Anti-windup Research Articles

Stability analysis and anti-windup design of saturated switching systems based on multiple Lyapunov functions

Abstract In this paper, employing advanced multiple Lyapunov functions (MLF) technology, we conduct a thorough investigation into the fault-tolerant characteristics of actuator saturation-based systems, particularly those prone to failures. Based on this comprehensive analysis, we carefully design an anti-windup (AW) controller, incorporating an efficient AW compensator and precisely calibrated gains for the dynamic state feedback controller, tailored to meet the specific needs of practical control systems. To further demonstrate the effectiveness of our approach, we also provide a detailed numerical example.

Impact of strength of fault current path on the operation of decoupled double synchronous reference frame – phase locked loop

This paper studies the performance of decoupled double synchronous reference frame - phase locked loop (DDSRF-PLL) synchronizing method during grid fault. The study is carried out using Matlab/Simulink. The contribution of the paper is to reveal that if the DDSRF-PLL proposed in many papers is used, the control system of network side converter (NSC) may become unstable during a symmetrical grid fault. The instability problem appears only when certain tuning parameters of DDSRF-PLL are used and the fault current path is weak. Thus, the problem may not be easily detected. This paper emphasizes that it is mandatory to use PI-controller with integrator anti windup in the loop filter of DDSRF-PLL. In addition, the impact of angular frequency limitation range on the fault ride through performance is evaluated with comparative simulations.

Power Quality Improvement using a New DPC Switching Table for a Three-Phase SAPF

This research focuses on the analysis and design of robust direct power control (DPC) for a shunt active power filter (SAPF). The study proposes a novel switching table design based on an analysis of the impact of inverter switching vectors on the derivatives of instantaneous reactive and active powers. The goal is to reduce the number of commutations by eliminating null vectors while maintaining the desired DC-bus voltage using a PI regulator-based anti windup technique. Additionally, a robust PLL structure-based band pass multivariate filter (BPMVF) is utilized to enhance the network voltage. The research demonstrates the effectiveness of the suggested power control through extensive simulation results, showing high performance in both transient and steady-state conditions. The proposed approach offers the advantages of sinusoidal network current, and unitary power factor, and eliminates the need for current regulators and coordinate transformations or PWM generators. Further research directions could explore the practical implementation and real-world performance of this technique in power systems.

A sensorless anti-windup speed control approach to axial gap bearingless motors with nonlinear lumped mismatched disturbance observers

In this paper, sensorless robust speed control with nonlinear lumped mismatched disturbance observers for a permanent magnet type axial gap bearingless motor (AGBM) is designed. Multistage anti-windup-based dynamic surface control combined with integral backstepping control is proposed to control the motor’s axial displacement and rotor speed. The approach is against parameter uncertainties and external disturbances, improving steady-state accuracy, eliminating the derivative explosion phenomenon, no chattering problem, and reducing the magnitude of the control system when current saturation occurs. In addition, a novel nonlinear lumped mismatched disturbance observer is proposed to improve the approach under unmodeled dynamics and external disturbances. To obtain high-accuracy tracking control, the control system includes the robust controller combined with the disturbance observers and anticipatory activation of anti-windup (AW) compensation, which means the controller is more complex. Then, to design a sensorless robust speed control for the motor, the rotor position and speed observer require higher accuracy. High-gain back-EMF observer combined with an improved phase-locked loop is proposed to estimate rotor angular position and speed even when the motor speed is reversed. Overall stability of closed-loop system control, including a sensorless speed control approach for motors using back-EMF estimation combined with saturation of the currents and lumped disturbance observers, is mathematically proven. Finally, the simulation results under measurement noise show that the proposed control system are obtained the effectiveness, feasibility, and robustness.

Offline output feedback robust anti-windup MPC-LPV using relaxed LMI optimization

This paper addresses a new technique of constrained output feedback robust model predictive control (RMPC) with anti-windup (AW) synthesis adopting linear parameter varying state-space (LPV-SS) systems via relaxed linear matrix inequalities (LMI) procedure. We proposed an output feedback control design with a conservatism reduction, including a robust AW-LPV synthesis to solve the robust stability under saturated signal control mode. Lyapunov stability functions through the LPV emphasis are considered. To evaluate the efficiency of the proposed method, we presented a time response analysis, closed-loop z-plane, worst-case upper bound, and we compared the performance of the proposed method with some MPC benchmarks using a numerical example.

Optimized Anti-Windup Coordinating Strategy for Torque-Maximized High-Speed Flux-Weakening Operation of Constrained Induction Motor Drives

Due to the contradiction between torque-maximized requirements and limited voltage and current constraints, voltage closed-loop flux-weakening strategy is developed to circumvent the saturation problem for maximum torque control of induction motor when the accelerating speed enters high-speed region. At the same time, since voltage inconsistency caused by the saturation is employed to construct flux-weakening controller (FC), anti-windup (AW) item in current regulator needs to be cut off to avoid the conflict. However, the replacement discards part of AWs utility and results in the distortion of command voltage, thus compromising system’s dynamic performance and making the tuning process of proportional-integral controller (PI)-based FC much trickier. To address this issue, an equivalent saturation model is presented. An optimized AW coordinating strategy is proposed, combining a novel structure, so-called virtual voltage buffer, with FC. Through an equivalent proof, it can be transformed into over-modulation block for a convenient implementation. Through its compensation in the transient period, <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$d$ </tex-math></inline-formula> -axis current can be quickly and smoothly manipulated in a more concise tuning process. As a result, the overall system possesses a fast acceleration capability with maximum torque and a wide speed range, while retaining a desirable system response. Simulation and experimental results verify the effectiveness of proposed method.

Robust induced [formula omitted] optimal control of discrete-time systems having magnitude and rate-bounded actuators

The design of robust state- and output-feedback control for uncertain discrete-time systems with physical magnitude and rate constraints on their actuator dynamics was addressed. Unlike the traditional methods such as anti-windup (AW) methods, nested ellipsoids, model predictive controllers (MPCs) and integral quadratic constraints(IQCs) formulated by sector bounded inequalities, this paper uses a transformation of the system dynamics to a form which considers control signal and its rate as controlled outputs and using discrete-time ℓ∞ induced (peak-to-peak) norm from disturbance inputs to these outputs. To cope with the magnitude and rate bound non-linearities together, the induced ℓ∞ norm from disturbance input to the outputs involving control signal and its rate is utilised. On the other hand, discrete-time(DT) induced ℓ2 norm from disturbance input to the main controlled output is used to mitigate the effects of disturbances. We can tackle this ambitious non-linear control problem in the domain of linear convex multi-objective optimal control problem, which can be solved by effective semi-definite optimisation methods by using the proposed transformation and handling the control constraints in terms of worst case peak-to-peak gain of the system. Extended Linear Matrix Inequalities (LMIs) and full block S-procedure based design conditions developed over Linear Fractional Representation(LFR) framework allow the user to obtain robust state- and output-feedback control solutions with reduced conservatism. For the first time, this paper introduces an extended LMI based robust output-feedback control design for magnitude and rate bounded (MRB) systems, using full block S-procedure. We demonstrate the performance of the proposed controller through several simulations over benchmark examples covering systems having multi-variable structures and uncertainties. Our study also involves comparison results with a recently introduced technique based on multi-stage AW technique. The simulation results show that the proposed method of this paper is much effective and less conservative compared to the recent AW method provided in the literature.

Anti windup GPC speed controller for induction machine based on Youla parametrization

Abstract In the induction motor indirect vector control system, because of its physical limitations, the large step change in the speed command and/or load would eventually cause the so-called “integral windup phenomenon” which causes unexpected behavior of the system. To counteract this problem, an anti- windup generalized predictive speed control method is proposed by using the Youla parametrization. As first step, the design of an initial GPC controller based on its polynomial equivalent structure is required. Then, thanks to the Youla parametrization, this controller is retuned considering two specifications. The first is a frequency specification on the quadratic component of stator current response to the speed reference. And the second is a time domain constraint on the measured speed response to the speed reference. These constraints are formulated within a convex optimization framework. The simulation results proved the efficiency of the present design method.

Integrated Anti-Windup Fault-Tolerant Control Architecture for Optimized Satellite Attitude Stabilization

This article presents the development of an anti-windup (AW) compensator architecture for nanosatellite systems. The design addresses the problem of fault-tolerant control (FTC) for attitude stabilization subject to actuator saturation, actuator faults, and multiple disturbances. In many practical applications, certain physical limitations in the actuator design often mean that actuator saturation is mostly unaccounted for. Based on the ESTCube-2 nanosatellite model with reaction wheels (RWs), an integrated AW–FTC architecture is designed for an optimized attitude control system. The AW compensator is formulated using the linear matrix inequality (LMI) and computed to generate an augmented solution that is appended to the linear control system. The AW compensator in the architecture is designed with suitable parameters and effective controller gain values. The AW–FTC acts on the RW momentum as control input with the observed torque response, thereby ensuring an asymptotically stable system. Simulation results are presented to demonstrate the effectiveness of this approach with finite-time stabilization under actuator faults and saturation conditions.

Output Feedback T-S Fuzzy RMPC Applied to 3SSC Boost Converter

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.

Containment control of multi-agent systems with input saturation and unknown leader inputs

This paper investigates the containment control problem for multi-agent systems (MASs) with multiple leaders which have non-zero control inputs. Agents’ tracking errors are described by a linear system with an external disturbance. The containment control problem is then solved by applying a distributed observer-based output feedback controller. Anti-windup (AW) compensation is designed by convex conditions, to improve the performance in the presence of actuator saturation. Finally, simulations are presented to illustrate the effectiveness of the proposed method.

Fixed-Dynamics Antiwindup Design: Application to Pitch-Limited Position Control of Multirotor Unmanned Aerial Vehicles

In this brief, we present and validate an antiwindup (AW) control design suitable to deal with saturated discrete-time linear plants. Following the modern approach to AW design, the proposed synthesis procedure is based on the compensator paradigm in which the AW controller acts on top of a baseline one, tuned to achieve desirable performance in the unsaturated regime. After extending existing ideas for continuous-time plants to their discrete-time counterparts, the design of the AW compensator is carried out with a focus on computational efficiency and optimized performance in practical operating scenarios. The proposed approach allows one to design fixed-dynamics AW compensators for possibly open-loop unstable plants using generalized sector conditions. Then, the synthesis procedure is applied to tune a fixed-dynamics compensator having the structure of a static compensator cascaded with a unit delay to avoid algebraic loops. Finally, the benefits of such AW augmentation are assessed experimentally to counteract windup effects arising in the position control of multirotor unmanned aerial vehicles (UAVs) when pitch limitations are imposed.

Pitch autopilot design for an autonomous aerial vehicle in the presence of amplitude and rate saturation

In this article, a new composite anti-windup (AW) compensator scheme is proposed to tackle the rate and amplitude saturations in an autonomous aerial vehicle (AAV). The actuator input saturation is a practical and critical challenge in the controller design of autonomous vehicles. Nowadays, modern anti-windup compensators are presenting practical remedies to cope with input amplitude and rate saturation. Meanwhile, Riccati-based compensators can be a suitable choice due to their high performance and simplicity. Therefore, this article proposes an integrated approach by combining the anti-windup amplitude and rate methods to deal with the aforementioned problems. First, the basic controller function on the linear model is examined. It is shown that this controller behaves well so long as there is no saturation. However, when saturation occurs, its performance is decreased and even becomes unstable. By modifying the controller via the proposed method, the controller efficiency is increased significantly. The proposed method has been implemented on an autonomous aerial vehicle with 6-degrees of freedom (6DOF). Through various simulation scenarios, it is shown that the proposed method can show proper behavior in the case of a nonlinear and close-to-reality model of the system. In addition, the proposed controller efficacy has been investigated in a comprehensive Monte Carlo simulation and it is shown that the proposed method keeps its efficiency against the practical uncertainties of the system behavior.

Anti-Windup FOPID-Based DPC for SAPF Interconnected to a PV System Tuned Using PSO Algorithm

This paper deals with a shunt active power filter (SAPF) integrated in a photovoltaic (PV) system, which is interfaced to the grid via a double-stage configuration, for simultaneously improving the power quality in the existence of non-linear loads and injecting the PV harvested power to the power grid. The direct power control (DPC) based on the conventional Proportional-integral (PI) suffers from some shortcomings in the transient state, such as large overshoots and undershoots in the voltage. Long response time is another disadvantage when using such a controller. To overcome this situation, the proposed control method is equipped by an anti windup fractional order proportional-integral differentiator (AW-FOPID) regulator, replacing the standard PI or PID regulators to maintain the DC link voltage at its desired value with small overshoots and undershoots in the voltage, while maintaining a short response time. The AW-FOPID controller, however, has five parameters, which makes it troublesome to tune. Accordingly, to adjust this AW-FOPID parameters, the Particle Swarm Optimization (PSO) algorithm is employed by minimizing the Integral Time Absolute Error (ITAE). Furthermore, an intelligent algorithm for tracking the maximum power point (MPPT) based on fuzzy logic has been applied to eventually resolve the drawback of the rapidly changing weather conditions. The overall control scheme is examined by simulation using MATLAB/Simulink software. The obtained simulation results and comparative study demonstrate the feasibility and performance of this control strategy.

Finite Time Convergence Incremental Nonlinear Dynamic Inversion-Based Attitude Control for Flying—Wing Aircraft with Actuator Faults

In this paper, a two-loop fault-tolerant attitude control scheme is proposed for flying-wing aircraft with actuator faults. A regular nonlinear dynamic inversion (NDI) control is used in the outer attitude loop, and a finite time convergence incremental nonlinear dynamic inversion (FINDI) control combined with control allocation strategy is used in the inner angular rate loop. Prescribed performance bound (PPB) is designed to constrain the tracking errors within a residual set, so the prescribed system performance can be guaranteed. An optimal anti-windup (AW) compensator is introduced to solve the actuator saturation problem. Simulation results demonstrate the effectiveness of the proposed approach.

Aplikasi Kontroler PI Modifikasi pada Prototype Alat Pasteurisasi Menggunakan Simple Water Heater

Kontroler PI adalah suatu algoritma kontroler yang banyak digunakan di industri karena kemudahannya untuk diaplikasikan dan dismulasikan. Dalam penelitian ini, kontroler PI digunakan untuk mengatur suhu pada Prototype Alat Pasteurisasi yang dirancang menggunakan Simple Water Heater. Pasteurisasi adalah sebuah proses pemanasan makanan dengan tujuan membunuh organisme yang merugikan. Keberhasilan Pasteurisasi sangat dipengaruhi oleh suhu pemanasan. Namun pada sistem ini, terdapat sebuah komponen yang mempunyai keterbatasan kinerja output. Komponen tersebut adalah Converter AC to AC. Converter AC to AC digunakan untuk mengatur tegangan AC yang dibutuhkan untuk mengontrol suhu pada plan pasteurisasi. Karena keterbatasan itu, sebuah modifikasi diperlukan. Modifikasi tersebut adalah Anti WindUp. Sehingga Kontroler PI mampu bekerja dengan baik dalam mencapai set poin dengan error steady state sekitar 1%, lebih tahan terhadap gangguan dari luar dan mampu menghasilkan susu yang aman untuk dikonsumsi.

The Anti Windup PID Controller ISE Tuning Based for Small-Scale Steam Distillation System

The Anti Windup PID Controller ISE Tuning Based for Small-Scale Steam Distillation System

A novel approach for static anti-windup compensation of one-sided Lipschitz systems under input saturation

This paper illustrates a new strategy for designing the local static anti-windup (AW) compensator for nonlinear systems with one-sided Lipschitz (OSL) nonlinearities under saturating actuators and exogenous disturbances. The static AW strategy is designed such that the resulting closed-loop system with OSL nonlinearity, actuator saturation, and exogenous disturbance is stable and the region of attraction can be maximized. Inequalities based conditions are formulated for the static AW gain design by using Lyapunov stability theory, sector condition, L2 gain reduction, OSL inequality, and quadratic inner-bounded (QIB) condition. The proposed AW technique is simpler to design, straightforward to implement and deals with a broader class of systems in contrast to conventional methods. An application example demonstrates that the proposed static AW can successfully mitigate the saturation consequences in OSL nonlinear systems.

Implementation of Fuzzy PID Controller in Cascade with Anti-Windup to Real-Scale Test Equipment for Pavements

In the industry and academia, large-scale equipment has been developed, which requires control systems that provide safety and efficiency with the lowest possible energy consumption. In the industrial cascade control system, nested controllers have been a versatile tool for the control of large-scale equipment. Research shows that these types of controllers improve their performance with the integration of artificial intelligence algorithms and prevention methods against controller saturation. For this reason, this paper presents the development of a fuzzy proportional-integral-derivative (PID) controller in cascade with anti-windup (AW) for full-scale test equipment for pavements. In this study, the mathematical expressions for the equipment, the design of the controller and additional systems for comparison, simulation and analysis are developed. The main objective is to test the functionality of this type of nested controllers for these systems.

A Class of Proportional-Integral With Anti-Windup Controllers for DC–DC Buck Power Converters With Saturating Input

In dc–dc buck power converters, a control action which is negative or greater than one has no physical meaning and is noncausal. For the sake of realism, the nonlinearity accompanying input saturation is taken into account in a model of dc–dc buck power converters, for which a Lyapunov function-based class of proportional-integral with anti-windup (PIAW) algorithms is given. Simple tuning guidelines ensure the global asymptotical stability of the closed-loop system. Neither the class of controllers nor the tuning procedure require the exact knowledge of the parameters of the power converter. To illustrate the results, a novel design matching the proposed class of controllers is given and the results of real-time experimental tests are presented, including the implementation of the linear proportional-integral (PI) control and a known anti-windup (AW) approach. The results confirm that the proposed PIAW control has the best performance even though saturation limits are activated and disturbances are present.