Laser Tracker

Keywords Laser tracker, volumetric verification, geometrical errors, regression functions, kinematic model. 

Abstract. This paper aims to present different methods of volumetric verification in long range machine toll with lineal and rotary axes using a commercial laser tracker as measurement system. 

This paper presents a high precision volumetric model based on a laser tracker (LT) as measurement system, whereby error compensation is performed in a long range MT with two linear axes and a rotation axis. The paper thus presents a study of the adequacy of different nonlinear optimization methods, the regression functions to be used depending on the type of axis and the usable space available. 

Fig. 1 Operation scheme of volumetric verification using laser tracker as measurement system...

Where Pi represents the measured point coordinates of the machine tool, measured using a laser tracker, and f(x, y, z) the machine tool point coordinates Pi obtained from the kinematic model of the machine (Fig 1). 

S. Aguado, D. Samper, J. Santolaria, J. J. Aguilar. Identification strategy of error parameter in volumetric error compensation of machine tool based on laser tracker measurements. International Journal Machine Tools Manufacture. 2012, 53, 160-169. 

Laser Tracker error modeling and kinematic calibration strategy... 

Keywords Laser Tracker, kinematic calibration, synthetic data. 

Abstract. Calibration of Laser Tracker systems is based most times in the determination of its geometrical errors. Some standards as the ASME B89.4.19 [1] and the VDI 2617-10 [2] describe different tests to calculate the geometric misalignments that cause systematic errors in Laser Tracker measurements. 

These errors are caused not only because of geometrical misalignments and other sources of error must also be taken in count. In this work we want to state the errors in a kinematic form. Errors will be split in two different components, geometric and kinematic errors. The first ones depend on the offsets, tilts and eccentricity of the mechanical and optical components of the system. Kinematic errors are different for every position of the Laser tracker, so they will be formulated as functions of three system variables distance (R), vertical angle (V) and horizontal angle (H) usually called d, (p and 9. 

The goal of this work is to set up an evaluation procedure to determine geometric and kinematic errors of Laser Trackers. 

Laser Tracker with beam source in the rotating head. This model is typical of API and FARO and determination of their geometric errors has been systematized by Muralikrishnan et al. [3] and Hughes et al. [4]. According to the proposed model, calibration corrections are based on 15 parameters, each representing the influence of a particular geometric error in the overall error of the equipment ... 

Laser Tracker with beam source column. LT model used by Leica and whose geometric error model was set by Loser et al. (1999) [5]. Geometric errors are similar to those from the previous model but with the particularity that the laser beam that emerges from the column in the vertical direction LT, is directed to the reflector by a mirror whose center of rotation coincides with the nominal theoretical intersection of the azimuth and tilt axes. The errors described are ... 

Laser Tracker modeling errors with beam source in the head (Model 1)... 

It has been shown the beginning of a process which will lead to with the development of a simple procedure for the calibration of laser tracker systems. The work done so far include the tests on SMR and planning of them with Active Target. Also the definition of LT models to study and geometric errors is at an advanced stage along with the definition of an automatic generator of synthetic data with simulated errors. 

VDI/VDE 2011 Accuracy of Coordinate Measuring Machines Characteristics and their Checking Acceptance and Reverification Tests of Laser Trackers (Diisseldorf Verein Deutscher Ingenieure) VDIADE 2617 part 10. 

B. Muralikrishnan, D. Sawyer, C. Blackburn, S. Philips, B. Borchardt, W. T. Estler 2009 AMSE B89.4.19 performance evaluation tests and geometric misalignments in laser trackers J. Res. Natl Inst. Stand. Technol. pp. 114 21-35... 

B. Hughes, A. Forbes, A. Lewis, W. Sun, D. Veal, K. Nasr, Laser tracker error determination using a network measurement. Measurement Science and Technology, vol. 22, no. 4 (2011) pp. 045103. 

R. Loser, S. Kyle, Alignment and field check procedures for the Leica Laser Tracker LTD 500, Boeing Large Scale Optical Metrology Seminar (1999). 

T. Takatsuji, M. Goto, S. Osawa, R. Yin, T. Kurosawa, Whole-viewing-angle cat s-eye retroreflector as a target of laser trackers. Meas. Sci. Technol. 10 (1999) pp. 87-90. 

The necessary data are usually obtained by means of external devices such as vision devices [3], the laser tracker [4] or the coordinate measuring machine. Then, the following step is to identify the kinematic parameters that provide the optimum value of an objective function. This function can be formulated in terms of a linear minimum-square. 

J. Santolaria, A C. Majarena, D. Samper, A. Brau, J. Velazquez, Articulated Arm Coordinate Measuring Machine Calibration by Laser Tracker Multilateration, ID 681853, (2014) 1-11. 

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