| 1. |
- Andersson, Jan-Erik, et al.
(författare)
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Robot control for wood carving operations
- 2001
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Ingår i: Mechatronics (Oxford). - 0957-4158 .- 1873-4006. ; 11:4, s. 475-490
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Tidskriftsartikel (refereegranskat)abstract
- The aim of this paper is to implement sensor control in wood carving operations. The introduction of wood carving is a step towards the development of a new manufacturing method for the wood manufacturing industry, where wood carving would facilitate increased freedom of the design choice. A control method that improves robot control and supports simpler programming, based on using an industrial robot equipped with a wrist mounted force/torque-sensor. is proposed for the wood carving process. This paper describes the structure and control algorithm of the system and how different machining parameters affect the cutting forces. The evaluation of the system showed that it is possible to control the cutting depth at speeds up to 7.5 mms by adjusting the rake angle of the tool to obtain a nominal force.
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| 2. |
- Danielsson, Fredrik, 1972-, et al.
(författare)
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Validation, off-line programming and optimisation of industrial control logic
- 2003
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Ingår i: Mechatronics (Oxford). - 0957-4158 .- 1873-4006. ; 13:6, s. 571-585
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Tidskriftsartikel (refereegranskat)abstract
- This article proposes a classification of different methods for validation, off-line programming and optimisation of control logic. The classification is an overview of different methods available and includes advantages and disadvantages for each method. The method overview points out a superior method, control system emulation, which is the most cost-effective and flexible method. The control system emulation method is also general and may be applied to validate and optimise control logic in various applications. Further, the method is compared with several other methods for validation of industrial control systems. However the method requires a standardised system architecture. This article proposes such architecture for the control system emulation method. Here, a control system emulator has also been implemented with the specific system architecture described in this article. An application case is also provided to demonstrate an approach to the integration of a control system emulator into a virtual manufacturing system.
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| 3. |
- Hyyppä, Kalevi
(författare)
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Design considerations in a laser navigation system for mobile robots
- 1994
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Ingår i: Mechatronics (Oxford). - : Elsevier BV. - 0957-4158 .- 1873-4006. ; 4:2, s. 199-206
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Tidskriftsartikel (refereegranskat)abstract
- A navigation system for mobile robots is discussed. The system utilizes a laser anglemeter which measures heading angles to beacons made of retroreflective tape. It is shown that the motion restrictions of a typical mobile robot can be utilized to simplify the angle measurement task considerably. Beam properties of typical HeNe-lasers and collimated GaAs-laser diodes are discussed. The collimated GaAs-laser is shown to be superior for the anglemeter. A design rule is given for the anglemeter receiver optics. Noise sources in the anglemeter receiver are discussed. Reference is made to a new low-noise photodiode-amplifier circuit which has the photodiode in the feedback path.
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| 4. |
- Moore, Philip, et al.
(författare)
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Intelligent semi-autonomous vehicles in materials handling
- 1999
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Ingår i: Mechatronics (Oxford). - : Elsevier. - 0957-4158 .- 1873-4006. ; 9:7, s. 881-892
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Tidskriftsartikel (refereegranskat)abstract
- An increase in functionality of semi-autonomous vehicles (SAV) through the implementation of intelligent distributed control and smart sensing techniques is presented. In combination with a modular design approach, this facilitates system modification and improvement, combined with faster customisation of the platform. A distributed and reactive behavioural control architecture is used to realise local autonomous navigation capabilities; improved operator interaction; self protection and safer operation. A virtual engineering environment based on a computer-aided-graphics platform is used (1) for modelling the vehicle and the environment in which it can operate; (2) developing pre-emptive learning and training of responses/behaviours, and (3) for evaluation of vehicle functionality as part of an integrated materials handling system.
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| 5. |
- Moore, P. R., et al.
(författare)
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Virtual engineering : an integrated approach to agile manufacturing machinery design and control
- 2003
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Ingår i: Mechatronics (Oxford). - : BioMed Central Ltd.. - 0957-4158 .- 1873-4006. ; 13:10, s. 1105-1121
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Tidskriftsartikel (refereegranskat)abstract
- A virtual manufacturing approach for designing, programming, testing, verifying and deploying control systems for agile modular manufacturing machinery are proposed in this paper. It introduces the concepts, operations, mechanisms and implementation techniques for integrating simulation environments and distributed control system environments so that the control logic programs that have been programmed and verified in the virtual environment can be seamlessly transferred to the distributed control system environment for controlling the real devices. The approach looks to exploit simulation in a much wider range of applications with great advantages in the design and development of manufacturing machine systems. In particular, it facilitates the verification of the runtime support applications using the simulation model before they are applied to the real system. Mechanisms that allow runtime data to be collected during operation of the real machinery to calibrate the simulation models are also proposed. The system implemented delivers a powerful set of software tools for realising agile modular manufacturing systems.
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| 6. |
- Uusijärvi, Rickard, et al.
(författare)
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Introducing distributed control in mobile machines based on hydraulic actuators
- 1994
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Ingår i: Mechatronics (Oxford). - : Elsevier. - 0957-4158 .- 1873-4006. ; 4:2, s. 51-72
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Tidskriftsartikel (refereegranskat)abstract
- The design of mobile machines demanding outspread hydraulic systems involves at least two major trade-offs, regarding the distribution and configuration of hydraulic components and the degree of distributed computer control within the machines. As a case study the “NODDATOR” project is described, in which a distributed control approach utilizing the Controller Area Network was applied to control a hydraulic application, a drill arm - boom - on a tunnelling machine. Practical experience in the project and advantages of the technique compared with the technique used today - a more or less strict implementation of a central control system - are pointed out. Further, the benefits which can be obtained by fully exploiting the possibilities of hydraulic distribution and distributed computer control, i.e. reduced cabling and cost, increased functionality and modularity are discussed. Among the new problems that arise, the multidisciplinarity of the technique and reliability issues are the most difficult ones. Reliability is a very relevant area for mechatronics where more research is needed as computer control systems increasingly replace mechanical solutions. The conclusion of the article is clear: Machines based on distributed technology are clearly the winners compared to current machines.
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| 7. |
- Ahmad, Aftab, et al.
(författare)
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A model-based and simulation-driven methodology for design of haptic devices
- 2014
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Ingår i: Mechatronics (Oxford). - : Elsevier BV. - 0957-4158 .- 1873-4006. ; 24:7, s. 805-818
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Tidskriftsartikel (refereegranskat)abstract
- High precision and reliable haptic devices are highly complex products. The complexity that has to be carefully treated in the design process is largely due to the multi-criteria and conflicting character of the functional and performance requirements. These requirements include high stiffness, large work-space, high manipulability, small inertia, low friction, high transparency, as well as cost constraints. The requirements are a basis for creating and assessing design concepts. Concept evaluation relies to a large extent on a systematic usage of kinematic, dynamic, stiffness, friction, and control models. The design process can benefit from a model-based and simulation-driven approach, where one starts from an abstract top-level model that is extended via stepwise refinements and design space exploration into a detailed and integrated systems model that can be physically realized. Such an approach is presented, put in context of the V-model, and evaluated through a test case where a haptic device, based on a Stewart platform, is designed and realized. It can be concluded, based on simulation and experimental results that the performance of this deterministically optimized haptic device satisfies the stated user requirements. Experiences from this case indicate that the methodology is capable of supporting effective and efficient development of high performing haptic devices. However, more test cases are needed to further validate the presented methodology.
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| 8. |
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| 9. |
- Carvalho Bittencourt, André, 1984-, et al.
(författare)
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A data-driven approach to diagnostics of repetitive processes in the distribution domain : Applications to gearbox diagnosticsin industrial robots and rotating machines
- 2014
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Ingår i: Mechatronics (Oxford). - : Elsevier. - 0957-4158 .- 1873-4006. ; 24:8, s. 1032-1041
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Tidskriftsartikel (refereegranskat)abstract
- This paper presents a data-driven approach to diagnostics of systems that operate in a repetitive manner. Considering that data batches collected from a repetitive operation will be similar unless in the presence of an abnormality, a condition change is inferred by comparing the monitored data against an available nominal batch. The method proposed considers the comparison of data in the distribution domain, which reveals information of the data amplitude. This is achieved with the use of kernel density estimates and the Kullback–Leibler distance. To decrease sensitivity to disturbances while increasing sensitivity to faults, the use of a weighting vector is suggested which is chosen based on a labeled dataset. The framework is simple to implement and can be used without process interruption, in a batch manner. The approach is demonstrated with successful experimental and simulation applications to wear diagnostics in an industrial robot gearbox and for diagnostics of gear faults in a rotating machine.
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| 10. |
- Chellapurath, Mrudul, et al.
(författare)
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USLIP dynamics emerges in underwater legged robot with foot kinematics of punting crabs
- 2024
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Ingår i: Mechatronics (Oxford). - : Elsevier BV. - 0957-4158 .- 1873-4006. ; 99
-
Tidskriftsartikel (refereegranskat)abstract
- This article investigates bioinspired solutions for achieving stable dynamic gaits in legged robots through leg coordination and foot trajectories. In this study, we recorded the kinematics of underwater running of the crab, Pachygrapsus marmoratus, and implemented the parameterized foot trajectories and inter-leg coordination on an underwater legged robot, SILVER 2.0. The robot's design parameters like legs’ stiffness, leg length, and body mass are based on the Underwater Spring Loaded Inverted Pendulum (USLIP), a model that describes underwater running in animals. With this implementation, we observed the spontaneous emergence of USLIP dynamics in 20% of the strides in the robot. This approach allowed SILVER 2.0 to leverage the advantages of stable dynamic gaits while optimizing the foot trajectory and inter-leg coordination, resulting in improved locomotion performances. The robot achieved a forward velocity of 0.16 m/s, twice the value obtained in previous gaits. Our study presents a promising approach for improving the locomotion performance of legged robots, enabling their effective use in various field applications, and further confirms a broad embedding of controllers generating template dynamics.
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| 11. |
- Chhabra, Robin, et al.
(författare)
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A holistic concurrent design approach to robotics using hardware-in-the-loop simulation
- 2013
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Ingår i: Mechatronics (Oxford). - : Elsevier BV. - 0957-4158 .- 1873-4006. ; 23:3, s. 335-345
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Tidskriftsartikel (refereegranskat)abstract
- This paper discusses a practical approach to the concurrent design of robot manipulators, which is based on an alternative design methodology, namely Holistic Concurrent Design (HCD), as well as the utilization of a modular hardware-in-the-loop simulation. Holistic concurrent design is a systematic design methodology for mechatronic systems that formalizes subjective notions of design, resulting in the simplification of the multi-objective constrained optimization process. Its premise is to enhance the communication between designers with various backgrounds and customers, and to consider numerous design variables with different natures concurrently. The methodology redefines the ultimate goal of design based on the qualitative notion of satisfaction, and formalizes the effect of designer's subjective attitude in the process. The hardware-in-the-loop platform involves physical joint modules and the control unit of a manipulator in addition to the software simulation to reduce modeling complexities and to take into account physical phenomena that are hard to be captured mathematically. This platform is implemented in the HCD design architecture to reliably evaluate the design attributes and performance supercriterion during the design process. The resulting architecture is applied to redesigning kinematic, dynamic and control parameters of an industrial manipulator. Copyright © 2013 Published by Elsevier Ltd. All rights reserved.
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| 12. |
- Chhabra, Robin, et al.
(författare)
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Holistic system modeling in mechatronics
- 2011
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Ingår i: Mechatronics (Oxford). - : Elsevier BV. - 0957-4158 .- 1873-4006. ; 21:1, s. 166-175
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Tidskriftsartikel (refereegranskat)abstract
- This paper outlines an alternative modeling scheme for mechatronic systems, as a basis for their concurrent design. The approach divides a mechatronic system into three generic subsystems, namely generalized executive, sensory and control, and links them together utilizing a combination of bond graphs and block diagrams. It considers the underlying principles of a multidisciplinary system, and studies the flow of energy and information throughout its different constituents. The first and second laws of thermodynamics are reformulated for mechatronic systems, and as a result three holistic design criteria, namely energy, entropy and agility, are defined. These criteria are formulated using the bond graph representation of a mechatronic system. As a case study, the three criteria are employed separately for concurrent design of a five degree-of-freedom industrial robot manipulator. © 2010 Elsevier Ltd. All rights reserved.
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| 13. |
- Edin Grimheden, Martin
(författare)
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Can agile methods enhance mechatronics design education?
- 2013
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Ingår i: Mechatronics (Oxford). - : Elsevier BV. - 0957-4158 .- 1873-4006. ; 23:8, s. 967-973
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Tidskriftsartikel (refereegranskat)abstract
- This paper presents a study of the integration of agile methods into mechatronics design education, as performed at KTH Royal Institute of Technology. The chosen method, Scrum, and the context of the studied capstone course are presented. With the integration of Scrum into the capstone projects, an educational favorable alternative is identified, to previously used design methodologies such as more traditional stage-gate methods as the Waterfall or method or the V-model. This is due to the emphasis on early prototyping, quick feedback and incremental development. It still might not be the favorable method for use in large scale industrial development projects where formal procedures might still be preferred, but the pedagogical advantages in mechatronics education are valuable. Incremental development and rapid prototyping for example gives many opportunities for students to reflect and improve. The Scrum focus on self-organizing teams also provides a platform to practice project organization, by empowering students to take responsibility for the product development process. Among the results of this study, it is shown that it is possible and favorable to integrate Scrum in a mechatronics capstone course and that this can enhance student preparation for a future career as mechatronics designers or product developers. It is also shown that this prepares the students with a larger flexibility to handle the increased complexity in mechatronics product development and thereby enabling the project teams to deliver results faster, more reliable and with higher quality.
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| 14. |
- Edrén, Johannes, et al.
(författare)
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Energy efficient cornering using over-actuation
- 2019
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Ingår i: Mechatronics (Oxford). - : Elsevier Ltd. - 0957-4158 .- 1873-4006. ; 59, s. 69-81
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Tidskriftsartikel (refereegranskat)abstract
- This work deals with utilisation of active steering and propulsion on individual wheels in order to improve a vehicle's energy efficiency during a double lane change manoeuvre at moderate speeds. Through numerical optimisation, solutions have been found for how wheel steering angles and propulsion torques should be used in order to minimise the energy consumed by the vehicle travelling through the manoeuvre. The results show that, for the studied vehicle, the energy consumption due to cornering resistance can be reduced by approximately 10% compared to a standard vehicle configuration. Based on the optimisation study, simplified algorithms to control wheel steering angles and propulsion torques that results in more energy efficient cornering are proposed. These algorithms are evaluated in a simulation study that includes a path tracking driver model. Based on a combined rear axle steering and torque vectoring control an improvement of 6–8% of the energy consumption due to cornering was found. The results indicate that in order to improve energy efficiency for a vehicle driving in a non-safety-critical cornering situation the force distribution should be shifted towards the front wheels.
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| 15. |
- Gratal, Xavi, et al.
(författare)
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Visual servoing on unknown objects
- 2012
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Ingår i: Mechatronics (Oxford). - : Elsevier BV. - 0957-4158 .- 1873-4006. ; 22:4, s. 423-435
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Tidskriftsartikel (refereegranskat)abstract
- We study visual servoing in a framework of detection and grasping of unknown objects. Classically, visual servoing has been used for applications where the object to be servoed on is known to the robot prior to the task execution. In addition, most of the methods concentrate on aligning the robot hand with the object without grasping it. In our work, visual servoing techniques are used as building blocks in a system capable of detecting and grasping unknown objects in natural scenes. We show how different visual servoing techniques facilitate a complete grasping cycle.
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| 16. |
- Grimheden, Martin, et al.
(författare)
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Mechatronics : the Evolution of an Academic Discipline in Engineering Education
- 2005
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Ingår i: Mechatronics (Oxford). - : Elsevier BV. - 0957-4158 .- 1873-4006. ; 15:2, s. 179-192
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Tidskriftsartikel (refereegranskat)abstract
- In a didactic approach to mechatronics, the academic subject can be defined according to four dimensions: identity, legitimacy, selection and communication. A result of defining the legitimacy of mechatronics as functional is that the ultimate identity can be viewed as thematic. Following this, a model is proposed to describe the evolution of mechatronics, from a disciplinary identity towards a thematic. The move from a disciplinary identity to a thematic is divided into six stages, each represented by a characteristic view and academic practice of the subject. To further illustrate this evolutional process examples from various universities in northern Europe are given. The universities analysed for this purpose presents examples for stages 3-5 in the model; stages represented by a change in courses (stage 3), a change in curricula (stage 4) and by a change in organization (stage 5).
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| 17. |
- Hagqvist, Petter, et al.
(författare)
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Resistance based iterative learning control of additive manufacturing with wire
- 2015
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Ingår i: Mechatronics (Oxford). - : Elsevier BV. - 0957-4158 .- 1873-4006. ; 31, s. 116-123
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Tidskriftsartikel (refereegranskat)abstract
- This paper presents successful feed forward control of additive manufacturing of fully dense metallic components. The study is a refinement of former control solutions of the process, providing more robust and industrially acceptable measurement techniques. The system uses a solid state laser that melts metal wire, which in turn is deposited and solidified to build the desired solid feature on a substrate. The process is inherently subjected to disturbances that might hinder consecutive layers to be deposited appropriately. The control action is a modified wire feed rate depending on the surface of the deposited former layer, in this case measured as a resistance. The resistance of the wire stick-out and the weld pool has shown to give an accurate measure of the process stability, and a solution is proposed on how to measure it. By controlling the wire feed rate based on the resistance measure, the next layer surface can be made more even. A second order iterative learning control algorithm is used for determining the wire feed rate, and the solution is implemented and validated in an industrial setting for building a single bead wall in titanium alloy. A comparison is made between a controlled and an uncontrolled situation when a relevant disturbance is introduced throughout all layers. The controller proves to successfully mitigate these disturbances and maintain stable deposition while the uncontrolled deposition fails.
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| 18. |
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| 19. |
- Hultman, Erik, et al.
(författare)
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An updated cable feeder tool design for robotized stator cable winding
- 2018
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Ingår i: Mechatronics. - : Elsevier BV. - 0957-4158 .- 1873-4006. ; 49, s. 197-210
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Tidskriftsartikel (refereegranskat)abstract
- We have previously suggested a method for robotized stator winding of cable wound electric machines and demonstrated the method successfully in full-scale experiments. The cable feeder tool used to handle the cable during the complete winding process is an essential component of this robot cell. To take the robot winding method to the next level, into an industrial product, require further developments regarding durability, independency, flexibility and implementability. In this paper, we present an updated cable feeder tool design. This tool is designed to be used in a robot cell for cable winding of the third-generation design of the Uppsala University Wave Energy Converter generator stator. In this work, three cable feeder tool prototypes have been constructed, experimentally evaluated and validated for the intended application. Key performance parameters are presented and discussed, including suggestions for further developments. We completed a durable, compact, high performance tool design, with fully integrated control into industrial robot controllers. The experimental results presented in this article are very promising and hence, the updated cable feeder tool design represents another important step towards an industrial solution for robotized stator cable winding.
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| 20. |
- Ji, Qinglei, et al.
(författare)
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Design and calibration of 3D printed soft deformation sensors for soft actuator control
- 2023
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Ingår i: Mechatronics (Oxford). - : Elsevier BV. - 0957-4158 .- 1873-4006. ; 92, s. 102980-102980
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Tidskriftsartikel (refereegranskat)abstract
- Soft actuators made from compliant materials are superior to conventional rigid robots in terms of flexibility, adaptability and safety. However, an inherent drawback of soft actuator is the low actuation precision. Implementing closed loop control is a possible solution, but the soft actuator shape can hardly be measured directly by commercially available sensors, which either are too stiff for integration or cause performance degradation of the actuator. Although 3D printing has been applied to print bendable sensors from conductive materials, they either have larger stiffness than the soft actuator or are made from specially designed materials that are difficult to reproduce. In this study, easily accessible commercial soft conductive material is applied to directly 3D print soft sensors on soft actuators. Different configurations of the printed sensors are studied to investigate how the sensor design affects the performance. The best sensor configuration is selected to provide shape feedback using its changing resistance during deformation. Compared with a commercial flexible bending sensor, the printed sensor has less influences on the soft actuator performance and enjoys higher shape estimation accuracy. Closed loop shape control of the actuator using feedback from the 3D printed sensor is then designed, implemented and compared with the control results using image feedback. A gripper consisting of three individually controlled soft actuators demonstrates the applications of the soft sensor.
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| 21. |
- Jonasson, Mats, et al.
(författare)
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Design and evaluation of an active electromechanical wheel suspension system
- 2008
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Ingår i: Mechatronics (Oxford). - : Elsevier BV. - 0957-4158 .- 1873-4006. ; 18:4, s. 218-230
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Tidskriftsartikel (refereegranskat)abstract
- This paper presents an electromechanical wheel suspension, where the upper arm of the suspension has been provided with an electric levelling and a damper actuator, both are allowed to work in a fully active mode. A control structure for the proposed suspension is described. The complex design task involving the control of the electric damper and its machine parameters is tackled by genetic optimisation. During this process, these parameters are optimised to keep the power dissipation of the electric damper as low as possible, while maintaining acceptable comfort and road-holding capabilities. The results of the evaluations carried out demonstrate that the proposed suspension can easily adopt its control parameters to obtain a better compromise of performance than that offered by passive suspensions. If the vehicle is to maintain acceptable performance during severe driving conditions, the damper has to be unrealistically large. However, if the electric damper is combined with a hydraulic damper, the size of the electric damper is significantly reduced. In addition, the design of the electric damper with the suggested control structure, including how it regenerates energy, is discussed.
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| 22. |
- La Hera, Pedro, 1981-, et al.
(författare)
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New approach for swinging up the Furuta pendulum : theory and experiments
- 2009
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Ingår i: Mechatronics (Oxford). - : Elsevier BV. - 0957-4158 .- 1873-4006. ; 19:8, s. 1240-1250
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Tidskriftsartikel (refereegranskat)abstract
- The problem of swinging up inverted pendulums has often been solved by stabilizing a particular class of homoclinic structures present in the dynamics of a physical pendulum. Here, new arguments are suggested to show how other homoclinic curves can be preplanned for dynamics of the passive-link of the robot. This is done by reparameterizing the motions according to geometrical relations among the generalized coordinates, which are known as virtual holonomic constraints. After that, conditions that guarantee the existence of periodic solutions surrounding the planned homoclinic orbits are derived. The corresponding trajectories, in contrast to homoclinic curves, admit efficient design of feedback control laws ensuring exponential orbital stabilization. The method is illustrated by simulations and supported by experimental studies on the Furuta pendulum. The implementation issues are discussed in detail.
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| 23. |
- Li, Yufeng, et al.
(författare)
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Model reference discrete-time sliding mode control of linear motor precision servo systems
- 2004
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Ingår i: Mechatronics (Oxford). - : Elsevier BV. - 0957-4158 .- 1873-4006. ; 14:7, s. 835-851
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Tidskriftsartikel (refereegranskat)abstract
- This paper studies high-precision motion control of linear motor servo systems. A model reference discrete-time sliding mode control is constructed, which converts servo problems to simple regulator problems. Moreover, based on one-step delayed disturbance approximation, unknown disturbances, including friction, can be well compensated without using any complicated friction modelling and corresponding on-line identification techniques, hence the design of the controller is simple and satisfactory performance is easy to achieve. For tracking control, the overall tracking errors can be further reduced by introducing an extra integral action, although it is not possible to completely eliminate the friction effect in the case that reference trajectories cross zero velocity. Since friction is a complicated non-smooth disturbance, detailed investigation on the influence of choice of sampling period on friction compensation performance is performed through simulation analysis. Experimental results are presented to illustrate the effectiveness and achievable control performance of the proposed scheme.
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| 24. |
- Masud, Nauman, et al.
(författare)
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Design, control, and actuator selection of a lower-body assistive exoskeleton with 3-D passive compliant supports
-
Ingår i: Mechatronics (Oxford). - 0957-4158 .- 1873-4006.
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Tidskriftsartikel (refereegranskat)abstract
- Physical human-robotic interaction is a crucial area of concern for robotic exoskeletons. Lower weight requirement for the worn exoskeletons limits the number and size of joint actuators, resulting in a low active degree of freedom for the exoskeletons with joint actuators having limited power and bandwidth. This limitation invariably results in reduced physical human-robotic interaction performance for the exoskeleton. Recently several techniques have been proposed for the low-active-degree-of-freedom-exoskeletons with improved physical human-robotic interaction performance using better load-torque compensators and improved active compliance. However, effective practical implementation of these techniques requires special hardware and software design considerations. A detailed design of a new lower-body exoskeleton is presented in this paper that can apply these recently developed techniques to practically improve the physical human-robotic interaction performance of the worn-exoskeletons. The design presented includes the exoskeleton's structural design, new joint assemblies, and the design of novel 3-D passive, compliant supports. A methodology of selecting and verifying the joint actuators and estimating the desired assistive forces at the contact supports based on human-user joint torque requirements and the degree of assistance is also thoroughly presented. A new CAN-based master-slave control architecture that supports the implementation of recent techniques for improved physical human-robotic interaction is also fully presented. A new control strategy capable of imparting simultaneous impedance-based force tracking control of the exoskeleton in task-space using DOB-based-DLTC at joint-space is also thoroughly presented.
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| 25. |
- Masud, Nauman, et al.
(författare)
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Disturbance observer based dynamic load torque compensator for assistive exoskeletons
- 2018
-
Ingår i: Mechatronics (Oxford). - : Elsevier Ltd. - 0957-4158 .- 1873-4006. ; 54, s. 78-93
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Tidskriftsartikel (refereegranskat)abstract
- In assistive robotics applications, the human limb is attached intimately to the robotic exoskeleton. The coupled dynamics of the human-exoskeleton system are highly nonlinear and uncertain, and effectively appear as uncertain load-torques at the joint actuators of the exoskeleton. This uncertainty makes the application of standard computed torque techniques quite challenging. Furthermore, the need for safe human interaction severely limits the gear ratio of the actuators. With small gear ratios, the uncertain joint load-torques cannot be ignored and need to be effectively compensated. A novel disturbance observer based dynamic load-torque compensator is hereby proposed and analysed for the current controlled DC-drive actuators of the exoskeleton, to effectively compensate the said uncertain load-torques at the joint level. The feedforward dynamic load-torque compensator is proposed based on the higher order dynamic model of the current controlled DC-drive. The dynamic load-torque compensator based current controlled DC-drive is then combined with a tailored feedback disturbance observer to further improve the compensation performance in the presence of drive parametric uncertainty. The proposed compensator structure is shown both theoretically and practically to give significantly improved performance w.r.t disturbance observer compensator alone and classical static load-torque compensator, for rated load-torque frequencies up to 1.6 Hz, which is a typical joint frequency bound for normal daily activities for elderly. It is also shown theoretically that the proposed compensator achieves the improved performance with comparable reference current requirement for the current controlled DC-drive.
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| 26. |
- Masud, Nauman, et al.
(författare)
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Modeling and control of a 4-ADOF upper-body exoskeleton with mechanically decoupled 3-D compliant arm-supports for improved-pHRI
- 2021
-
Ingår i: Mechatronics (Oxford). - : Elsevier. - 0957-4158 .- 1873-4006. ; 73
-
Tidskriftsartikel (refereegranskat)abstract
- Safe physical human-robotic interaction is a crucial concern for worn exoskeletons where lower weight requirement limits the number and size of actuators to be used. A novel control strategy is suggested in this paper for the low degree of freedom exoskeletons, by combining proposed mechanically decoupled passive-compliant arm-supports with active compliance, to achieve an improved and safer physical-human-robotic-interaction performance, while considering the practical limitations of low-power actuators. The approach is further improved with a novel vectoral-form of disturbance observer-based dynamic load-torque compensator, proposed to linearize and decouple the nonlinear human-machine dynamics effectively. The design of a four-degree of freedom exoskeleton test-rig that can assure the implementation of the proposed strategy is also shortly presented. It is shown through simulation and experimentation, that the use of proposed strategy results in an improved and safer physical human-robotic interaction, for the exoskeletons using limited-power actuators. It is also shown both through simulation and experimentation, that the proposed vectoral-form of disturbance based dynamic load-toque compensator, effectively outperforms the other traditional compensators in compensating the load-torques at the joints of the exoskeleton.
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| 27. |
- Masud, Nauman, et al.
(författare)
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On stability and performance of disturbance observer-based-dynamic load torque compensator for assistive exoskeleton : A hybrid approach
- 2020
-
Ingår i: Mechatronics (Oxford). - : Elsevier. - 0957-4158 .- 1873-4006. ; 69
-
Tidskriftsartikel (refereegranskat)abstract
- A disturbance observer-based-dynamic load-torque compensator for current-controlled DC-drives, as joint actuator of assistive exoskeletons, has been recently proposed. It has been shown that this compensator can effectively linearize and decouple the coupled nonlinear dynamics of the human-exoskeleton system, by more effectively compensating the associated nonlinear load-torques of the exoskeleton at the joint level. In this paper, a detailed analysis of the current controlled DC drive-servo system using the said compensator, with respect to performance and stability is presented, highlighting the key factors and considerations affecting both the stability and performance of the compensated servo system. It is shown both theoretically and through simulation results that the stability of the compensated servo system is compromised as performance is increased and vice-versa. Based on the saturation state of the servo system, a new hybrid switching control strategy is then proposed to select stability or performance-based compensator and controller optimally. The strategy is then experimentally verified both at the joint and task space level by using the developed four active-degree of freedom exoskeleton test rig.
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| 28. |
- Murgovski, Nikolce, 1980, et al.
(författare)
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Component sizing of a plug-in hybrid electric powertrain via convex optimization
- 2012
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Ingår i: Mechatronics. - : Elsevier BV. - 0957-4158 .- 1873-4006. ; 22:1, s. 106-120
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Tidskriftsartikel (refereegranskat)abstract
- This paper presents a novel convex modeling approach which allows for a simultaneous optimization of battery size and energy management of a plug-in hybrid powertrain by solving a semidefinite convex problem. The studied powertrain belongs to a city bus which is driven along a perfectly known bus line with fixed charging infrastructure. The purpose of the paper is to present the convexifying methodology and validate the necessary approximations by comparing with results obtained by Dynamic Programming when using the original nonlinear, non-convex, mixed-integer models. The comparison clearly shows the importance of the gear and engine on/off decisions, and it also shows that the convex optimization and Dynamic Programming point toward similar battery size and operating cost when the same gear and engine on/off heuristics are used. The main conclusion in the paper is that due to the low computation time, the convex modeling approach enables optimization of problems with two or more state variables, e.g. allowing for thermal models of the components; or to include more sizing variables, e.g. sizing of the engine and the electric machine simultaneously.
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| 29. |
- Olofsson, Bjorn, et al.
(författare)
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Path-tracking velocity control for robot manipulators with actuator constraints
- 2017
-
Ingår i: Mechatronics (Oxford). - : PERGAMON-ELSEVIER SCIENCE LTD. - 0957-4158 .- 1873-4006. ; 45, s. 82-99
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Tidskriftsartikel (refereegranskat)abstract
- An algorithm for high-performance path tracking for robot manipulators in the presence of model uncertainties and actuator constraints is presented. The path to be tracked is assumed given, and the nominal trajectories are computed using, for example, well-known algorithms for time-optimal path tracking. For online path tracking, the nominal, feedforward trajectories are combined with feedback in a control architecture with a secondary controller, such that robustness to uncertainties in model or environment is achieved. The control law is based on existing path-velocity control (PVC), or so called online time scaling, but in addition to speed adaptation along the tangent of the path, the algorithm also comprises an explicit formulation and approach, with several attractive properties, for handling the deviations along the transversal directions of the path. For achieving fast convergence along the normal and binormal directions of the path in 3D motion, the strategy proposed has inherent exponential convergence properties. The result is a complete architecture for path-tracking velocity control (PTVC). The method is evaluated in extensive simulations with manipulators of different complexity, and PTVC exhibits superior performance compared to PVC. (C) 2017 Elsevier Ltd. All rights reserved.
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| 30. |
- Olofsson, Björn, et al.
(författare)
-
Path-tracking velocity control for robot manipulators with actuator constraints
- 2017
-
Ingår i: Mechatronics. - : Elsevier BV. - 0957-4158 .- 1873-4006. ; 45, s. 82-99
-
Tidskriftsartikel (refereegranskat)abstract
- An algorithm for high-performance path tracking for robot manipulators in the presence of model uncertainties and actuator constraints is presented. The path to be tracked is assumed given, and the nominal trajectories are computed using, for example, well-known algorithms for time-optimal path tracking. For online path tracking, the nominal, feedforward trajectories are combined with feedback in a control architecture with a secondary controller, such that robustness to uncertainties in model or environment is achieved. The control law is based on existing path-velocity control (PVC), or so called online time scaling, but in addition to speed adaptation along the tangent of the path, the algorithm also comprises an explicit formulation and approach, with several attractive properties, for handling the deviations along the transversal directions of the path. For achieving fast convergence along the normal and binormal directions of the path in 3D motion, the strategy proposed has inherent exponential convergence properties. The result is a complete architecture for path-tracking velocity control (PTVC). The method is evaluated in extensive simulations with manipulators of different complexity, and PTVC exhibits superior performance compared to PVC.
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| 31. |
- Oomen, Tom, et al.
(författare)
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Sparse iterative learning control with application to a wafer stage : Achieving performance, resource efficiency, and task flexibility
- 2017
-
Ingår i: Mechatronics (Oxford). - : PERGAMON-ELSEVIER SCIENCE LTD. - 0957-4158 .- 1873-4006. ; 47, s. 134-147
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Tidskriftsartikel (refereegranskat)abstract
- Trial-varying disturbances are a key concern in Iterative Learning Control (ILC) and may lead to inefficient and expensive implementations and severe performance deterioration. The aim of this paper is to develop a general framework for optimization-based ILC that allows for enforcing additional structure, including sparsity. The proposed method enforces sparsity in a generalized setting through convex relaxations using el norms. The proposed ILC framework is applied to the optimization of sampling sequences for resource efficient implementation, trial-varying disturbance attenuation, and basis function selection. The framework has a large potential in control applications such as mechatronics, as is confirmed through an application on a wafer stage.
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| 32. |
- Ragusila, Victor, et al.
(författare)
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Mechatronics by analogy and application to legged locomotion
- 2016
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Ingår i: Mechatronics (Oxford). - : Elsevier BV. - 0957-4158 .- 1873-4006. ; 35, s. 173-191
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Tidskriftsartikel (refereegranskat)abstract
- A new design methodology for mechatronic systems, dubbed as Mechatronics by Analogy (MbA), is introduced. It argues that by establishing a similarity relation between a complex system and a number of simpler models it is possible to design the former using the analysis and synthesis means developed for the latter. The methodology provides a framework for concurrent engineering of complex systems while maintaining the transparency of the system behavior through making formal analogies between the system and those with more tractable dynamics. The application of the MbA methodology to the design of a monopod robot leg, called the Linkage Leg, is also presented. A series of simulations show that the dynamic behavior of the Linkage Leg is similar to that of a combination of a double pendulum and a spring-loaded inverted pendulum, based on which the system kinematic, dynamic, and control parameters can be designed concurrently.
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| 33. |
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| 34. |
- Roos, Fredrik, et al.
(författare)
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Optimal Selection of motor and gearhead in mechatronic applications
- 2006
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Ingår i: Mechatronics (Oxford). - : Elsevier BV. - 0957-4158 .- 1873-4006. ; 16:1, s. 63-72
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Tidskriftsartikel (refereegranskat)abstract
- A method for the selection of motor and gearhead in mechatronic applications is proposed. The method is applicable to any kind of load and helps to find the optimal motor gearhead combination with respect to output torque, peak power, mass/size and/or cost. The input to the method is the load cycle and component data on candidate motors and gearheads. Output is a set of graphs of all motor/gear ratio combinations that can drive the given load. From these graphs it is easy to read out the peak power, motor torque and energy efficiency for all feasible motor/gear ratio combinations.
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| 35. |
- Smith, Christian, et al.
(författare)
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A predictor for operator input for time-delayed teleoperation
- 2010
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Ingår i: Mechatronics (Oxford). - : Elsevier BV. - 0957-4158 .- 1873-4006. ; 20:7, s. 778-786
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Tidskriftsartikel (refereegranskat)abstract
- In this paper we describe a method for bridging Internet time delays in a free motion type teleoperation scenario in an unmodeled remote environment with video feedback The method proposed uses minimum jerk motion models to predict the input from the user a time into the future that is equivalent to the round-trip communication delay The predictions are then used to control a remote robot Thus the operator can in effect observe the resulting motion of the remote robot with virtually no time-delay even in the presence of a delay on the physical communications channel We present results from a visually guided teleoperated line tracing experiment with 100 ms round-trip delays where we show that the proposed method makes a significant performance improvement for teleoperation with delays corresponding to intercontinental distances.
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| 36. |
- Törngren, Martin, et al.
(författare)
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Integrating viewpoints in the development of mechatronic products
- 2014
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Ingår i: Mechatronics (Oxford). - : Elsevier BV. - 0957-4158 .- 1873-4006. ; 24:7, s. 745-762
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Tidskriftsartikel (refereegranskat)abstract
- The development of mechatronic products involves multiple stakeholders which have different viewpoints and therefore use different concepts, models and tools to deal with their concerns of interest. This paper argues that an increased emphasis needs to be placed on the relations between viewpoints to be able to deal with the evolving scope and requirements on mechatronic products. We study relations between viewpoints at the levels of people, models and tools, and present solutions that are used to formally and explicitly capture such relations. Viewpoint contracts are used to define the vocabulary, assumptions and constraints required for ensuring smooth communication between stakeholders (people level). Dependency models capture relations between product properties belonging to different viewpoints, and how such dependencies relate to predictions and decisions (model level). Tool integration models describe the relations between tools in terms of traceability, data exchange, invocation and notifications (tool level). A major contribution of this paper is a unification approach, elaborating how these solutions can be used synergetically to integrate viewpoints. An industrial robot case study is utilized to illustrate the challenges and solutions with respect to relations between viewpoints, including the unification approach.
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| 37. |
- Åstrand, Björn, et al.
(författare)
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A vision based row-following system for agricultural field machinery
- 2005
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Ingår i: Mechatronics (Oxford). - Amsterdam : Elsevier. - 0957-4158 .- 1873-4006. ; 15:2, s. 251-269
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Tidskriftsartikel (refereegranskat)abstract
- In the future, mobile robots will most probably navigate through the fields autonomously to perform different kind of agricultural operations. As most crops are cultivated in rows, an important step towards this long-term goal is the development of a row-recognition system, which will allow a robot to accurately follow a row of plants. In this paper we describe a new method for robust recognition of plant rows based on the Hough transform. Our method adapts to the size of plants, is able to fuse information coming from two rows or more and is very robust against the presence of many weeds. The accuracy of the position estimation relative to the row proved to be good with a standard deviation between 0.6 and 1.2 cm depending on the plant size. The system has been tested on both an inter-row cultivator and a mobile robot. Extensive field tests have showed that the system is sufficiently accurate and fast to control the cultivator and the mobile robot in a closed-loop fashion with a standard deviation of the position of 2.7 and 2.3 cm, respectively. The vision system is also able to detect exceptional situations by itself, for example the occurrence of the end of a row.
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| 38. |
- Johansson, Rolf, et al.
(författare)
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State-Space System Identification of Robot Manipulator Dynamics
- 2000
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Ingår i: Mechatronics. - 0957-4158. ; 10:3, s. 403-418
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Tidskriftsartikel (refereegranskat)abstract
- We have applied and evaluated system identification methods using both commercial software and dedicated subspace model identification software (MOESP). Results using the different software tools have been similar (but not identical) in accuracy and predictive power, the main differences being the time required for computation and occasional failures of one algorithm in delivery of a stable model. For linear model identification all methods tested failed to provide residuals, i.e. model misfit, uncorrelated with input and without significant autocorrelation. As a result, no linear stochastic innovations model could be formulated in any satisfactory manner. However, model-order tests based on singular values suggest that a low model order be sufficient for input-output modeling to within a modeling accuracy of 2-5%. Thus, the identification of a state-space model combined with a friction model provides effective means to modeling in robotics.
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| 39. |
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| 40. |
- Boyraz Baykas, Pinar, 1981, et al.
(författare)
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Dynamic Modeling of a Horizontal Washing Machine and Optimization of Vibration Characteristics using Genetic Algorithms
- 2013
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Ingår i: Mechatronics. - : Elsevier BV. - 0957-4158. ; 23:6, s. 581-593
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Tidskriftsartikel (refereegranskat)abstract
- In this work, a 2D dynamic model of a horizontal axis washing machine is derived regarding the rotation plane in order to examine the vibration characteristics of the spin-cycle and improve the design proposing a new optimization scheme based on Genetic Algorithms (GA). The dynamic model is numerically simulated and the outputs are validated using experimental vibration data acquired from a test-rig including the drum and the motor of a horizontal-axis washing machine. The measurements are performed using piezo-transducers and a novel measurement scheme is used to obtain displacement values from acceleration data as well as estimating the instantaneous frequency of the rotation with appropriate signal processing. This study has two main contributions: (i) a new method for design improvement applying GA to optimization of vibration characteristics for the horizontal-axis washing machines, and (ii) a novel measurement method yielding the displacement in 2D and instantaneous frequency of vibration from acceleration data. While the GA is contributing to passive improvement methods in the field, the novel measurement method opens the way for low-cost diagnosis and active-vibration control of washing machines.
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| 41. |
- Oddo, Calogero Maria, 1983, et al.
(författare)
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A mechatronic platform for human touch studies
- 2011
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Ingår i: Mechatronics. - : Elsevier BV. - 0957-4158. ; 21:3, s. 604-613
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Tidskriftsartikel (refereegranskat)abstract
- The development of a mechatronic tactile stimulation platform for touch studies is presented. The platform was developed for stimulation of the fingertip using textured surfaces, providing repeatable tangential sliding motion of stimuli with controlled indentation force. Particular requirements were addressed to make the platform suitable for neurophysiological studies in humans with particular reference to electrophysiological measurements, but allowing a variety of other studies too, such as psychophysical, tri-bological and artificial touch ones. The design of the mechatronic tactile stimulator is detailed, as well as the performance in tracking reference trajectories. Using microneurography, we recorded from human tactile afferents and validated the platform compatibility with the exacting demands of electrophysiological methods, comprising the absence of spurious vibrations and the lack of relevant electromagnetic interference.
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| 42. |
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| 43. |
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| 44. |
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| 45. |
- Simoni, Luca, et al.
(författare)
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Inclusion of the dwell time effect in the LuGre friction model
- 2020
-
Ingår i: Mechatronics. - : Elsevier BV. - 0957-4158. ; 66
-
Tidskriftsartikel (refereegranskat)abstract
- The Dahl friction model is a simple dynamic model for friction obtained by adding dynamics to the stress strain curve. The model captures many aspects of friction and has been used for simulation for a long time. A drawback with the model is that it does not display the stick-slip effect. The LuGre friction model extends the Dahl model to capture the stick-slip motion but is does not capture the fact that friction increases between two surfaces in contact. In this paper we extend the LuGre model to include the effects of dwell time. The model is verified with experiments.
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| 46. |
- Neshat, M., et al.
(författare)
-
Short-term solar radiation forecasting using hybrid deep residual learning and gated LSTM recurrent network with differential covariance matrix adaptation evolution strategy
- 2023
-
Ingår i: Energy. - : Elsevier Ltd. - 0360-5442 .- 1873-6785. ; 278
-
Tidskriftsartikel (refereegranskat)abstract
- Developing an accurate and robust prediction of long-term average global solar irradiation plays a crucial role in industries such as renewable energy, agribusiness, and hydrology. However, forecasting solar radiation with a high level of precision is historically challenging due to the nature of this source of energy. Challenges may be due to the location constraints, stochastic atmospheric parameters, and discrete sequential data. This paper reports on a new hybrid deep residual learning and gated long short-term memory recurrent network boosted by a differential covariance matrix adaptation evolution strategy (ADCMA) to forecast solar radiation one hour-ahead. The efficiency of the proposed hybrid model was enriched using an adaptive multivariate empirical mode decomposition (MEMD) algorithm and 1+1EA-Nelder–Mead simplex search algorithm. To compare the performance of the hybrid model to previous models, a comprehensive comparative deep learning framework was developed consisting of five modern machine learning algorithms, three stacked recurrent neural networks, 13 hybrid convolutional (CNN) recurrent deep learning models, and five evolutionary CNN recurrent models. The developed forecasting model was trained and validated using real meteorological and Shortwave Radiation (SRAD1) data from an installed offshore buoy station located in Lake Michigan, Chicago, United States, supported by the National Data Buoy Centre (NDBC). As a part of pre-processing, we applied an autoencoder to detect the outliers in improving the accuracy of solar radiation prediction. The experimental results demonstrate that, firstly, the hybrid deep residual learning model performed best compared with other machine learning and hybrid deep learning methods. Secondly, a cooperative architecture of gated recurrent units (GRU) and long short-term memory (LSTM) recurrent models can enhance the performance of Xception and ResNet. Finally, using an effective evolutionary hyper-parameters tuner (ADCMA) reinforces the prediction accuracy of solar radiation.
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| 47. |
- Neshat, Mehdi, et al.
(författare)
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Wind turbine power output prediction using a new hybrid neuro-evolutionary method
- 2021
-
Ingår i: Energy. - : Elsevier BV. - 0360-5442 .- 1873-6785. ; 229
-
Tidskriftsartikel (refereegranskat)abstract
- Short-term wind power prediction is challenging due to the chaotic characteristics of wind speed. Since, for wind power industries, designing an accurate and reliable wind power forecasting model is essential, we deployed a novel composite deep learning-based evolutionary approach for accurate forecasting of the power output in wind-turbine farms, which is developed in three stages. At the beginning stage (pre -processing), the k-means clustering method and an autoencoder are employed to detect and filter noise in the SCADA measurements. In the Next step (decomposition), in order to decompose the SCADA time -series data, we proposed a new hybrid variational mode decomposition (HVMD) method, that consists of VMD and two heuristics: greedy Nelder-Mead search algorithm (GNM) and adaptive randomised local search (ARLS). Both heuristics are applied to tune the hyper-parameters of VMD that results in improving the performance of the forecasting model. In the third phase, based on prior knowledge that the un-derlying wind patterns are highly non-linear and diverse, we proposed a novel alternating optimisation algorithm that consists of self-adaptive differential evolution (SaDE) algorithm and sine cosine optimi-sation method as a hyper-parameter optimizer and then combine with a recurrent neural network (RNN) called Long Short-term memory (LSTM). This framework allows us to model the power curve of a wind turbine on a farm. A historical dataset from supervisory control and data acquisition (SCADA) systems were applied as input to estimate the power output from an onshore wind farm in Sweden. Two short time forecasting horizons, including 10 min ahead and 1 h ahead, are considered in our experiments. The achieved prediction results supported the superiority of the proposed hybrid model in terms of accurate forecasting and computational runtime compared with earlier published hybrid models applied in this paper.
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| 48. |
- Trenkwalder, Claudia, et al.
(författare)
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Expert Consensus Group report on the use of apomorphine in the treatment of Parkinson's disease - Clinical practice recommendations
- 2015
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Ingår i: Parkinsonism & Related Disorders. - : Elsevier BV. - 1873-5126 .- 1353-8020. ; 21:9, s. 1023-1030
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Forskningsöversikt (refereegranskat)abstract
- Extensive published evidence supports the use of subcutaneously-administered apomorphine as an effective therapy for Parkinson's disease (PD) but to date no consensus recommendations have been available to guide healthcare professionals in the optimal application of apomorphine therapy in clinical practice. This document outlines best-practice recommendations for selecting appropriate candidates for apomorphine intermittent injection (the pen-injection formulation) or apomorphine continuousinfusion (the pump formulation), for initiating patients onto therapy and for managing their ongoing treatment. Apomorphine is a suitable therapeutic option for PD patients who experience troublesome 'off periods despite optimized treatment with oral PD medications. Due to its speed of onset, apomorphine injection is particularly suited to those patients requiring rapid, reliable relief of both unpredictable and predictable 'off' periods, those who require reliable and fast relief when anticipating an 'off', those with levodopa absorption or gastric emptying problems resulting in delayed or failed 'on', or for rapid relief of early morning dystonia or akinesia. Apomorphine infusionl is suited for patients whose 'off periods can no longer be adequately controlled by standard oral PD treatment or for those in whom rescue doses of apomorphine injection are effective but either needed too frequently (more than 4-6 times per day), or are associated with increasing dyskinesia. In addition to treating motor fluctuations, there is evidence that apomorphine infusion may be effective for the management of specific non-motor symptoms of PD associated with 'off' periods. Apomorphine infusion is less invasive than other non-oral treatment options for advancing disease, intrajejunal levodopa infusion and deep-brain stimulation. (C) 2015 Elsevier Ltd. All rights reserved.
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| 49. |
- Hemminki, Kari, et al.
(författare)
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Subsequent Autoimmune or Related Disease in Asthma Patients: Clustering of Diseases or Medical Care?
- 2010
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Ingår i: Annals of Epidemiology. - : Elsevier BV. - 1047-2797 .- 1873-2585. ; 20, s. 217-222
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Tidskriftsartikel (refereegranskat)abstract
- PURPOSE: Asthma includes immunological components that may share mechanisms with autoimmune diseases. We analyzed the subsequent occurrence of any of 22 autoimmune and related conditions in hospitalized asthma patients. METHODS: A nationwide study was conducted in Sweden on subsequent diseases of asthma patients on the basis of the Hospital Discharge Register. Standardized incidence ratios (SIRs) were calculated for subsequent autoimmune diseases. RESULTS: A total of 4006 patients were hospitalized for an autoimmune condition after last hospitalization for asthma. The SIRs were increased for 11 subsequent autoimmune conditions, diagnosed at least 5 years after asthma. The highest SIRs were noted for polyarteritis nodosa (4.29) and Addison disease (3.62). SIRs for these diseases and others, including the most common autoimmune disease rheumatoid arthritis, were increased even when the follow-up was started 5 years after the last asthma hospitalization. Addison disease and Crohn disease were increased in asthma patients hospitalized at various ages, whereas young asthma patients presented with celiac disease and immune thrombocytopenic purpura. CONCLUSIONS: Hospitalized asthma patients presented with a number of subsequent autoimmune and related diseases. Although we were unable to exclude the effects of environmental factors, the data suggest that shared genetic factors or gene-environment interactions may explain coexistence of some of these diseases.
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