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| 2. |
- Lindroos, Ola, et al.
(author)
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Estimating the position of the harvester head : a key step towards the precision forestry of the future?
- 2015
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In: Croatian Journal of Forest Engineering. - Zagreb : University of Zagreb. - 1845-5719 .- 1848-9672. ; 36:2, s. 147-164
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Journal article (peer-reviewed)abstract
- Modern harvesters are technologically sophisticated, with many useful features such as the ability to automatically measure stem diameters and lengths. This information is processed in real time to support value optimization when cutting stems into logs. It can also be transferred from the harvesters to centralized systems and used for wood supply management. Such information management systems have been available since the 1990s in Sweden and Finland, and are constantly being upgraded. However, data on the position of the harvester head relative to the machine are generally not recorded during harvesting. The routine acquisition and analysis of such data could offer several opportunities to improve forestry operations and related processes in the future. Here, we analyze the possible benefits of having this information, as well as the steps required to collect and process it. The benefits and drawbacks of different sensing technologies are discussed in terms of potential applications, accuracy and cost. We also present the results of preliminary testing using two of the proposed methods. Our analysis indicates that an improved scope for mapping and controlling machine movement is the main benefit that is directly related to the conduct of forestry operations. In addition, there are important indirect benefits relating to ecological mapping. Our analysis suggests that both of these benefits can be realized by measuring the angles of crane joints or the locations of crane segments and using the resulting information to compute the head's position. In keeping with our findings, two companies have recently introduced sensor equipped crane solutions.
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| 3. |
- Ringdahl, Ola, 1971-, et al.
(author)
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Enhanced Algorithms for Estimating Tree Trunk Diameter Using 2D Laser Scanner
- 2013
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In: Remote Sensing. - Basel : MDPI. - 2072-4292. ; 5:10, s. 4839-4856
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Journal article (peer-reviewed)abstract
- Accurate vehicle localization in forest environments is still an unresolved problem. Global navigation satellite systems (GNSS) have well known limitations in dense forest, and have to be combined with for instance laser based SLAM algorithms to provide satisfying accuracy. Such algorithms typically require accurate detection of trees, and estimation of tree center locations in laser data. Both these operations depend on accurate estimations of tree trunk diameter. Diameter estimations are important also for several other forestry automation and remote sensing applications. This paper evaluates several existing algorithms for diameter estimation using 2D laser scanner data. Enhanced algorithms, compensating for beam width and using multiple scans, were also developed and evaluated. The best existing algorithms overestimated tree trunk diameter by ca. 40%. Our enhanced algorithms, compensating for laser beam width, reduced this error to less than 12%.
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| 4. |
- Ringdahl, Ola, 1971-, et al.
(author)
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Estimating wheel slip for a forest machine using RTK-DGPS
- 2012
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In: Journal of terramechanics. - : Elsevier BV. - 0022-4898 .- 1879-1204. ; 49:5, s. 271-279
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Journal article (peer-reviewed)abstract
- Wheel slip may increase the risk for wheel rutting and tear up ground vegetation and superficial roots and thereby decreasing the bearing capacity of the ground, but also reducing the growth of nearby standing forest trees. With increased slip, more energy is consumed for making wheel ruts in the ground, with increased fuel consumption as a result. This paper proposes a novel method for measuring slip in an uneven forest terrain with an 8WD forestry machine. This is done by comparing the wheel velocity reported by the machine and velocity measured with an accurate DGPS system. Field tests with a forestry machine showed that slip could be calculated accurately with the suggested method. The tests showed that there was almost no slip on asphalt or gravel surfaces. In a forest environment, 10–15% slip was common. A future extension of the method enabling estimation of the slip of each wheel pair in the bogies is also suggested.
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| 5. |
- Ringdahl, Ola, 1971-, et al.
(author)
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Path tracking in forest terrain by an autonomous forwarder
- 2011
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In: Scandinavian Journal of Forest Research. - : Taylor & Francis. - 0282-7581 .- 1651-1891. ; 26:4, s. 350-359
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Journal article (peer-reviewed)abstract
- Autonomous navigation in forest terrain, where operation paths are rarely straight or flat and obstacles are common, is challenging. This paper evaluates a system designed to autonomously follow previously demonstrated paths in a forest environment without loading/unloading timber, a pre-step in the development of fully autonomous forwarders. The system consisted of a forwarder equipped with a high-precision global positioning system to measure the vehicle’s heading and position. A gyro was used to compensate for the influence of the vehicle’s roll and pitch. On an ordinary clear-cut forest area with numerous stumps, the vehicle was able to follow two different tracks, three times each at a speed of 1 m s-1, with a mean path tracking error of 6 and 7 cm, respectively. The error never exceeded 35 cm, and in 90% of the observations it was less than 14 and 15 cm, respectively. This accuracy is well within the necessary tolerance for forestry operations. In fact, a human operator would probably have a hard time following the track more accurately. Hence, the developed systems function satisfactorily when using previously demonstrated paths. However, further research on planning new paths in unknown unstructured terrain and on loading/unloading is required before timber transports can be fully automated.
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| 6. |
- Ringdahl, Ola, 1971-, et al.
(author)
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Potentials of possible machine systems for directly loading logs in cut-to-length harvesting
- 2012
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In: Canadian Journal of Forest Research. - : Canadian Science Publishing. - 0045-5067 .- 1208-6037. ; 42:5, s. 970-985
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Journal article (peer-reviewed)abstract
- In conventional mechanized cut-to-length systems, a harvester fells and cuts trees into logs that are stored on the ground until a forwarder picks them up and carries them to landing sites. A proposed improvement is to place logs directly into the load spaces of transporting machines as they are cut. Such integrated loading could result in cost reductions, shorter lead times from stump to landing, and lower fuel consumption. However, it might also create waiting times for the machines involved, whereas multifunctional machines are likely to be expensive. Thus, it is important to analyze whether or not the advantages of any changes outweigh the disadvantages. The conventional system was compared with four potential systems, including two with autonomous forwarders, using discrete-event simulation with stochastic elements in which harvests of more than 1000 final felling stands (containing in total 1.6 million m3) were simulated 35 times per system. The results indicate that harwarders have substantial potential (less expensive on ≥80% of the volume and fuel consumption decreased by ≥18%) and may become competitive if key innovations are developed. Systems with cooperating machines have considerably less potential, limited to very specific stand conditions. The results conform with expected difficulties in integrating processing and transporting machines’ work in variable environments.
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| 7. |
- Arad, Boaz, et al.
(author)
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Development of a sweet pepper harvesting robot
- 2020
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In: Journal of Field Robotics. - : John Wiley & Sons. - 1556-4959 .- 1556-4967. ; 37:6, s. 1027-1039
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Journal article (peer-reviewed)abstract
- This paper presents the development, testing and validation of SWEEPER, a robot for harvesting sweet pepper fruit in greenhouses. The robotic system includes a six degrees of freedom industrial arm equipped with a specially designed end effector, RGB-D camera, high-end computer with graphics processing unit, programmable logic controllers, other electronic equipment, and a small container to store harvested fruit. All is mounted on a cart that autonomously drives on pipe rails and concrete floor in the end-user environment. The overall operation of the harvesting robot is described along with details of the algorithms for fruit detection and localization, grasp pose estimation, and motion control. The main contributions of this paper are the integrated system design and its validation and extensive field testing in a commercial greenhouse for different varieties and growing conditions. A total of 262 fruits were involved in a 4-week long testing period. The average cycle time to harvest a fruit was 24 s. Logistics took approximately 50% of this time (7.8 s for discharge of fruit and 4.7 s for platform movements). Laboratory experiments have proven that the cycle time can be reduced to 15 s by running the robot manipulator at a higher speed. The harvest success rates were 61% for the best fit crop conditions and 18% in current crop conditions. This reveals the importance of finding the best fit crop conditions and crop varieties for successful robotic harvesting. The SWEEPER robot is the first sweet pepper harvesting robot to demonstrate this kind of performance in a commercial greenhouse.
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| 8. |
- Barth, Ruud, et al.
(author)
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Using ROS for agricultural robotics : design considerations and experiences
- 2014
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In: RHEA-2014. ; , s. 509-518
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Conference paper (peer-reviewed)abstract
- We report on experiences of using the ROS middleware for developmentof agricultural robots. We describe software related design considerations for all maincomponents in developed subsystems as well as drawbacks and advantages with thechosen approaches. This work was partly funded by the European Commission(CROPS GA no 246252).
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| 9. |
- Bontsema, Jan, et al.
(author)
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CROPS : Clever Robots for Crops
- 2015
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In: Engineering & Technology Reference. - : Institution of Engineering and Technology (IET). - 2056-4007. ; 1:1
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Journal article (peer-reviewed)abstract
- In the EU-funded CROPS project robots are developed for site-specific spraying and selective harvesting of fruit and fruit vegetables. The robots are being designed to harvest crops, such as greenhouse vegetables, apples, grapes and for canopy spraying in orchards and for precision target spraying in grape vines. Attention is paid to the detection of obstacles for autonomous navigation in a safe way in plantations and forests. For the different applications, platforms were built. Sensing systems and vision algorithms have been developed. For software the Robot Operating System is used. A 9 degrees of freedom manipulator was designed and tested for sweet-pepper harvesting, apple harvesting and in close range spraying. For the applications different end-effectors were designed and tested. For sweet pepper a platform that can move in between the crop rows on the common greenhouse rail system which also serves as heating pipes was built. The apple harvesting platform is based on a current mechanical grape harvester. In discussion with growers so-called ‘walls of fruit trees’ have been designed which bring robots closer to the practice. A canopy-optimised sprayer has been designed as a trailed sprayer with a centrifugal blower. All the applications have been tested under practical conditions.
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