Palanisamy Selvaraj

Robust fault-tolerant H∞ control for offshore steel jacket platforms via sampled-data approach

Abstract This paper addresses the issue of robust fault-tolerant sampled-data H ∞ control for a class of uncertain offshore steel jacket platform systems with input random time-varying delays and linear fractional uncertainties. A new Lyapunov–Krasovskii functional (LKF) is constructed to obtain sufficient conditions under which the uncertain offshore platform system is robustly asymptotically stable with a disturbance attenuation level γ > 0 . Moreover, Jenson׳s integral inequality and zero valued free weighting matrix are utilized to simplify the derivation of the main results. Linear matrix inequality (LMI) based sufficient conditions are derived to guarantee the robust performance of the considered offshore steel jacket platform with a disturbance attenuation index. The proposed results can be used to attenuate the external disturbances to make ensure the safety and comfort level of the offshore structure. Finally, the results are verified with simulation results to show the effectiveness of the proposed control scheme.

Adaptive reliable output tracking of networked control systems against actuator faults

Abstract This paper investigates the reliable adaptive observer-based output tracking control problem for a class of networked control systems subject to actuator faults and external disturbances via equivalent-input disturbance technique. Notably, the reliable control design based on adaptive mechanism is implemented to compensate the on-line actuator faults automatically and an observer-based controller is introduced through communication networks to drive the output of controlled plant to track the output of a reference model. Moreover, due to the effect of network-induced delays and packet dropouts in the controller-to-actuator channel, the inputs of controlled plant and observer-based tracking controller are updated in an asynchronous way. Then, based on the asynchronous characteristic, the resulting closed-loop networked control system is formulated with two interval time-varying delays for obtaining the required result. In particular, the equivalent-input disturbance approach improves the disturbance rejection performance and it does not require any prior knowledge of the disturbances. By constructing a suitable Lyapunov–Krasovskii functional and using free-weighting matrix approach, a new set of sufficient conditions for the solvability of the addressed problem is derived in terms of linear matrix inequalities. At last, the proposed result is validated through two numerical examples and also a comparison study is presented which shows the effectiveness of the developed control scheme over some existing conventional control schemes.

Vibration control of structural systems via robust non-fragile sampled-data control scheme

Abstract This paper investigates the dissipative non-fragile output feedback sampled-data control problem for uncertain structural systems. In the proposed system, uncertainties are assumed to be time-varying and bounded, which are considered in the linear fractional transformation form. The main objective of this paper is to design a non-fragile sampled-data controller such that the resulting closed-loop system is strictly ( Q , S , R ) - α -dissipative. On the basis of a suitable Lyapunov–Krasovskii functional and linear matrix inequality technique, a new set of sufficient conditions is established to achieve the required result for both nominal and uncertain systems. In particular, an output feedback dissipative sampled-data controller is designed by solving a set of matrix inequalities. More precisely, Schur complement lemma, free weighting matrix approach and Wirtinger-based double integral inequality are utilized to substantially simplify the derivation of the main results. Finally, simulations based on structural systems are conducted to illustrate the effectiveness of the proposed control scheme.

A Robust Repetitive-Control Design for a Class of Uncertain Stochastic Dynamical Systems

In this brief, we study the problem of output tracking for continuous-time stochastic dynamical systems with parametric uncertainties and aperiodic disturbances by using a modified repetitive controller (MRC). More precisely, the MRC is obtained based on the equivalent input disturbance (EID) technique such that the closed-loop modified repetitive-control system is asymptotically stable in the presence of uncertainties and aperiodic disturbances. The main advantage of the proposed controller is that it can incorporate an EID estimator, which estimates and eliminates disturbances in the repetitive-control systems. Finally, simulation is conducted to reveal that the proposed controller can effectively reject the aperiodic disturbance, reduce the stochastic noise, and track the reference signal without steady-state error.

Dissipative sampled‐data control of uncertain nonlinear systems with time‐varying delays

This article investigates the delay-dependent robust dissipative sampled-data control problem for a class of uncertain nonlinear systems with both differentiable and non-differentiable time-varying delays. The main purpose of this article is to design a retarded robust control law such that the resulting closed-loop system is strictly (Q, S, R)-dissipative. By introducing a suitable Lyapunov–Krasovskii functional and using free weighting matrix approach, some sufficient conditions for the solvability of the addressed problem are derived in terms of linear matrix inequalities. From the obtained dissipative result, we deduce four cases namely, H∞ performance, passivity performance, mixed H∞, and passivity performance and sector bounded performance of the considered system. From the obtained result, it is concluded that based on the passivity performance it is possible to obtain the controller with less control effort, and also the minimum H∞ performance and the maximum allowable delay for achieving stabilization conditions can be obtained via the mixed H∞ and passivity control law. Finally, simulation studies based on aircraft control system are performed to verify the effectiveness of the proposed strategy.

Observer-based state tracking control of uncertain stochastic systems via repetitive controller

ABSTRACT This paper develops the repetitive control scheme for state tracking control of uncertain stochastic time-varying delay systems via equivalent-input-disturbance approach. The main purpose of this work is to design a repetitive controller to guarantee the tracking performance under the effects of unknown disturbances with bounded frequency and parameter variations. Specifically, a new set of linear matrix inequality (LMI)-based conditions is derived based on the suitable Lyapunov–Krasovskii functional theory for designing a repetitive controller which guarantees stability and desired tracking performance. More precisely, an equivalent-input-disturbance estimator is incorporated into the control design to reduce the effect of the external disturbances. Simulation results are provided to demonstrate the desired control system stability and their tracking performance. A practical stream water quality preserving system is also provided to show the effectiveness and advantage of the proposed approach.

Robust reliable dissipative control of nonlinear networked control systems

This article focuses on the robust reliable dissipative control issue for a class of switched discrete-time nonlinear networked control systems with external energy bounded disturbances. In particular, nonlinearities are modeled in a probabilistic way according to Bernoulli distributed white sequence with known conditional probability. A Lyapunov–Krasovskii functional is proposed based on which sufficient conditions for the existence of the reliable dissipative controller are derived in terms of linear matrix inequalities (LMIs) which ensures exponentially stability as well as (Q,S,R) dissipative performance of the resulting closed-loop system. The explicit expression of the desired controller gains can be obtained by solving the established LMIs. Finally, a numerical example is presented to demonstrate the effectiveness and applicability of the proposed design strategy.

Maintenance management system for a defence aircraft development programme

Design and development of a defence aircraft involves solving of multi disciplinary problems over the development lifecycle. The ground and flight tests evaluation play a crucial role during the certification of the aircraft. The observations from the field trials viz. reported failures and corrective actions taken are of immense value for the performance assessment of aircraft. In addition to the aircraft performance assessment and root cause analysis of the failures, the data from the field also facilitates to assess and refine the maintenance procedures. This paper brings out a conceptual model of computerised aircraft maintenance management system (CAMMS), which is a product lifecycle management (PLM) enabled enterprise–wide solution involving designers, maintenance planners, test pilots, flight test engineers, inspectors and certification agency. This supposed system will encapsulate a framework for failure reporting analysis and corrective action that shall assist in failure, reliability and maintainability analysis, aiding a tighter control on the schedule and budgetary escalation.

Seismic Qualification of the Unconventional Valve by Shake Table Testing

To make Nuclear Power Plants (NPP) more acceptable by the public, there is a need to conform to the stringent safety criteria evolved continuously. Among the several safety aspects, the seismically induced effects call more attention at the present scenario. But the adequate full scale testing of the critical components can render a more realistic simulation. Extensively shake table testing is used for the seismic qualification and research purposes. It provides the means to excite structures in such a way that they are subjected to conditions representative of true earthquake ground motions. The seismic qualification tests were conducted as per the test procedure given in IEEE STD 344-1987 standards: IEEE recommended practice for seismic qualification of class 1E equipment for Nuclear Power Generating Station. Valves are one of the active components in the SFR system. The seismic operability of active components can be established only by shake table testing. Shake table testing includes fixing of the equipment into the shake table, exiting the table with a seismic excitation equal to or larger than the design earthquake, resonance search test in all the three directions for 1 to 50 Hz to identify the system frequencies and assessment of the functionality and structural integrity of the valve during and at the end of the test. The valve that has been experimentally qualified completed type test for OBE & SSE cycles, the same will not be utilized in the reactor application. The methodology involved in the seismic qualification of the unconventional valve presented in this paper. Among the various shake table experiments carried out for the seismic qualification unconventional valves, the experiment carried out for the Inclined Fuel Transfer Machine (IFTM) Gate valve is referred in this paper for the above purpose. It is one of the unconventional type large in size and heavy gate valve available in the SFR system

State Estimation and Dissipative-Based Control Design for Vehicle Lateral Dynamics With Probabilistic Faults

In this paper, the state estimation problem is studied for vehicle lateral dynamics, which are approximated by the Takagi–Sugeno (T–S) fuzzy model with probabilistic actuator faults. First, a fuzzy rule-based state estimator is constructed to estimate the exact state values of the considered system, and then a probability-dependent fault-tolerant state feedback controller is developed based on the estimated state values. Furthermore, by constructing an appropriate Lyapunov–Krasovskii functional, some novel delay-dependent sufficient conditions that ensure the mean-square asymptotic stability and strict