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Interactive on-line trajectories for semi-automation: case study of a forwarder crane
Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
2016 (English)In: Proceedings of 2016 IEEE International Conference on Automation Science and Engineering (CASE), IEEE, 2016, p. 928-933Conference paper, Published paper (Refereed)
Abstract [en]

Working with forestry cranes is not easy due to their complex mechanical structure, non-linear behavior of the hydraulic actuation system, and non-intuitive joint-based control; however, with automation, the level of manipulation difficulty can be reduced. This is potentially useful for the operators since they are prone to be more productive if semi-automation functions are introduced to a certain level. In this paper, a semi-automation function for the base joint actuator of a forestry forwarder crane is proposed. The semi-automation function is based on a design of an interactive on-line trajectory generation algorithm with variable final time that acts as a reference signal to a closed-loop position controller. Moreover, the advantage of this scheme is that the operators are kept in the loop by directly being in charge of controlling the final time for the on-line trajectory generation algorithm. Experiments with a downsized industry-standard forwarder crane verify the applicability and advantage of the proposed scheme.

Place, publisher, year, edition, pages
IEEE, 2016. p. 928-933
Keyword [en]
trajectory control, closed loop systems, cranes, forestry, hydraulic actuators
National Category
Control Engineering Robotics
Research subject
Automatic Control
Identifiers
URN: urn:nbn:se:umu:diva-129520DOI: 10.1109/COASE.2016.7743502ISBN: 978-1-5090-2409-4 (electronic)OAI: oai:DiVA.org:umu-129520DiVA, id: diva2:1061188
Conference
2016 IEEE International Conference on Automation Science and Engineering (CASE), 21-25 August, 2016, Forth Worth, Texas, USA
Available from: 2016-12-31 Created: 2016-12-31 Last updated: 2018-06-09Bibliographically approved
In thesis
1. Towards semi-automation of forestry cranes: automated trajectory planning and active vibration damping
Open this publication in new window or tab >>Towards semi-automation of forestry cranes: automated trajectory planning and active vibration damping
2017 (English)Doctoral thesis, comprehensive summary (Other academic)
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.

Place, publisher, year, edition, pages
Umeå: Umeå universitet, 2017. p. 85
Series
Robotics and control lab, ISSN 1654-5419 ; 9
Keyword
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
National Category
Control Engineering Robotics
Identifiers
urn:nbn:se:umu:diva-140256 (URN)978-91-7601-776-0 (ISBN)
Public defence
2017-10-27, N420, Naturvetarhuset, Umeå, 13:00 (English)
Opponent
Supervisors
Available from: 2017-10-06 Created: 2017-10-04 Last updated: 2018-06-09Bibliographically approved

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Fodor, SzabolcsVázquez, CarlosFreidovich, Leonid

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Citation style
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