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This paper is concerned with the problem of adaptive tracking control for a class of nonlinear systems with parametric uncertainty, bounded external disturbance, and actuator saturation. In order to achieve robust output tracking for the saturated uncertain nonlinear systems, a combination of adaptive robust control (ARC) and a novel terminal sliding-mode-based nonlinear disturbance observer (TSDO) is proposed, where the modeling inaccuracy and disturbance are integrated as a lumped disturbance. Specifically, the observer errors of estimating the lump disturbances converge to zero in finite-time for improving the precision of estimation. The estimated disturbances are then used in the controller to compensate for the system's lumped disturbances. The analytical results show that the proposed scheme is stable and can guarantee the asymptotic tracking with the tracking error converging to zero even in the presence of disturbances. Finally, the developed method is illustrated the effectiveness by the application to control of a quarter-car model with active suspension system. Note to Practitioners-Tracking problem is a popular topic in the field of control, which plays an important role in actual application.Especially this issue on nonlinear system, which dynamic behaviors are complex and nonlinear characteristic property and the mathematical models are often difficult to accurate obtain. Another challenging issue in nonlinear control is the effects from uncertainties and external disturbances. Usually, building a dynamical system called an "disturbance observer" to estimate the modeling inaccuracy and disturbance is more applicable since uncertainties and disturbance cannot be measured through sensors. In addition, it is noted that saturation nonlinearity occurs in many practical actuators. How to design the controller in presence of saturation has become one main focus of control researches. Motivated by these issues, in this paper, ARC with TSDO algorithms are proposed for a class of uncertainty nonlinear systems to avoid employing large feedback gains in practical implementations.

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Vehicle suspension systems are important for significantly improving passenger comfort and handling characteristics. A well-designed suspension system can promote the whole performances of automobile chassis. In this paper, an adaptive vibration control strategy is proposed for the nonlinear uncertain suspension systems to stabilize both the vertical and pitch motions of the car, and thus to contribute to the ride comfort. Simultaneously, the ride holding performances are preserved within their allowable limits in the controller design. Moreover, differing from the existing results, in most of which the effect of actuator dynamic is neglected, this paper considers the electrohydraulic systems as actuators to supply the active forces into suspension systems. Furthermore, to overcome the "exploration of terms" problem existing in standard backstepping, a filterbased adaptive control strategy is subsequently proposed. Finally, a design example is shown to illustrate the effectiveness of the proposed active controllers, where different road conditions are considered in order to reveal the closed-loop system performance in detail.Index Terms-Active control, adaptive control, backstepping control, vehicle suspension system. 0018-9545 (c) 2015 IEEE. Personal use is permitted, but republication/redistribution requires IEEE permission. See http://www.ieee.org/publications_standards/publications/rights/index.html for more information.This article has been accepted for publication in a future issue of this journal, but has not been fully edited. Content may change prior to final publication. Citation information: DOI 10.1109/TVT.2015.2437455, IEEE Transactions on Vehicular Technology 2 0018-9545 (c)