SUMMARYThis paper studies the design problem of robust delay-dependent H ∞ controller for a class of timedelay control systems with time-varying state and input delays, which are assumed to be noncoincident. The system is subject to norm-bounded uncertainties and L 2 disturbances. Based on the selection of an augmented form of Lyapunov-Krasovskii (L-K) functional, first a Bounded Real Lemma (BRL) is obtained in terms of linear matrix inequalities (LMIs) such that the nominal, unforced time-delay system is guaranteed to be globally asymptotically stable with minimum allowable disturbance attenuation level. Extending BRL, sufficient delay-dependent criteria are developed for a stabilizing H ∞ controller synthesis involving a matrix inequality for which a nonlinear optimization algorithm with LMIs is proposed to get feasible solution to the problem. Moreover, for the case of existence of norm-bounded uncertainties, both the BRL and H ∞ stabilization criteria are easily extended by employing a well-known bounding technique. A plenty of numerical examples are given to illustrate the application of the proposed methodology of this note. The achieved numerical results on the maximum allowable delay bound and minimum allowable disturbance attenuation level are exhibited to be less conservative in comparison to those of existing methods in the literature.

There always exists a conflict between ride comfort and suspension deflection performances during the vibration control of suspension systems. Active suspension control systems, which are designed by linear methods, can only serve as a trade-off between these conflicting performance criteria. Both performance objectives can only be accomplished at the same time by using a nonlinear controller. This paper addresses the non-linear induced L2 control of an active suspension system, which contains non-linear spring and damper elements. The design method is based on the linear parameter varying (LPV) model of the system. The proposed method utilizes the bilinear damping characteristic, stiffening spring characteristic when the suspension deflection approaches the structural limits, mass variations and parameter-dependent weighting filters. Simulation studies both in time and frequency domain demonstrate that the active suspension system controlled by the proposed method always guarantees an agreement between acceleration (comfort) and suspension deflection magnitudes together with a high ride performance.

This article addresses the design of a gain-scheduling type nonlinear controller for a full-vehicle active suspension system. The proposed method is based on a Linear Parameter Varying (LPV) model of the system. In this model, the variations in suspension deflection and mass are chosen as the scheduling parameters. During the simulations, the full-vehicle system that is controlled by the proposed method is tested with different road profiles, having high and low bumps, hollows and combinations of the two. The simulation results demonstrate that the proposed method successfully maximizes the ride comfort when suspension deflection is far away from the structural limits and minimizes the suspension deflection by changing its behavior when the suspension limits are reached.

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Parameters identification of isolated wind-diesel power systems (WDPS) is a significant issue in stability analysis of the power system as well as guaranteeing the power generation through the control system. In this paper, enhanced whale optimization algorithms (EWOA) are proposed to deal with the parameter identification problem of a WDPS system. The proposed EWOA effectively tackles the premature convergence problem of WOA by splitting the population into two subpopulations and updating the position of each whale according to the position of the best agent in its current subpopulation, the position of the other subpopulation's best agent, and the position of the best neighboring agent. Furthermore, fractional chaotic maps are embedded in the search process of EWOA to increase its performance in terms of accuracy. For validation purposes, the proposed algorithms are applied to identify the unknown parameters of WDPS, where different statistical analyzes and comparisons are carried out with other recent state-of-the-art algorithms. Simulation results confirm that the algorithms have less deviation in parameter estimation, more convergence speed, and higher precision in comparison with other algorithms. INDEX TERMS Optimization, parameter identification, whale optimization algorithm, wind-diesel power system.

In this study, the design problem of a Model Predictive Controller (MPC) for attenuation of vertical motions of a passenger ship which is subject to irregular wave excitations is investigated. The proposed design considers actuator amplitude and rate saturation phenomenon. The motion control system of the ship utilises a pair of active stabilizing fins mounted to the head and tail. First, irregular long crested head waves are implemented by a well-established randomization theory in order to find heave force and pitch moment at F n = 0.40 and F n = 0.50 in the time domain. Then, a two-degree-of-freedom mathematical model, in which pitch and heave motions are coupled with the approximation of convolution integrals is solved to obtain the uncontrolled motions and accelerations of the ship. Finally, considering the physical amplitude and rate limitations of the active fin mechanism, an MPC design is proposed to obtain a practically applicable state-feedback control law for attenuating vertical motion of a passenger ship. The performance of the MPC is also compared with an elipsoid based H ∞ controller. An extensive amount of simulation studies are presented at the end to illustrate the effectiveness of the proposed approach.

SUMMARYThis paper addresses the design problem of L 2 , gain-scheduling non-linear state-feedback controller for linear parameter varying (LPV) systems, subjected to actuator saturations and bounded energy disturbances, by using parameter-dependent type Lyapunov functions. The paper provides a systematic procedure to generate a sequence of linear matrix inequality (LMI) type conditions of increasing precision for obtaining a suboptimal L 2 state-feedback controller. The presented method utilizes the modified sector condition for formalization of actuator saturation and homogeneous polynomial parameter-dependent representation of LPV systems. Both simulations and experimental studies on an inverted pendulum on a cart system illustrate the benefits of the approach.