Conference publications

Abstracts

XXII conference

Calibration аlgorithm for tеhe laser tracker system

Kobets S., Nguyen T.T.¹, Amthor A.¹, Ament C.¹

Russia, Moscow, MPEI, Department of Applied Mathematics and Computer Science, kobetsss@gmail.com

¹Germany, Ilmenau, Ilmenau University of Technology, Systems Analysis Group, tran-trung.nguyen@tu-ilmenau.de

1 pp. (accepted)

While working with non-contact geometric measuring devices it can be crucial to have a really high level of accuracy. And this is when optical methods come into play. Inductive and capacitive methods can only cover short distances; methods based on measurement of the propagation time or ultrasound are relatively inaccurate. Length measurements done in vast volumes of space with a help of an interferometer allow us to raise accuracy rate up to nanometers and can serve as the basis for controlling the position of the kinematics.

Lasertracker – is a measuring system that can accurately non-contact determine the position of a point in a three-dimensional space using a retroreflector by the means of two angles and a length. Lasertracker consists of the interferometer (length measurements) and galvanometer scanner (angles measurements). Calculation of the position in three dimensions can be done using the method of triangulation. The accuracy of this method is limiteуd by the angular sensor scanners. Another measurement method is based on the principle of trilateration. Position in space can be determined using only the measurements of lengths using lasertracker. This method is used for multi laser tracking system (MLTS). In order to apply the trilateration method, it is necessary to know the relative position of each lasertracker (which is fixed inside the working space) in the given coordinate system.

This paper presents a calibration method to identify the position as well as system parameters of the multi lasertracking system, which is able to track the movement of a retroreflector. A three-dimensional coordinate of a target position is measured using laser tracking interferometer system based on laser trilateration. By applying the principle of triangulation, four laser interferometers are used to measure the relative optical path of the retroreflector, which produce redundancy in the measurement. Based on this redundancy the parameter of the measurement system can be self-calibrated without reference measurement system. That means that this calibration method calculates the positions of lasertrackers along with the position of the target using just measured distances of four lasertracking interferometers.

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