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Vincenzo Parenti-castelli – One of the best experts on this subject based on the ideXlab platform.

  • A Fast and Robust Hybrid Method for the Solution of the 6-3 Stewart–Gough Platform Direct Position Analysis
    Journal of Mechanisms and Robotics, 2008
    Co-Authors: Rocco Vertechy, Vincenzo Parenti-castelli

    Abstract:

    A robust and accurate hybrid method for the real-time estimation of the Actual Configuration of 6-3 Stewart-Gough platforms is presented. The method is hybrid since on one hand it requires the use of three extra sensors in addition to the six ones, which measure the lengths of the manipulator legs, and on the other hand it reduces the influence of sensor noise on the pose estimate by means of either an iterative procedure, which is based on the Newton-Raphson scheme, at regular Configurations, or by means of a noniterative procedure, which is based on the study of the null-space of the manipulator Jacobian, in the vicinity of singular Configurations. The method is robust since it does not fail near singular Configurations and it detects the Actual assembly mode of the manipulator. It is also accurate since it always provides a solution, which satisfies the kinematic constraint equations of the manipulator and is rather insensitive to sensor noise. The method is fast since the estimation of the Actual Configuration of the mechanism requires a limited number of operations, which can be executed in real-time. Analytical and numerical results are reported to show the robustness, accuracy, and computational efficiency of the proposed method.

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  • Determination of the Actual Configuration of the General Stewart Platform Using Only One Additional Sensor
    Journal of Mechanical Design, 1999
    Co-Authors: Vincenzo Parenti-castelli, R. Di Gregorio

    Abstract:

    This paper presents a procedure for the determination of the Actual Configuration of the general geometry Stewart platform (GSP), a fully-parallel manipulator that features two rigid bodies connected to each other via spherical pairs by six controlled-length legs. The six leg length measurements, provided by the displacement sensors incorporated in the leg hardware equipment, do not make it possible to uniquely find the GSP Configuration because several Configurations are possible for a given set of leg lengths. Several extra sensors in addition to those incorporated in the leg equipment have been proposed in the literature in order to obtain a one-to-one correspondence between the measurements and the Actual GSP Configuration. The proposed procedure makes use of only one additional displacement sensor and relies upon the analytical results available in the literature for a particular type of Stewart platform. The procedure, which uniquely defines the Actual Configuration of the GSP, is not intended for on-line implementation. Three different algorithms are proposed for computation and their efficiency compared. A case study is reported that confirms the effectiveness of the procedure.

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  • A New Algorithm Based on Two Extra-Sensors for Real-Time Computation of the Actual Configuration of the Generalized Stewart-Gough Manipulator
    Journal of Mechanical Design, 1999
    Co-Authors: Vincenzo Parenti-castelli, R. Di Gregorio

    Abstract:

    It is well known that the direct position analysis of fully-parallel manipulators provides more than one solution, i.e., more than one Configuration of the mechanism is possible for a given set of the actuated variables of motion. Extra information is, thus, necessary to find the Actual Configuration of the manipulator. This paper presents a new algorithm for the real-time computation of the Actual Configuration of the generalized Stewart-Gough manipulator, also known as 6-6 fully-parallel manipulator with general geometry. The proposed algorithm makes use of two extra rotary sensors in addition to five out of the six sensors normally implemented in the servosystems of the manipulator. A one-to-one correspondence between the sensor measurements and the manipulator Configuration is provided. With respect to other algorithms recently presented in the literature, the proposed method greatly reduces the computational burden. Finally a case study shows the effectiveness of the proposed procedure.

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R. Di Gregorio – One of the best experts on this subject based on the ideXlab platform.

  • Determination of the Actual Configuration of the General Stewart Platform Using Only One Additional Sensor
    Journal of Mechanical Design, 1999
    Co-Authors: Vincenzo Parenti-castelli, R. Di Gregorio

    Abstract:

    This paper presents a procedure for the determination of the Actual Configuration of the general geometry Stewart platform (GSP), a fully-parallel manipulator that features two rigid bodies connected to each other via spherical pairs by six controlled-length legs. The six leg length measurements, provided by the displacement sensors incorporated in the leg hardware equipment, do not make it possible to uniquely find the GSP Configuration because several Configurations are possible for a given set of leg lengths. Several extra sensors in addition to those incorporated in the leg equipment have been proposed in the literature in order to obtain a one-to-one correspondence between the measurements and the Actual GSP Configuration. The proposed procedure makes use of only one additional displacement sensor and relies upon the analytical results available in the literature for a particular type of Stewart platform. The procedure, which uniquely defines the Actual Configuration of the GSP, is not intended for on-line implementation. Three different algorithms are proposed for computation and their efficiency compared. A case study is reported that confirms the effectiveness of the procedure.

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  • A New Algorithm Based on Two Extra-Sensors for Real-Time Computation of the Actual Configuration of the Generalized Stewart-Gough Manipulator
    Journal of Mechanical Design, 1999
    Co-Authors: Vincenzo Parenti-castelli, R. Di Gregorio

    Abstract:

    It is well known that the direct position analysis of fully-parallel manipulators provides more than one solution, i.e., more than one Configuration of the mechanism is possible for a given set of the actuated variables of motion. Extra information is, thus, necessary to find the Actual Configuration of the manipulator. This paper presents a new algorithm for the real-time computation of the Actual Configuration of the generalized Stewart-Gough manipulator, also known as 6-6 fully-parallel manipulator with general geometry. The proposed algorithm makes use of two extra rotary sensors in addition to five out of the six sensors normally implemented in the servosystems of the manipulator. A one-to-one correspondence between the sensor measurements and the manipulator Configuration is provided. With respect to other algorithms recently presented in the literature, the proposed method greatly reduces the computational burden. Finally a case study shows the effectiveness of the proposed procedure.

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  • Real-Time Computation of the Actual Posture of the General Geometry 6-6 Fully-Parallel Mechanism Using Two Extra Rotary Sensors
    Journal of Mechanical Design, 1998
    Co-Authors: Vincenzo Parenti-castelli, R. Di Gregorio

    Abstract:

    The paper presents three algorithms for the determination of the Actual Configuration of the general geometry 6-6 fully-parallel mechanism by using two extra rotary sensors in addition to the six ones that are normally implemented in the servosystems of the six actuated legs. The three proposed algorithms provide a one-to-one correspondence between the sensor measurements and the Configuration of the mechanism. Comparison of the three algorithms, that are all for real-time computation, is presented and one of them is shown to be a good compromise between precision and computation time.

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Marc Bonnet – One of the best experts on this subject based on the ideXlab platform.

  • A preconditioned 3-D multi-region fast multipole solver for seismic wave propagation in complex geometries
    Communications in Computational Physics, 2012
    Co-Authors: Stéphanie Chaillat, Jean-françois Semblat, Marc Bonnet

    Abstract:

    The analysis of seismic wave propagation and amplification in complex geological structures requires efficient numerical methods. In this article, following up on recent studies devoted to the formulation, implementation and evaluation of 3-D single- and multi-region elastodynamic fast multipole boundary element methods (FM-BEMs), a simple preconditioning strategy is proposed. Its efficiency is demonstrated on both the single- and multi-region versions using benchmark examples (scattering of plane waves by canyons and basins). Finally, the preconditioned FM-BEM is applied to the scattering of plane seismic waves in an Actual Configuration (alpine basin of Grenoble, France), for which the high velocity contrast is seen to significantly affect the overall efficiency of the multi-region FM-BEM.

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