• 제목/요약/키워드: Thermal Error Compensation

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Design of Thermal Displacement Compensation Sensor for High Reliability Machine Tools (고신뢰 머시닝센터를 위한 열변위 보상 센서 설계기술)

  • Kim, Il-Hae;Jang, Dong-Young;Park, Jeong-Hoon;Park, Sung-Wook;Shim, Poong-Soo
    • Journal of the Korean Society for Precision Engineering
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    • v.28 no.8
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    • pp.886-893
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    • 2011
  • To increase the reliability and positional accuracy of a machine tool, a novel capacitive displacement sensor having a cylindrical shape is presented to measure the axial displacement of a machine tool spindle. Characteristics of the sensor were analyzed by numerical simulation. The sensor was built into a specific machine tool spindle and its performance was experimentally investigated. The accuracy of a thermal error compensation system of a machine tool can be enhanced greatly using proposed sensor.

Development of Online Realtime Positioning Error Compensation System for CNC Machine Tools (CNC 공작기계용 온라인 실시간 위치오차 보정시스템의 개발)

  • Chung, Chae-Il;Kim, Jong-Won;Nam, Weon-Woo;Lee, Sang-Jo
    • Journal of the Korean Society for Precision Engineering
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    • v.16 no.10
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    • pp.45-52
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    • 1999
  • The online realtime positioning error compensation system 'SKY-PACS' is developed to correct geometric errors, thermal errors and tool deflection errors induced by cutting forces on the vertical machining center. 'SKY-PACS' communicates position commands and position compensation signals with the CNC controller at 100Hz, which is CNC control frequency. So the compensation procedure can be applied during axis movement. Using 'SKY-PACS', Maximum 1 axis positioning accuracy was corrected from 5{\mu}m$ to 2{\mu}m$and the squareness error of X-Y table was corrected from 51{\mu}m$/m to below 4{\mu}m$/m. The error compensation under the cutting condition is carried out by ISO10791-7. And the measurement of test-pieces shows that the roundness is corrected rom 8{\mu}m$ to below 5{\mu}m$.

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Thermal Error Measurement and Modeling Techniques for the 5 Degree of Freedom(DOF) Spindle Unit Drifts in CNC Machine Tools (CNC 공작기계 스핀들 유닛의 5자유도 열변형 오차측정 및 모델링 기술)

  • Park, Hui-Jae;Lee, Seok-Won;Gwon, Hyeok-Dong
    • Transactions of the Korean Society of Mechanical Engineers A
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    • v.24 no.5 s.176
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    • pp.1343-1351
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    • 2000
  • Thermally induced errors have been significant factors affecting the machine tool accuracy. In this paper, the spindle thermal error has been focused, where the 5 degree of freedom thermal error components are considered. An effective measurement system has been devised for the 5 DOF thermal errors, consisting of gap sensors and thermocouples around the micro-computer interfaced environment. Several thermal error modeling techniques are also implemented for the thermal error prediction: multiple linear regression, neural network and system identification methods, etc. The performance of the thermal error modeling techniques is evaluated and compared, giving the system identification method as the optimum model having the least deviation. The developed system for the thermal error measurement and modeling was practically applied to a CNC machining center, and the spindle thermal errors were effectively compensated around the micro computer-machine tool interfaced networks. The machine tool accuracy was improved about 4-5 times typically.

Disturbance Observer-based Current Measurement Offset Error Compensation in Vector-controlled SPMSM Drives (표면 부착형 동기 전동기 벡터 제어에서의 외란 관측기 기반 전류 측정 오프셋 오차 보상 방법)

  • Lee, Sang-Min;Lee, Kibok
    • The Transactions of the Korean Institute of Power Electronics
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    • v.27 no.5
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    • pp.402-409
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    • 2022
  • In vector-controlled drive systems, the current measurement offset error causes unwanted torque ripple, resulting in speed and torque control performance degradation. The current measurement offset error is caused by various factors, including thermal drift. This study proposes a simple DC offset error compensation method for a surface permanent magnet motor based on a disturbance observer. The disturbance observer is designed in the stationary reference frame. The proposed method uses only the measured current and machine parameters without additional hardware. The effect of parameter variations is analyzed, and the performance of the current measurement offset error compensation method is validated using simulation and experimental results.

Real-time Estimation and Compensation of Thermal Error for the Machine Origin of Machine Tools (공작기계 원점 열변형오차의 실시간 규명 및 보상제어)

  • 안중용
    • Proceedings of the Korean Society of Machine Tool Engineers Conference
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    • 1998.03a
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    • pp.148-153
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    • 1998
  • In order to control thermal deformation of machine origin of machine tools due to internal and external heat sources, the real-time compensation system has been developed. First, GMDH models were constructed to estimate thermal deformation of machine origin for a vertical machining center through the measurement of deformation data and temperature data of specific points on the machine tool. Thermocouples and gap sensors are used respectively for measurement. These models are nonlinear equations with high-order polynomials and implemented in a multilayered perceptron type network structure. Secondly, work origin shift method were developed by implementing digital I/O interface board between CNC controller and IBM-PC. The work origin shift method is to shift the work origin by the compensation amounts which is calculated by pre-established GMDH model. From the experimental result, thermal deformation of machine origin was reduced to below $\pm$5${\mu}{\textrm}{m}$.

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Form Error Compensation of Aspheric lens considering Thermal Deformation on Glass Molding Press ( I ) (Glass Lens 가압성형의 열 변형에 의한 비구면 Lens 형상보정 ( I ))

  • Lee, Hak-Suk;Lee, Dong-Kil;Park, Jong-Rak;Kim, Hye-Jung;Kim, Jung-Ho
    • Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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    • 2008.11a
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    • pp.354-354
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    • 2008
  • Recently, due to the tremendous growth of media technology, demands of the aspheric glass lens which is a high-performance and miniaturized is gradually increasing. Generally, the aspheric glass lens is manufactured by GMP(Grass Molding Press) method using WC(tungsten carbide) mold core. In this study, the thermal deformation which occurs in the cooling step of GMP was considered, and it was compensated the form of mold core. The lens which was molded by compensated mold core was satisfied that can be applied to the actual specifications.

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Development of Error Compensation System and On the Machine Measurement System for Ultra-Precision Machine (초정밀가공기용 오차보상시스템 및 기상측정장치 개발)

  • 이대희;나혁민;오창진;김호상;민흥기;김민기;임경진;김태형
    • Proceedings of the Korean Society of Precision Engineering Conference
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    • 2003.06a
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    • pp.599-603
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    • 2003
  • This paper present an error compensation system and On-Machine Measurement(OMM) system for improving the machining accuracy of ultra-precision lathe. The Fast-Tool-Servo(FTS) driven by a piezoelectric actuator is applied for error compensation system. The controller is implemented on the 32bit DSP for feedback control of piezoelectric actuator. The control system is designed to compensates three kinds of machining errors such as the straightness error of X-axis slide, the thermal growth error of the spindle. and the squareness between spindle and X-axis slide. OMM is preposed to measure the finished profile of workpiece on the machine-tool using capacitive sensor with highly accurate ruby tip probe guided by air bearing. The data acquisition system is linked to the CNC controller to get the position of each axis in real-time. Through the experiments, it is founded that the thermal growth of spindle and tile squareness error between spindle and X-axis slide influenced to machining error more than straightness error of X-axis slide in small travel length. These errors were simulated as a sinusoidal signal which has very low frequency and the FTS could compensate the signal less than 30 m. The implemented OMM system has been tested by measuring flat surface of 50 mm diameter and shows measurement error less than 400 mm

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