Kalle Kärhä - Academia.edu (original) (raw)

Papers by Kalle Kärhä

IEEE Access

The use of autonomous systems at wood processing sites of forest industries can significantly inc... more The use of autonomous systems at wood processing sites of forest industries can significantly increase safety, productivity and efficiency by reducing the number of monotonous and dangerous tasks conducted by human labor utilizing heavy machinery. However, autonomous machine operation in mill yards is challenging because of the dynamic and complex working environment and partly unstructured processes. The inherent complexity of wood handling and storage tasks requires significant human expertise. Rapid advancements in sensor technologies and machine learning techniques, along with increases in available computational power have enabled progress in automated operation frameworks and algorithms development, which opens the door to the introduction of novel autonomous systems into this environment. With the aim of gaining a better understanding of current issues and facilitating optimal strategies for the deployment of high-level autonomous systems in mill yard environments, this study: (1) utilizes a systematic literature review to map current autonomous technologies and algorithms suitable for adoption by the forest industry in automation of vehicles working in mill yards; (2) summarizes and discusses the potential feasibility of the considered sensors, systems and adoption strategies, and considers implementation challenges for high-level autonomous machinery in mill yard environments; and (3) proposes a system framework that integrates multiple technologies to enable autonomous navigation and material handling in mill yards. The study is the first of its kind as a comprehensive study on autonomous vehicles and machinery in mill yard environments. Our novel framework aids in the identification of follow-up research areas and thus promotes the adoption and use of complex autonomous systems in industrial environments.

In the context of the Government's Climate and Energy Strategy, it is estimated that the prim... more In the context of the Government's Climate and Energy Strategy, it is estimated that the primary use of wood-based fuels in Finland will be about 100 TWh by the year 2020. The overall target set for forest chips is 25 TWh. The objective of the research carried out by Metsäteho Oy and Pöyry Energy Oy was to produce as realistic as possible a total analysis of the possibilities of increasing the use of solid wood-based fuels, and especially forest chips, in Finland by 2020. The study showed that the growth objective set in the Government's Climate and Energy Strategy can be attained through the supply and consumption of wood-based fuels. The emission trade had a strong influence on the competitiveness of wood-based fuels and the use of such fuels in energy plants. Increasing the proportion of wood-based fuels is very difficult at the current pricing level of emission rights (about 15 €/t CO2). Considering the huge resources required by the forest chip production system and the...

In the new forest management recommendations in Finland, one cultivation alternative for Scots pi... more In the new forest management recommendations in Finland, one cultivation alternative for Scots pine (Pinus sylvestris L.) is intensive cultivation in which the quality of a poor or mediocre pine stand is improved by carrying out an intensive, quality first thinning. This type of thinning leaves ca. 700 trees per hectare. The research conducted by Metsäteho Oy investigated how harvesting conditions and costs change when the thinning intensity is increased and intensive, quality thinning is carried out in firstthinning Scots pine stands. The study showed that the harvesting conditions in intensive, quality thinning are superior, resulting in lower harvesting costs than for normal first thinning. One item of particular note was the drop in cutting costs. Intensive, quality thinning had less of an impact on the forest haulage costs. The reduction in harvesting costs, and especially in the cutting costs, was dependent on the extent to which the average stem size of the trees to be harves...

The research carried out by Metsäteho Oy and Pöyry Management Consulting Oy estimated how much ma... more The research carried out by Metsäteho Oy and Pöyry Management Consulting Oy estimated how much machinery and labour would be needed for large-scale forest chip production if the use of forest chips increased extensively in Finland during the coming decade. If the production and consumption of forest chips are 25 to 30 TWh in Finland in 2020, then 1,900 to 2,200 machinery units, i.e. machines and trucks, would be needed. This would mean total investments in production machinery of 530 to 630 million € (VAT 0%). The labour demand would be 3,400 to 4,000 machine operators and drivers, and 4,200 to 5,100 labour years including indirect labour. The results of the study indicated that forest chip production resources will be a major bottleneck in reaching the consumption target of 25 TWh of forest chips in Finland by 2020.

In Finland, two mechanized harvesting systems are used for small-diameter (d1.3<10 cm) thinnin... more In Finland, two mechanized harvesting systems are used for small-diameter (d1.3<10 cm) thinning wood: 1) the traditional two-machine (harvester and forwarder) system, and 2) the harwarder system (i.e. the same machine performs both cutting and forest haulage to the roadside). There are currently more than 20 energy wood harwarders in use in Finland. However, there have been no comprehensive studies carried out on energy wood harwarders. Metsäteho Oy undertook a study on the two mechanized harvesting systems for small-sized thinning wood. Time study and follow-up study material was collected for the study from whole-tree harvesting using energy wood harwarders and two-machine harvesting systems. The productivity and cost levels of the two main harvesting systems were determined, and the whole-tree harvesting costs for harwarders were compared with those of the conventional two-machine system. The results gave a clear indication of what kind of machine resources can be most profita...

The field studies assessed the competitiveness of industrial roundwood and energy wood procuremen... more The field studies assessed the competitiveness of industrial roundwood and energy wood procurement based on the Fixteri II whole-tree bundler. The objectives of the studies were: i) to analyse the properties of whole-tree bundles and their correlation with stand parameters; ii) to define the productivity of wholetree bundling and the forwarding and long-distance transportation of whole-tree bundles; and iii) to determine the procurement costs of the whole-tree bundling supply chain and to compare these costs with those of other industrial roundwood and energy wood supply chains. The average diameter of the whole-tree bundles measured in the study was 65 cm and the average length 268 cm. The whole-tree bundles harvested from the bundling time-study sample plots averaged a green mass of 476 kg. The average solid volume of the bundles was 495 dm, of which branches accounted for 17% on average. The whole-tree bundle size increased in line with increase in average stem size of removals. ...

Currently, the total number of harwarders in industrial roundwood and energy wood harvesting in F... more Currently, the total number of harwarders in industrial roundwood and energy wood harvesting in Finnish forests is slightly over one hundred. Metsäteho Oy conducted a follow-up study of harwarders in industrial roundwood harvesting in Finland, and also investigated the transfers of the harwarders. In the study of Metsäteho, the possibilities of harwarder systems in wood harvesting in the near future in Finland were also evaluated. It was forecasted that the number of harwarders will significantly increase in the near future in Finland; within a few years, the number of harwarders engaged in industrial roundwood and energy wood harvesting may even be as much as 200–300. This development forecast is based on the following factors: I) Cost effectiveness in wood harvesting is being sought at the level of the stand marked for harvesting, as well as from the point of view of the forest machine business. II) The structural change in cuttings is setting new demands on the harvesting machine...

The effect of different pre-clearance methods on future harvesting conditions and the clearance c... more The effect of different pre-clearance methods on future harvesting conditions and the clearance costs were studied. In addition, the effect of undergrowth and pre-clearance methods on the work productivity, costs, and silvicultural result of the winter and summer harvesting of first-thinning Scots pine (Pinus sylvestris) stands, as well as the profitability of the pre-clearance, were analysed. Four different pre-clearance methods were tested in the study. Even first-thinning wood was harvested on some uncleared research plots. The density and average height of the Norway spruce (Picea abies) undergrowth were found to have a significant effect on the cutting productivity. The density of spruce undergrowth also affected the forwarding productivity. The undergrowth density and height, or pre-clearance method, had no effect on the silvicultural result. The density and average height of the spruce undergrowth, the size of the trees to be harvested, the roundwood removal, and the costs of...

Annals of Forest Research, 2018

Cut-to-length harvesting is a cost-efficient method of the wood supply chain. However, it risks c... more Cut-to-length harvesting is a cost-efficient method of the wood supply chain. However, it risks causing stem damage in the mechanized process of thinning forest stands, thereby reducing the growth and technical quality of the remaining trees, which would then be exposed on the increased vulnerability to fungal diseases. For these reasons, it is critical to support quality monitoring of harvesting machines. One way to support quality monitoring is through the application of machine vision solutions. In this study, the damaged stems were photographed systematically from a strip road. The success of the stem-damage detection was analyzed to determine the relationships between successful detection, stand condition, and the image-processing technique. Statistically meaningful relationships were identified via logistic regression analysis, which can be used in selection of tailored image processing technique. The study indicated that the quality-monitoring system of mechanized harvesting ...

In order to speed up the production of small-sized thinning wood chips in young stands, the Finni... more In order to speed up the production of small-sized thinning wood chips in young stands, the Finnish State provides financial incentives for the production of small-diameter wood chips. Financial support is provided according to the Sustainable Silviculture Foundation Law (Kemera). Currently (Summer 2008), the Kemera support provides subsidies for smallsized wood chips in early thinnings 7-10 €/MWh maximum in typical harvesting conditions (whole-tree chip removal 40-70 m 3 /ha, and average stem size of removal 10-40 dm 3). Metsäteho Oy undertook a study on the total production costs of small-sized thinning wood chips with and without the Kemera supports. The results gave a clear indication that small-sized wood chips cannot currently be produced without the Kemera supports from young stands with typical harvesting conditions. If operating without the Kemera supports, the average stem size of whole trees harvested must be greater than 80 dm 3 , at the current price level of small-diameter wood chips in order for the harvesting of small-diameter energy wood from young stands to be economically profitable in Finland.

Annals of Forest Science, 2020

Key message We examined the accuracy of the stand attribute data based on airborne laser scanning... more Key message We examined the accuracy of the stand attribute data based on airborne laser scanning (ALS) provided by the Finnish Forest Centre. The precision of forest inventory data was compared for the first time with operative logging data measured by the harvester. Context Airborne laser scanning (ALS) is increasingly used together with models to predict the stand attributes of boreal forests. The information is updated by growth models. Information produced by remote sensing, model prediction, and growth simulation needs field verification. The data collected by harvesters on logging sites provide a means to evaluate and verify the accuracy of the ALS-based data. Aims This study investigated the accuracy of ALS-based forest inventory data provided by the Finnish Forest Centre at the stand level, using harvester data as the reference. Special interest was on timber assortment volumes where the quality reductions of sawlog are model predictions in ALS-based data and true realized ...

European Journal of Forest Research, 2020

Small tree size represents the main challenge when designing a cost-effective harvesting system f... more Small tree size represents the main challenge when designing a cost-effective harvesting system for European short-rotation plantations. This challenge is further complicated by the need to obtain 4-m logs for high-end products, which rules out the possibility of deploying whole-tree chipping. Both challenges can be met through mass or multi-tree handling (MTH), which must begin at the time of felling and continue uninterrupted along the whole supply chain. The objective was to: (1) gauge the productivity and the cost of CTL harvesting applied to these plantations; (2) assess log yield and capacity to match dimensional specifications; (3) determine if MTH applied to CTL technology offers a real benefit compared with conventional single-tree handling. The authors conducted a time study using a block design with a two-machine cut-to-length harvesting system (i.e. harvester and forwarder) in single- and multi-tree handling operations on the clear cutting of a hybrid poplar plantation i...

Croatian journal of forest engineering, 2021

The EU’s climate and energy framework and Energy Efficiency Directive drive European companies to... more The EU’s climate and energy framework and Energy Efficiency Directive drive European companies to improve their energy efficiency. In Finland, the aim is to achieve carbon neutrality by 2035. Stora Enso Wood Supply Finland (WSF) had a target, by 2020, to improve its energy efficiency by 4% from the 2015 level. This case study researches the use of the forest machine fleet contracted to Stora Enso WSF. The aims were to 1) clarify the forest machine fleet energy-efficiency as related to the engine power; 2) determine the fuel consumption and greenhouse gas (GHG) emissions from wood-harvesting operations, including relocations of forest machines by trucks; and 3) investigate the energy efficiency of wood-harvesting operations. The study data consisted of Stora Enso WSF’s industrial roundwood harvest of 8.9 million m3 (solid over bark) in 2016. The results illustrated that forest machinery was not allocated to the different cutting methods (thinning or final felling) based on the engine...

European Journal of Forest Engineering, 2020

The objective of this study was to analyze forest industry professionals’ opinions of the utility... more The objective of this study was to analyze forest industry professionals’ opinions of the utility of pre-clearance work prior to the first-thinning operations. A total of 153 interviews were conducted with three groups of professionals (forest machine entrepreneurs, harvester operators and logging officers) with a response rate of 80%. In general, the respondents agreed that the occurrence of understory would hinder the cutting work if the softwood tree understory density exceeded 1,152 trees/ha and a height of 1.42 m. The corresponding values for broadleaved trees were 1,669 trees/ha and a height of 1.86 m. The respondents stated that trees eligible for logging should be pre-cleared within a circular area with a mean radius of 1.24 m, and the stump height of cleared trees should not exceed 10.8 cm. In intermediate areas (i.e., outside of the circular areas) understory trees exceeding a height of 1.96 m should be pre-cleared. Pre-harvest clearing should be conducted, on average, 9.2...

International Journal of Advanced Engineering Research and Science, 2018

In this study, timber trade scenarios are considered in a wood procurement region of Finland. Thi... more In this study, timber trade scenarios are considered in a wood procurement region of Finland. This multiple objective decision-making situation includes the timber purchase from forest owners and the lumber sales from sawmill to abroad. The situation is further complicated by a number of stem bucking instructions of sawmill during different periods. In practice, this decision problem has been solved by applying single-objective stem bucking instructions in harvesters. Due to the complex nature of the problem, single-objective solution can't be directly used to support the timber trade in a manner that it is techno-economically relevant to the forest owners and industries. In this study, stand parameters and timber trade attributes were measured in local wood procurement conditions to improving the bucking instructions. Three scenarios of how the simulation system works based on the real stem diameters and optional monetary value of logs are investigated in the timber-trade process. The Finnish timber trade market is subjected to agreements regarding stem bucking regulations. These agreements could be made on the basis of the three criteria suggested in this study accounting for the effects of stand classification on the timber sales of forest owners and the lumber sales of export companies. Keywords-cut-to-length method, forest industry, forest owner, multi-criteria analysis, stem bucking, wood procurement. I.

Forests, 2019

Research Highlights: This study offers new information on the cross cutting of decayed stems with... more Research Highlights: This study offers new information on the cross cutting of decayed stems with the sounding of short (0.5 m) offcuts and the bucking of longer (3.0 m) butt-rotten poles. Background and Objectives: The root and butt-rot fungus Heterobasidion annosum sensu lato (Fr.) Bref. causes wood quality damage to trees in softwood forests. When timber is harvested in butt-rotten forests, it is essential that the decayed part of the tree is recognized and cut away from a stem, while the healthy and good quality log section of a stem is cross cut with precision sawlogs. The objective of the study was to investigate the impact of two off-cutting methods on stem processing time, cutting productivity, sawlog volume, and commercial value at the roadside landing when harvesting timber from the butt-rotten Norway spruce (Picea abies (L.) Karst.) final-felling forests. Materials and Methods: The length of the short offcuts used was 0.5 m. The results of the cross-cutting practices were...

International Journal of Forest Engineering, 2005

The felling and bunching of small diameter trees in Finland is still largely carried out manually... more The felling and bunching of small diameter trees in Finland is still largely carried out manually using a chain saw and clearing saw. The felling of small diameter trees has been developed and mechanized. In addition to the high felling costs of small trees, the move towards mechanized harvesting is also caused by a shortage of professional lumberjacks, the possibility of all-year-round mechanized energy wood harvesting, and an increasing demand for energy wood.

International Journal of Forest Engineering, 2004

High harvesting costs are the main problems in first thinnings. Machines with lower operating cos... more High harvesting costs are the main problems in first thinnings. Machines with lower operating costs could be one potential solution for cost-efficient first thinnings. The research investigated the productivity of the four most widely used small harvesters, i.e. thinning harvesters, and their cutting costs. Data were also collected on the productivity relationships between working methods and the differences between operators. In the time studies involving thinning harvesters, the Nokka Profi and Timberjack 770 represented the larger, more expensive machines, while the Sampo-Rosenlew 1046X and Valtra Forest 120 represented the more compact, less expensive thinning harvesters. The productivity per operating hour (E 15 including delay times shorter than 15 minutes) of the thinning harvesters was found to be 5.6-10.3 m 3 / E 15 (stem size 50-100 dm 3) in first thinnings and 9.1-12.7 m 3 / E 15 (100-150 m 3) in second thinnings. The productivity figures of the individual machines were similar. The differences were mainly attributable to the operators. The time study showed that the differences between operators using the same machines were as great as 40%. The cutting costs for the thinning harvesters were 7.5-14.2 US$/m 3 (50-100 dm 3) in first thinnings when using the Nokka/Timberjack machine group. The corresponding costs for the Sampo/Valtra machine group were 5.7 and 10.5 US$/m 3. It would appear that thinning harvesters can be operated at the same productivity level of medium-sized harvesters in thinnings and, consequently, they can be run at cutting costs lower than those of medium-sized harvesters.

Computers and Electronics in Agriculture, 2019

The machine vision-based mobile Trestima Stack application was a more accurate and faster measuri... more The machine vision-based mobile Trestima Stack application was a more accurate and faster measuring method than a conventional stacked timber measurement. • The measurement difference of Trestima Stack had a better average in large terminal yards (+0.6%) than at roadside landings (+4.5%). • For both measurement methods, there was a negative correlation between the stack size and the volume-based effective total measurement time consumption. • Trestima Stack can be recommended for inventorying timber stacks at roadside landings, particularly when the stacks measured consist of several measurement batches.