Modeling of Absolute Distance Meter Shift Inside a Laser Tracker


In the measurement of machine tool and robot geometric errors, one of the most extensively used instruments is the Laser Tracker (LT). Errors in the LT measurements will decrease the effectiveness of the error modeling and compensation methods that utilize these measurements. When the LT's Absolute Distance Meter (ADM) is used without frequent referencing to a home position, large and long-term shifts occur. The ADM shift directly introduces errors in the radial component of every measurement in spherical coordinates, which will result in measurement errors in the Cartesian coordinates. Although the ADM shift is addressed in newer LT designs using internal referencing hardware, this paper presents a pragmatic and efficient software solution to ADM shift for LTs in which the internal referencing hardware is not embedded. The LT was measured for 22 hr in a temperature-constant room to examine the ADM shift effects on measurements. An ADM shift model was then proposed by assuming that the ADM shift equally affects radial components of all measurements wherever the target is, as long as it is within the measurement range. Another experiment was then performed to test the validity of the proposed model. After the model was identified and errors were corrected, the maximum temporal variation in the radial distance measurement is reduced by 80-86%.

Meeting Name

ASME 2017 12th International Manufacturing Science and Engineering Conference, MSEC 2017 (2017: Jun. 4-8, Los Angeles, CA)


Mechanical and Aerospace Engineering

Research Center/Lab(s)

Intelligent Systems Center


The authors gratefully acknowledge the financial support for this work provided by the National Science Foundation (NSF, Grant No.CMMI-1335340) and the Center for Aerospace Manufacturing Technologies at the Missouri University of Science and Technology.

Keywords and Phrases

Error compensation; Errors; Hardware; Machine tools; Manufacture; Absolute distance; Cartesian coordinate; Compensation method; Measurement range; Software solution; Spherical coordinates; Temperature constant; Temporal variation; Instrument errors

International Standard Book Number (ISBN)


Document Type

Article - Conference proceedings

Document Version


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© 2017 American Society of Mechanical Engineers (ASME), All rights reserved.

Publication Date

01 Jun 2017