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La Hera, Pedro M
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Publications (10 of 33) Show all publications
Lindroos, O., Ringdahl, O., Pedro, L. H., Hohnloser, P. & Hellström, T. (2015). Estimating the position of the harvester head: a key step towards the precision forestry of the future?. Croatian Journal of Forest Engineering, 36(2), 147-164
Open this publication in new window or tab >>Estimating the position of the harvester head: a key step towards the precision forestry of the future?
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2015 (English)In: Croatian Journal of Forest Engineering, ISSN 1845-5719, E-ISSN 1848-9672, Vol. 36, no 2, p. 147-164Article in journal (Refereed) Published
Abstract [en]

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.

Place, publisher, year, edition, pages
Zagreb, Croatia: Croatian Journal of Forest Engineering, 2015
Keywords
boom tip control, automation, ALS, sensors, harvester data
National Category
Forest Science Robotics Computer Vision and Robotics (Autonomous Systems)
Research subject
computer and systems sciences
Identifiers
urn:nbn:se:umu:diva-109881 (URN)000363907900001 ()
Available from: 2015-10-08 Created: 2015-10-08 Last updated: 2018-06-07Bibliographically approved
La Hera, P. & Morales, D. O. (2015). Model-Based Development of Control Systems for Forestry Cranes. Journal of Control Science and Engineering, 2015, Article ID 256951.
Open this publication in new window or tab >>Model-Based Development of Control Systems for Forestry Cranes
2015 (English)In: Journal of Control Science and Engineering, ISSN 1687-5249, E-ISSN 1687-5257, Vol. 2015, article id 256951Article in journal (Refereed) Published
Abstract [en]

Model-based methods are used in industry for prototyping concepts based on mathematical models. With our forest industry partners, we have established a model-based workflow for rapid development of motion control systems for forestry cranes. Applying this working method, we can verify control algorithms, both theoretically and practically. This paper is an example of this workflow and presents four topics related to the application of nonlinear control theory. The first topic presents the system of differential equations describing the motion dynamics. The second topic presents nonlinear control laws formulated according to sliding mode control theory. The third topic presents a procedure for model calibration and control tuning that are a prerequisite to realize experimental tests. The fourth topic presents the results of tests performed on an experimental crane specifically equipped for these tasks. Results of these studies show the advantages and disadvantages of these control algorithms, and they highlight their performance in terms of robustness and smoothness.

National Category
Robotics Control Engineering
Identifiers
urn:nbn:se:umu:diva-112787 (URN)10.1155/2015/256951 (DOI)000361955200001 ()
Available from: 2015-12-14 Created: 2015-12-14 Last updated: 2018-06-07Bibliographically approved
Ortiz Morales, D., La Hera, P., Westerberg, S., Freidovich, L. & Shiriaev, A. (2015). Path-constrained motion analysis: an algorithm to understand human performance on hydraulic manipulators. IEEE Transactions on Human-Machine Systems, 45(2), 187-199
Open this publication in new window or tab >>Path-constrained motion analysis: an algorithm to understand human performance on hydraulic manipulators
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2015 (English)In: IEEE Transactions on Human-Machine Systems, ISSN 2168-2291, Vol. 45, no 2, p. 187-199Article in journal (Refereed) Published
Abstract [en]

We propose a novel method to analyze how human operators use hydraulic manipulators of heavy-duty equipment. The approach is novel in the sense that it applies knowledge of motion planning and optimization techniques used in robotics. As an example, we consider the case of operating a forestry crane. To that end, we use motion data that has been recorded during standard operation with the help of sensors and a data acquisition unit. The data backs up the notion that operators work by performing repeatable patterns observed in the trajectories of the manipulator's joints. We show how this nominal behavior is computed, and consequently this allow us to present the following: 1) an analytical procedure to analyze motions, 2) how to represent the "performance" of the operator in a 2D plot, 3) an example of how to use this information to suggest customized control settings, and 4) some complementary ideas needed for improving efficiency through automation.

Keywords
forestry, human performance analysis, hydraulic manipulators, manual control
National Category
Robotics Control Engineering
Identifiers
urn:nbn:se:umu:diva-87595 (URN)10.1109/THMS.2014.2366873 (DOI)000351468500004 ()
Available from: 2014-04-04 Created: 2014-04-04 Last updated: 2018-06-08Bibliographically approved
Khan, M. S., ur Réhman, S., La Hera, P., Liu, F. & Li, H. (2014). A pilot user's prospective in mobile robotic telepresence system. In: 2014 Asia-Pacific Signal and Information Processing Association Annual Summit and Conference (APSIPA 2014): . Paper presented at Annual Summit and Conference of Asia-Pacific-Signal-and-Information-Processing-Association (APSIPA), DEC 09-12, 2014, Angkor, CAMBODIA. IEEE
Open this publication in new window or tab >>A pilot user's prospective in mobile robotic telepresence system
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2014 (English)In: 2014 Asia-Pacific Signal and Information Processing Association Annual Summit and Conference (APSIPA 2014), IEEE, 2014Conference paper, Published paper (Refereed)
Abstract [en]

In this work we present an interactive video conferencing system specifically designed for enhancing the experience of video teleconferencing for a pilot user. We have used an Embodied Telepresence System (ETS) which was previously designed to enhance the experience of video teleconferencing for the collaborators. In this work we have deployed an ETS in a novel scenario to improve the experience of pilot user during distance communication. The ETS is used to adjust the view of the pilot user at the distance location (e.g. distance located conference/meeting). The velocity profile control for the ETS is developed which is implicitly controlled by the head of the pilot user. The experiment was conducted to test whether the view adjustment capability of an ETS increases the collaboration experience of video conferencing for the pilot user or not. The user study was conducted in which participants (pilot users) performed interaction using ETS and with traditional computer based video conferencing tool. Overall, the user study suggests the effectiveness of our approach and hence results in enhancing the experience of video conferencing for the pilot user.

Place, publisher, year, edition, pages
IEEE, 2014
Keywords
Teleconferencing, Collaboration, Computers, Estimation, Noise, Computer science, Human factors
National Category
Robotics Interaction Technologies Computer Vision and Robotics (Autonomous Systems)
Identifiers
urn:nbn:se:umu:diva-108559 (URN)10.1109/APSIPA.2014.7041635 (DOI)000392861900123 ()978-6-1636-1823-8 (ISBN)
Conference
Annual Summit and Conference of Asia-Pacific-Signal-and-Information-Processing-Association (APSIPA), DEC 09-12, 2014, Angkor, CAMBODIA
Available from: 2015-09-14 Created: 2015-09-14 Last updated: 2018-06-07Bibliographically approved
Ortiz Morales, D., Westerberg, S., La Hera, P., Mettin, U., Freidovich, L. & Shiriaev, A. (2014). Increasing the level of automation in the forestry logging process with crane trajectory planning and control. Journal of Field Robotics, 31(3), 343-363
Open this publication in new window or tab >>Increasing the level of automation in the forestry logging process with crane trajectory planning and control
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2014 (English)In: Journal of Field Robotics, ISSN 1556-4959, E-ISSN 1556-4967, Vol. 31, no 3, p. 343-363Article 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
Keywords
tree harvesting systems; robotic manipulators; excavator; industrialization
National Category
Robotics Control Engineering
Identifiers
urn:nbn:se:umu:diva-86214 (URN)10.1002/rob.21496 (DOI)000333934200001 ()
Available from: 2014-04-04 Created: 2014-02-20 Last updated: 2018-06-08Bibliographically approved
La Hera, P. & Ortiz Morales, D. (2014). Non-linear dynamics modelling description for simulating the behavior of forestry cranes. International journal of Modeling, identification and control, 21(2), 125-138
Open this publication in new window or tab >>Non-linear dynamics modelling description for simulating the behavior of forestry cranes
2014 (English)In: International journal of Modeling, identification and control, ISSN 1746-6172, E-ISSN 1746-6180, Vol. 21, no 2, p. 125-138Article in journal (Refereed) Published
Abstract [en]

Model-based design is a standard framework widely adopted in modern industry. It is used for designing multi-domain engineering solutions based on computer-aided simulation technology. Currently, this approach is also being viewed as a tentative method for designing modern heavy-duty machine technology. Under this motivation, our aim is to present how modeling techniques can be used for simulating dynamics of forestry machines. To this end, we consider a forestry crane, and propose mathematical models and calibration techniques, such that model-based methods can subsequently be applied. The complexity of the machine is represented by first principle laws, in which the mechanical system is modeled by Euler-Lagrange formulations, and the hydraulic system is modeled by principles of fluid dynamics. The calibration algorithms are performed by statistical algorithms based on linear and nonlinear least-squares methods. The results of simulation show a significant correspondence between the simulated and observed variables, validating our procedures.

Place, publisher, year, edition, pages
Inderscience Enterprises Ltd, 2014
Keywords
forestry machines, forestry cranes, hydraulic manipulators, dynamic modelling, model calibration, identification, simulation, real–time implementation, nonlinear dynamics, heavy–duty machinery, mathematical modelling, Euler–Lagrange formulations, fluid dynamics
National Category
Control Engineering Robotics
Identifiers
urn:nbn:se:umu:diva-87577 (URN)10.1504/IJMIC.2014.060006 (DOI)
Available from: 2014-04-04 Created: 2014-04-04 Last updated: 2018-06-08Bibliographically approved
Ortiz Morales, D., La Hera, P. & Ur Rehman, S. (2013). Generating Periodic Motions for the Butterfly Robot. In: Amato, N. (Ed.), Intelligent Robots and Systems (IROS), 2013 IEEE/RSJ International Conference on: . Paper presented at IEEE/RSJ International Conference on Intelligent Robots and Systems (IROS) Location: Tokyo, Japan Date: Nov 3-8, 2013 (pp. 2527-2532). IEEE conference proceedings
Open this publication in new window or tab >>Generating Periodic Motions for the Butterfly Robot
2013 (English)In: Intelligent Robots and Systems (IROS), 2013 IEEE/RSJ International Conference on / [ed] Amato, N., IEEE conference proceedings, 2013, p. 2527-2532Conference paper, Published paper (Refereed)
Abstract [en]

We analyze the problem of dynamic non-prehensile manipulation by considering the example of thebutterfly robot. Our main objective is to study the problem of stabilizing periodic motions, which resemble some form of juggling acrobatics. To this end, we approach the problem by considering theframework of virtual holonomic constraints. Under this basis, we provide an analytical and systematic solution to the problems of trajectory planning and design of feedback controllers to guarantee orbital exponential stability. Results are presented in the form of simulation tests.

Place, publisher, year, edition, pages
IEEE conference proceedings, 2013
Series
IEEE International Conference on Intelligent Robots and Systems, ISSN 2153-0858
Keywords
Underactuated mechanical systems, limit cycles, virtual holonomic constraints, transverse linearization
National Category
Robotics
Identifiers
urn:nbn:se:umu:diva-86210 (URN)10.1109/IROS.2013.6696712 (DOI)000331367402100 ()978-1-4673-6358-7 (ISBN)
Conference
IEEE/RSJ International Conference on Intelligent Robots and Systems (IROS) Location: Tokyo, Japan Date: Nov 3-8, 2013
Available from: 2014-02-20 Created: 2014-02-20 Last updated: 2018-06-08Bibliographically approved
La Hera, P., Shiriaev, A. S., Freidovich, L. B., Mettin, U. & Gusev, S. V. (2013). Stable walking gaits for a three-link planar biped robot with one actuator. IEEE Transactions on robotics, 29(3), 589-601
Open this publication in new window or tab >>Stable walking gaits for a three-link planar biped robot with one actuator
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2013 (English)In: IEEE Transactions on robotics, ISSN 1552-3098, E-ISSN 1941-0468, IEEE transactions on robotics, Vol. 29, no 3, p. 589-601Article in journal (Refereed) Published
Abstract [en]

We consider a benchmark example of a three-link planar biped walker with torso, which is actuated in between the legs. The torso is thought to be kept upright by two identical torsional springs. The mathematical model reflects a three-degree-of-freedom mechanical system with impulse effects, which describe the impacts of the swing leg with the ground, and the aim is to induce stable limit-cycle walking on level ground. The main contribution is a novel systematic trajectory planning procedure for solving the problem of gait synthesis. The key idea is to find a system of ordinary differential equations for the functions describing a synchronization pattern for the time evolution of the generalized coordinates along a periodic motion. These functions, which are known as virtual holonomic constraints, are also used to compute an impulsive linear system that approximates the time evolution of the subset of coordinates that are transverse to the orbit of the continuous part of the periodic solution. This auxiliary system, which is known as transverse linearization, is used to design a nonlinear exponentially orbitally stabilizing feedback controller. The performance of the closed-loop system and its robustness with respect to various perturbations and uncertainties are illustrated via numerical simulations.

Keywords
Biped robots, holonomic servoconstraints, limit-cycle walking, orbital stabilization, trajectory planning with dynamic constraints, transverse linearization, underactuated mechanical systems, virtual holonomic constraints
National Category
Robotics Veterinary Science
Identifiers
urn:nbn:se:umu:diva-39717 (URN)10.1109/TRO.2013.2239551 (DOI)000320137200001 ()
Funder
Swedish Research Council, 2008-4369
Note

Funding Agency, Grant Number:

Russian Federal Agency for Science and Innovation, 02.740.11.505

Russian Federal Target Program "Research & Development in Priority Areas", 11.519.11.4007

Norwegian Research Council under KMB grant Next Generation Robotics for Norwegian Industry

Norwegian Research Council under FRIPRO Grant, 214525/F20

Russian Foundation for Basic Research, 12-01-00808

Available from: 2011-02-04 Created: 2011-02-04 Last updated: 2018-06-08Bibliographically approved
Ortiz Morales, D. & La Hera, P. X. (2012). Design of energy efficient walking gaits for a three-link planar biped walker with two unactuated degrees of freedom. In: Robotics and Automation (ICRA), 2012 IEEE International Conference on: . Paper presented at 2012 IEEE International Conference on Robotics and Automation (ICRA), Location: St Paul, MN, Date: May 14-18, 2012 (pp. 148-153). New York: IEEE Computer Society
Open this publication in new window or tab >>Design of energy efficient walking gaits for a three-link planar biped walker with two unactuated degrees of freedom
2012 (English)In: Robotics and Automation (ICRA), 2012 IEEE International Conference on, New York: IEEE Computer Society, 2012, p. 148-153Conference paper, Published paper (Other academic)
Abstract [en]

We consider the example of a three-link planar biped walker with two passive links. The main objective is to design symmetric periodic gaits in flat ground, that can be exponentially stabilized by feedback control. To this end, we apply recent advances in nonlinear control, to propose a systematic procedure to the problems of gait synthesis and control design. The core of the method lays on a nontrivial coordinate transformation, in order to approach the problem in a state-dependent form. For gait synthesis, such procedure allows a reduction of the search space, with the feasibility of considering energetic performance for optimization. For control design, this allows to apply concepts of transverse linearization, to design a nonlinear feedback control law, which performance is studied by numerical simulations.

Place, publisher, year, edition, pages
New York: IEEE Computer Society, 2012
Series
IEEE International Conference on Robotics and Automation, ISSN 2152-4092
Keywords
Walking robots, underactuated mechanical systems, limit cycles, virtual holonomic constraints, transverse linearization
National Category
Computer Sciences Robotics
Identifiers
urn:nbn:se:umu:diva-61582 (URN)10.1109/ICRA.2012.6224874 (DOI)000309406700023 ()978-1-4673-1405-3 (ISBN)
Conference
2012 IEEE International Conference on Robotics and Automation (ICRA), Location: St Paul, MN, Date: May 14-18, 2012
Available from: 2012-11-27 Created: 2012-11-20 Last updated: 2018-06-08Bibliographically approved
Ortíz Morales, D. & La Hera, P. X. (2012). Design of stable walking gaits for biped robots with several underactuated degrees of freedom. In: Dynamic Walking Conference 2012, Pensacola, Florida, U.S.A.: . Paper presented at Dynamic Walking Conference 2012, Pensacola, Florida, U.S.A. 21 - 25 May 2012.
Open this publication in new window or tab >>Design of stable walking gaits for biped robots with several underactuated degrees of freedom
2012 (English)In: Dynamic Walking Conference 2012, Pensacola, Florida, U.S.A., 2012Conference paper, Poster (with or without abstract) (Refereed)
Abstract [en]

Dynamic walking gaits are theoretically reflected by theperiodic solutions exhibited by nonlinear impulsive dynamicalsystems [1]. In practice, such solutions, knownas limit cycles, can exist either as a natural responseof the system, e.g. passive walkers, or by the use offeedback control. Analytically, finding these solutionsis certainly challenging, and the complexity of the problemincreases considerably if a mixture in between passiveand actuated joints are considered, i.e. underactuatedrobots.

National Category
Robotics
Identifiers
urn:nbn:se:umu:diva-61880 (URN)
Conference
Dynamic Walking Conference 2012, Pensacola, Florida, U.S.A. 21 - 25 May 2012
Available from: 2012-11-29 Created: 2012-11-28 Last updated: 2018-06-08Bibliographically approved
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