Search

Actuator constraints, particularly saturation limits, are an intrinsic and long‐standing problem in the implementation of most control systems. Model reference adaptive control (MRAC) is no exception and it may suffer considerably when actuator saturation is encountered. With this in mind, this paper proposes an anti‐windup strategy for model reference adaptive control schemes subject to actuator saturation. A prominent feature of the proposed compensator is that it has the same architecture as well‐known nonadaptive schemes, namely model recovery anti‐windup, which rely on the assumption that the system model is known accurately. Since, in the adaptive case, the model is largely unknown, the proposed approach uses an "estimate" of the system matrices for the anti‐windup formulation and modifies the adaptation laws that update the controller gains; if the (unknown) ideal control gains are reached, the model recovery anti‐windup formulation is recovered. The main results provide conditions under which, if the ideal control signal eventually lies within the control constraints, then the system states will converge to those of the reference model, that is, the tracking error will converge to zero asymptotically. The article deals with open‐loop stable linear systems and highlights the main challenges involved in the design of anti‐windup compensators for model‐reference adaptive control systems, demonstrating its success via a flight control application. [ABSTRACT FROM AUTHOR]

This article describes a research study on an electromechanical system with saturation, where a fuzzy hybrid controller with integral action and anti-windup is applied. The study focuses on implementing this Integral Fuzzy Logic Controller (IFLC) on a Field-Programmable Gate Array (FPGA) board. The fuzzy controllers, known for their effectiveness in handling disturbances and saturations, are used in a parallel structure. To optimize the performance of the controller, the Particle Swarm Optimization (PSO) technique is employed to tune the membership functions and feedback loop gains. The complex algebraic concepts and Type 1 fuzzy logic algorithms are transformed into mathematical equations suitable for VHSIC Hardware Description Language (VHDL). The proposed controller is co-simulated using Vivado and Xilinx® System Generator (XSG) tools on both software and hardware platforms. The utilization of fixed-point data propagation in the controller's structure ensures optimized implementation methods. The performance index of our controller surpasses that of a conventional Proportional-Integral-Derivative (PID) controller, demonstrating superior efficacy in regulating the system dynamics. To verify the efficacy of the proposed control strategy, a thorough comparison is done using control simulations between it and previous PID systems. The results show a 31% decrease in speed overshoot. [ABSTRACT FROM AUTHOR]

Real‐world nonlinear control systems (e.g., robots) are influenced dynamically by backlash and saturation. However, it is lacking of a control design tool with a sound theory to deal with these phenomena and achieve optimal finite‐time stability simultaneously. To this end, we propose a novel anti‐windup and backlash compensation‐based finite‐time control (AWBC‐FTC) method for an unsolved control task of a general class of unstable nonlinear systems under input saturation and backlash nonlinearity. It includes a compound control structure with two layers where the upper switches two control modes and the lower regulates the system in either the backlash mode or the contact mode. New stability theory together with parameter optimization algorithms are also proposed to support new design approaches of two sub‐controllers where the adversary effects of input saturation and backlash are eliminated and the optimal finite state stability under a guaranteed domain of attraction is achieved. Experimental results on a benchmark robot system verify the advantages of the proposed design tools over the other in terms of a bunch of transient and stability measures. Therefore, the work enriches both theory and design of nonlinear systems for a challenging control objective. [ABSTRACT FROM AUTHOR]

This paper studies a class of input-saturated nonlinear systems with Lipschitz condition. We combine the fully actuated system approach with anti-windup control to design control system. The proposed control method has the advantages of both fully actuated system approach and anti-windup control. The main advantages are: (1) establishing a fully actuated system approach control framework based on anti-windup control. The controller of the nonlinear system can be written out immediately when a fully actuated system (FAS) model or a group of FAS models of the system is derived, simplifying the steps of control system analysis and design; (2) many actual systems are FAS models, and there is no need to convert the system into a state space model; (3) the anti-windup compensator works only when the actuator saturation occurs to ensure the stability of the control system. In fact, most of the time, the system operates in an unsaturated state, which means that in most cases, the system performance is not affected. A numerical simulation example is given to illustrate the effectiveness of the proposed method. [ABSTRACT FROM AUTHOR]

Copyright of Journal of Southeast University (English Edition) is the property of Journal of Southeast University Editorial Office and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

This paper investigates an anticipatory activation anti-windup approach based on Linear Active Disturbance Rejection Control (LADRC) to address the influences of accelerated saturation on the actuators in a Miniaturized Inertial Stabilized Platform (MISP) with extreme external disturbance. The proposed method aims to eliminate the high-frequency vibrations on the Line of Sight (LOS) of electro-optical devices during actuator saturation. To achieve this, the Linear Extended State Observer (LESO) is modified by adding saturation feedback to the total disturbance observed state variable, which is operated as an anticipatory activation anti-windup compensator. The stability of the proposed controller is discussed, and the gains are optimized by the Linear Matrix Inequality (LMI) constraints though quadratic programming and an H-infinite performance indicator. Additionally, as the multiple activated scheme for anti-windup, the effectiveness of immediate activation in dealing with accelerated saturation is compared and analyzed. These comparisons and verification are implemented through simulations, where the external disturbance is introduced using recorded attitude data from USV sailing. Finally, experiments are conducted on an MISP for a visual tracking system, demonstrating that the anticipatory activation mothed effectively suppresses high-frequency vibrations on the LOS during instances of accelerated saturation. [ABSTRACT FROM AUTHOR]

Copyright of Electric Machines & Control / Dianji Yu Kongzhi Xuebao is the property of Electric Machines & Control and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

As it is known, the operation of electrolyzers with variable currents allows for a reduction in green hydrogen production costs. Indeed, operating electrolyzers as variable loads enables the better use of renewable energy resources but also contributes to the power quality of the network where electrolyzers are connected. However, with extreme winds such as those in Patagonia, this mode of operation affects the lifetime of the equipment. In this regard, this work considers the variable operation mode of electrolyzers, but also, for preserving their lifetime, a control strategy based on concepts of Passivity and anti-windup is presented. Time responses over realistic wind show good behaviors of the technique and demonstrate the possibility of maximizing the contribution of electrolyzers to the electrical grid. [Display omitted] • Electrolyzers operating as variable loads reduce green H2 cost production. • Electrolyzers as smart loads improve the quality of the power grid. • Extremum wind changes affect the electrolyzer lifetime. • The proposal preserves the lifetime of electrolyzers. • The proposed control combines Passivity, PI control and anti-windup concepts. [ABSTRACT FROM AUTHOR]

The aim of this study is to offer a way for dealing with the stabilization of discrete delayed systems with missing measurements using an anti-windup compensator. Linear matrix inequalities are used to establish a set of sufficient conditions based on the Lyapunov–Krasovskii function that ensure the asymptotic stability of the system through the anti-windup controller and the performance of the H ∞ norm. A characterization of the stability domain is also given. Numerical examples are given to contrast with previous studies, and show the efficiency of our methodology in obtaining the largest estimated domain of attraction, upper bounds of the delay as well as the minimum value of performance attenuation H ∞ , which means that our approach gives less conservative results than the other methods. [ABSTRACT FROM AUTHOR]

Over the last decade, industrial applications and promising research domains including robotics and automotive engineering have adopted the rotary switched reluctance actuator (SRA). SRA's fault tolerance, simple, strong structure, and high-frequency operation make it popular. However, the SRA's nonlinear magnetic flux flow and saturation operation negate its benefits. Several control systems have been developed; however, they often need extensive mechanism models and advanced control theory, making them impracticable. This paper proposes a modified proportional integral derivative (PID) controller to evaluate the control performance, which comprises of PID controller with an anti-windup, a linearizer unit, and switching mechanism to activate the SRA phases. The linearizer unit aids to compensate for the nonlinear current-displacement relationship. The anti-windup element helps to halt the integral action during the starting motion. At the fully aligned position, 60°, the modified PID reduced positioning steady-state error by 4.3 times at 76.9%, overshoot by 48.8%, and settling time by 25.3%. Both the modified PID and conventional PID showed zero steady-state error at intermediate position, 70°, however the modified PID controller depicted an improved percentage overshoot by 54.5% and settling time by 74.5%. The results show that the modified PID outperforms conventional PID in transient response, steady-state error, overshoot, and settling time. [ABSTRACT FROM AUTHOR]

Copyright of Electric Machines & Control / Dianji Yu Kongzhi Xuebao is the property of Electric Machines & Control and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

In this digital era, the basis of every smart instrument is discrete signal models e.g. in Networked control systems, Cyber physical systems etc. It has been shown that time-delays are unavoidable during the digital implementation of an engineering system. Therefore, the stabilization of discrete time delayed systems is gaining the high importance [1–10]. Although a lot of literature is found on the stabilization of time delayed systems for a long time using the construction of proper non-negative Lyapunov functional. Recalling some existing results on this issue, the LMI-based stability conditions are obtained by its forward difference negative-definite in direction to claim the less conservative results [15–25]. In order to seek less conservative stability criteria, this paper introduces an anti-windup scheme appended with Wirtinger inequality, reciprocal convex approach and delay partitioning of a discrete-time delayed systems by using Lyapunov Krasovskii functional. To accomplish this task, delay partitioning technique may be utilized to develop improved stability conditions for the considered system. The Wirtinger-based inequality and reciprocal convex approach has been employed to derive less conservative results. On employing the delay partitioning, a novel linear matrix inequality-based criterion is proposed to stabilize such systems. The considered Lyapunov-Krasovskii functional includes the information of intermediate delay to acknowledge the delay information implicitly that ensures the considered system to be regular, impulse free and stable in terms of linear matrix inequalities. The estimation of the attraction basin is to ensure that the state remains inside the level set of a certain Lyapunov function. Numerical simulation verifies that the presented method reduces conservatism than the existing results. [ABSTRACT FROM AUTHOR]

This paper addresses the design of a dynamic output feedback-based anti-windup compensator to mitigate the windup phenomenon for a discrete time-varying delayed system with input saturation to establish the asymptotic stability. Linear matrix inequalities–based stability conditions are derived locally and globally. The controller for the closed-loop system is designed to reduce the effect of external bounded disturbances by utilizing the linear matrix inequality approach. The novel triple Lyapunov–Krasovskii functional along with reciprocal convex inequality is used to solve the expressions contained in the forward difference of the functional and to maximize the basin of attraction. Finally, industrial examples are simulated to prove the effectiveness of the proposed criterion. [ABSTRACT FROM AUTHOR]

This paper investigates an anticipatory activation anti-windup approach based on Linear Active Disturbance Rejection Control (LADRC) to address the influences of accelerated saturation on the actuators in a Miniaturized Inertial Stabilized Platform (MISP) with extreme external disturbance. The proposed method aims to eliminate the high-frequency vibrations on the Line of Sight (LOS) of electro-optical devices during actuator saturation. To achieve this, the Linear Extended State Observer (LESO) is modified by adding saturation feedback to the total disturbance observed state variable, which is operated as an anticipatory activation anti-windup compensator. The stability of the proposed controller is discussed, and the gains are optimized by the Linear Matrix Inequality (LMI) constraints though quadratic programming and an H-infinite performance indicator. Additionally, as the multiple activated scheme for anti-windup, the effectiveness of immediate activation in dealing with accelerated saturation is compared and analyzed. These comparisons and verification are implemented through simulations, where the external disturbance is introduced using recorded attitude data from USV sailing. Finally, experiments are conducted on an MISP for a visual tracking system, demonstrating that the anticipatory activation mothed effectively suppresses high-frequency vibrations on the LOS during instances of accelerated saturation.

In this paper, the problem of guaranteed cost control and anti-windup design is studied for a class of switched systems with actuator saturation. The switching strategy and anti-windup compensator are designed to ensure the asymptotic stability of the closed-loop system and to obtain the minimum upper bound of the cost function. Some sufficient conditions for the existence of an anti-windup compensator of guaranteed cost are given by using the multiple Lyapunov functions method. On this basis, the minimum upper bound of the cost function is determined by solving the optimisation problem under the constraint of linear matrix inequality (LMI). Finally, a numerical example is given to verify the effectiveness of the proposed method. [ABSTRACT FROM AUTHOR]

This work presents a reference conditioning anti‐windup scheme based on passivity control theory. The main closed‐loop is controlled by a proportional–integral–derivative (PID) control, and the injection and damping assignment technique ensures that PID variables are compatible with the process input. In the proposed algorithm, a fictitious actuator, modeled as a first‐order filter, is incorporated to estimate the rate of change and the output of the actuator device. Amplitude and rate constraints are weight by coefficients that shape the energy function of the anti‐windup scheme. Finally, to show how the algorithm can cope with the windup problem, simulation results are presented. Even when shown the results on a linear PID, the proposal can extend to any linear or nonlinear control in the main control loop. [ABSTRACT FROM AUTHOR]

Copyright of Control Theory & Applications / Kongzhi Lilun Yu Yinyong is the property of Editorial Department of Control Theory & Applications and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Chemical processes use to be non-minimum phase systems. Thereby, they are a challenge for control applications. In this paper, fuzzy state feedback is applied in the Van de Vusse reaction that has an inverse response. The control design has an integrator to enhance the control performance by eliminating the steady-state error when a step reference is applied. An anti-windup action is used to reduce the undershoot in the system response. In practice, it is not possible to have always access to all the state variables. Thus, a fuzzy state observer is implemented via LMIs. Frequently, the papers that show similar applications present some comments about disturbance rejection. To eliminate the steady-state error when a ramp reference is used, in this work, a second integrator is aggregated. Now, the anti-windup also reduces the overshoot generated due to the usage of two integrators in the final application.

The control synthesis of a high-speed supercavitating vehicle (HSSV) faces many difficulties such as the stability, control, and maneuvering with dynamical uncertainties due to parameter perturbations, external disturbances, unmodeled dynamics, measurement noises, and actuator constraints. Inspired by the HSSV dynamical analysis, this paper proposes the H∞ (i.e. ''H-infinity'') robust control synthesis to generate a robust low-order controller, which is intended for real implementations to ensure active control actions. Particularly, the presented control scheme includes a feedback component and an anti-windup compensator. The anti-windup synthesis is to provide system stability under actuator saturations. Extensive simulations show that the designed controller provides good performances with high robustness for vertical plane manoeuver while effectively eliminating planning forces, exogenous disturbances and noises as well as overcoming cavitator saturations.

On the basis of the fact that all signals in the practical system are always bounded, this paper proposes a practical QFT-based approach for the synthesis of anti-windup compensation for uncertain LTI systems. Meanwhile, a modified version of the circle criterion is developed for saturated systems with parametric uncertainty to reduce the conservativeness of the anti-windup compensator design within the non-interfering anti-windup framework. In the context of QFT, it means enlarging the allowed zone of the compensator remarkably in the Nichols chart compare to the traditional version of the circle criterion. As a result, the less conservative stability boundary provides more room for the compensator synthesis, making the performance improvement possible. Numerical examples demonstrate the effectiveness and the performance improvement as expected of the proposed technique based on QFT for the anti-windup compensator design. [ABSTRACT FROM AUTHOR]

In addition to the difficulty of system modeling, every physical system faces actuator saturation, making the real control different from the controller output (desired control input). When this occurs, the controller output does not regulate the system properly and errors occur as a result of incorrect updating. This is known as the windup phenomenon. In the event that the controller is configured to override actuator saturation, it can lead to a failure in the controller's performance, such as large overshoots, high response time, and even system instability in the worst case. Therefore, in this paper, a new robust model-free controller method is proposed. It is a combination of four nonlinear control techniques, namely model-free controller, fractional-order sliding mode controller, fractional integral–proportional (PI) controller, and anti-windup compensator, which gives rise to the new model-free controller algorithm called hybrid fractional-order intelligent PI fractional sliding mode controller with an anti-windup compensator termed (MF-FOiPI-FOSMC-AW). However, to illustrate the effectiveness of the new proposed MF-FOiPI-FOSMC-AW method, simulation and experimental results compared to classical PI and iPI controllers (with and without an anti-windup compensator) on a hydraulic system are presented in the presence or absence of external disturbances for different types of references. Finally, simulation is conducted through an experimental comparison of the proposed approach with other strategies such as the classical anti-windup PI controller and the anti-windup intelligent PI controller, which is carried out for this purpose. [ABSTRACT FROM AUTHOR]

This paper investigates a nonlinear output feedback fault-tolerant control method for the hypersonic flight vehicles with non-affine actuator faults. Compared to the existing investigations, with little aerodynamic knowledge, the proposed controller tackles three practical issues simultaneously, including the inaccurate onboard measurements of the flow angles, unknown non-affine actuator faults and actuator saturation. Drawing support from the differentiator technique, an estimation method for the unmeasured flight path angle is devised, and then an available transformed error variable is defined to construct control laws. Tracking differentiators are introduced to establish uncertainty observers for estimating the unknown model functions including the influences caused by the non-affine actuator faults, and tackle the "explosion of terms" inherent in backstepping. Besides, to improve the controller's performance when the actuator saturation happens, a novel anti-windup strategy is developed to settle the problem that many existing anti-windup strategies are not workable if the non-affine actuator faults happen. Finally, comparative simulation results are provided to demonstrate the effectiveness and superiority of the proposed method. • Three usual practical issues existing in HFV control are tackled simultaneously. • Superior result can be obtained even if the actuator faults and saturation happen. • A novel anti-windup strategy is devised considering actuator faults. • The proposed method is established with almost no aerodynamic knowledge. [ABSTRACT FROM AUTHOR]

In this article, the robust control problem of uncertain nonlinear systems subject to magnitude and rate saturation (MRS) is investigated via active disturbance rejection control. To this purpose, we propose a novel robust controller that involves an improved extended state observer (IESO), a composite loop, and two anti-windup loops. The IESO is designed to estimate the state and the total disturbance, which includes the uncertain dynamics and external disturbance. Compared with the traditional ESO, IESO absorbs an anti-windup loop to ensure accurate estimation under MRS. The convergence analysis of IESO is further carried out to theoretically verify the accurate estimation of IESO. The composite loop is generalized to cancel the total disturbance based on the output of IESO. Moreover, a rate anti-windup loop is designed to attenuate the effect of rate saturation on the estimation/cancellation of total disturbance. An algorithm for anti-windup gains computation is correspondingly established, in order to minimize the effect of external disturbance in terms of $L_{2}$ gain while guaranteeing the local asymptotic stability. Finally, the proposed method is applied to aeroengine, which involves large uncertainty and suffers from disturbance and MRS. The experimental results verify the effectiveness of the proposed method. [ABSTRACT FROM AUTHOR]

The aim of this paper is to present a robust anti-windup compensator methodology to deal with the stabilization of nonlinear time-varying delay systems, which are described by Takagi–Sugeno (T–S) fuzzy models. Given a stabilizing output feedback fuzzy controller, an anti-windup control approach is developed to estimate the domain of attraction. Based on the Lyapunov–Krasovskii functional and delay-dependent analysis, sufficient conditions for the robust stabilization via anti-windup controller are derived in terms of linear matrix inequalities. In addition, an algorithm is provided to optimize the anti-windup gain and reduce the conservatism. Numerical examples illustrate the effectiveness of our methodology and show the improvements over the existing ones. [ABSTRACT FROM AUTHOR]

The attitude control of an underactuated reusable launch vehicle (RLV) in the reentry phase involving nonminimum phase problem and control input constraints is investigated in this article. To address the nonminimum phase problem, an approach combining output redefinition and robust backstepping is proposed, where a synthetic output is constructed using the combination of the original output and the internal states to obtain stable zero dynamics, and then robust backstepping is performed on the new output. Besides, the ideal internal dynamics are obtained by using optimal bounded inversion, which are incorporated into the controller as the reference trajectories for the internal states to improve the output tracking accuracy. To cope with the control input constraints, a simple and useful anti-windup strategy is proposed by using feedback error clipping, which is shown to be very effective in mitigating control input saturation. Numerical simulations are given to validate the effectiveness of the proposed method. [ABSTRACT FROM AUTHOR]

This paper considers the guaranteed cost control and anti-windup design problem for a class of discrete-time saturated switched systems. The switching strategy and anti-windup compensators are designed, for guaranteeing that the considered system is asymptotically stable and simultaneously the minimised upper-bound of cost function is obtained. By using the multiple Lyapunov functions method, we derive some sufficient conditions about the existence of anti-windup compensation gains of guaranteed cost. Furthermore, the minimised upper-bound of cost function is determined by solving an optimisation problem in terms of linear matrix inequalities constraints. Finally, a numerical example is given to show the effectiveness of the proposed method. [ABSTRACT FROM AUTHOR]

Delay and actuator saturation are inevitable in practical control engineering, which may lead to system performance degradation, or even divergence of controlled variables. Combination of Smith predictor (SP) and model recovery anti-windup method is an effective solution to anti-windup synthesis for linear delayed systems, but model-dependent property brings obstacles for the application and promotion. To overcome such a difficulty, a few-shot data-driven approach has been proposed in this paper, and operating data are collected to simultaneously tune feedback controller parameters and estimate internal model applied in SP. Subsequently, the anti-windup compensator is constructed with the estimated model and compensator gain is calculated by using the Lyapunov equation. Finally, the effectiveness of the proposed method is verified through simulations that implemented three typical processes in engineering. [ABSTRACT FROM AUTHOR]

Error Governor (EG) deals with the problem of dynamically modifying the feedback error driving a controller having bounded control signals, for preventing controller or actuators saturation, avoiding integrator and/or slow dynamics windup and preserving the nominal linear controller behaviour. In this paper, an optimisation-based EG scheme is proposed for discrete-time Proportional–Integral–Derivative (PID) controllers driving Single-Input Single-Output (SISO) plants. The PID controller is considered in state-space form, and this formulation is used to pose the EG problem as a constrained quadratic program (QP). Because the QP problem is subject to inequality constraints related to controller saturation, in order to use the proposed scheme in real-world applications, it should be necessary to consider appropriate algorithms for efficiently solving the optimisation problem. An efficient way to efficiently compute the solution of the EG problem is presented, reducing the computational effort required to solve the EG QP for using the proposed scheme in real control loops with high sampling rate. An analysis of control performance and computational burden is provided, comparing in simulation studies the optimal EG scheme performance with respect to control results provided by saturated PID with and without anti-windup action. [ABSTRACT FROM AUTHOR]

This article proposes a controller using Fuzzy Model Predictive Control (FMPC) and a fuzzy state observer applied to a three states switching cell (3SSC) boost converter. The proposed approach is an observer-based output feedback fuzzy MPC, which combines a state feedback FMPC controller with a fuzzy state observer. Moreover, a stability criterion is developed for the controller-observer procedure, considering a Takagi-Sugeno (T-S) fuzzy model, a PDC fuzzy control law, a fuzzy state observer and a state feedback FMPC, through the Linear Matrix Inequalities (LMI) optimization procedure. Furthermore, an Anti-Windup (AW) procedure is added to the control scheme. The proposed procedure is implemented for a boost converter through computer simulation, and the obtained results are compared with two MPC controllers. The analysis is done considering the time response and some performance indexes, moreover, the robust stability for the studied controller is explicit using stability ellipsoids. [ABSTRACT FROM AUTHOR]

This article presents a novel framework for the output regulation of rational nonlinear systems subject to input saturation, where the controller structure is composed by an internal model generator in series with an output feedback stabilizing stage. In order to address the effects of control saturation, we propose the use of an anti‐windup compensation loop into both internal model and stabilizing control stages. Given prior knowledge of the system zero‐error steady‐state condition and a proper internal model, we cast the regulation error dynamics in a differential‐algebraic form, which leads to matrix inequalities conditions that ensure closed‐loop stability and exponential transient performance. Optimization problems are then proposed to simultaneously compute the stabilizing controller and the anti‐windup gains such that a domain of attraction estimate is maximized. [ABSTRACT FROM AUTHOR]

This paper focuses on the design of a disturbance rejection controller for a tailless aircraft based on the technique of nonlinear dynamic inversion (NDI). The tailless aircraft model mounted on a three degree-of-freedom (3-DOF) dynamic rig in the wind tunnel is modeled as a nonlinear affine system subject to mismatched disturbances. First of all, a baseline NDI attitude controller is designed for sufficient stability and good reference tracking performance of the nominal system. Then, a nonlinear disturbance observer (NDO) is supplemented to the baseline NDI controller to estimate the lumped disturbances for compensation, including unmodeled dynamics, parameter uncertainties, and external disturbances. Mathematical analysis demonstrates the convergence of the employed NDO and the resulting closed-loop system. Furthermore, an anti-windup modification is applied to the NDO for control performance preserving in the presence of actuator saturation. Subsequently, the designed control schemes are preliminarily validated and compared via simulations. The baseline NDI controller demonstrates satisfactory attitude tracking performance in the case of nominal simulation; the NDO augmented NDI controller presents significantly improved ability of disturbance rejection when compared with the baseline NDI controller in the case of robust simulation; the anti-windup modified scheme, rather than the baseline NDI controller nor the NDO augmented NDI controller, can preserve the closed-loop performance in the case of actuator saturation. Finally, the baseline NDI scheme and the NDO augmented NDI scheme are implemented and further validated in the wind tunnel flight tests, which demonstrate that the experimental results are in good agreement with that of the simulations. [ABSTRACT FROM AUTHOR]

Abstract The problem of chatter vibration is associated with adverse consequences that often lead to tool impairment and poor surface finished in a workpiece, and thus, controlling or suppressing chatter vibrations is of great significance to improve machining quality. In this paper, a workpiece and an actuator dynamics are considered in modeling and controller design. A proportional-integral controller (PI) is presented to control and actively damp the chatter vibration of a workpiece in the milling process. The controller is chosen on the basis of its highly stable output and a smaller amount of steady-state error. The controller is realized using analog operational amplifier circuit. The work has contributed to planning a novel approach that addresses the problem of chatter vibration in spite of technical hitches in modeling and controller design. The method can also lead to considerable reduction in vibrations and can be beneficial in industries in term of cost reduction and energy saving. The application of this method is verified using active damping device actuator (ADD) in the milling of steel.

In this study, an anti-windup reconfigurable control method is developed for dynamic positioning vessel in the presence of thruster faults and input saturation. The designed reconfiguration block acting as a virtual thruster aims at hiding the faults from the nominal controller. Also, it is added into the closed-loop system between the nominal controller and the dynamic positioning system. A thruster saturation-failure fault matrix technique is proposed to regard the thruster saturation as thruster fault, meanwhile an auxiliary system is constructed to achieve extra compensation for the adverse effects induced by input saturation. Furthermore, an integral sliding mode control method is presented to accommodate the nonlinear items in the reconfiguration block. An adaptive technique is also employed to preserve robustness against the unknown uncertainties. Finally, a vessel dynamic positioning control process is adopted to evaluate the effectiveness of the proposed method. [ABSTRACT FROM AUTHOR]