Planning a path to improve the performance of target localization usually requires significant computational load, so localization cannot be implemented in real time. In this study, guidance laws ...using vector fields, which can be implemented in real time with suboptimum performance, are introduced for a low-cost unmanned aircraft equipped with a bearing-only sensor. The proposed guidance laws using vector fields are simple, and the Fisher information matrix and optimization tools are combined to construct the necessary vector fields. Therefore, only a little information and limited computational load are required when an unmanned aircraft is steered by the proposed guidance laws.
A group of agents can form a flock using the augmented Cucker-Smale (C-S) model. The model autonomously aligns them to a common velocity and maintains a relative distance among the agents in a ...distributed manner by sharing the information among neighbors. This paper introduces the concept of inactiveness to the augmented C-S model for improving the flocking performance. It involves controlling the energy and convergence time required to form a stable flock. Inspired by the natural world where a few lazy (or inactive) workers are helpful to the group performance in social insect colonies. In this study, we analyzed different levels of inactiveness as a degree of control input effectiveness for multiple fixed-wing UAVs in the flocking algorithm. To find the appropriate inactiveness level for each flock member, the particle swarm optimization-based approach is used as the first step, based on the initial condition of the flock. However, as the significant computational burden may cause difficulties in implementing the optimization-based approach in real time, we also propose a heuristic adaptive inactiveness approach, which changes the inactivity level of selected agents adaptively according to their position and heading relative to the flock center. The performance of the proposed approaches using the concept of lazy (or inactive) agents is verified with numerical simulations by comparing them with the conventional flocking algorithm in various scenarios.
This paper proposes a formation control algorithm to create separated multiple formations for an undirected networked multi-agent system while preserving the network connectivity and avoiding ...collision among agents. Through the modified multi-consensus technique, the proposed algorithm can simultaneously divide a group of multiple agents into any arbitrary number of desired formations in a decentralized manner. Furthermore, the agents assigned to each formation group can be easily reallocated to other formation groups without network topological constraints as long as the entire network is initially connected; an operator can freely partition agents even if there is no spanning tree within each subgroup. Besides, the system can avoid collision without loosing the connectivity even during the transient period of formation by applying the existing potential function based on the network connectivity estimation. If the estimation is correct, the potential function not only guarantees the connectivity maintenance but also allows some extra edges to be broken if the network remains connected. Numerical simulations are performed to verify the feasibility and performance of the proposed multi-subgroup formation control.
This paper presents a distributed swarm system for small fixed-wing unmanned aerial vehicles (UAVs). In particular, to perform various missions with multiple UAVs that are densely gathered and ...collision free, a hybrid-flocking control algorithm is synthesized by using three types of control protocols: vector field guidance (for path following/loitering), augmented Cucker–Smale (ACS) model (for collective flocking behavior), and potential field (for collision avoidance). In particular, to address the issue of conflicts between different control protocols, the adaptive ACS model is proposed and the optimization problem is formulated to determine the suitable mixing weights of control protocols. We also design the transition of multiple operation modes and communication architecture for the swarm system. The system is evaluated using the proposed hybrid-flocking control algorithm by proof-of-concept real flight experiments using 18 small fixed-wing UAVs as well as extensive numerical simulations. Flight experiments are successfully performed for multiple consecutive tasks including the individual task, circular path loitering and elliptical path loitering while avoiding collisions among UAVs.
•The distributed small fixed-wing UAV swarm system is designed.•The hybrid-flocking control algorithm is proposed by combining three control protocols.•The optimal mixing weight improves the mission performance.•Numerical simulations and flight experiments validate the hybrid-flocking algorithm.
This paper focuses on unmanned aircraft guidance laws for a straight path and a circular orbit following using the vector field approach. The vector fields introduced in this paper can be applied to ...not only path following, but also other purposes such as arrival position, angle, and time control. Therefore, they could be applied to various missions providing advantages over other previous vector fields. Stability and performance of the path following has been proved and analyzed using the classical control theory. Simulation using a six degrees-of-freedom aircraft model shows that these guidance laws are effective for the missions even under the existence of wind disturbance. Furthermore, flight experiments with a blended-wing-body type unmanned aircraft are performed to evaluate the proposed vector field guidance algorithm.
This paper presents strategies for standoff target tracking by a team of unmanned aircrafts using vector field. Many methods to the vector field approach were investigated in other papers, but a ...modified vector field is introduced to obtain new interesting characteristics in this paper. The modified vector field satisfies more constraints. We introduce two guidance modes to track a target: one is a capturing mode and the other one is a loitering mode. In the capturing mode, aircrafts can arrive at desired positions and time, i.e., unmanned aircrafts can capture a target simultaneously from all sides. After a target is captured, the guidance mode is changed to the loitering mode. Then the relative spacing among aircrafts is controlled by a standoff distance command and a speed command. Hence, they track a target with a desired formation.
This paper elaborates on the directional axis guidance and control algorithm used in mission flight for high altitude long endurance UAV. First, the directional axis control algorithm is designed to ...modify the control variable such that a strong headwind prevents the UAV from moving forward. Similarly, the guidance algorithm is designed to operate the respective algorithms for Fly-over, Fly-by, and Hold for way-point flight. The design outcomes of each guidance and control algorithm were confirmed through nonlinear simulation of high altitude long endurance UAV. Finally, the penultimate purpose of this study was to perform an actual mission flight based on the design results. Consequently, flight tests were used to establish the flight controllability of the designed guidance and control algorithm. 본 논문에서는 고고도 장기체공 무인항공기의 임무 비행을 위한 방향축 유도, 제어 알고리즘에 대해 기술 하였다. 먼저 방향축 제어 알고리즘은 임무 기간 중 무인항공기가 전진비행을 할 수 없을 맞바람에 대해 제어 변수를 전환하는 알고리즘을 설계하였다. 유도법칙은 항로점 비행을 위해 Fly-over, Fly-by, Hold 속성에 대한 각각의 알고리즘을 적용하였다. 무인항공기의 비선형 시뮬레이션을 통해 각 유도, 제어 알고리즘의 설계 결과를 확인하였다. 본 연구는 설계 결과를 토대로 실제 임무 비행을 수행하는 것을 목적으로 한다. 따라서 본 연구 내용을 기반으로 비행 시험을 통해 설계한 유도 제어 알고리즘의 비행 운용성을 확인하였다.
This paper focuses on unmanned aircraft guidance laws for a straight path and a circular orbit following using the vector field approach. The vector fields introduced in this paper can be applied to ...not only path following, but also other purposes such as arrival position, angle, and time control. Therefore, they could be applied to various missions providing advantages over other previous vector fields. Stability and performance of the path following has been proved and analyzed using the classical control theory. And simulation using a six degrees-of-freedom aircraft model shows that these guidance laws are effective for the missions even under the existence of wind disturbance.
Many guidance laws for UAVs focus on path following. And trajectory tracking problem is enough when it satisfies path and time constrains. One more constraint will be considered in this research, ...that is, approaching direction to a terminal position. Two methods will be introduced; they are based on Pythagorean-Hodograph curve, and the Lyapunov vector field, respectively. The first algorithm consists of two steps. The first step is trajectory-planning using PH curve, and the second step is tracking algorithm for that curve. The second algorithm is based on vector field including a variable parameter. Using this parameter, contraction vectors toward the origin are tuned, and a desired terminal approaching condition is achieved.
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