• Journal of Institute of Control, Robotics and Systems
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• v.4 no.4
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• pp.458-463
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• 1998

This paper presents an autopilot design method for STT missiles using the intelligent control technique and multiple controllers. The mixed $H_2/H_{\infty}$ control technique is applied for each controller design and the control gains are implemented by using the genetic searching algorithm. To facilitate automatic switching of multiple controllers under different operating conditions, an error based switching scheme is also combined with the multiple controllers at a higher level, which constitutes a hierarchical intelligent control system. It is shown via computer simulation that the proposed autopilot outperforms the conventional one.

• The Transactions of the Korean Institute of Electrical Engineers A
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• v.48 no.4
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• pp.402-409
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• 1999

Variable structure control law is well known to be a robust control algorithm and evolution strategy is used as an effective search algorithm in optimization problems. In this paper, we propose a variable structure controller with time-varying switching surface. We calculate the maximum value of seitching surface gradient that is of the 3rd order polynomial form. Evolution strategy is used to optimize the parameters of the switching surface gradient. Finally, the proposed method is applied to position tracking control for BLDC motor. Experimental results show that the proposed method is more useful than the conventional variable structure controller.

• Proceedings of the KIPE Conference
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• 2001.07a
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• pp.163-166
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• 2001

In this paper, a two-level switching algorithm ov the deadbeat to control PWM inverter is proposed. A modified algorithm of the deadbeat is suitable for the UPS system. Two levels in the pulse pattern are used. This scheme allows the use of higher switching frequency for a given computation time delay, which results in lower total harmonic distortion at the output. The proposed control scheme is implemented using TMS320F240 DSP for controlling on inverter.

• 제어로봇시스템학회:학술대회논문집
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• 1993.10b
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• pp.155-159
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• 1993

In this paper, we consider the problem of a stochastic optimal switching control, which can be applied to the control of a system with uncertain demand such as a control problem of a power plant. The dynamic programming method is applied for the formulation of the optimal control problem. We solve the system of Quasi-Variational Inequalities(QVI) using an algoritlim which involves the finite difference approximation and contraction mapping method. A mathematical example of the optimal switching control is constructed. The actual performance of the algorithm is also tested through the solution of the constructed example.

• Proceedings of the IEEK Conference
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• 2001.06a
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• pp.297-300
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• 2001

This paper proposes a sound multicast packet-switching method which can less affect QoS degradation. The method includes a switch fabric with extra switching paths dedicated for multicast packets. Presented also are both a buffering structure and a scheduling algorithm for the proposed method. Simulation analysis for the method shows that the switching delay of unicast packets is decreased even though arrival rate of multicast packets is increased.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.6 no.10
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• pp.2473-2492
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• 2012

Energy conservation is a vital issue in wireless sensor networks. Recently, employing mobile sinks for data gathering become a pervasive trend to deal with this problem. The sink can follow stochastic or pre-defined paths; however the controlled mobility pattern nowadays is taken more into consideration. In this method, the sink moves across the network autonomously and changes its position based on the energy factors. Although the sink mobility would reduce nodes' energy consumption and enhance the network lifetime, the overhead caused by topological changes could waste unnecessary power through the sensor field. In this paper, we proposed EEDARS, an energy-efficient dual-sink algorithm with role switching mechanism which utilizes both static and mobile sinks. The static sink is engaged to avoid any periodic flooding for sink localization, while the mobile sink adaptively moves towards the event region for data collection. Furthermore, a role switching mechanism is applied to the protocol in order to send the nearest sink to the recent event area, hence shorten the path. This algorithm could be employed in event-driven and multi-hop scenarios. Analytical model and extensive simulation results for EEDARS demonstrate a significant improvement on the network metrics especially the lifetime, the load and the end-to-end delay.

• Journal of Institute of Control, Robotics and Systems
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• v.15 no.10
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• pp.1029-1038
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• 2009

This paper proposes a gain switching algorithm for joint position control of a hydraulic humanoid robot. Accurate position control of the lower body is one of the basic requirements for robust balance and walking control. Joint position control is more difficult for hydraulic robots than it is for electric robots because of an absence of reduction gear and better back-drivability of hydraulic joints. Backdrivability causes external forces and torques to have a large effect on the position of the joints. External ground reaction forces therefore prevent a simple proportional-derivative (PD) controller from realizing accurate and fast joint position control. We propose a state feedback controller for joint position control of the lower body, define three modes of state feedback gains, and switch the gains according to the Zero Moment Point (ZMP) and linear interpolation. Dynamic equations of hydraulic actuators were experimentally derived and applied to a robot simulator. Finally, the performance of the algorithm is evaluated with dynamic simulations.

• The Transactions of the Korean Institute of Power Electronics
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• v.7 no.2
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• pp.137-148
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• 2002

Direct Torque Control(DTC) is considered to be an useful control scheme of high performance induction motor drives because the scheme provides a quick torque response without requiring the complex field-orientation block and inner current regulation loop. Among a few drawbacks of the conventional DTC scheme, large current harmonics due to flux drooping phenomenon in a low speed range may be the major difficulty In order to remove the difficulty, a fuzzy variable switching sector scheme and its real-time implementation algorithm are proposed in this paper. A DSP based control board is designed for the Induction motor drives with the DTC scheme including the fuzzy switching sector algorithm. Simulation and experimental results show the effectiveness of the proposed scheme.

• The KIPS Transactions:PartC
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• v.11C no.4
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• pp.527-538
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• 2004

In this paper, we present the flow aggregation method and the FLTC(flow lasting time control) algorithm to reduce the number of flows and solve the scalability problem in high speed IP switching networks. The flow aggregation based on the destination address could reduce the total number of flows, improve the label efficiency, and increase the total amount of the switched packets. The FLTC algorithm also eliminates the waste of label by deleting the flow binding efficiently. With the traces of real Internet traffics, we evaluate the performance of these schemes by simulation. The label efficiency, the average number of label used, and the percentage of packets switched and the number of packets switched are used as performance measures for this simulation.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.10 no.8
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• pp.3701-3727
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• 2016

Recently Service Function Chaining (SFC) is promising to innovate the network service mode in modern networks. However, a feasible implementation of SFC is still difficult due to the need to achieve functional equivalence with traditional modes without sacrificing performance or increasing network complexity. In this paper, we present a configurable network service chaining (CNSC) mechanism to provide services for network traffics in a flexible and optimal way. Firstly, we formulate the problem of network service chaining and design an effective service chain construction framework based on integrating software-defined networking (SDN) with network functions virtualization (NFV). Then, we model the service path computation problem as an integer liner optimization problem and propose an algorithm named SPCM to cooperatively combine service function instances with a network utility maximum policy. In the procedure of SPCM, we achieve the service node mapping by defining a service capacity matrix for substrate nodes, and work out the optimal link mapping policies with segment routing. Finally, the simulation results indicate that the average request acceptance ratio and resources utilization ratio can reach above 85% and 75% by our SPCM algorithm, respectively. Upon the prototype system, it is demonstrated that CNSC outperforms other approaches and can provide flexible and scalable network services.