• Proceedings of the Korean Society of Precision Engineering Conference
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• 2000.11a
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• pp.188-192
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• 2000

An analysjs model for calculation the motion accuarcy of double sides hydrostatic table is proposed in thn paper. For the analysis of motion accuracy, profiles of each rails are assumed as periodic function, and represented using Fourier coefficients. Variahon of bearing clearance is represented as the vanation of linear, angular displacement of table and profiles of rails. Motion accuracy is calculated in the basis of finite element analysis on the pressure dutributmn of table. In order to improve calculating time in the analysis of motion accuracy, The proposed modeling method converts double sides table to single side table equivalently Results by the proposed method 1s compared with directly caculated results mdyhcally, and also compared wlth experimental results. From the theoretical and experimental analysis, it is confirmed that the proposed modeling mothod is very effective to analyze the motion accuracy of dauble sides hydrostatic table.

• Journal of the Korean Society for Precision Engineering
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• v.14 no.12
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• pp.114-120
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• 1997

For compensating the error motion of hydrostatic tables, we have introduced a way that the clearance of table is controlled corresponding to the amount of eror with the actively controlled variable capillary, named as ACC. In previous paper, through the basic test, it was confirmed that by the use of ACC, the error motion within 2.7$\mu$ m of a hydrostatic table could be compensated with the resolution of 27nm, 1/100 contollable range, and with the frequency bandwidth of 5.5Hz, structurally. In this paper, we performed practical compensation of the linear and angular motion error of hydrostatic table using ACC. For improving the compensated motion accuracy, iterative control method is put into the control system. The experimental results show that by the simultaneous compensation of error, the linear and angular motion error are improved upto 0.25$\mu$ m and 0.4arcsec, which are about 1/10 and 1/3 of the non-compensated motion errors respectively.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 1997.10a
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• pp.380-384
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• 1997

For improving the motion accuracy of hydrostatic table, corrective machining algorithm is proposed in this paper. The algorithm consists of three main processes. Reverse analysis is performed firstly to estimate rail profile from measured linear and angular motion error, in the algorithm. For the next step, correctwe machining information is decided as referring to the estimating rail profile. Finally, motion errors on correctively machined rail are analized by using motion error analysls method proposed in the previous paper. These processes can be rtcrated if the analized motion errors are worse than target accuracy. In order to verify the validity of the algorithm theoretically, motion errors by the estimated rail after corrective machining are compared with motion errors by true rail assumed as the measured value. Estimated motion errors show good agreement with assumed values, and it is confirmed that the algorithm IS effective to acquire the corrective machming information to improve the accuracy of hydrostatic table.

• Journal of the Korean Society for Precision Engineering
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• v.21 no.6
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• pp.139-144
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• 2004

In order to discuss the availability of hydrostatic guideways driven by the coreless linear motor to ultra precision machine tools, a prototype of guideway is designed and tested in this research. A coreless linear DC motor with the continuous force of 156 N and a laser scale with the resolution of 0.01 ${\mu}{\textrm}{m}$ are used as the feeding system. The experiments are performed on the static stuffiness, motion accuracy, positioning accuracy, microstep response and variation of velocity. The guideway has the infinite axial stillness within 50 N of applied load, and by the motion error compensation method using the Active Controlled Capillary, 0.08 ${\mu}{\textrm}{m}$ of linear motion error and 0.1 arcsec of angular motion error are acquired. The guideway also has 0.21 ${\mu}{\textrm}{m}$ of positioning error and 0.09 ${\mu}{\textrm}{m}$ of repeatability, and it shows the stable response against the 0.01 ${\mu}{\textrm}{m}$ resolution step command. The velocity variation of feeding system is less than 0.6 %. From these results, it is confirmed that the hydrostatic guideway driven by the coreless linear motor is very useful fur the ultra precision machine tools.

• Journal of the Korean Society for Precision Engineering
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• v.22 no.6 s.171
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• pp.76-82
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• 2005

In this paper, the pole placement controller based on the Robust Internal-loop Compensator (RIC) structure, which has inherent structural equivalence to disturbance observer, is proposed to control a linear positioning system. This controller has the advantage to easily select controller gains by using pole placement without loss of that of original RIC structure. The principal is to construct the pole placement controller for a nominal internal model instead of unknown real plant. Using linear motion experiment showed the effectiveness of the proposed controller.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 1996.11a
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• pp.1073-1077
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• 1996

This paper presents a recoil and counter recoil(R&CR) motion measurement method using linear variable differential transformers(LVDT). The output of a LVDT is obtained from the differential voltage of the 2nd transformers. As a sensor core is attached at the motion body, the output is directly proportional to the core motion. Displacement, velocity and acceleration are measure from the core length. With a comparison between the measurement result and the known value which is obtained by the precision steel tape, the accuracy and the usefulness of the proposed scheme is validated.

• 제어로봇시스템학회:학술대회논문집
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• 1993.10b
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• pp.230-233
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• 1993

This paper described a relationship between motion speed and working accuracy of industrial articulated robot arms. Working accuracy of the robot arm deteriorates at high speed operation caused by a nonlinear transformation of the kinematics and the time delay of the robot arm dynamic. The deterioration of the following trajectory was expressed as a linear function of the squares of the robot arm motion speed, depending upon a posture of the robot arm and division interval of the objective trajectory.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2004.05a
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• pp.326-331
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• 2004

The linear motion (LM) guide using ball bearing has many advantages compared with conventional sliding guides. Therefore, LM guide using ball bearing has been used widely to increase the accuracy of the position of a system. This research investigates dynamic characteristics of LM guide through mainly linear analysis. Linear analysis is accomplished by Lagrange equation and finite element method. And another trial that is nonlinear analysis about one mode of LM guide(bouncing mode) from Hertzian contact theory is accomplished in the latter half of this research. Through nonlinear analysis we could observe the softening characteristic due to the Hertzian contact nonlinearity.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2003.06a
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• pp.343-346
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• 2003

In order to discuss the availability of the hydrostatic guideway driven by the coreless linear motor to ultra precision machine tools, a prototype of guideway is designed and tested in this research. A coreless linear DC motor with the continuous force of 156 N and a laser scale with the resulution of 10 nm are used as the feeding system. The experiments are performed on the static stiffness. motion accuracy, positioning accuracy. microstep response and variation of velocity. The guideway has the infinite axial stiffness within 50 N of applied load, and has 0.08 ${\mu}{\textrm}{m}$ of linear motion error and 0.1 arcsec of angular motion error. It also has 0.21 ${\mu}{\textrm}{m}$ of positioning error and 0.09 ${\mu}{\textrm}{m}$ of repeatability, and it shows the stable response against the 10 nm resolution step command. The velocity variation of feeding system is less than 5%. From these results, it is confirmed that the hydrostatic guideway driven by the coreless linear motor is very useful for the ultra precision machine tools.

• Proceedings of the Korean Society of Machine Tool Engineers Conference
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• 2003.10a
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• pp.36-40
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• 2003

In order to discuss the availability of aerostatic guideways driven by the coreless linear motor to ultra precision machine tools, a prototype of guideway is designed and tested in this research. A coreless linear DC motor with the continuous force of 156N and a laser scale with the resolution of $0.01\mu\textrm{m}$ are used as the feeding system. The experiments are performed on the static stiffness, motion accuracy, positioning accuracy, microstep response and variation of velocity. The guideway also has $0.21\mu\textrm{m}$ of positioning error and $0.09\mu\textrm{m}$ of repeatability, and it shows the stable response against the $0.01\mu\textrm{m}$ resolution step command. The velocity variation of feeding system is less than 0.6%. From these results, it is confirmed that the aerostatic guideway driven by the coreless linear motion is very useful for the ultra precision machine tools.