• Journal of Internet Computing and Services
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• v.18 no.5
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• pp.17-22
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• 2017

In a MPC coding using excitation source of voiced and unvoiced, it would be a distortion of speech waveform. This is caused by normalization of synthesis speech waveform of voiced in the process of restoration the multi-pulses of representation section. This paper present PCFBD-MPC( Position Compensation Frequency Band Division-Multi Pulse Coding ) used V/UV/S( Voiced / Unvoiced / Silence ) switching, position compensation in a multi-pulses each pitch interval and Unvoiced approximate-synthesis by using specific frequency in order to reduce distortion of synthesis waveform. Also, I was implemented that the PCFBD-MPC( Position Compensation Frequency Band Division-Multi Pulse Coding ) system and evaluate the SNRseg of PCFBD-MPC in coding condition of 8kbps. As a result, SNRseg of PCFBD-MPC was 13.4dB for female voice and 13.8dB for male voice respectively. In the future, I will study the evaluation of the sound quality of 8kbps speech coding method that simultaneously compensation the amplitude and position of multi-pulse source. These methods are expected to be applied to a method of speech coding using sound source in a low bit rate such as a cellular phone or a smart phone.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.17 no.1
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• pp.159-164
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• 2016

This paper reports the load factor logic design for a fly-by-wire helicopter flight envelope protection. As a helicopter is very complex system with a rotor, fuselage, engine, etc., there are many constraints on the flight region. Because of these constraints, pilots should consider them carefully and have a heavy workload, which causes controllability degradation. In this respect, automatic logic is needed to free the pilot from these considerations. As one of these logics, the flight envelope protection logic for the load factor of a FBW helicopter was designed. The flight to exceed the load factor is caused by an abrupt pitch cyclic stick change. In this scheme, the load factor limit logic was added between the pilot stick command block and pitch attitude command block. From the current load value, the available attitude range was calculated dynamically and simulated on the helicopter simulator model to verify the performance. A comparison of the simulation results at the hovering and forward speed region with and without applying the load limiting logic showed that the load factor limit was exceeded more than 20% when the logic was not applied, whereas with the load factor limit logic the load factor was within the limit. In conclusion, a dynamically allocated limitation logic to helicopter FBW controller was verified by simulation.

• Journal of Aerospace System Engineering
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• v.13 no.6
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• pp.52-59
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• 2019

The rotor blade is a key component that generates the lift, thrust, and control forces required for helicopter flight by the torque transmitted through the hub and the blade pitch angle control, and should be designed to factor vibration characteristics so that there is no risk of resonance with structural safety. In this study, the structural design of the main rotor blade for MPUH(Multi-Purpose Unmanned Helicopter) was conducted and the sectional stiffness measurement of the fabricated blade was performed. The evaluation of the vibration characteristics of the main rotor system was then conducted factoring the measured stiffness distribution. The interior of the rotor blade comprised of the skin, spar, and torsion box, and carbon and glass fiber composites were applied. The Ksec2D program was applied to predict the stiffness of blade, and the results were compared to the measured data. CAMRADII, a comprehensive rotorcraft analysis program, was applied to investigate the natural frequency trends and resonance risks due to the rotor rotation.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.32 no.10
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• pp.77-82
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• 2004

This paper presents polar converting logic(PCL) of BTT missiles against slowly moving or stationary targets. A guidance commands expressed in rectangular coordinates must be converted in the form of polar coordinates for BTT control. Since conventional PCL has nonlinear and discontinuous function, the missiles may lose controllability when pitch acceleration command equals to zero. Further, roll coupling may have a serious unstabilizing influence on homing guidance with two gimbals seeker. In this paper, a linear homotopy equation is introduced to improve the controllability and a command following performance at midcourse phase. We also design a PCL which is less sensitive to pitch acceleration command so that it may improve the stability of the homing loop. To substantiate our conclusion, results of the computer simulation have been illustrated.

• 한국신재생에너지학회:학술대회논문집
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• 2009.06a
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• pp.491-494
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• 2009

This paper introduces the design concepts and characteristics of WinDS3000$^{TM}$ which is a trade mark of Doosan's 3MW offshore/onshore wind turbine. WinDS3000$^{TM}$ has been designed in consideration of high RAMS (Reliability, Availability, Maintainability and Serviceability) and cost effectiveness for the TC Ia condition in GL guideline. An integrated drive train design with an innovative three-stage gearbox has been introduced to minimize nacelle weight of the wind turbine and to enhance a high reliability for transmission. A permanent magnet generator with full converter system has been introduced to get higher efficiency in part load operation, and grid friendliness use of 50 Hz and 60 Hz grid. A pitch regulated variable speed power control with individual pitch system has been introduced to regulate rotor torque while generator reaction torque can be adjusted almost instantaneously by the associated power electronics. An individual pitch control system has been introduced to reduce fatigue loads of blade and system. The wind turbine has been also equipped with condition monitoring and diagnostic systems in order to meet maintainability requirements. And internal maintenance crane in nacelle has been developed. As a result, the maintenance cost was dramatically reduced and maintenance convenience also enhanced in offshore condition.

• Journal of the Korea Institute of Military Science and Technology
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• v.13 no.6
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• pp.967-975
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• 2010

There have been a lot of efforts on the improvement for the ride comfort and handling stability of the combat vehicles. Especially most of vehicles for military purpose have bad inertial condition and severe operating condition such as the rough road driving, and need a high mobility in the emergency status. It is necessary to apply the controlled suspension system in order to improve the vehicle mobile stability and ride comfort ability of crews. A feasibility study is performed on the application of the semi-active suspension system with a magneto-rheological controlled shock absorber for a $6{\times}6$ combat vehicle. First, the dynamic simulation model of the vehicle including the control model for the semi-active suspension system was executed. Based on this model, a hardware-in-the-loop simulation(HILS) system which has a semi-active suspension controller hardware was constructed. After full vehicle simulations were performed in virtual proving courses with this system, the semi-active suspension system was proven to give better ride comfort and handling stability in comparison with the conventional passive suspension system.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.13 no.4
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• pp.142-151
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• 1999

Linear Pulse Motors (LPM) are used a field where SImOth linear motion is required, and it's position accuracy higher than that of a lead According to the advanUlge such as simplicity of rrechanical frarre, high reliability, precise open-loop operation, low inertia etc. LPM is awlied largely where it have made motor of this kind more and rmre attractive in many application areas such as factory automation and high speed positioning. This paper is researched to analyze for force characteristics of hybrid LPM with high accuracy and repeatability. Both the thrust and normal force are very sensitive to the airgap and tooth pitches of the forcer and platen. Here, the thrust shows a high content while the normal force is much higher than the thrust. For magnetic circuits of hybrid LPM is the complicated structure, the finite element rrethod (FEM) is employed with suitable rrethod for calculating the force. Therefore, both the virtual work principle and maxwell stress tensor have been used.n used.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.36 no.9
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• pp.1017-1026
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• 2012

In this study, an exoskeleton-type robot is developed to assist frozen shoulder rehabilitation in a systematic and efficient manner for humans. The developed robot has two main features. The first is a structural feature: this robot was designed to rehabilitate both shoulders of a patient, and the three axes of the shoulder meet at one point to generate human-like ball joint motions. The second is a functional feature that is divided into two rehabilitation modes: the first mode is a joint rehabilitation mode that helps to recover the shoulder's original range of motion by moving the patient's shoulder according to patterns obtained by motion capture, and the second mode is a muscle rehabilitation mode that strengthens the shoulder muscles by suitably resisting the patient's motion. Through these two modes, frozen shoulder rehabilitation can be performed systematically according to the patient's condition. The development procedure is described in detail.

• Journal of Advanced Navigation Technology
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• v.25 no.6
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• pp.441-449
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• 2021

With advances in autonomous vehicles, there is a growing demand for more accurate position estimation. Especially, this is a case for a moving robot for the indoor operation which necessitates the higher accuracy in position estimation when the robot is required to execute the task at a predestined location. Thus, a method for improving the position estimation which is applicable to both the fixed and the moving object is proposed. The proposed method exploits the initial position estimation from Bluetooth beacon signals as observation signals. Then, it estimates the gravitational acceleration applied to each axis in an inertial frame coordinate through computing roll and pitch angles and combining them with magnetometer measurements to compute yaw angle. Finally, it refines the control inputs for an object with motion dynamics by computing acceleration on each axis, which is used for improving the performance of Kalman filter. The experimental assessment of the proposed algorithm shows that it improves the position estimation accuracy in comparison to a conventional Kalman filter in terms of average error distance at both the fixed and moving states.

• Journal of the Microelectronics and Packaging Society
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• v.15 no.3
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• pp.27-33
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• 2008

With increasing use of portable appliances such as PDA and cellular phone, changing environment of applications requires higher solder joint reliability. The ENIG (Electroless Nickel Immersion Gold) process has been widely used for fine pitch SMT (Surface Mount Technology) and BGA (Ball Grid Array) packaged devices due to its benefits including excellent solderability, high uniformity and substantial legibility throughout the packaging process. Its brittle fracture of solder, however, has received increasingly attentions. It was Down that fracture brittleness is mainly related with black pad resulting from galvanic nickel corrosion and P-enriched layer formation between the IMC (Intermetallic Compounds) and electroless nickel layer. Theoretically, smooth electroless Ni layer was blown to have a advantages in minimizing the black pad phenomenon by uniform solution exchange during immersion gold plating. Nevertheless, how to control the surface morphology of electroless Ni layer has been hardly blown. This study investigates an effect of surface morphology of Cu underlayer on surface morphology of electroless Ni layer. To obtain various kinds of surface morphology of Cu layer, two types of Cu etching chemical and a number of Cu etching treatment were applied.