Laser tracker error determination using a network measurement

Hughes, Ben; Forbes, Alistair; Lewis, Andrew; Sun, Wenjuan; Veal, Dan; Nasr, Karim M.

doi:10.1088/0957-0233/22/4/045103

Cited by 72 publications

(55 citation statements)

References 10 publications

(13 reference statements)

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“…A novel network-based laser tracker testing/calibration methodology, demonstrated by NPL [8] has received great interest from the laser tracker manufacturers and industrial community. The method is approximately eight times faster than existing methods in the published standard (ASME B89.…”

Section: Npl Network Based Calibration Methodologymentioning

confidence: 99%

ASME B89.4.19 standard for laser tracker verification – experiences and optimisations

Nasr

Forbes

Hughes

et al. 2012

Int. J. Metrol. Qual. Eng.

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Abstract. Laser trackers are becoming the tool of choice for large volume dimensional metrology applications such as the measurement of aerospace assemblies, power plant structures, civil engineering structures and terrestrial transportation vehicles. A laser tracker is a portable coordinate measuring system that tracks a moving target reflector and measures the position of the target in spherical coordinates (r, θ, φ). The metrological performance of a laser tracker is influenced by many factors including: compensation for atmospheric effects, thermal expansion of the instrument and its mount, thermal distortion of the workpiece or artefact being measured, the wavelength of the laser radiation, the internal alignment of the gimbal axes and the linearity and alignment of the internal angular measuring scales. The most important of these potential error sources, which fundamentally limit the achievable uncertainty, are the internal mechanical and optical alignments and the quality and alignment of the angular scales. Several national and international standards exist or are in the process of being developed for performance verification of laser trackers. ASME B89.4.19-2006 is one of the established standards used to verify the performance of laser trackers. The main test relies on measuring a known reference length in a variety of configurations and ranges and comparison of the observed error (laser tracker measured length minus reference length) with the specified maximum permissible error (MPE) defined by the manufacturer. The establishment of an ASME B89.4.19 laser tracker verification facility at NPL is introduced. We highlight the importance of tracker verification and discuss the error sources, which contribute to the tracker measurement uncertainty. Some initial results obtained using this new facility are presented.

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Section: Npl Network Based Calibration Methodologymentioning

confidence: 99%

ASME B89.4.19 standard for laser tracker verification – experiences and optimisations

Nasr

Forbes

Hughes

et al. 2012

Int. J. Metrol. Qual. Eng.

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“…The NPL network test [2] involves the measurement of a network of fifteen to eighteen targets from independent tracker positions/rotations in front-face and back-face modes. In-house developed software uses the collected network of data to solve a nonlinear optimisation problem to obtain the correct positions of the tracker, the location of target nests and all the tracker error correction factors including angle encoder errors and geometrical misalignments.…”

Section: The Npl Network Techniquementioning

confidence: 99%

“…The horizontal angle encoder calibration methodologies used were: the National Institute of Standards and Technology (NIST) technique [1], the NPL network technique [2] and the precision angular indexing table technique.…”

Section: Introductionmentioning

confidence: 99%

Determination of Laser Tracker Angle Encoder Errors

Nasr

Hughes

Forbes

et al. 2014

EPJ Web of Conferences

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Abstract. Errors in the angle encoders of a laser tracker may potentially produce large errors in long range coordinate measurements. To determine the azimuth angle encoder errors and verify their values stored in the tracker's internal error map, several methodologies were evaluated, differing in complexity, measurement time and the need for specialised measuring equipment. These methodologies are: an artefact-based technique developed by NIST; a multi-target network technique developed by NPL; and the classical precision angular indexing table technique. It is shown that the three methodologies agree within their respective measurement uncertainties and that the NPL technique has the advantages of a short measurement time and no reliance on specialised measurement equipment or artefacts.

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“…Till today different researchers have focused on some of these one independently [17] or only analysing only an approach [18]. However, developed software allows us to face this problem from a global approach; merging scientific and industrial application in a simulation tool as in other areas is done [19,20].…”

Section: Introductionmentioning

confidence: 99%

Modelling of Computer-Assisted Machine Tool Volumetric Verification Process

Aguado¹,

Velázquez²,

Samper³

2016

Int. j. simul. model.

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Nowadays, the accuracy of machining parts is essential in order to compete in a global market as demanding as machining. Due to the high cost of these machines continuous operation is required, with a reduction of the downtime owing to production readiness, maintenance or breakdowns. Among all the sources of error that affect the accuracy of machining parts, this paper is focused on improving the positioning accuracy of the machine. This requires periodic inspection of the machine tool, which should be included in maintenance operations.Volumetric verification is a novel technique that is being progressively introduced in machine tool maintenance operations, significantly reducing the time required. Unlike other techniques, this is based on non-linear mathematical models and the optimization process increases the influence factors. This modelling provides a re-creation of the whole verification process for all the influence factors; this allows the determination of the best measurement system distribution and the identification of techniques to use to characterize geometric errors. Thus, the verification time required is reduced, unnecessary tests are eliminated, the conditions under which real tests should be carried out are obtained in advance and machine tool accuracy is improved.

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Laser tracker error determination using a network measurement

Cited by 72 publications

References 10 publications

ASME B89.4.19 standard for laser tracker verification – experiences and optimisations

ASME B89.4.19 standard for laser tracker verification – experiences and optimisations

Determination of Laser Tracker Angle Encoder Errors

Modelling of Computer-Assisted Machine Tool Volumetric Verification Process

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