Now showing items 1-20 of 70

  • A bilinear formulation for the motion planning of non-holonomic parallel orienting platforms 

    Grosch Obregon, Patrick John; Thomas, Federico (Institute of Electrical and Electronics Engineers (IEEE), 2013)
    Conference report
    Open Access
    This paper deals with the motion planning problem for parallel orienting platforms with one non-holonomic joint and two prismatic actuators which can maneuver to reach any three-degree-of-freedom pose of the moving platform. ...
  • Accurate computation of quaternions from rotation matrices 

    Sarabandi, Soheil; Thomas, Federico (Springer International Publishing, 2018)
    Conference report
    Open Access
    The main non-singular alternative to 3×3 proper orthogonal matrices, for representing rotations in R3, is quaternions. Thus, it is important to have reliable methods to pass from one representation to the other. While ...
  • A coordinate-free approach to tracing the coupler curves of pin-jointed linkages 

    Rojas Libreros, Nicolás Enrique; Thomas, Federico (ASME PRESS, 2011)
    Conference report
    Restricted access - publisher's policy
    In general, high-order coupler curves of plane mechanisms cannot be properly traced by standard predictor-corrector algorithms due to drifting problems and the presence of singularities. Instead of focusing on finding ...
  • A distance-based formulation of the octahedral manipulator kinematics 

    Rojas Libreros, Nicolás Enrique; Borràs Sol, Júlia; Thomas, Federico (2010)
    Conference report
    Open Access
    In most practical implementations of the Gough-Stewart platform, the octahedral form is either taken as it stands or is approximated. The kinematics of this particular instance of the Gough-Stewart platform, commonly known ...
  • A distance geometry approach to the singularity analysis of 3R robots 

    Thomas, Federico (ASME PRESS, 2015)
    Article
    Restricted access - publisher's policy
    This paper shows how the computation of the singularity locus of a 3R robot can be reduced to the analysis of the relative position of two coplanar ellipses. Since the relative position of two conics is a projective ...
  • A family of quadratically-solvable 5-SPU parallel robots 

    Borràs Sol, Júlia; Thomas, Federico; Torras, Carme (2010)
    Conference report
    Open Access
    A 5-SPU robot with collinear universal joints is well suited to handling an axisymmetric tool, since it has 5 controllable DoFs and the remaining one is a free rotation around the tool. The kinematics of such a robot having ...
  • A linear relaxation technique for the position analysis of multi-loop linkages 

    Porta Pleite, Josep Maria; Ros Giralt, Lluís; Thomas, Federico (2008)
    External research report
    Open Access
    This report presents a new method able to isolate all configurations that a multi-loop linkage can adopt. We tackle the problem by providing formulation and resolution techniques that fit particularly well together. The ...
  • A linear relaxation technique for the position analysis of multiloop linkages 

    Porta Pleite, Josep Maria; Ros Giralt, Lluís; Thomas, Federico (2009)
    Article
    Open Access
    This paper presents a new method to isolate all configurations that a multiloop linkage can adopt. The problem is tackled by means of formulation and resolution techniques that fit particularly well together. The adopted ...
  • A matrix-based approach to the image moment problem 

    Martínez Bauzà, Judit; Porta Pleite, Josep Maria; Thomas, Federico (2006-11)
    Article
    Open Access
    An image can be seen as an element of a vector space and hence it can be expressed in as a linear combination of the elements of any non necessarily orthogonal basis of this space. After giving a matrix formulation of this ...
  • Analysing the singularities of 6-SPS parallel robots using virtual legs 

    Borràs Sol, Júlia; Thomas, Federico; Torras, Carme (LIRMM, 2008)
    Conference report
    Open Access
    A virtual leg in a 6-SPS parallel robot is defined as a leg whose length is determined by the lengths of a subset of the actual legs of the robot. This necessarily implies that this subset of legs defines a rigid subassembly. ...
  • A new insight into the coupler curves of the RCCC four-bar linkage 

    Thomas, Federico; Pérez Gracia, Alba (Springer, 2017)
    Conference report
    Open Access
    Based on the condition for four points to lie on the unit sphere, derived using Distance Geometry, a new mathematical formulation for the coupler curves of the RCCC linkage is presented. The relevance of this formulation ...
  • A one-motor full-mobility 6-PUS manipulator 

    Grosch Obregon, Patrick John; Gregorio, Raffaele di; Thomas, Federico (Springer, 2010)
    Conference report
    Open Access
    This paper presents the feasibility study of an under-actuated parallel manipulator with 6-PUS topology, destined to handle work-tables in CNC machine tools. The proposed device exploits the fact that, in such an application, ...
  • Application of distance geometry to tracing coupler curves of pin-jointed linkages 

    Thomas, Federico; Rojas Libreros, Nicolás Enrique (ASME PRESS, 2013)
    Article
    Restricted access - publisher's policy
    In general, high-order coupler curves of single-degree-of-freedom plane linkages cannot be properly traced by standard predictor–corrector algorithms due to drifting problems and the presence of singularities. Instead of ...
  • Approaching dual quaternions from matrix algebra 

    Thomas, Federico (2014)
    Article
    Open Access
    Dual quaternions give a neat and succinct way to encapsulate both translations and rotations into a unified representation that can easily be concatenated and interpolated. Unfortunately, the combination of quaternions and ...
  • Architectural singularities of a class of pentapods 

    Borràs Sol, Júlia; Thomas, Federico; Torras, Carme (2011)
    Article
    Open Access
    A pentapod is usually defined as a 5-degrees-of-freedom fully-parallel manipulator with an axial spindle as moving platform. This kind of manipulators has revealed as an interesting alternative to serial robots handling ...
  • Architecture singularities in flagged parallel manipulators 

    Borràs Sol, Júlia; Thomas, Federico; Torras, Carme (IEEE, 2008)
    Conference report
    Open Access
    Flagged manipulators are of interest because they are the only Stewart-Gough platforms for which a cell decomposition of their singularity loci is available. Here we show that the known family of such manipulators can be ...
  • A reconfigurable 5-DoF 5-SPU parallel platform 

    Borràs Sol, Júlia; Thomas, Federico; Ottaviano, Erika; Ceccarelli, Marco (2009)
    Conference report
    Open Access
    This paper presents a 5-SPU platform whose base leg attachments can be easily reconfigured, statically or dynamically, without altering its singularity locus. This permits to adapt the platform’s geometry to particular ...
  • A reconfigurable asymmetric 3-UPU parallel robot 

    Sarabandi, Soheil; Grosch Obregon, Patrick John; Porta Pleite, Josep Maria; Thomas, Federico (2018)
    Conference report
    Open Access
    Parallel robots with three UPU legs have received a lot of attention due to the possibility of assembling these legs so that the robot performs either a pure translational or a pure rotational motion. Nevertheless, some ...
  • A robust forward kinematics analysis of 3-RPR planar platforms 

    Rojas Libreros, Nicolás Enrique; Thomas, Federico (Springer Verlag, 2010)
    Conference report
    Open Access
    The standard forward kinematics analysis of 3-RPR planar parallel platforms boils down to computing the roots of a sextic polynomial. There are many different ways to obtain this polynomial but all of them include exceptions ...
  • A short account of Leonardo Torres' endless spindle 

    Thomas, Federico (2008)
    Article
    Restricted access - publisher's policy
    At the end of the 19th century, several analog machines had been proposed for solving algebraic equations. These machines – based not only on kinematics principles but also on dynamic or hydrostatic balances, electric or ...