Seungkeun Kim

Optimum design of three-dimensional behavioural decentralized controller for UAV formation flight

This article proposes a behavioural decentralized approach that allows an unmanned aerial vehicle (UAV) formation flight to carry out a waypoint-passing mission effectively. The objective of the proposed controller is to make each UAV in the formation fly through predefined waypoints while maintaining its distance from other UAVs. To perform these two tasks, which can conflict with each other, coupled dynamics of UAVs is considered; this combines the dynamics of all the members in the formation. To apply the behavioural decentralized controller on the basis of the coupled dynamics, a feedback linearization technique with a diffeomorphic transfer map is derived for a three-dimensional UAV kinematics model. A behavioural approach in which the control input is decided by the relative weight of each UAVs desired behaviour is considered, so that the UAVs can react promptly in various situations. Optimization techniques of the gain matrices are also performed to improve the performance of the formation flight using eigen-structure analysis and Cholesky decomposition. To verify the performance of the proposed controller, numerical simulation is performed for a waypoint-passing mission of multiple UAVs.

Consensus-based reconfigurable controller design for unmanned aerial vehicle formation flight

This article presents a distributed controller design methodology with a failure detection logic for formation flight of unmanned aerial vehicles (UAVs). An output feedback linearization method with a consensus protocol is used to maintain a specified time-varying geometric configuration of multiple UAVs. In this approach, any explicit leader does not exist in the team, and the control strategy requires only the local neighbour-to-neighbour information between the vehicles. A graph Laplacian matrix is used to define the information flow topologies between the vehicles. The Failure detection algorithm is also proposed in order to detect a communication loss or an aircraft system fault and to isolate the failed one. The detection logic proposed in this study considers the case in which one of the vehicles totally broke down. Once the failure is detected, the failed vehicle is isolated. Reforming the interconnection topology using the failure detection logic can guarantee the stable formation flight with the proposed controller. Numerical simulations are performed to validate the performance of the proposed controller with which the formation geometry is dynamically reconfigured using failure detection information.

Dubins Path Planning of Multiple Unmanned Airborne Vehicles for Communication Relay

This article investigates the path planning strategy of a swarm of unmanned airborne vehicles (UAVs) with the aim of guaranteeing the communication relay between a ground control station and a friendly fleet. A decision-making algorithm mainly relies on waypoint generations and path planning based on Dubins theory and deals with dynamic and strategic constraints such as maximum speed, minimum curvature radius, and no fly zones arising from the mission operative scenario. The example simulations concerning a baseline scenario with a swarm of three UAVs are done to verify the feasibility of the proposed path planning algorithm.

Airborne monitoring of ground traffic behaviour for hidden threat assessment

This paper focuses on development of behaviour recognition technique for airborne monitoring of ground traffic to detect hidden threats. To enhance tracking accuracy, sensor fusion and smoothing are applied with Kalman filter. To tackle behaviour recognition, trajectory approximation and classification methodology is proposed using differential geometric quantities and string matching. Simulation on a ground vehicle is done to verify the feasibility of the proposed algorithms.

Flight test of a Flying-Wing Type UAV with Partial Wing Loss Using Neural Network Controller

This paper presents flight test result of flying-wing type UAV with partial wing loss using neural network controller. 22% and 33% loss of wing area moment were considered for the damage configuration. A new trim state was obtained for each damaged model with the variation of mass, center of gravity and moment of inertia. A numerical simulation was performed to investigate the changed flight dynamics. It is verified that the damaged UAV shows sluggish roll behavior with unstable longitudinal response. A neural network based adaptive controller combined with feedback linearization was designed in order to compensate for the partial damage. It is verified that the instability caused by partial wing damage can be effectively controlled, and the overall system can be stabilized via neural network controller.

Design of a Track Guidance Algorithm for Formation Flight of UAVs

Precise flight path tracking capability is generally required to carry out complex missions for high performance of Unmanned Aerial Vehicles (UAVs). Accurate waypoint navigation is a key feature that these UAVs usually have. This paper presents a track guidance algorithm for the waypoint navigation of multiple UAVs. In order to minimize the track error between pre-assigned flight path and the position of a single vehicle, it’s heading or yaw rate of the vehicle is guided to direct a certain distance ahead on the flight path. The suggested guidance algorithm is a spatial version of the first order dynamic characteristics for a time-dependent system. An invariant tracking performance is guaranteed in a spatial domain so that a constant flight trajectory pattern is obtained without regard to a speed of the vehicle. Additionally, a modified track guidance algorithm is executed for a formation flight of the UAVs. A crucial design parameter is a spatial constant that controls the shape of the convergence to an assigned flight path. Reference flight trajectories are designed based on a two-dimensional vehicle model, and the proposed algorithm is verified by numerical simulation using rigid body UAV dynamics with MATLAB/Simulink Aerosim Blockset.

Cooperative Tracking of a Moving Target using Integrated Vector Field and Decentralized Extended Information Filter

Abstract This paper presents the decentralized target localization and control design for multiple unmanned aircraft to track a moving target. The extended information filter is applied to estimate the position and velocity of the target with additional target information provided by neighbor aircraft. The heading vector field considering both the distance error to the target and the phase spacing error between aircraft is proposed to track the fast target which changes its direction rapidly. Numerical simulation is performed to verify the proposed estimation and tracking scheme using four unmanned aircraft.

Coordinated Trajectory Planning for Efficient Communication Relay Using Multiple UAVs

Abstract This paper investigates the use of small UAVs as communication relay nodes for expanding communications links and improving communication quality, primarily for a fleet of ground or navy vessels. An airborne relay in ground/maritime space can effectively connect to units operating over the horizon, beyond normal communication range, or under limited satellite communication environments. For efficient UAV communication relay, this paper firstly deals with the UAV deployment for stationary communication nodes, which finds the fixed optimal location of UAVs to improve the connectivity of a wireless network. Then, considering movements of vessels and constraints of the fixed-wing UAV in a dynamic environment, this paper proposes a decentralised nonlinear model predictive trajectory planning strategy. By exploiting motion estimates of vessels and states of UAVs, the trajectory planning algorithm finds a control input sequence over a certain time horizon, which optimises network connectivity. Numerical simulations are performed with different number of UAVs for both stationary and manoeuvring naval vessels to verify the feasibility and benefit of the proposed approach.

System Design and Dynamic Analysis for Sail Deployment for Cube Satellite CNUSAIL-1

The CNUSAIL-1, which is currently being developed at the Chungnam National University, is a 3U-size cube satellite with four-square-meter sized small sail. The purpose of the CNUSAIL-1 is to deploy the sail and check its eect on satellite orbit and attitude in LEO and to perform de-orbiting using the sail membranes as a drag-sail at the nal phase. The deployment system consists of quadrant sail membranes, four steel booms, and a spiral torsional spring. Kapton sheet sith a thickness of 0.25 m is selected as the sail membranes, and C-shaped steel booms are used to support the membranes. The 0.5U sized deployer is designed with a middle spindle and four guides to help the booms spread smoothly. The design and mechanism of the CNUSAIL-1 deployment system is introduced, and its performance is veried through ground test in a low-friction environment. Additionally, the eect of the sail deployment on attitude dynamics is analyzed via numerical simulations and ground experients by taking into account boom ejection speed, the moment of the torsional spring, and the time-dependent change of moment of inertia.