Adaptive Leader-Follower Consensus Control of Multiple Flexible Manipulators With Actuator Failures and Parameter Uncertainties

In this paper,the leader-follower consensus problem for a multiple flexible manipulator network with actuator failures,parameter uncertainties,and unknown time-varying boundary disturbances is addressed.The purpose of this study is to develop distributed controllers utilizing local interactive protocols that not only suppress the vibration of each flexible manipulator but also achieve consensus on joint angle position between actual followers and the virtual leader.Following the accomplishment of the reconstruction of the fault terms and parameter uncertainties,the adaptive neural network method and parameter estimation technique are employed to compensate for unknown items and bounded disturbances.Furthermore,the Lyapunov stability theory is used to demonstrate that followers’angle consensus errors and vibration deflections in closed-loop systems are uniformly ultimately bounded.Finally,the numerical simulation results confirm the efficacy of the proposed controllers.

Piecewise model-based adaptive compensation control for high-speed trains with unknown actuator failures

In order to deal with the uncertainties caused by different operation conditions and unknown actuator failures of high-speedtrains,an adaptive failures compensation control scheme is designed based on the piecewise model.A piecewise constant model is introduced to describe the variable system parameters caused by the variable operation environments,and a multiple-particle plecewise model of high-speed trains,with unknown actuator failures,is then established.An adaptive failure compensation controller is developed for the multiple-particle piecewise constant model,by using a direct model refering to the adaptive control method.Such an adaptive controller can not only compensate the uncertainties from unknown actuator failures,but also effectively deal with the uncertainties caused by different operating conditions.Finally,a CRH380A high-speed train model is taken as the controlled object for the simulation study.The simulation results show that the proposed controller ensures the desired system performance in the presence of unknown actuator failures and uncertain operation conditions.

Robust stability analysis of switched uncertain systems with multiple time-varying delays and actuator failures

In this paper,the robust stability issue of switched uncertain multidelay systems resulting from actuator failures is considered.Based on the average dwell time approach,a set of suitable switching signals is designed by using the total activation time ratio between the stable subsystem and the unstable one.It is first proven that the resulting closed-loop system is robustly exponentially stable for some allowable upper bound of delays if the nominal system with zero delay is exponentially stable under these switching laws.Particularly,the maximal upper bound of delays can be obtained from the linear matrix inequalities.At last,the effectiveness of the proposed method is demonstrated by a simulation example.

Non-fragile robust H_(∞)control of nonlinear networked control systems with time-varying delay and unknown actuator failures

Purpose-This paper is concerned with non-fragile robust H_(∞)control problems for nonlinear networked control systems(NCSs)with time-varying delay and unknown actuator failures.The paper aims to discuss these issues.Design/methodology/approach-The system parameters are allowed to have time-varying uncertainties and the actuator faults are unknown but whose upper and lower bounds are known.By using some lemmas,uncertainties can be replaces with the known values.By taking the exogenous disturbance and network transmission delay into consideration,a delay nonlinear system model is constructed.Findings-Based on Lyapunov stability theory,linear matrix inequalities(LMIs)and free weighting matrix methods,the sufficient conditions for the existence of the non-fragile robust H_(∞)controller gain are derived and which can obtained by solving the LMIs.Finally,a numerical example is provided to illustrate the effectiveness of the proposed methods.Originality/value-The introduced approach is interesting for NCSs with time-varying delay and unknown actuator failures.

Event-triggered robust control for networked control systems with actuator failures and time-varying transmission delays

Purpose–The purpose of this paper is with robust control problem for event-triggered networked control systems(NCSs)with actuator failures and time-varying transmission delays.Design/methodology/approach–A random sequence is introduced to describe the actuator faults,and a novel event-triggering communication scheme is adopted in the sensor-to-controller channel.By taking the event-triggered mechanism and network transmission delay into consideration,a delay system model is constructed.Findings–Based on Lyapunov stability theory and free weighting matrix method,the feasibility criteria for co-designing both the controller gain and the trigger parameters are derived.Finally,a simulation example is exploited to demonstrate the effectiveness of the proposed linear matrix inequalities(LMIs)approach.Originality/value–The introduced approach is interesting for NCSs with actuator failures and timevarying transmission delays.

A Robust Roll Stabilization Controller with Aerodynamic Disturbance and Actuator Failure Consideration

Combining adaptive theory with an advanced second-order sliding mode control algorithm,a roll stabilization controller with aerodynamic disturbance and actuator failure consideration for spinning flight vehicles is proposed in this paper.The presented controller is summarized as an“observer-controller”system.More specifically,an adaptive secondorder sliding mode observer is presented to select the proper design parameters and estimate the knowledge of aerodynamic disturbance and actuator failure,while the proposed roll stabilization control scheme can drive both roll angle and rotation rate smoothly converge to the desired value.Theoretical analysis and numerical simulation results demonstrate the effectiveness of the proposed controller.

Sliding-Mode-Based Attitude Tracking Control of Spacecraft Under Reaction Wheel Uncertainties

The attitude tracking operations of an on-orbit spacecraft with degraded performance exhibited by potential actuator uncertainties(including failures and misalignments) can be extraordinarily challenging. Thus, the control law development for the attitude tracking task of spacecraft subject to actuator(namely reaction wheel) uncertainties is addressed in this paper. More specially, the attitude dynamics model of the spacecraft is firstly established under actuator failures and misalignment(without a small angle approximation operation). Then, a new non-singular sliding manifold with fixed time convergence and anti-unwinding properties is proposed, and an adaptive sliding mode control(SMC) strategy is introduced to handle actuator uncertainties, model uncertainties and external disturbances simultaneously. Among this, an explicit misalignment angles range that could be treated herein is offered. Lyapunov-based stability analyses are employed to verify that the reaching phase of the sliding manifold is completed in finite time, and the attitude tracking errors are ensured to converge to a small region of the closest equilibrium point in fixed time once the sliding manifold enters the reaching phase. Finally, the beneficial features of the designed controller are manifested via detailed numerical simulation tests.

Impact angle constrained fuzzy adaptive fault tolerant IGC method for Ski-to-Turn missiles with unsteady aerodynamics and multiple disturbances

An impact angle constrained fuzzy adaptive fault tolerant integrated guidance and control method for Ski-to-Turn(STT)missiles subject to unsteady aerodynamics and multiple disturbances is proposed.Unsteady aerodynamics appears when flight vehicles are in a transonic state or confronted with unstable airflow.Meanwhile,actuator failures and multisource model uncertainties are introduced.However,the boundaries of these multisource uncertainties are assumed unknown.The target is assumed to execute high maneuver movement which is unknown to the missile.Furthermore,impact angle constraint puts forward higher requirements for the interception accuracy of the integrated guidance and control(IGC)method.The impact angle constraint and the precise interception are established as the object of the IGC method.Then,the boundaries of the lumped disturbances are estimated,and several fuzzy logic systems are introduced to compensate the unknown nonlinearities and uncertainties.Next,a series of adaptive laws are developed so that the undesirable effects arising from unsteady aerodynamics,actuator failures and unknown uncertainties could be suppressed.Consequently,an impact angle constrained fuzzy adaptive fault tolerant IGC method with three loops is constructed and a perfect hit-to-kill interception with specified impact angle can be implemented.Eventually,the numerical simulations are conducted to verify the effectiveness and superiority of the proposed method.

Adaptive fault-tolerant control of high-speed maglev train suspension system with partial actuator failure: design and experiments

High-speed maglev trains will play an important role in the high-speed transportation system in the near future.However,under the conditions of strong magnetic fields and continuous operation,the actuators of the high-speed maglev train suspension system are prone to lose partial effectiveness,which makes the suspension control problem challenging.In addition,most existing fault-tolerant control(FTC)methods for suspension systems require linearization around the equilibrium points during the controller design or stability analysis.Therefore,from a practical perspective,this study presents a novel nonlinear FTC strategy with adaptive compensation for high-speed maglev train suspension systems.First,a nonlinear dynamic model of the suspension system based on join-structure is established and the actuator failures are described.Then,a nonlinear fault-tolerant suspension control law with an adaptive update law is designed to achieve stable suspension against partial actuator failure.The Lyapunov theory and extended Barbalat lemma are utilized to rigorously prove the closed-loop asymptotic stability even if there is partial actuator failure,without any approximation to the original nonlinear dynamics.Finally,hardware experimental results are included to demonstrate the effectiveness of the proposed approach.

Distributed Fault-Tolerant Control of Uncertain Multi-Agent Systems with Connectivity Maintenance

In this paper,a distributed cooperative control protocol is presented to deal with actuator failures of multi-agent systems in the presence of connectivity preservation.With the developed strategy,each agent can track the reference trajectory of the leader in the presence of actuator failures,disturbances and uncertainties.The connectivity of the multi-agent system can always be ensured during the control process.To achieve the aforementioned control objectives,a potential function is introduced to the distributed adaptive fault-tolerant control algorithm to preserve the initial connected network among the agents.The uncertainty of the multi-agent system,which is allowed to be described by discontinuous functions,is approximated and compensated using the fuzzy logic system.The asymptotic stability of the closed-loop system is demonstrated through the use of Cellina’s approximate selection theorem of nonsmooth analysis.Due to the developed adaptive laws,the upper bound of the disturbance is allowed to be uncertain,which facilitates the implementation of the control scheme.Finally,simulation results are provided to verify the effectiveness of the proposed control scheme.

Direct adaptive actuator failure compensation control:a tutorial

A resilient control system is expected to have the capacity to restore the desired system stability and tracking performance in the presence of uncertain system faults such as actuator failures.While redundant actuators are used for actuator failure accommodation,uncertain actuator failures,whose failure time,pattern,and values may be unknown,can bring new challenges to feedback control design as such uncertain failures can introduce large structural,parametric,and actuation uncertainties.Two technical issues are associated with using redundant actuators:how redundant actuators should be coordinated for effective failure compensation control,and how a feedback control law should be adaptively designed to compensate uncertain actuator failures.In this paper,we present a tutorial on direct adaptive failure compensation-based solutions to these issues for different types of control systems:state tracking using state feedback,output tracking using state feedback or output feedback,for linear,non-linear,and multi-input multi-output systems.We give an overview on such adaptive actuator failure compensation designs which have special capacities to effectively use actuation redundancy to handle uncertain actuator failures,using either direct or indirect adaptive control approaches for direct adaptive actuator failure compensation without explicit failure detection,for fast and effective failure accommodation.

Robust Adaptive Actuator Failure Compensation for a Class of Uncertain Nonlinear Systems

This paper presents a robust adaptive state feedback control scheme for a class of parametric-strict-feedback nonlinear systems in the presence of time varying actuator failures. The designed adaptive controller compensates a general class of actuator failures without any need for explicit fault detection. The parameters, times, and patterns of the considered failures are completely unknown. The proposed controller is constructed based on a backstepping design method. The global boundedness of all the closed-loop signals is guaranteed and the tracking error is proved to converge to a small neighborhood of the origin. The proposed approach is employed for a two-axis positioning stage system as well as an aircraft wing system. The simulation results show the correctness and effectiveness of the proposed robust adaptive actuator failure compensation approach.

Reliable control of discrete-time linear systems with actuator failure

A sufficient condition is given for robust stability of a discrete linear system in which an arbitrary portion of input channel is permanently attenuated or disconnected due to actuator fault.The partial disconnection/attenuation of the control input,is modelled as uncertainty and dealt with via a robust control method.The proposed method enables one to design a controller in such a way that the closed loop system remains stable when any combination of input signals is disconnected if the open loop system is stable and fulfils some additional properties.It is shown that the linear quadratic regulator can guarantee reliable closed loop with some specific choices for weighting matrices.The result is extended to unstable systems by assuming additional constraints on the failed actuators.Compared to previously established results,the proposed conditions are easier to verify and applicable to a wider class of systems.An example is also included.

Adaptive controller design for uncertain singular systems with actuator failure

In this paper,the problem of model reference adaptive controller design with actuator failure is solved for a series of uncertain singular systems.The research on partial actuator failure is relatively mature and it is necessary to solve the problem of how to guarantee the system performance when the actuator fails completely.For this reason,we treat the system with actuator failure as a switching system with two subsystems and then solve the stability analysis problem of the error switching system.The emphasis is to design the adaptive controller by some sufficient linear matrices inequalities(LMIs)conditions and obtain the global stability criterion of the error switching system through the resident time method.Finally,the proposed method is applied to HiMAT aircraft to illustrate the feasibility and effectiveness of this kind of problem.