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  • 1.
    Berglund, Anders
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Träteknologi.
    Efficient utilization of sawlogs using scanning techniques and computer modelling2014Doktoravhandling, med artikler (Annet vitenskapelig)
    Abstract [en]

    The main question asked of the work described in this thesis was howthe sawing of logs into sawn timber can be performed more efficientlywith respect to the choice of raw material, volume and value yield in thesawing and in the grading of the sawn timber produced.The development of industrial computed tomography scanning providesinformation about the external and internal properties of a sawlogat production speed. This opens up new possibilities of controlling theflow of raw material early in the process and of optimizing the breakdownof each sawlog. Another use of industrial computed tomography scanningis for predicting the strength of sawn timber better than is possible withcurrent visual and machine strength grading equipment.A more traditional way of increasing sawmill profitability is by increasingthe volume of sawn timber. One way of doing this is by reducing thesaw blade thickness which results in less sawdust. With the use of thinnersaw blades however there is a risk that the saw blades become misalignedwhich in turn leads to saw mismatch, an unevenness seen on the surfaceof the sawn timber. In this work, attempts were made to automaticallymeasure and monitor saw mismatch in a sawmill during ongoing production.It is also possible for a sawmill to increase its profitability by measuresnot related to the sawing process. One such example is customer adaptationwhen delivering the sawn timber. Different customers use the sawntimber for different purposes and consequently have different requirements,which is why the sawn timber produced is graded and sorted before it isdelivered to the customer. In this work, an alternative method for gradingsawn timber more efficiently using a multivariate method was developedand evaluated.The following results have been obtained:Log breakdowns of 716 Scots pine logs and 750 Norway spruce logsthat had been scanned using computed tomography were simulated andthe rotational position of each log was optimized. The results showedan average relative value increase of 16% for appearance graded sawntimber compared to the conventional horns down position. When simulating log breakdowns of 677 Norway spruce logs with respect to visuallystrength graded sawn timber, an average relative value increase of 11%was obtained. The effect that errors in knot detection algorithms had ona breakdown optimization was also analysed when optimizing breakdownof 57 Norway spruce sawlogs. The results showed that errors in the knotdiameter had the most severe impact on the average relative value increaseof a log rotation optimization, followed by errors in the dead knot border.The smallest effect was observed in the case of errors in rotational positionof the knots.Computed tomography scanning can also be used in a sawmill for log sorting in relation to different end-uses of the sawn timber. A simulationsoftware for cross-cutting optimization based on computed tomographydata was developed and it was shown that there was a reasonable correlationbetween these results and the results of an industrial system. Sincethe developed software can be combined with log breakdown simulationsbased on computed tomography data, it is evident that computed tomographycan be used to identify logs that would result in a poor volume yieldin the subsequent cross-cut optimization.Destructive bending strength tests were performed on 113 pieces of Norway spruce sawn timber. Multivariate models for predicting the bending strength of the sawn timber were created using computed tomography data of the sawlogs from which the sawn timber originated. The results showed that computed tomography scanning of logs produced prediction models of bending strength with a higher accuracy than discrete X-rayscanning. The main advantage was the detailed knot information that could be used in the prediction models.A method to measure saw mismatch automatically in a sawmill basedon laser triangulation was developed and the measurements were well correlatedwith manual measurements of saw mismatch. When laser triangulationwas used to measure saw mismatch in a sawmill, a distinguishabletrend of increasing magnitude and frequency of saw mismatch was observed.Finally, ways in which the sawn timber in a sawmill could be gradedand sorted more efficiently was investigated. It was found that by using agrading method based on multivariate techniques it is possible to increasethe proportion of higher sawn timber grades by up to 10 percentage points,which may increase sawmill profitability.

    Fulltekst (pdf)
    FULLTEXT01
  • 2.
    Berglund, Anders
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Träteknologi.
    Process control and production strategies in the sawmill industry2013Licentiatavhandling, med artikler (Annet vitenskapelig)
    Abstract [en]

    The sawmill process itself is not complicated. What makes it complex is thediversity of the raw material, the logs that are processed in the sawmill, and thedivergent production with many different end products. In the sawmill variousnumber of measurement and scanning equipments are installed. These are usedfor controlling the various processes and for measuring how well they are carriedthrough.The main objective of this thesis is to build knowledge of how we can makethe sawing process, one of the main steps within the sawmill process, more efficientwith respect to both volume yield and value recovery by new equipmentand new production strategies. The intention has been that the conclusions inthis thesis can contribute to a knowledge base that can be of assistance in decisionsregarding control process parameters and production strategies for a sawmill.There is a possible economic saving by increased volume yield for the sawmillsif the saw kerf width can be reduced, but there is a fear that the presence andmagnitude of saw mismatch will be affected by this. Saw mismatch occurs on thesawn boards due to displacement in axial direction of the saw blades in doublearbor saw machines as a consequence of wear, heat or mechanical disturbance. Itis shown in this thesis that it was possible to measure saw mismatch automaticallyduring sawmill operation by laser triangulation and that the measurements werecomparable to manual measurements. It is also suggested how the presence andmagnitude of saw mismatch can be evaluated when measurements are carriedout in a sawmill.Another study addressed in the thesis is the consideration of applying analternative log rotation for each log than the in Scandinavia industrial praxis ofhorns down (log crook faced upwards). This possibility for a greater profit returncomes in question since the development of an industrial computed tomographyscanner makes the internal knot structure of the log available.Log breakdown simulations of about 600 Scots pine (Pinus sylvestris [L.])logs and 800 Norway spruce (Picea abies [L.] Karst.) logs mainly from differentgeographic locations in Sweden showed that there is a potential value increasewhen rotating each log for greatest profit return. The potential value increase wasdependent of the rotational error of the sawing machine and the price differencesbetween quality grades. For the 600 Scots pine logs and the 800 Norway sprucelogs in the study an increased average value increase of 13% was obtained ifapplying the rotation that maximizes the value of each log instead of the horns down position. An introduced rotational error of the sawing machine reducedthe value potential to 6%. There was a weak correlation between the log rotationthat maximizes the value of each log and the outer shape of the logs. This meansthat the outer shape can not be used as an indicator of how the log should berotated for greatest profit return.One subject of discussion in the thesis is also the importance of representativeinput data in order to make as general conclusions as possible. The Swedishstem bank has been an important factor in many studies made in the field ofwood technology. It is a well-documented data set and computed tomographyscanning of logs has made it possible to represent internal wood features in logbreakdown software. Since computed tomography scanning of logs is a time consuming process the number of scanned logs are relatively small. Now thatan industrial computed tomography scanner operating at production speed isentering the market this opens up new possibilities. Hopefully simulation studiesthat are performed on larger industrial data sets coming from logs processed inthe sawmills at a daily basis is not too far away.

    Fulltekst (pdf)
    FULLTEXT01
  • 3.
    Berglund, Anders
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Träteknologi.
    Broman, Olof
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Träteknologi.
    Grönlund, Anders
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Träteknologi.
    Fredriksson, Magnus
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Träteknologi.
    Improved log rotation using information from a computed tomography scanner2013Inngår i: Computers and Electronics in Agriculture, ISSN 0168-1699, E-ISSN 1872-7107, Vol. 90, s. 152-158Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

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

  • 4.
    Berglund, Anders
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Träteknik.
    Broman, Olof
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Träteknik.
    Oja, Johan
    Grönlund, Anders
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Träteknik.
    Customer adapted grading of Scots pine sawn timber using a multivariate method2015Inngår i: Scandinavian Journal of Forest Research, ISSN 0282-7581, E-ISSN 1651-1891, Vol. 30, nr 1, s. 87-97Artikkel i tidsskrift (Fagfellevurdert)
    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.

  • 5.
    Berglund, Anders
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Träteknologi.
    Dahlquist, Simon
    SP Trä.
    Grönlund, Anders
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Träteknologi.
    Detection of saw mismatch in double arbor saw machines using laser triangulation2013Inngår i: Wood Material Science & Engineering, ISSN 1748-0272, E-ISSN 1748-0280, Vol. 8, nr 4, s. 219-225Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    In the sawing process of a sawmill, not only are the target sizes of great importance. The saw mismatch that may occur in double arbor saw machines is also an essential parameter that affects the planing allowance, as well as the quality of the sawn products. In this study, a newly developed measurement equipment for detecting saw mismatch in the green sorting line of a sawmill has been evaluated in an initial experimental test. The obtained data has been compared to manual measurements of saw mismatch with good results. Also, based on a small sample, 75 – 95% of the boards with a maximal saw mismatch exceeding 0.5 mm are detected. The rate of detection depends on the number of cameras used.

  • 6. Berglund, Anders
    et al.
    Fredriksson, Magnus
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Träteknologi.
    Broman, Olof
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Träteknologi.
    Grönlund, Anders
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Träteknologi.
    Project: CT-Pro2012Annet (Annet (populærvitenskap, debatt, mm))
    Abstract [sv]

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

  • 7.
    Berglund, Anders
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Träteknologi.
    Grönlund, Anders
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Träteknologi.
    An industrial test of measuring saw mismatch using laser triangulation2013Konferansepaper (Fagfellevurdert)
    Abstract [en]

    Sawing yield is an important parameter for the sawmill profit. One way to increase the sawing yield is by a reduced saw kerf width, an adapted shrinking allowance, and a lower sawing allowance. The Swedish sawmills on the other hand see a risk of poorer sawing accuracy and sawing precision and at worst, more frequent saw blade failures. One problem with a reduced saw kerf width is the saw mismatch that may occur in double arbor saw machines. Saw mismatch occurs when the saw blades are displaced in axial direction with respect to each other due to wear, heat or mechanical disturbance. In this study the aim was to test the robustness of a laser triangulation unit used for measuring saw mismatch during sawmill operation. The aim was also to find a suitable response variable for saw mismatch which was evaluated by using the cant height, feed speed and average top diameter of the logs as predicting variables in a partial least squares regression. The goodness of prediction for each response variable was used to compare the response variables with each other. The results showed that the robustness when measuring saw mismatch by laser triangulation during ongoing sawmill production was satisfactory. The response variable with the best goodness of prediction (Q2 = 0.135) was defined using a sliding window with a size of 500 boards. Each element of the response variable was calculated as the share of boards within the sliding window exceeding a threshold value of 0.5 mm. This response variable was positively correlated with the cant height, feed speed and average top diameter of the log. Future work requires a designed experiment where the predicting variables are varied systematically and where the effect of characteristics and wear of the saw blades is also considered.

    Fulltekst (pdf)
    FULLTEXT01
  • 8. Berglund, Anders
    et al.
    Grönlund, Anders
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Träteknologi.
    Dahlquist, Simon
    SP Trä, Sverige.
    Projekt: Processuppföljning sågverk2013Annet (Annet (populærvitenskap, debatt, mm))
  • 9.
    Berglund, Anders
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Träteknologi.
    Johansson, Erik
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Träteknologi.
    Skog, Johan
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Träteknologi.
    Value optimized log rotation for strength graded boards using computed tomography2014Inngår i: European Journal of Wood and Wood Products, ISSN 0018-3768, E-ISSN 1436-736X, Vol. 72, nr 5, s. 635-642Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    A possible application for an industrial computed tomography scanner in a sawmill is finding an optimal rotational position of logs with respect to knots and outer shape. Since a computed tomography scanner is a great investment, it is important to investigate potential profitability of such an investment for different production strategies. The objective of this study was to investigate the potential value increase of the sawn timber of Norway spruce (Picea abies (L.) Karst.) by rotating logs to their optimum position prior to sawing compared with sawing all logs in horns down position. The production strategy evaluated by log breakdown simulation in this case study was to produce strength graded timber of the center boards, while the side boards were appearance graded. This case study showed an average value increase with respect to the value of center boards, side boards and chips of 11 %.

  • 10.
    Breinig, Lorenz
    et al.
    Forstliche Versuchs- und Forschungsanstalt Baden-Württemberg (FVA).
    Berglund, Anders
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Träteknologi.
    Grönlund, Anders
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Träteknologi.
    Bruechert, Franka
    Forstliche Versuchs- und Forschungsanstalt Baden-Württemberg (FVA).
    Sauter, Udo
    Forstliche Versuchs- und Forschungsanstalt Baden-Württemberg (FVA).
    Effect of knot detection inaccuracy on value recovery improvement when using a CT log scanner for sawing control2013Inngår i: Forest products journal, ISSN 0015-7473, Vol. 63, nr 7-8, s. 263-274Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Roundwood scanners utilizing X-ray computed tomography (CT) provide the information required for individual log-sawing optimization. However, errors in the automated detection of quality-relevant internal wood features for sawing control may lead to improper log positioning at breakdown, impairing the realization of value recovery potential. It is thus of interest to have an estimation of the impact of feature detection errors on the performance of sawing optimization. A sensitivity analysis was conducted to quantify the effect of errors in knot detection on a breakdown optimization by adjustment of log rotation. Therefore, sawing simulations were performed with the geometric descriptions of log shape and internal knots extracted from the CT scans of 57 Norway spruce (Picea abies (L.) Karst.) logs. Three types of artificially set knot description errors were tested under different pricing and product scenarios, each in different magnitudes as systematic or random error. Errors in knot diameter were found to have the greatest impact for both systematic and random errors. The effect of errors in dead knot border radial position was less pronounced but still substantial for higher error levels, while errors in knot rotational position could be neglected even for the highest magnitudes of error tested. The assumed price differentiation between product qualities had a major influence on the impact of the errors. It could be observed that with errors of higher magnitudes than those reported for present knot detection algorithms, an improvement in value recovery compared with outer-shape–based optimization still resulted in the simulated rotation optimization.

  • 11.
    Fredriksson, Magnus
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Träteknik.
    Berglund, Anders
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Träteknik.
    Broman, Olof
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Träteknik.
    Validating a crosscutting simulation program based on computed tomography scanning of logs2015Inngår i: European Journal of Wood and Wood Products, ISSN 0018-3768, E-ISSN 1436-736X, Vol. 73, nr 2, s. 143-150Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

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

    Fulltekst (pdf)
    fulltext
  • 12.
    Fredriksson, Magnus
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Träteknologi.
    Johansson, Erik
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Träteknologi.
    Berglund, Anders
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Träteknologi.
    Rotating Pinus sylvestris sawlogs by projecting knots from computed tomography images onto a plane2014Inngår i: BioResources, ISSN 1930-2126, E-ISSN 1930-2126, Vol. 9, nr 1, s. 816-827Artikkel i tidsskrift (Fagfellevurdert)
    Fulltekst (pdf)
    FULLTEXT01
  • 13.
    Johansson, Erik
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Träteknik.
    Berglund, Anders
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Träteknik.
    Skog, Johan
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Träteknik. SP Sveriges Tekniska Forskningsinstitut, SP Trä.
    Comparing predictability of board strength between computed tomography, discrete x-ray, and 3D scanning of Norway spruce logs2016Inngår i: Wood Material Science & Engineering, ISSN 1748-0272, E-ISSN 1748-0280, Vol. 11, nr 2, s. 116-125Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Strength graded boards of Norway spruce (Picea abies (L.) Karst.) are important products for many Scandinavian sawmills. If the bending strength of the produced boards can be predicted before sawing the logs, the raw material can be used more efficiently. In previous studies it is shown that the bending strength can be predicted to some extent using discrete X-ray scanning of logs. In this study, we have evaluated if it is possible to predict bending strength of Norway spruce boards with higher accuracy using computed tomography (CT) scanning of logs compared to a combination of discrete X-ray and 3D scanning. The method was to construct multivariate models of bending strength for three different board dimensions. Our results showed that CT scanning of logs produces better models of bending strength compared to a combination of discrete X-ray and 3D scanning. The main reason for this difference was the benefit of knowing the position of where the boards were cut from the logs and therefore detailed knot information could be used in the prediction models. Due to the small number of observations in this study, care should be taken when comparing the resulting prediction models to results from other studies

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