| 1. |
- Ortiz Morales, Daniel, 1984-, et al.
(författare)
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Path-constrained motion analysis : an algorithm to understand human performance on hydraulic manipulators
- 2015
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Ingår i: IEEE Transactions on Human-Machine Systems. - 2168-2291. ; 45:2, s. 187-199
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Tidskriftsartikel (refereegranskat)abstract
- 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.
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| 2. |
- La Hera, Pedro
(författare)
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Non-linear dynamics modelling description for simulating the behaviour of forestry cranes
- 2014
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Ingår i: International Journal of Modelling, Identification and Control. - : Inderscience Publishers. - 1746-6172 .- 1746-6180. ; 21, s. 125 - 138
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Tidskriftsartikel (refereegranskat)abstract
- 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 considered as a tentative method for designing modern heavy-duty machine technology. Under this motivation, our aim is to present how modelling 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 modelled by Euler-Lagrange formulations, and the hydraulic system is modelled by principles of fluid dynamics. The calibration algorithms are performed by statistical algorithms based on linear and non-linear least-squares methods. The results of simulation show a significant correspondence between the simulated and observed variables, validating our procedures.
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| 3. |
- Mendoza Trejo, Omar
(författare)
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Robust Concurrent Design of a 2-DOF Collaborative Robot (Cobot)
- 2021
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Ingår i: IEEE/ASME Transactions on Mechatronics. - 1083-4435. ; 26, s. 347-357
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Tidskriftsartikel (refereegranskat)abstract
- Uncertainties play a fundamental role in systems design, since the device behavior may be undesirable in the presence of unknown parameters. For devices interacting with humans, the force exerted by different operators represents a source of uncertainty, which under specific circumstances, could lead to undesired performance. This article proposes a robust concurrent design of a planar 2-DOF cobot modeled as a differential algebraic system and considers the force exerted by the human operator as the output of a PD controller. The robust concurrent design keeps the system performance as less sensitive as possible despite the different operators that interact with the device. Therefore, we establish the robust concurrent design as a multiobjective dynamic optimization problem, intended to minimize both the trajectory tracking error and its sensitivity with respect to uncertain parameters. The source of uncertainty comes from the force applied by the human operator while the independent variables are the inertial and kinematic parameters of the links in the kinematic chain, as well as the cobot controller gains. Experimental results show the effectiveness of the proposed design methodology.
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| 4. |
- Ortiz Morales, Daniel, 1984-, et al.
(författare)
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Generating Periodic Motions for the Butterfly Robot
- 2013
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Ingår i: Intelligent Robots and Systems (IROS), 2013 IEEE/RSJ International Conference on. - : IEEE conference proceedings. - 2153-0858. - 9781467363587 ; , s. 2527-2532
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Konferensbidrag (refereegranskat)abstract
- 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.
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| 5. |
- Ortiz Morales, Daniel, 1984-, et al.
(författare)
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Increasing the level of automation in the forestry logging process with crane trajectory planning and control
- 2014
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Ingår i: Journal of Field Robotics. - : Wiley-Blackwell. - 1556-4959 .- 1556-4967. ; 31:3, s. 343-363
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Tidskriftsartikel (refereegranskat)abstract
- 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.
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| 6. |
- La Hera, Pedro, et al.
(författare)
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Model-Based Development of Control Systems for Forestry Cranes
- 2015
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Ingår i: Journal of Control Science and Engineering. - : Hindawi Limited. - 1687-5249 .- 1687-5257. ; 2015
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Tidskriftsartikel (refereegranskat)abstract
- 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.
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| 7. |
- Piikki, Kristin, et al.
(författare)
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Digital soil mapping for modelling of transport pathways for pesticides to surface water
- 2015
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Rapport (övrigt vetenskapligt/konstnärligt)abstract
- Detailed spatial information of soil texture and SOM content are needed for the modelling of pesticide fate. As part of the SLF project Transport pathways for pesticides to surface water (SLFH1133108) such maps were derived for three depth layers of the soil profile in two sub-catchments with a total area of 450 ha. Data from proximal sensor measurements were combined with national datasets (a digital elevation model and a Quaternary deposit map) and calibrated against soil sample data. Different modelling strategies were tested and the best strategy for each layer was selected for production of the final maps. For topsoil texture, Marsplines modelling with a reduced number of covariables gave the best results (the final models included topographic variables and gamma radiation). In the upper subsoil, the texture was best predicted by an empirical relationship to the topsoil predictions. This is not surprising since the number of calibration samples in the subsoil was very small (n = 18) compared to the number of calibration samples (n = 85). In the deep subsoil, the best strategy was again to use Marsplines modelling with a reduced number of covariables. The SOM content in the topsoil and was mapped by Marsplines modelling using a limited number of predictors and allowing interactions. In the subsoil, however, all soil samples but one had SOM < 3 % and the entire area was classified as as SOM class u. Organic soils according to the SGU QD map (peat areas) were not included in the mapping. Instead they were directly assigned as SOM class t and the texture was not determined.
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| 8. |
- Ren, Keni, 1983-, et al.
(författare)
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Where do we find missing data in a commercial real-time location system? Evidence from 2 dairy farms
- 2021
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Ingår i: JDS Communications. - : American Dairy Science Association. - 2666-9102. ; 2, s. 345-350
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Tidskriftsartikel (refereegranskat)abstract
- Real-time indoor positioning using ultra-wideband devices provides an opportunity for modern dairy farms to monitor the behavior of individual cows; however, missing data from these devices hinders reliable continuous monitoring and analysis of animal movement and social behavior. The objective of this study was to examine the data quality, in terms of missing data, in one commercially available ultra-wideband–based real-time location system for dairy cows. The focus was on detecting major obstacles, or sections, inside open freestall barns that resulted in increased levels of missing data. The study was conducted on 2 dairy farms with an existing commercial real-time location system. Position data were recorded for 6 full days from 69 cows on farm 1 and from 59 cows on farm 2. These data were used in subsequent analyses to determine the locations within the dairy barns where position data were missing for individual cows. The proportions of missing data were found to be evenly distributed within the 2 barns after fitting a linear mixed model with spatial smoothing to logit-transformed proportions (mean = 18% vs. 4% missing data for farm 1 and farm 2, respectively), with the exception of larger proportions of missing data along one of the walls on both farms. On farm 1, the variation between individual tags was large (range: 9–49%) compared with farm 2 (range: 12–38%). This greater individual variation of proportions of missing data indicates a potential problem with the individual tag, such as a battery malfunction or tag placement issue. Further research is needed to guide researchers in identifying problems relating to data capture problems in real-time monitoring systems on dairy farms. This is especially important when undertaking detailed analyses of animal movement and social interactions between animals.
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| 9. |
- Ahlman, Linnéa, 1987, et al.
(författare)
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Stress Detection Using Proximal Sensing of Chlorophyll Fluorescence on the Canopy Level
- 2021
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Ingår i: AgriEngineering. - : MDPI AG. - 2624-7402. ; 3:3, s. 648-668
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Tidskriftsartikel (refereegranskat)abstract
- Chlorophyll fluorescence is interesting for phenotyping applications as it is rich in biological information and can be measured remotely and non-destructively. There are several techniques for measuring and analysing this signal. However, the standard methods use rather extreme conditions, e.g., saturating light and dark adaption, which are difficult to accommodate in the field or in a greenhouse and, hence, limit their use for high-throughput phenotyping. In this article, we use a different approach, extracting plant health information from the dynamics of the chlorophyll fluorescence induced by a weak light excitation and no dark adaption, to classify plants as healthy or unhealthy. To evaluate the method, we scanned over a number of species (lettuce, lemon balm, tomato, basil, and strawberries) exposed to either abiotic stress (drought and salt) or biotic stress factors (root infection using Pythium ultimum and leaf infection using Powdery mildew Podosphaera aphanis ). Our conclusions are that, for abiotic stress, the proposed method was very successful, while, for powdery mildew, a method with spatial resolution would be desirable due to the nature of the infection, i.e., point-wise spread. Pythium infection on the roots is not visually detectable in the same way as powdery mildew; however, it affects the whole plant, making the method an interesting option for Pythium detection. However, further research is necessary to determine the limit of infection needed to detect the stress with the proposed method.
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| 10. |
- Ringdahl, Ola, 1971-, et al.
(författare)
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Estimating wheel slip for a forest machine using RTK-DGPS
- 2012
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Ingår i: Journal of terramechanics. - : Elsevier BV. - 0022-4898 .- 1879-1204. ; 49:5, s. 271-279
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Tidskriftsartikel (refereegranskat)abstract
- Wheel slip may increase the risk for wheel rutting and tear up ground vegetation and superficial roots and thereby decreasing the bearing capacity of the ground, but also reducing the growth of nearby standing forest trees. With increased slip, more energy is consumed for making wheel ruts in the ground, with increased fuel consumption as a result. This paper proposes a novel method for measuring slip in an uneven forest terrain with an 8WD forestry machine. This is done by comparing the wheel velocity reported by the machine and velocity measured with an accurate DGPS system. Field tests with a forestry machine showed that slip could be calculated accurately with the suggested method. The tests showed that there was almost no slip on asphalt or gravel surfaces. In a forest environment, 10–15% slip was common. A future extension of the method enabling estimation of the slip of each wheel pair in the bogies is also suggested.
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