Time-varying Formation Control Protocol Research Articles

Observer-Based Bipartite Formation Control for MASs With External Disturbances Under Event-Triggered Scheme

This brief investigates the bipartite time-varying formation tracking control for multi-agent systems with cooperative-antagonistic interactions and external disturbances under event-triggered scheme. To deal with the external disturbances, an extended state observer is employed to illustrate the control protocol. Then, a time-varying formation control protocol is developed under event-triggered scheme to eliminate continuous communication, further reducing unnecessary computational cost successfully. Besides, Zeno behavior is verified to be excluded and convergence analysis of proposed protocol is demonstrated by the lights of Lyapunov stability theory. Finally, the effectiveness of the proposed protocol is indicated by a numerical simulation, where the agents realize two time-varying antagonistic sub-formations with disturbance rejection under event-triggered scheme.

Time-Varying Group Formation With Adaptive Control for Second-Order Multi-Agent Systems

In this paper, adaptive time-varying group formation control for second-order multi-agent systems with undirected topology is studied. Firstly, a conventional multi-group adaptive time-varying formation control protocol is presented, and the stability of the system is analyzed based on Lyapunov method. Then, the traditional method of dealing with nonlinear dynamics cannot be directly applied to time-varying formation problem, the parameter estimation method is used to track the unknown internal nonlinear dynamics of agent. Virtual leader and filter are introduced to solve the problem of variable derivation and repeated derivation of system state, and the adaptive rate of time-varying formation converges to a stable value. Finally, the feasibility of the results is verified by two simulation results.

Intermittent Time-Varying Formation Control for High-Order Networked Agents Subject to Discontinuous Communications

This paper investigates the leaderless and leader-follower time-varying formation design and analysis problems for a group of networked agents subject to discontinuous communications. Firstly, a leaderless time-varying formation control protocol is proposed via the intermittent control strategy, where the control input of each agent is constructed by the distributed local state information and formation instructions in the communication time unit, but it is zero in the noncommunication time unit. Then, an explicit formulation of the formation center function is determined to describe the formation movement trajectory of the whole networked agents. Leaderless time-varying formation design and analysis with discontinuous communications are given in the form of linear matrix inequalities. Moreover, the main results of the leaderless cases are extended to the leader-follower cases. Finally, two numerical examples are provided to illustrate the theoretical results of leaderless and leader-follower cases, respectively.

Distance- and Velocity-Based Collision Avoidance for Time-Varying Formation Control of Second-Order Multi-Agent Systems

This brief addresses the time-varying formation control problem with collision avoidance for second-order multi-agent systems. By taking both distances and velocities between agents into account, a novel collision avoidance scheme is proposed on the basis of conventional distance-based artificial potential field methods. Compared with the latter, the proposed scheme can more accurately determine possible collision situations and thus significantly reduce possible collision areas, which consequently not only can reduce energy consumption, but also has as few adverse effects on formation maintenance as possible. Then a time-varying formation control protocol is designed so as to achieve zero steady-state position and velocity formation tracking errors without collision. Finally, theoretical analysis, numerical demonstration, as well as comparative simulation are provided to verify the effectiveness of the proposed method.

Time-varying formation for linear multi-agent systems based on sampled data with multiple leaders

This paper investigates the time-varying formation problem of a linear multi-agent system (MAS) based on sampled data with multiple leaders. The leader group and the follower group form the MAS. Followers are driven to reach the time-varying formation where the center of the formation is the convex combination of the states of the leaders. First, a time-varying formation control protocol with sampled data is proposed, while communication among followers is only occurred at sampling instants, which reduces the waste of communication energy significantly. Second, sufficient conditions for the MAS achieving the desired time-varying formation under sampling with multiple leaders are derived. In the theoretical analysis, a Lyapunov function is constructed to derive sufficient conditions based on formation protocol with sampled data for the MAS reaching time-varying formation. In addition, under formation control with sampled data, the problems of time-varying formation of MAS with one leader and time-invariant formation of MAS with multiple leaders are the special cases of the problem discussed in this paper. Finally, one example is presented to demonstrate the obtained theoretical analysis.

Time-Varying Formation Control for Second-Order Discrete-Time Multi-Agent Systems With Directed Topology and Communication Delay

Time-varying formation control protocol design and analysis problems for the second-order discrete-time multi-agent systems with directed interaction topology and communication delay are investigated. A local information-based distributed protocol is designed by utilizing the delayed state information of neighbors. Through system decomposition and stability analysis, an explicit description of the feasible time-varying formation set is given. Necessary and sufficient conditions for the systems with the directed topology and communication delay to achieve time-varying formation are obtained, which are related to the topology of the interaction graph and the feasibility of the predefined formation. Necessary constraints on the gain parameters and the sampling period are proposed, so as to guide the design of parameters in the protocol. The numerical simulation results indicate that the protocol can steer the agents to accomplish the desired time-varying formation and effectively tolerate the relatively large bounded communication delay. Outdoor experiment with quadrotors is presented to demonstrate the effectiveness of the obtained theoretical results with one sampling period delay.

Event-triggered time-varying formation control for general linear multi-agent systems

This paper investigates event-triggered formation control problems for general linear multi-agent systems. The time-varying formation this paper studied can be described by a bounded piecewise differentiable vector-valued function. Firstly, a time-varying formation control protocol based on event-triggered scheme is constructed by the states of the neighboring agents. Each agent broadcasts its state information to neighbor nodes if the triggering condition is satisfied, and the communication load is decreased significantly. Then, an algorithm consisting of three steps is proposed to design the event-triggered formation control protocol. Moreover, it is proven that under the designed event-triggered formation protocol, the multi-agent systems can achieve the desired time-varying formation which belongs to the feasible formation set with the bounded formation error and the closed systems do not exhibit Zeno behavior. Finally, simulation results are given to demonstrate the effectiveness of the theoretical analysis.

Guaranteed-Performance Time-Varying Formation Control for Swarm Systems Subjected to Communication Constraints

Guaranteed-performance time-varying formation analysis and design problems for general high-order swarm systems with communication constraints are investigated. First, a guaranteed-performance time-varying formation control protocol is proposed by using the intermittent relative local information, and the performance function is introduced to guarantee the formation regulation performance among neighboring agents. An explicit presentation of the formation center function is presented to describe the movement trajectory of the formation as a whole. Then, sufficient conditions for guaranteed-performance time-varying formation analysis and design are respectively given by linear matrix inequality techniques, and a guaranteed-performance cost is determined meanwhile. When the desired guaranteed-performance time-varying formation satisfies the time-varying formation feasibility condition, swarm systems with communication constraints can achieve the guaranteed-performance time-varying formation by designing the gain matrix of the guaranteed-performance time-varying formation control protocol if the nominal coverage rate is larger than a positive threshold. Finally, a numerical simulation is shown to illustrate theoretical results.

Distributed adaptive time-varying formation for multi-agent systems with general high-order linear time-invariant dynamics

This paper studies distributed time-varying formation control problems for general high-order linear time-invariant (LTI) multi-agent systems using an adaptive based approach. Firstly, a time-varying formation control protocol is constructed by the states of neighboring agents, which the adaptive gain scheduling technique is employed to estimate the coupling weights between neighboring agents. Different from the existing results on formation control, the formation can be specified by piecewise continuously differentiable vectors and no global information about the interaction topologies is required. Then an algorithm with two steps is presented to design the distributed adaptive formation control protocol, where a description of the feasible time-varying formation set is given. The stability of the algorithm is proved using the Lyapunov theory. It is shown that if the predefined time-varying formation belongs to the feasible formation set and each agent is stabilizable, then time-varying formation can be achieved by general high-order LTI multi-agent systems using the distributed adaptive formation protocol designed in the proposed algorithm. Finally, numerical examples are given to demonstrate the effectiveness of the theoretical results.

Formation Control for High-Order Linear Time-Invariant Multiagent Systems With Time Delays

Formation control problems for high-order linear time-invariant multiagent systems with time delays are investigated. First, a general time-varying formation control protocol is proposed. Then, based on consensus approaches, necessary and sufficient conditions for multiagent systems to achieve a given time-varying formation are presented. An explicit expression of the time-varying formation reference function is also given. It is shown that the motion modes of the formation reference can be specified. Furthermore, necessary and sufficient conditions for formation feasibility are proposed. An approach to expand the feasible formation set and an algorithm to design the protocol for multiagent systems to achieve time-varying formations are provided, respectively. Finally, numerical simulations are presented to demonstrate theoretical results.