Joon-Hwan Shim

Evaluation of quad ducted‐fan helicopter

Purpose – With the purpose of clearing up the risk to rotor blades, this paper develops a quad ducted‐fan helicopter using four ducted‐fans instead of four rotor blades in a quad rotor helicopter.Design/methodology/approach – Auto hovering test, auto cruise test, and altitude control simulations were conducted to estimate the flight performance of the quad ducted‐fan helicopter.Findings – Flight performance of the test quad ducted‐fan helicopter is almost same as a commercial quad rotor helicopter, and it succeeds to decrease the risk to the rotor blade. However, endurance is shorter than that of the quad rotor helicopter, because of the ducted‐fan characteristics.Research limitations/implications – The test quad ducted‐fan helicopter can fly for about four minutes with two packs of fourcell (16.8 V)‐2200 mAh Lipo batteries, and it needs about 3.3 times as much energy as quad rotor helicopter. The authors will improve the performance of quad ducted‐fan helicopter by aerodynamics analysis and design of duc...

Developments of a Cross-Correlation Calculation Algorithm for Gas Temperature Distributions Based on TDLAS

Abstract >> Most of reconstruction algorithms for the calculation of temperature distributions in CT (computedtomography)-TDLAS (tunable diode laser absorption spectroscopy) are based upon two-line thermometry method.This method gives unstable calculation convergence due to signal noise, bias error, and signal mis-matches. Inthis study, a new reconstruction algorithm based on cross-correlation for temperature calculation is proposed. The patterns of the optical signals at all wave lengths were used to reconstruct the temperature distribution. Numericaltest has been made using phantom temperature distributions. Using these phantom temperature data, absorptionspectra for all wave lengths were constructed, and these spectra were regarded as the signals that would be obtainedin an actual experiments. Using these virtually generated experimental signals, temperature distribution was onceagain reconstructed, and was compared with those of the original phantom data. Calculation errors obtained bythe newly proposed algorithm were slightly large at high temperatures with small errors at low temperature.Key words : CT(컴퓨터토모그래피), TDLAS(레이저흡수분광법), Cross-Correlation(상호상관), Numerical Test(수치적 시험), Phantom Temperature(가상 온도)

2D Temperature Measurement of CT-TDLAS by Using Two-Ratios-of-Three-Peaks Algorithm

>> In order to improve the performance of temperature field measurements by CT-TDLAS (Computer Tomography Tunable Diode Laser Absorption Spectroscopy), a new reconstruction algorithm, named two-ratiosof-three-peaks method is proposed in this paper. Further, two methods for selecting appropriate initial values of the iterative calculation of CT-TDLAS are proposed. One is MLOS (multiplicative line of sight) method and the other one is ALOS (additive line of sight) method. Two-ratios-of-three-peaks (2R3P) algorithm combined with MART (multiplicative algebraic reconstruction technique) is finally developed for the enhancements of reconstructive calculations. The results have been compared with those obtained by the conventional one-ratio-of-two-peaks (1R2P) algorithm. In order to evaluate the performance of this algorithm, numerical test has been performed using phantom Gaussian temperature distributions with 11×11 square mesh. The performance of the constructed algorithm has been demonstrated by comparing the results obtained in actual burner experiments with those obtained by thermocouples. It has been verified that 2R3P algorithm with MART and MLOS showed best performance than that of 1R2P algorithm.

Gas-Flow Sensor using Optical Fiber Bragg Grating(FBG)

We have proposed and demonstrated an gas-flow sensor using optical fiber bragg grating(FEG). The flow sensor has no electronics and no mechanical parts in its sensing part and the structure is th11s simple and immune to electromagnetic interference(EMI). The FEG sensor was consisted qf the sensing element and a coil heater. The metal coil was used to supply the current to the FEG. While some currents supply to the coil, the refractive index of the FEG under the coil is changed and thus the wavelength shift of fiber optic sensor was induced In this work, the wavelength shift according to flow-rate was experimentally studied and was used to evaluate the gas flow-rate in a gas tube. As a result, it was possible to measure the flow-rate in a linear range from 5 to with a resolution of approximately at the applied currents of 100 mA and 120 mA. The measured sensitivities were for 100 mA and for 120 mA.

Attitude control of Quad Ducted-fan Helicopter

Recently, R/C single/multi rotor helicopter is used in fields of aerial photography and aerial investigation. But helicopter rotor blades are not covered, and the thrust is generated by high rotational speed. Thus R/C helicopter has a high risk of damage. In this study, we developed a new flying object using 4 ducted-fans instead of 4 rotor blades in quad rotor helicopter. We call this as Quad Ducted-fan Helicopter.

Extra Thruster for Quad Rotor Helicopter

As R/C airplane, Quad Rotor Helicopter (QRH)is tiltedits attitude to generate horizontal force component for moving direction. So attitude control is important. In the case of autonomous control, attitude control system tilts the airframe against to the disturbance such as wind. As a result, the attitude of flying QRH always slants. In this study, extra thruster rotors are mountedto keep the position and horizontal attitude of QRH. Extra thrusters are tilted to generate thrust against to the disturbance without airframe inclination. This system is constructed with two ducted fans which can slant by two axes. To oppose the crosswind, the thruster slants the ducted fan to leeward. Because the airframe is kept the horizontal, it is suitable for a precise measurement.

Design and Implementation of PDA-based Image Surveillance System for Harbor Security using IP Camera

This paper describes a new progressive embedded Internet Protocol(IP) camera available for real-time image transmission. It was applied for ship safety and security on seashore area. The functions of developed embedded system was more effective and excellent than conventional systems. Nowadays, each nation has established harbor security systems to jump up their ports to international port. Recently Incheon port has tried to change man security into center security system used by image security system. The security system of Incheon port has some advantages like effectivity of security system and reduction of manpower and cost, installed by image security system with CCTV cameras at the entrance gate and around the fence. Thus in this paper, we have designed and implemented a Personal Digital Assistants(PDA) based Image Surveillance System for Harbor Security using IP Camera under ubiquitous environment. This system has big advantages which are more effective in an emergency and low cost and small manpower than conventional systems.

Design of a Reconfigurable Slot Antenna using Sequentially Voltage-Applied RF MEMS Switches

In this paper, we designed a reconfigurable slot antenna using sequentially voltage-applied RF MEMS switches. In order to obtain pull-in voltage and maximum stress of the MEMS switches, the switch structures in accordance with airgap height was analyzed by ANSYS simulation A actuation voltage of MEMS switches can be determined by switch geometry and airgap height between a movable plate and a bottom plate. The designed lengths of MEMS switches were 240 , 320 , 400 , respectively and the airgap was 6. The total size of the designed slot antenna was 10 mm x 10 mm and the slot length and width were 500 and 200 , respectively. The length and size of the CPW feedline were 5 mm and 30-80-30 , respectively. and then the size of the CPW in the slot was 50-300-150 . The tuning of the resonant frequency of the proposed device is realized by varying the electrical length of the antenna, which is controlled by applying the DC bias voltages to the RF MEMS switches. The designed slot antenna has been simulated, fabricated and measured