Distributed Finite-time Observer Research Articles

Distributed Neural Adaptive Impedance Control for Cooperative Manipulation With Unknown Objects.

Existing cooperative manipulation methods for multiple manipulator systems usually assume that the grasp matrix and the desired trajectory of each manipulator are known in advance. In this work, distributed neural adaptive impedance control (AIC) strategies integrating fully distributed observers are proposed to remove both limitations. Specifically, two fully distributed finite-time observers are designed to estimate the actual and ideal states of the reference point without using global information. The estimates of the grasp matrix and the desired trajectory of each end-effector (EE) are then obtained by kinematic constraints and the estimates of the reference point's states. At the controller development, a distributed adaptive impedance model is established to achieve an adaptive trade-off between tracking performance and compliance. Then, distributed neural network (NN)-based tracking control strategies are developed to asymptotically realize the desired adaptive impedance dynamics in the presence of uncertainties. Additionally, a virtual energy tank (EK) is employed to interact with the impedance system to correct the adaptive impedance laws for system passivity. A simulation for four mobile manipulators tightly cooperative transport an unknown object is carried out to demonstrate the established results.

Distributed finite-time attack detection and estimation of intelligent connected vehicle platoon

ABSTRACT This paper presents a distributed finite-time observer design approach for the problem of intelligent connected vehicles (ICVs) containing both attack signals and unknown disturbances. Firstly, an analysis is conducted on the two types of network attacks that ICVs may encounter, followed by the construction of a dynamic vehicle model and its transformation into a state space equation. Secondly, an intermediate variable is introduced to design a distributed attack estimation observer, which both ensures accurate estimation of the vehicle safety state and attack signal within a limited time and overcomes the constraints of traditional observers. Additionally, sufficient conditions for the finite-time boundedness of the observer error system with H ∞ performance are provided in the form of linear matrix inequalities. Furthermore, an adaptive threshold attack detection method is designed. Finally, the simulation results validate the efficiency of the design methods.

Distributed Finite-Time Observer for Multiple Line Outages Detection in Power Systems

Distributed Finite-Time Observer for Multiple Line Outages Detection in Power Systems

Distributed Finite-time Observer for Rapid Detection of Multiple Line Outages in Transmission Networks with Uncertain Parameters

Distributed Finite-time Observer for Rapid Detection of Multiple Line Outages in Transmission Networks with Uncertain Parameters

Finite-Time Output Regulation of Linear Heterogeneous Multi-Agent Systems Using Smooth Control

In this paper, we investigate a finite-time output regulation (FTOR) problem for linear heterogeneous multi-agent systems (LHMAS). The objective is to design protocols such that each agent can follow the reference signal within a finite time. An exosystem is given to generate the reference signal and disturbances. Only a part of agents are assumed to have access to the system matrix and state of the exosystem. First, smooth distributed finite-time observers are designed to estimate them. Then, with the help of feedforward method, smooth state feedback and output feedback controllers are designed to address the FTOR problem. By virtue of the finite-time control method and the OR technique, it is shown that the proposed smooth distributed observers and controllers can achieve the finite-time convergence of the estimation errors and error outputs, respectively. Finally, a numerical example is presented for illustration.

Analysis and design of control systems via parameter‐based approach

Analysis and design of control systems via parameter‐based approach

Distributed finite-time neural network observer-based consensus tracking control of heterogeneous underwater vehicles

This note scrutinizes the distributed finite-time tracking problem of heterogeneous multi-agent systems with uncertain dynamics and environmental disturbances. To estimate the exogenous disturbances, an adaptive neural network-based disturbance observer is developed in which the approximation error of the neural network is compensated using adaptation laws. Based on finite-time stability theory, a distributed finite-time observer is proposed for each follower in order to estimate the leader's position. Moreover, an adaptive dynamic sliding mode-based controller is also developed for each follower, which ensures finite-time convergence of the tracking error between the leader and the follower. Incorporating adaptive control into the developed composite control structure leads to reducing the chattering, as well as enhancing the robustness and accuracy. Stability analysis and finite-time convergence of the tracking error are performed using the Lyapunov theory and multiple time scale principle, respectively. Finally, simulations and comparisons are performed in order to verify the effectiveness of the developed control algorithm for a group of autonomous underwater vehicles (AUVs).

Distributed Finite-Time Safety Consensus Control of Vehicle Platoon With Senor and Actuator Failures

Due to the numerical subsystems and functionalities among the platoon, failures easily occur and lead vehicle safety and stability to deteriorate. With the surge of platoon connectivity, the abnormal states arising in faulty vehicles will have an impact on adjacent healthy vehicles, potentially resulting in severe traffic accidents. To address the aforementioned problems and improve the functional safety of platoons, a systemic anti-fault safety consensus strategy is proposed in this article to deal with sensor faults, LOE actuator faults, and bias actuator faults simultaneously. To tackle the necessary defects, this safety consensus technique can be split into fault detection tasks and fault-tolerant control tasks. Initially, a distributed finite-time observer is employed to detect sensor faults through the index between the reconstructed states and received states. In the presence of actuator faults, a novel adaptive finite-time fault parameter estimation law collaboration with a feasible differential observer is developed to assess the precise fault extent. In addition, to improve the estimation performance of the adaptive fault parameter estimation law, an integral discounted cost function is constructed in this paper to obtain the optimal learning gain. Via theoretical analysis, the solution for the minimal value of the cost function and the finite-time convergence property are demonstrated in this paper. Furthermore, by utilizing this novel adaptive optimal finite-time estimation law, a novel distributed adaptive finite-time fault-tolerant controller is constructed to compensate for failures in platoon. Finally, the effectiveness and feasibility of our safety consensus strategy are verified by real-time simulations through the dSPACE platform.

Fully distributed adaptive finite-time consensus over uncertain network topology

ABSTRACT Communication network could suffer uncertainties originating from link faults and network attacks. This situation, in multi-agent systems, can be featured by unknown weights of network topology. To impair the influence of the uncertain topology, typical compensation should be taken into account in distributed protocols to the workability of multi-agent systems. This paper, in the context of uncertain topology, addresses finite-time leader-following consensus for second-order uncertain nonlinear multi-agent systems. In addition to uncertainties in topology, the systems also allow unknown control coefficients, which together with the unknown weights renders the realisation of finite-time leader-following consensus nontrivial. Specifically, a fully distributed protocol based on distributed finite-time observer is designed via integrating the adaptive compensation scheme. Notably, in the designed protocol, dynamic high gains are introduced for the compensations of the network uncertainties and agents uncertainties. It turns out that the designed fully distributed protocol guarantees the global finite-time leader-following consensus. Simulation examples are provided to illustrate the validity of the proposed approach.

Finite-Time Velocity-Free Rendezvous Control of Multiple AUV Systems With Intermittent Communication

In this study, a finite-time velocity-free rendezvous control method is considered for multiple autonomous underwater vehicle (AUV) systems with intermittent undirected communication. First, we develop a distributed finite-time observer for each AUV to estimate its own state information. Second, we design a rendezvous control algorithm that utilizes the estimated state information intermittently through a communication network in the absence of velocity measurement. A homogeneous method is used to prove that all AUVs in the group can achieve rendezvous in finite time for a network with intermittent communication, even without velocity measurements. The proposed method is shown to reduce the communication load of the system. More importantly, the control algorithm achieves the control goal of the system and is proven to be viable for many practical applications of multiple AUV systems from both economic and security perspectives. Finally, the effectiveness of the proposed control protocol is demonstrated via numerical simulations.

Finite‐time attitude consensus control for multiple rigid spacecraft based on distributed observers

The problem of attitude consensus control is addressed for multiple rigid spacecraft under a fixed interaction network where only a subset of followers can obtain the leader's state information. To estimate the attitude and angular velocity of the leader, a group of distributed finite-time observers is constructed for each follower. Then fast non-singular terminal sliding mode attitude controllers are proposed for followers based on the observed information. Rigorous proofs are presented to show the finite-time attitude consensus performance of the closed-loop multiple rigid spacecraft systems under the proposed consensus protocol including distributed observers and attitude controllers. Numerical simulations are provided to illustrate the performance of the proposed attitude consensus protocol.

Finite-time observer based tracking control of uncertain heterogeneous underwater vehicles using adaptive sliding mode approach

In this study, a finite-time consensus tracking problem is investigated for a group of autonomous underwater vehicles (AUVs) with heterogeneous uncertain dynamics. We firstly propose a two-layer distributed control strategy, which consists of an upper-layer distributed observer and a lower-layer controller, without using any global information. Based on Hölder’s inequality and the theory of finite-time stability, a distributed finite-time observer is developed for each follower to estimate the position information of a leader (i.e., an exosystem). Based on the sliding mode control method, a consensus tracking control scheme is designed for each AUV, by which all follower AUVs can track the leader in finite time. Secondly, when the parameters in the AUV dynamics are uncertain, a parameter-adaptive sliding mode control algorithm is introduced to improve the control performance. Finally, simulation results are presented to demonstrate the effectiveness of the proposed control algorithms.

Cooperative Startup Control for Heterogeneous Vehicle Platoons: A Finite-Time Output Tracking-Based Approach

The connected vehicle (CV) technology has emerged in recent years. This article studies cooperative startup control of heterogeneous CVs in a platoon. First, from the perspective of cooperative tracking of heterogeneous multiagent systems, a hierarchical finite-time control framework is established, which consists of an upper-level interactive observer layer and a lower-level local controller layer. By separating neighboring information interaction from local dynamics control, the proposed framework allows to design upper-level observers and lower-level local controllers separately. Second, by introducing a potential function related to the consensus and observing errors, a distributed finite-time observer is designed for each CV to observe a startup reference trajectory available for only part of the CVs. Third, a distributed local finite-time controller is designed for each CV to track its observed startup reference trajectories. Within the proposed framework, finite-time observing and tracking of the startup reference trajectory are strictly proved to guarantee cooperative startup control. Numerical simulations are carried out to demonstrate the effectiveness of the proposed methods.

Finite-time velocity-free observer-based consensus tracking for heterogeneous uncertain AUVs via adaptive sliding mode control

In this study, a finite-time velocity-free position consensus tracking control method is investigated for multiple autonomous underwater vehicle (AUV) systems with heterogeneous uncertain dynamics. First, two distributed finite-time observers are developed for each follower AUV to estimate the state information of the leader and follower-AUVs’ own. Subsequently, via the sliding mode control technique, a consensus tracking control algorithm based on the estimated information is designed, such that each follower AUV can track the leader’s position trajectory within a finite-time, even in the absence of velocity measurement. Second, for the situation involving uncertain model parameters, a parameter adaptive sliding mode-based control algorithm is proposed to improve the performance of the closed-loop AUV system. The two controllers only require the position information of the AUVs. Finally, two numerical simulations are carried out to validate the effectiveness of the two proposed control protocols.

Finite-time resilient attitude coordination control for multiple rigid spacecraft with communication link faults

In this work we address the finite-time resilient attitude coordination control problem for a group of rigid spacecraft under a directed communication graph. Based on the high gain technique and the finite-time observer method, a distributed finite-time observer, where only the estimated attitudes of the leader are required to exchange among spacecraft, is designed to estimate the leader's attitude and velocity. The resilience of the distributed observer to communication link faults is proven by use of the homogeneity property. Then, a distributed finite-time attitude coordination control protocol is proposed to guarantee the finite-time convergence of the attitude tracking errors to a small neighborhood of zero. Finally, numerical studies are carried out to demonstrate the effectiveness of the derived control law.

Finite-time formation-containment tracking for second-order multi-agent systems with a virtual leader of fully unknown input

This paper studies the finite-time time-varying formation-containment tracking problems for second-order multi-agent systems with directed topology, where the multi-agent system consists of one virtual leader with fully unknown input, several real leaders and followers. In contrast with traditional formation and containment cases studied in most of the existing literature, apart from accomplishing the expected time-varying formation, the real leaders are required to track the trajectory generated by the virtual leader, and the followers need to get into the convex envelope spanned by the real leaders in finite time. The method for solving the finite-time formation-containment tracking problems is divided into the following steps. First, distributed finite-time observers are designed for each real leader and follower, in order to obtain the estimated states of their neighbor agents. Then, formation-containment tracking protocols are presented by using the neighboring information for both real leaders and followers. Furthermore, based on Lyapunov theory, it is proved that the given formation-containment tracking can be realized in finite time by the multi-agent system under the designed protocols. Finally, a case study on multi-robot transport operation is given to verify the effectiveness of the theoretical results.

Distributed adaptive fault-tolerant output regulation of heterogeneous multi-agent systems with coupling uncertainties and actuator faults

In this paper, we consider the distributed adaptive fault-tolerant output regulation problem for heterogeneous multiagent systems with matched system uncertainties and mismatched coupling uncertainties among subsystems under the influence of actuator faults. First, distributed finite-time observers are proposed for all subsystems to observe the state of the exosystem. Then, a novel fault-tolerant controller is designed to compensate for the influence of matched system uncertainties and actuator faults. By using the linear matrix inequality technique, a sufficient condition is provided to guarantee the solvability of the considered problem in the presence of mismatched coupling uncertainties. Moreover, it is shown that the system in closed-loop with the developed controller can achieve output regulation by using the Lyapunov stability theory and cyclic-small-gain theory. Finally, a numerical example is given to illustrate the effectiveness of the obtained result.

Distributed Finite-Time Coordinated Attitude Tracking Control for Multiple Spacecraft with Actuator Saturation

For multi-spacecraft with actuator saturation, inertia uncertainties and external disturbances, a distributed finite-time coordinated attitude tracking control problem for the spacecraft with the communication topology containing fewer information paths is investigated. Aiming at reducing the communication path, a class of distributed finite-time state observers is designed. To speed up the convergence rate of the multiple spacecraft system, a fast nonsingular terminal sliding mode function is proposed. Moreover, an adaptive control term is proposed to suppress the impact of the external state-dependent disturbances and unknown time-varying inertia uncertainties. Further considering the actuator saturation owing to its physical limitations, a saturation function is designed. With the distributed finite-time observers, the fast nonsingular terminal sliding mode function, the adaptive update law and the saturation function, a distributed finite-time coordinated attitude tracking saturation controller is designed. Using the proposed controller, the follower can synchronize with the common leader with time-varying trajectory in finite time. Simulation results demonstrate the effectiveness of the designed controller.

A Distributed Framework for $k$-hop Control Strategies in Large-Scale Networks Based on Local Interactions

In this paper, we propose a distributed framework for large-scale networks to attain control strategies requiring $k$ -hop interactions. This research is motivated by the observation that in many practical applications and operational domains involving large-scale networks, such as environmental monitoring or traffic load balancing, agents may be required to collect only information concerning other agents located sufficiently close to them, that is agents topologically at most $k$ -hop away. In this setting, distributed observers available at the state of art, which typically estimates the full network state, may be inadequate due to scalability issues. Differently, we propose a distributed finite-time observer which allows each agent to estimate the state of its $k$ -hop neighbors by interacting only with the agents belonging to its 1-hop neighborhood. Furthermore, we demonstrate that for feedback control strategies based on $k$ -hop neighborhood information, which are input-to-state stable, the proposed distributed finite-time observer can be effectively used to design stable large-scale networked control strategies. Numerical results are provided to corroborate the theoretical findings.

Flatness-based finite-time leader–follower formation control of multiple quadrotors with external disturbances

This study considers the leader–follower formation control problem for multiple quadrotors in the presence of external disturbances. Based on the differential flatness theory, the underactuated quadrotor system is transformed into a fully actuated one with four degrees of freedom and four control inputs. Based on this model, a distributed finite-time observer is developed to reconstruct the leader's states for each follower. Then, an observer-based finite-time controller is proposed based on an adaptive disturbance rejection approach, which is independent of the upper bounds of the disturbances, to address the formation control problem for multiple quadrotors. The stability analysis indicates that the closed-loop system theoretically achieves the finite-time stability and robustness against the disturbances. Finally, a numerical simulation is provided to verify the performance of the proposed formation control scheme.