Thermal and Geometric Error Compensation Approach for an Optical Linear Encoder.

Donatas Gurauskis,Albinas Kasparaitis,Artūras Kilikevičius

doi:10.3390/s21020360

Donatas Gurauskis, Albinas Kasparaitis + Show 1 more

Open Access

https://doi.org/10.3390/s21020360

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Abstract

Linear displacement measuring systems, like optical encoders, are widely used in various precise positioning applications to form a full closed-loop control system. Thus, the performance of the machine and the quality of its technological process are highly dependent on the accuracy of the linear encoder used. Thermoelastic deformation caused by a various thermal sources and the changing ambient temperature are important factors that introduce errors in an encoder reading. This work presents an experimental realization of the real-time geometric and thermal error compensation of the optical linear encoder. The implemented compensation model is based on the approximation of the tested encoder error by a simple parametric function and calculation of a linear nature error component according to an ambient temperature variation. The calculation of a two-dimensional compensation function and the real-time correction of the investigated linear encoder position readings are realized by using a field programmable gate array (FPGA) computing platform. The results of the performed experimental research verified that the final positioning error could be reduced up to 98%.

Highlights

The implemented compensation model is based on the approximation of the tested encoder error by a simple parametric function and calculation of a linear nature error component according to an ambient temperature variation
Encoder mounting couldapproximately be the same amount of heat all the time, it is stated that along the linear encoder existed a steady source of the linear position measurement error, because of misalignment or deformations during fixation, lack of support stiffness, inaccurate guideway carriage, andinduced so on. ther thermal gradient
The approach of a thermal and geometric error compensation for a linear encoder is introduced in this article

Summary

Introduction

The vast majority of industrial and scientific applications use optical encoders for a position measurement and closed-loop position control, for example, machine tools [1,2,3,4,5], tracking systems [6,7,8], industrial robots [9,10,11,12,13], positioning stages [14,15,16,17], and so on All these technological machines work under various environment conditions such as temperature, humidity, mechanical vibration, etc. The majority of this research analyzes only the machine tool structure, considering that the used measurement system is not the source of the error by itself [29]

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