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  • 1.
    Andrikopoulos, George
    et al.
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Signaler och system.
    Nikolakopoulos, George
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Signaler och system.
    HUmanoid Robotic Leg via pneumatic muscle actuators: implementation and control2018Ingår i: Meccanica (Milano. Print), ISSN 0025-6455, E-ISSN 1572-9648, Vol. 53, nr 1-2, s. 465-480Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    In this article, a HUmanoid Robotic Leg (HURL) via the utilization of pneumatic muscle actuators (PMAs) is presented. PMAs are a pneumatic form of actuation possessing crucial attributes for the implementation of a design that mimics the motion characteristics of a human ankle. HURL acts as a feasibility study in the conceptual goal of developing a 10 degree-of-freedom (DoF) lower-limb humanoid for compliance and postural control, while serving as a knowledge basis for its future alternative use in prosthetic robotics. HURL’s design properties are described in detail, while its 2-DoF motion capabilities (dorsiflexion–plantar flexion, eversion–inversion) are experimentally evaluated via an advanced nonlinear PID-based control algorithm.

  • 2.
    Andrikopoulos, Georgios
    et al.
    Department of Electrical and Computer Science, University of Patras.
    Nikolakopoulos, George
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Signaler och system.
    Manesis, Stamatis
    Department of Electrical and Computer Engineering, University of Patras.
    Design and Development of an Exoskeletal Wrist Prototype via Pneumatic Artificial Muscles2015Ingår i: Meccanica (Milano. Print), ISSN 0025-6455, E-ISSN 1572-9648, Vol. 50, nr 11, s. 2709-2730Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Full or partial loss of function in the shoulder, elbow or wrist is an increasingly common ailment caused by various medical conditions like stroke, occupational and sport injuries, as well as a number of neurological conditions, which increases the need for the development and improvement of upper limb rehabilitation devices. In this article, the design and implementation of the EXOskeletal WRIST (EXOWRIST) prototype is presented. This novel robotic appliance’s motion is achieved via pneumatic artificial muscles, a pneumatic form of actuation possessing crucial attributes for the development of an exoskeleton that is safe, reliable, portable and low-cost. Furthermore, the EXOWRIST’s properties are presented in detail and compared to the recent wrist exoskeleton technology, while its two degrees-of-freedom movement capabilities (extension-flexion, ulnar-radial deviation) are experimentally evaluated via a PID- based control algorithm. Experimental results involving initial testing of the proposed exoskeleton on a healthy human volunteer for the preliminary evaluation of the EXOWRIST’s attributes are also presented.

  • 3.
    Atashipour, Seyed Abdolrahim
    et al.
    Department of Civil, Chemical and Environmental Engineering, Genoa University.
    Sburlati, R.
    Department of Civil, Chemical and Environmental Engineering, Genoa University.
    Atashipour, Seyed Rasoul
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Byggkonstruktion och -produktion.
    Elastic analysis of thick-walled pressurized spherical vessels coated with functionally graded materials2014Ingår i: Meccanica (Milano. Print), ISSN 0025-6455, E-ISSN 1572-9648, Vol. 49, nr 12, s. 2965-2978Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    In recent years, functionally graded material (FGM) has been widely explored in coating technology amongst both academic and industry communities. FGM coatings are suitable substitutes for many typical conventional coatings which are susceptible to cracking, debonding and eventual functional failure due to the mismatch of material properties at the coating/substrate interface. In this study, a thick spherical pressure vessel with an inner FGM coating subjected to internal and external hydrostatic pressure is analyzed within the context of three-dimensional elasticity theory. Young’s modulus of the coating is assumed to vary linearly or exponentially through the thickness, while Poisson’s ratio is considered as constant. A comparative numerical study of FGM versus homogeneous coating is conducted for the case of vessel under internal pressure, and the dependence of stress and displacement fields on the type of coating is examined and discussed.

  • 4.
    Bennitz, Anders
    et al.
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Byggkonstruktion och -produktion.
    Grip, Niklas
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Matematiska vetenskaper.
    Schmidt, Jacob W.
    Technical University of Denmark.
    Thick-walled cylinder theory applied on a conical wedge anchorage2011Ingår i: Meccanica (Milano. Print), ISSN 0025-6455, E-ISSN 1572-9648, Vol. 46, nr 5, s. 959-977Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    In this paper, we derive and examine an analytical model for the internal stresses and strains within the anchorage for a prescribed presetting distance. This model is derived from the theory of thick walled cylinders under the assumptions regarding plane stress and axial symmetry. We simplify the resulting system of ten nonlinear equations and derive a method for solving them numerically. A comparison of plotted results for three different angles on the wedge's outer surface and six different presetting distances follows. These results are also compared to both axi-symmetric and 3D FE (Finite Element) models. Analytical and FE axi-symmetric models show good correspondence, though compared to the 3D FE model, they show a clear difference in the predicted radial stress distribution on the FRP. Thus, the derived analytical model can be a useful and faster alternative to FE modeling of axi-symmetric anchorages. However, the model is of more restricted value and should be complemented by, for example, 3D FE models for other designs.

  • 5.
    Tyapin, Ilya
    et al.
    Luleå tekniska universitet, Institutionen för ekonomi, teknik och samhälle, Innovation och Design.
    Hovland, Geir
    University of Agder.
    The Gantry-Tau parallel kinematic machine: kinematic and elastodynamic design optimisation2011Ingår i: Meccanica (Milano. Print), ISSN 0025-6455, E-ISSN 1572-9648, Vol. 46, nr 1, s. 113-129Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    One of the main advantages of the Gantry-Tau machine is a large accessible workspace/footprint ratio compared to many other parallel machines. The optimal kinematic, elastostatic and elastodynamic design parameters of the machine are still difficult to calculate and this paper introduces an optimisation scheme based on the geometric and functional dependencies to define the workspace and first resonance frequency. This method assumes that each link and universal joint can be described by a mass-spring-damper model and calculates the transfer function from a Cartesian force or torque to Cartesian position or orientation. The evolutionary algorithm based on the complex search method is compared to the gradient-based search function in Matlab integrated optimisation toolbox. Kinematic design obtained by optimisation according to this paper gives a 2D workspace\footprint ratio more than 1.88 and first resonance frequency is more than 50 Hz with components of an existing lab prototype at the University of Agder, Norway.

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