• Journal of Broadcast Engineering
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• v.12 no.1 s.34
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• pp.53-60
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• 2007

A Digital Broadcasting Satellite (DBS) receiver converts digital A/V streams received from a satellite to analog NTSC A/V signals in real-time. Multi-tasking is an efficient way to improve the utilization of the processor core in real-time applications. In this paper, we propose a hybrid approach with a balanced trade-off between hardware kernel and multi-tasking programming to increase a system throughput. First, the schedulability of the critical hard real-time tasks in the DBS receiver is verified by using a simple feasibility test. Then, several soft real-time tasks are thoughtfully programmed to satisfy functional requirements of the system.

• Journal of the Korean Society for Precision Engineering
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• v.31 no.7
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• pp.627-634
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• 2014

Machine tool vibration is well known for reducing machining accuracy. Because vibration response of a linear structure generally depends on its transfer function if the magnitude of excitation were kept constant, this study introduces a RET(Random Excitation Test) based on FRF method to evaluate stiffness of a prototype HDMTL(Heavy-Duty Multi-Tasking Lathe) for large crankshaft of marine engine. Firstly, two force loops of the lathe and corresponding structural loops were identified:1) workpiece - spindle - head stock - main bed, 2) workpiece - tool post - carriage bed. Secondly, compliances of each structural loop were measured respectively using RET with a hydraulic exciter and then converted into stiffness. Finally, the measured stiffness was compared with that obtained previously by FEM analysis. As the result, both measured and computed stiffness were closely in agreement with each other. And the prototype HDMTL has evidently sufficient rigidity above ordinary heavy-duty lathes.

• 제어로봇시스템학회:학술대회논문집
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• 2005.06a
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• pp.621-625
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• 2005

This paper presents a new hybrid serial-parallel robot(HSPR), which has six degrees of freedom driven by ball screw linear actuators and motored joints. This hybrid robot design presents a compromise between high rigidity of fully parallel manipulators and extended workspace of serial manipulators. The hybrid robot has a large, singularity-free workspace and high stiffness. Therefore, the presented kinematic structure of the hybrid robot is particularly suitable for multi-tasking machining processes such as milling, drilling, deburring and grinding. In addition to the machining processes, the hybrid robot can be used for welding, fixturing, material handling and so on. The study on design of the hybrid robot is performed. A kinematic analysis and mechanism description of the hybrid robot with six-controlled degree of freedom is presented. In the virtual design works by DADS, workspace and force analysis are discussed. A numerical model is treated to demonstrate our analysis and to determine the range of permissible extension of the struts. Also, we determine some important design parameters for the hybrid robot.

• Journal of the Korean Society for Precision Engineering
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• v.29 no.2
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• pp.139-146
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• 2012

A multi-tasking machine tool for large scale marine engine crankshafts has been developed together with design technologies for its special devices. Since work pieces, that is, crankshafts to be machined are big and heavy; weight of over 100 tons, length of 10 m long, and diameter of over 3.5 m, several special purpose core devices are necessarily developed such as PTD (Pin Turning Device) for machining eccentric pin parts, face place and steady rest for chucking and resting heavy work pieces. PTD is a unique special purpose device of open-and-close ring typed structure equipped with revolving ring spindle for machining eccentric pins apart from journal. In order to achieve high rigidity of the machine tool, structural design optimization using TMSA (Taguch Method based Sequential Algorithm) has been completed with FEM structural analysis, and a hydrostatic bearing system for the PTD has been developed with theoretical hydrostatic analysis.

• Transactions of the Korean Society of Machine Tool Engineers
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• v.18 no.2
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• pp.162-169
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• 2009

This paper describes a study on dynamic characteristics analysis and dynamic compliance evaluation of a 5-axis multi-tasking machine tool of ram-head type. Structural dynamics analysis and evaluation are necessary to machine tool design and development to secure good machine tool performance against tough and harsh machining conditions. In this study, natural frequencies and corresponding vibration modes of the machine tool structure were analyzed by using both F.E.M. modal analysis and impulse hammer test. Furthermore, dynamic compliance of the machine tool was analyzed by using F.E.M. and also measured by using a hydraulic exciter test. Both the theoretical analysis and experimental test results showed good agreement with each other.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2012.10a
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• pp.311-312
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• 2012

• 제어로봇시스템학회:학술대회논문집
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• 1996.10b
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• pp.1048-1051
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• 1996

In this paper, we present real-time S/W architecture and techniques such as real-time scheduling, synchronization, and etc. for implementation of a real-time control system for driving multi-motors. Simulation shows feasibility of real-time S/W techniques presented here.

• 제어로봇시스템학회:학술대회논문집
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• 1997.10a
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• pp.672-675
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• 1997

This paper proposes a structure of the control system for the step & scan exposure tool. The step & scan exposure tool is used for the manufacturing process of the semiconductor DRAM memory of giga bit. The control system employs the VME bus instead of the conventional ISA bus so that all control signals and data can be managed separately by the 4 VME-PCs for fast and fault-free flow of signals for multi-tasking. A high speed I/O card is equipped for the real-time monitoring and control of the sub module equipment. Then all the subsystems are integrated and aligned for the operation of the step & scan exposure tool with the VME bus and, I/O card.

• Proceedings of the Korea Society for Simulation Conference
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• 2001.10a
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• pp.280-287
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• 2001

There have been some studies about hybrid production system, which integrate push system and pull system. Most of them are based on the simple production system considering one product line. Though there are many studies about hybrid production system, it\`s not practical to implement them for real factory, because most of them did not consider various factors about real factory. On this study we designed hybrid production system considering some factor - one is automatic kanban generation, the other is dispatching rule for Multi-tasking worker, and the last one is the priority of kanban. At last, We give simulation results fur a real company, which produce various cameras in Korea.

• Journal of Institute of Control, Robotics and Systems
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• v.5 no.5
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• pp.622-629
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• 1999

This paper discusses a real time multi-tasking system model and a development environment for an elevator control system. Recently, as the elevator systems become large-scaled and operate with high speed, there are lots of software tasks to be processed with time constraints. Thus, the control systems are designed with distributed control structure and characteristics of typical real time systems. For stuructural design of such real time system, we introduce a multi-tasking model based on a real time operating system model and an software development environment based on virtual protopyping which simulates real system operation in the cross development of a new elevator system with distributed control structure and its system reliability can be verified through numerous field tests.