Event-triggered Output Feedback Control Research Articles

Adaptive model-based dynamic event-triggered output feedback control of a robotic manipulator with disturbance

This paper focuses on the stable tracking control of the manipulator with constrained communication, unmeasurable velocity, and nonlinear uncertainties. An NN observer-depended output feedback scheme in the discrete-time domain is developed by virtue of the model-based dynamic event-triggered backstepping technique in the channel of sensor to controller. For generalizing the zero-order-holder (ZOH) implementation, a plant model is built to approximate the triggered states in the time flow, and according to which, the control law is fabricated. Based on model-based error events, we construct a dead-zone triggered condition with a dynamically adjustable threshold, making the threshold evolve with the system performance, to achieve flexible communication scheduling and avoid the accumulation of triggers in small tracking errors. The internal and external nonlinear uncertainties are online compensated by the neural network, and the aperiodic adaptive law is derived in the sense of control stability to save the computation. Finally, the conditions for semi-global ultimate uniform bounded (SGUUB) of all variables are given via impulse Lyapunov analysis, and a positive lower bound in the time interval between consecutive executions to guarantee the Zeno free behavior is obtained. Simulations are conducted on a three-link manipulator to illustrate the effectiveness of our method.

Distributed event‐triggered output feedback H∞ control for multi‐agent systems with transmission delays

The output feedback H ∞ consensus control problem of multi-agent systems is studied using an event-triggered control strategy. Two types of transmission delays, one from the system output to the output feedback controller (OFC) and the other from the OFC to the zero-order holder, are considered. This causes the OFC and the system not to be updated in the same time intervals. An interval dividing approach is applied to such that the whole system can be updated in the same time intervals. An event-triggered OFC with H ∞ performance is proposed for multi-agent systems to achieve consensus. By constructing an appropriate Lyapunov–Krasovskii functional, sufficient conditions based on linear matrix inequality are derived to guarantee the consensus achievement. Finally, the theoretical results are validated using computer simulation.

Fuzzy adaptive event-triggered output feedback control for nonlinear systems with tracking error constrained and unknown dead-zone

ABSTRACT In this paper, an adaptive fuzzy event-triggered output feedback control scheme is studied for a class of non-strict feedback systems with tracking error constrained and unknown dead-zone. Fuzzy logical systems (FLSs) are employed to solve the uncertainties of the controlled plant, and the immeasurable states are estimated by employing the fuzzy observer. In the designed observer, to compensate for the effect of unknown dead-zone by invoking the known designed event-triggered input signal, an adaptive parameter is designed. Furthermore, due to event-triggered control (ETC) places a great burden on the computing space, the dynamic surface control (DSC) technique is used to solve the problem of ‘explosion of complexity’ in each step, and the simplified barrier Lyapunov function (SBLF) is utilised to restrict the tracking error within the prescribed boundaries. Consequently, the designed parameter adaptive laws and event-triggered controller can ensure that all signals of the closed-loop system are semi-globally uniformly ultimately bounded (SGUUB). Ultimately, two numerical simulation examples are provided to illustrate the effectiveness of the proposed event-triggered control theory.

Event-Triggered Output Feedback Control of Switched Nonlinear Systems With Input Saturation.

This article is concerned with the event-triggered output feedback control problem for a class of switched nonlinear strict-feedback systems subject to asymmetric input saturation. The nonlinear terms are assumed to be bounded by a continuous function of the output multiplied by unmeasured states. The hyperbolic tangent function is employed to process the error caused by the event-triggered scheme, and an indicator function of the saturation degree is used to analyze the influence generated by the asymmetric input saturation. By adopting the common Lyapunov function method and the dynamic gain control design approach, a new design procedure based on a reduced-order observer is proposed to construct an output feedback controller. It is proved by the Lyapunov analysis that the proposed event-triggered control scheme can ensure that all the signals of the closed-loop system are globally bounded. Furthermore, the output can be converged to a bounded region around the origin, and this region can be tuned to be small by adjusting the design parameters. Different from typical existing results on the switched nonlinear strict-feedback systems, the celebrated backstepping method is not employed in this article. The continuous stirred tank reactor is finally used to demonstrate the effectiveness of the proposed control scheme.

Formula omitted]-gain analysis for dynamic event-triggered networked control systems with packet losses and quantization

The problem of event-triggered output feedback control for networked control systems (NCSs) with packet losses and quantization is addressed. A new dynamic quantization scheme is proposed to prevent saturation of the quantizer in the presence of external disturbances, and using the emulation-based approach, we show how to design the event-triggering conditions to guarantee the L2-gain performance of the overall system. To cope with the successive packet losses and the dynamic quantization, the NCS is embedded into a hybrid dynamical system, which is capable of describing these dynamics. Then, a novel Lyapunov function type is constructed to analyze the L2-gain performance with the quantization and packet dropout effects. Furthermore, owing to the proposed method, the Zeno phenomenon resulting from the transmission instants and updates of quantizer are prevented by introducing a minimum inter-event time. Finally, a numerical simulation is introduced to demonstrate the feasibility of the proposed design approach.

Dynamic event-triggered output feedback control for a class of nonlinear systems with time-varying delays

This note studies the problem of dynamic event-triggered output feedback control for a class of nonlinear systems under homogeneous growth condition with unknown growth rate and time delays. Firstly, in order to deal with unknown growth rate and time-varying state delays, a double-gain dynamic scheme is introduced and a suitable Lyapunov–Krasovskii functional is selected. Secondly, a dynamic event-triggered strategy is proposed by introducing the dynamic gain to the event-triggered condition, which makes the triggering threshold be tuned dynamically. Compared with some existing works related to event-triggered strategy, the proposed strategy is more flexible for saving communication resources. Subsequently, a new output feedback control law is developed in the context of event-triggered mechanism to guarantee the boundedness of system signals while the system states globally enter a compact set around the origin. Finally, two examples are given to show the feasibility and merit of the presented scheme.

Switched-Observer-Based Event-Triggered Adaptive Fuzzy Funnel Control for Switched Nonlinear Systems

This article addresses the event-triggered output-feedback funnel tracking control problem for a class of switched nonlinear systems. A novel switched-observer-based event-triggered adaptive fuzzy funnel control approach for solving the problem is proposed by exploiting the average dwell time method and backstepping. To estimate unmeasurable system states, a switched fuzzy observer and switched update laws for individual subsystems are designed. Compared with the existing funnel controllers designed in the framework of continuous-time feedback control, the proposed approach constructs event-triggered funnel controllers of subsystems and a switching event-triggered mechanism (ETM), which greatly alleviates the unnecessary waste of communication and computation resources, and, without any known limitation on maximum asynchronous time, handles the issue of asynchronous switching between the candidate controllers of subsystems and subsystems. Also, a strictly positive lower bound on interevent time is ensured by introducing a piecewise constant variable into the ETM, which overcomes the difficulty of switched measurement error being discontinuous. It is guaranteed that the tracking error evolves within a prespecified performance funnel. Finally, two examples including a mass-spring-damper system are presented for illustrating the validity of the developed approach.

Event-Triggered Output-Feedback Backstepping Control of Sandwich Hyperbolic PDE Systems

Motivated by vibration control of a mining cable elevator avoiding frequent actions of a massive actuator, which is a hydraulic cylinder driving a head sheave, we present an event-triggered output-feedback backstepping boundary controller for <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$2\times 2$</tex-math></inline-formula> coupled hyperbolic partial differential equations (PDEs) sandwiched by two ordinary differential equations (ODEs), through a two-step design including an output-feedback low-pass-filter-based backstepping boundary stabilization law and the subsequent design of a dynamic event-triggering mechanism. The existence of a minimal dwell-time between two triggering times, and exponential convergence in the event-based closed-loop system are proved in this article. In numerical simulations, the proposed control design is validated in the application of axial vibration control of a mining cable elevator.

Dynamic event-triggered output feedback control for stochastic nonlinear systems

Abstract In this paper, the event-triggered stabilization problem for stochastic nonlinear systems is addressed. A dynamic event-triggered transmission strategy is proposed for general stochastic nonlinear systems without the linear growth assumption and the proposed transmission strategy can be applied to the output-based dynamic controller. Zeno phenomenon is avoided in the transmission strategy. The resulted closed-loop system is modeled into a stochastic hybrid system. Uniformly globally asymptotic stability in probability is concluded by showing that the equilibrium set is uniformly globally stable in probability and arbitrarily small neighborhood of the equilibrium set is uniformly globally recurrent in probability.

Adaptive Event-Triggered Control for Switched p-Normal Nonlinear Systems via Output Feedback.

This article studies the issue of adaptive event-triggered output-feedback control for switched p -normal nonlinear systems with the unknown homogeneous growth rate. A homogeneous output-feedback controller is first designed for nominal nonlinear systems based on adding one power integrator technique. Then, a dynamic gain technique is introduced to deal with the difficulty caused by the unknown homogeneous growth rate. With an elaborate design of the adaptive law of the dynamic gain, a novel adaptive event-triggered output-feedback controller is developed to ensure that the closed-loop system is globally asymptotically stable. Meanwhile, a new analysis way is proposed to prove that the Zeno behavior is excluded in the event-triggered control system. Finally, two examples are provided to indicate the effectiveness of the proposed control method.

Event-Triggered Adaptive Optimal Control With Output Feedback: An Adaptive Dynamic Programming Approach.

This article presents an event-triggered output-feedback adaptive optimal control method for continuous-time linear systems. First, it is shown that the unmeasurable states can be reconstructed by using the measured input and output data. An event-based feedback strategy is then proposed to reduce the number of controller updates and save communication resources. The discrete-time algebraic Riccati equation is iteratively solved through event-triggered adaptive dynamic programming based on both policy iteration (PI) and value iteration (VI) methods. The convergence of the proposed algorithm and the closed-loop stability is carried out by using the Lyapunov techniques. Two numerical examples are employed to verify the effectiveness of the design methodology.

Neural-Network Approximation-Based Adaptive Periodic Event-Triggered Output-Feedback Control of Switched Nonlinear Systems.

This study considers an adaptive neural-network (NN) periodic event-triggered control (PETC) problem for switched nonlinear systems (SNSs). In the system, only the system output is available at sampling instants. A novel adaptive law and a state observer are constructed by using only the sampled system output. A new output-feedback adaptive NN PETC strategy is developed to reduce the usage of communication resources; it includes a controller that only uses event-sampling information and an event-triggering mechanism (ETM) that is only intermittently monitored at sampling instants. The proposed adaptive NN PETC strategy does not need restrictions on nonlinear functions reported in some previous studies. It is proven that all states of the closed-loop system (CLS) are semiglobally uniformly ultimately bounded (SGUUB) under arbitrary switchings by choosing an allowable sampling period. Finally, the proposed scheme is applied to a continuous stirred tank reactor (CSTR) system and a numerical example to verify its effectiveness.

Event-triggered robust control for quadrotors with preassigned time performance constraints

In this paper, an event-triggered robust control for quadrotors with preassigned time performance constraints is presented. In order to prolong operational time and enhance mission completion efficiency subject to limited onboard power, a switching threshold event-triggered strategy is embedded in controller-to-actuator and sensor-to-controller channels, where switching threshold event-triggered based extended state observers (SET-ESO) are respectively established in the trajectory and attitude subsystems to accomplish the real-time estimation of linear velocity, angular velocity along with lumped disturbances using intermittent measurements, and the quantitative analysis between the ultimate observation error and parameters of SET-ESO is revealed. Based on the estimation results, an event-triggered output feedback control law including a robust compensation term is established to realize an anti-disturbance time-varying trajectory tracking without involving Zeno phenomena. Moreover, to eliminate severe fluctuations at the transient inherent in traditional prescribed performance control (TPPC) with a fast convergent rate, a tracking differentiator-based prescribed performance control (TDPPC) mechanism is exploited to ensure the trajectory state converge to a pre-given region with a preassigned prescribed time, such that a smooth and pre-specified finite-time tracking capability independent of control parameters is preserved. Next, with the aid of Lyapunov synthesis, all the signals involved in the closed-loop quadrotor system are proved to be bounded, and the preassigned time performance constraints are not violated. The simulation and comparison results are shown to validate the effectiveness of the proposed control scheme.

Boundary stabilisation via event-triggered output-feedback for a class of 2 × 2 hyperbolic systems

This paper is devoted to the boundary stabilisation via event-triggered output-feedback for a class of hyperbolic systems. Different from the closely related works, the system parameters are spatially varying and only one boundary measurement is available for feedback, which brings essential difficulties to the analysis and synthesis of event-triggered control. To solve the problem, by using the time-varying strategy and the infinite-dimensional backstepping technique, a novel event-triggered output-feedback controller is designed for the systems. Particularly, a time-varying event-triggering mechanism, with an extra decaying signal introduced into the threshold, is determined. It is rigorously shown that the designed event-triggered controller can guarantee that all the states of the resulting closed-loop system exponentially converge to zero in the sense of norm while no Zeno phenomenon occurs. Two simulation examples are given to illustrate the effectiveness of the established boundary control strategy.

Robust Output Regulation of Linear Systems by Event-Triggered Dynamic Output Feedback Control

In this article, we study the robust output regulation problem of linear systems by an event-triggered output feedback control law. We first summarize the solvability of the linear robust output regulation problem by the internal model design. Then, we implement this continuous-time control law by an event-triggered output feedback control law together with an output-based triggering mechanism. We show that, under almost the same solvability conditions as those for the linear robust output regulation problem, the robust output regulation problem can also be solved by an event-triggered output feedback control law without incurring Zeno phenomenon. Furthermore, we show that, it is possible to solve the robust output regulation problem practically while preventing the interevent time from approaching zero as time tends to infinity.

Event-triggered output feedback control for discrete Markov jump systems under deception attack

An event-triggered dynamic output feedback control (DOFC) problem for discrete Markov jump systems is considered, where both measurement and control channel are under the deception attacks. To reduce the data traffic in the channel and the control actions against attack, two event-triggered schemes (ETSs) are implemented on sensor and controller node asynchronously. And two quantizers are installed independently. Sufficient criterions for ensuring asymptotic stability of the networked control systems (NCSs) are obtained by deriving the Lyapunov functional, and the co-design of DOFC with ETSs can be acquired in terms of the linear matrix inequality (LMI). An application on DC motor is utilized to prove the feasibility of this method.

Adaptive event-triggered output-feedback controller for uncertain nonlinear systems

This paper addresses the event-triggered output-feedback stabilization for a class of uncertain nonlinear systems. Essentially different from the related literature, the systems under investigation allow large uncertainties (whose size is unknown) coupling to unmeasurable states, which requires to integrate a comprehensive output-feedback compensation mechanism into the event-triggered philosophy and would bring substantial challenges to the event-triggered control. To solve the problem, a novel scheme of adaptive event-triggered output-feedback control is established for the systems. Specifically, an adaptive dynamic gain is introduced not only to counteract the large uncertainties but also to cope with the execution/sampling error. Then, an adaptive event-triggered output-feedback controller based on dynamic-gain observer is constructed to guarantee global convergence for the resulting closed-loop system while reducing execution/sampling. Particularly, the event-triggering mechanism involved is delicately designed by fully exploiting the dynamic gain, to enable the negative influence of the gain through the execution error to be counteracted (no matter how large the gain becomes) while precluding infinitely fast execution which violates the implementation of event-triggered controller in practice. Correspondingly, a distinctive analysis pattern is implemented for the closed-loop performance, due to the coupling of the dynamic-gain compensation mechanism and the event-triggering mechanism. Moreover, for more efficient resource saving, we further show the feasibility of adaptive dynamic event-triggering mechanism for the desired stabilization.

Event‐triggered practical finite‐time output feedback stabilisation for switched non‐linear time‐delay systems

This study investigates the event-triggered practical finite-time output feedback control for a class of switched high-order non-linear time-delay systems with uncertain control coefficients. A reduced-order observer is first constructed to estimate the unmeasurable states. By adding a power integrator technique, an event-triggered output feedback controller is designed for the nominal system. Subsequently, the constructed observer and controller are scaled with a suitable gain by homogeneous domination approach, which, together with an appropriate Lyapunov–Krasoviskii functional, can render that the uncertain switched high-order non-linear system with time-varying delay is practical finite-time stability. Finally, two examples are provided to demonstrate the validity of the proposed scheme.

A Switching Method to Event-Triggered Output Feedback Control for Unmanned Aerial Vehicles Over Cognitive Radio Networks

This article investigates the event-triggered output feedback control problem for unmanned aerial vehicle (UAV) systems over cognitive radio (CR) networks. A periodic event-triggered scheme is proposed in the presence of CR networks. By modeling the CR network as an <sc xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">on</small> – <sc xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">off</small> switch, a new switched time-delay system model is developed for the event-triggered UAV. Based on the new model, the exponential stability and <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$H_{\infty }$ </tex-math></inline-formula> performance criteria are derived by using the constructed Lyapunov function. Then, a co-design method is proposed to obtain mode-dependent controller gains and trigger parameters simultaneously. Finally, the proposed scheme is verified by a UAV system.

Distributed Bipartite Consensus of Linear Multiagent Systems Based on Event-Triggered Output Feedback Control Scheme

This article investigates the bipartite consensus problem for linear multiagent systems by the event-triggered output feedback control scheme. Both cooperative interaction and antagonistic interaction between neighbor agents are considered. Assuming that the system states are not available for measurement, the state observer is thus proposed to settle this scenario. Then, a novel observer-based bipartite control scheme is developed on the basis of two event-triggering mechanisms. One is designed for the communication between neighbors and another is for controller updates. Different from the existing methods, the proposed control strategy does not need continuous updates, avoids continuous communication between neighbors, and is applicable for the signed communication topology. Moreover, we extend the results from the bipartite leaderless consensus to the bipartite leader-following consensus and the bipartite containment consensus. It is proven that the proposed controllers fulfill the exclusion of Zeno behavior in three consensus problems. Finally, three examples are provided to illustrate the feasibility of the theoretical results.