| 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. |
- 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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| 8. |
- 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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| 9. |
- Elmgren Frykberg, Gunilla, 1957-, et al.
(författare)
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Impact of stroke on anterior-posterior force generation prior to seat-off during sit-to-walk
- 2012
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Ingår i: Gait & Posture. - : Elsevier BV. - 0966-6362 .- 1879-2219. ; 35:1, s. 56-60
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Tidskriftsartikel (refereegranskat)abstract
- Force generation during sit-to-walk (STW) post-stroke is a poorly studied area, although STW is a common daily transfer giving rise to a risk of falling in persons with disability. The purpose of this study was to describe and compare strategies for anterior-posterior (AP) force generation prior to seat-off during the STW transfer in both subjects with stroke and in matched controls. During STW at self-selected speed, AP force data were collected by 4 force plates, beneath the buttocks and feet from eight subjects with stroke '(>6 months after onset) and 8 matched controls. Subjects with post-stroke hemiparesis and matched controls generated a similar magnitude of total AP force impulses (F-1.71 = 0.67; p = 0.42) beneath buttocks and feet prior to seat-off during STW. However, there were significant group differences in AP force impulse generation beneath the stance buttock (i.e. the non-paretic buttock in the stroke group), with longer duration (F-1.71 = 8.78; p <0.005), larger net AP impulse (F-1.71 = 6.76; p < 0.05) and larger braking impulse (F-1.71 = 7.24; p <0.05) in the stroke group. The total braking impulse beneath buttocks and feet was about 4.5 times larger in the stroke group than in the control group (F-1.71 = 8.84; p < 0.005). An intra-and inter-limb dys-coordination with substantial use of braking impulses was demonstrated in the stroke group. This motor strategy differed markedly from the smooth force interaction in the control group. These results might be important in the development of treatment models related to locomotion post-stroke.
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| 10. |
- Gebresenbet, Girma
(författare)
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Modeling of Unmanned Aerial Vehicles for Smart Agriculture Systems Using Hybrid Fuzzy PID Controllers
- 2024
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Ingår i: Applied Sciences. - 2076-3417. ; 14
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Tidskriftsartikel (refereegranskat)abstract
- Unmanned aerial vehicles have a wide range of uses in the military field, non-combat situations, and civil works. Due to their ease of operation, unmanned aerial vehicles (UAVs) are highly sought after by farmers and are considered the best agricultural technologies, since different types of controller algorithms are being integrated into drone systems, making drones the most affordable option for smart agriculture sectors. PID controllers are among the controllers frequently incorporated into drone systems. Although PID controllers are frequently used in drones, they have some limitations, such as sensitivity to noise and measurement errors, which can lead to instability or oscillations in the system. On the other hand, PID controllers provide improved accuracy in drone system responses. When using PID controllers to achieve the best performance in a drone system, it is better to share the advantages of PID controllers with other intelligence controllers. One promising option is the fuzzy PID controller. The aim of this study was to control quadcopter states (rolling, altitude, and airspeed) by leveraging quadcopter technology and adding hybrid fuzzy PID controls into the system. The quadcopter system and its controllers were mathematically modeled using the Simulink/MATLAB platform, and the system was controlled by fuzzy PID controllers. For validation purposes, the fuzzy PID controller was compared with a classically tuned PID controller. For roll, height, and airspeed, the fuzzy PID controller provided an improvement of 41.5%, 11%, and 44%, respectively, over the classically tuned PID controller. Therefore, the fuzzy PID controller best suits the needs of farmers and is compatible with smart agriculture systems.
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