Anti-windup Synthesis Research Articles

Switching Anti-Windup Synthesis for Linear Systems With Asymmetric Actuator Saturation.

This article proposes a switching anti-windup strategy for linear, time-invariant (LTI) systems subject to asymmetric actuator saturation and L2 -disturbances, the core idea behind which is to make full use of the available range of control input space by switching among multiple anti-windup gains. The asymmetrically saturated LTI system is converted to a switched system with symmetrically saturated subsystems, and a dwell time switching rule is presented to govern the switching between different antiwindup gains. Based on multiple Lyapunov functions, we derive sufficient conditions for guaranteeing the regional stability and weighted L2 performance of the closed-loop system. The switching anti-windup synthesis that designs a separate anti-windup gain for each subsystem is cast as a convex optimization problem. In comparison with the design of a single anti-windup gain, our method can induce less conservative results since the asymmetric character of the saturation constraint is fully utilized in the switching anti-windup design. Two numerical examples, and an application to aeroengine control (the experiments are conducted on a semiphysical test bench), demonstrate the superiority and practicality of the proposed scheme.

Switching Anti-windup Synthesis for Linear Systems Subject to Asymmetric Input Magnitude and Rate Saturation: Application to Aircraft Engines

Switching Anti-windup Synthesis for Linear Systems Subject to Asymmetric Input Magnitude and Rate Saturation: Application to Aircraft Engines

Enhancement of the Commandable Areas of a Modular DC–DC Converter With Anti-Windup Synthesis in Fuel Cell Systems

Enhancement of the Commandable Areas of a Modular DC–DC Converter With Anti-Windup Synthesis in Fuel Cell Systems

Event-triggered anti-windup strategy for time-delay systems subject to saturating actuators

<p>This paper investigates the anti-windup synthesis problem for linear control systems subject to time-varying state delay and saturating actuators. To alleviate the redundant data transmission, the dynamic event-triggered mechanism is adopted. Moreover, to abate the inherent conservatism, novel delay-dependent sector conditions containing double integral terms are explored. Then, using augmented Lyapunov-Krasovskii functionals and several less conservative inequalities, delay-dependent anti-windup synthesis criteria are obtained in accordance with the feasibility of linear matrix inequalities. Subsequently, the optimization of the initial condition set is addressed. Finally, a simulation example illustrates the availability and technique advantages of the proposed results.</p>

A Generalized Anti-windup Approach for Internal Model Control

In this paper, we develop a generalized anti-windup synthesis procedure for saturating internal model control (IMC). Within this framework, the anti-windup design problem reduces to a search over a class of left coprime factorization of the linear internal model controller. An appropriate anti-windup is constructed by solving a set of linear matrix inequalities. As compared to other static anti-windup constructions in the literature, the IMC anti-windup is always feasible with guaranteed closed-loop stability and performance. Using a simulation example, we benchmark the behaviour of the constructed anti-windup with existing state-of-the-art methods.

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.

Anti-Windup Synthesis for Linear Systems With Asymmetric Input Saturation: Application to Aircraft Engine Control

This brief proposes a novel anti-windup scheme for linear systems subject to asymmetric input saturation. The asymmetrically saturated system is converted into an equivalent one with symmetric saturation through coordinate transformation. Based on the transformed model, we establish the set invariance condition of the resulting closed-loop system. This condition is less conservative since the non-symmetric nature of the saturation nonlinearity can be fully exploited in the control design. An optimization algorithm to maximize the invariant set is further developed for anti-windup gain design. The theoretical aspect of this method is analyzed rigorously, and the effectiveness is verified through an application to the aircraft engine control with experiments performed on a semi-physical test bed.

Dynamics modeling and motion control for high-speed underwater vehicles using H-infinity synthesis with anti-windup compensator

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.

Data-driven anti-windup compensator synthesis for unknown linear systems with time delay

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.

Delayed anti-windup strategy for input-delay systems with actuator saturations

In this paper, the time-delayed anti-windup problem is addressed for linear input-delay systems with actuator saturations. By using an augmented Lyapunov-Krasovskii functional, the generalized sector condition and some advanced inequalities, anti-windup synthesis conditions are first established by means of linear matrix inequalities. In particular, the first time-interval is considered in determining the performances of closed-loop systems under a relatively practical control setting. Then, several optimization problems are proposed to solve the optimal performance indices. Finally, a simulation example is given to illustrate the effectiveness of the proposed anti-windup strategy.

Anti-windup design for directionality compensation with application to quadrotor UAVs

In this letter we propose an anti-windup strategy to counteract directionality effects arising in saturated MIMO systems in which independent dynamical subsystems are coupled through a static mixing of the inputs. Since such systems are affected by undesired input cross-couplings when saturation occurs, we propose an anti-windup augmentation scheme built on top of the baseline controller and tailored to achieve satisfactory time-domain performance for reference signals of interest. Motivated by the quadrotor application, in which position control has higher priority over yaw control for safety reasons, we embed in the anti-windup synthesis procedure the possibility to prioritize the level of performance degradation during saturation for the different system outputs.

A practical solution for the control of time-delayed and delay-free systems with saturating actuators

This paper presents a predictor based structure that is suitable to deal with both time-delayed and delay-free systems with saturating actuators. Such condition, well known in the literature to cause the windup phenomenon, is usually coped within the control area by techniques that commonly lead to the controller augmentation. However, it seems to exist a lack of simple approaches to deal with the design of linear controllers for both systems with and without delay. Thus, this paper addresses the saturation problem by both proposing a linear controller design and an associated anti-windup compensator design. The controller tuning is realized in three distinct phases, initially considering set-point tracking adjustment, then robustness and disturbance rejection tuning, and finally the associated anti-windup compensator synthesis. Furthermore, linear matrix inequalities (LMIs) which include both performance and stability requirements are employed for the anti-windup synthesis. The proposed controller presents better results when compared with recently published anti-windup controllers as well as a constrained MPC algorithm. Experimental results on a neonatal intensive care unit are also presented in order to validate the usefulness of the proposed strategy.

Discrete-time anti-windup compensation for synchrotron electron beam controllers with rate constrained actuators

By accelerating electrons to relativistic speeds, synchrotrons generate extremely intense and narrow beams of electromagnetic light that are used for academic research and commercial development across a range of scientific disciplines. In order to achieve optimum performance, the stability of the electron beam is a crucial parameter for synchrotrons and is achieved by a beam stabilisation system that is used to control the location of the electron beam and minimise any instability of the electron beam caused by external disturbances. Slew rate limits are common nonlinearities encountered with the actuators in synchrotron feedback systems which can impose significant limitations on the robustness and the performance of the control system. This paper describes an Internal Model Control (IMC) based anti-windup synthesis using an algebraic Riccati equation for a discrete-time control system to compensate against the performance deterioration in the presence of rate constraints. An Integral Quadratic Constraint (IQC) framework is used to analyse the robust stability of the anti-windup augmented closed loop system in the presence of norm-bounded uncertainty. The anti-windup augmented controller is implemented at Diamond Light Source, the UK’s national synchrotron facility and improvements in robustness and performance were achieved with respect to the use of no anti-windup compensation.

Directionality compensation for linear multivariable anti-windup synthesis

We develop new synthesis procedures for optimising anti-windup control applicable to open-loop exponentially stable multivariable plants subject to hard bounds on the inputs. The optimising anti-windup control falls into a class of compensator commonly termed directionality compensation. The computation of the control involves the online solution of a low-order quadratic programme in place of simple saturation. We exploit the structure of the quadratic programme to incorporate directionality information into the offline anti-windup synthesis using a decoupled architecture similar to that proposed in the literature for anti-windup schemes with simple saturation. We demonstrate the effectiveness of the design compared to several schemes using a simulated example.

Delay Dependent Anti-windup Synthesis for Time-varying Delay Systems with Saturating Actuators

The synthesis of an anti-windup compensator for systems with time-varying delays is solved in this paper. More precisely, LMI conditions are proposed that guarantee the stability of the closedloop system, with a enlarged domain of attraction. An ellipsoid and a polyhedral set are used to bound this domain of attraction, making possible to derive a new sector condition. In addition, an algorithm is provided to optimize the anti-windup gain, reducing the conservatism. Numerical examples illustrate the effectiveness of our methodology, which improves previous works.

Simultaneous anti-windup synthesis for linear systems subject to actuator saturation

Simultaneous anti-windup synthesis for linear systems subject to actuator saturation

Simultaneous multi-stage anti-windup synthesis for open-loop stable plants

In this paper, we present a synthesis method for global stability and performance of input constrained linear plants. We consider the multi-stage anti-windup scheme that uses two sets of static anti-windup gains. Unlike traditional two-step anti-windup design procedures, our method synthesizes all controller parameters simultaneously. This simultaneous design also provides an opportunity to guarantee different levels of performance based on the magnitude of the controller output. The synthesis results are cast as an optimization over linear matrix inequalities. The benefits of the proposed method are illustrated with a well-known example.

Optimal anti-windup synthesis for repetitive controllers

Repetitive controllers use internal models that provide very high gain at a selected fundamental frequency and its harmonics, additionally, some of the internal models may result unstable, as in the high order repetitive control approach. These characteristics make the repetitive control system susceptible to exhibit wind-up when actuator saturation occurs. This paper proposes an anti-windup scheme for repetitive control based on the model recovery anti-windup strategy. The proposed scheme provides low order, low computational burden and also isolation of the controller from the saturation effects. The anti-windup compensator is constructed from the plant model and provides an additional linear feedback path aimed at enhancing system performance. This feedback path is designed to obtain a deadbeat behaviour, which makes the system recovery faster. Finally, internal stability and deadbeat features are designed in a compact procedure based on linear matrix inequalities and an optimal linear quadratic design. Experimental validation of the proposed anti-windup compensator is provided using a mechatronic plant.

Anti-windup design with guaranteed stability regions for resonant and repetitive controllers.

This paper addresses the anti-windup synthesis for control loops presenting resonant or repetitive controllers. A linear conditioning anti-windup approach is considered. Provided that the exogenous signals or the initial condition are such that the distance between the control signal provided by the controller and the set of admissible constrained controls is limited in energy, i.e dist(ulin, ) ε L2, the computed anti-windup compensator minimizes the deviation of the actual system output from the ideal output that would be achieved in the absence of saturation. The main theoretical contribution of the paper is therefore the proposition of a systematic method to determine admissible sets of exogenous signals and initial conditions for which the condition dist(ulin, u) ε L2 holds when resonant or repetitive controllers are used.

Convex Synthesis of Multivariable Static Discrete-time Anti-windup via the Jury-Lee Criterion

Due to its ease of application, the circle criterion has been widely used to guarantee the stability of many anti-windup schemes. While the Popov criterion gives less conservative results, it has been conjectured in the literature that it cannot be used for convex anti-windup synthesis. This paper shows that the conjecture does not necessarily apply in the discrete-time setting. We show how the search for optimal parameters corresponding to the Jury-Lee criterion (a discrete counterpart of the Popov criterion) can be formulated as a convex search via a linear matrix inequality (LMI). The result is then extended to two existing multivariable static anti-windup schemes with stable open-loop plants. Two numerical examples of multivariable anti-windup controller synthesis are provided, and it is shown that in both cases the synthesis using the Jury-Lee criterion can allow better performance than existing methods which use the circle criterion alone.