• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.29 no.10
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• pp.647-651
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• 2016

The power relay can easily control high voltage and high current through metallic contacts. In addition, it has the advantage in reasonable price. So it has been used in many applications. But the power relay has a weak point by mechanical movements. These mechanical movements cause the bouncing phenomenon. Arc and bouncing phenomenon are the main causes of electric abrasion and material erosion. In this study, mechanical repetitive experiments and repetitive experiments in electrically connected state are conducted. Then these two experimental results in terms of bouncing phenomenon and changes in the contact surface are compared. In all number of repetitions, contacts in an electrically connected state cause smaller number of bounce. Also, It has lower contents of silver on eroded surface than the other. The experimental results would be helpful to the further study of contacts life span.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.40 no.5
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• pp.931-937
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• 2015

Distributed relay scheme for wireless ad hoc multi-hop multicast network composed of low-power and low-complexity wireless devices with high density is proposed. The proposed relay scheme is shown to be better than flooding, which is the distributed relay scheme applied to ZigBee, in the outage probability and the multicast transmission rate by simulations.

• Journal of Institute of Control, Robotics and Systems
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• v.22 no.11
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• pp.925-931
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• 2016

The BLDC motor is used widely in industry due to its controllability and freedom from maintenance because there is no mechanical brush in the BLDC motor. Furthermore, it is suitable for high-speed applications, such as compressors and air blowers. For instance, for a compressor with a small impeller due to miniaturizing, the BLDC motor has to rotate at a very high speed to maintain the compression ratio of the compressor. Typically, to reach an ultra-high speed, airfoil bearings must be used in place of ball bearings because of their friction. Unfortunately, the characteristics of airfoil bearings change drastically depending on the revolution speed. In this paper, a BLDC motor with airfoil bearings is controlled with a PID controller. To analyze and determine the PID coefficients, the relay-feedback method is used. Additionally, for adaptive control, a fuzzy logic controller is used. Furthermore, the auto-tuning and self-tuning techniques are combined to control the BLDC motor. The proposed method is able to control the airfoil-bearing BLDC motor efficiently.

• KIPS Transactions on Computer and Communication Systems
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• v.6 no.5
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• pp.211-218
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• 2017

Recent robot software platform research focuses on providing intelligent service via abstraction of robot devices. Context-aware techniques are necessary for intelligent robot services, which are based on the perception of environmental information obtained from heterogeneous sensors in IoT environment. Robot Operating System (ROS) provides protocols to operate robot devices. ROS includes functions for abstracting heterogeneous sensors themselves in order to control the robot, however, it lacks the ability to provide context information that the robot can perceive based on environmental information through consistent collection methods. In this paper, we propose a relay system for ROS to provide context-aware robot service. The proposed system makes it possible for ROS to control and provide context-aware robot services with relay of an external context-aware system and ROS. In experiments, we demonstrate procedures that robot services abstracted from ROS and an external context-aware system works together based on the proposed system.

• Korean Chemical Engineering Research
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• v.58 no.2
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• pp.190-196
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• 2020

The step to obtain a process dynamic model through process experiments is very important because it needs times and expenditures. Step response method is one of the standard methods to have long been used for understanding process dynamics, obtaining dynamical models and designing control systems. For the step response, it is usually required to measure process output for a step input change in the open-loop manner. Its disadvantage criticized is the long open-loop operation. For this, a method based on the time-optimal control technique to minimize the test time for obtaining the step response has been recently presented. However, the method requires iterative computations for the minimization of test times. Here, a method where iterative computations are not required is proposed. Simulation results are presented to show that test times to obtain step responses are reduced considerably and an autotuning method based on the proposed method is compared with the relay feedback autotuning method accepted widely for the autotuning of controllers.

• Journal of the Korean Institute of Gas
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• v.15 no.3
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• pp.47-52
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• 2011

The purpose of this paper analyzes and studies to seek the failure examples of electronic control actuators for engine in liquified petroleum gas vehicle. The first, it was verified phenomenon for intial starting damage and no-acceleration of engine because of occasionally fuel feeding interception by clogged of emergency cutting solenoid valve filter. The second, the contact resistance produced in the connecting part of engine control relay because of no fully surface contacting by processes and assembly badness. It was displayed phenomenon of re-starting badness. The actuator that idle speed control system was sticked inside because of intake-air decreasing by carbon deposit. As a result, it was verified the phenomenon of disharmony that repeated up and down the engine revolution.

• KIPS Transactions on Computer and Communication Systems
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• v.10 no.6
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• pp.173-180
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• 2021

Non Orthogonal Multiple Access (NOMA) is a technology to guarantee the explosively increased Quality of Service(QoS) of users in 5G networks. NOMA can remove the frequent orthogonality in Orthogonal Multiple Access (OMA) while allocating the power differentially to classify user signals. NOMA can guarantee higher communication speed than OMA. However, the NOMA has one disadvantage; it consumes a more energy power when the distance increases. To solve this problem, relay nodes are employed to implement the cooperative NOMA control idea. In a cooperative NOMA network, relay node participations for cooperative communications are essential. In this paper, a new bandwidth allocation scheme is proposed for cooperative NOMA platform. By employing the idea of Vickrey-Clarke-Groves (VCG) mechanism, the proposed scheme can effectively prevent selfishly actions of relay nodes in the cooperative NOMA network. Especially, base stations can pay incentives to relay nodes as much as the contributes of relay nodes. Therefore, the proposed scheme can control the selfish behavior of relay nodes to improve the overall system performance.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.8 no.2
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• pp.618-633
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• 2014

Relay technology is becoming more important for mobile communications and wireless internet of things (IoT) networking because of the extended access network coverage range and reliable quality of service (QoS) it can provide at low power consumption levels. Existing mobile multihop relay (MMR) technology uses fixed-point stationary relay stations (RSs) and a divided time-frame (or frequency-band) to support the relay operation. This approach has limitations when a local fixed-point stationary RS does not exist. In addition, since the time-frame (or frequency-band) channel resources are pre-divided for the relay operation, there is no way to achieve high channel utilization using intelligent opportunistic techniques. In this paper, a different approach is considered, where the use of mobile/IoT devices as RSs is considered. In applications that use mobile/IoT devices as relay systems, due to the very limited battery energy of a mobile/IoT device and unequal channel conditions to and from the RS, both minimum energy consumption and QoS support must be considered simultaneously in the selection and configuration of RSs. Therefore, in this paper, a mobile RS is selected and configured with the objective of minimizing power consumption while satisfying end-to-end data rate and bit error rate (BER) requirements. For the RS, both downlink (DL) to the destination system (DS) (i.e., IoT device or user equipment (UE)) and uplink (UL) to the base station (BS) need to be adaptively configured (using adaptive modulation and power control) to minimize power consumption while satisfying the end-to-end QoS constraints. This paper proposes a minimum transmission power consuming RS selection and configuration (MPRSC) scheme, where the RS uses cognitive radio (CR) sub-channels when communicating with the DS, and therefore the scheme is named MPRSC-CR. The proposed MPRSC-CR scheme is activated when a DS moves out of the BS's QoS supportive coverage range. In this case, data transmissions between the RS and BS use the assigned primary channel that the DS had been using, and data transmissions between the RS and DS use CR sub-channels. The simulation results demonstrate that the proposed MPRSC-CR scheme extends the coverage range of the BS and minimizes the power consumption of the RS through optimal selection and configuration of a RS.

• Journal of Institute of Control, Robotics and Systems
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• v.10 no.12
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• pp.1280-1286
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• 2004

A lot of industrial chemical processes contain certain input nonlinearities even though they are controlled by several linear controllers. Here we investigate a sequential loop closing identification method for MIMO Hammerstein nonlinear processes with diagonal nonlinearities. The proposed method separates the identification of the nonlinear static function from that of the linear subsystem by using a relay feedback test and a triangular type signal test. From 2 n activations for n n MIMO nonlinear processes, we sequentially identify the whole range of the nonlinear static function as well as the transfer function matrix of the linear subsystem.

• 제어로봇시스템학회:학술대회논문집
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• 1997.10a
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• pp.704-707
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• 1997

In this paper, we present a fuzzy logic based tuner for continuous on-line tuning of PID controllers. The essential idea of the scheme is to parameterize a Ziegler-Nichols-like tuning formula by a singler parameter .alpha., then to use an on line fuzzy logic to self-tune the parameter. The adaptive scaling makes the controller robust against large variations in parametric and dynamics uncertainties in the plant model. New self-tuning controller has the ability to decide when to use PI or PID control by extracting process dynamics from relay experiments. These scheme lead to improved performance of the transient and steady state behavior of the closed loop system, including processes with nonminimum phase processes.