• Journal of the Korea Institute of Military Science and Technology
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• v.11 no.3
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• pp.5-12
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• 2008

This paper presents the features of an impact angle constrained open-loop optimal trajectory which is given by a function of initial conditions and optimal guidance gains. Using missile motion described by linearized kinematic equations and a proper form of performance index, an inverse optimal problem is suggested to investigate the gains related to the performance index. The flight trajectory and time-to-go can be shaped in terms of the optimal guidance gains. The results are evaluated by 3-DOF simulation.

• Journal of Institute of Control, Robotics and Systems
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• v.15 no.1
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• pp.8-14
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• 2009

A formation flight guidance logic that enables the leader-follower station keeping between two UAVs is presented in this paper. The logic is motivated by the investigation of the relation between the proportional navigation and the nonlinear trajectory tracking guidance law, The simplicity of the presented method provides computational efficiency and allows easy implementation. An excellent performance of the proposed logic is demonstrated via various numerical simulations for multiple UAVs environment.

• Journal of Institute of Control, Robotics and Systems
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• v.8 no.7
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• pp.613-623
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• 2002

Ascent trajectory optimization and explicit guidance problems for a satellite launch vehicle with yaw maneuver in a 3-dimension are considered. The trajectory optimization problem with boundary conditions is formulated as a nonlinear programming problem by parameterizing the inertial pitch and yaw attitude control variables, and is solved by using the SQP algorithm. The flight constraints such as gravity-turn and range safety conditions are imposed. An explicit inertial guidance algorithm in the exoatmospheric phase is also presented. The guidance algorithm provides steering command and time-to-go value directly using the current states of the vehicle and the desired orbit insertion conditions. The liquid propelled Delta 2910 launch vehicle is used as a numerical model.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.37 no.11
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• pp.1104-1111
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• 2009

In the low altitude, mission of the aircraft is restricted by a variety of threats such as anti-air missiles and terrain obstacles. Especially, aircraft have always a risk of ground collision near terrain. In this study, to effectively solve this problem, we developed the flight path generation algorithm that is considered the terrain avoidance. In this flight path generation algorithm, waypoints that should be passed by the UAV are selected first. The waypoints are located in the middle of the terrain obstacles. Then, physically meaningful waypoints sets are classified by Dijkstra algorithm. The optimal waypoint guidance law based on the optimal control theory is applied to produce trajectory candidates. And finally the minimum control energy trajectory is determined.

• Journal of the Korean Society for Aviation and Aeronautics
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• v.30 no.1
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• pp.38-43
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• 2022

As the use of unmanned aerial vehicles increases, in order to expand the operability of the unmanned aerial vehicle, it is essential to develop an unmanned aerial vehicle traffic management system, and to establish the system, it is necessary to analyze the integrated navigation performance of the unmanned aerial vehicle to be operated. Integrated navigation performance is affected by various factors such as the type of unmanned aerial vehicle, flight environment, and guidance law algorithm. In addition, since a large amount of flight data is required to obtain high-reliability analysis results, efficient and consistent flight scenarios are required. In this paper, a flight scenario that satisfies the requirements for integrated navigation performance analysis of rotary and fixed-wing unmanned aerial vehicles was designed and verified through flight experiments.

• Journal of the Korea Institute of Military Science and Technology
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• v.16 no.6
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• pp.739-744
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• 2013

In this paper, we propose a method of generating pitch commands for consistent initial trajectories irrelevant to flight conditions in the initial boosting phase of a thrust-vector-controlled vehicle. After shape assumption of the pitch command profile, parameters of the profile are determined in real time in order for the summit height of the trajectory to be a desired value by deriving the summit height considering thrust performance, gravity, and other flight conditions. Computer simulation results demonstrate good performance of the proposed method.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.38 no.3
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• pp.213-220
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• 2010

This paper presents the analysis results of trajectory, performance and attitude control based on the first flight data of the KSLV-I. The KSLV-I had a fairing separation problem and failed to inject spacecraft into the orbit. In this paper, the trajectory, flight performance, and attitude control was analyzed considering the influence of unseparated fairing. Moreover, the flight results and performance of the inertial navigation and guidance system were presented. As a results of post-flight analysis, any other problem besides the fairing separation problem was not happened and onboard equipment functioned normally.

• Journal of the Korean Society for Precision Engineering
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• v.17 no.6
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• pp.111-118
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• 2000

The design of reference trajectory with respect to drag acceleration is necessary to decelerate from hypersonic speed safely after atmosphere re-entry of space vehicle. The re-entry guidance design involves trajectory optimization, generation of a reference drag acceleration profile with the satisfaction of 6 trajectory constraints during the re-entry flight. This reference drag acceleration profile can be considered as the reference trajectory. The cost function is composed of the accumulated total heating on vehicle due to the reduction of weight. And a regularization is needed to prevent optimal drag profile from varying too fast and achieve realized trajectory. This paper shows the relations between velocity, drag acceleration and altitude in drag acceleration profile, and how to determine the reference trajectory.

• Proceedings of the KIEE Conference
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• 1991.11a
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• pp.361-365
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• 1991

The problem being considered here is the determination of optimal guidance laws for a launch vehicle for scientific missions. The optimal guidance commands are determined in the sense that the least amount of fuel is used. A numerical solution was obtained for the case where the position and velocity state variables satisfy a specified constraint at the time of thrust cutoff. The method used here is based on the Pontryagin's maximum principle. This is the method of solving a problem in the calculus of variations. In particular, it applies to the problem considered here where the magnitude of the control is bounded. Simulations for the optimal guidance algorithm, during the 2nd and the 3rd-stage flight of the Japanese rocket M-3H-3, are carried out. The results show that the guided trajectory that satisfying the terminal constraints is optimal, and the guidance algorithm works well in the presence of some errors during the 1st-stage pre-programmed guidance phase.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.42 no.10
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• pp.842-850
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• 2014

This paper presents a trajectory tracking controller for rotorcraft UAVs to improve the tracking performances in the presence of various uncertainties. The proposed tracking method consists of a velocity guidance law based on the relative distance and L1 adaptive augmentation loop for tracking the velocity commands. In the proposed structure, the desired velocity generated by the guidance law is the reference value of the adaptive controller for accurate path tracking. In the guidance law, the desired acceleration is generated based on the relative distance and its derivatives, and then the velocity command of the inner control loop is calculated by integrating the accelerations. $L_1$ augmentation loop supplements the linear controller to guarantee the flight performances such as a tracking accuracy in the presence of the uncertainties. The proposed controller was validated in actual flight tests to successfully demonstrate its capability using a quadrotor UAV.