• Journal of Institute of Control, Robotics and Systems
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• v.21 no.3
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• pp.199-209
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• 2015

This paper presents a model predictive control (MPC) approach to control the steering angle in an autonomous vehicle. In designing a highly automated driving control algorithm, one of the research issues is to cope with probable risky situations for enhancement of safety. While human drivers maneuver the vehicle, they determine the appropriate steering angle and acceleration based on the predictable trajectories of surrounding vehicles. Likewise, it is required that the automated driving control algorithm should determine the desired steering angle and acceleration with the consideration of not only the current states of surrounding vehicles but also their predictable behaviors. Then, in order to guarantee safety to the possible change of traffic situation surrounding the subject vehicle during a finite time-horizon, we define a safe driving envelope with the consideration of probable risky behaviors among the predicted probable behaviors of surrounding vehicles over a finite prediction horizon. For the control of the vehicle while satisfying the safe driving envelope and system constraints over a finite prediction horizon, a MPC approach is used in this research. At each time step, MPC based controller computes the desired steering angle to keep the subject vehicle in the safe driving envelope over a finite prediction horizon. Simulation and experimental tests show the effectiveness of the proposed algorithm.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.41 no.5
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• pp.342-349
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• 2013

A damage imposed on an unmanned aerial vehicle changes the flight dynamic characteristics, and makes difficult for a conventional controller based on undamaged dynamics to stabilize the vehicle with damage. This paper presents a neural network based adaptive control method that guarantees stable control performance for an unmanned aerial vehicle even with damage on the main wing. Additionally, Pseudo Control Hedging (PCH) is combined to prevent control performance degradation by actuator characteristics. Asymmetric dynamic equations for an aircraft are chosen to describe motions of a vehicle with damage. Aerodynamic data from wind tunnel test for an undamaged model and a damaged model are used for numerical validation of the proposed control method. The numerical simulation has shown that the proposed control method has robust control performance in the presence of wing damage.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.28 no.1B
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• pp.34-44
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• 2003

As the recent rapid development of internet technology and the wide spread of multimedia communications, massive increase of network traffic causes some problems such as the lack of network paths and the bad quality of service To resolve these problems, this paper presents a web-based traffic control system which supports QoS of realtime packet transmission for the multimedia communication The traffic control system presented in this paper applies the integrated service model and provides QoS of packet transmission by means of determining the packet transmission rate according to the policies of network manager and the optimal resource allocation considering the end-to-end traffic load It also provides QoS for the realtime packet transmission through the admission controller and the packet scheduler by the modified $WF^2Q^+$ algorithm support asynchronous and class-based queuing.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.12 no.6
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• pp.132-141
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• 2013

Robotic Drilling Systems(RDSs) set the standard for the factory automation systems in aerospace manufacturing. With the benefits of cost effective drilling and predictive maintenance, RDSs can provide greater flexibility in the manufacturing process. The system can be easily adopted to manage very complex and time-consuming processes, such as automated fastening hole drilling processes of large aircraft sections, where it would be difficult accomplished by workers following teaching or conventional guided methods. However, in order to build an RDS based on a CAD model, the precise calibration of the Tool Center Point(TCP) must be performed in order to define the relationships between the fastening-hole target and the End Effector(EEF). Based on the kinematics principle, the robot manipulator requires a new method to correct the 3D errors between the CAD model of the reference coordinate system and the actual measurements. The system can be called as a successful system if following conditions can be met; a. seamless integration of the industrial robot controller and the IO Level communication, b. performing pre-defined drilling procedures automatically. This study focuses on implementing a new technology called iGPS into the fastening-hole-drilling process, which is a critical process in aircraft manufacturing. The proposed system exhibits better than 100-micron 3D accuracy under the predefined working space. Based on the proposed EEF fastening-hole machining process, the corresponding processes and programs are developed, and its feasibility is studied.

• 대한공업교육학회지
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• v.41 no.2
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• pp.89-118
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• 2016

In this study, the model of Turtle Ship, which is evaluated as one of the world's first ironclad ship in battle as well as the traditional scientific and technological heritage in Korea, was combined with the Physical Computing Platform(Arduino and App Inventor) that enables students to learn the basic concepts of IT in an easy and fun way. Thus, this study contrived the Physical Computing Platform-based Turtle Ship model which will make the students of Industrial Specialized High School develop the technological literacy and humanities-based knowledge through flexible education out of stereotype and single subject as well as enhance the potential of creative convergence education. The following is a summary of the main results obtained through this study: First, Arduino-based Main-controller design and making is helpful to learn of the hardware and software knowledge about EEC(Electron Electronics Control) and to confirm the basic characteristics and performance of interaction of Arduino and actuators. Second, The fundamental Instructional environments of abilities such as implementing EEC systems, thinking logically, and problem-solving skills were provided by designing of pattern diagram, designing an actuator circuit and making, the creation of sketches as technical programming and developing of mobile app. Thirdly, This is physical computing platform based Turtle ship model that will enable students to bring up their technological literacy and interest in the cultural heritage.

• Journal of Electrical Engineering and Technology
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• v.7 no.4
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• pp.513-523
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• 2012

For precisely regulating the speed of a permanent magnet synchronous motor system with unknown load torque disturbance and disturbance inputs, an LMI-based sliding mode control scheme is proposed in this paper. After a brief review of the PMSM mathematical model, the sliding mode control law is designed in terms of linear matrix inequalities (LMIs). By adding an extended observer which estimates the unknown load torque, the proposed speed tracking controller can guarantee a good control performance. The stability of the proposed control system is proven through the reachability condition and an approximate method to implement the chattering reduction is also presented. The proposed control algorithm is implemented by using a digital signal processor (DSP) TMS320F28335. The simulation and experimental results verify that the proposed methodology achieves a more robust performance and a faster dynamic response than the conventional linear PI control method in the presence of PMSM parameter uncertainties and unknown external noises.

• Journal of Electrical Engineering and Technology
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• v.11 no.6
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• pp.1645-1655
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• 2016

A Dynamic Voltage Restorer (DVR) model is proposed to eliminate the short-term voltage disturbances that occur in the grid-connected mode, the switching between grid-connected mode and the stand-alone mode of a Microgrid. The proposed DVR structure is based on a conventional cascaded H-bridge multilevel inverter (MLI) topology; a novel composite control strategy is presented, which could ensure the compensation ability of voltage sag by the DVR. Moreover, the compensation to specified order of harmonic is added to implement effects that zero-steady error compensation to harmonic voltage in specified order of the presented control strategy; utilizing wind turbines-batteries units as DC energy storage components in the Microgrid, the operation cost of the DVR is reduced. When the Microgrid operates under stand-alone mode, the DVR can operate on microsource mode, which could ease the power supply from the main grid (distribution network) and consequently be favorable for energy saving and emission reduction. Simulation results validate the robustness and effective of the proposed DVR system.

• The Transactions of the Korean Institute of Power Electronics
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• v.22 no.1
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• pp.53-59
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• 2017

The information on the actual voltages and actual currents of the motor is required for the sensorless control of a permanent magnet synchronous motor without rotor position sensors. In the model-based rotor position estimator of a PM synchronous motor, the reference voltages, which are the outputs of the current controller, are commonly used. The reference voltages in over-modulation regions for high-speed operation differ from the actual voltages applied to the motor. Consequently, the estimated rotor position and rotor speed may fail to track the real rotor position and real rotor speed. In this paper, the sensorless control for a PM synchronous motor in over-modulation regions for high-speed operation is proposed. The three-phase voltages applied to the motor are measured by using additional voltage detection circuits, and the performance of the rotor position estimator based on the measured three-phase voltages is validated through the experimental results.

• Journal of the Society of Naval Architects of Korea
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• v.35 no.2
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• pp.29-37
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• 1998

Linear equations of motion for submersibles are one of the rest important design parameters, which are used as a governing equation for the shape design and the controller design. But, the estimated maneuvering coefficients in equations of motion by using empirical formulae, theoretical calculations or model tests might have some errors. Therefore the maneuvering coefficients should be verified from sea trial test. In this study, parallel extended Kalman filter method, Nelder & Mead Simplex method and genetic algorithm were applied to the parameter identification of roll maneuvering coefficients based on sea trial data. As a result, it was verified that Nelder & Mead Simplex method gave the most satisfactory results for the mathmatical models and the sea trial data used in this study.

• Journal of Electrical Engineering and Technology
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• v.12 no.6
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• pp.2227-2236
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• 2017

In order to solve the neutral-point voltage fluctuation problem of three-phase three-level T-type inverters (TPTLTIs), the unbalance characteristics of capacitor voltages under different switching states and the mechanism of neutral-point voltage fluctuation are revealed. Based on the mathematical model of a TPTLTI, a feed-forward voltage balancing control strategy of DC-link capacitor voltages error is proposed. The strategy generates a DC bias voltage using a capacitor voltage loop with a proportional integral (PI) controller. The proposed strategy can suppress the neutral-point voltage fluctuation effectively and improve the quality of output currents. The correctness of the theoretical analysis is verified through simulations. An experimental prototype of a TPTLTI based on Digital Signal Processor (DSP) is built. The feasibility and effectiveness of the proposed strategy is verified through experiment. The results from simulations and experiment match very well.