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T. S. Mruthyunjaya - One of the best experts on this subject based on the ideXlab platform.
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a force torque sensor based on a Stewart Platform in a near singular configuration
Mechanism and Machine Theory, 2004Co-Authors: R Ranganath, T. S. Mruthyunjaya, P S Nair, Ashitava GhosalAbstract:It is well known that a parallel mechanism at a singular configuration can gain one or more degrees of freedom instantaneously, and at such a configuration it cannot resist externally applied force/torque along certain directions. At near-singular configurations, small applied force/torque in a certain specific direction can give rise to large forces in the links, thereby resulting in mechanical magnification in link forces. This key idea is used, with a Stewart Platform, in a near-singular configuration, to design a directionally sensitive force–torque sensor. The concept of near-singular configuration and magnification is developed analytically and numerically with the help of a simple planar truss with rotary and flexure joints. A finite element analysis shows that a properly designed flexure joint approximates a rotary joint reasonably well, thus avoiding friction and non-linearities associated with rotary joints. The concept of force magnification and flexural joints is next extended to a Stewart Platform at a near-singular configuration. It is verified, using finite element analysis, that the Stewart Platform at a near-singular configuration with flexural hinges shows large forces in the legs for small external forces and torques applied in certain directions, and thus can be a good design for a highly sensitive force–torque sensor for certain components of applied force/torque. It is also shown, from a singularity analysis of the Stewart Platform, that sensitivity to other components of external force/torque can be obtained by using different near-singular configurations. The theoretical concepts are demonstrated with a prototype sensor which is sensitive to two components of the externally applied force and one component of the externally applied moment.
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design and development of a Stewart Platform based force torque sensor
Mechatronics, 2001Co-Authors: T. A. Dwarakanath, Bhaskar Dasgupta, T. S. MruthyunjayaAbstract:This paper details the design and development of a force–torque sensor based on the Stewart Platform structure. The optimal synthesis of the sensor structure is performed with the objective of achieving well-conditioned transformation between the input and output forces. The influence of size of Platform on sensitivity and the load bearing capacity are discussed in the light of capabilities of available sensing elements. Thus, the design is obtained by satisfying the dual objective of isotropy and sensitivity of the force–torque sensor. Maximization of signal to noise ratio (S/N ratio) is considered at various stages in arriving at various component shapes and dimensions. The above design has been implemented in the development of a compact force–torque sensor.
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the Stewart Platform manipulator a review
Mechanism and Machine Theory, 2000Co-Authors: Bhaskar Dasgupta, T. S. MruthyunjayaAbstract:This paper presents a state-of-the-art review of the literature on the six-degree-of-freedom parallel manipulator commonly known as the Stewart Platform. The existing studies in the field are critically examined to ascertain the trends of research in the field and to identify unsolved problems. The Stewart Platform being representative of the class of parallel manipulators, the concepts applicable for it have direct relevance to the entire class. The distinctions of this class from the conventional serial robot manipulators are also highlighted and the novel perspectives that are necessary for the analysis and design of the Stewart Platform in particular and parallel manipulators in general are recommended.
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a canonical formulation of the direct position kinematics problem for a general 6 6 Stewart Platform
Mechanism and Machine Theory, 1994Co-Authors: Bhaskar Dasgupta, T. S. MruthyunjayaAbstract:This paper deals with the direct position kinematics problem of a general 6-6 Stewart Platform, the complete solution of which is not reported in the literature until now and even establishing the number of possible solutions for the general case has remained an unsolved problem for a long period. Here a canonical formulation of the direct position kinematics problem for a general 6-6 Stewart Platform is presented. The kinematic equations are expressed as a system of six quadratic and three linear equations in nine unknowns, which has a maximum of 64 solutions. Thus, it is established that the mechanism, in general, can have up to 64 closures. Further reduction of the system is shown arriving at a set of three quartic equations in three unknowns, the solution of which will yield the assembly configurations of the general Stewart Platform with far less computational effort compared to earlier models.
Liping Wang - One of the best experts on this subject based on the ideXlab platform.
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research on the dynamic coupling of the rigid flexible manipulator
Robotics and Computer-integrated Manufacturing, 2015Co-Authors: Zhihua Liu, Xiaoqiang Tang, Liping WangAbstract:Because of its large dimension, a rigid-flexible manipulator was designed to serve as the feed support system in a Five-hundred-meter Aperture Spherical radio Telescope (FAST). The rigid-flexible manipulator is composed of a flexible cable-driven parallel manipulator and a rigid Stewart Platform. Motion of the Stewart Platform may induce vibration of the cable-driven parallel manipulator due to reaction forces. The goal of this study is to investigate the dynamic coupling of the rigid-flexible manipulator. The "Virtual Stewart Platform" was introduced to obtain a homogenous matrix to describe how much base motion is produced by a given Stewart Platform motion. On this basis, an index was proposed to characterize the dynamic coupling of the rigid-flexible manipulator. Based on the proposed index, the factors influencing the dynamic coupling are investigated. The proposed index can be considered as a performance index in design and control of the system. Influence of the dynamic coupling on the feedback control of the rigid-flexible manipulator was also discussed. The simulation results showed that the dynamic performance of the rigid-flexible manipulator is strongly determined by the proposed index. The "Virtual Stewart Platform" is introduced to obtain a homogenous matrix to describe how much base motion is produced by a given Platform motion.An index is proposed to characterize the dynamic coupling of the rigid-flexible manipulator.Based on the proposed index, the factors influencing the dynamic coupling are investigated.Influence of the dynamic coupling on the feedback control of the rigid-flexible manipulator is discussed.
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stiffness analysis of a Stewart Platform based parallel kinematic machine
International Conference on Robotics and Automation, 2002Co-Authors: Yuwen Li, Jinsong Wang, Liping WangAbstract:Stiffness is one of the important considerations in the design of Stewart Platform based parallel kinematic machine (PKM). In most stiffness models of PKMs, the machine frames are thought of rigid bodies. In this paper, an approach is presented to establish the stiffness model of a Stewart Platform-based PKM, considering the deformation of the frame. The deformation of legs and the frame is considered as kinematic parameter errors of Stewart Platform. According to the differential error model, the machine structure is decomposed into two subsystems: the parallel links subsystem and the machine frame subsystem. The stiffness matrix of each subsystem is established respectively, assuming that the other one is a rigid structure. By linear superposition of the two subsystems, the stiffness model of the machine structure is obtained. A finite element analysis (FEA) model is used to simulate the physical structure. The FEA results are compared to those derived from a mathematical model, and the comparison shows the validity of this approach.
Chulgoo Kang - One of the best experts on this subject based on the ideXlab platform.
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closed form force sensing of a 6 axis force transducer based on the Stewart Platform
Sensors and Actuators A-physical, 2001Co-Authors: Chulgoo KangAbstract:The 6-axis force transducers based on the Stewart Platform require the solution of forward kinematics of the Stewart Platform in order to obtain force and torque acting on the upper plate from given six leg forces. However, the solution of forward kinematics is not known in a closed form. In this paper, a closed-form solution of the forward kinematics is derived by means of linearization of the inverse kinematics equations, and the derived solution is applied to the calculation of force and torque acting on the transducer. In order to investigate the validity of the proposed method, a prototype of the transducer based on the Stewart Platform is developed and force analysis is conducted. Moreover, the gravity compensation algorithm is proposed to reduce the weight effects of the transducer.
Ashitava Ghosal - One of the best experts on this subject based on the ideXlab platform.
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Design of a semi-regular Stewart Platform manipulator for a de- sired workspace
2016Co-Authors: Debabrata Chatterjee, Ashitava GhosalAbstract:sired workspace The SRSPM is the most widely used and hence the most important Gough-Stewart Platform configuration for various practical applications. Hence design for geomet-rical parameters to achieve optimal performance is of considerable interest. This paper presents a search based algorithm to determine the optimal geometrical parame-ters for the SRSPM for given desired workspace specifi-cations. We have used the knowledge of the generic shape of the workspace as revealed by previous studies, and a few fundamental observations on the effect of va-rying different geometrical parameters on the geometry of the workspace to design an algorithm to solve our design problem. Two main observations used are-- the size of the end effecter determines what volume of the reachable workspace is actually the region over which the tool is orientable in any desired directions and the actuated length can be increased to have a new increased workspace volume
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geometric characterization and parametric representation of the singularity manifold of a 6 6 Stewart Platform manipulator
Mechanism and Machine Theory, 2006Co-Authors: Sandipan Bandyopadhyay, Ashitava GhosalAbstract:In this paper, we present a compact closed-form expression for the singularity manifold of a class of 6-6 Stewart Platform manipulators most commonly used in research and industry. The singularity manifold is obtained as the hyper-surface in the task-space, SE(3), on which the wrench transformation matrix for the top Platform degenerates. This condition leads to an extremely large expression containing algebraic and trigonometric functions of the architecture, position and orientation variables. We present algorithms or effcient symbolic simplicfication of such large expressions. Using these algorithms, for a given architecture and orientation, the singularity manifold is obtained as a cubic surface in $R^3$. The symbolic computations yield a simple parametric expression for the surface in terms of the architectural and orientation parameters of the manipulator, and allows us to completely characterise and visualise the singularity manifold. We show that, in general, the cubic surface is a one-parameter family of hyperbolas in planes parallel to the base of the manipulator. It is further shown that the hyperbola degenerates to a parabola in a unique plane, and to a pair of straight lines in four other planes. The explicit parameterization allows us to obtain the location of each of these special planes analytically. For a given architecture and position, the singularity manifold is a surface in SO(3), which can be, in general, algebraically described by a 6th degree polynomial in the Rodrigue's parameters. In this paper, we present explicit expressions for the polynomial defining the orientation singularity manifold in terms architecture and orientation parameters. The theoretical results are illustrated with several numerical examples.
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a force torque sensor based on a Stewart Platform in a near singular configuration
Mechanism and Machine Theory, 2004Co-Authors: R Ranganath, T. S. Mruthyunjaya, P S Nair, Ashitava GhosalAbstract:It is well known that a parallel mechanism at a singular configuration can gain one or more degrees of freedom instantaneously, and at such a configuration it cannot resist externally applied force/torque along certain directions. At near-singular configurations, small applied force/torque in a certain specific direction can give rise to large forces in the links, thereby resulting in mechanical magnification in link forces. This key idea is used, with a Stewart Platform, in a near-singular configuration, to design a directionally sensitive force–torque sensor. The concept of near-singular configuration and magnification is developed analytically and numerically with the help of a simple planar truss with rotary and flexure joints. A finite element analysis shows that a properly designed flexure joint approximates a rotary joint reasonably well, thus avoiding friction and non-linearities associated with rotary joints. The concept of force magnification and flexural joints is next extended to a Stewart Platform at a near-singular configuration. It is verified, using finite element analysis, that the Stewart Platform at a near-singular configuration with flexural hinges shows large forces in the legs for small external forces and torques applied in certain directions, and thus can be a good design for a highly sensitive force–torque sensor for certain components of applied force/torque. It is also shown, from a singularity analysis of the Stewart Platform, that sensitivity to other components of external force/torque can be obtained by using different near-singular configurations. The theoretical concepts are demonstrated with a prototype sensor which is sensitive to two components of the externally applied force and one component of the externally applied moment.
Sandipan Bandyopadhyay - One of the best experts on this subject based on the ideXlab platform.
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identification of the largest singularity free cylinders in the translational workspace of the semi regular Stewart Platform manipulator
IFToMM World Congress on Mechanism and Machine Science, 2019Co-Authors: Prem Kumar Prasad, Sandipan BandyopadhyayAbstract:This paper presents a method to compute the largest possible cylindrical volume within the translational workspace of the semi-regular Stewart Platform manipulator (SRSPM), which would be free of gain-type singularities. An analytical approach is used in finding the singularity-free regions rather than discretising the workspace into small singularity-free volumes. Comparison with another convex shape, i.e., the sphere, is performed to demonstrate the relative importance and usefulness of using the cylindrical geometry for finding the singularity-free spaces.
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identifying singularity free spheres in the position workspace of semi regular Stewart Platform manipulators
ARK, 2018Co-Authors: Anirban Nag, Vikranth Reddy, Saurav Agarwal, Sandipan BandyopadhyayAbstract:This paper presents a method to compute the largest sphere inside the position-workspace of a semi-regular Stewart Platform manipulator , that is free of gain-type singularities. The sphere is specific to a given orientation of the moving Platform, and is centred at a designated point of interest. The computation is performed in two parts; in the first part, a Computer Algebra System (CAS) is used to derive a set of exact symbolic expressions, which are then used further in a purely numerical manner for faster computation. The method thus affords high computation speed, while retaining the exactness and generic nature of the results. The numerical results are validated against those obtained from an established numerical algebraic geometry tool, namely, Bertini, and are illustrated via an example.
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geometric characterization and parametric representation of the singularity manifold of a 6 6 Stewart Platform manipulator
Mechanism and Machine Theory, 2006Co-Authors: Sandipan Bandyopadhyay, Ashitava GhosalAbstract:In this paper, we present a compact closed-form expression for the singularity manifold of a class of 6-6 Stewart Platform manipulators most commonly used in research and industry. The singularity manifold is obtained as the hyper-surface in the task-space, SE(3), on which the wrench transformation matrix for the top Platform degenerates. This condition leads to an extremely large expression containing algebraic and trigonometric functions of the architecture, position and orientation variables. We present algorithms or effcient symbolic simplicfication of such large expressions. Using these algorithms, for a given architecture and orientation, the singularity manifold is obtained as a cubic surface in $R^3$. The symbolic computations yield a simple parametric expression for the surface in terms of the architectural and orientation parameters of the manipulator, and allows us to completely characterise and visualise the singularity manifold. We show that, in general, the cubic surface is a one-parameter family of hyperbolas in planes parallel to the base of the manipulator. It is further shown that the hyperbola degenerates to a parabola in a unique plane, and to a pair of straight lines in four other planes. The explicit parameterization allows us to obtain the location of each of these special planes analytically. For a given architecture and position, the singularity manifold is a surface in SO(3), which can be, in general, algebraically described by a 6th degree polynomial in the Rodrigue's parameters. In this paper, we present explicit expressions for the polynomial defining the orientation singularity manifold in terms architecture and orientation parameters. The theoretical results are illustrated with several numerical examples.
