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Semi-Automating Forestry Machines: Motion Planning, System Integration, and Human-Machine Interaction
Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics. (Robotics and Control Lab)
2014 (English)Doctoral thesis, comprehensive summary (Other academic)Alternative title
Delautomatisering av skogsmaskiner : Rörelseplanering, systemintegration och människa-maskin-interaktion (Swedish)
Abstract [en]

The process of forest harvesting is highly mechanized in most industrialized countries, with felling and processing of trees performed by technologically advanced forestry machines. However, the maneuvering of the vehicles through the forest as well as the control of the on-board hydraulic boom crane is currently performed through continuous manual operation. This complicates the introduction of further incremental productivity improvements to the machines, as the operator becomes a bottleneck in the process. A suggested solution strategy is to enhance the production capacity by increasing the level of automation. At the same time, the working environment for the operator can be improved by a reduced workload, provided that the human-machine interaction is adapted to the new automated functionality.

The objectives of this thesis are 1) to describe and analyze the current logging process and to locate areas of improvements that can be implemented in current machines, and 2) to investigate future methods and concepts that possibly require changes in work methods as well as in the machine design and technology. The thesis describes the development and integration of several algorithmic methods and the implementation of corresponding software solutions, adapted to the forestry machine context. Following data recording and analysis of the current work tasks of machine operators, trajectory planning and execution for a specific category of forwarder crane motions has been identified as an important first step for short term automation. Using the method of path-constrained trajectory planning, automated crane motions were demonstrated to potentially provide a substantial improvement from motions performed by experienced human operators. An extension of this method was developed to automate some selected motions even for existing sensorless machines. Evaluation suggests that this method is feasible for a reasonable deviation of initial conditions.

Another important aspect of partial automation is the human-machine interaction. For this specific application a simple and intuitive interaction method for accessing automated crane motions was suggested, based on head tracking of the operator. A preliminary interaction model derived from user experiments yielded promising results for forming the basis of a target selection method, particularly when combined with some traded control strategy. Further, a modular software platform was implemented, integrating several important components into a framework for designing and testing future interaction concepts. Specifically, this system was used to investigate concepts of teleoperation and virtual environment feedback. Results from user tests show that visual information provided by a virtual environment can be advantageous compared to traditional video feedback with regards to both objective and subjective evaluation criteria.

Place, publisher, year, edition, pages
Umeå: Umeå Universitet , 2014. , 56 p.
Robotics and control lab, ISSN 1654-5419 ; 6
Keyword [en]
Forestry Robotics, Forest Machine Automation, Trajectory Planning, Hydraulic Manipulators, Teleoperation, Virtual Environments, Interaction Methods, Head Tracking
National Category
URN: urn:nbn:se:umu:diva-89067ISBN: 978-91-7601-061-7OAI: diva2:718380
Public defence
2014-06-11, MIT-huset, MA121, Umeå, 13:00 (English)
Available from: 2014-05-21 Created: 2014-05-20 Last updated: 2014-05-20Bibliographically approved
List of papers
1. Analysis of human-operated motions and trajectory replanning for kinematically redundant manipulators
Open this publication in new window or tab >>Analysis of human-operated motions and trajectory replanning for kinematically redundant manipulators
2009 (English)In: 2009 IEEE/RSJ International Conference on Intelligent Robots and Systems: St.Louis, USA, 2009, 795-800 p.Conference paper (Refereed)
Abstract [en]

We consider trajectory planning for kinematically redundant manipulators used on forestry machines. The analysis of recorded data from human operation reveals that the driver does not use the full potential of the machine due to the complexity of the manipulation task. We suggest an optimization procedure that takes advantage of the kinematic redundancy so that time-efficient joint and velocity profiles along the path can be obtained. Differential constraints imposed by the manipulator dynamics are accounted for by employing a phase-plane technique for admissible path timings. Velocity constraints of the individual joints are particularly restrictive in hydraulic manipulators. Our study aims for semi-autonomous schemes that can provide assistance to the operator for executing global motions.

Motion Planning, Kinematically Redundant Manipulators, Robotics in Agriculture and Forestry
National Category
Other Electrical Engineering, Electronic Engineering, Information Engineering
Research subject
Automatic Control
urn:nbn:se:umu:diva-30078 (URN)
IROS 2009
Available from: 2009-12-03 Created: 2009-12-03 Last updated: 2014-05-20Bibliographically approved
2. Increasing the level of automation in the forestry logging process with crane trajectory planning and control
Open this publication in new window or tab >>Increasing the level of automation in the forestry logging process with crane trajectory planning and control
Show others...
2014 (English)In: Journal of Field Robotics, ISSN 1556-4959, E-ISSN 1556-4967, Vol. 31, no 3, 343-363 p.Article in journal (Refereed) Published
Abstract [en]

Working with forestry machines requires great amount of training to be sufficiently skilledto operate forestry cranes. In view of this, introducing automated motions, as those seenin robotic arms, is ambitioned by this industry for shortening the amount of training timeand make the work of the operator easier. Motivated by this fact, we have developedtwo experimental platforms for testing control systems and motion planning algorithms inreal-time. They correspond to a laboratory setup and a commercial version of a hydraulicmanipulator used in forwarder machines. The aim of this article is to present the results ofthis development by providing an overview of our trajectory planning algorithm and motioncontrol method, with a subsequent view of the experimental results. For motion control,we design feedback controllers that are able to track reference trajectories based on sensormeasurements. Likewise, we provide arguments to design controllers in open-loop for thecase of machines lacking of sensing devices. Relying on the tracking efficiency of thesecontrollers, we design time efficient reference trajectories of motions that correspond tologging tasks. To demonstrate performance, we provide an overview of an extensive testingdone on these machines.

Place, publisher, year, edition, pages
Wiley-Blackwell, 2014
tree harvesting systems; robotic manipulators; excavator; industrialization
National Category
Robotics Control Engineering
urn:nbn:se:umu:diva-86214 (URN)10.1002/rob.21496 (DOI)000333934200001 ()
Available from: 2014-04-04 Created: 2014-02-20 Last updated: 2016-02-15Bibliographically approved
3. Modeling of head orientation for applications in manipulator control
Open this publication in new window or tab >>Modeling of head orientation for applications in manipulator control
(English)Manuscript (preprint) (Other academic)
Abstract [en]

Many heavy equipment manipulators, such as those found on excavators and forestry machines, currently require continuous manual control. While full automation of these systems is complicated due to the unstructured environments in which they are used, semi-automation can be a useful tool for improving both efficiency and working conditions. In the case of forestry machines, we have located specific work tasks where recent advances in time efficient trajectory planning could be used to increase productivity. However, in order to fully take advantage of these methods, a user interface must be developed that will let the operators communicate their intentions to the system in an intuitive and efficient way. We therefore propose a novel interaction method where headtracking is used to estimate the operator’s gaze in order to specify a target point as input to the trajectory planner for the hydraulic manipulator. In this paper, we investigate the feasibility of such a system, through analysis of task-specific requirements. From dedicated user experiments done in a lab we have identified and tested a model from head orientation to gaze direction, which allows us to predict the gaze angle with an average accuracy of close to 4 degrees. In a field test we have verified that the method is transferable to a real-world setting with comparable results.

National Category
Computer Vision and Robotics (Autonomous Systems)
urn:nbn:se:umu:diva-89066 (URN)


Available from: 2014-05-20 Created: 2014-05-20 Last updated: 2014-05-20Bibliographically approved
4. Virtual environment-based teleoperation of forestry machines: designing future interaction methods
Open this publication in new window or tab >>Virtual environment-based teleoperation of forestry machines: designing future interaction methods
2013 (English)In: Journal of Human-Robot Interaction, ISSN 2163-0364, Vol. 2, no 3, 84-110 p.Article in journal (Refereed) Published
Abstract [en]

Virtual environment-assisted teleoperation has great potential as a human-robot interaction paradigm for field robotic systems, in particular when combined with elements of automation. Unstructured outdoor environments present a complex problem with many challenging elements. For the specific application of forestry machines, we investigate which steps are required in order to implement such a system, what potential benefits there are, and how individual components can be adapted to efficiently assist forestry machine operators in their daily work in the near future. An experimental prototype of a teleoperation system with virtual environment-based feedback is constructed using a scenario-based design process. The feasibility of the implementation is partly verified through experimental studies.

Place, publisher, year, edition, pages
Journal of Human-Robot Interaction, 2013
Human-robot Interaction, Teleoperation, Virtual Environments, Field Robotics, System Design
National Category
Computer Vision and Robotics (Autonomous Systems)
urn:nbn:se:umu:diva-83682 (URN)10.5898/JHRI.2.3.Westerberg (DOI)
Available from: 2013-12-03 Created: 2013-12-03 Last updated: 2014-05-20Bibliographically approved

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