The finite/fixed-time stabilization and tracking control is currently a hot field in various systems since the faster convergence can be obtained. By contrast to the asymptotic stability,the finite-time stability poss...The finite/fixed-time stabilization and tracking control is currently a hot field in various systems since the faster convergence can be obtained. By contrast to the asymptotic stability,the finite-time stability possesses the better control performance and disturbance rejection property. Different from the finite-time stability, the fixed-time stability has a faster convergence speed and the upper bound of the settling time can be estimated. Moreover, the convergent time does not rely on the initial information.This work aims at presenting an overview of the finite/fixed-time stabilization and tracking control and its applications in engineering systems. Firstly, several fundamental definitions on the finite/fixed-time stability are recalled. Then, the research results on the finite/fixed-time stabilization and tracking control are reviewed in detail and categorized via diverse input signal structures and engineering applications. Finally, some challenging problems needed to be solved are presented.展开更多
The adaptive fixed-time consensus problem for a class of nonlinear multi-agent systems(MASs)with actuator faults is considered in this paper.To approximate the unknown nonlinear functions in MASs,radial basis function...The adaptive fixed-time consensus problem for a class of nonlinear multi-agent systems(MASs)with actuator faults is considered in this paper.To approximate the unknown nonlinear functions in MASs,radial basis function neural networks are used.In addition,the first order sliding mode differentiator is utilized to solve the“explosion of complexity”problem,and a filter error compensation method is proposed to ensure the convergence of filter error in fixed time.With the help of the Nussbaum function,the actuator failure compensation mechanism is constructed.By designing the adaptive fixed-time controller,all signals in MASs are bounded,and the consensus errors between the leader and all followers converge to a small area of origin.Finally,the effectiveness of the proposed control method is verified by simulation examples.展开更多
To achieve the fast convergence and tracking precision of a robotic upper-limb exoskeleton,this paper proposes an observer-based integrated fixed-time control scheme with a backstepping method.Firstly,a typical 5 DoF(...To achieve the fast convergence and tracking precision of a robotic upper-limb exoskeleton,this paper proposes an observer-based integrated fixed-time control scheme with a backstepping method.Firstly,a typical 5 DoF(degrees of freedom)dynamics is constructed by Lagrange equations and processed for control purposes.Secondly,second-order sliding mode controllers(SOSMC)are developed and novel sliding mode surfaces are introduced to ensure the fixed-time convergence of the human-robot system.Both the reaching time and settling time are proved to be bounded with certain values independent of initial system conditions.For the purpose of rejecting the matched and unmatched disturbances,nonlinear fixed-time observers are employed to estimate the exact value of disturbances and compensate the controllers online.Ultimately,the synthesis of controllers and disturbance observers is adopted to achieve the excellent tracking performance and simulations are given to verify the effectiveness of the proposed control strategy.展开更多
High-speed Electromagnetic Suspension(EMS)train is continuously impacted by the irregularity of the track,which worsens the levitation performance of the train.In this paper,a composite control scheme for the EMS is p...High-speed Electromagnetic Suspension(EMS)train is continuously impacted by the irregularity of the track,which worsens the levitation performance of the train.In this paper,a composite control scheme for the EMS is proposed to suppress track irregularities by integrating a Refined Disturbance Observer(RDO)and a Prescribed Performance Fixed-Time Controller(PPFTC).The RDO is designed to estimate precisely the track irregularities and lumped disturbances with uncertainties and exogenous disturbances in the suspension system,and reduce input chattering by applying to the disturbance compensation channel.PPFTC is designed to converge the suspension air gap error to equilibrium point with prescribed performance by completing error conversion,and solve the fast dynamic issue of EMS.And the boundary of overshoot and steady-state is limited in the ranged prescribed.A theoretical analysis is conducted on the stability of the proposed control method.Finally,the effectiveness and reasonability of the proposed composite anti-disturbance control scheme is verified by simulation results.展开更多
This paper is dedicated to solving the problem of adaptive fuzzy fault-tolerant tracking control for a class of time-varying high-order uncertain nonlinear systems.The motivation comes from how to construct a compact ...This paper is dedicated to solving the problem of adaptive fuzzy fault-tolerant tracking control for a class of time-varying high-order uncertain nonlinear systems.The motivation comes from how to construct a compact set large enough in which the approximation of any unknown continuous function by a fuzzy logic system(FLS)is effective while compensating sensor/actuator faults and external disturbances.The difficulty is to verify the boundedness of closed-loop signals on the constructed compact set and to reduce the number of the variables of the fuzzy membership functions as many as possible.By a new lemma,linear/nonlinear terms are introduced in adaptive laws to dominate unknown residual terms.With adding a power integrator method,a unified fault-tolerant controller is designed to drive the tracking error to converge to a small compact set of the origin within a fixed time,regardless of whether the system suffers from faults and disturbances.Superior to the existing results,in the presence of time-varying factors the scheme of this paper clarifies the logical relationship between the compactness of the approximation and the boundedness of the state variables.Finally,the application of control strategy is demonstrated by numerical/practical examples.展开更多
This paper considers the practical fixed-time tracking control problem for a state constrained pure-feedback nonlinear system.A new barrier function is first proposed to handle various asymmetric time-varying constrai...This paper considers the practical fixed-time tracking control problem for a state constrained pure-feedback nonlinear system.A new barrier function is first proposed to handle various asymmetric time-varying constraints and unify the cases with and without state constraints.Then a low-cost neural network based adaptive fixed-time controller is constructed by further combining the dynamic surface control,which overcomes the technical problems of overparametrization and singularity in the backstepping procedure.The proposed design guarantees that the tracking error converges to a small neighbourhood of zero in a fixed time while satisfying the state constraints as a priority task without imposing feasibility conditions on the virtual controllers.Simulation results validate the effectiveness of the proposed adaptive fixed-time tracking control strategy.展开更多
In this paper,the problem of non-singular fixed-time control with prescribed performance is studied for multi-agent systems characterized by uncertain states,nonlinearities,and nonstrict feedback.To mitigate the nonli...In this paper,the problem of non-singular fixed-time control with prescribed performance is studied for multi-agent systems characterized by uncertain states,nonlinearities,and nonstrict feedback.To mitigate the nonlinearity,a fuzzy logic algorithm is applied to approximate the intrinsic dynamics of the system.Furthermore,a fuzzy logic system state observer based on leader state information is designed to address the partial unob-servability of followers.Subsequently,the power integral method is incorporated into the backstepping approach to avoid singularities in the fixed-time controller.A command filter method is introduced into the standard backstepping approach to reduce the computational complexity of controller design.Then,a non-singular fixed-time adaptive control strategy with prescribed performance is proposed by constraining the tracking error within a prescribed range.Rigorous theoretical analysis ensures the convergence of consensus error in the multi-agent system to the prescribed performance region within a fixed time.Finally,the practicality of the algorithm is validated through numerical simulations.展开更多
This paper studies the dynamic and control problems of space tether system(STS)after capturing space debris.The fully integrated system post-capture is referred to as space tether debris-assembly(STDA),while the syste...This paper studies the dynamic and control problems of space tether system(STS)after capturing space debris.The fully integrated system post-capture is referred to as space tether debris-assembly(STDA),while the system comprising the capture device and debris is termed the debris assembly.A significant challenge in stabilizing STS after debris capture lies in the residual angular momentum of the debris,which,if unmitigated,coupled with the relative angular velocity difference between the debris and the tether,can lead to detrimental effects such as tether entanglement and system destabilization.Furthermore,STDA system experiences unknown mass parameter variations that exacerbate control difficulties.To address these challenges,this paper proposes a nonlinear control strategy designed to rapidly stabilize the attitude motion of the end body,despite uncertainties in mass parameters and boundary constraints.A dynamic model of STDA system,encompassing the host spacecraft,tether,capture device,and space debris,is formulated based on Lagrangian equation.This model accounts for the relative attitude motion between the debris-assembly and the tether,as well as the attitude dynamics of the tether itself,thereby enabling an analysis of disturbances arising from unknown mass parameters and collision-induced angular motion.To mitigate these disturbances,a sliding mode disturbance observer is developed to compensate for dynamic uncertainties associated with the space debris'unknown mass.Furthermore,an error transformation is performed,and a prescribed performance controller is designed to ensure that the system remains within predefined boundaries during stabilization.The effectiveness of the proposed method is validated through numerical simulations.展开更多
This paper is dedicated to fixed-time passivity and synchronization for multi-weighted spatiotemporal directed networks.First,to achieve fixed-time passivity,a type of decentralized power-law controller is developed,i...This paper is dedicated to fixed-time passivity and synchronization for multi-weighted spatiotemporal directed networks.First,to achieve fixed-time passivity,a type of decentralized power-law controller is developed,in which only one parameter needs to be adjusted in the power-law terms;this greatly decreases the inconvenience of parameter adjustment.Second,several fixed-time passivity criteria with LMI forms are derived by using a Gauss divergence theorem to deal with the spatial diffusion of nodes and by applying the Hölder’s inequality to dispose rigorously the power-law term greater than one in the designed control scheme;this improves the previous theoretical analysis.Additionally,the fixed-time synchronization of spatiotemporal directed networks with multi-weights is addressed as a direct result of fixed-time strict passivity.Finally,a numerical example is presented in order to show the validity of the theoretical analysis.展开更多
This paper presents an adaptive multi-agent coordination(AMAC)strategy suitable for complex scenarios,which only requires information exchange between neighbouring robots.Unlike traditional multi-agent coordination me...This paper presents an adaptive multi-agent coordination(AMAC)strategy suitable for complex scenarios,which only requires information exchange between neighbouring robots.Unlike traditional multi-agent coordination methods that are solved by neural dynamics,the proposed strategy displays greater flexibility,adaptability and scalability.Furthermore,the proposed AMAC strategy is reconstructed as a time-varying complex-valued matrix equation.By introducing a dynamic error function,a fixed-time convergent zeroing neural network(FTCZNN)model is designed for the online solution of the AMAC strategy,with its convergence time upper bound derived theoretically.Finally,the effectiveness and applicability of the coordination control method are demonstrated by numerical simulations and physical experiments.Numerical results indicate that this method can reduce the formation error to the order of 10^(-6)within 1.8 s.展开更多
In this paper,a class of discontinuous Cohen-Grossberg neural networks with timevarying delays is considered.Firstly,under the extended Filippov differential inclusions framework,the problem of periodic solutions of t...In this paper,a class of discontinuous Cohen-Grossberg neural networks with timevarying delays is considered.Firstly,under the extended Filippov differential inclusions framework,the problem of periodic solutions of the considered neural networks with more relaxed conditions imposed on the amplification functions is analyzed by using set-valued mapping and Kakutani's fixed point theorem,which has rarely been used to study such problem.Secondly,the fixed-time synchronization of the error system of the considered neural networks is also investigated by designing a novel control strategy,which can improve not only the previous ones with sign function greatly,but also can reduce the chattering phenomenon.Finally,two numerical examples are presented to further illustrate the validity of the obtained results.展开更多
This paper presents an investigation on the target-guided coordinated control(TACC)of unmanned surface vehicles(USVs).In the scenario of tracking non-cooperative targets,the status information of the target can only b...This paper presents an investigation on the target-guided coordinated control(TACC)of unmanned surface vehicles(USVs).In the scenario of tracking non-cooperative targets,the status information of the target can only be obtained by some USVs.In order to achieve semi-encirclement tracking of noncooperative targets under maritime security conditions,a fixed-time tracking control method based on dynamic surface control(DSC)is proposed in this paper.Firstly,a novel TACC architecture with decoupled kinematic control law and decoupled kinetic control law was designed to reduce the complexity of control system design.Secondly,the proposed DSC-based target-guided kinematic control law including tracking points pre-allocation strategy and sigmoid artificial potential functions(SigAPFs)can avoid collisions during tracking process and optimize kinematic control output.Finally,a fixed-time TACC system was proposed to achieve fast convergence of kinematic and kinetics errors.The effectiveness of the proposed TACC approach in improving target tracking safety and reducing control output chattering was verified by simulation comparison results.展开更多
This paper investigates modified fixed-time synchronization(FxTS)of complex networks(CNs)with time-varying delays based on continuous and discontinuous controllers.First,for the sake of making the settling time(ST)of ...This paper investigates modified fixed-time synchronization(FxTS)of complex networks(CNs)with time-varying delays based on continuous and discontinuous controllers.First,for the sake of making the settling time(ST)of FxTS is independent of the initial values and parameters of the CNs,a modified fixed-time(FxT)stability theorem is proposed,where the ST is determined by an arbitrary positive number given in advance.Then,continuous controller and discontinuous controller are designed to realize the modified FxTS target of CNs.In addition,based on the designed controllers,CNs can achieve synchronization at any given time,or even earlier.And control strategies effectively solve the problem of ST related to the parameters of CNs.Finally,an appropriate simulation example is conducted to examine the effectiveness of the designed control strategies.展开更多
This paper presents an entire fixed-time disturbance observer-based global terminal switching sliding mode control of robot manipulators,which has inner and external uncertainties.The entire fixed-time disturbance obs...This paper presents an entire fixed-time disturbance observer-based global terminal switching sliding mode control of robot manipulators,which has inner and external uncertainties.The entire fixed-time disturbance observer-based global terminal switching sliding mode control has the global finite-time reaching characteristic,the property that system convergence time can be prescribed,and the global robustness to uncertainties,with the entire fixed-time disturbance observer that accurately estimates uncertainties after a fixed time,despite the initial state.The joints of the control system can arrive at the prescribed joint angular position at the predefined joint angular speed at the prescribed time.展开更多
This paper investigates the distributed fixed-time attitude coordinated control problem for multiple spacecraft subject to actuator saturation under the directed topology. First, a distributed fixed-time observer is p...This paper investigates the distributed fixed-time attitude coordinated control problem for multiple spacecraft subject to actuator saturation under the directed topology. First, a distributed fixed-time observer is presented for each follower spacecraft to estimate the leader spacecraft’s states. Compared with the commonly used fixed-time observer, the settling time of the proposed fixed-time observer can be easily adjusted by some free design parameters. Next, a distributed fixed-time control scheme is derived by using the estimates of the leader spacecraft’s states and the adding a power integrator technique. When considering actuator saturation, an auxiliary system is utilized to compensate the saturation. Further, a rigorous theoretical proof is provided to show that the practical fixed-time stability of the closed-loop system is ensured. Finally, simulation results illustrate the benefits and effectiveness of the developed control scheme.展开更多
This paper investigates the heading tracking problem of surface vehicles with unknown model parameters.Based on finite/fixed-time control theories and in the context of command filtered control,two novel adaptive cont...This paper investigates the heading tracking problem of surface vehicles with unknown model parameters.Based on finite/fixed-time control theories and in the context of command filtered control,two novel adaptive control laws are developed by which the vehicle can track the desired heading within settling time with all signals of the closed-loop system are uniformly bounded.The effectiveness and performance of the schemes are demonstrated by simulations and comparison studies.展开更多
This paper studies the fixed-time output-feedback control for a class of linear systems subject to matched uncertainties.To estimate the uncertainties and system states,we design a composite observer which consists of...This paper studies the fixed-time output-feedback control for a class of linear systems subject to matched uncertainties.To estimate the uncertainties and system states,we design a composite observer which consists of a high-order sliding mode observer and a Luenberger observer.Then,a robust output-feedback controller with fixed-time convergence guarantee is constructed.Rigorous theoretical proof shows that with the proposed controller,the system states can converge to zero in fixed-time free of the initial conditions.Finally,simulation comparison with existing algorithms is given.Simulation results verify the effectiveness of the proposed controller in terms of its fixed-time convergence and perfect disturbance rejection.展开更多
Fixed-time control of traffic signals pursues the regulation of phases based on historical data of traffic demand, in this way, neglecting of the random arrival rates of traffic flow on different intersection streams ...Fixed-time control of traffic signals pursues the regulation of phases based on historical data of traffic demand, in this way, neglecting of the random arrival rates of traffic flow on different intersection streams causes increasing of the stops and delays and fuel consumption at the same time. Coordinated semi-actuated control due to ability to respond traffic demands on both main and secondary directions, based on road detector registration saves the coordinated features, serving the unused time to the main road, while the secondary clears early. In this paper, the authors analyzed and explained comparatively the results of LOS （level of service） parameters of the current state of control （fixed-time） with the proposed control （semi-actuated coordinated） of the artery of length 2,348 km consisted of four signalized T intersections. Highway Capacity Manual and Synchro/Sim Traffic software are used for analysis and optimization of parameters in this paper.展开更多
In this paper,we consider the fixed-time stabilization control problem of quantum systems modeled by Schrodinger equations.Firstly,the Lyapunov-based fixed-time stability criterion is extended to finitedimensional clo...In this paper,we consider the fixed-time stabilization control problem of quantum systems modeled by Schrodinger equations.Firstly,the Lyapunov-based fixed-time stability criterion is extended to finitedimensional closed quantum systems in the form of coherence vectors.Then for a two-level quantum system with single control input,a non-smooth fractional-order control law is designed using the relative state distance.By integrating the fixed-time Lyapunov control technique and the bi-limit homogeneity theory,the quantum system is proved to be stabilized to an eigenstate of the inherent Hamiltonian in a fixed time.Comparing with existing methods in quantum system control,the proposed approach can guarantee stabilization in a fixed time without depending on the initial states.展开更多
This paper presents a fixed-time cooperative gui-dance method with impact angle constraints for multiple flight vehicles (MFV) to address the challenges of intercepting large maneuvering targets with difficulty and lo...This paper presents a fixed-time cooperative gui-dance method with impact angle constraints for multiple flight vehicles (MFV) to address the challenges of intercepting large maneuvering targets with difficulty and low precision. A coopera-tive guidance model is proposed, transforming the cooperative interception problem into a consensus problem based on the remaining flight time of the flight vehicles. First, the impact angle constraint is converted into the line of sight (LOS) angle con-straint, and a new fixed-time convergent non-singular terminal sliding surface is introduced, which resolves the singularity issue of the traditional sliding surfaces. With this approach, LOS angle rate and normal overloads can converge in fixed time, ensuring that the upper bound of the system convergence time is not affected by the initial value of the system. Furthermore, the maneuvering movement of the target is considered as a system disturbance, and an extended state observer is employed to estimate and compensate for it in the guidance law. Lastly, by applying consensus theory and distributed communication topology, the remaining flight time of each flight vehicle is syn-chronized to ensure that they intercept the target simulta-neously with different impact angles. Simulation experiments are conducted to validate the effectiveness of the proposed cooper-ative interception and guidance method.展开更多
基金partially supported by the National Natural Science Foundation of China(62003097,62121004,62033003,62073019)the Local Innovative and Research Teams Project of Guangdong Special Support Program(2019BT02X353)+2 种基金the Key Area Research and Development Program of Guangdong Province(2021B0101410005)the Joint Funds of Guangdong Basic and Applied Basic Research Foundation(2019A1515110505)。
文摘The finite/fixed-time stabilization and tracking control is currently a hot field in various systems since the faster convergence can be obtained. By contrast to the asymptotic stability,the finite-time stability possesses the better control performance and disturbance rejection property. Different from the finite-time stability, the fixed-time stability has a faster convergence speed and the upper bound of the settling time can be estimated. Moreover, the convergent time does not rely on the initial information.This work aims at presenting an overview of the finite/fixed-time stabilization and tracking control and its applications in engineering systems. Firstly, several fundamental definitions on the finite/fixed-time stability are recalled. Then, the research results on the finite/fixed-time stabilization and tracking control are reviewed in detail and categorized via diverse input signal structures and engineering applications. Finally, some challenging problems needed to be solved are presented.
基金the National Natural Science Foundation of China(62003093,62203119,62033003,62121004)the China National Postdoctoral Program(BX20220095,2022M710826)+1 种基金the Natural Science Foundation of Guangdong Province(2022A1515011506)the Guangzhou Science and Technology Planning Project(202102020586)。
文摘The adaptive fixed-time consensus problem for a class of nonlinear multi-agent systems(MASs)with actuator faults is considered in this paper.To approximate the unknown nonlinear functions in MASs,radial basis function neural networks are used.In addition,the first order sliding mode differentiator is utilized to solve the“explosion of complexity”problem,and a filter error compensation method is proposed to ensure the convergence of filter error in fixed time.With the help of the Nussbaum function,the actuator failure compensation mechanism is constructed.By designing the adaptive fixed-time controller,all signals in MASs are bounded,and the consensus errors between the leader and all followers converge to a small area of origin.Finally,the effectiveness of the proposed control method is verified by simulation examples.
基金supported by National Natural Science Foundation of China (Nos. 61703134, 61703135, 61773151, 61503118 and 61871173)Natural Science Foundation of Hebei Province (Nos. F2015202150, F2016202327 and F2018202279)+3 种基金Natural Science Foundation of Tianjin (No. 17JCQNJC04400)the Foundation of Hebei Educational Committee (Nos. QN2015068 and ZD2016071)the Colleges and Universities in Hebei Province Science and Technology Research Youth Fund (No. ZC2016020)the Graduate Innovation Funding Project of Hebei Province (No. CXZZBS2017038)
文摘To achieve the fast convergence and tracking precision of a robotic upper-limb exoskeleton,this paper proposes an observer-based integrated fixed-time control scheme with a backstepping method.Firstly,a typical 5 DoF(degrees of freedom)dynamics is constructed by Lagrange equations and processed for control purposes.Secondly,second-order sliding mode controllers(SOSMC)are developed and novel sliding mode surfaces are introduced to ensure the fixed-time convergence of the human-robot system.Both the reaching time and settling time are proved to be bounded with certain values independent of initial system conditions.For the purpose of rejecting the matched and unmatched disturbances,nonlinear fixed-time observers are employed to estimate the exact value of disturbances and compensate the controllers online.Ultimately,the synthesis of controllers and disturbance observers is adopted to achieve the excellent tracking performance and simulations are given to verify the effectiveness of the proposed control strategy.
基金supported by the National Natural Science Foundation of China(Grant 62273029).
文摘High-speed Electromagnetic Suspension(EMS)train is continuously impacted by the irregularity of the track,which worsens the levitation performance of the train.In this paper,a composite control scheme for the EMS is proposed to suppress track irregularities by integrating a Refined Disturbance Observer(RDO)and a Prescribed Performance Fixed-Time Controller(PPFTC).The RDO is designed to estimate precisely the track irregularities and lumped disturbances with uncertainties and exogenous disturbances in the suspension system,and reduce input chattering by applying to the disturbance compensation channel.PPFTC is designed to converge the suspension air gap error to equilibrium point with prescribed performance by completing error conversion,and solve the fast dynamic issue of EMS.And the boundary of overshoot and steady-state is limited in the ranged prescribed.A theoretical analysis is conducted on the stability of the proposed control method.Finally,the effectiveness and reasonability of the proposed composite anti-disturbance control scheme is verified by simulation results.
基金supported by National Natural Science Foundation of China[grant number 62173208]Taishan Scholar Project of Shandong Province of China[grant number tsqn202103061]。
文摘This paper is dedicated to solving the problem of adaptive fuzzy fault-tolerant tracking control for a class of time-varying high-order uncertain nonlinear systems.The motivation comes from how to construct a compact set large enough in which the approximation of any unknown continuous function by a fuzzy logic system(FLS)is effective while compensating sensor/actuator faults and external disturbances.The difficulty is to verify the boundedness of closed-loop signals on the constructed compact set and to reduce the number of the variables of the fuzzy membership functions as many as possible.By a new lemma,linear/nonlinear terms are introduced in adaptive laws to dominate unknown residual terms.With adding a power integrator method,a unified fault-tolerant controller is designed to drive the tracking error to converge to a small compact set of the origin within a fixed time,regardless of whether the system suffers from faults and disturbances.Superior to the existing results,in the presence of time-varying factors the scheme of this paper clarifies the logical relationship between the compactness of the approximation and the boundedness of the state variables.Finally,the application of control strategy is demonstrated by numerical/practical examples.
基金supported in part by Shanghai Rising-Star Program under Grant No.22QA1409400in part by the National Natural Science Foundation of China under Grant Nos.62473287 and 62088101in part by Shanghai Municipal Science and Technology Major Project under Grant No.2021SHZDZX0100。
文摘This paper considers the practical fixed-time tracking control problem for a state constrained pure-feedback nonlinear system.A new barrier function is first proposed to handle various asymmetric time-varying constraints and unify the cases with and without state constraints.Then a low-cost neural network based adaptive fixed-time controller is constructed by further combining the dynamic surface control,which overcomes the technical problems of overparametrization and singularity in the backstepping procedure.The proposed design guarantees that the tracking error converges to a small neighbourhood of zero in a fixed time while satisfying the state constraints as a priority task without imposing feasibility conditions on the virtual controllers.Simulation results validate the effectiveness of the proposed adaptive fixed-time tracking control strategy.
基金supported by the National Natural Science Foundation of China(62203356).
文摘In this paper,the problem of non-singular fixed-time control with prescribed performance is studied for multi-agent systems characterized by uncertain states,nonlinearities,and nonstrict feedback.To mitigate the nonlinearity,a fuzzy logic algorithm is applied to approximate the intrinsic dynamics of the system.Furthermore,a fuzzy logic system state observer based on leader state information is designed to address the partial unob-servability of followers.Subsequently,the power integral method is incorporated into the backstepping approach to avoid singularities in the fixed-time controller.A command filter method is introduced into the standard backstepping approach to reduce the computational complexity of controller design.Then,a non-singular fixed-time adaptive control strategy with prescribed performance is proposed by constraining the tracking error within a prescribed range.Rigorous theoretical analysis ensures the convergence of consensus error in the multi-agent system to the prescribed performance region within a fixed time.Finally,the practicality of the algorithm is validated through numerical simulations.
基金Key Research and Development Program of Shaanxi(Grant No.2023-GHZD-32)China Postdoctoral Science Foundation(Grant No.2023M732862)+2 种基金Natural Science Basic Research Program of Shaanxi(Grant No.2024JC-YBQN-0650)National Natural Science Foundation of China(Grant No.62273277)Natural Science Foundation of Chongqing,China(Grant No.2023NSCQ-MSX2403)。
文摘This paper studies the dynamic and control problems of space tether system(STS)after capturing space debris.The fully integrated system post-capture is referred to as space tether debris-assembly(STDA),while the system comprising the capture device and debris is termed the debris assembly.A significant challenge in stabilizing STS after debris capture lies in the residual angular momentum of the debris,which,if unmitigated,coupled with the relative angular velocity difference between the debris and the tether,can lead to detrimental effects such as tether entanglement and system destabilization.Furthermore,STDA system experiences unknown mass parameter variations that exacerbate control difficulties.To address these challenges,this paper proposes a nonlinear control strategy designed to rapidly stabilize the attitude motion of the end body,despite uncertainties in mass parameters and boundary constraints.A dynamic model of STDA system,encompassing the host spacecraft,tether,capture device,and space debris,is formulated based on Lagrangian equation.This model accounts for the relative attitude motion between the debris-assembly and the tether,as well as the attitude dynamics of the tether itself,thereby enabling an analysis of disturbances arising from unknown mass parameters and collision-induced angular motion.To mitigate these disturbances,a sliding mode disturbance observer is developed to compensate for dynamic uncertainties associated with the space debris'unknown mass.Furthermore,an error transformation is performed,and a prescribed performance controller is designed to ensure that the system remains within predefined boundaries during stabilization.The effectiveness of the proposed method is validated through numerical simulations.
基金supported by the National Natural Science Foundation of China(62373317)the Tianshan Talent Training Program(2022TSYCCX0013)+3 种基金the Key Project of Natural Science Foundation of Xinjiang(2021D01D10)the Basic Research Foundation for Universities of Xinjiang(XJEDU2023P023)the Xinjiang Key Laboratory of Applied Mathematics(XJDX1401)the Intelligent Control and Optimization Research Platform in Xinjiang University.
文摘This paper is dedicated to fixed-time passivity and synchronization for multi-weighted spatiotemporal directed networks.First,to achieve fixed-time passivity,a type of decentralized power-law controller is developed,in which only one parameter needs to be adjusted in the power-law terms;this greatly decreases the inconvenience of parameter adjustment.Second,several fixed-time passivity criteria with LMI forms are derived by using a Gauss divergence theorem to deal with the spatial diffusion of nodes and by applying the Hölder’s inequality to dispose rigorously the power-law term greater than one in the designed control scheme;this improves the previous theoretical analysis.Additionally,the fixed-time synchronization of spatiotemporal directed networks with multi-weights is addressed as a direct result of fixed-time strict passivity.Finally,a numerical example is presented in order to show the validity of the theoretical analysis.
基金supported by the National Natural Science Foundation of China under Grants 61962023,61562029 and 62466019.
文摘This paper presents an adaptive multi-agent coordination(AMAC)strategy suitable for complex scenarios,which only requires information exchange between neighbouring robots.Unlike traditional multi-agent coordination methods that are solved by neural dynamics,the proposed strategy displays greater flexibility,adaptability and scalability.Furthermore,the proposed AMAC strategy is reconstructed as a time-varying complex-valued matrix equation.By introducing a dynamic error function,a fixed-time convergent zeroing neural network(FTCZNN)model is designed for the online solution of the AMAC strategy,with its convergence time upper bound derived theoretically.Finally,the effectiveness and applicability of the coordination control method are demonstrated by numerical simulations and physical experiments.Numerical results indicate that this method can reduce the formation error to the order of 10^(-6)within 1.8 s.
基金Supported by the National Natural Science Foundation of China(62576008)University Annual Scientific Research Plan of Anhui Province(2022AH030023)。
文摘In this paper,a class of discontinuous Cohen-Grossberg neural networks with timevarying delays is considered.Firstly,under the extended Filippov differential inclusions framework,the problem of periodic solutions of the considered neural networks with more relaxed conditions imposed on the amplification functions is analyzed by using set-valued mapping and Kakutani's fixed point theorem,which has rarely been used to study such problem.Secondly,the fixed-time synchronization of the error system of the considered neural networks is also investigated by designing a novel control strategy,which can improve not only the previous ones with sign function greatly,but also can reduce the chattering phenomenon.Finally,two numerical examples are presented to further illustrate the validity of the obtained results.
文摘This paper presents an investigation on the target-guided coordinated control(TACC)of unmanned surface vehicles(USVs).In the scenario of tracking non-cooperative targets,the status information of the target can only be obtained by some USVs.In order to achieve semi-encirclement tracking of noncooperative targets under maritime security conditions,a fixed-time tracking control method based on dynamic surface control(DSC)is proposed in this paper.Firstly,a novel TACC architecture with decoupled kinematic control law and decoupled kinetic control law was designed to reduce the complexity of control system design.Secondly,the proposed DSC-based target-guided kinematic control law including tracking points pre-allocation strategy and sigmoid artificial potential functions(SigAPFs)can avoid collisions during tracking process and optimize kinematic control output.Finally,a fixed-time TACC system was proposed to achieve fast convergence of kinematic and kinetics errors.The effectiveness of the proposed TACC approach in improving target tracking safety and reducing control output chattering was verified by simulation comparison results.
基金Supported by the National Natural Science Foundation of China(62476082)。
文摘This paper investigates modified fixed-time synchronization(FxTS)of complex networks(CNs)with time-varying delays based on continuous and discontinuous controllers.First,for the sake of making the settling time(ST)of FxTS is independent of the initial values and parameters of the CNs,a modified fixed-time(FxT)stability theorem is proposed,where the ST is determined by an arbitrary positive number given in advance.Then,continuous controller and discontinuous controller are designed to realize the modified FxTS target of CNs.In addition,based on the designed controllers,CNs can achieve synchronization at any given time,or even earlier.And control strategies effectively solve the problem of ST related to the parameters of CNs.Finally,an appropriate simulation example is conducted to examine the effectiveness of the designed control strategies.
文摘This paper presents an entire fixed-time disturbance observer-based global terminal switching sliding mode control of robot manipulators,which has inner and external uncertainties.The entire fixed-time disturbance observer-based global terminal switching sliding mode control has the global finite-time reaching characteristic,the property that system convergence time can be prescribed,and the global robustness to uncertainties,with the entire fixed-time disturbance observer that accurately estimates uncertainties after a fixed time,despite the initial state.The joints of the control system can arrive at the prescribed joint angular position at the predefined joint angular speed at the prescribed time.
基金supported by the National Natural Science Foundation of China(Nos.61720106010,62003041)Science and Technology on Space Intelligent Control Laboratory,China(No.KGJZDSYS-2018-05)General Project of Ningxia Natural Science Fund,China(No.2020AAC03234)。
文摘This paper investigates the distributed fixed-time attitude coordinated control problem for multiple spacecraft subject to actuator saturation under the directed topology. First, a distributed fixed-time observer is presented for each follower spacecraft to estimate the leader spacecraft’s states. Compared with the commonly used fixed-time observer, the settling time of the proposed fixed-time observer can be easily adjusted by some free design parameters. Next, a distributed fixed-time control scheme is derived by using the estimates of the leader spacecraft’s states and the adding a power integrator technique. When considering actuator saturation, an auxiliary system is utilized to compensate the saturation. Further, a rigorous theoretical proof is provided to show that the practical fixed-time stability of the closed-loop system is ensured. Finally, simulation results illustrate the benefits and effectiveness of the developed control scheme.
基金supported by the National Natural Science Foundation of China(U1808205)the Fundamental Research Funds for the Central Universities(N2023011)+1 种基金the Youth Foundation of Hebei Educational Committee(QN2020522)the Natural Science Foundation of Hebei Province(F2020501018)。
文摘This paper investigates the heading tracking problem of surface vehicles with unknown model parameters.Based on finite/fixed-time control theories and in the context of command filtered control,two novel adaptive control laws are developed by which the vehicle can track the desired heading within settling time with all signals of the closed-loop system are uniformly bounded.The effectiveness and performance of the schemes are demonstrated by simulations and comparison studies.
基金This work was supported by the National Natural Science Foundation of China(62003131,62073121,62173125)the Natural Science Foundation of Jiangsu Province(BK20200520).
文摘This paper studies the fixed-time output-feedback control for a class of linear systems subject to matched uncertainties.To estimate the uncertainties and system states,we design a composite observer which consists of a high-order sliding mode observer and a Luenberger observer.Then,a robust output-feedback controller with fixed-time convergence guarantee is constructed.Rigorous theoretical proof shows that with the proposed controller,the system states can converge to zero in fixed-time free of the initial conditions.Finally,simulation comparison with existing algorithms is given.Simulation results verify the effectiveness of the proposed controller in terms of its fixed-time convergence and perfect disturbance rejection.
文摘Fixed-time control of traffic signals pursues the regulation of phases based on historical data of traffic demand, in this way, neglecting of the random arrival rates of traffic flow on different intersection streams causes increasing of the stops and delays and fuel consumption at the same time. Coordinated semi-actuated control due to ability to respond traffic demands on both main and secondary directions, based on road detector registration saves the coordinated features, serving the unused time to the main road, while the secondary clears early. In this paper, the authors analyzed and explained comparatively the results of LOS （level of service） parameters of the current state of control （fixed-time） with the proposed control （semi-actuated coordinated） of the artery of length 2,348 km consisted of four signalized T intersections. Highway Capacity Manual and Synchro/Sim Traffic software are used for analysis and optimization of parameters in this paper.
基金This work is supported in part by the Ministry of Education(MOE),Singapore under Grant MOE2020-T1-1-067also partially supported by the National Natural Science Foundation of China under Grants 62103352 and 61903319.
文摘In this paper,we consider the fixed-time stabilization control problem of quantum systems modeled by Schrodinger equations.Firstly,the Lyapunov-based fixed-time stability criterion is extended to finitedimensional closed quantum systems in the form of coherence vectors.Then for a two-level quantum system with single control input,a non-smooth fractional-order control law is designed using the relative state distance.By integrating the fixed-time Lyapunov control technique and the bi-limit homogeneity theory,the quantum system is proved to be stabilized to an eigenstate of the inherent Hamiltonian in a fixed time.Comparing with existing methods in quantum system control,the proposed approach can guarantee stabilization in a fixed time without depending on the initial states.
基金supported by the National Natural Science Foundation of China(61903099)the Natural Science Foundation of Heilongjiang Province(LH2020F025)+2 种基金the Project of Science and Technology Research Program of Chongqing Education Commission of China(KJZD-K20200470)the Postdoctoral Science Foundation of China(2021M690812)the Postdoctoral Science Fund of Heilongjiang Province(LBH-Z21048).
文摘This paper presents a fixed-time cooperative gui-dance method with impact angle constraints for multiple flight vehicles (MFV) to address the challenges of intercepting large maneuvering targets with difficulty and low precision. A coopera-tive guidance model is proposed, transforming the cooperative interception problem into a consensus problem based on the remaining flight time of the flight vehicles. First, the impact angle constraint is converted into the line of sight (LOS) angle con-straint, and a new fixed-time convergent non-singular terminal sliding surface is introduced, which resolves the singularity issue of the traditional sliding surfaces. With this approach, LOS angle rate and normal overloads can converge in fixed time, ensuring that the upper bound of the system convergence time is not affected by the initial value of the system. Furthermore, the maneuvering movement of the target is considered as a system disturbance, and an extended state observer is employed to estimate and compensate for it in the guidance law. Lastly, by applying consensus theory and distributed communication topology, the remaining flight time of each flight vehicle is syn-chronized to ensure that they intercept the target simulta-neously with different impact angles. Simulation experiments are conducted to validate the effectiveness of the proposed cooper-ative interception and guidance method.
