and density measurements are converted to a gray scale image. This method is very effective as regards the evaluation of experimental tests

  • 3. Chiorescu, Sorin
    et al.
    Grundberg, Stig
    The influence of missing bark on measurements performed with a 3D log scanner2001In: Forest products journal, ISSN 0015-7473, Vol. 51, no 8, p. 78-86Article in journal (Refereed)
    Abstract [en]

    Nowadays the sawmill industry is in possession of sophisticated measurement equipment, which is the key to the successful running of the wood transformation process. New technologies such as three-dimensional (3D) scanners are becoming more and more common in Swedish sawmills. These scanners are used for sorting sawlogs according to different criteria such as diameter, length, or quality. They also perform the automatic scaling of the sawlogs that is the basis for estimating volume. Both scaling and sorting are done on bark, i.e., before debarking the logs. Specific functions for the double bark thickness are used to estimate the diameter under bark of the logs. However, these functions do not take into account the eventual missing/damaged bark from the surface of the logs. The errors caused by this lack of precision negatively affect the quality of both scaling and sorting procedures. In this study, with the aid of a simulation technique and field tests, questions regarding the size of these errors and how missing bark affects the measurement procedure when using a 3D log scanner are tackled. Finally, a new system for bark deduction is proposed, implemented, and evaluated in a Swedish sawmill. The results show that paying more attention to missing bark when scaling and sorting sawlogs can considerably increase the accuracy of these operations, thus leading to improvements in the forestry-wood chain.

  • 4.
    Ekevad, Mats
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Salin, Jarl-Gunnar
    Grundberg, Stig
    Nyström, Jan
    Grönlund, Anders
    Modelling of adequate pretwist for obtaining straight timber2006In: Wood Material Science & Engineering, ISSN 1748-0272, E-ISSN 1748-0280, Vol. 1, no 2, p. 76-84Article in journal (Refereed)
    Abstract [en]

    Wood in general and wooden studs in particular are often distorted owing to uneven shrinkage during the drying process in the sawmill. Twist is often the most detrimental of all types of distortion, and it is caused by spiral grain in combination with variations in moisture content. For sawmills, the objective is to produce dried, straight boards, and one method of dealing with boards with excessive spiral grain is to sort them out and then dry them in a pretwisted position to obtain straight boards after drying. A model using the finite element (FE) method for the simulation of drying twist distortions was first calibrated against laboratory experiments in which boards were dried with and without restraints and pretwists. After the calibration, the FE results were compared with industrial test results for boards that were dried without restraints or with restraints with zero pretwist, i.e. straight restraints. The FE model used an elastic-ideally plastic material model to obtain permanent deformations. The calibration was to set the yield stresses so that there was a good match between FE results and results from the laboratory experiments. The comparison between the industrial test results and the FE results showed that the FE model is capable of realistic simulations of drying boards with and without restraints and presumably also pretwists

  • 5. Grundberg, Stig
    An X-ray LogScanner: a tool for control of the sawmill process1999Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    Wood is a biological material with great variability. Every piece of wood is a unique individual. The great challenge in the wood products manufacturing process has always been to select pieces of wood with properties that fulfil the product requirements. This will be even more important in the future as customers increasingly demand sawn products with special properties regarding dimension, moisture content, wrap and last, but not least, biological or aesthetic features. To be albe to fulfil these requirements, the right logs have to be selected for a certain product before the sawing process. This means that an accurate tool that can measure external and internal features is needed. The main objective of this work was to develop and evaluate algorithms for nondestructive measurement of external and internal properties in sawlogs with the aid of a bidirectional X-ray LogScanner. The LogScanner outlines and the LogScanner signals were simulated using CT (computer tomography) images from the Swedish Pine (Pinus sylvestris) Stem Bank and the European Spruce (Picea abies) Stem Bank. With the aid of data from the stem bank databases, the simulated scanner signals, the saw simulation program virtual SawMill (vSM), and statistical analysis programs, new control algorithms were developed and evaluated. The studies show that an X-ray LogScanner with two X-ray sources has a great potential to become a powerful tool for control of the sawmill process. The most important conclusions of work presented in this thesis were that: - X-ray based technology is a suitable technique for nondestructive measurement of internal features in green sawlogs. - CT scanning is a powerful research tool for measurement and visualisation of different log properties. - Parameterisation is an efficient method for reduction of the amount of data from a CT scanner. - It is very efficient to use data from a “Stem Bank data-base” based on CT scanning for simulation, analysis and development of the sawing process and different measurement technologies. - An X-ray LogScanner with two X-ray sources can measure log features such as diameter under bark, species, log type, knot structure, rotational position of knots, density, heartwood content, annual ring width and predict strength and grade of sawn boards.

  • 6. Grundberg, Stig
    Scanning for internal defects in logs1994Licentiate thesis, comprehensive summary (Other academic)
  • 7. Grundberg, Stig
    et al.
    Axelsson, Bengt
    Grönlund, Anders
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Verktygsförslitning: mätmetodik - inverkande faktorer1987Report (Other academic)
  • 8. Grundberg, Stig
    et al.
    Fredriksson, Johan
    Oja, Johan
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Andersson, Carola
    Förbättrade metoder vid användning av 3D-mätramar2001Report (Other academic)
  • 9. Grundberg, Stig
    et al.
    Grönlund, Anders
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Feature extraction with the aid of an X-ray log scanner1998In: Proceedings from the 3rd International Seminar/Workshop on Scanning Technology and Image Processing on Wood: Skelleftea, Sweden, Aug. 17 - 19, 1998 / [ed] Owe Lindgren; Anders Grönlund; Olle Hagman, Luleå: Luleå tekniska universitet, 1998Conference paper (Refereed)
  • 10. Grundberg, Stig
    et al.
    Grönlund, Anders
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Log scanning: extraction of knot geometry in CT-volumes1992In: Proceedings from the Seminar/Workshop on Scanning Technology and Image Processing on Wood, Skellefteå, Sweden, Aug. 30 - Sept. 1, 1992, Skellefteå, 1992Conference paper (Refereed)
  • 11. Grundberg, Stig
    et al.
    Grönlund, Anders
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Methods for reducing data when scanning for internal log defects1991In: Proceedings: 4th International Conference on Scanning Technology in the Wood Industry, San Francisco, Calif: Forest Industries , 1991Conference paper (Refereed)
  • 12. Grundberg, Stig
    et al.
    Grönlund, Anders
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Simulated grading of logs with an X-ray Log Scanner: Grading accuracy compared with manual grading1997In: Scandinavian Journal of Forest Research, ISSN 0282-7581, E-ISSN 1651-1891, Vol. 12, no 1, p. 70-76Article in journal (Refereed)
  • 13. Grundberg, Stig
    et al.
    Grönlund, Anders
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    The Development of a Log-Scanner for Scots Pine1995In: Proceedings from the 2nd International Seminar/Work­shop on Scanning Technology and Image Processing on Wood, Luleå: Högskolan i Luleå , 1995, p. 39-50Conference paper (Refereed)
  • 14. Grundberg, Stig
    et al.
    Grönlund, Anders
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Grönlund, Ulla
    The Swedish stem bank: a database for different silvicultural and wood properties1995Report (Other academic)
  • 15. Grundberg, Stig
    et al.
    Grönlund, Anders
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Lindgren, Owe
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Noggrannhet vid detektering av stockars inre kvalitet: avrapportering av steg 11989Report (Other academic)
  • 16. Grundberg, Stig
    et al.
    Grönlund, Anders
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Oja, Johan
    Israelsson, M.
    Log models reconstructed from X-ray LogScanner signal1999In: Connection between silviculture and wood quality through modelling approaches and simulation softwares: third workshop : La Londe-Les-Maures, France, 1999 : proceedings / [ed] Gérard Nepveu, Nancy: INRA Editions, 1999Conference paper (Refereed)
  • 17. Grundberg, Stig
    et al.
    Hagman, Olle
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Measuring active wood fracture surfaces1993In: European Journal of Wood and Wood Products, ISSN 0018-3768, E-ISSN 1436-736X, Vol. 51, no 1, p. 49-54Article in journal (Refereed)
    Abstract [en]

    This report describes a measurement method, based on image processing, for calculating the proportion of active wood fractures in a sheet of particle board that has been pulled apart. This method gives an indirect measurement of the effectiveness of the glue in a particle board. The basic procedure is to separate different surfaces on both sides of the tensile fracture. The separation of the glue covered surfaces from wood surfaces has been enhanced by a development process. The separated surfaces for each side, represented in the form of a binary image, are added, and a proportion of the surface with coinciding wood surfaces represents the proportion of wood fractures. The error analysis covers the randomly obtained coinciding surfaces.

  • 18. Grundberg, Stig
    et al.
    Hagman, Olle
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Multivariate image analysis methods to classify features on scots pine: evaluation of a multisensor approach1993In: Scan Pro: 5th International Conference on Scanning Technology & Process Control for the Wood Products Industry : Atlanta GA USA Renaissance Hotel, October 25-27, 1993 : conference proceedings / [ed] Ryszard Szymani, San Francisco: Miller Freeman , 1993Conference paper (Refereed)
  • 19. Grundberg, Stig
    et al.
    Hagman, Olle
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Rese- och konferensrapport: USA 19891990Report (Other academic)
  • 20. Grundberg, Stig
    et al.
    Hagman, Olle
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Utveckling av mätmetod för beräkning av andel träbrott i spånskiva1991Report (Other academic)
  • 21. Grundberg, Stig
    et al.
    Lindgren, Owe
    Grönlund, Anders
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    The development of an X-ray based scanner for log grading at full protection speed1996In: Proceedings / 10th International Symposium on Nondestructive Testing of Wood: Lausanne, Switzerland, August 26-27-28, 1996 / [ed] J.L. Sandoz, Lausanne: Swiss Federal Institute of Technology , 1996Conference paper (Refereed)
  • 22. Grundberg, Stig
    et al.
    Oja, Johan
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Grönlund, Anders
    Detecting knots in logs using a simulated X-ray cone-beam scanner2004In: Fourth workshop "Connection between forest resources and wood quality: modelling approaches and simulation software" : Harrison Hot Springs, British Columbia, Canada, September 8 - 15, 2002 ; proceedings / [ed] Gerard Nepveu, International Union of Forestry Research Organisations , 2004Conference paper (Other academic)
  • 23.
    Grönlund, Anders
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Björklund, L.
    Grundberg, Stig
    Berggren, G.
    Manual för furustambank1995Report (Other academic)
  • 24.
    Grönlund, Anders
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Grundberg, Stig
    The accuracy of knot models: influence on the simulated recovery1999In: Connection between silviculture and wood quality through modelling approaches and simulation softwares: third workshop : La Londe-Les-Maures, France, 1999 : proceedings / [ed] Gérard Nepveu, Nancy: INRA Editions, 1999Conference paper (Refereed)
  • 25.
    Grönlund, Anders
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Grundberg, Stig
    Oja, Johan
    Stem bank database: a tool for analysis in the forestry wood chain2004In: The forestry woodchain: Quantifying and forcasting quality from forestry to end product / [ed] Jenny Claridge; Tom Randle, Forest Research, UK , 2004Conference paper (Refereed)
  • 26.
    Grönlund, Anders
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Grundberg, Stig
    Oja, Johan
    Nyström, Jan
    Scanning techniques as tools for integration in the wood conversion chain: some industrial applications2005In: Broad spectrum utilisation of wood: proceedings of the COST Action E 44 Conference : June 14th - 15th 2005, Vienna, Austria / [ed] Alfred Teischinger, Wien: Institutes für Holzforschung, Universität für Bodenkultur Wien , 2005Conference paper (Refereed)
    Abstract [en]

    The market makes lot of different demands on sawn wood products. There are requirements regarding strength, straightness, durability, aesthetic appearance, etc. Most of these demands can be fulfilled by the inherent properties of the trees in the forest. The challenge is to utilize the wood properties to fulfil the market demands in an efficient way. The raw material has to be selected so every customer gets the right piece of wood with the required properties. In order to achieve this, the raw material has to be characterized with different scanning techniques in several steps before and during the breakdown process. In this presentation some examples and experiences from industrially implemented scanning techniques will be described. We can today, after some years of R&D efforts, see how X-ray LogScanners are implemented in the industry. So far they are used for measurement of diameter under bark, internal knot structure, annual ring width, heartwood content and commodity grades. The full potential of this technique is, however, not being fully utilized yet. Equipment for measurement of spiral grain on logs and sawn wood has also been implemented industrially. It has been proven that with the aid of this equipment boards that will twist during drying can be sorted out and treated separately, thus enabling production of straighter timber. The third type of equipment that will be presented is a heartwood scanner. With this scanner, sawmills select Scots pine planks with high heartwood content that are suitable for applications where improved durability is required. These examples show that scanning technology is a key factor for a successful integration between market and forest.

  • 27.
    Grönlund, Anders
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Oja, Johan
    Grundberg, Stig
    Nyström, Jan
    Ekevad, Mats
    Process control based on measurement of spiral grain and heartwood content2007In: Proceeding of 18th International Wood Machining Seminar: IWMS 18, 2007Conference paper (Refereed)
  • 28.
    Hagman, Olle
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Grundberg, Stig
    Wang, Xingli
    NTI Norway.
    Sorting pulpwood by X-ray scanning1997In: 1997 International mechanical pulping conference, Swedish association of pulp and papers engineers , 1997Conference paper (Other academic)
  • 29. Hagman, Olle
    et al.
    Grönlund, Anders
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Grundberg, Stig
    Accuracy of manual grading: some Swedish experiences1995In: Caring for the Forest: research in a changing world: congress report : IUFRO XX World Congress, 6-12 August 1995, Tampere, Finland / [ed] Eeva Korpilahti; Heli Mikkelä; Tommi Salonen, 1995Conference paper (Refereed)
  • 30.
    Lindberg, Henrik
    et al.
    Luleå tekniska universitet.
    Lindberg, L.
    Lindgren, Owe
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Grundberg, Stig
    Mätning av trädensitet och fuktinnehåll i trä: Kalibrering av datortomograf1990Report (Other academic)
  • 31. Nyström, Jan
    et al.
    Grundberg, Stig
    Automatic measurement of spiral grain and its impact on twist after drying2003In: IWSS 5: Proceedings / Fifth International conference on image processing and scanning of wood, March 23 to 26, 2003, Bad Waltersdorf, Austria, Europe, 2003, p. 5-12Conference paper (Other academic)
  • 32.
    Nyström, Jan
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Grundberg, Stig
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Industrial measurement of spiral grain on debarked sawlogs and prediction of twist on centre planks after drying2007In: Modelling the Wood Chain: Forestry - Wood Industry - Wood Products Markets / [ed] Joris Van Acker; Arto Usenius, Ghent: Ghent University , 2007, p. 87-93Conference paper (Refereed)
    Abstract [en]

    Spiral grain occurs naturally more or less in all trees. Instead of running parallel to the pith, the grain runs spiralled around the trunk like a helix. Since wood is an orthotropic material with higher shrinkage perpendicular to than parallel with the grain, the tree will twist when dried, and so will a plank or board cut from it. The tracheid effect utilizes the light-conducting properties of the softwood tracheids to measure the direction of spiral grain. A small laser point was projected on the wood surface. The light transmitted in the wood and scattered back forms an elliptic shape extended in the direction of the fibres. The ellipse of light was registered with a CMOS camera and the orientation of the ellipse's major axis was computed by image processing in real time. A camera system for measuring spiral grain on the debarked surface of a log was installed at a sawmill. In normal production, centre planks of Norway spruce were marked with colour in six different groups according to the size and direction of spiral grain measured by the camera system. All marked planks were manually measured for twist after drying. Measurements on 843 pieces show a coefficient of determination of 0.76 between spiral grain under bark and twist after drying.

  • 33.
    Oja, Johan
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Fredriksson, Johan
    Grundberg, Stig
    Berg, Per
    Automatic grading of sawlogs: industrial experiences from x-ray scanning and optical 3D scanning2003In: IWSS 5: Proceedings / Fifth International conference om image processing and scanning of wood, March 23 to 26, 2003, Bad Waltersdorf, Austria, Europe, 2003, p. 107-114Conference paper (Other academic)
  • 34.
    Oja, Johan
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Grundberg, Stig
    Industrial methods of measuring heartwood in logs and sawn wood2004Conference paper (Other academic)
  • 35.
    Oja, Johan
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Grundberg, Stig
    Fredriksson, Johan
    Råvarustyrning med LogScanner2000Report (Other academic)
  • 36.
    Oja, Johan
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Grundberg, Stig
    Fredriksson, Johan
    Swedish Institute for Wood Technology Research.
    Berg, Per
    Swedish Institute for Wood Technology Research.
    Automatic grading of sawlogs: a comparison between X-ray scanning, optical three-dimensional scanning and combinations of both methods2004In: Scandinavian Journal of Forest Research, ISSN 0282-7581, E-ISSN 1651-1891, Vol. 191, no 1, p. 89-95Article in journal (Refereed)
    Abstract [en]

    As sawmills become increasingly efficient, the importance of focusing on value recovery becomes obvious. To maximize value recovery, sawmills require the ability to sort logs according to quality. This study compares four different combinations of three-dimensional (3D) and X-ray scanning that can be used to grade logs automatically. The study was based on 135 Scots pine (Pinus sylvestris L.) logs that had been scanned with both a 3D scanner and an X-ray scanner with two X-ray sources. The percentage of boards with correct grade sawn from automatically graded logs varied from 57% when using only 3D scanning to 66% when using a combination of 3D scanning and X-ray scanning in two directions. The highest possible result, with ideal log grading, was 81%. The result also shows that the combination of a 3D scanner and one X-ray direction results in higher accuracy than a scanner based on two X-ray directions

  • 37. Oja, Johan
    et al.
    Grundberg, Stig
    Grönlund, Anders
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Measuring the outer shape of Pinus sylvestris saw logs with an x-ray LogScanner1998In: Scandinavian Journal of Forest Research, ISSN 0282-7581, E-ISSN 1651-1891, Vol. 13, no 3, p. 340-347Article in journal (Refereed)
    Abstract [en]

    The accuracy of measuring the outer shape of Scots pine (Pinus sylvestris L.) saw logs with an X-ray LogScanner has been compared with the accuracy of using a 2-axis optical scanner, a 3-axis optical scanner and an ideal 3-D optical scanner. The different scanners were simulated using computed tomography (CT) data from the Swedish Stem Bank. The outer shape of 60 saw logs was measured every third centimeter. The error attributable to bark when using optical scanners was simulated separately. The results from the simulations showed that when measuring the outer shape on bark, the X-ray LogScanner facilitated measurement of the minimum shadow diameter with the same accuracy as with a 3-D optical scanner. The results also showed that the potential of combining the X-ray LogScanner with a 3-D optical scanner should be investigated

  • 38. Oja, Johan
    et al.
    Grundberg, Stig
    Grönlund, Anders
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Predicting the stiffness of sawn products by X-ray scanning of Norway spruce saw logs2001In: Scandinavian Journal of Forest Research, ISSN 0282-7581, E-ISSN 1651-1891, Vol. 16, no 1, p. 88-96Article in journal (Refereed)
    Abstract [en]

    The aim of the study was to investigate the possibility of strength grading Norway spruce [Picea abies (L.) Karst.] saw logs on the basis of simulated X-ray LogScanner measurements and to evaluate the potential accuracy of X-ray LogScanner measurements of green heartwood density and percentage of heartwood. The study was based on 272 logs for strength grading and 29 logs for measurements of green heartwood density and percentage of heartwood. The logs were scanned using computed tomography (CT). After sawing, the modulus of elasticity (MOE) of the centre boards was measured using a strength-grading machine. The CT images were used for simulations of an X-ray LogScanner, resulting in simulated measurements of different variables such as diameter, taper, percentage of heartwood, density and density variations. Multivariate models for prediction of MOE were then calibrated using partial least squares (PLS) regression. The MOE of a log was defined as the mean value of the MOE of the two centre boards. The study showed that the simulated X-ray LogScanner measured the percentage of heartwood and green heartwood density with relatively high accuracy (R2 = 0.94 and R2 = 0.73, respectively, after removing two outliers) and that these and other variables measured by the simulated X-ray LogScanner could be used to predict the stiffness of the centre boards. These predictions were used to sort the logs according to the predicted MOE. When sorting out 50% of the logs (''high-strength'' logs), the percentage of C30 boards increased from 73% (all logs in the study) to 100% (only ''high-strength'' logs). The rest of the logs could then be divided into two groups, one of them with 100% C24 and C30 boards.

  • 39. Oja, Johan
    et al.
    Grundberg, Stig
    Grönlund, Anders
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Predicting the strength of sawn products by X-ray scanning of logs: a preliminary study2000In: Wood and Fiber Science, ISSN 0735-6161, Vol. 32, no 2, p. 203-208Article in journal (Refereed)
    Abstract [en]

    The aim of the study was to investigate the possibility of predicting the strength of centerboards from Norway spruce (Picea abies (L.) Karst.) saw logs, based on simulated X-ray LogScanner measurements. The study was based on eight logs. The logs were scanned using computed tomography (CT), four centerboards were sawn from each log, and the bending stiffness (MOE) and strength (MOR) of the boards were measured. The CT-images were used for simulations of the industrial X-ray LogScanner, resulting in simulated measurements of knot volume and the green density of heartwood. Finally, multivariate models were calibrated using Partial Least Squares (PLS) regression. These models predict bending strength and stiffness based on the variables measured by the simulated X-ray LogScanner. Both bending strength and modulus of elasticity were defined as the mean value of the four boards from each log. The results were very promising, with strong models for prediction of both MOR (R2 = 0.73) and MOE (R2 = 0.94) mean values for all four boards from each log. The results indicate that the X-ray LogScanner can be used for the sorting of saw logs according to strength and stiffness. The next step should be to repeat the study on a larger sample of material.

  • 40. Oja, Johan
    et al.
    Grundberg, Stig
    Grönlund, Anders
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Simulated Control of Sawing Position Based on X-ray Logscanner Measurements1998In: Proceedings from the 3rd International Seminar/Workshop on Scanning Technology and Image Processing on Wood: Skelleftea, Sweden, Aug. 17 - 19, 1998 / [ed] Owe Lindgren; Anders Grönlund; Olle Hagman, Luleå: Luleå tekniska universitet, 1998Conference paper (Refereed)
  • 41.
    Oja, Johan
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Kallsner, Bo
    Grundberg, Stig
    Predicting the strength of sawn wood products: a comparison between x-ray scanning of logs and machine strength grading of lumber2005In: Forest products journal, ISSN 0015-7473, Vol. 55, no 9, p. 55-60Article in journal (Refereed)
    Abstract [en]

    For a long time, process improvements in sawmills have focused on high productivity measured in volume per hour and volume recovery. As sawmills become increasingly efficient, the importance of focusing on value recovery becomes obvious. In order to maximize value recovery, sawmills need the ability to sort logs according to properties such as strength. The aim of this study was to compare the results of predicting the strength of center boards based on x-ray scanning of logs with the results obtained by machine strength grading using a bending machine. The study was based on 131 Norway spruce (Picea abies (L.) Karst.) sawlogs that were scanned with an x-ray LogScanner and then sawn into boards. The bending stiffness of the center boards was tested using a strength-grading machine, and the bending strength was tested according to EN 408. Models for prediction of bending strength based on machine strength grading and x-ray LogScanner measurements were calibrated using partial least squares regression. The study showed that the x-ray LogScanner (r2 = 0.44) and machine strength grading (r2 = 0.43) had similar accuracy in predicting bending strength. The combination of both methods resulted in significantly higher accuracy (r2 = 0.56). The root mean square error (RMSE) was 8.5 MPa for the bending machine, 8.4 MPa for the x-ray LogScanner, and 7.4 MPa for the combination of both methods. Consequently, the combination is an interesting alternative. Future studies should include a larger number of boards and focus on the effect of log carriers and on finding the reasons behind outliers

  • 42.
    Oja, Johan
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Källsner, B.
    Grundberg, Stig
    Predicting the strength of sawn products by industrial X-ray scanning of Norway spruce saw logs2001In: Proceedings / ScanTech 2001, the Ninth International Conference on Scanning Technology and Process Optimization for the Wood Industry : November 4 - 6, 2001, Holiday Inn Seattle International Airport, Seattle, Washington, U.S.A.: ScanTech 2001, the Ninth International Conference on Scanning Technology and Process Optimization for the Wood Industry : November 4 - 6, 2001, Holiday Inn Seattle International Airport, Seattle, Washington, U.S.A, Berkeley, Calif: Wood machining institute , 2001Conference paper (Refereed)
  • 43. Oja, Johan
    et al.
    Wallbäcks, Lars
    AssiDomän.
    Grundberg, Stig
    Hägerdal, Erik
    AssiDomän.
    Grönlund, Anders
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Automatic grading of Scots pine (Pinus sylvestris L.) sawlogs using an industrial X-ray log scanner2003In: Computers and Electronics in Agriculture, ISSN 0168-1699, E-ISSN 1872-7107, Vol. 41, no 1-3, p. 63-75Article in journal (Refereed)
    Abstract [en]

    The successful running of a sawmill is dependent on its ability to achieve the highest possible value recovery from the sawlogs, i.e. to optimize the use of the raw material. Such optimization requires information about the properties of every log. One method of measuring these properties is to use an X-ray log scanner. The objective was to determine the accuracy when grading Scots pine (Pinus sylvestris L.) sawlogs using an industrial scanner known as the X-ray LogScanner. The study was based on 150 Scots pine sawlogs from a sawmill in northern Sweden. All logs were scanned in the LogScanner at a speed of 125 m/min. The X-ray images were analyzed on-line with measures of different properties as a result (e.g. density and density variations). The logs were then sawn with a normal sawing pattern (50 × 125 mm) and the logs were graded depending on the result from the manual grading of the center boards. Finally, partial least squares (PLS) regression was used to calibrate statistical models that predict the log grade based on the properties measured by the X-ray LogScanner. The study showed that 77-83% of the logs were correctly sorted when using the scanner to sort logs into three groups according to the predicted grade of the center boards. After sawing the sorted logs, 67% of the boards had the correct grade. When scanning the same logs repeatedly, the relative standard deviation of the predicted grade was 12-20%. The study also showed that it is possible to sort out 10 and 16%, respectively, of the material into two groups with high quality logs, without changing the grade distribution of the rest of the material to any great extent

1 - 43 of 43
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