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REFERENCE LINKING PLATFORM OF KOREA S&T JOURNALS
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International Journal of Aeronautical and Space Sciences
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Journal DOI :
The Korean Society for Aeronautical & Space Sciences
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Volume & Issues
Volume 10, Issue 2 - Nov 2009
Volume 10, Issue 1 - May 2009
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Study on Path Planning Algorithms for Unmanned Agricultural Helicopters in Complex Environment
Moon, Sang-Woo ; Shim, David Hyun-Chul ;
International Journal of Aeronautical and Space Sciences, volume 10, issue 2, 2009, Pages 1~11
DOI : 10.5139/IJASS.2009.10.2.001
In this paper, two algorithms to solve the path planning problem with constraints from obstacles are presented. One proposed Algorithm is "Grid point-based path planning". The first step of this algorithm is to set points which can be the waypoints around the field. These points can be located inside or outside of the field or the obstacles. Therefore, we should determine whether those points are located in the field or not. Using the equations of boundary lines for a region that we are interested in is an effective approach to handle. The other algorithm is based on the boundary lines of the agricultural field, and the concept of this algorithm is well known as "boustrophedon method". These proposed algorithms are simple but powerful for complex cases since it can generate a plausible path for the complex shape which cannot be represented by using geometrical approaches efficiently and for the case that some obstacles or forbidden regions are located on the field by using a skill of discriminants about set points. As will be presented, this proposed algorithm could exhibit a reasonable accuracy to perform an agricultural mission.
Rotorcraft Waypoint Guidance Design Using SDRE Controller
Yang, Chang-Deok ; Kim, Chang-Joo ; Yang, Soo-Seok ;
International Journal of Aeronautical and Space Sciences, volume 10, issue 2, 2009, Pages 12~22
DOI : 10.5139/IJASS.2009.10.2.012
This paper deals with the State-Dependent Riccati Equation (SDRE) Technique for the design of rotorcraft waypoint guidance. To generate the flight trajectory through multiple waypoints, we use the trigonometric spline. The controller design and its validation is based upon a level 2 simulation rotorcraft model and the designed SDRE controller is applied to the trajectory tracking problems. To verify the designed guidance law, the simulation environment of high fidelity rotorcraft model is developed using three independent PCs. This paper focuses on the validation of rotorcraft waypoint guidance law which is designed by using SDRE Controller.
Development of an Unsteady Aerodynamic Analysis Module for Rotor Comprehensive Analysis Code
Lee, Joon-Bae ; Yee, Kwan-Jung ; Oh, Se-Jong ; Kim, Do-Hyung ;
International Journal of Aeronautical and Space Sciences, volume 10, issue 2, 2009, Pages 23~33
DOI : 10.5139/IJASS.2009.10.2.023
The inherent aeromechanical complexity of a rotor system necessitated the comprehensive analysis code for helicopter rotor system. In the present study, an aerodynamic analysis module has been developed as a part of rotorcraft comprehensive program. Aerodynamic analysis module is largely classified into airload calculation routine and inflow analysis routine. For airload calculation, quasi-steady analysis model is employed based on the blade element method with the correction of unsteady aerodynamic effects. In order to take unsteady effects - body motion effects and dynamic stall - into account, aerodynamic coefficients are corrected by considering Leishman-Beddoes's unsteady model. Various inflow models and vortex wake models are implemented in the aerodynamic module to consider wake induced inflow. Specifically, linear inflow, dynamic inflow, prescribed wake and free wake model are integrated into the present module. The aerodynamic characteristics of each method are compared and validated against available experimental data such as Elliot's induced inflow distribution and sectional normal force coefficients of AH-1G. In order to validate unsteady aerodynamic model, 2-D unsteady model for NACA0012 airfoil is validated against aerodynamic coefficients of McAlister's experimental data.
Development of On-line Performance Diagnostic Program of a Helicopter Turboshaft Engine
Kong, Chang-Duk ; Koo, Young-Ju ; Kho, Seong-Hee ; Ryu, Hye-Ok ;
International Journal of Aeronautical and Space Sciences, volume 10, issue 2, 2009, Pages 34~42
DOI : 10.5139/IJASS.2009.10.2.034
Gas turbine performance diagnostics is a method for detecting, isolating and quantifying faults in gas turbine gas path components. On-line precise fault diagnosis can promote greatly reliability and availability of gas turbine in real time operation. This work proposes a GUI-type on-line diagnostic program using SIMULINK and Fuzzy-Neuro algorithms for a helicopter turboshaft engine. During development of the diagnostic program, a look-up table type base performance module are used for reducing computer calculating time and a signal generation module for simulating real time performance data. This program is composed of the on-line condition monitoring program to monitor on-line measuring performance condition, the fuzzy inference system to isolate the faults from measuring data and the neural network to quantify the isolated faults. Evaluation of the proposed on-line diagnostic program is performed through application to the helicopter engine health monitoring.
Calibration of a Five-Hole Multi-Function Probe for Helicopter Air Data Sensors
Kim, Sung-Hyun ; Kang, Young-Jin ; Myong, Rho-Shin ; Cho, Tae-Hwan ; Park, Young-Min ; Choi, In-Ho ;
International Journal of Aeronautical and Space Sciences, volume 10, issue 2, 2009, Pages 43~51
DOI : 10.5139/IJASS.2009.10.2.043
In the flight of air vehicles, accurate air data information is required to control them effectively. Especially, helicopters are often put in drastic motion involved with high angle of attacks in order to perform difficult missions. Among various sensors, the multi function probe (MFP) has been used in the present study mainly owing to its advantages in structural simplicity and capability of providing various information such as static and total pressure, speed, and pitch and yaw angles. In this study, a five-hole multi-function probe (FHMFP) is developed and its calibration is conducted using multiple regressions. In this work a calibration study on the FHMFP, an air data sensor for helicopters, is reported. It is shown that the pitch and yaw angles' accuracy of calibration is
at a cone angle of
, respectively, which is summarized in table 3.
KFLOW Results of Airloads on HART-II Rotor Blades with Prescribed Blade Deformation
Sa, Jeong-Hwan ; Kim, Jee-Woong ; Park, Soo-Hyung ; Park, Jae-Sang ; Jung, Sung-Nam ; Yu, Yung-Hoon ;
International Journal of Aeronautical and Space Sciences, volume 10, issue 2, 2009, Pages 52~62
DOI : 10.5139/IJASS.2009.10.2.052
A three-dimensional compressible Navier-Stokes solver, KFLOW, using overlapped grids has recently been developed to simulate unsteady flow phenomena over helicopter rotor blades. The blade-vortex interaction is predicted for a descending flight using measured blade deformation data. The effects of computational grid resolution and azimuth angle increments on airloads were examined, and computed airloads and vortex trajectories were compared with HART-II wind tunnel data. The current method predicts the BVI phenomena of blade airloads reasonably well. It is found from the present study that a peculiar distribution of vorticity of tip vortices in an approximate azimuth angle range of 90 to 180 degrees can be explained by physics of the shear-layer interaction as well as the dissipation of numerical schemes.
Numerical Investigation on Overlap Effects of Tandem Rotors in Forward Flight
Lee, Jae-Won ; Oh, Se-Jong ; Yee, Kwan-Jung ; Kim, Deog-Kwan ;
International Journal of Aeronautical and Space Sciences, volume 10, issue 2, 2009, Pages 63~76
DOI : 10.5139/IJASS.2009.10.2.063
A study on the interference effects of overlapping tandem rotors in forward flight is conducted using the time-marching free-wake panel method which adopts field velocity boundary integral formulation. The conventional boundary integral formulation is numerically unstable for the cases when the blade and the wake are in close proximity to each other. In order to avoid this problem, this study applies the field velocity method and modifies the boundary integration formulation. The improved method is used for the parametric study on the advance ratio and the distance between the rotors. These are the parameters that most affect the interference of the tandem rotor in forward flight. Comparison of the aerodynamic performance shows that the horizontal distance between the rotors negligibly influences the overlap-induced power factor for high advance ratio. In addition, it shows that the overlap-induced power factor is inversely proportional to the squared vertical distance between the rotors, and that the overlap-induced power factor increases to a certain extent and decrease back as the advance ratio increases.
General Purpose Cross-section Analysis Program for Composite Rotor Blades
Park, Il-Ju ; Jung, Sung-Nam ; Kim, Do-Hyung ; Yun, Chul-Yong ;
International Journal of Aeronautical and Space Sciences, volume 10, issue 2, 2009, Pages 77~85
DOI : 10.5139/IJASS.2009.10.2.077
A two-dimensional cross-section analysis program based on the finite element method has been developed for composite blades with arbitrary cross-section profiles and material distributions. The modulus weighted approach is used to take into account the non-homogeneous material characteristics of advanced blades. The CLPT (Classical Lamination Plate Theory) is applied to obtain the effective moduli of the composite laminate. The location of shear center for any given cross-sections are determined according to the Trefftz' definition while the torsion constants are obtained using the St. Venant torsion theory. A series of benchmark examples for beams with various cross-sections are illustrated to show the accuracy of the developed cross-section analysis program. The cross section cases include thin-walled C-channel, I-beam, single-cell box, NACA0012 airfoil, and KARI small-scale blades. Overall, a reasonable correlation is obtained in comparison with experiments or finite element analysis results.
Development of a Point Tracking System for Measuring Structural Deformations Using Commercial Video Cameras
Kim, Hong-Il ; Kim, Ho-Young ; Park, Hyun-Jin ; Han, Jae-Hung ; Kim, Jun-Bum ; Kim, Do-Hyung ; Han, Jeong-Ho ;
International Journal of Aeronautical and Space Sciences, volume 10, issue 2, 2009, Pages 86~94
DOI : 10.5139/IJASS.2009.10.2.086
This paper deals with the creation of a new, low-cost point/position tracking system that can measure deformations in engineering structures with simple commercially widespread cameras. Though point tracking systems do exist today, such as Stereo Pattern Recognition (SPR) and Projection Moir
Interferometry (PMI) systems, they are far too costly to use to analyze small, simple structures because complex optical components such as large flashes, high-resolution cameras and data acquisition systems with several computers are required. We developed a point tracking system using commercial cameras. This system used IR LEDs and commercial IR CCD cameras to minimize the interference posed by other extraneous light sources. The main algorithm used for this system is an optical point tracking algorithm, which is composed of the point extraction algorithm and the point matching algorithm for 3-D motion estimation. a series of verification tests were performed. Then, the developed point tracking system was applied to measure deformations of an acrylic plate under a mechanical load. The measured deformations of the acrylic plate matched well with the numerical analysis results. The results indicate that the developed point tracking system is reliable enough to measure continuous deformed shapes of various engineering structures.
Predicting BVI Loadings and Wake Structure of the HARTII Rotor Using Adaptive Unstructured Meshes
Yu, Dong-Ok ; Jung, Mun-Seung ; Kwon, Oh-Joon ; Yu, Yung-H. ;
International Journal of Aeronautical and Space Sciences, volume 10, issue 2, 2009, Pages 95~105
DOI : 10.5139/IJASS.2009.10.2.095
The flow fields around the HARTII rotor were numerically investigated using a viscous flow solver on adaptive unstructured meshes. An overset mesh and a deforming mesh technique were used to handle the blade motion including blade deflection, which was obtain from the HARTII experimental data. A solution-adaptive mesh refinement technique was also used to capture the rotor wake effectively. Comparison of the sectional normal force and pitching moment at 87% radial station between the two cases, with and without the blade deflection, showed that the blade loading is significantly affected by blade torsion. It was found that as the mesh was refined, the strength of tip vortex is better preserved, and the magnitude of high frequency blade loading, caused by blade-vortex interaction (BVI), is further magnified. It was also found that a proper time step size, which corresponds to the cell size, should be used to predict unsteady solutions accurately. In general, the numerical results in terms of the unsteady blade loading and the rotor wake show good agreement with the experimental data.
Evolution of Tip Vortices Generated by Two Bladed Rotor in Hover at Early Wake Ages
Park, Byung-Ho ; Han, Yong-Oun ;
International Journal of Aeronautical and Space Sciences, volume 10, issue 2, 2009, Pages 106~116
DOI : 10.5139/IJASS.2009.10.2.106
In order to investigate change of vortex structures and its evolving proceses, two dimensional LDV system was used for measurement of velocity vectors of tip vortex, and PIV system was also used for visualizations of tip vortex array for two bladed rotor, respectively. Experiments provided vortex locations, tangential and axial velocity components of tip vortex at six wake ages of 9.5, 10.5, 60.5, 99.5, 129.5, 169.5 and corresponded six wake ages shifted with 180 degrees per each. It was resulted that tip vortices generated by the first blade satisfy Landgrebe's model for their vortex locations even after they were accelerated by the second blade in downstream. Tangential velocity components of tip vortices follow Vatistas' n=2 model on both inside and outside regions of rotor slipstream without loss of vortex circulation. Axial velocity profiles revealed that there were small but significant perturbations just outside the primary vortex core which implies the second blade affects the wake substantially. It was also found that tip paths of each blade were not willing to be coincided intrinsically.
Signal Processing Algorithm to Reduce RWR Electro-Magnetic Interference with Tail Rotor Blade of Helicopter
Im, Hyo-Bin ; Go, Eun-Kyoung ; Jeong, Un-Seob ; Lyu, Si-Chan ;
International Journal of Aeronautical and Space Sciences, volume 10, issue 2, 2009, Pages 117~124
DOI : 10.5139/IJASS.2009.10.2.117
In the environment where various and complicated threat signals exist, RWR (Radar Warning Receiver), which can warn pilot of the existence of threats, has long been a necessary electronic warfare (EW) system to improve survivability of aircraft. The angle of arrival (AOA) information, the most reliable sorting parameter in the RWR, is measured by means of four-quadrant amplitude comparison direction finding (DF) technique. Each of four antennas (usually spiral antenna) of DF unit covers one of four quadrant zones, with 90 degrees apart with nearby antenna. According to the location of antenna installed in helicopter, RWR is subject to signal loss and interference by helicopter body and structures including tail bumper, rotor blade, and so on, causing a difficulty of detecting hostile emitters. In this paper, the performance degradation caused by signal interference by tail rotor blades has been estimated by measuring amplitude video signals into which RWR converts RF signals in case a part of antenna is screened by real tail rotor blade in anechoic chamber. The results show that corruption of pulse amplitude (PA) is main cause of DF error. We have proposed two algorithms for resolving the interference by tail rotor blades as below: First, expand the AOA group range for pulse grouping at the first signal analysis phase. Second, merge each of pulse trains with the other, that signal parameter except PRI and AOA is similar, after the first signal analysis phase. The presented method makes it possible to use RWR by reducing interference caused by blade screening in case antenna is screened by tail rotor blades.
Navier-Stokes Simulation of Unsteady Rotor-Airframe Interaction with Momentum Source Method
Kim, Young-Hwa ; Park, Seung-O ;
International Journal of Aeronautical and Space Sciences, volume 10, issue 2, 2009, Pages 125~133
DOI : 10.5139/IJASS.2009.10.2.125
To numerically simulate aerodynamics of rotor-airframe interaction in a rigorous manner, we need to solve the Navier-Stokes system for a rotor-airframe combination as a whole. This often imposes a serious computational burden since rotating blades and a stationary body have to be simultaneously dealt with. An efficient alternative is to adopt a momentum source method in which the action of rotor is approximated as momentum source over a rotor disc plane in a stationary computational domain. This makes the simulation much simpler. For unsteady simulation, the instantaneous momentum sources are assigned only to a portion of disk plane corresponding to blade passage. The momentum source is obtained by using blade element theory with dynamic inflow model. Computations are carried out for the simple rotor-airframe model (the Georgia Tech model) and the results of the simulation are compared with those of the full Navier-Stokes simulation with moving mesh system for rotor and with experimental data. It is shown that the present simulation yields results as good as those of the full Navier-Stokes simulation.
Development of an Advanced Rotorcraft Preliminary Design Framework
Lim, Jae-Hoon ; Shin, Sang-Joon ; Kim, June-Mo ;
International Journal of Aeronautical and Space Sciences, volume 10, issue 2, 2009, Pages 134~139
DOI : 10.5139/IJASS.2009.10.2.134
Various modules are generally combined with one another in order to perform rotorcraft preliminary design and its optimization. At the stage of the preliminary design, analysis fidelity is less important than the rapid assessment of a design is. Most of the previous researchers attempted to implement sophisticated applications in order to increase the fidelity of analysis, but the present paper focuses on a rapid assessment while keeping the similar level of fidelity. Each small-sized module will be controlled by an externally-operated global optimization module. Results from each module are automatically handled from one discipline to another which reduces the amount of computational effort and time greatly when compared with manual execution. Automatically handled process decreases computational cycle and time by factor of approximately two. Previous researchers and the rotorcraft industries developed their own integrated analysis for rotorcraft design task, such as HESCOMP, VASCOMP, and RWSIZE. When a specific mission profile is given to these programs, those will estimate the aircraft size, performance, rotor performance, component weight, and other aspects. Such results can become good sources for the supplemental analysis in terms of stability, handling qualities, and cost. If the results do not satisfy the stability criteria or other constraints, additional sizing processes may be used to re-evaluate rotorcraft size based on the result from stability analysis. Trade-off study can be conducted by connecting disciplines, and it is an important advantage in a preliminary design study. In this paper among the existing rotorcraft design programs, an adequate program is selected for a baseline of the design framework, and modularization strategy will be applied and further improvements for each module be pursued.
Design and Development of Multi-rotorcraft-based Unmanned Prototypes of Personal Aerial Vehicle
Muljowidodo, Muljowidodo ; Budiyono, Agus ;
International Journal of Aeronautical and Space Sciences, volume 10, issue 2, 2009, Pages 140~147
DOI : 10.5139/IJASS.2009.10.2.140
The paper presents the design, development and testing activities of the multi-rotorcraft-based unmanned aerial vehicle at the Center for Unmanned System Studies, Institut Teknologi Bandung (ITB), Indonesia. The multi-rotor system was selected as the design stepping stone for future development of personal aerial vehicle prototypes. A step-by-step design program is conducted to study the technology building blocks and critical issues associated with the design, development and operation of personal aerial vehicles. A number of multi-rotor configurations have been investigated providing basic guidelines for developing a stable unmanned aerial platform. The benefit of the presently selected configuration is highlighted and some preliminary testing results are presented.
First Principle Approach to Modeling of Primitive Quad Rotor
Sudiyanto, Tata ; Muljowidodo, Muljowidodo ; Budiyono, Agus ;
International Journal of Aeronautical and Space Sciences, volume 10, issue 2, 2009, Pages 148~160
DOI : 10.5139/IJASS.2009.10.2.148
By the development of recent technology, a new variant of rotorcrafts having four rotors start drawing attention from aerial-robotics engineers more than before. Its potential spans from just being control device test bed to performing difficult task such as carrying surveillance device to unreachable places. In this regards, modeling a quad-rotor is significant in analyzing its dynamic behavior and in synthesizing control system for such a vehicle. This paper summarizes the modeling of a mini quad-rotor aerial vehicle. A first principle approach is considered for deriving the model based on Euler-Newton equations of motion. The result of the modeling is a simulation platform that is expected to acceptably predict the dynamic behavior of the quad-rotor in various flight conditions. Linear models associated with different flight condition can be extracted for the purpose of control synthesis.