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In the work, the observer-based control is designed and analyzed for a class of large-scale interconnected systems subject to parameter uncertainty. In the beginning, we build a large-scale interconnected system with parameter uncertainty and apply this model to a multi-level wireless power transfer system. By using this modeling method, the order of multi-level wireless power transfer system is greatly deduced. In addition, the multi-level wireless power transfer system include coupling terms and uncertain parameters considered in the observer-based control law design. We earn sufficient conditions of this model stability for multi-level wireless power transfer systems under this control law through the Lyapunov stability theorem and Young's inequality. The stability analysis method suggested in the work could also be adopted in other practical plants. At last, the correctness and availability of this suggested approach are verified through simulation results. [ABSTRACT FROM AUTHOR]

The performance of speed tracking is crucial for electric vehicles. In this paper, the observer-based speed tracking controller is designed to improve the stability, reliability, and economy of the IMT system by obtaining unmeasurable state information using the observer. The nonlinearity of the IMT system, the uncertainty of the electric damping coefficient, and the drive shaft damping coefficient are taken into account. First, the norm-bounded uncertainty reduction method describes the system uncertainty parameters and establishes the state space in expression. Second, the system is reconstructed to deal with the nonlinear and unmeasurable states. Third, Lyapunov stability theory and linear matrix inequality (LMI) are used to design the optimal controller that has H ∞ and LQR performance conditions to minimize the effects of sensor noise and road slope and to ensure system stability and control performance. Among them, the nonlinear mismatch term in the system is dealt with using the differential mean value theorem (DMVT). Finally, compared with other controllers, the designed controller has good tracking performance, anti-disturbance, and robustness, and the observer can estimate the state effectively. [ABSTRACT FROM AUTHOR]

This work introduces a novel control framework using the Caputo fractional derivative (CFD) with respect to another function—a derivative that has not been thoroughly treated in control theory. By extending the widely recognized Caputo-Hadamard (CH) fractional-order derivative, we address its utility in nonlinear systems. The core of our contribution is the practical stability for systems governed by this derivative, which ensures convergence toward a bounded region around the origin. Additionally, we extend the Lipschitz condition (LC) to the one-sided Lipschitz (OSL) condition for observer design and observer based-control design in fractional-order systems, ensuring its practical stability. Finally, three numerical examples validate the effectiveness of our proposed framework, providing practical insights for control theory advancements. [ABSTRACT FROM AUTHOR]

This work introduces a novel control framework using the Caputo fractional derivative (CFD) with respect to another function—a derivative that has not been thoroughly treated in control theory. By extending the widely recognized Caputo-Hadamard (CH) fractional-order derivative, we address its utility in nonlinear systems. The core of our contribution is the practical stability for systems governed by this derivative, which ensures convergence toward a bounded region around the origin. Additionally, we extend the Lipschitz condition (LC) to the one-sided Lipschitz (OSL) condition for observer design and observer based-control design in fractional-order systems, ensuring its practical stability. Finally, three numerical examples validate the effectiveness of our proposed framework, providing practical insights for control theory advancements.

The problem of output feedback stabilization for a class of stochastic switched planar systems (Sto-SPS) subjected to asymmetric output constraints is investigated. A new tangent-type asymmetric barrier Lyapunov function (BLF) with quartic terms, which is independent of nonlinear terms of Sto-SPS and takes the pre-set asymmetric output constraint into consideration, is developed first. Next, the proposed BLF is exploited to renovate the adding a power integrator technique elegantly and state feedback stabilizers are presented systematically. Then, with the deliberately constructed stochastic reduced-order switched observers, an observer-based output feedback control strategy is thereby established while guaranteeing the pre-specified asymmetric output constraint successfully. Ascribing to its unified nature, the proposed scheme is effective for Sto-SPS whether output constraints are imposed on or not, which eliminates the need for additional modifications to the controllers' structure. The presented simulations demonstrate the effectiveness of the proposed method. [ABSTRACT FROM AUTHOR]

In this paper, a novel dynamic event‐triggered control protocol for leader‐following problems of generic linear multi‐agent systems is proposed. Compared with the existing static event‐triggered strategy, the developed event‐triggered approach significantly reduces the utilization of communication resources while guaranteeing asymptotic consensus, and the interevent time is adjustable. Under this event scheduling mechanism, a synthesis approach combining controller and observer design is presented. The observer‐based control and event‐triggered rules are distributed, which only require local information of each agent to implement. The proposed methods incorporate model‐based estimation and auxiliary dynamic variables with a clock‐like behavior to prolong the interevent time as long as possible. The sufficient conditions for leader‐following consensus are established using linear matrix inequalities (LMIs) formulation to facilitate numerical computation. Comparative simulations in different scenarios demonstrate the validity of the proposed theoretical results. [ABSTRACT FROM AUTHOR]

This work aims to analyse the cluster consensus for positive multi-agent systems (MASs) with nonlinearities. This study focuses on introducing an observer-based controller with the aim of achieving cluster consensus in the considered positive nonlinear MASs, where the controller includes time-varying delay. Specifically in cluster consensus, agents are divided into multiple clusters to accomplish various collective tasks, each influenced by distinct inter-cluster and intra-cluster communications. In this study, a fixed directed graph is employed to express the communication among agents. By designing a proper Lyapunov-Krasovskii functional and utilising the properties of graph, a set of conditions required for cluster consensus of the examined MASs is established as linear matrix inequalities. Finally, the effectiveness of the derived theoretical findings is confirmed through numerical examples. [ABSTRACT FROM AUTHOR]

This work aims to focus on analyzing the consensus control problem in cooperative–competitive networks in the occurrence of external disturbances. The primary motive of this work is to employ the equivalent input-disturbance estimation technique to compensate for the impact of external disturbances in the considered multi-agent system. In particular, a suitable low-pass filter is implemented to enhance the accuracy of disturbance estimation performance. In addition, a specific signed, connected, and structurally balanced undirected communication graph with positive and negative edge weights is considered to express the cooperation–competition communication among neighboring agents. The cooperative–competitive multi-agent system reaches its final state with same magnitude and in opposite direction under the considered structurally balanced graph. By utilizing the properties of Lyapunov stability theory and graph theory, the adequate conditions assuring the bipartite consensus of the examined multi-agent system are established as linear matrix inequalities. An illustrative example is delivered at the end to check the efficacy of the designed control scheme. [ABSTRACT FROM AUTHOR]

This paper presents an extensive investigation into the state feedback stabilization, observer design, and observer-based controller design for a specific category of nonlinear Hadamard fractional-order systems. The research extends the conventional integer-order derivative to the Hadamard fractional-order derivative, offering a more universally applicable method for system analysis. Furthermore, the traditional Lipschitz condition is adapted to a one-sided Lipschitz condition, broadening the range of systems amenable to analysis using these techniques. The efficacy of the proposed theoretical findings is illustrated through several numerical examples. For instance, in Example 1, we select an order of derivative r = 0.8; in Example 2, r is set to 0.9; and in Example 3, r = 0.95. This study enhances the comprehension and regulation of nonlinear Hadamard fractional-order systems, setting the stage for future explorations in this domain. [ABSTRACT FROM AUTHOR]

In this paper, we deal with the problem of exponential observer controller design for a class of nonlinear time-varying impulsive systems. We show that, under the classical conditions of uniform complete controllability and uniform complete observability, it is possible to design a novel observer-based control scheme for the nonlinear time-varying impulsive system. [ABSTRACT FROM AUTHOR]

This paper investigates the problem of observer-based control for a class of nonlinear systems described by the Caputo–Hadamard fractional-order derivative. Given the growing interest in fractional-order systems for their ability to capture complex dynamics, ensuring their practical stability remains a significant challenge. We propose a novel concept of practical stability tailored to nonlinear Hadamard fractional-order systems, which guarantees that the system solutions converge to a small ball containing the origin, thereby enhancing their robustness against perturbations. Furthermore, we introduce a practical observer design that extends the classical observer framework to fractional-order systems under an enhanced One-Sided Lipschitz (OSL) condition. This extended OSL condition ensures the convergence of the proposed practical observer, even in the presence of significant nonlinearities and disturbances. Notably, the novelty of our approach lies in the extension of both the practical observer and the stability criteria, which are innovative even in the integer-order case. Theoretical results are substantiated through numerical examples, demonstrating the feasibility of the proposed method in real-world control applications. Our contributions pave the way for the development of robust observers in fractional-order systems, with potential applications across various engineering domains. [ABSTRACT FROM AUTHOR]

This article introduces an observer‐based control strategy tailored for regulating plasma glucose in type 1 diabetes mellitus patients, addressing challenges like unknown time‐varying delays and meal disturbances. This control strategy is based on an extended Bergman minimal model, a nonlinear glucose‐insulin model to encompass unknown inputs, such as unplanned meals, exercise disturbances, or delays. The primary contribution lies in the design of an observer‐based state feedback control in the presence of unknown long delays, which seeks to support and enhance the performance of the traditional artificial pancreas by considering realistic scenarios. The observer and control gains for the observer‐based control are computed through linear matrix inequalities formulated from Lyapunov conditions that guarantee closed‐loop stability. This design deploys a soft and gentle dynamic response, similar to a natural pancreas, despite meal disturbances and input delays. Numerical tests demonstrate the scheme's effectiveness in glycemic level regulation and hypoglycemic episode avoidance. [ABSTRACT FROM AUTHOR]

Summary: The reduced‐order observer‐based finite‐time control problem for one‐sided Lipschitz nonlinear switched singular systems is addressed in this paper. First, the design method of the reduced‐order observer is given via state transformation. Then, based on the average dwell time (ADT) approach, some new sufficient conditions for regularity, impulse‐freeness, have a unique solution and finite‐time boundedness (FTB) of the dynamic augmented systems are obtained by exploring the reduced‐order observer‐based controller. Further, the lower finite‐time bound can be obtained by using singular value decomposition method. And the state feedback gain and the observer gain are computed by solving linear matrix inequalities (LMIs). Finally, the validity of the obtained method is illustrated by means of a numerical example and a DC motor system. [ABSTRACT FROM AUTHOR]

Summary: This paper presents neural networks (NNs) adaptive controller for an uncertain fractional‐order nonlinear system in strict‐feedback form, subject to input saturation, unavailable states for measurement, and external disturbances. The fractional‐order adaptive laws are derived based only on the output tracking error thanks to the implementation of the strictly positive real (SPR) property, differently from the existing results in the literature of fractional‐order strict‐feedback systems where all system states are used in the adaptive laws. The proposed design approach addresses the nonaffine nature of the control input due to saturation nonlinearity by using the mean value theorem and follows a nonrecursive design by using a state transformation where the advantage is twofold. First, it eliminates the explosion complexity found in back‐stepping control‐based approaches design, and second, it reduces the approximators units and parameters in controller implementation. Furthermore, an observer is introduced to estimate the unavailable newly defined states, and then an output adaptive feedback control design is ensured. An NN is used to approximate the unknown ideal control law, and an auxiliary control term is appended to deal with saturation effect, unknown disturbance, and approximation errors. The tracking error is proved to converge asymptotically to a bounded set using the Lyapunov theory. Simulation results on three examples show the effectiveness of the proposed approach. [ABSTRACT FROM AUTHOR]

Summary: This work solves the distributed tracking problem for multi‐agent systems with bounded inputs over directed networks. Unlike existing results focusing only on the input amplitude saturation, both input amplitude and input rate saturation are taken into account, which are more challenging due to the coupled evolutions of input amplitudes and input rates. Firstly, relative disturbance observers are developed using relative state measurements to estimate the relative disturbances, where the estimation errors converge to zero within a finite time horizon. Subsequently, distributed tracking error observers are proposed by means of a novel bounded function to estimate the tracking errors, where the estimation errors will converge to zero. Then, an observer‐based saturated control strategy is designed to achieve the distributed tracking objective. Finally, simulations of DC‐DC buck converters tracking and vehicles formation are provided to verify the effectiveness of the control scheme. [ABSTRACT FROM AUTHOR]

This paper proposes an observer-based proportional Derivative (O-BPD) fuzzy controller for uncertain discrete-time nonlinear descriptor systems (NDSs). Representing NDSs with the Takagi–Sugeno fuzzy model (T-SFM), the proportional derivative (PD) feedback method can be utilized in the fuzzy controller design via the Parallel Distributed Compensation (PDC) concept, such that the noncausal problem and impulse behavior are avoided. A fuzzy observer is proposed to obtain unmeasured states to fulfill the PD fuzzy controller. Moreover, uncertainties and transient response performances are taken into account for the NDSs. Then, a stability analysis process and corresponding stability conditions are derived from the Lyapunov theory with the robust control method and the pole constraint. Different from existing research, the Singular Value Decomposition (SVD) and the projection lemma are utilized to transfer the stability conditions into the Linear Matrix Inequation (LMI) form. Because of this reason, the conservatism of the analysis process can be reduced by eliminating the restriction on the positive definite matrix in the Lyapunov function. By giving the proper center and radius parameters of the pole constraint in the O-BPD fuzzy controller design process, the expected transient responses can be obtained for different designers and different practical applications. Finally, the effectiveness and applicability of the proposed O-BPD fuzzy controller are demonstrated by two examples of the simulation. [ABSTRACT FROM AUTHOR]

This paper introduces a novel observer-based fuzzy tracking controller that integrates disturbance estimation to improve state estimation and path tracking in the lateral control systems of Unmanned Ground Vehicles (UGVs). The design of the controller is based on linear matrix inequality (LMI) conditions derived from a Takagi–Sugeno fuzzy model and a relaxation technique that incorporates additional null terms. The state observer is developed to estimate both the vehicle’s state and external disturbances, such as road curvature. By incorporating the disturbance observer, the proposed approach effectively mitigates performance degradation caused by discrepancies between the system and observer dynamics. The simulation results, conducted in MATLAB and a commercial autonomous driving simulator, demonstrate that the proposed control method substantially enhances state estimation accuracy and improves the robustness of path tracking under varying conditions.

In this study, the Lyapunov technique is used to analyze the observer-based control problem for polynomial fuzzy fractional order (PFFO) models. The case of polynomial matrices with unmeasurable states is considered to increase the applicability of the PFFO models in the design problem. In this regard, we offer two design procedures. First, the design conditions are presented in a one-step procedure. In this design, the non-convex conditions are transformed in a set of sum of squares (SOS) by introducing a new symbolic variable except the state vector β and its estimated β ^ . The obtained SOS conditions are presented involve three independent symbolic variables which increase both computing complexity and conservatism. To get around this shortcoming, a second design method is developed. By using the suggested method, SOS conditions requiring just two separate symbolic variables may be obtained. The architecture is shown in two stages; however, the observer and controller gains are computed in a single stage in order to further minimize conservatism. In order to demonstrate the utility of the suggested theoretical analysis, a simulated example is then provided. [ABSTRACT FROM AUTHOR]

An observer‐based event‐triggered non‐fragile control problem for regulating the levels of oxygen and carbon dioxide (O2$$ {}_2 $$ and CO2$$ {}_2 $$) in patients blood during the extra‐corporeal blood circulation (ECC) process with random communication packet losses is explored in this work. The main intention of this work is to design an observer‐based event‐triggered and non‐fragile controller for ensuring the finite‐time boundedness criterion for the resulting system with mixed H∞$$ {H}_{\infty } $$ and passivity performance index over a finite interval of time. In addition to the limited bandwidth of the channels, such random packet losses might occur simultaneously between the sensors and the controllers, and between the controllers and the actuators. Unlike most studies in the literature, we have found that, since the controller‐actuator link has packet dropouts, the observer's control input differs from that of the plant. The sufficient conditions derived are presented in a linear matrix inequalities frame work. Finally, simulation results are used to validate the efficacy of the proposed control method. The results show that the proposed observer‐based event‐triggered non‐fragile controller keeps the blood gases within physiological limits during a stable ECC process. [ABSTRACT FROM AUTHOR]

Large wind turbines have typically poorly damped structures. Hence, the absence of damping leads to aeroelastic oscillations, and the operational rotor speed can approach the critical rotor speed. By using damping injection, the control system can actively introduce some additional damping. In the present work, a control approach to reduce oscillations of the rotor blades in the edgewise direction is proposed. The concept is based on the damping injection mechanism, and an additional level of safety is obtained by introducing the Dynamic Safety Margin (DSM) in the control law. The feedback control scheme requires some unmeasurable variables. This aspect is covered by using an interval observer. The control approach is tested by using simulations on a high-definition model implemented in an aeroservoelastic code. Simulation results are very satisfactory and promising for future experiments using hardware-in-the-loop equipment. [ABSTRACT FROM AUTHOR]

Sampled-data control of PDEs has become an active research area; however, existing results are confined to deterministic PDEs. Sampled-data controller design of stochastic PDEs is a challenging open problem. In this paper we suggest a solution to this problem for 1D stochastic diffusion-reaction equations under discrete-time nonlocal measurement via the modal decomposition method, where both the considered system and the measurement are subject to nonlinear multiplicative noise. We present two methods: a direct one with sampled-data controller implemented via zero-order hold device, and a dynamic-extension-based one with sampled-data controller implemented via a generalized hold device. For both methods, we provide mean-square L² exponential stability analysis of the full-order closed-loop system. We construct a Lyapunov functional V that depends on both the deterministic and stochastic parts of the finite-dimensional part of the closedloop system. We employ corresponding Ito's formulas for stochastic ODEs and PDEs, respectively, and further combine V with Halanay's inequality with respect to the expected value of V to compensate for sampling in the infinite-dimensional tail. We provide linear matrix inequalities (LMIs) for finding the observer dimension and upper bounds on sampling intervals and noise intensities that preserve the mean-square exponential stability. We prove that the LMIs are always feasible for large enough observer dimension and small enough bounds on sampling intervals and noise intensities. A numerical example demonstrates the efficiency of our methods. The example shows that for the same bounds on noise intensities, the dynamic-extension-based controller allows larger sampling intervals, but this is due to its complexity (generalized hold device for sample-data implementation compared to zero-order hold for the direct method). [ABSTRACT FROM AUTHOR]

Magnetic gears (MGs) emerged as an interesting alternative to conventional mechanical gears, owing mainly to their high torque densities and contactless operation. This paper presents a novel observer-based position control system for a magnetic-geared servo drive. The presented control system is based on two well established control strategies—field-oriented control (FOC) and state feedback control. The former is used to achieve effective torque control of a permanent magnet synchronous motor (PMSM) which is considered as an actuator that drives the high-speed rotor, whereas the latter is used to control the position of the low-speed rotor. A reduced-order extended state observer is used to estimate the position and speed of the low-speed rotor, thereby reducing the number of sensors required for the implementation of the controller. The whole control system is implemented on a microcontroller and tested on an existing prototype with a gear ratio of 18:1. The experimental results show that the presented control system guarantees precise positioning within a short amount of time and excellent disturbance rejection. [ABSTRACT FROM AUTHOR]

This paper presents a novel control strategy based on an uncertainty estimator for a class of fractional-order nonlinear systems characterized by a polynomial input. The proposed strategy allows the system to be controlled without resorting to transformations or approximate linearization. This is accomplished by using a fractional-order sliding-mode observer, whose task is to estimate certain portions of the state of the nonlinear system of a non-integer order, thus allowing the control law to counteract these elements to steer the system towards a desired behavior. To validate the performance of the proposed strategy, it was implemented, both in simulation and experimentally, to regulate the temperature of the cold side of a thermoelectric module fed by a DC/DC electronic power converter of the step-down type, a system that is known to have a nonlinear polynomial-type control input. [ABSTRACT FROM AUTHOR]

In this article, the bipartite containment control problem is considered for discrete-time linear descriptor multi-agent systems (DMASs) with multiple dynamic leaders under fixed signed digraph topology, in which each leader can be autonomous or evolving dynamically via communicating with other leaders in its neighbourhood. Based upon the properties of the solutions to discrete-time modified generalised algebraic Riccati equations(MGAREs), three different types of distributed observer-based protocols utilising only available local information are devised. Algorithms for constructing the devised protocols are also presented. Moreover, sufficient conditions ensuring the bipartite containment of the DMASs are established. Finally, the effectiveness of the presented protocols is validated by numerical simulations. [ABSTRACT FROM AUTHOR]

This paper is concerned with the input–output finite-time (IO-FT) stabilisation problem for a class of continuous-time periodic piecewise polynomial systems (PPPSs) with immeasurable states and external disturbances via state estimation-based robust reliable controller. Firstly, to reflect the actuality, a parameter uncertainty that exhibits the random nature and the actuator faults with nonlinear character are considered in the addressed PPPSs and the control scheme, respectively. In detail, the randomness of uncertain parameters is portrayed by the stochastic variable and it is presumed to pursue the Bernoulli distributions. Secondly, to estimate the immeasurable states of PPPSs, a periodic piecewise polynomial observer is designed depending on the output of PPPSs. The main intent of this article is to devise a state estimation-based robust reliable controller to ascertain the IO-FT stabilisation of the PPPSs. Moreover, by bridging the Lyapunov stability theory, linear matrix inequality technique and IO-FT stability theory, the required IO-FT stabilisation conditions in the frame of linear matrix inequality are procured for the system under consideration. Eventually, simulation results of the addressed PPPSs are shown in line with the proposed analytical findings, revealing the competence, inherent capability and utility of the devised control protocol. [ABSTRACT FROM AUTHOR]

This paper mainly deals with an observer-based control problem for the nonlinear reaction–diffusion systems subject to non-collocated output feedback. Different with the existing non-collocated controllers, the proposed methodology constructs a more general Lyapunov function with segmented spatial regions to guarantee the piecewise stabilization of nonlinear partial differential equations (PDEs) with multi-spatiotemporal states. The sufficient linear matrix inequalities (LMIs) condition is first derived by combining the improved Lyapunov direct method, Lipschitz condition, mean value theorem of integrals and a variant of Wirtinger's inequality to obtain the local gain matrices of collocated control. Further, a nonlinear PDEs observer-based piecewise controller is proposed to overcome the non-collocated distribution between finite piecewise actuators and sensors. Finally, a comparison simulation for the FitzHugh–Nagumo (FHN) system is presented to demonstrate the effectiveness and superiority of proposed non-collocated piecewise controller. [ABSTRACT FROM AUTHOR]

This paper investigates the observer‐based sampled‐data control problem for networked systems with consecutive packet dropouts. A new consecutive packet dropout model is established to describe the phenomenon of packet dropout in both the sensor‐controller (S‐C) and controller‐actuator (C‐A) channels. First, the considered system with observer‐based control scheme is studied in the discrete‐time domain by using equivalent discretization transformation. In order to simplify subsequent analysis, matrix exponential computation is employed to transform the discrete‐time system into a more tractable form. Then, the proposed new consecutive packet dropout model is taken into consideration to establish the stochastic mean square exponential stability condition. Furthermore, a novel two‐step synthesis approach is used to design the observer‐based controller. Finally, the effectiveness of the proposed observer‐based sampled‐data control approach is verified using a numerical example. In addition, the advantages of the proposed approach are validated through comparisons. [ABSTRACT FROM AUTHOR]

Wheeled Mobile Robots (WMRs) are systems with multiple industrial and civilian applications. Trajectory tracking is essential in many applications, such as surveillance, monitoring, and autonomous driving. However, in practical applications, a WMR is always affected by kinematic disturbances, state estimation error, and measurement noise, which may diminish the system's performance. Hence, this work proposes a novel observer-based H ∞ controller that is robust against matched and unmatched disturbances. The proposed methodology compensates for disturbances through a disturbance observer, transforming the closed-loop system into a new one affected by uniformly bounded disturbances. Then, an H ∞ controller is designed to make the WMR track a desired reference signal. A formal stability proof demonstrates the feasibility of the new proposal. Also, feedback and finite-time controllers are used to assess the novel controller. Numerical simulations and experimental results with a scaled autonomous car-like robot demonstrate the novel controller's efficiency and outstanding performance, despite disturbances when compared against finite-time and feedback controllers. [Display omitted] • An observer-based H ∞ controller for trajectory tracking of wheeled mobile robots is developed. • The kinematic model is transformed into decoupled systems, simplifying the control design stage. • The disturbances affecting the system are compensated through an observer. • Robust performance is achieved despite matched and unmatched disturbances. • The controller is validated through numerical simulations and experimental results. [ABSTRACT FROM AUTHOR]

For an Euler‐Bernoulli beam with variable coefficients, all the disturbances and references are supposed to be from an exosystem. Two observer‐based controls are proposed to regulate two non‐collocated outputs to track prescribed references. First, we construct an uncertain disturbance‐free beam system, which is determined by the inputs, measurable outputs, and unknown initial conditions. New exosystems are then defined to address the undetectability of the original exosystem and the uncertainties of input disturbances. We then propose two observer‐based controls through an extended observer for the disturbance‐free beam and the new exosystems. For the closed‐loop system, the tracking errors are proved to be exponentially regulated toward zero. A simulation example is provided to describe the theoretical result. [ABSTRACT FROM AUTHOR]

In this paper, a control method is presented for the six degrees of freedom (6-DoF) underwater systems. First, the proposed thruster voltage mapping control strategy of underwaters is proposed by combining the general model of the 6-DoF motion and the thruster dynamical model. Indeed, a novel control strategy is designed to be used for the 6-DoF underwater vehicle with various numbers of thrusters. The suggested technique is computationally simple by using only one control loop, and it overcomes problems arising from conventional methods. Second, an observer-based robust adaptive fuzzy estimator is presented to compensate for disturbance and uncertainties. [ABSTRACT FROM AUTHOR]

An observer-based control method for high-order fully actuated systems is proposed. First, a concept of exponentially stable observers is introduced, which, different from traditional state observers, requires not only asymptotic convergence of observation errors, but also exponential convergence. Further, inspired by existing results, two design methods for exponentially stable observers are developed, one of which is less conservative and the other is simpler and more straightforward to use. Secondly, a parametric control method based on the exponentially stable observer is proposed, which ensures the exponential stability of the closed-loop system. Moreover, the proposed method does not rely on the solution of nonlinear partial differential equations, and although the system is nonlinear and time-varying, the Separation Principle still holds under this control strategy, which is a significant advantage of the proposed method. Finally, the method is applied to the attitude control of flexible spacecraft with nonlinear inertia, and comparative simulation results verify the effect of the proposed approach.

Usually, simultaneous improvement of the transient performance and static accuracy is a challenging issue in saturated control systems. Employing an observer and the concept of composite nonlinear feedback, an integral controller is developed for constrained continuous-time systems. To achieve the control goal in the regulation purpose, a linear model is first derived by linearization about the operating point. Some parameters of the integral control are adjusted via the feedback passivation idea. The integral control law would be presented when a passivity condition is satisfied. Adding suitable damping terms to the existing one, the final controller is modified to enhance the response quality of the closed-loop system. The obtained results are evaluated in some numerical real examples. Although such a control method uses linearization, the outcomes of simulations, as well as the calculated performance indexes, discover the efficiency of the designed control system over the comparable ones. [ABSTRACT FROM AUTHOR]

For decades in the aerospace and control sciences, the Inertial Stabilized Platform (ISP) system has been studied to improve the accuracy of recipient photos or target tracking. This paper presents a nonlinear observer-based control method for three Degrees Of Freedom (3-DOF) ISP systems. First, a new formula of the state space equation for the 3-DOF ISP system is proposed to make this model suitable for designing an observer-based control. Then, by measuring the angular positions as output feedback, the angular velocities are estimated by the nonlinear observer, and Lyapunov-based nonlinear control techniques are used to design the observer. Furthermore, the exponential stability and convergence of the observer system are proved. Finally, the auxiliary control signal is considered so that the dynamics of the designed observer become a simple linear form and are easily controlled by the state feedback controller. Simulation results illustrate the effectiveness and feasibility of the proposed control strategy. [ABSTRACT FROM AUTHOR]

This paper investigates finite-time stability and observer-based finite-time control for nonlinear uncertain switched discrete-time system. Firstly, sufficient conditions are given to ensure that a class of switched nonlinear uncertain discrete-time system is finite-time stable under arbitrary switching. The observer-based controller is constructed. By constructing the switched Lyapunov function, sufficient conditions are derived to ensure the resulting closed-loop system is finite-time stable via observer-based control. The observer-based controller is designed to guarantee a switched nonlinear discrete-time system is finite-time stabilized. Finally, two numerical examples are given to illustrate the effectiveness of the proposed results. [ABSTRACT FROM AUTHOR]

This paper presents the design of an observer-based quadratic boundedness protocol for leader-following consensus in multi-agent systems. The problem under consideration is to force all the agents to follow the trajectories of a virtual leader in spite of bounded disturbances which implies that the leader-following consensus is reached in a positively invariant and attractive ellipsoid. Under the framework of control synthesis in multi-agent systems subject to bounded disturbances, linear matrix inequality-based sufficient conditions are obtained for the computation of the controller and observer gains. The effectiveness of the proposed approach is demonstrated through simulations in a fleet of unmanned aerial vehicles subject to wind turbulence which are shown to achieve formation control. [ABSTRACT FROM AUTHOR]

This paper addresses the leader-following formation control problems for generic linear multi-agent systems under directed topology with designable inter-event time. A synthesis approach combining controller and observer design is developed under a dynamic event-triggered communication and control scheme. The proposed feedback control, state estimation, and event-triggered rules are distributed, and only local information is required for each agent to implement these algorithms. The proposed dynamic event-triggered protocol incorporates model-based estimation and clock-like auxiliary dynamic variables to prolong the inter-event time and economize the network resources. Furthermore, the inter-event time is designable, which allows more flexible tuning of communication frequency with only minor performance degradation. Sufficient conditions for formation control are established by linear matrix inequalities. The proposed method exhibits significant improvement over the dynamic event-triggered control methods described in the existing literature. Compared to the existing static event-triggered strategy, the proposed approach significantly reduces the utilization of communication resources while preserving asymptotic convergence to the desired formation. Comparative simulations demonstrate the validity and effectiveness of the proposed theoretical results. [ABSTRACT FROM AUTHOR]

Large wind turbines have typically poorly damped structures. Hence, the absence of damping leads to aeroelastic oscillations, and the operational rotor speed can approach the critical rotor speed. By using damping injection, the control system can actively introduce some additional damping. In the present work, a control approach to reduce oscillations of the rotor blades in the edgewise direction is proposed. The concept is based on the damping injection mechanism, and an additional level of safety is obtained by introducing the Dynamic Safety Margin (DSM) in the control law. The feedback control scheme requires some unmeasurable variables. This aspect is covered by using an interval observer. The control approach is tested by using simulations on a high-definition model implemented in an aeroservoelastic code. Simulation results are very satisfactory and promising for future experiments using hardware-in-the-loop equipment.

Magnetic gears (MGs) emerged as an interesting alternative to conventional mechanical gears, owing mainly to their high torque densities and contactless operation. This paper presents a novel observer-based position control system for a magnetic-geared servo drive. The presented control system is based on two well established control strategies—field-oriented control (FOC) and state feedback control. The former is used to achieve effective torque control of a permanent magnet synchronous motor (PMSM) which is considered as an actuator that drives the high-speed rotor, whereas the latter is used to control the position of the low-speed rotor. A reduced-order extended state observer is used to estimate the position and speed of the low-speed rotor, thereby reducing the number of sensors required for the implementation of the controller. The whole control system is implemented on a microcontroller and tested on an existing prototype with a gear ratio of 18:1. The experimental results show that the presented control system guarantees precise positioning within a short amount of time and excellent disturbance rejection.

This work studies the prescribed‐time robust consensus tracking problem of heterogeneous multi‐agent systems over directed graphs. Aiming at multi‐agent systems with a static leader and only matched disturbances, a distributed observer‐based consensus algorithm is developed, to ensure that the tracking errors converge to zero accurately in prescribed time. For the case of multi‐agent systems with a dynamic leader and mismatched/matched disturbances, an adaptive strategy based on a distributed observer and a disturbance observer is designed by the dynamic damping reciprocal technology. Such strategy can avoid the numerical singularity, adapt to the situation that the upper bounds of the disturbances are unknown, and assure that the tracking errors converge to an adjustable neighborhood of zero within prescribed time. Finally, simulations are given to verify the effectiveness of the proposed control strategies. [ABSTRACT FROM AUTHOR]