• Proceedings of the KSME Conference
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• 2001.06b
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• pp.93-98
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• 2001

This paper studies on the design of an ILQ(Inverse Linear Quadratic optimal control) looper control system for hot strip mills. The looper which is placed between each stand plays an important role in controlling strip width by regulating strip tension variation generated from the velocity difference of main work rolls. The mathematical model for looper is firstly obtained by Taylor's linearization of nonlinear differential equations, where it is given as a linear and time invariant state-space equation. Secondly, a looper servo controller is designed by ILQ control algorithm, which is an inverse problem of LQ(Linear Quadratic optimal control) control. By tunning control gain arbitration parameters and time constants, it is shown that the ILQ looper servo controller has the performance that makes well to follow desired trajectories of both strip tension and looper angle.

• Journal of the Korean Society of Manufacturing Technology Engineers
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• v.18 no.5
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• pp.462-468
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• 2009

In this study, a workpiece-chucking device that generates a chucking force from a shape memory alloy is introduced. This paper first presents train procedure to transform a commercial one-way shape memory alloy into a two-way shape memory alloy, which makes unclamping mechanism of the chucking device simpler than that using the one-way shape memory alloy Second, it describes a conceptual design of the workpiece-chucking device using the two-way type shape memory alloy. Third, it presents a prototype and its chucking characteristics, such as time-response of clamping/unclamping operations and a relationship between temperatures and chucking forces. Finally, it describes a mill-machining test conducted with the prototype. The results confirm that the proposed workpiece-chucking device is feasible for micro machine-tools.

• Transactions of the Korean Society of Machine Tool Engineers
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• v.17 no.2
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• pp.121-127
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• 2008

Micro end-milling has been becoming an important machining process to manufacture a number of small products such as micro-devices, bio-chips, micro-patterns and so on. Despite the importance of micro end-milling, many related researches have given grand efforts to micro end-milling phenomenon, for example, micro end-milling mechanism, cutting force modeling and machinability. This paper strongly concerned actual problem, micro tool deflection, which causes excessive machining errors on the workpiece. To solve this problem, machining error prediction method was proposed through a series of test micro cutting and analysis of their SEM images. An iterative algorithm was applied in order to obtain corrected tool path which allows reducing machining errors in spite of tool deflection. Experiments are carried out to validate the proposed approaches. In result, remarkable error reduction could be obtained.

• Advances in concrete construction
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• v.4 no.4
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• pp.263-281
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• 2016

Concrete continues to be the most consumed construction material in the world, only next to water. Due to rapid increase in construction activities, Construction and Demolition (C&D) waste constitutes a major portion of total solid waste production in the world. It is important to assess the amount of C&D waste being generated and analyse the practices needed to handle this waste from the point of waste utilization, management and disposal addressing the sustainability aspects. The depleting natural resources in the current scenario warrants research to examine viable alternative means, modes and methods for sustainable construction. This study reports processing Recycled Coarse Aggregates (RCA) using a rod mill, for the first time. Parameters such as amount of C&D waste for processing, nature of charge and duration of processing time have been optimized for obtaining good quality RCA. Performance of RCA based concrete and performance enhancement techniques of 50% RCA based concrete are discussed in this paper.

• Journal of Korean Institute of Industrial Engineers
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• v.21 no.2
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• pp.217-237
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• 1995

One of the most distinguished advantages of five-axis machining is that complex free surfaces(such as impeller) can be machined by one setup. Five-axis CNC machine, however, is very expensive so that its usage is restricted to a few large companies. As an economical approach to five-axis machining, this paper presents a method for machining the five-axis free surfaces(using ball-end mill) on a three-axis CNC machine with an index table. The method developed consists of: a) determining the minimum number of part setups and their interference-free and collision-free potential machining area, b) calculating actual machining area for each setup, and c) generating 3-axis cutter path for each part setup. The method has been successfully tested via computer simulations for several complex surfaces including impeller.

• KIEE International Transaction on Electrical Machinery and Energy Conversion Systems
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• v.3B no.3
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• pp.133-138
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• 2003

In this paper, a BLDC motor and its controller are developed for treadmill application. Motor size and structure are restricted in the design stage due to the limited and enclosed space of the treadmill. The shape of the rotor magnet is analyzed using FEM with restricted design conditions. Manufacturing, cost and performance are also considered. A biomechanical analysis of human locomotion with the change of velocity is considered in the design of the controller. For stable operation of the treadmill, current and temperature are to be detected by the DSP controller. The prototype BLDCM and its controller are tested to verify its performances.

• Proceedings of the KIEE Conference
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• 1993.07b
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• pp.889-891
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• 1993

In order to perform the group control of motor drive systems in such as steel process line, high performance communication system is indispensible. In this paper, we introduce newly developed communication system which is suitable for these group control application. Using HDLC protocol, this system can transfer data to a long distance(up to 1km) at high speed(1Mbps) with reliability and efficiency. The performance of this communication system was proven through the application to the group control of DAEKYOUNG Bar Mill Line.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 1999.11a
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• pp.323-326
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• 1999

In this paper, a windmill type ultrasonic motor operated by single-Phase AC electric field was fabricated, and then torque characteristics were investigated. A metal-ceramic composite component was used as the stator\`s vibrator to generate ultrasonic vibrations. The windmill type ultrasonic motors has only three components; a stator element with two wind-mill shape slotted metal endcaps, a rotor and a bearing. In this parer we measured torque, when stator\`s slot was changed Iron 4, 6, 8. Brass metal was pressed with umbrella-type using metal molt then slot of 3 kind was manufactured. The maximum revolution speed was 388(rpm) in the case of a small ultrasonic motor of 11.35 mm diameter, 8 slot and 1.01 mm thickness. The maximum torque of 0.17 mNm was obtained at a speed of 131 rpm.

• Proceedings of the KIEE Conference
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• 1998.11a
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• pp.189-191
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• 1998

The development of the high- frequency induction-heating for 2700kW power range intend to make localization at forging and rolling mill part by technical innovation. And, the development makes to increase our's competitive power at technique, quality and cost. This paper describes the heart of high-frequency induction-heating technique, switching technique, a few problem in common using as an unsatisfied technique, load adjustment technique, system control, diagnostic system and auto-interface etc.

• Proceedings of the KIEE Conference
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• 2003.11c
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• pp.693-696
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• 2003

Among many servo control systems in steel making plant, AGC system in hot rolling mill is very important to get a accurate strip thickness for good quality. AGC (Auto Gauge Control) system controls the roll gap to maintain the required thickness by using the variation of roll force and the measure of output thickness. In this paper, a simulator of AGC system which unifies both hydraulic servo control system and AGC algorithm is suggested. After proving the concurrence of algorithms between the simulator and real system, main actuator system is added. Instead of usual PI system used in present system, DOB control scheme is applied and shows the effect of disturbance attenuation well.