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Towards semi-automation of forestry cranes: automated trajectory planning and active vibration damping
Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för tillämpad fysik och elektronik.
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. , 85 s.
Serie
Robotics and control lab, ISSN 1654-5419 ; 9
Emneord [en]
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: urn:nbn:se:umu:diva-140256ISBN: 978-91-7601-776-0 (tryckt)OAI: oai:DiVA.org:umu-140256DiVA: diva2:1146828
Disputas
2017-10-27, N420, Naturvetarhuset, Umeå, 13:00 (engelsk)
Opponent
Veileder
Tilgjengelig fra: 2017-10-06 Laget: 2017-10-04 Sist oppdatert: 2017-10-13bibliografisk kontrollert
Delarbeid
1. Automation of slewing motions for forestry cranes
Åpne denne publikasjonen i ny fane eller vindu >>Automation of slewing motions for forestry cranes
2015 (engelsk)Inngår i: 2015 15th International Conference on Control, Automation and Systems (ICCAS), IEEE, 2015, 796-801 s.Konferansepaper, Publicerat paper (Fagfellevurdert)
Abstract [en]

The modern timber harvesting industry would be ineffective without heavy duty advanced machinery used for logging. However, with benefits of mechanization comes the operation complexity. Introducing automation is expected to reduce the mental and physical load on the operator and improve the machine use efficiency. Nonetheless, with current technology fully autonomous timber harvesting is impossible. In this paper a semi-automation scenario is presented using the base joint actuator of a forestry forwarder crane taking into consideration the need to attenuate unwanted oscillations of its hanging grapple. We address the necessary motion planning and motion stabilization tasks. To reduce oscillations along a nominal trajectory, we design smooth reference profiles based on experiments. Meanwhile, a practical structure for a feedback controller is proposed and tested. In this process, actuator nonlinearities are dealt with feasible identification and compensation techniques.

sted, utgiver, år, opplag, sider
IEEE, 2015
Serie
International Conference on Control Automation and Systems, ISSN 2093-7121
Emneord
automation, forestry cranes, input nonlinearity, trajectory design, identification
HSV kategori
Forskningsprogram
reglerteknik
Identifikatorer
urn:nbn:se:umu:diva-113791 (URN)000382295200164 ()978-8-9932-1509-0 (ISBN)
Konferanse
15th International Conference on Control, Automation and Systems (ICCAS 2015) Oct. 13-16,2015 in BEXCO, Busan, Korea
Tilgjengelig fra: 2015-12-31 Laget: 2015-12-31 Sist oppdatert: 2017-10-04bibliografisk kontrollert
2. Practical trajectory designs for semi-automation of forestry cranes
Åpne denne publikasjonen i ny fane eller vindu >>Practical trajectory designs for semi-automation of forestry cranes
2016 (engelsk)Inngår i: Proceedings of  ISR 2016: 47th International Symposium on Robotics, VDE Verlag GmbH, 2016, 1-8 s.Konferansepaper, 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
HSV kategori
Forskningsprogram
reglerteknik
Identifikatorer
urn:nbn:se:umu:diva-129523 (URN)978-3-8007-4231-8 (ISBN)
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: 2017-10-04bibliografisk kontrollert
3. Interactive on-line trajectories for semi-automation: case study of a forwarder crane
Åpne denne publikasjonen i ny fane eller vindu >>Interactive on-line trajectories for semi-automation: case study of a forwarder crane
2016 (engelsk)Inngår i: Proceedings of 2016 IEEE International Conference on Automation Science and Engineering (CASE), IEEE, 2016, 928-933 s.Konferansepaper, Publicerat paper (Fagfellevurdert)
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.

sted, utgiver, år, opplag, sider
IEEE, 2016
Emneord
trajectory control, closed loop systems, cranes, forestry, hydraulic actuators
HSV kategori
Forskningsprogram
reglerteknik
Identifikatorer
urn:nbn:se:umu:diva-129520 (URN)10.1109/COASE.2016.7743502 (DOI)978-1-5090-2409-4 (ISBN)
Konferanse
2016 IEEE International Conference on Automation Science and Engineering (CASE), 21-25 August, 2016, Forth Worth, Texas, USA
Tilgjengelig fra: 2016-12-31 Laget: 2016-12-31 Sist oppdatert: 2017-10-04bibliografisk kontrollert
4. Towards oscillation reduction in forestry cranes
Åpne denne publikasjonen i ny fane eller vindu >>Towards oscillation reduction in forestry cranes
2016 (engelsk)Inngår i: Proceedings of the Bath/ASME 2016 Symposium on Fluid Power and Motion Control, ASME Press, 2016, V001T01A049Konferansepaper, Publicerat paper (Fagfellevurdert)
Abstract [en]

Smooth operation of heavy-duty forestry cranes is not an easy task for the operators with the current joystick-based control method that is complex and non-intuitive. Moreover, abrupt movements of the same joysticks provoke aggressive signals that can lead to oscillatory motions in the actuators and in the entire crane. These oscillations, not only contribute to wear of the joint actuators but also can cause damage to both the operators and the environment; therefore, they must be attenuated. The proposed approach in this paper uses the popular input shaping control technique combined with a practical switching logic to deal with different frequency payload oscillations induced by the motion of the inner boom actuator of a forwarder crane. The results show a significant improvement in terms of visible oscillation reduction monitored through their appearance in the torque signal computed from pressure measurements. Experiments performed on a down-sized forestry crane verifies the effectiveness of the approach.

sted, utgiver, år, opplag, sider
ASME Press, 2016
HSV kategori
Forskningsprogram
reglerteknik
Identifikatorer
urn:nbn:se:umu:diva-129521 (URN)10.1115/FPMC2016-1792 (DOI)000389092900049 ()978-0-7918-5006-0 (ISBN)
Konferanse
Bath/ASME symposium on fluid power and motion control, FPMC 2016, September 7-9, 2016, University of Bath, UK
Tilgjengelig fra: 2016-12-31 Laget: 2016-12-31 Sist oppdatert: 2017-10-04bibliografisk kontrollert
5. Active vibration damping using H2-optimal feedback control design for forestry cranes
Åpne denne publikasjonen i ny fane eller vindu >>Active vibration damping using H2-optimal feedback control design for forestry cranes
(engelsk)Manuskript (preprint) (Annet vitenskapelig)
Abstract [en]

Nowadays, forest harvesting is highly mechanized. The commercially available forestry machines are equipped with knuckleboom cranes that are hydraulically actuated, and manually controlled through a set of joysticks and buttons. A common problem that human operators face during manipulation of such knuckleboom cranes, are the crane structure oscillations created by non-smooth or too aggressive manual joystick-based commands. These oscillations not only contribute to actuator wear, but are also dangerous for operators and the environment as well. The current paper investigates the oscillation attenuation induced by the motion of the inner boom actuator and is based on H2-optimal controller synthesis active in the pressure feedback loop. Furthermore, the controller robustness is verified experimentally considering different working conditions of the reference machine, which also verifies the effectiveness of the approach. 

HSV kategori
Forskningsprogram
reglerteknik
Identifikatorer
urn:nbn:se:umu:diva-140252 (URN)
Tilgjengelig fra: 2017-10-03 Laget: 2017-10-03 Sist oppdatert: 2017-10-04

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