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  • 1. Berg, Per
    et al.
    Oja, Johan
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Att detektera fibervinkel med 4 kameror på obarkade stockar: Resultat från vinterprov2004Report (Other academic)
  • 2.
    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.
    Oja, Johan
    Grönlund, Anders
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Customer adapted grading of Scots pine sawn timber using a multivariate method2015In: Scandinavian Journal of Forest Research, ISSN 0282-7581, E-ISSN 1651-1891, Vol. 30, no 1, 87-97 p.Article in journal (Refereed)
    Abstract [en]

    To define new grading rules, or to customize the ones in use in a rule-based automatic grading system of boards, is a time-consuming job for a sawmill engineer. This has the effect that changes are rarely made. The objective of this study was to continue the development of a method that replaces the calibration of grading rule settings by a holistic-subjective automatic grading, using multivariate models. The objective was also to investigate if this approach can improve sawmill profitability and at the same time have a satisfied customer. For the study, 323 Scots pine (Pinus sylvestris L.) boards were manually graded according to preferences of an important customer. That is, a customer that regularly purchases significant volumes of sawn timber. This manual grading was seen as reference grading in this work. The same boards were also scanned and graded by a rule-based automatic grading 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, with respect to the manual grading, than the grading by the rule-based automatic grading system. The prediction of board grades based on multivariate models resulted in 76-87% of the boards graded correctly, according to the manual grading, while the corresponding number was 63% for the rule-based automatic grading system.

  • 3.
    Broman, Olof
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Nyström, Jan
    Oja, Johan
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Effektiv produktion av golvprodukter med krav på estetiska egenskaper2007Report (Other academic)
    Abstract [sv]

    Trä används i många tillämpningar där träet är synligt och där råvarans estetiska egenskaper därför är mycket. Exempel på sådana tillämpningar är produkter är golv och paneler. I detta projekt har produktionsprocessen för solida furugolv studerats, det vill säga hela kedjan från sortering av stockar till slutkonsumenters preferenser. Samarbetspartners i detta FoU- projekt har varit SCA -Bollsta sågverk, Norrlands Trä AB, SP Trätek och LTU - Träteknologi, Skellefteå. Syftet med projektet har varit att demonstrera hur man med hjälp av modern marknadsanalys, modern, industriellt implementerad mätteknik och avancerade sorteringsalgoritmer kan effektivisera produktionen av kundanpassade produkter med krav på estetiska egenskaper. Ett delmål var att undersöka alternativa utseendekvaliteter till dagens produktion av golvträ. Den genomgående metoden har varit att mäta och dokumentera råvarans egenskaper genom hela processen från stock till färdig produkt. En lättanvänd interaktiv databas har utvecklats inom ramen för projektet och använts för simulering av alternativa sorteringar av råvara avsedd för golvproduktion. Kopplat till databasen har även ett visualiseringsverktyg utvecklats. Detta gör det möjligt att direkt kunna se resultatet av simuleringarna i form av digitala golvytor. Utöver resultat i form av utvecklad databasgränssnitt, visualiseringsverktyg och verktyg för konsumentudersökningar så har projektet visat på intressanta resultat vad gäller både produktions och marknad. Resultatet av databassimuleringarna visar att man genom att förändra sorteringsstrategin och sortera stockarna baserat på information från en röntgenmätram helt kan undvika utsortering i råsorteringen, minska utsorteringen i justerverket med 25% (från tolv till nio procentenheter) och ändå producera en golvråvara med samma estetiska egenskaper som tidigare. Som ett alternativ till den ursprungliga golvråvaran har även en ny golvråvara definierats. Preferensstudier i både Sverige och Norge visade att konsumenternas tyckte bättre om den nya kvaliteten än den utsprungliga. Samtidigt gjorde denna nya golvråvara det möjligt att helt undvika utsortering i både råsortering och justerverk och samtidigt öka den tillgängliga golvråvaran med 27% (från 30 till 38 procentenheter).

  • 4.
    Broman, Olof
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Nyström, Jan
    Oja, Johan
    Modelling the connection between industrially measured raw material properties and end user preferences: Part 2. Results from preference studies2008In: Connection between Forest Resources and Wood Quality: Modelling Approaches and Simulation Software. IUFRO Working Party 5.01.04 Wood Quality Modelling, June 8. - 14, Koli, Finland / [ed] H. Peltola, 2008Conference paper (Other academic)
  • 5.
    Broman, Olof
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Wixe, David
    LTU Skellefteå, Träteknologi.
    Grönlund, Anders
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Oja, Johan
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Råvarustyrning för materialeffektiv produktion av limfog: En studie utförd vid Norrfog AB2011Report (Other academic)
    Abstract [sv]

    Norrfog AB i Malå tillverkar limfogskivor i olika kvaliteter, bland annat till gör-det-själv- (GDS)-limfog, möbelfog och IKEAs hyllkoncept Ivar. Då Norrfog planerar att öka sin producerade volym av limfog ökar behovet av en effektiv styrning av rätt råvara till rätt slutprodukt. Samtidigt stiger råvarupriserna och det blir allt viktigare att maximera volyms- och värdeutbytet. Vid tidpunkten för studien: Norrfog AB köper klena furustockar och försorterar stockarna i diameterklasser med hjälp av en 2D-mätram. Ingen sortering sker på stocktyp och därmed blandas rotstockar, svartkviststockar och friskkviststockar. Stockarna sågas med en 2ex postning till plankor som efter torkning kapas upp till komponentlängder som därefter klyvs till färdiga lameller för limfogsproduktion. Huvudsyftet med detta projekt var att undersöka möjligheterna att styra rätt kvalitet av timmer till rätt slutprodukt; Ivarhyllan, GDS-limfog och möbelfog samt för- och nackdelar med att införa ett alternativt sågsätt – genomsågning. Inom ramen för studien fanns följande forsknings- och utvecklingsfrågor: •Stocklängdens betydelse för volymutbytet av limfog? •Stocktypens betydelse för kvaliteten på producerad limfog? •Går det att hitta rätt typ av stockar till en specifik produkt redan vid timmerplanen med hjälp av befintlig 2D-mätram och förbättrar 3D eller röntgen-skanning denna klassificering av stockar? •Finns det ett motstånd till fingerskarv bland konsumenter och vad anses vara ett önskvärt utseende på en träyta av limfog? Studien visar att den stocktyp som gav den bästa kvaliteten var friskkviststockarna, men även de stockar som sorterades som svartkvistiga visade sig innehålla mestadels friska kvistar i de aktuella timmerdimensionerna. Ett tydligt resultat var att rotstockar innehöll den lägsta kvaliteten med för många och/eller för stora svarta kvistar och det visade sig vara lämpligt att om möjligt sortera bort dessa stockar för att såga dessa separat till produkter med lägre krav på kvalitet. Sorteringsalgoritmer för olika mättekniker för timmer speciellt anpassade för att maximera utbytet kvalitet 1 i den färdiga limfogen testades. Med befintlig 2D-mätram sorterades 81 % av rotstockarna bort och med röntgenmätning ökade andelen bortsorterade rotstockar till 98 %. Ett viktigt resultat var att genomsågning gav i snitt 13 % högre volymutbyte än 2ex-sågning och att korta stockar gav ökat volymutbyte jämfört med fullängdsstockar. En separat undersökning angående skivornas utseende visar att fingerskarvade limfogskivor är något konsumenten kan tänka sig, så länge färgskiftningarna mellan lamellerna är små. Stora färgskiftningar och små svarta kvistar var det som respondenterna rankade som minst tilltalande för alla skivor oavsett fingerskarv eller inte.

  • 6. Brännström, Mattias
    et al.
    Manninen, Janne
    Stora Enso AB, Porvoo.
    Oja, Johan
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Predicting the strength of sawn wood by tracheid laser scattering2008In: BioResources, ISSN 1930-2126, E-ISSN 1930-2126, Vol. 3, no 2, 437-451 p.Article in journal (Refereed)
    Abstract [en]

    An industrial laser light scattering scanner, designed to detect the spiral grain angle of logs by the light scattering along the grain, was used on two large samples of Norway spruce (Picea abies (var. Karst)) in various sawn dimensions (approximately 750 pieces). Additional measurements were made by other techniques, such as X-ray scanning, resonance frequency measurement, and various manual measurements. The strength properties of the boards were measured by destructive testing in four-point bending according to European standard. Multivariate methods (PLS) were used to model the relationship between the bending strength of the board (MOR) and the measurements. Based only on the output from the simple tracheid scattering equipment, a model for MOR achieved an R² exceeding 0.3. Combinations with average density or outer shape parameters from log scanning resulted in R² 0.4 and 0.3 respectively, although these parameters alone only accounted for R² 0.2. The results can be used to increase the understanding of strength in wood and in an improved industrial strength-grading process.

  • 7. Brännström, Mattias
    et al.
    Manninen, Janne
    Oja, Johan
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Tracheid laser scattering: a simple tool for a rough strength estimation2006Conference paper (Other academic)
  • 8. Brännström, Mattias
    et al.
    Oja, Johan
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Grönlund, Anders
    Predicting board strength by X-ray scanning of logs: the impact of different measurement concepts2007In: Scandinavian Journal of Forest Research, ISSN 0282-7581, E-ISSN 1651-1891, Vol. 22, no 1, 60-70 p.Article in journal (Refereed)
    Abstract [en]

    The objective of this study was to compare the individual board strength predictions from an X-ray log scanner by using either two or four X-ray directions. The benefit of applying traceability between log and board was also studied. In total, 119 Norway spruce [Picea abies (L.) Karst.] sawlogs were scanned by an X-ray log scanner at the log sorting station of a sawmill and sawn into two centre pieces per log. Individual board traceability was enabled by following the rotational position of the log in the scanner and at the succeeding sawing. All boards were graded by a commercial strength grading machine before destructive testing was done. The resulting data were used to derive variables for building multivariate partial least squares strength prediction models. In the modelling a hierarchical modelling approach was used, where annual ring width, dry density and elasticity were also modelled. For all concepts studied the models' fit was similar. Only minor benefits could be found when using four directions and traceability compared with two directions and no traceability. One conclusion is that the result for traceability, from four directions in particular, is more sensitive for the interior knot reconstruction result. The strength prediction was on the same R2 level as for the strength grading machine

  • 9. Flodin, Jens
    et al.
    Oja, Johan
    Grönlund, Anders
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Fingerprint traceability of logs using the outer shape and the tracheid effect2008In: Forest products journal, ISSN 0015-7473, Vol. 58, no 4, 21-27 p.Article in journal (Refereed)
    Abstract [en]

    Traceability in the sawmilling industry is a concept that, among other benefits, could be used to more effectively control and pinpoint errors in the production process. The fingerprint approach is a traceability concept that in earlier studies has shown good potential for tracing logs between the log sorting station and the saw intake. In these studies, bark has been identified as a large source of measurement inaccuracy. This study was set out to investigate whether the fingerprint recognition rate could be improved when compensating for bark with traditional bark functions or a new automatic bark assessment based on the tracheid effect. The results show that the fingerprint recognition rate can be improved by using more sophisticated bark compensation. Compared to no bark compensation, improvements can be made by using the existing bark functions, and even further improvements can be made by using automatic bark assessment based on the tracheid effect. The results further show that the butt-end reducer between the log sorting station and the saw intake has a very negative effect on the fingerprint recognition rate, but that significant improvements in the recognition rate can be achieved by excluding the section of the log's butt end that is affected by the butt-end reduction.

  • 10. Flodin, Jens
    et al.
    Oja, Johan
    Grönlund, Anders
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Fingerprint traceability of sawn products using industrial measurement systems for x-ray log scanning and sawn timber surface scanning2008In: Forest products journal, ISSN 0015-7473, Vol. 58, no 11, 100-105 p.Article in journal (Refereed)
    Abstract [en]

    Traceability in the sawmilling industry is a concept that, for example, could be used to more effectively control the production process and the utilization of raw material. The fingerprint approach is a traceability concept that rests on the principle that every piece of wood is a unique individual with unique properties and therefore can be identified and separated if a sufficient number of these properties are measured accurately enough. This study was made with the aim of making the fingerprint connection between logs and the center yield sawn from those logs using length and knot information. The material used was Scots pine logs from six different diameter groups sawn with a two-ex sawing pattern into six different dimensions of center-yield planks. The data from the logs were collected at the log sorting station by an industrial one-directional x-ray log scanner in combination with a 3-D optical scanner. The data from the sawn center yield were collected by an industrial cross-fed surface scanning system situated in the sawmill's green sorting station. The results show that over 95 percent of all planks could be matched to the right log. This gives a high potential for further development and realization of fingerprint tracing between the log sorting and the green sorting station into a practical application for process control and process improvement.

  • 11. Flodin, Jens
    et al.
    Oja, Johan
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Grönlund, Anders
    Fingerprint traceability of sawn products using x-ray logscanning and sawn timber surface scanning2007In: Quality control for wood and wood products: COST Action E 53 the first conference, October 15th/17th, 2007, Warsaw, Poland / [ed] Marek Grześkiewicz, Warsaw: Warsaw University of Life Sciences , 2007, 39-42 p.Conference paper (Refereed)
    Abstract [en]

    Traceability in the sawmilling industry is a concept that could be used to more effectively control the production processand the utilization of the raw material. The fingerprint approach is a traceability concept that rests on the idea that everypiece of wood is a unique individual with unique properties and hence can be identified and separated if a sufficientnumber of these properties are measured accurately enough. This study was hosted by a sawmill in northern Sweden andwas aimed at making the fingerprint connection between logs and the center yield sawn from those logs using length andknot information. The 140 logs involved in the study were of Scots pine with top diameters spanning the range from 153 to213 millimeters. The center yield sawn from these logs was of two dimensions. The smaller logs (153-187 mm) were sawnwith a 2 ex pattern to 50 by 100 mm, and the larger logs (174-213 mm) were sawn to 50 by 125 mm with a 2 ex pattern.The data from the logs were collected at the log sorting station by an industrial one-directional x-ray log scanner incombination with a 3-D optical scanner. The data from the sawn center yield were collected by an industrial cross-fedsurface scanning system situated in the sawmill's green sorting station. Both systems are used in the sawmill's normalcontinuous production. The results show that over 90% of all planks could be matched to the right log, which bespeaksa great potential for further development and realization of fingerprint tracing as a tool for process control and processimprovement.

  • 12. 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)
  • 13. 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)
  • 14. 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)
  • 15.
    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)
  • 16.
    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.

  • 17.
    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)
  • 18. Johansson, J.
    et al.
    Hagman, Olle
    Oja, Johan
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Predicting moisture content and density of Scots pine by microwave scanning of sawn timber2003In: Computers and Electronics in Agriculture, ISSN 0168-1699, E-ISSN 1872-7107, Vol. 41, no 1-3, 85-90 p.Article in journal (Refereed)
    Abstract [en]

    Non-destructive testing of wood for prediction of strength is significantly influenced by wood density and moisture content. A sensor capable of measuring both density and moisture content would be a good tool to aid in predicting the strength of sawn timber. This study was carried out to investigate the possibility of calibrating a prediction model for the moisture content and density of Scots pine (Pinus sylvestris) using microwave sensors. The material was initially at green moisture content, and thereafter dried in several steps to zero moisture content. At each step all the samples were weighted, scanned with a microwave camera (Satimo 9.4 GHz) and CT scanned with a medical CT scanner (Siemens Somatom AR.T.). The output variables from the microwave camera were used as predictors, and CT images correlated with known moisture content were used as response variables. Multivariate models to predict moisture content and density were calibrated using partial least squares (PLS) regression. The result shows that it is possible to predict both moisture content and density with very high accuracy using microwave sensors

  • 19. Kvarnström, Björn
    et al.
    Oja, Johan
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Applications of RFID to improve traceability in continuous processes2010In: Sustainable Radio Frequency Identification Solutions, Vienna, Austria: IN-TECH, 2010, 69-86 p.Chapter in book (Other academic)
  • 20. Lundgren, Nils
    et al.
    Brännström, Mattias
    Hagman, Olle
    Oja, Johan
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Predicting the strength of Norway spruce by microwave scanning: a comparison with other scanning techniques2007In: Wood and Fiber Science, ISSN 0735-6161, Vol. 39, no 1, 167-172 p.Article in journal (Refereed)
    Abstract [en]

    In this study, 90 boards of Norway spruce (Picea abies (L.) Karst.) sized 48 x 148 mm in cross-section, have been examined using different scanning and measurement techniques. All of the boards originated from a sawmill located in southern Finland. Planar X-ray scanning, microwave scanning, and grain-angle measurement have been performed. In addition, strength and elastic properties were assessed for eachpiece by four point bending. The purpose of the study was to relate the potential of microwave scanning compared to other, industrially available techniques and to explain the physiological background of the microwave responses. The results show that the microwave signal, after transmission through wood, contains information about the bending strength and the modulus of elasticity. The correlation to densityis a key factor. Annual ring width was also found to be correlated both to microwave measurements and strength properties.

  • 21.
    Lycken, Anders
    et al.
    Luleå tekniska universitet.
    Oja, Johan
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    A multivariate approach to automatic grading of Pinus sylvestris sawn timber2006In: Scandinavian Journal of Forest Research, ISSN 0282-7581, E-ISSN 1651-1891, Vol. 21, no 2, 167-174 p.Article in journal (Refereed)
    Abstract [en]

    The objective of this study was to create an easier way to handle the often complicated and intricate situations with which the operator of an automatic grading system is faced each time a change to the grading rules is proposed. The scope of the study was the possibility of a holistic method of automatic appearance grading of sawn wood similar to manual grading and based on multivariate statistics. The study was based on 90 Scots pine ( Pinus sylvestris L.) sawlogs. The logs were sawn and the boards were scanned and manually graded. The result of the manual grading was defined as the true grade. Models for prediction of board grade based on aggregated defect variables were calibrated using partial least squares regression. The classification based on the multivariate models resulted in 80-85% of the boards being correctly graded according to the manual grading. In conclusion, this paper shows that a multivariate statistical approach for grading timber is a possible way to simplify the process of grading and to customize the grading rules when using an automatic grading system

  • 22. Moberg, L.
    et al.
    Eriksson, L.
    Oja, Johan
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Effects of different silvicultural regimes on wood quality and timber yield: a simulation approach2005In: Proceedings Fifth IUFRO Workshop: Connections between Forest Resources and Wood Quality: Modelling Approaches and Simulation Software, 2005Conference paper (Refereed)
  • 23.
    Nordmark, Urban
    et al.
    Luleå tekniska universitet.
    Oja, Johan
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Prediction of board values in Pinus sylvestris sawlogs using X-ray scanning and optical three-dimensional scanning of stems2004In: Scandinavian Journal of Forest Research, ISSN 0282-7581, E-ISSN 1651-1891, Vol. 19, no 5, 473-480 p.Article in journal (Refereed)
    Abstract [en]

    As the sawmill industry strives towards customer orientation, the need for sorting of logs according to quality has been recognized, and automatic sorting based on measurements by three-dimensional (3D) optical log scanners has been implemented at sawmills. There is even a small number of sawmills using the X-ray log scanner for automatic log-sorting. At the log-sorting stage, the potential of the raw material to fulfil the needs has already been reduced by the decisions taken when the trees were bucked (cross-cut) into logs. Thus, the application of predictions of the boards' properties at the bucking stage is desirable. This study investigates the possibility of predicting board values from logs based on 3D scanning alone and 3D scanning in combination with X-ray scanning of stems. This study is based on 628 logs scanned by computed tomography that make up the Swedish Pine Stem Bank. Simulated sawing of the logs gave product values for each log. Prediction models on product value were adapted using partial least squares regression and x-variables derived from the properties of the logs and their original stems, measurable with a 3D log scanner and the X-ray LogScanner. The results were promising. Using a 3D scanner alone, R2 was 0.68, and using a 3D scanner in combination with an X-ray LogScanner, R2 was 0.72.

  • 24. Nyström, Jan
    et al.
    Oja, Johan
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Broman, Olof
    Modelling the connection between industrially measured raw material properties and end user preferences: Part 1. The simulation tool2008In: Connection between Forest Resources and Wood Quality: Modelling Approaches and Simulation Software. IUFRO Working Party 5.01.04 Wood Quality Modelling, June 8. - 14, Koli, Finland / [ed] H. Peltola, 2008Conference paper (Other academic)
  • 25.
    Oja, Johan
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    A comparison between three different methods of measuring knot parameters in Picea abies1997In: Scandinavian Journal of Forest Research, ISSN 0282-7581, E-ISSN 1651-1891, Vol. 12, no 3, 311-315 p.Article in journal (Refereed)
    Abstract [en]

    Both foresters and sawmillers are interested in the knot structure of trees; in particular, position and number of knots, knot diameter, knot length and dead knot border. For research purposes, it is possible today to carry out non-destructive measurements using computer tomography (CT) and image analysis. The aim of this study was to measure knot parameters on Norway spruce (Picea abies (L.) Karst.) using a non-destructive method developed for Scots pine (Pinus sylvestris L.), and to compare the results of this method with the results of two different destructive methods. In order to do this, two Norway spruce stems were scanned by CT. Then five logs from one stem were cut into flitches 20 mm thick and the defects on the sawn surfaces were scanned manually. The other stem was cut just above every whorl and then each knot was split through its centre and the knot parameters were measured manually. The study showed that the CT method compares well with the destructive methods. It is a reasonably fast, non-destructive method which measures position and diameter of knots and detects larger knots with acceptable accuracy. The study also showed that a large number of smaller knots were not found by the CT method and that the CT method measured knot length and dead knot border with low accuracy. This means that the CT method has to be adjusted to Norway spruce in order to improve its ability to measure knot length and dead knot border and to detect smaller knots.

  • 26.
    Oja, Johan
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Automatisk bestämning av timmeregenskaper med oförstörande mätteknik: kartläggning av teknik och FoU2000Report (Other academic)
  • 27.
    Oja, Johan
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Evaluation of knot parameters measured automatically in CT-images of Norway spruce (Picea abies (L.) Karst.)2000In: European Journal of Wood and Wood Products, ISSN 0018-3768, E-ISSN 1436-736X, Vol. 58, no 5, 375-379 p.Article in journal (Refereed)
    Abstract [en]

    Knot parameters measured automatically in CT-images of Norway spruce have been evaluated on logs from four plots in the Norway spruce stem bank. The evaluation was made through comparisons between measurements on real centre boards and measurements on reconstructed boards. The reconstructions were based on the automatically measured parameter descriptions of knots and log shape and on simulated sawing. The diameter of knots was measured with a mean error of -2 mm and a standard deviation of 3 mm. It was shown that the reconstructed centre boards were well in accordance with the real centre boards in terms of position, number, size and type of knots. The exception is knot type for small knots in large butt logs.

  • 28.
    Oja, Johan
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Industrial Experiences of Log Scanning in Sweden2003Conference paper (Other academic)
  • 29.
    Oja, Johan
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Measuring knots and resin pockets in CT-images of Norway spruce1997Licentiate thesis, comprehensive summary (Other academic)
  • 30.
    Oja, Johan
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    X-ray measurement of properties of saw logs1999Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    A nondestructive method of measuring knot parameters for research purposes has been compared to alternative, destructive methods. The method is based on automatic analysis of CT-images. The image analysis algorithms were adjusted to and evaluated on Norway spruce. The possibilities of measuring resin pockets in CT-images have been studied and stereological methods have been applied on volume estimation of resin pockets in saw logs. For research purposes the study showed that compared to destructive methods, both accuracy and speed of the CT-method were competitive. It was also shown that resin pockets can be detected and measured in CT-images of Norway spruce. Data from the CT-scanned logs was used to simulate an industrial X-ray LogScanner. The X-ray LogScanner was based on two X-ray sources and designed for scanning at 3 m/s. The possibility of using this X-ray LogScanner to make nondestructive measurements of properties of saw logs has been investigated. The study showed that the X-ray LogScanner measures minimum shadow diameter under bark before debarking with an accuracy comparable to a 3D-scanner and that the sawing position could be controlled based on X-ray LogScanner measurements of the best half of the logs. The X-ray LogScanner could also be used to measure percentage of heartwood and green heartwood density. Based on the X-ray LogScanner measurements it was possible to calibrate PLS-models for prediction of the bending stiffness of the centerboards.

  • 31. Oja, Johan
    et al.
    Broman, Olof
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Lindfors, Sven.Erik
    Luleå tekniska universitet.
    Projektrapport: timmerinmätningsstöd1999Report (Other academic)
    Abstract [sv]

    Bakgrunden till projektet är de höga kraven på snabbhet och noggrannhet vid inmätning av sågtimmer. Målet med projektet är att utveckla ett datorbaserat timmerinmätningsstöd. Timmerinmätningsstödet ska presentera en stillbild av stockens rotändyta tillsammans med displaydata och kvalitetsförslag baserat på data från en skuggmätram. Timmerinmätningsstödet består av två kameror som tar ändytebilder, en dator som tar fram kvalitetsförslaget baserat på mätdata från skuggmätramen och ytterligare en dator som presenterar ändytebilden tillsammans med kvalitets- förslag och övrig information. Utvärderingen av bildernas kvalitet visade att det är möjligt att hitta 87% av de ändytor som har röta, kåd-, tjur- eller källved och 65% av de ändytor som har märg- och kapsprickor. Arbetet med ta fram ett kvalitetsförslag visar att PLS-modeller och mätrams- data gör det möjligt att ge ett kvalitetsförslag för vederlagsmätning, dock utan hänsyn till ändytefel och enstaka defekter som till exempel lyror. En utvärdering av virkesmätarnas erfarenheter och synpunkter visade bland annat att de upplever att ändytebildens kvalitet är god och att de har stor nytta av få en ändytebild kombinerad med displaydata. Kvalitetsförslaget för gran upplevs fungera tillräckligt bra för att kunna bli ett hjälpmedel medan kvalitetsförslaget för tall måste bli mer pålitligt för att vara till någon nytta.

  • 32. Oja, Johan
    et al.
    Broman, Olof
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Nyström, Jan
    Modelling the connection between industrially measured raw material properties and end user preferences: Part 3. Optimizing the industrial production2008In: Connection between Forest Resources and Wood Quality: Modelling Approaches and Simulation Software. IUFRO Working Party 5.01.04 Wood Quality Modelling, June 8. - 14, Koli, Finland / [ed] H. Peltola, 2008Conference paper (Other academic)
  • 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, 107-114 p.Conference 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, 89-95 p.Article 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, 340-347 p.Article 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, 88-96 p.Article 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, 203-208 p.Article 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, 55-60 p.Article 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.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Temnerud, E.
    Sveriges Lantbruksuniversitet.
    The appearance of resin pockets in CT-images of Norway spruce (Picea abies (L.) Karst.)1999In: European Journal of Wood and Wood Products, ISSN 0018-3768, E-ISSN 1436-736X, Vol. 57, no 5, 400-406 p.Article in journal (Refereed)
    Abstract [en]

    The appearance of resin pockets in CT-images of Norway spruce (Picea abies (L.) Karst.) was studied. The study also includes a comparison between measured and calculated CT-numbers of Norway spruce resin and wood. It was found that it should be possible to create algorithms that automatically detect large resin pockets in CT-images of Norway spruce. Compared to resin pockets in heartwood, resin pockets in green sapwood are more difficult to detect due to the high density of the surrounding wood. The study also showed that the correlation between measured and calculated CT-numbers was high and that it is possible to use the same function for conversion between CT-number and density for both green wood and resin.

  • 44. 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, 63-75 p.Article 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

  • 45.
    Sepulveda, P
    et al.
    Luleå tekniska universitet.
    Kline, D.E.
    Department of Wood Science, Virginia Technology, Blacksburg.
    Oja, Johan
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Prediction of fiber orientation in Norway spruce logs using an X-ray log scanner: a preliminary study2003In: Wood and Fiber Science, ISSN 0735-6161, Vol. 35, no 3, 421-428 p.Article in journal (Refereed)
    Abstract [en]

    Previous studies have shown that a CT scanner can be used to accurately measure spiral grain in logs. However, the application of such a CT scanning system is of limited use in an industrial application because of the cost and processing time associated with CT scanning. The aim of this study was a preliminary assessment of predicting fiber orientation, an indication of spiral grain, in center-boards from Norway spruce (Picea abies) saw logs using an X-ray log scanner. The scanner is a high-speed commercial log-scanning device used to grade and sort logs based on internal quality characteristics. In this study, nineteen logs were first scanned with a CT scanner. Afterwards, the CT images were used to simulate X-ray log scanner images, with which measurements of different variables such as diameter, taper, percentage of heartwood, density, and density variations could be calculated. Depending on the log diameter, two to four centerboards were then sawn from each log, and the fiber orientations of the boards were measured for observed spiral grain for each log. A statistical model for predicting fiber orientation was then developed using partial least squares (PLS) regression. The PLS-model was developed to predict the fiber orientation of a log at a distance of 50 mm from the pith based on different variables that are measurable with the industrial X-ray log scanner. The resulting PLS-model was shown to produce an R2 = 0.45 for the training set and R2 = 0.55 for the test set. The statistically significant variables used to predict spiral grain were green heartwood density, knot volume, and a measure of the unsymmetrical distribution of knot volume. Significant correlation of these variables warrants further research and development with the X-ray log scanner to nondestructively sort out logs with excessive spiral grain.

  • 46.
    Sepulveda, P.
    et al.
    Luleå tekniska universitet.
    Oja, Johan
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Grönlund, Anders
    Modelling spiral grain in saw logs based on data form a simlated X-ray LogScanner2004In: 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)
  • 47.
    Sepulveda, Paul
    et al.
    Luleå tekniska universitet.
    Oja, Johan
    Grönlund, Anders
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Predicting spiral grain by computed tomography of Norway spruce2002In: Journal of Wood Science, ISSN 1435-0211, E-ISSN 1611-4663, Vol. 48, no 6, 479-483 p.Article in journal (Refereed)
    Abstract [en]

    Spiral grain is a feature of wood that affects the shape of the sawn timber. Boards sawn from logs with a large spiral grain have a tendency to twist when the moisture content changes. The aim of this study was to investigate the possibility of predicting spiral grain based on variables that should be measurable with an X-ray LogScanner. The study was based on 49 Norway spruce (Picea abies) logs from three stands in Sweden. The logs were scanned with a computed tomography (CT) scanner every 10 mm along the log. Concentric surfaces at various distances from the pith were then reconstructed from the stack of CT images. The spiral grain angle was measured in these concentric surface images, and a statistical model for predicting spiral grain was calibrated using partial least squares (PLS) regression. The PLS model predicts the spiral grain of a log at a distance 50 mm from the pith based on different variables that should be measurable with an industrial X-ray LogScanner. The result was a PLS model with R2 = 0.52 for the training set and R 2 = 0.37 for the test set. We concluded that it should be possible to predict the spiral grain of a log based on variables measured by an industrial X-ray LogScanner. The most important variables for predicting spiral grain were measures of sapwood content, variation in the ratio between the heartwood and log areas, and the standard deviation for the mean log density in 10 mm thick cross slices along the log. The accuracy when sorting the logs into two groups with spiral grain of greater than or equal 2.0° and of less than or equal 2.0°, respectively, was 84% of the correctly sorted logs.

  • 48. Skog, Johan
    et al.
    Oja, Johan
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Combining x-ray and three-dimensional scanning of sawlogs: comparison between one and two x-ray directions2009In: Proceedings of the 6th International Symposium on Image and Signal Processing and Analysis, 2009: ISPA 2009 ; Salzburg, Austria, 16 - 18 Sept. 2009 / [ed] Peter Zinterhof, Piscataway, NJ: IEEE Communications Society, 2009, 353-358 p.Conference paper (Refereed)
    Abstract [en]

    In many sawmills, presorting of sawlogs is based on data from optical three-dimensional (3D) scanners. The use of x-ray log scanners is also becoming increasingly common and most sawmills installing an x-ray scanner already have a 3D scanner present. It is in this paper demonstrated how data from oneand two-directional x-ray scanners can be combined with 3D scanner data using path length compensation. Examples show how the resulting images may be processed in order to predict quality parameters such as heartwood diameter and green heartwood density. Using the proposed method, it is possible to improve the accuracy of these important quality sorting parameters using existing equipment. This will improve the presorting at sawmills, thus reducing the production of off-grade products carrying unwanted combinations of dimension and grade.

  • 49. Skog, Johan
    et al.
    Oja, Johan
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Density measurements in Pinus sylvestris sawlogs combining X-rayand three-dimensional scanning2010In: Scandinavian Journal of Forest Research, ISSN 0282-7581, E-ISSN 1651-1891, Vol. 25, no 5, 470-481 p.Article in journal (Refereed)
    Abstract [en]

    Wood density is an important quality variable, closely related to the mechanical properties of the wood. Precise wood density measurements in the log sorting would enable density sorting of logs for products such as strength-graded wood and fingerjointed wood. Density sorting of logs would also give more homogeneous drying properties and thus improve the quality of the final products. By compensating the radiographs from an X-ray log scanner for the varying path lengths using outer shape data from a three-dimensional (3D) scanner, it is possible to make precise estimates of both green and dry density. Measurements on simulated industrial data were compared with densities measured in computed tomographic (CT) images for 560 Scots pine (Pinus sylvestris L.) logs. It was found that green sapwood density could be measured with predictability R2 = 0.65 and root mean square error (RMSE) of 25 kg m-3. Green and dry heartwood densities were measured with similar precision: R2 = 0.79 and RMSE = 32 kg m-3 for green density and R2 = 0.83 and RMSE = 32 kg m-3 for dry density.

  • 50. Skog, Johan
    et al.
    Oja, Johan
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Heartwood diameter measurements in Pinus sylvestris sawlogs combining X-ray and three-dimensional scanning2009In: Scandinavian Journal of Forest Research, ISSN 0282-7581, E-ISSN 1651-1891, Vol. 24, no 1, 182-188 p.Article in journal (Refereed)
    Abstract [en]

    Quality sorting of sawlogs based on three-dimensional (3D) or X-ray scanning or a multivariate combination of variables from both methods may be used to decrease the production of off-grade products carrying unwanted combinations of dimension and grade. There is, however, potential for further improving the sorting accuracy if 3D and X-ray raw data are combined at an early stage using path length compensation. From the measured 3D shape, a good estimate of the length of each X-ray path through the log can be made, enabling the calculation of a log density profile from the measured X-ray attenuation. The effect of this technique on heartwood diameter measurements of 423 Scots pine (Pinus sylvestris L.) logs was evaluated. By the addition of 3D data to the X-ray data it was possible to raise the predictability of the heartwood diameter from R 2=0.84 to 0.95 and to improve the root mean square error from 17 mm to 9.3 mm, primarily because of the enhanced contrast between heartwood and sapwood.

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