• Transactions of the Korean Society of Mechanical Engineers A
• /
• v.26 no.8
• /
• pp.1534-1544
• /
• 2002

The TDCSA(Time Delay Control with Switching Action) method, which consists of Time Delay Control(TDC) and a switching action of sliding mode control(SMC), has been proposed as a promising technique in the robust control area, where the plant has unknown dynamics with parameter variations and substantial disturbances are preset. When TDCSA is applied to the plant with saturation nonlinearity, however, the so-called windup phenomena are observed to arise, causing excessive overshoot and instability. The integral element of TDCSA and the saturation element of a plant cause the windup phenomena. There are two integral effects in TDCSA. One is the integral effect occurred by time delay estimation of TDC. Other is the integral term of an integral sliding surface. In order to solve this problem, we have proposed an anti-windup scheme method for TDCSA. The stability of the overall system has been proved for a class of nonlinear system. Experiment results show that the proposed method overcomes the windup problem of the TDCSA.

• ETRI Journal
• /
• v.25 no.6
• /
• pp.437-444
• /
• 2003

We derive a new joint power and rate control rule with which we can minimize the mean transmission delay in CDMA networks for a given mean transmission power. We show that it is optimal to respectively control the power inverse-linearly and the rate linearly to the square root of channel gain while maintaining the signal-to-interference ratio at a constant. We also show that the proposed joint power/rate control rule achieves excellent performance results in terms of the probability of the instantaneous delay being within a target delay against one-dimensional control schemes.

• Journal of Institute of Control, Robotics and Systems
• /
• v.10 no.12
• /
• pp.1196-1201
• /
• 2004

H₂ controller is proposed for networked control systems with time-varying delay. The time-varying network delay is assumed to be unknown, but its lower and upper bounds are assumed to be known. The time-varying delay is treated like a parameter variation and robust control technique is used to deal with the time-varying delay. The proposed controller can be computed by solving linear matrix inequalities. Through numerical simulations, the proposed controller is verified.

• Journal of Institute of Control, Robotics and Systems
• /
• v.9 no.8
• /
• pp.632-639
• /
• 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
• /
• 2003.11c
• /
• pp.441-444
• /
• 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.

• Transactions of the Korean Society of Mechanical Engineers A
• /
• v.26 no.6
• /
• pp.1035-1046
• /
• 2002

Time Delay Control(TDC) is a robust nonlinear control scheme using Time Delay Estimation(TDE) and also has a simple structure. To apply TDC to a real system, we must design Time Delay Controller to guarantee stability. The earlier research stated sufficient stability condition of TDC for general plants. In that research, it was assumed that time delay is infinitely small. But, it is impossible to implement infinitely small time delay in a real system. So, in this research we propose a new sufficient stability condition of TDC for general plants with finite time delay. And the simulation results indicate that the previous sufficient stability condition does not work even for small time delay, while our proposed condition works well.

• Journal of Institute of Control, Robotics and Systems
• /
• v.14 no.6
• /
• pp.564-572
• /
• 2008

The performance of the direct adaptive time-delay command shaping filter depends on the select time-delay. In the previously introduced direct adaptive command shaping filter, however, the time-delay value is fixed and only the magnitudes of the impulses are learned. In this paper, the authors introduce a new scheme to adapt the time-delay which is to be used in conjunction with the direct adaptive command shaping for the improved vibration suppression in flexible motion system. In order to formulate the time-delay adaptation scheme, the authors have analyzed the effect of the time-delay value on the performance of the direct adaptive command shaping filter. By modifying the direct adaptation formula based on the analysis result the authors have established a set of equations to adapt the time-delay toward the optimal value. Simulation results show the effectiveness of the proposed time-delay adaptation approach for the improved vibration suppression.

• The Transactions of the Korean Institute of Electrical Engineers D
• /
• v.53 no.7
• /
• pp.501-508
• /
• 2004

In this paper, a coordinated scheduling algorithm is proposed to reduce end-to-end delay in distributed control of systems. For the algorithm, the analysis of practical end-to-end delay in the worst case is performed priory with considering implementation of the systems. The end-to-end delay is composed of the delay caused by multi-task scheduling of operating systems, the delay caused by network communications, and the delay caused by asynchronous timing between operating systems and network communications. Through some simulation tests based on CAN(Controller Area Network), the proposed worst case end-to-end delay analysis is validated. Through the simulation tests, it is also shown that a real-time distributed control system designed to existing worst case delay cannot guarantee end-to-end time constraints. With the analysis, a coordinated scheduling algorithm is proposed here. The coordinated scheduling algorithm is focused on the reduction of the delay caused by asynchronous timing between operating systems and network communications. Online deadline assignment strategy is proposed for the scheduling. The performance enhancement of the distributed control systems by the scheduling algorithm is shown through simulation tests.

• Proceedings of the KIEE Conference
• /
• 2006.10c
• /
• pp.354-356
• /
• 2006

In this paper, the position control performance of networked control systems is analyzed when time delay through the network is considered. Integrating a control system into a network has great advantages over the traditional control system which uses point to point connection: it allows remarkable reduction in wiring, makes it easy to install and maintain the system, and improves compability. However, a networked control system has the critical defect that network uncertainties, such as time delay, can degrade the control system's performance. Therefore, the major concern of a networked control system is analyzing the effect of network uncertainties. This paper is concerned with PID controller performance for stability region, critical stability region and unstability region under the time delay in the Controller Area Network.

• 제어로봇시스템학회:학술대회논문집
• /
• 2005.06a
• /
• pp.1571-1576
• /
• 2005

DCS has many processing components and various communication elements. And its communication delay characteristic is affected diverse operating situation and context. Especially, binding signal which traversed from one control-node to another control-node undergo all sort of delay conditions. So its delay value has large deviation with the lapse of time, and the measurement of delay statistics during long time is very difficult by using general oscilloscope or other normal instruments. This thesis introduces the design and implementation of PC-based BDAS(Binding Delay Analysis System) System developed to overcomes these hardships. The system has signal-generator, IO-card, data-acquisition module, delay-calculation and analyzer module, those are implemented on industrial standard PC/Ethernet hardware and Windows/Linux platforms. This system can detect accurate whole-system-wide delay time including io, control processing and network delay, in the resolution of msec unit, and can analyze each channel's delay-historic data which is maintained by realtime database. So, this system has strong points of open system architecture, for example, user-friendly environment, low cost, high compatibility, simplicity of maintenance and high extension ability. Of all things, the measuring capability of long-time delay-statistics obtained through historic-DB make the system more valuable and useful, which function is essential to analyze accurate delay performance of DCS system. Using this system, the verification of delay performance of DCS for nuclear power plants is succeeded in KNICS(Korea Nuclear Instrumentation & Control System) projects