A practical calibration process using partial information for a commercial 
Stewart platform

Chai, Kok-Soon; Young, Ken; Tuersley, Ian

doi:10.1017/s0263574701004027

Cited by 15 publications

(9 citation statements)

References 12 publications

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“…Generally, the calibration of parallel robots is performed using either built-in extra sensors (Daney, 2003) or using external metrology equipment measuring (possibly only partially) the pose of the mobile platform (Andreff et al, 2004;Chai et al, 2002). Clearly, only the second method is suitable for calibrating an existing robot, such as our hexapod.…”

Section: Calibrationmentioning

confidence: 99%

Kinematic characterisation of hexapods for industry

Blaise

Bonev

Monsarrat

et al. 2010

Industrial Robot: An International Journal

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Purpose -The purpose of this paper is to propose two simple tools for the kinematic characterization of hexapods. The paper also aims to share the experience of converting a popular commercial motion base (Stewart-Gough platform, hexapod) to an industrial robot for use in heavy duty aerospace manufacturing processes. Design/methodology/approach -The complete workspace of a hexapod is a six-dimensional entity that is impossible to visualize. Thus, nearly all hexapod manufacturers simply state the extrema of each of the six dimensions, which is very misleading. As a compromise, a special 3D subset of the complete workspace is proposed, an approximation of which can be readily obtained using a computer-aided design (CAD)/computer-aided manufacturing (CAM) software suite, such as computer-aided 3D interactive application (CATIA). While calibration techniques for serial robots are readily available, there is still no generally agreed procedure for calibrating hexapods. The paper proposes a simple calibration method that relies on the use of a laser tracker and requires no programming at all. Instead, the design parameters of the hexapod are directly and individually measured and the few computations involved are performed in a CAD/CAM software such as CATIA. Findings -The conventional octahedral hexapod design has a very limited workspace, though free of singularities. There are important deviations between the actual and the specified kinematic model in a commercial motion base. Practical implications -A commercial motion base can be used as a precision positioning device with its controller retrofitted with state-of-the-art motion control technology with accurate workspace and geometric characteristics. Originality/value -A novel geometric approach for obtaining meaningful measures of the workspace is proposed. A novel, systematic procedure for the calibration of a hexapod is outlined. Finally, experimental results are presented and discussed.

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Section: Calibrationmentioning

confidence: 99%

Kinematic characterisation of hexapods for industry

Blaise

Bonev

Monsarrat

et al. 2010

Industrial Robot: An International Journal

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“…In (Wei et al, 2001) during simulation of kinematic calibration of 6-PSS parallel manipulator, indirect method by photoelectric length gauge with a ball is used for pose measuring. Chai et al (2002) proposed using an external laser measuring device to determine the actual accuracy of a Gough-Stewart platform. Daney (2003) presents the modeling and a unified scheme to identify the kinematic parameters of the last platform.…”

Section: Approach With Adapted Devices For Measurementmentioning

confidence: 99%

Calibration of Parallel Manipulators and their Application to Machine Tools. A State of the Art Survey

Hernández-Martínez

López-Cajún

Jáuregui-Correa³

2010

IIT

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Some of the main investigations on calibration methods of parallel mechanisms are briefly discussed in this work. Initially, the identification of errors in these structures applied to machine tools is presented, later the kinematics and the concept of parallel mechanisms calibration is introduced. Additionally, the main characteristics of the existing methods of calibration are discussed, such as the parametrical approaches, the calibration methods with internal/external measuring devices, innovative calibration methods and works that provide assistance to this aim.Keywords: Parallel mechanisms, calibration, machine tools, inverse kinematics, forward kinematics. Resumen

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“…Several measuring systems have been used to determine the pose of movable rigid bodies often by means of expensive measurement devices such as laser tracking systems, 9 vision-based measure devices, 22,23 or redundant systems. Several measuring systems have been used to determine the pose of movable rigid bodies often by means of expensive measurement devices such as laser tracking systems, 9 vision-based measure devices, 22,23 or redundant systems.…”

Section: Introductionmentioning

confidence: 99%

Design optimization of a cable-based parallel tracking system by using evolutionary algorithms

2014

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2015). Design optimization of a cablebased parallel tracking system by using evolutionary algorithms. Robotica, 33, pp 599-610 SUMMARYIn this paper, an optimization design of a 6 DOF parallel measuring system is analyzed. First, a closed form direct kinematics formulation based on Cayley-Menger determinants is considered in the objective function, in order to measure the manipulator singularities, then an estimation of distribution algorithm is proposed to solve the optimization problem. It is shown that the evolutionary algorithm can find close to optimal solutions for minimum pose error estimation. Additionally, these global optimizers significantly reduce the computational burden in comparison with exhaustive search and other global optimization techniques. The sensitivity of the pose error estimation in the prescribed robots' workspace is analyzed and used to guide a designer in choosing the best structural configuration. Numerical examples are discussed to show the feasibility of the proposed optimization methodology.

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A practical calibration process using partial information for a commercial Stewart platform

Cited by 15 publications

References 12 publications

Kinematic characterisation of hexapods for industry

Kinematic characterisation of hexapods for industry

Calibration of Parallel Manipulators and their Application to Machine Tools. A State of the Art Survey

Design optimization of a cable-based parallel tracking system by using evolutionary algorithms

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