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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 12, Issue 4 - Dec 2011
Volume 12, Issue 3 - Sep 2011
Volume 12, Issue 2 - Jun 2011
Volume 12, Issue 1 - Mar 2011
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Research Advances on Tension Buckling Behaviour of Aerospace Structures: A Review
Datta, Prosun Kumar ; Biswas, Sauvik ;
International Journal of Aeronautical and Space Sciences, volume 12, issue 1, 2011, Pages 1~15
DOI : 10.5139/IJASS.2011.12.1.1
This paper reviews most of the research done in the field of tensile buckling characteristics pertaining to aerospace structural elements with special attention to local buckling and parametric excitation due to periodic loading on plate and shell elements. The concepts of buckling in aerospace structures appear as the result of the application of a global compressive applied load or shear load. A less usual situation is the case, in which a global tensile stress creates buckling instability and the formation of complex spatial buckling pattern. In contrast to the case of a pure compression or shear load, here the applied macroscopic load has no compressive component and is thus globally stabilizing. The instability stems from a local compressive stress induced by the presence of a defect, such as a crack or a hole, due to partial or non-uniform applied load at the far end. This is referred to as tensile buckling. This paper discusses all aspects of tensile buckling, theoretical and experimental. Its far reaching applications causing local instability in aerospace structural components are discussed. The important effects on dynamic stability behaviour under locally induced periodic compression have been identified and influences of various parameters are discussed. Experimental results on simple and combination resonance characteristics on plate structures due to tensile buckling effects are elaborated.
Nonlinear Model Predictive Control for Multiple UAVs Formation Using Passive Sensing
Shin, Hyo-Sang ; Thak, Min-Jea ; Kim, Hyoun-Jin ;
International Journal of Aeronautical and Space Sciences, volume 12, issue 1, 2011, Pages 16~23
DOI : 10.5139/IJASS.2011.12.1.16
In this paper, nonlinear model predictive control (NMPC) is addressed to develop formation guidance for multiple unmanned aerial vehicles. An NMPC algorithm predicts the behavior of a system over a receding time horizon, and the NMPC generates the optimal control commands for the horizon. The first input command is, then, applied to the system and this procedure repeats at each time step. The input constraint and state constraint for formation flight and inter-collision avoidance are considered in the proposed NMPC framework. The performance of NMPC for formation guidance critically degrades when there exists a communication failure. In order to address this problem, the modified optimal guidance law using only line-of-sight, relative distance, and own motion information is presented. If this information can be measured or estimated, the proposed formation guidance is sustainable with the communication failure. The performance of this approach is validated by numerical simulations.
Vision-Based Relative State Estimation Using the Unscented Kalman Filter
Lee, Dae-Ro ; Pernicka, Henry ;
International Journal of Aeronautical and Space Sciences, volume 12, issue 1, 2011, Pages 24~36
DOI : 10.5139/IJASS.2011.12.1.24
A new approach for spacecraft absolute attitude estimation based on the unscented Kalman filter (UKF) is extended to relative attitude estimation and navigation. This approach for nonlinear systems has faster convergence than the approach based on the standard extended Kalman filter (EKF) even with inaccurate initial conditions in attitude estimation and navigation problems. The filter formulation employs measurements obtained from a vision sensor to provide multiple line(-) of(-) sight vectors from the spacecraft to another spacecraft. The line-of-sight measurements are coupled with gyro measurements and dynamic models in an UKF to determine relative attitude, position and gyro biases. A vector of generalized Rodrigues parameters is used to represent the local error-quaternion between two spacecraft. A multiplicative quaternion-error approach is derived from the local error-quaternion, which guarantees the maintenance of quaternion unit constraint in the filter. The scenario for bounded relative motion is selected to verify this extended application of the UKF. Simulation results show that the UKF is more robust than the EKF under realistic initial attitude and navigation error conditions.
An Extended Scalar Adaptive Filter for Mitigating Sudden Abnormal Signals of Guided Missile
Lim, Jun-Kyu ; Park, Chan-Gook ;
International Journal of Aeronautical and Space Sciences, volume 12, issue 1, 2011, Pages 37~42
DOI : 10.5139/IJASS.2011.12.1.37
An extended scalar adaptive filter for guided missiles using a global positioning system receiver is presented. A conventional scalar adaptive filter is adequate filter for eliminating sudden abnormal jumping measurements. However, if missile or vehicle velocities have variation, the conventional filter cannot eliminate abnormal measurements. The proposed filter utilizes an acceleration term, which is an improvement not used in previous conventional scalar adaptive filters. The proposed filter continuously estimates noise measurement variance, velocity error variance and acceleration error variance. For estimating the three variances, an innovation method was used in combination with the least square method for the three variances. Results from the simulations indicated that the proposed filter exhibited better position accuracy than the conventional scalar adaptive filter.
Integrated System for Autonomous Proximity Operations and Docking
Lee, Dae-Ro ; Pernicka, Henry ;
International Journal of Aeronautical and Space Sciences, volume 12, issue 1, 2011, Pages 43~56
DOI : 10.5139/IJASS.2011.12.1.43
An integrated system composed of guidance, navigation and control (GNC) system for autonomous proximity operations and the docking of two spacecraft was developed. The position maneuvers were determined through the integration of the state-dependent Riccati equation formulated from nonlinear relative motion dynamics and relative navigation using rendezvous laser vision (Lidar) and a vision sensor system. In the vision sensor system, a switch between sensors was made along the approach phase in order to provide continuously effective navigation. As an extension of the rendezvous laser vision system, an automated terminal guidance scheme based on the Clohessy-Wiltshire state transition matrix was used to formulate a "V-bar hopping approach" reference trajectory. A proximity operations strategy was then adapted from the approach strategy used with the automated transfer vehicle. The attitude maneuvers, determined from a linear quadratic Gaussian-type control including quaternion based attitude estimation using star trackers or a vision sensor system, provided precise attitude control and robustness under uncertainties in the moments of inertia and external disturbances. These functions were then integrated into an autonomous GNC system that can perform proximity operations and meet all conditions for successful docking. A six-degree of freedom simulation was used to demonstrate the effectiveness of the integrated system.
Experimental Study on Simplex Swirl Injector Dynamics with Varying Geometry
Chung, Yun-Jae ; Khil, Tae-Ock ; Yoon, Jung-Soo ; Yoon, Young-Bin ; Bazarov, V. ;
International Journal of Aeronautical and Space Sciences, volume 12, issue 1, 2011, Pages 57~62
DOI : 10.5139/IJASS.2011.12.1.57
The effects of swirl chamber`s diameter and length on injector`s dynamic characteristics were investigated through an experimental study. A mechanical pulsator was installed in front of the manifold of a swirl injector which produces pressure oscillations in the feed line. Pressure in the manifold, liquid film thickness in the orifice and the pressure in the orifice were measured in order to understand the dynamic characteristic of the simplex swirl injector with varying geometry. A direct pressure measuring method (DPMM) was used to calculate the axial velocity of the propellant in the orifice and the mass flow rate through the orifice. These measured and calculated values were analyzed to observe the amplitude and phase differences between the input value in the manifold and the output values in the orifice. As a result, a phase-amplitude diagram was obtained which exhibits the injector`s response to certain pressure fluctuation inputs. The mass flow rate was calculated by the DPMM and measured directly through the actual injection. The effect of mean manifold pressure change was insignificant with the frequency range of manifold pressure oscillation used in this experiment. Mass flow rate was measured with the variation of injector`s geometries and amplitude of the mass flow rate was observed with geometry and pulsation frequency variation. It was confirmed that the swirl chamber diameter and length affect an injector`s dynamic characteristics. Furthermore, the direction of geometry change for achieving dynamic stability in the injector was suggested.
Unsteady Subsonic Aerodynamic Characteristics of Wing in Fold Motion
Jung, Yoo-Yeon ; Kim, Ji-Hwan ;
International Journal of Aeronautical and Space Sciences, volume 12, issue 1, 2011, Pages 63~68
DOI : 10.5139/IJASS.2011.12.1.63
Aerodynamic characteristics of a wing during fold motion were investigated in order to understand how variations or changes in such characteristics increase aircraft performance. Numerical simulations were conducted, and the results were obtained using the unsteady vortex lattice method to estimate the lift, drag and the moment coefficient in subsonic flow during fold motion. Parameters such as the fold angle and the fold angular velocity were summarized in detail. Generally, the lift and pitching moment coefficients decreased as the angle increased. In contrast, the coefficients increased as the angular velocity increased.
Development of a Peristaltic Micropump with Lightweight Piezo-Composite Actuator Membrane Valves
Pham, My ; Goo, Nam-Seo ;
International Journal of Aeronautical and Space Sciences, volume 12, issue 1, 2011, Pages 69~77
DOI : 10.5139/IJASS.2011.12.1.69
A peristaltic micropump with lightweight piezo-composite actuator (LIPCA) membrane valves is presented. The micropump contained three cylinder chambers that were connected by microchannels and two active membrane valves. A circular miniature LIPCA was developed and manufactured to be used as actuating diaphragms. The LIPCA diaphragm acted as an active membrane valve that alternate between open and closed positions at the inlet and outlet in order to produce high pumping pressure. In this LIPCA, a lead zirconium titanate ceramic with a thickness of 0.1 mm was used as an active layer. The results confirmed that the actuator produced a large out-of-plane deflection. During the design process, a coupled field analysis was conducted in order to predict the actuating behavior of the LIPCA diaphragm; the behavior of the actuator was investigated from both a theoretical and experimental perspective. The active membrane valve concept was introduced as a means for increasing pumping pressure, and microelectromechanical system techniques were used to fabricate the peristaltic micropump. The pumping performance was analyzed experimentally in terms of the flow rate, pumping pressure and power consumption.
Application of an Adaptive Autopilot Design and Stability Analysis to an Anti-Ship Missile
Han, Kwang-Ho ; Sung, Jae-Min ; Kim, Byoung-Soo ;
International Journal of Aeronautical and Space Sciences, volume 12, issue 1, 2011, Pages 78~83
DOI : 10.5139/IJASS.2011.12.1.78
Traditional autopilot design requires an accurate aerodynamic model and relies on a gain schedule to account for system nonlinearities. This paper presents the control architecture applied to a dynamic model inversion at a single flight condition with an on-line neural network (NN) in order to regulate errors caused by approximate inversion. This eliminates the need for an extensive design process and accurate aerodynamic data. The simulation results using a developed full nonlinear 6 degree of freedom model are presented. This paper also presents the stability evaluation for control systems to which NNs were applied. Although feedback can accommodate uncertainty to meet system performance specifications, uncertainty can also affect the stability of the control system. The importance of robustness has long been recognized and stability margins were developed to quantify it. However, the traditional stability margin techniques based on linear control theory can not be applied to control systems upon which a representative non-linear control method, such as NNs, has been applied. This paper presents an alternative stability margin technique for NNs applied to control systems based on the system responses to an inserted gain multiplier or time delay element.
Structural Analysis of a Composite Target-drone
Park, Yong-Bin ; Nguyen, Khanh-Hung ; Kweon, Jin-Hwe ; Choi, Jin-Ho ; Han, Jong-Su ;
International Journal of Aeronautical and Space Sciences, volume 12, issue 1, 2011, Pages 84~91
DOI : 10.5139/IJASS.2011.12.1.84
A finite element analysis for the wing and landing gear of a composite target-drone air vehicle was performed. For the wing analysis, two load cases were considered: a 5g symmetric pull-up and a -1.5g symmetric push-over. For the landing gear analysis, a sinking velocity of 1.4 m/s at a 2g level landing condition was taken into account. MSC/NASTRAN and LS-DYNA were utilized for the static and dynamic analyses, respectively. Finite element results were verified by the static test of a prototype wing under a 6g symmetric pull-up condition. The test showed a 17% larger wing tip deflection than the finite element analysis. This difference is believed to come from the material and geometrical imperfections incurred during the manufacturing process.