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Practical trajectory designs for semi-automation of forestry cranes
Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för tillämpad fysik och elektronik.
Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för tillämpad fysik och elektronik.
Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för tillämpad fysik och elektronik.
2016 (engelsk)Inngår i: Proceedings of  ISR 2016: 47th International Symposium on Robotics, VDE Verlag GmbH, 2016, s. 1-8Konferansepaper, Publicerat paper (Fagfellevurdert)
Abstract [en]

Simplifying the operation of forestry machines with operator-centered semi-automation is needed in the modern timber harvesting industry in order to increase operator productivity and comfort, to reduce learning time of novice operators and to ensure safer manipulation of the cranes. In this paper, useful tools towards operator-centered semi-automation of the base joint actuator of a forwarder crane are proposed. The main goal is to allow comfortable automated motions that do not excite dangerous oscillations of the freely-hanging grapple. Moreover, operator commands are used interactively with a closed-loop position control scheme to assure automated slewing motions. Smooth reference trajectories are provided for the position controller with an on-line trajectory generation algorithm that is developed by combining properties of two standard trajectory generation methods. A practical algorithm based on experiments is introduced to find the trajectory that guaranties minimal grapple oscillations within a set of relatively fast trajectories. Further on, the log loading/unloading tasks are discussed and verified experimentally using the proposed approach on a forwarder crane prototype.

sted, utgiver, år, opplag, sider
VDE Verlag GmbH, 2016. s. 1-8
HSV kategori
Forskningsprogram
reglerteknik
Identifikatorer
URN: urn:nbn:se:umu:diva-129523ISBN: 978-3-8007-4231-8 (tryckt)OAI: oai:DiVA.org:umu-129523DiVA, id: diva2:1061187
Konferanse
ISR 2016: 47th International Symposium on Robotics, June 21–22, 2016, Munich, Germany
Tilgjengelig fra: 2016-12-31 Laget: 2016-12-31 Sist oppdatert: 2018-06-09bibliografisk kontrollert
Inngår i avhandling
1. Towards semi-automation of forestry cranes: automated trajectory planning and active vibration damping
Åpne denne publikasjonen i ny fane eller vindu >>Towards semi-automation of forestry cranes: automated trajectory planning and active vibration damping
2017 (engelsk)Doktoravhandling, med artikler (Annet vitenskapelig)
Abstract [en]

Forests represent one of the biggest terrestrial ecosystems of Earth, that can produce important raw renewable materials such as wood with the help of sun, air and water. To efficiently extract these raw materials, the tree harvesting process is highly mechanized in developed countries, meaning that advanced forestry machines are continuously used to fell, to process and to transport the logs and biomass obtained from the forests. However, working with these machines is demanding both mentally and physically, which are known factors to negatively affect operator productivity. Mental fatigue is mostly due to the manual operation of the on-board knuckleboom crane, which requires advanced cognitive work with two joystick levers, while the most serious physical strains arise from cabin vibrations. These vibrations are generated from knuckleboom crane vibrations as a result of aggressive manual operation.

To enhance operator workload, well-being, and to increase productivity of the logging process, semi-automation functions are suggested, which are supervised automatic executions of specific work elements. Some of the related issues are addressed in the current thesis. Therefore, the content is divided into: (1) the design and development of a semi-automation function focused only on the base joint actuator (slewing actuator) of a knuckleboom crane, and (2) active vibration damping solutions to treat crane structure vibrations induced by the main lift cylinder (inner boom actuator). The considered reference machine is a downsized knuckleboom crane of a forwarder machine, which is used to pick up log assortments from a harvesting site.

The proposed semi-automation function presented in the first part could be beneficial for operators to use during log loading/unloading scenarios. It consists from a closed-loop position control architecture, to which smooth reference slewing trajectories are provided by a trajectory planner that is automated via operator commands. The used trajectory generation algorithms are taken from conventional robotics and adapted to semi-automation context with proposed modifications that can be customizable by operators.

Further, the proposed active vibration damping solutions are aimed to reduce vibrations of the knuckleboom crane excited by the inner boom actuator due to aggressive manual commands. First, a popular input shaping control technique combined with a practical switching logic was investigated to deal with the excited payload oscillations. This technique proved to be useful with a fixed crane pose, however it did not provide much robustness in terms of different link configurations. To tackle this problem an H2-optimal controller is developed, which is active in the pressure feedback-loop and its solely purpose is to damp the same payload oscillations. During the design process, operator commands are treated and explained from input disturbance viewpoint.

All of the hypothesis throughout this thesis were verified with extensive experimental studies using the reference machine.

sted, utgiver, år, opplag, sider
Umeå: Umeå universitet, 2017. s. 85
Serie
Robotics and control lab, ISSN 1654-5419 ; 9
Emneord
Forestry, forwarder cranes, semi-automation, slewing actuator, automated trajectory planning, oscillations, inner boom actuator, active vibration damping, frequency estimation, input shaping control technique, H2-optimal control
HSV kategori
Identifikatorer
urn:nbn:se:umu:diva-140256 (URN)978-91-7601-776-0 (ISBN)
Disputas
2017-10-27, N420, Naturvetarhuset, Umeå, 13:00 (engelsk)
Opponent
Veileder
Tilgjengelig fra: 2017-10-06 Laget: 2017-10-04 Sist oppdatert: 2018-06-09bibliografisk kontrollert

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