Fault-tolerant Formation Control Research Articles

Adaptive distributed fault-tolerant control for underactuated surface vehicles with bridge-to-bridge event-triggered mechanism

This paper investigates an adaptive distributed fault-tolerant formation control scheme for multiple underactuated surface vehicles (USVs) with the bridge-to-bridge event-triggered communication mechanism. In particular, under the directed topology, information from each USV is broadcast to the adjacent vehicles only if the event-triggered condition is satisfied. The benefit of the proposed event-triggered communication mechanism eliminates the requirement of either the continuous monitoring of adjacent vehicles’ states or global graph information, which can address the problem of the limited communication bandwidth in the marine practice. Based on the event-triggered communication, backstepping and directed topology, an adaptive distributed formation controller is developed for each USV. Besides, the unknown structure uncertainty and external disturbances are compressed together to compensate by introducing the neural network (NN) approximator and the neural damping technique. And the derived adaptive law can also compensate the adverse effect of unknown actuator faults and gain uncertainty. Through the Lyapunov theory, all signals in the closed-loop system are proved to be with the semi-global uniform ultimate bounded (SGUUB) stability. Finally, the numerical simulation is illustrated to verify the effectiveness of the control algorithm.

Fault-Tolerant Formation Control for Heterogeneous Vehicles Via Reinforcement Learning

This article focuses on the formation control problem of multiple heterogeneous vehicles in air–ground coordination under communication link faults and actuator faults. To address communication link faults among heterogeneous vehicles, a distributed observer is first designed using the air and ground local vehicle information and its convergence is discussed. Using the outputs of the distributed observer and the states of the vehicles, fault-tolerant controller policies are designed for the team of heterogeneous vehicles via reinforcement learning but without knowledge of the vehicle dynamics. Simulation results are included to demonstrate the effectiveness of the proposed fault-tolerant controller.

Distributed Fault Estimation and Fixed-Time Fault-Tolerant Formation Control for Multi-UAVs subject to Sensor Faults

Distributed Fault Estimation and Fixed-Time Fault-Tolerant Formation Control for Multi-UAVs subject to Sensor Faults

Distributed adaptive fault-tolerant formation control for heterogeneous multiagent systems under switching directed topologies

This paper studies the cooperative fault-tolerant formation control problem of tracking a dynamic leader for heterogeneous multiagent systems consisting of multipile unmanned aerial vehicles (UAVs) and unmanned ground vehicles (UGVs) with actuator faults under switching directed interaction topologies. Based on local neighborhood formation information, the distributed fault-tolerant formation controllers are constructed to ensure that all follower UAVs and UGVs can accomplish the demanding formation configuration in the state space and track the dynamic leader’s trajectory. By incorporating the sliding mode control and adaptive control technique, the actuator faults and unknown parameters of follower agents can be compensated. Through the theoretical analysis, it is proved that the cooperatively semiglobally uniformly ultimately boundedness of the closed-loop system is guaranteed, and the formation tracking errors converge to a small adjustable neighborhood of the origin. A simulation example is introduced to show the validity of the proposed distributed fault-tolerant formation control algorithm.

Integrated active fault‐tolerant formation control for networked multi‐agent systems

This paper focuses on the design and simulation of an integrated reconfigurable control strategy for networked multi-agent systems. The control task is to remain the desired time-varying formation in the presence of actuator faults, and to well address the pairing between fault estimation and reconfigurable formation control. A decentralized fault estimation method using observer based estimator is presented to estimate both additive and multiplicative fault values. The reconfigurable control is constructed by adaptive technique using a distributed strategy. Only the information from neighboring agents as well as the fault values are required. The adaptive gains and fault estimates are designed by analyzing the Lyapunov stability of the overall system. The simulation results validate that the proposed integrated fault-tolerant formation control scheme can recover the original desired formation if there are faulty agents in system.

Fault-Tolerant Formation Control of Passive Multi-Agent Systems Using Energy Tanks

This letter considers the design of a fault-tolerant formation control law for multi-agent systems using energy balancing methods. Decentralized algorithms for fault diagnosis and graph topology update are proposed, and a formation reconfiguration procedure is developed based on energy tanks, which are able to guarantee that new connections among the agents can be established in a passive way. A simulation study supports and corroborates the theoretical findings.

Distributed Adaptive Fault-Tolerant Formation Control for Heterogeneous Multiagent Systems With Communication Link Faults

In this paper, we investigate the distributed adaptive fault-tolerant formation control problem for a group of heterogeneous multiagent systems consisting of multiple follower unmanned aerial vehicles (UAVs) and unmanned ground vehicles (UGVs) with parametric uncertainties and communication link faults. Based on the local states information of the vehicles, the adaptive fault-tolerant formation control protocol with varying control gains is developed for each follower UAV and UGV such that all followers track the dynamic trajectory of the virtual leader and obtain the expected formation configuration simultaneously under the influence of communication link faults and external disturbances. The distributed formation tracking convergence performance is discussed through Lyapunov theory. Finally, a simulation study based on the UAVs-UGVs collaborative systems is provided to show the effectiveness of the developed control strategy.

Data-driven fault-tolerant formation control for nonlinear quadrotors under multiple simultaneous actuator faults

This paper addresses the problem of data-driven fault-tolerant formation control for quadrotors with nonlinearities, unknown system parameters, and multiple actuator faults in the vehicle dynamics. A distributed fault-tolerant formation control law is developed including a distributed observer to generate the position reference for each vehicle, a fault-tolerant position control law to track the position reference, and a fault-tolerant attitude control law to regulate the attitude. Reinforcement learning approaches are implemented to update the optimal control weights in the fault-tolerant formation control law design. Stability of the proposed fault-tolerant formation control law is proven and simulation results of quadrotors under multiple actuator faults are provided to demonstrate the effectiveness of the proposed method.

Fault-Tolerant Fuzzy Formation Control for a Class of Nonlinear Multiagent Systems Under Directed and Switching Topology

The fault-tolerant formation control problem of a class of nonlinear multiagent systems with actuator/sensor faults under directed and switching network topology is addressed in this article. The main contributions are as follows: 1) the developed controller is effective to compensate for actuator/sensor faults and unknown nonlinearity simultaneously and 2) in contrast to the existing fault-tolerant formation control results, the more general directed and switching network topology is considered. In particular, by using a fuzzy logic system to approximate unknown nonlinearity and by introducing fault estimators to estimate actuator/sensor faults, a novel distributed fuzzy formation controller is developed. By virtue of introducing a modification technique in adaptive law, the phenomenon of strictly increase in adaptive law caused by actuator/sensor faults and unknown nonlinearity can be avoided. In addition, the uniformly ultimately bounded of the formation errors can be shown by introducing a novel Lyapunov function and a new analysis method. The efficiency of the developed method can be shown by an illustrative example demonstrates.

Fault estimation and fault tolerance control for spacecraft formation systems with actuator fault and saturation

AbstractIn this study, a novel fault estimation and fault tolerant control (FTC) scheme is proposed for a class of nonlinear spacecraft formation flying systems in actuator fault and saturation case, in which the directed communication topology with leader spacecraft as the root. The decentralized unknown input observer is designed to estimate the unknown actuator fault factors, which affect the performance of spacecraft formation flying systems. The obtained fault estimated values are served as the design of distributed fault tolerant formation controller. Then, a distributed fault tolerant formation control algorithm is proposed using adaptive terminal sliding mode control (ATSMC) technique, such that each follower spacecraft could synchronize with leader spacecraft in the presence of actuator fault and saturation case. Finally, the effectiveness of the proposed FTC scheme is verified by numerical practical examples.

Fixed-Time Fault-Tolerant Formation Control for Heterogeneous Multi-Agent Systems With Parameter Uncertainties and Disturbances

This paper investigates the fixed-time time-varying formation control problems for heterogeneous multi-agent systems (MASs) composed of multiple Unmanned Ground Vehicles (UGVs) and multiple Unmanned Aerial Vehicles (UAVs) in the presence of actuator faults, parameter uncertainties, matched and mismatched disturbances. Besides achieving the desired formation configurations, each follower can also track the position trajectory produced by the virtual leader within fixed time simultaneously. The difference dynamic characteristics between the heterogeneous agents leads to unbalanced interaction of lumped uncertainties in the communication network, which increases the difficulty of collaborative control. To estimate the mismatched disturbances and lumped uncertainties, a fixed-time observer for each follower is designed, which can guarantee the estimation errors converge to the origin in fixed settling time. Subsequently, by utilizing the backstepping technique and the fixed-time stability theory, an observer-based distributed fixed-time formation controller for each follower in the $X$ - $Y$ axes and the observer-based decentralized fixed-time tracking controllers for follower-UAVs in the $Z$ axes are presented, which are shown to be fixed-time stable even under the influence of actuator faults and mismatched disturbances. Moreover, the fixed-time results can ensure the convergence time is independent of initial conditions. Finally, numerical simulations demonstrate the effectiveness of the proposed algorithms.

LVS guidance principle and adaptive neural fault-tolerant formation control for underactuated vehicles with the event-triggered input

This paper presents a novel adaptive neural event-triggered formation control strategy for underactuated surface vehicles (USVs) in the presence of marine practical constraints, i.e. the waypoints-based planned path and actuator failures. The proposed strategy is composed of the guidance model and the control one. For the guidance part, the logic virtual ship (LVS) guidance principle is developed to implement the reference path programming for the formation pattern. For merit of the adaptive virtual ship, the smooth reference can be produced for followers without using the velocity information of leader. Furthermore, the proposed adaptive neural fault-tolerant control algorithm is to guarantee that the followers can maintain their pattern and converge to the corresponding reference path. In the algorithm, the neural networks (NNs)-based observer is designed to estimate the unmeasurable velocities of followers online. With the input event-triggered mechanism, two adaptive parameters are derived to compensate for the gain uncertainty and actuator failure. And that could effectively reduce the communication burden for the channel from controller to actuator. The derived closed-loop system has been proved to be with the semi-global uniform ultimate bounded (SGUUB) stability. Finally, the superiority of the proposed strategy can be verified by the simulation experiments.

Fault-Tolerant Formation Tracking Control for Heterogeneous Multiagent Systems with Directed Topology

In this paper, the adaptive fault-tolerant formation tracking control problem for a set of heterogeneous unmanned aerial vehicle (UAV) and unmanned ground vehicle (UGV) systems with actuator loss of effectiveness faults is investigated. The cooperative fault-tolerant formation control strategy for UAV and UGV collaborative systems is classified into the altitude consensus control scheme for follower UAVs and the position cooperative formation control scheme for all followers. The altitude consensus control algorithm is designed by utilizing backstepping control technique to drive all UAVs to a desired predefined height. Then, based on synchronization formation error information, the position cooperative formation control algorithm is proposed for all followers to reach the expected position and perform the desired formation configuration. The adaptive fault estimation term is adopted in the designed fault-tolerant formation control algorithm to compensate for the actuator loss of effectiveness fault. Finally, a simulation example is proposed to reveal the validity of the designed cooperative formation tracking control scheme.

Distributed fault-tolerant formation control for multiple unmanned aerial vehicles under actuator fault and intermittent communication interrupt

This article develops a distributed adaptive fault-tolerant formation control scheme for the multiple unmanned aerial vehicles to counteract actuator faults and intermittent communication interrupt, where the issues on control input saturation and mismatched uncertainties are also addressed. The discontinuous communication protocol technique is exploited to achieve the stability of the formation system, if the conditions of dwell time and the rate of communication are satisfied. On the basis of the local information of neighboring unmanned aerial vehicles, a novel distributed adaptive mechanism is designed to estimate the bounds of actuator faults and uncertainties, where the input saturation is explicitly taken into consideration. The stability of the whole formation system under the designed fault-tolerant formation control strategy is analyzed using the Lyapunov approach. Finally, simulation results are presented to illustrate the effectiveness of the proposed scheme.

Fully distributed adaptive fault-tolerant formation control for octorotors subject to multiple actuator faults

In this paper, the fault-tolerant formation control for multiple octorotor unmanned aerial vehicles is investigated. A fully distributed adaptive fault-tolerant formation control scheme is presented to achieve a desired formation flight under multiple uncertainties and actuator faults. The developed controller does not require the global information of the constructed communication network and the knowledge of faults. The robust formation system stability under multiple uncertainties and actuator faults is proven by Lyapunov analysis. Simulation results for octorotor formation flying are provided to demonstrate the effectiveness.

Real-Time Fault-Tolerant Formation Control of Multiple WMRs Based on Hybrid GA–PSO Algorithm

A fault-tolerant formation control (FTFC) strategy is proposed against severe actuator faults, applied to a team of wheeled mobile robots (WMRs). In the beginning, a team of WMRs is operating in a prescribed formation topology. As long as the robot(s) cannot complete the required mission due to severe actuator faults, the formation is reconfigured for the healthy WMRs to eliminate the fault effects. The new reconfiguration is determined by means of an optimal assignment scheme so that each healthy robot can be assigned to a unique position. Subsequently, each robot starts planning its trajectory to reach its new position in the new formation configuration by virtue of a hybrid genetic algorithm and particle swarm optimization (GA–PSO). As metaheuristic optimization techniques, such as GA and PSO, are unable to solve the optimization problem with continuous control inputs, control parameterization and time discretization (CPTD) method is, therefore, adopted to offer an approximate piecewise linearization of the control inputs. Thus, an approach with the integration of CPTD and GA–PSO is developed. This integrated approach enables that the time of achieving the configuration is minimized, while the physical constraints of WMRs and collision avoidance are explicitly considered. Finally, real-time experiments are conducted to validate the effectiveness of the proposed algorithm compared with other optimization techniques, such as GA and PSO. <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">Note to Practitioners</i> —Cooperative unmanned systems have drawn significant interests in military and civilian applications. During missions’ execution, it is of great importance for cooperative unmanned systems to have fault-tolerance capabilities for achieving the desired mission when faults occur in one or more team members. A challenging problem is how to detect and isolate the fault and how to mitigate the fault effects on the whole mission. This article presents a fault-tolerant formation control strategy in the case of severe actuator fault occurrence in a team of wheeled mobile robots.

Fault-tolerant formation control of stochastic nonlinear multi-agent systems with time-varying weighted topology

In this paper, the fault-tolerant formation control of nonlinear stochastic multi-agent systems in the presence of actuator faults, disturbances, and time-varying weighted topology is considered. While most traditional fault-tolerant control methods in the literature use fixed weights on the topology edges, in this study these weights are considered time-varying using a pre-designed function, which allows formulating the system more realistically. Moreover, in contrast with previous works on fault-tolerant multi-agent systems, in this study, the model of the agents is considered to be stochastic in general. Furthermore, the actuators of the agents are considered to have a time-varying fault of additive and multiplicative types. A passive and an active fault-tolerant controllers are designed based on the back-stepping sliding-mode approach. In the passive method, a constant robust controller is proposed using an upper bound of the faults while, in the active controller, the additive and multiplicative faults are estimated using adaptive laws. The active and passive fault-tolerant controllers guarantee that the formation errors converge to a bounded region near the origin in a mean-square sense and all of the existing signals in the closed-loop system remain bounded in probability. The results of the formation control are extended to consensus control as well. Finally, a stochastic multi-aircraft model and an RLC circuit with stochastic part are used as two case studies to illustrate the effectiveness of the proposed design method.

Robust Fault-Tolerant Formation Control for Tail-Sitters in Aggressive Flight Mode Transitions

In this paper, the fault-tolerant time-varying formation control problem for a group of tail-sitters with multiple actuator faults and uncertainties is studied. A robust distributed fault-tolerant formation control strategy is developed to achieve aggressive time-varying formation flying in flight mode transitions. For each tail-sitter, the designed controller can be divided into an inner attitude controller and an outer position controller to govern the rotational and translational motions, respectively. The information of the actuator faults does not need to be identified online and the tracking errors of the global closed-loop control system can converge into a given neighborhood of the origin in a finite time. Simulation results are presented to show the effectiveness of the proposed control strategy.

Adaptive Distributed Fault-tolerant Formation Control for Multi-robot Systems under Partial Loss of Actuator Effectiveness

This paper presents an adaptive distributed fault-tolerant formation control for multi-robot systems. Both the kinematics and dynamics of differential wheeled mobile robots are considered. In particular, the problem caused by actuator faults is investigated. Based on dynamic surface control techniques, adaptive formation controllers can be obtained under a directed communication network. The closed-loop stability is guaranteed by using Lyapunov stability analysis such that all followers can exponentially converge to a leader-follower formation pattern. Simulation and experimental results illustrate that the desired formation pattern can be preserved for a group of wheeled robots subject to unknown uncertainties and actuator faults.

Finite‐time fault‐tolerant formation control for multiquadrotor systems with actuator fault

SummaryThis paper investigates the distributed tracking control of a group of underactuated quadrotors in the presence of actuator faults in three‐dimensional space. Using consensus protocol and sliding mode algorithm, a distributed finite‐time fault‐tolerant formation control scheme is developed. The whole closed‐loop system is composed by position loop, attitude loop, and propeller speed loop. A propeller speed fault‐tolerant controller is developed to deal with the unexpected faults of quadrotors. The finite‐time stability of the closed‐loop system is guaranteed through Lyapunov analysis. Finally, the efficiency of the proposed algorithm is illustrated by some numerical simulations.