• Journal of Advanced Navigation Technology
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• v.22 no.6
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• pp.537-544
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• 2018

A national comprehensive aviation test center is being constructed for the purpose of flight tests for development and modification of aircraft or flight inspections for the development of navaids. Flight testing is a high-risk task, so strict risk management processes are required prior to operation. In addition, since the flight test center is subject to the airdrome regulations under the current law, the introduction of the safety management system will enhance safety as usual in ordinary airports. The establishment of a safety management system based on ICAO criteria is an optimal means of ensuring safe and effective operation of the test center and may mitigate the risks that may arise during flight testing. This paper focuses on risk assessment and mitigation required for safety management at the flight test center. We conducted risk assessments on the flight hazards identified in the previous study. Then the high risk group of hazards were selected and risk mitigation techniques such as avoidance, reduction, acceptance, and control were applied.

• International Journal of Aeronautical and Space Sciences
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• v.11 no.2
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• pp.131-135
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• 2010

We report on the design of a three-axis missile autopilot using multi-objective control synthesis via linear matrix inequality techniques. This autopilot design guarantees $H_2/H_{\infty}$ performance criteria for a set of finite linear models. These models are linearized at different aerodynamic roll angle conditions over the flight envelope to capture uncertainties that occur in the high-angle-of-attack regime. Simulation results are presented for different aerodynamic roll angle variations and show that the performance of the controller is very satisfactory.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2003.10a
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• pp.95-98
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• 2003

The physics of the plume-induced shock and separation particulary at a high plume to exit pressure ratio and supersonic speeds up to Mach 3.0 with aid without a passive control method, porous extension, were studied using computational techniques. Mass-averaged Navier-Stokes equations with the RNG k-$\varepsilon$ turbulence model were solved using a fully implicit finite volume scheme and a 4-stage Runge-Kutta method. The courol methodology for plume-afterbody interactions is to use a perforated wall attached at either the nozzle exit or the edge of the missile base. The Effect of porous wall length on plume interference is also investigated. The computational results show the main effect of the porous extension on plume-afterbody interactions is to in the plume from strongly underexpanding during a change in flight conditions. With control, a change in porous extension length has no significant effect on plume interference.

• Journal of Advanced Navigation Technology
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• v.21 no.3
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• pp.264-271
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• 2017

This paper presents air traffic control simulation model for generating 4D trajectory, and aircraft dynamic model based on 4D trajectory information. With aircraft parameters from BADA and Total Energy Model, the trajectory is defined through modified Bezier curve and the simulation supports two aircraft control methods based on controlled time of arrival (CTA) or airspeed. The simulation results shown that flight time and path were almost identical to the defined trajectory, and derived the differences of each control methods according to wind conditions. Based on the simulation model developed in this study, it is expected to be applied to various air traffic management researches. Future studies will focus on applying optimization techniques in order to minimize the difference between generated trajectories and actual flight routes. This work will increase utilization of developed simulation futhermore.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.38 no.2
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• pp.137-148
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• 2014

A multi-rotor is an autonomous flying robot with multiple rotors. Depending on the number of the rotors, multi-rotors are categorized as tri-, quad-, hexa-, and octo-rotor. Given their rapid maneuverability and vertical take-off and landing capabilities, multi-rotors can be used in various applications such as surveillance and reconnaissance in hostile urban areas surrounded by high-rise buildings. In this paper, the unified dynamic model of each tri-, quad-, hexa-, and octo-rotor are presented. Then, based on derived mathematical equations, the operation and control techniques of each multi-rotor are derived and analyzed. For verifying and validating the proposed models, operation and control technique simulations are carried out.

• Journal of Satellite, Information and Communications
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• v.10 no.2
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• pp.115-120
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• 2015

Until now, AOCS SW has used FPU which is one of CPU resources for satellite attitude control. And most of the SW Throughput was consumed to calculate Matrix Multiply. As SW throughput margin is decreasing seriously with shorter control period and more computational burden at next satellite programs, a dedicated HW matrix multiplier is absolutely required. This paper represents results of HW implementation & performance measurement and mentions several techniques for performance improvement, further works.

• International Journal of Aeronautical and Space Sciences
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• v.12 no.1
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• pp.78-83
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• 2011

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.

• Aerospace Engineering and Technology
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• v.11 no.1
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• pp.158-168
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• 2012

This paper deals with TVC nozzle stroke verification test and corresponding analysis techniques related to kick motor TVC system of KSLV-I second stage. It is shown that the relationship between TVC stroke and potentiometer voltage is revealed via the open-loop stroke verification test, and other major operational parameters including nozzle alignment error, actuation error, neutral position, radius of nozzle rotation, location of nozzle rotation center, angle conversion coefficients, etc. are analyzed via the closed-loop stroke verification test. The TVC stroke verification test results for the first and second flight model of KSLV-I show that all TVC operational parameters of KSLV-I second stage were normally setup for the first and second flight tests.

• 한국전산유체공학회:학술대회논문집
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• 2011.05a
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• pp.465-468
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• 2011

Ice accretion on aircraft surface can greatly deteriorate the safety of aircraft. In particular, it can be a cause of impediment for aircraft performances such as aerodynamic characteristics, control, and engine. Numerical simulation of icing accretion based on the state-of-art CFD techniques can be alternative to expensive icing wind tunnel test or flight test. In this study, icing conditions are defined in order to predict the ice accretions around the air intake of aircraft. Then the range and amount of ice accretion on the intake in icing wind tunnel were investigated In addition, a study on the size effect of icing wind tunnel was conducted in order to check the compatibility with the real in-flight test environment.

• Journal of KIISE
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• v.44 no.6
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• pp.601-606
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• 2017

Recently, we have frequently encountered flying drones with the growth of drone industry. However, it is difficult for a driver to stabilize the motor speed of drones, since the voltage of a Lithium polymer battery used in drones may suddenly drop or rise when its power is exhausted. The instability of the motor speed precludes the drone from maintaining a flight altitude, so that the fuselage of a drone performs ascending and descending repeatedly. For solving this problem, existing techniques either add a compensator considering voltage drop of battery or change the control model. Since these techniques use hardware-implemented modules or depend on motor type and experimental results, there is a problem that new suitable modules should be implemented in accordance with the used motor of the fuselage. For solving this problem, in this paper, we implement a motor speed controller in the firmware of drones by considering voltage drop of battery to enhance drone flight stability.