Networked Lagrange Systems Research Articles

Safety Flocking of Networked Lagrangian Systems With Event-Triggered Communication

Safety Flocking of Networked Lagrangian Systems With Event-Triggered Communication

Adaptive Coordination of Networked Lagrangian Systems with Nonsmooth Actuator Nonlinearities

Adaptive Coordination of Networked Lagrangian Systems with Nonsmooth Actuator Nonlinearities

Distributed Coordination Control of Networked Lagrangian Systems With Velocity and Input Constraints Over Event-Triggered Communication

In this paper, the coordination control problem of networked Euler-Lagrange (E-L) systems with velocity and input constraints over event-triggered communication is considered. A novel distributed controller is proposed to achieve the control objective under reasonable initial conditions. Unlike existing methods, neither the proposed controller nor the event-triggered scheme relies on any global information of the communication graph. Also, Zeno behavior is proved to be non-existent. In addition, the constraints on the system velocity and input will not be violated. Finally, case studies and experiment results are provided to show the effectiveness of the proposed method.

Multiple-bipartite consensus for networked Lagrangian systems without using neighbours' velocity information in the directed graph

This paper investigates the multiple-bipartite consensus problem without considering neighbours' velocity information in networked Lagrangian systems (NLSs). A distributed adaptive control algorithm without using neighbours' velocity information is proposed, which facilitates the practical configuration deployments in the coopetition networks. By borrowing a subtle vector composed of the eigenvector components associated with zero eigenvalue of Laplacian matrix, a novel reference estimated vector is introduced to conduct the stability analysis step-by-step in the coopetition networks. Finally, simulations are provided to show the effectiveness of the proposed algorithm.

Achieving distributed consensus for networked uncertain Euler–Lagrange systems with average dwell time approach

AbstractThis paper proposes a novel distributed consensus achieving algorithm for switched networked Lagrange systems with uncertain parameters, in order to solve the abruptly occurrence problem of parameters changing and communication topologies switching. We first model the multirobot systems as switched networked Lagrange systems. Then, by introducing the network topology into the sliding mode vector, a unified distributed consensus tracking strategy is then proposed by systematically combining the average dwell time (ADT) approach and adaptive control method. Besides, a sufficient condition regarding the ADT among subsystems is derived to ensure the asymptotical consensus performance of the multirobot systems. A unified analysis methodology is developed to perform the convergence analysis for the closed‐loop system by Lyapunov stable theory. Finally, illustrative examples and simulations are provided to demonstrate and validate the theoretical results.

Resilient Consensus for Networked Lagrangian Systems With Disturbances and DoS Attacks

In this article, we consider the resilient consensus control problem of multiple Euler–Lagrange systems in the presence of external disturbances and denial-of-service (DoS) attacks, which have bounded duration and frequency. Unlike the most existing methods for linear multiagent systems, the strong nonlinearity, and unknown disturbances of multiple Euler–Lagrange systems make the resilient control problem under DoS attacks be more challenging and still not well explored. To this end, an adaptive control scheme is first proposed with a robust sliding mode-like term to handle the unknown bounded external disturbances. In addition, an auxiliary system is designed by using the sampled neighboring information to achieve resilience to DoS attacks. Sufficient conditions are presented by using Lyapunov and small-gain approaches. Finally, simulation results are given to verify the effectiveness of the proposed resilient consensus control approach.

Resilient Synchronization of Networked Lagrangian Systems Over Event-Based Communication With Asynchronous DoS Attacks

A wide range of actual systems can be modeled as Euler- Lagrange dynamics, its inherently complex nonlinearities present additional difficulties in the design of control algorithms. In this paper, the distributed resilient synchronization control problem of networked Euler- Lagrange (E-L) systems under event-based communication with distributed denial-of-service (DoS) attacks is considered. A novel distributed dynamic event-triggered scheme is proposed to schedule the communication source under asynchronous DoS attacks on different channels. Then, a self-triggered scheme is designed to reduce the updating number of the control signals. Under the proposed adaptive control scheme, the asymptotic synchronization of the closed-loop system is guaranteed under DoS attacks. Neither the control strategy nor the dual-terminal event-triggered scheme needs the eigenvalue information of the Laplace matrix. Also, no Zeno behavior occurs under the proposed event-based control and communication framework. Finally, case studies are provided to show the effectiveness of the proposed method.

Jamming-Resilient Synchronization of Networked Lagrangian Systems With Quantized Sampling Data

A wide range of cyber–physical systems can be modeled as Euler–Lagrange dynamics, whose inherent nonlinearities bring additional difficulties in the design and analysis of controllers for such systems. The objective of this article is to solve the jamming-resilient synchronization control problem of networked Lagrangian systems subject to unknown external disturbances, with the quantized sampling data. Under a jamming attack, a normal communication channel will be blocked with unknown frequencies and intervals. To achieve jamming attack resilience, a robust adaptive controller is proposed. Then a novel auxiliary system is designed for each subsystem over a directed network. By using the quantized sampling data from each subsystem and its neighbors, the jamming attack can be handled by an embedded single-integral subsystem. Sufficient conditions that are independent of the attack parameters are derived to guarantee the global stability of the closed-loop system. Compared with existing jamming-resilient methods, the proposed approach is concise and resilient to any jamming attacks with bounded frequencies and durations.

Dynamic event-Based resilient consensus of networked lagrangian systems under DoS attacks

In this paper, the dynamic event-based resilient consensus control of the multiple networked Euler-Lagrangian (E-L) systems under the Denial of Service (DoS) attacks is considered. Compared with linear cyber-physical systems, nonlinear networked E-L systems are more complex and closer to actual mechanical systems. For the situation where the topology is a strongly connected directed topology, a controller based on a dynamic event-trigger mechanism is designed to achieve consensus control for the networked E-L system in the absence of DoS attacks. Sufficient conditions are presented, which can guarantee the closed-loop system be stable. Then the resilient consensus problem of event-based controllers under energy-constrained DoS attacks is analyzed. The conditions related to the duration and frequency of DoS attacks are given. Zeno behavior is proved does not exist in the proposed control scheme. Finally, some numerical simulation results are given for verifying the theoretical results.

Fully distributed practical bipartite formation tracking of networked Lagrangian systems with actuator faults and bounded inputs

This paper investigates the bipartite formation tracking (BFT) problem of networked Lagrangian systems (NLSs) with signed directed graphs. Each system suffers from actuator fault with bounded input. Firstly, the unknown input of the leader is estimated for all the followers based on an observer in the prescribed time, which is constructed by employing a time base generator (TBG). Then, a hierarchical fully distributed controller is proposed to achieve BFT without using the global information with respect to the communication graphs. Then, the related sufficient condition for the system stability is derived by means of the Lyapunov theory. Finally, a simulation example is proposed to demonstrate the performance of the hierarchical fully distributed controller for achieving BFT.

Distributed multiple-bipartite consensus in networked Lagrangian systems with cooperative–competitive interactions

In combination with the collective behavior evolution of bipartite consensus and cluster/group consensus, this paper proposes the notion of multiple-bipartite consensus in networked Lagrangian systems (NLSs), effectively integrating the above emergent collective behaviors in cooperative–competitive networks. The problems of leaderless multiple-bipartite consensus and leader-following multiple-bipartite tracking consensus are solved via deploying the designed distributed adaptive torque controllers for uncertain NLSs. Compared with the traditional bipartite consensus framework, antagonistic interactions can exist in the same subnetwork. By introducing an acyclic partition and adding the integral item in the distributed adaptive torque control protocols, the explicit expressions of the final states are eventually obtained in the leaderless case. Moreover, the leader-following case can be realized in finite time resorting to two predefined estimators embedded in the scheme. The effectiveness of two scenarios has been illustrated through numerical simulations with ten heterogeneous mechanical manipulators.

Practical Bipartite Consensus for Networked Lagrangian Systems in Cooperation-Competition Networks

Practical Bipartite Consensus for Networked Lagrangian Systems in Cooperation-Competition Networks

Group consensus coordination control in networked nonholonomic multirobot systems

In this article, the coordination control problem of group tracking consensus is considered for networked nonholonomic mobile multirobot systems (NNMMRSs). This problem framework generalizes the findings of complete consensus in NNMMRSs and group consensus in networked Lagrangian systems (NLSs), enjoying capacious application backgrounds. By leveraging a kinematic controller embedded in the adaptive torque control protocols, a new convergence criterion of group consensus is established. In contrast to the formulation under strict algebraic assumptions, it is found that group tracking consensus for NNMMRSs can be realized under a simple geometrical condition. The system stability analysis is dictated by the property of network topology with acyclic partition. Finally, the theoretical achievements are verified by illustrative numerical examples. The results show an interesting phenomenon that, for NNMMRSs, the state responses exhibit negative correlation with the algebraic connectivity and coupling strength.

Leader-Following Regional Multiple-Bipartite Consensus for Networked Lagrangian Systems with Coopetition Interactions

This paper investigates the leader-following regional multiple-bipartite consensus problems of networked Lagrangian systems (NLSs) in coopetition networks. Our framework expands the application scopes of traditional regional consensus in cooperative networks. With the aid of a novel auxiliary variable embedded in the control protocols, the final states of NLSs are guaranteed to realise multi-regional symmetry in the constructed multiple symmetric regions. By utilising the characteristic of acyclic topology in the structurally balanced graph, the stability of the closed system is performed by perturbation analysis theory, nonlinear control theory, functional analysis theory, and so on. Finally, the effectiveness of our approach is verified by numerical simulations.

Consensus Control for Networked Manipulators With Switched Parameters and Topologies

To solve abruptly occurrence of parameters jumping and directed communication topologies changing in the control process of networked manipulators, in this paper, distributed switched consensus control algorithms are formulated for a group of robot manipulators in realizing cooperative consensus performance. In fact, networked Lagrange systems are modeled as switched systems regarding the different parameters and topologies. Namely, the dynamic models switch when the system parameters or the topology structures change. The consensus control strategy is constructed by resorting to (improved) average dwell time (ADT) method and sliding-mode control technique, and a unified analysis methodology is developed to perform the convergence analysis for the closed-loop system by Lyapunov stable theory. The main contribution of this paper is the development of a systematically adaptive consensus algorithm by simultaneously considering shifting parameters and switching communication network (as two unavoidable key factors) in the process of communication interaction among robots. A distinctive feature of the developed consensus protocol is to introduce the directed network topology characterizing the local communication interaction among robots, which is especially suitable for representing the the structures and features of the realistic cooperative multi-robotic systems. Accordingly, the developed consensus tracking strategy for manipulators possess prominent advantages including robustness,stability and effectiveness over the existing concentrated on single robot counterparts. Finally, numerical simulations of two-link manipulators are performed to illustrate the effectiveness of the obtained control algorithm.

Event‐based resilience to DoS attacks on communication for consensus of networked Lagrangian systems

SummaryIn this article, we consider the resilience analysis of the even‐based consensus control of networked Lagrangian systems under denial‐of‐service (DoS) attacks, which are usually implemented by the attackers to block the communication channels. Comparing with the linear cyber‐physical systems, the secure control of the networked Lagrangian systems is more complex and challenging, especially under the conditions of asymmetry communication and discontinuous control. To this end, an event‐based controller is first designed for consensus control of networked Lagrangian systems in the absence of DoS attacks. Sufficient conditions are given to stabilize the closed‐loop systems. Then the resilience analysis is presented for the event‐based controller under DoS attacks. Some conditions associated with the DoS duration and frequency are proposed for the control parameters against the attacks. Then Zeno behaviors are proved to be nonexistent in the proposed control scheme. An algorithm is also given to guide the control design.

Resilient Cooperative Control for Networked Lagrangian Systems Against DoS Attacks.

In this article, we study the distributed resilient cooperative control problem for directed networked Lagrangian systems under denial-of-service (DoS) attacks. The DoS attacks will block the communication channels between the agents. Compared with the existing methods for the linear networked systems, the considered nonlinear networked Lagrangian systems with asymmetric channels under DoS attacks are more challenging and still not well explored. In order to solve this problem, a novel resilient cooperative control scheme is proposed by using the sampling control approach. Sufficient conditions are first derived in the absence of DoS attacks according to a multidimensional small-gain scheme. Then, in the presence of DoS attacks, the proposed resilient scheme works in a switching manner. Inspired by multidimensional small-gain techniques, the Lyapunov approach is used to analyze the closed-loop system, which enables us to establish sufficient stability conditions for the control gains in terms of the duration and frequency of the DoS attacks.

Distributed Consensus of Networked Lagrangian Systems With Unknown Nonidentical Control Directions

In the literature, most of the consensus methods require the control directions of all agents to be known. This paper deals with the distributed consensus problem without such requirements for networked Lagrangian systems subjected to uncertain dynamics. Unknown control directions are nonidentical in the sense that the control direction related to each control input in an individual Lagrangian system can be different and unknown as well as that the control directions for different Lagrangian systems are allowed to be distinct. Regarding the communication topology, the only requirement is to contain a fixed directed spanning tree. Based on the estimated consensus value, novel auxiliary sliding mode variables are constructed and applied to develop the distributed adaptive consensus control scheme. It is proved by adopting the special properties of the Laplacian matrix on directed graphs and matrix theory that global uniform boundedness of all closed-loop signals and the asymptotic consensus can be achieved. Simulations on networked two-link revolute joint arms are provided to verify the validity of the proposed scheme.

Connectivity-preserving flocking for networked Lagrange systems with time-varying actuator faults

This paper studies fault-tolerant coordination with connectivity preservation and collision avoidance for unknown Lagrange agent systems subject to actuator faults. In contrast to the existing works, the actuator faults may change the states of the agents to violate the network connectivity and the existence of the loss of effectiveness faults makes control coefficients unknown and time-varying. Furthermore, the leader’s dynamics are allowed to be nonlinear instead of being linear and generated by a marginally stable system. The aforementioned setting improves the practical relevance of the problem to be addressed in the paper and meanwhile, it poses technical challenges to flocking controller design and asymptotic stability analysis. Consequently, for a class of nonlinear leader systems, a novel distributed adaptive scheme is proposed by introducing a distributed estimator and a Nussbaum gain technique to provide a fully distributed solution with guaranteed fault-tolerant coordination, connectivity preservation, and collision avoidance simultaneously. Numerical examples are given to illustrate the effectiveness of the design.

Tracking Synchronization of Networked Lagrangian Systems via Impulsive Control and Its Applications

An impulsive control scheme is proposed to investigate the tracking synchronization of ring and inline networked Lagrangian systems. Given a time-varying target trajectory, some algebraic synchronization criteria are derived to make the networked Lagrangian systems synchronize to the target trajectory. A distinctive feature of the proposed work is that the impulsive control scheme is used to investigate the highly nonlinear Lagrangian systems. By the impulsive control, each agent described by the Lagrangian system instantaneously interacts with its neighbors only at some discrete moments. Furthermore, the proposed control strategy requires only local coupling feedback for global convergence. As a direct application of the obtained theoretical results, the tracking synchronization of multiple 3-DOF mobile robots is discussed in detail and simulated. Simulation results verify the effectiveness of the proposed control strategy.