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Broman, Olof
Publications (10 of 55) Show all publications
Olofsson, L., Broman, O. & Sandberg, D. (2019). Holistic-Subjective Automatic Grading of Sawn Timber: Sensitivity to Systematic Changes. In: International Wood Machining Seminar: . Paper presented at International Wood Machining Seminar.
Open this publication in new window or tab >>Holistic-Subjective Automatic Grading of Sawn Timber: Sensitivity to Systematic Changes
2019 (English)In: International Wood Machining Seminar, 2019Conference paper, Published paper (Other academic)
Abstract [en]

Holistic-subjective automatic grading of sawn timber by a partial least squares (PLS) regression model required training of the model. This study tests the sensitivity towards systematic changes of a specialized PLS model, trained on a selected type of material suitable for a specific paneling product, when used to grade sawn timber systematically different than the material it was trained on. A sawmills automatic scanning system used cameras to measure knot and bark features on 900 planks. Each plank was split into three boards, and each board was shaped into an indoor paneling product and manually graded as desirable or undesirable at a planing mill. The plank grade was decided as the majority of the board-grade outcome. The knot and bark measurements were used to create a large set of feature variables for each plank that was correlated to the plank’s grade by PLS regression. Of the 900 available planks, 434 planks sawn from top logs were used as a class-balanced specialistic training set, with half of the planks resulting in a majority of desirable boards. The regression model trained on the class-balanced specialistic training set was used to grade a test set of 282 planks, containing 64 planks that by manual classification of automatically captured images were determined to be sawn from butt logs and were systematically different from the training material. The PLS model’s grading accuracy of the planks sawn from top logs was 76%, compared to 70% for the plank sawn from butt logs. The grading outcome resulted in a higher proportion of both delivered planks from the sawmill and received desirable planks by the planing mill when grading planks from top logs as compared to planks from butt logs. The results indicated that a specialistic PLS model should not be used for a generalistic use-case.

Keywords
sawmilling, wood, automatic grading, PLS-regression
National Category
Wood Science
Research subject
Wood Science and Engineering
Identifiers
urn:nbn:se:ltu:diva-74170 (URN)
Conference
International Wood Machining Seminar
Available from: 2019-06-04 Created: 2019-06-04 Last updated: 2019-08-15
Olofsson, L., Broman, O. & Sandberg, D. (2019). Holistic-subjective automatic grading of sawn timber: Sensitivity to systematic changes.. In: Schajer, G (Ed.), Proceedings of the 24th International Wood Machining Seminar, IWMS 24.: . Paper presented at IWMS 24. August 25-30, 2019, Corvallis, Oregon, USA (pp. 154-167). Corvallis: Oregon State University (OSU)
Open this publication in new window or tab >>Holistic-subjective automatic grading of sawn timber: Sensitivity to systematic changes.
2019 (English)In: Proceedings of the 24th International Wood Machining Seminar, IWMS 24. / [ed] Schajer, G, Corvallis: Oregon State University (OSU) , 2019, p. 154-167Conference paper, Published paper (Refereed)
Place, publisher, year, edition, pages
Corvallis: Oregon State University (OSU), 2019
National Category
Wood Science
Research subject
Wood Science and Engineering
Identifiers
urn:nbn:se:ltu:diva-76021 (URN)
Conference
IWMS 24. August 25-30, 2019, Corvallis, Oregon, USA
Available from: 2019-09-16 Created: 2019-09-16 Last updated: 2019-10-22
Olofsson, L., Broman, O., Skog, J., Fredriksson, M. & Sandberg, D. (2019). Multivariate product adapted grading of Scots pine sawn timber for an industrial customer, part 1: Method development. Wood Material Science & Engineering, 14(6), 428-436
Open this publication in new window or tab >>Multivariate product adapted grading of Scots pine sawn timber for an industrial customer, part 1: Method development
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2019 (English)In: Wood Material Science & Engineering, ISSN 1748-0272, E-ISSN 1748-0280, Vol. 14, no 6, p. 428-436Article in journal (Refereed) Published
Abstract [en]

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

Place, publisher, year, edition, pages
Taylor & Francis, 2019
Keywords
Sawn timber, visual grading, customer adoption, discriminant analysis
National Category
Wood Science Other Mechanical Engineering
Research subject
Wood Science and Engineering
Identifiers
urn:nbn:se:ltu:diva-73967 (URN)10.1080/17480272.2019.1617779 (DOI)
Funder
Vinnova, 2018-02749
Note

Validerad;2019;Nivå 2;2019-10-10 (johcin)

Available from: 2019-05-16 Created: 2019-05-16 Last updated: 2019-10-16Bibliographically approved
Olofsson, L., Broman, O., Skog, J., Fredriksson, M. & Sandberg, D. (2019). Multivariate Product Adapted Grading of Scots Pine Sawn Timber for an Industrial Customer, Part 2: Robustness to Disturbances. Wood Material Science & Engineering, 14(6), 420-427
Open this publication in new window or tab >>Multivariate Product Adapted Grading of Scots Pine Sawn Timber for an Industrial Customer, Part 2: Robustness to Disturbances
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2019 (English)In: Wood Material Science & Engineering, ISSN 1748-0272, E-ISSN 1748-0280, Vol. 14, no 6, p. 420-427Article in journal (Refereed) Published
Abstract [en]

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

Place, publisher, year, edition, pages
Taylor & Francis, 2019
Keywords
Sawn timber, visual grading, customer adoption, discriminant analysis
National Category
Wood Science Other Mechanical Engineering
Research subject
Wood Science and Engineering
Identifiers
urn:nbn:se:ltu:diva-73854 (URN)10.1080/17480272.2019.1612944 (DOI)000469741800001 ()2-s2.0-85065546163 (Scopus ID)
Funder
Vinnova, 2018-02749
Note

Validerad;2019;Nivå 2;2019-10-16 (johcin)

Available from: 2019-05-06 Created: 2019-05-06 Last updated: 2019-10-16Bibliographically approved
Olofsson, L., Möller, C.-J., Wendel, C., Oja, J. & Broman, O. (2019). New possibilities with CT scanning in the forest value chain. In: 21st International Nondestructive Testing and Evaluation of Wood Symposium: . Paper presented at International Nondestructive Testing and Evaluation of Wood Symposium.
Open this publication in new window or tab >>New possibilities with CT scanning in the forest value chain
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2019 (English)In: 21st International Nondestructive Testing and Evaluation of Wood Symposium, 2019Conference paper, Published paper (Other academic)
Abstract [en]

Industrial high-resolution X-ray computed tomography (CT) scanners have recently been installed at several sawmills worldwide for the description of roundwood interior features and external log shape. These CT scanners represent a technological advancement for sawmill businesses that open a way to higher volume and value yields and new production planning strategies. This paper will present an indicative study of innovative use of non-destructive CT log data in a Swedish softwood sawmill, linking high-quality information of the wood material along the wood-value chain. Sawn timber was observed throughout the sawmill process line, i.e. from the log yard through the sawmill process until grading after the timber was dried. Before sawing, the CT scanner scanned the logs and calculated knot measurements from the 3D CT log data of simulated value-optimized center yield. A corresponding set of knot measurements were later calculated from the camera-based grading of the dried timber. Only considering knots from the two sets of measurements, the sawn timber was automatically given a quality assessment based on CT data, by camera-based scanning data, and by manual visual grading for reference. Partial least squares regression was used to create prediction models by correlating the two sets of knot measurements with the automatically determined grade from the dry-sorting. The prediction models tested increased the grading consistency between the grading based on CT data of virtual planks and based on camera data of the same planks. Furthermore, a traceability algorithm was tested as a tool to generate large data sets for future studies.

Keywords
sawn timber grading, computed tomography, partial least squares
National Category
Wood Science
Identifiers
urn:nbn:se:ltu:diva-75506 (URN)
Conference
International Nondestructive Testing and Evaluation of Wood Symposium
Available from: 2019-08-14 Created: 2019-08-14 Last updated: 2019-09-06
Olofsson, L., Broman, O., Fredriksson, M., Skog, J. & Sandberg, D. (2017). Customer adapted grading of Scots pine sawn timber: a multivariate method approach. In: Zbiec M & Orlowski K (Ed.), 23rd International wood machining seminar: proceedings : 28. - 31. 5. 2017, Warsaw, Poland. Paper presented at 23rd International Wood Machining Seminar (IWMS-23), War saw, Poland, May 28-31 2017 (pp. 360-361). Warsaw: Warsaw university of life sciences
Open this publication in new window or tab >>Customer adapted grading of Scots pine sawn timber: a multivariate method approach
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2017 (English)In: 23rd International wood machining seminar: proceedings : 28. - 31. 5. 2017, Warsaw, Poland / [ed] Zbiec M & Orlowski K, Warsaw: Warsaw university of life sciences , 2017, p. 360-361Conference paper, Published paper (Refereed)
Abstract [en]

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

Place, publisher, year, edition, pages
Warsaw: Warsaw university of life sciences, 2017
National Category
Agricultural and Veterinary sciences Wood Science Other Mechanical Engineering
Research subject
Wood Science and Engineering
Identifiers
urn:nbn:se:ltu:diva-65840 (URN)978-83-948046-0-2 (ISBN)
Conference
23rd International Wood Machining Seminar (IWMS-23), War saw, Poland, May 28-31 2017
Available from: 2017-09-26 Created: 2017-09-26 Last updated: 2017-11-24Bibliographically approved
Ah Shenga, P., Bomark, P., Broman, O. & Sandberg, D. (2017). Log sawing positioning optimization and log bucking of tropical hardwood species to increase the volume yield. Wood Material Science & Engineering, 12(4), 257-262
Open this publication in new window or tab >>Log sawing positioning optimization and log bucking of tropical hardwood species to increase the volume yield
2017 (English)In: Wood Material Science & Engineering, ISSN 1748-0272, E-ISSN 1748-0280, Vol. 12, no 4, p. 257-262Article in journal (Refereed) Published
Abstract [en]

The sawmill industry is a very important link in the Mozambique forest products value chain, but the industry is characterized by undeveloped processing technology and high-volume export of almost unrefined logs. The low volume yield of sawn timber has been identified as a critical gap in the technological development of the industry. To improve the profitability of the industry, there is thus a need to develop methods and techniques that improve the yield. In this paper, different positioning of logs prior to sawing and the possibility of increasing the volume yield of crooked logs by bucking the logs before sawing have been studied. A computer simulation was used to study the cant-sawing and through-and-through sawing of the logs to determine the volume yield of sawn timber from the jambirre (Millettia stuhlmannii Taub.) and umbila (Pterocarpus angolensis DC.) species. The optimal position, i.e. the position of the log before sawing that gives the highest volume yield of sawn timber for a given sawing pattern when the positioning parameters, offset, skew and rotation, are considered gave a considerable higher volume yield than the horns-down position. By bucking very crooked logs and using the horns-down positioning before sawing, the volume yield can be of the same magnitude as that obtained by optimal positioning on full-length (un-bucked) logs. The bucking reduces the crook of the logs and hence increases the volume yield of sawn timber.

Place, publisher, year, edition, pages
Taylor & Francis, 2017
National Category
Other Mechanical Engineering
Research subject
Wood Science and Engineering
Identifiers
urn:nbn:se:ltu:diva-61459 (URN)10.1080/17480272.2016.1275788 (DOI)000402709800010 ()2-s2.0-85008622401 (Scopus ID)
Note

Validerad;2017;Nivå 2;2017-06-07 (andbra)

Available from: 2017-01-16 Created: 2017-01-16 Last updated: 2018-07-10Bibliographically approved
Manuel, A., Leonhart, R., Broman, O. & Becker, G. (2016). How do consumers express their appreciation of wood surfaces?: Norway spruce floors in Germany as an example (ed.). Annals of Forest Science, 73(3), 703-712
Open this publication in new window or tab >>How do consumers express their appreciation of wood surfaces?: Norway spruce floors in Germany as an example
2016 (English)In: Annals of Forest Science, ISSN 1286-4560, E-ISSN 1297-966X, Vol. 73, no 3, p. 703-712Article in journal (Refereed) Published
Abstract [en]

Key Message: A variety of visually different floor sam- ples are presented online to consumers. Based on their individual verbal judgements of appreciation for visual surface characteristics, four distinct groups of floor sur- faces were identified. This allows directing design and marketing efforts more precisely towards consumers’ expectations.Context: For high-end wood products, appearance is a key factor. Traditionally, manufacturers grade wood considering technical parameters and industrial customers’ requirements. In contrast, knowing the consumers’ verbal items would be of advantage for both producers and buyers.Aims: Three research questions are identified exploring pos- sibilities to utilize consumers’ appreciations. (1) Is it possible to establish a consistent characterization with verbal items? (2) Can appreciation be linked to visual wood properties? (3) Can the great natural variety of wood surfaces be assigned to de- sirable product groups?Methods: Out of 57 spruce logs, 810 floor boards were pro- duced and sorted into 15 ‘visual classes’ (VC). Images were retrieved and virtual floors composed from each VC. Consumers evaluated selected floor samples in an online sur- vey using a set of 7 items. Hierarchical cluster analysis and discriminant analysis are applied to analyze the answers.Results: Only 4 out of the 7 items (‘vividness’, ‘evenness’, ‘contrast’ and ‘stripes’) were sufficient to allocate the VCs to four groups which represent different consumer appreciations. Inverse assessments of different product groups support a more differentiated marketing.Conclusion: The results indicate that verbal judgements of high-end wood surfaces can hold advantages directing production and marketing efforts more towards consumers’ preferences and thus increasing satisfaction and added value

Keywords
Forestry, agricultural sciences and landscape planning - Wood fibre and forest products, Skogs- och jordbruksvetenskap samt landskapsplanering - Träfiber- och virkeslära
National Category
Other Mechanical Engineering
Research subject
Wood Science and Engineering
Identifiers
urn:nbn:se:ltu:diva-8159 (URN)10.1007/s13595-016-0558-1 (DOI)000380253600013 ()2-s2.0-84979306927 (Scopus ID)6a0d4ab1-0b0f-4619-93a8-b8b4d6017012 (Local ID)6a0d4ab1-0b0f-4619-93a8-b8b4d6017012 (Archive number)6a0d4ab1-0b0f-4619-93a8-b8b4d6017012 (OAI)
Note

Validerad; 2016; Nivå 2; 20160608 (olof); Bibliografisk uppgift: Cite this article as Manuel, A., Leonhart, R., Broman, O. et al. Annals of Forest Science (2016) 73: 703. doi:10.1007/s13595-016-0558-1

Available from: 2016-09-29 Created: 2016-09-29 Last updated: 2019-08-23Bibliographically approved
Ah Shenga, P., Bomark, P., Broman, O. & Sandberg, D. (2016). The Effect of Log Position Accuracy on the Volume Yield in Sawmilling of Tropical Hardwood. BioResources, 11(4), 9560-9571
Open this publication in new window or tab >>The Effect of Log Position Accuracy on the Volume Yield in Sawmilling of Tropical Hardwood
2016 (English)In: BioResources, ISSN 1930-2126, E-ISSN 1930-2126, Vol. 11, no 4, p. 9560-9571Article in journal (Refereed) Published
Abstract [en]

This study investigated the effect of the positioning of the log before sawing on the volume yield of sawn timber from tropical hardwood species. Three positioning parameters were studied, the offset, skew, and rotation, combined with two sawing patterns of cant-sawing and through-and-through sawing. A database consisting of two tropical hardwood species with very different outer shapes, jambirre (Millettia stuhllmannii Taub.) and umbila (Pterocarpus angolensis DC.), was used to simulate the sawing process. The result of the simulation revealed that, according to the combined effect of offset, skew, and rotation positioning, the positioning of the log before sawing is extremely important to achieve a high volume yield of sawn timber. The positioning parameter that has the highest effect on the volume yield is the rotation, and the variation in the volume yield associated with a deviation in the positioning can reduce the volume yield of sawn timber by between 7.7% and 12.5%.

Keywords
Log positioning error, Tropical species, Skew, Offset, Rotation
National Category
Other Mechanical Engineering
Research subject
Wood Science and Engineering
Identifiers
urn:nbn:se:ltu:diva-37010 (URN)10.15376/biores.11.4.9560-9571 (DOI)000391801300108 ()
Note

Validerad; 2016; Nivå 2; 2016-11-23 (andbra)

Available from: 2016-10-03 Created: 2016-10-03 Last updated: 2019-09-11Bibliographically approved
Fredriksson, M., Bomark, P., Broman, O. & Grönlund, A. (2015). A trapeze edging method for cross laminated timber panel production (ed.). In: (Ed.), Roger Hernández; Claudia Cáceres (Ed.), Proceedings of the 22nd International Wood Machining Seminar: . Paper presented at International Wood Machining Seminar : 14/06/2015 - 19/06/2015 (pp. 323-332). Quebec city, Kanada: Universite Laval
Open this publication in new window or tab >>A trapeze edging method for cross laminated timber panel production
2015 (English)In: Proceedings of the 22nd International Wood Machining Seminar / [ed] Roger Hernández; Claudia Cáceres, Quebec city, Kanada: Universite Laval , 2015, p. 323-332Conference paper, Published paper (Refereed)
Place, publisher, year, edition, pages
Quebec city, Kanada: Universite Laval, 2015
National Category
Other Mechanical Engineering
Research subject
Wood Science and Engineering
Identifiers
urn:nbn:se:ltu:diva-30380 (URN)42931d02-f2a2-44c4-985e-2f52f33f5357 (Local ID)978-0-9947964-0-0 (ISBN)42931d02-f2a2-44c4-985e-2f52f33f5357 (Archive number)42931d02-f2a2-44c4-985e-2f52f33f5357 (OAI)
Conference
International Wood Machining Seminar : 14/06/2015 - 19/06/2015
Note

Godkänd; 2015; 20140930 (magfre)

Available from: 2016-09-30 Created: 2016-09-30 Last updated: 2017-11-25Bibliographically approved
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