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김유단,이태영,안재명 서울대학교 항공우주신기술연구소 2000 항공우주신기술연구소 연구보고 Vol.1 No.1
Missile trajectory optimization is performed to obtain the optimal intercept trajectories against a descending target. The missile is assumed to be a point mass moving in three dimensional space, and thrust, gravity and aerodynamic forces are assumed to dominate the forces acting on it. Burnout velocity is considered as the performance index, inequality constraints on the control variables are considered, and inequality constraints on the dynamic pressure multiplied by the angle of attack is also considered to guarantee structural safety. The direct method is used to solve this problem, and only the control variables are parameterized. When the pre-computed optimal input is implemented, the missile may deviate from the pre-computed optimal trajectory due to external disturbances as well as internal uncertainties. To compensate for these effects, a real time trajectory optimization algorithm is proposed. ※ This paper has been presented at JSASS 13th International Sessions in 37th Aircraft Symposium which has held at Tokyo on October 13-15, 1999.
Seungho Yoon,Youdan Kim,Sanghyuk Park 한국항공우주학회 2012 International Journal of Aeronautical and Space Sc Vol.13 No.1
An adaptive backstepping controller is designed for the automatic landing of a fixed-wing aircraft. The backstepping control scheme is adopted by using the nonlinear six degree-of-freedom dynamics of the aircraft during the landing phase. The adaptive law is integrated along with the backstepping controller in order to estimate the aircraft modeling errors as well as the external disturbance. The dynamic constraints of the states and the actuator inputs are taken into account in the parameter adaptation. This is done to prevent an aggressive adaptation and to provide reliable control commands. Numerical simulations were performed to verify the performance of the proposed control law for the landing of the aircraft with the presence of gust and actuator stuck.
Distributed Unmanned Aircraft Collision Avoidance Using Limit Cycle
Yongwoo Lee,Youdan Kim 제어로봇시스템학회 2011 제어로봇시스템학회 국제학술대회 논문집 Vol.2011 No.10
This paper presents a guidance algorithm for the distributed collision avoidance of multiple unmanned aircraft based on a limit cycle generated around the collision threat. Distributed collision avoidance, on which individual aircraft detects a collision threat and solves it without any explicit communication with the other aircrafts, among multiple unmanned aircraft is performed using the geometric and kinematic information of the existing aircrafts in a discoverable range. The algorithm analyzes the given information by deriving properties such as line-of-sight(LOS) vector, the closest point of approach(CPA), then figures out a collision threat if exists. A limit cycle, which plays a role of a guidance vector field and actually guides the aircraft to maintain predescribed safety radius between the threat and the aircraft, is applied to a stationary and moving obstacles to provide consecutive flight path angles. By doing this, the algorithm eventually guides the aircraft to a collision-free route to accomplish the goal of the given missions. All of these procedures should be processed independently in real-time. Several scenarios are considered for numerical simulations, and the simulaton results demonstrate the effectiveness of the collision avoidance performance and behavioral characteristics of the guidance algorithm. Finally, issues including effectiveness and feasibility of the proposed algorithm are addressed.
Flight Envelope Protection Controller using Dynamic Trim Algorithm
Hohyun Shin,Youdan Kim,Eung Tae Kim,Ki Jung Seong 제어로봇시스템학회 2009 제어로봇시스템학회 국제학술대회 논문집 Vol.2009 No.8
This paper deals with a flight envelope protection control scheme. The objective of the flight envelope protection controller is to prevent the pilot or flight control system from making control inputs that would force the aircraft get out of the flight envelope. The main contribution of this paper is to modify the dynamic trim algorithm using the 1<SUP>st</SUP> order differential term. To verify the performance of the proposed controller, numerical simulations are performed for the velocity restriction of non-linear aircraft model.
Youkyung Hong,Youdan Kim 한국항공우주학회 2012 International Journal of Aeronautical and Space Sc Vol.13 No.1
In this paper, the Integrated Guidance and Control (IGC) law is proposed for the Rotary Unmanned Aerial Vehicle (RUAV). The objective of the IGC law is to consider the nonlinear dynamic characteristics of the RUAV and to design a guidance law which takes into consideration the nonlinear relationship between kinematics and dynamics. In order to control the RUAV system, sliding mode control scheme is adopted. As the RUAV is an under-actuated system, a slack variable approach is used to generate the available control inputs. Through the Lyapunov stability theorem, the stability of the proposed IGC law is proved. In order to verify the performance of the IGC law, numerical simulations are performed for waypoint tracking missions.
Mingu Kim,Youdan Kim 한국항공우주학회 2013 International Journal of Aeronautical and Space Sc Vol.14 No.1
Nonlinear guidance law combined with a pseudo pursuit guidance is proposed, to perform stationary target observation mission. Multiple UAVs are considered, with waypoint constraint. The whole guidance is divided into two steps: firstly, waypoint approach, with specified incidence angle; and secondly, loitering around the stationary target. Geometric approach is used to consider the constraint on the waypoint, and a specified phase angle between the loitering UAV and the approaching UAV. In the waypoint approach step, UAVs fly to the waypoint using the pseudo pursuit guidance law. After passing the waypoint, UAVs turn around the target, using a distance error dynamics-based guidance law. Numerical simulations are performed, to verify the performance of the proposed guidance law.
Collision avoidance for quadrotor using stereo vision depth maps
Jongho Park,Youdan Kim IEEE 2015 IEEE transactions on aerospace and electronic syst Vol.51 No.4
<P>A collision avoidance algorithm for a quadrotor unmanned aerial vehicle using a stereo vision sensor is proposed. A mathematical model for the quadrotor is developed, and the underactuated problem of the quadrotor is treated by introducing virtual inputs. Stereo vision is used to obtain depth map information, which is used to detect an obstacle. The collision cone approach is adopted to avoid collisions between the quadrotor and the detected obstacle. The collision prediction is conducted by using the relation between the velocity vector of the quadrotor and the collision cone. Information of the detected obstacles is accumulated to determine the location and size of the obstacles, which is used to prevent the quadrotor from colliding with the obstacle. Multiple obstacles can also be managed by creating obstacle clusters in the image plane. A waypoint guidance law and controller are designed using a feedback linearization scheme and a linear quadratic tracker. Numerical simulations are performed to demonstrate the performance of the proposed algorithm.</P>