• The Transactions of the Korean Institute of Electrical Engineers D
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• v.53 no.10
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• pp.678-689
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• 2004

The major concern of networked control system is network uncertainties such as time delay and data loss. Because these uncertainties may degrade the performance of networked control system and destabilize the entire system. Therefore, the performance and the stability variation of networked control system due to network uncertainties must be considered first in designing networked control system. In particular, the stability analysis of networked control system is most important issue since time delay and data loss can make the overall systems unstable. In this paper, we present a new stability analysis method of networked control system with time delay and data loss, which is impossible in previous works. The proposed method can determine maximum time delay and allowable transmission rate that preserve stability performance of networked control system. The results of the simulation validate effectiveness of our stability analysis method.

• Proceedings of the KIEE Conference
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• 2005.10b
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• pp.23-25
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• 2005

This paper is devoted to the passivity based control in bilateral teleoperation for varying time delay. Toimprove the stability and task performance, master and slave in bilateral teleoperation must be coupled via the network through which the force and velocity are communicated. However, time delay existing in the transmission channel is a long standing impediment to bilateral control and can destabilize the system, even if the system is stable without time delay, In this paper, we investigate how the varying time delay affects the advanced teleoperation stability and results in an out-of-control status. A new approach based on passivity control has been bilaterally designed for both the master and slave sites and the simulation result will verify that our approach is better and effective for passive bilateral teleoperation.

• Proceedings of the KIEE Conference
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• 2007.04a
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• pp.340-342
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• 2007

When a system is teleoperated in the indoor environment through the wireless LAN, the communication time delay that is due to the inherent characteristic and surrounding environment is random and unbounded. The time delay has a significant effect on the stability and performance of the teleoperating system. In this paper, we present the method that is the image compression, measuring time delay and switching control-mode corresponding to time delay automatically, to improve stability and performance, and the simple experiment is conducted to demonstrate the feasibility

• Journal of Institute of Control, Robotics and Systems
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• v.9 no.8
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• pp.632-639
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• 2003

This paper proposes a simple compensation scheme for the time delay caused by measurement, calculation and selection of voltage vector in Direct Torque Control (DTC) of an induction motor. In general scheme, it is difficult to know the exact delay time, furthermore the delay time can be varied by program routines for calculation and processing of measured data. In this proposed scheme, by applying voltage vector at the beginning of next sampling period, a fixed delay time is achieved and its compensation becomes much simpler. Furthermore, with the simple compensation algorithm, an improved performance can be achieved by shortening sampling period. Experimental results prove the feasibility of the proposed scheme in induction motor control.

• Proceedings of the KIEE Conference
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• 2003.11c
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• pp.441-444
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• 2003

Network uncertainties such as data loss and time delay can vary the stability property of networked control system. Therefore, these uncertainties must be considered first in designing networked control system. In this paper, we present a new stability analysis method of networked control system with data loss and time delay. The proposed method can determine maximum allowable time delay and minimum allowable transmission rate that preserves stability performance of networked control system. The results of the simulation validate effectiveness of our stability analysis method.

• Journal of the Korea Society of Computer and Information
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• v.13 no.1
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• pp.175-183
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• 2008

QoS-support technology in networks is based on measuring QoS metrics which reflect a magnitude of stability and performance. The one-way delay measurement of the QoS metrics especially requires a guarantee of clock synchronization between end-to-end hosts. However, the hosts in networks have a relative or absolute difference in clock time by reason of clock offsets. flock skews and clock adjustments. In this paper, we present a theorem, methods and simulation results of one-way delay and clock offset estimations between end-to-end hosts. The proposed theorem is a relationship between one-way delay, one-way delay variation and round-trip time And we show that the estimation error is mathematically smaller than a quarter of round-trip time.

• Transactions on Control, Automation and Systems Engineering
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• v.1 no.2
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• pp.128-133
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• 1999

This paper presents a new delay-dependent robust stabilization condition for uncertain time-delay systems. An algorithm involving convex optimization is proposed to compute a suboptimal upper bound of the delay such that the system can be stabilized by the controller for all admissible uncertainties. It is illustrated by numerical examples that the proposed delay-dependent controller can be less conservative than previous results. It is also shown that the proposed delay-dependent controller can even capture the delay-independent stability of the system, which is not possible with existing delay-dependent results.

• Journal of the Korean Institute of Telematics and Electronics
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• v.15 no.5
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• pp.13-18
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• 1978

A delay switching PLL (DSPLL) is proposed for improvement of the frequency acquisition Performance (pull-in range) while keeping a narrow bandwidth LPF. It has, between the phase detector and the LPF, just a simple RC delay circuit, a switch and another phase detector controlling the switching time. For the common second order PLL, the pull-in capability of the DSPLL is analyzed approximately, without considering additive white noise effect, and verified experimentally. It is shown that the delay switching extends the pull-in range significantly, as much as a half of lock-range. At the phase tracking mode, the delay switching does not function, to make the DSPLL be a normal PLL.

• 전기의세계
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• v.28 no.3
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• pp.37-50
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• 1979

The time optimal control of dynamic systems with time delay is studied with emphasis on the practical realization of controllers. An extensive survey on various methods of control is included and a result for a time optimal regulator with signle delay in control is presented and simulated on a digital computer.

• 제어로봇시스템학회:학술대회논문집
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• 2002.10a
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• pp.59.5-59
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• 2002

In this paper, we present a robust controller design method that can not only deal with the constant time delay plant but also an uncertain time delay one. For a constant time delay plant. The proposed DTC can independently adjust the set response and the disturbance response without any stability constraint. And in the uncertain time delay case, one can process the control design step with uncertainty norm bound. To verify real effectiveness, theoretical analysis and simulation results are given.