Now showing items 1-20 of 74

  • 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 fast branch-and-prune algorithm for the position analysis of spherical mechanisms 

    Shabani, Arya; Sarabandi, Soheil; Porta Pleite, Josep Maria; Thomas, Federico (Springer, 2019)
    Conference report
    Open Access
    Different branch-and-prune schemes can be found in the literature for numerically solving the position analysis of spherical mechanisms. For the prune operation, they all rely on the propagation of motion intervals. They ...
  • 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 ...