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1

An active fault-tolerant control framework against actuator stuck failures under input saturations

Qi X., Theilliol D., He Y., Han J.

International Journal of Applied Mathematics and Computer Science

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2017

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Vol. 27, no. 4

749--761

EN

In this paper, a control framework including active fault-tolerant control (FTC) and reference redesign is developed subject to actuator stuck failures under input saturations. FTC synthesis and reference redesign approaches are proposed to guarantee post-fault system safety and reference reachability. Then, these features are analyzed under both actuator stuck failures and constraints before fault-tolerant controller switches. As the main contribution, actuator stuck failures and constraints are unified so that they can be easily considered simultaneously. By means of transforming stuck failures into actuator constraints, the post-fault system can be regarded as an equivalent system with only asymmetrical actuator constraints. Thus, methods against actuator saturations can be used to guarantee regional stability and produce the stability region. Based on this region, stuck compensation is analyzed. Specifically, an unstable open-loop system is considered, which is more challenging. Furthermore, the method is extended to a set-point tracking problem where the reachability of the original reference can be evaluated. Then, a new optimal reference will be computed for the post-fault system if the original one is unreachable. Finally, simulation examples are shown to illustrate the theoretical results.

2

Robust output regulation of uncertain chaotic systems with input magnitude and rate constraints

Velosa C. M. N., Bousson K.

Acta Mechanica et Automatica

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2015

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Vol. 9, no. 4

252--258

EN

The problem of output regulation deserves a special attention particularly when it comes to the regulation of nonlinear systems. It is well-known that the problem is not always solvable even for linear systems and the fact that some demanding applications require not only magnitude but also rate actuator constraints makes the problem even more challenging. In addition, real physical systems might have parameters whose values can be known only with a specified accuracy and these uncertainties must also be considered to ensure robustness and on the other hand because they can be crucial for the type of behaviour exhibited by the system as it happens with the celebrated chaotic systems. The present paper proposes a robust control method for output regulation of chaotic systems with parameter uncertainties and subjected to magnitude and rate actuator constraints. The method is an extension of a work recently addressed by the same authors and consists in decomposing the nonlinear system into a stabilizable linear part plus a nonlinear part and in finding a control law based on the small-gain principle. Numerical simulations are performed to validate the effectiveness and robustness of the method using an aeronautical application. The output regulation is successfully achieved without exceeding the input constraints and stability is assured when the parameters are within the specified intervals. Furthermore, the proposed method does not require much computational effort because all the control parameters are computed offline.

3

Dynamic Modification of Reference Value for Reduction of Negative Effects of Actuator Constraints in Single-loop PID Control Systems

Janiszowski K.

Pomiary Automatyka Kontrola

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2009

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R. 55, nr 3

170-173

EN

A modification of the PID digital controller algorithm, based on the introduction of a virtual reference value that never exceed active constraints in the actuator output is presented and investigated. This idea derived from virtual modification of a control error can be used in digital control systems subjected by both: magnitude and rate constraints. The adaptation (to the actuator constraints) is performed by a special transformation of the control error, and is equivalent to introduction of a new, virtual reference value for the control system. Simulation results for dynamic, linear SISO systems are presented for comparison of the proposed approach with used techniques.

PL

W pracy zostala przedstawiona modyfikacja działania cyfrowego algorytmu PID, oparta na wprowadzeniu dynamicznie zmiennej wartości zadanej, która nie prowadzi do przekroczenia ograniczeń możliwości elementu wykonawczego. Metoda jest oparta na dynamicznej modyfikacji odchyłki regulacji i może być stosowana w układach regulacji o ograniczeniach amplitudy i prędkości zmian zespołu wykonawczego. Adaptacja układu (do ograniczeń aktuatora) jest równoważna dynamicznej modyfikacji wartości zadanej. Wyniki badań symulacyjnych, porównujące efekty działania metody z innymi modyfikacjami stosowanymi dla algorytmu PID są zaprezentowane dla dwóch liniowych układów dynamicznych.

4

Control error dynamic modification as an efficient tool for reduction of effects introduced by actuator constraints

Janiszowski K. B.

International Journal of Applied Mathematics and Computer Science

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2009

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Vol. 19, no 2

271-279

EN

A modification of digital controller algorithms, based on the introduction of a virtual reference value, which never exceeds active constraints in the actuator output is presented and investigated for some algorithms used in single-loop control systems. This idea, derived from virtual modification of a control error, can be used in digital control systems subjected to both magnitude and rate constraints. The modification is introduced in the form of on-line adaptation to the control task. Hence the design of optimal (in a specified sense) digital controller parameters can be separated from actuator constraints. The adaptation of the control algorithm (to actuator constraints) is performed by the transformation of the control error and is equivalent to the introduction of a new, virtual reference value for the control system. An application of this approach is presented through examples of three digital control algorithms: the PID algorithm, the dead-beat controller and the state space controller. In all cases, clear advantages of transients are observed, which yields some general conclusions to the problem of processing actuator constraints in control.