1,256 publications from this institution
This study deals with the design of a robust fault estimation and fault-tolerant control for vehicle lateral dynamics subject to external disturbance and unknown sensor faults. Firstly, a descriptor state and fault observer is designed to achieve the system state and sensor fault estimates simultaneously. Secondly, based on the information of on-line fault estimates, a robust fault-tolerant controller based on static output-feedback controller (SOFC) design approach is developed. To provide linear matrix inequalities of less conservatism, the results are conducted in the non-quadratic framework dealing with unmeasurable premise variables case. Simulation results show the effectiveness of the proposed control approach when the vehicle road adhesion conditions change and the sideslip angle is unavailable for measurement.
Magnetorheological (MR) dampers have been widely studied and employed to solve the vibration problem in structures such as buildings and bridges. It is known that MR dampers can generate high damping forces with low-energy requirements and low-cost productions. However, the complex dynamics that characterize MR dampers make difficult the control design to achieve the vibration reduction goals in an efficient manner. In this paper, semiactive controllers based on the backstepping and quantitative feedback theory techniques are proposed and their performances are compared with each other on the problem of vibration control in a structure with an MR damper. They are applied to a large-scale three-story building with an MR damper at its first floor subject to seismic motions. The performance of the proposed controllers is experimentally evaluated by means of real-time hybrid testing scheme that accounts for time delays and actuator dynamics, allowing for the test of velocity-dependent devices. Copyright © 2009 John Wiley & Sons, Ltd.
In this paper, accurate trajectory tracking problem of a surface vehicle disturbed by complex marine environments is solved by creating a finite-time control (FTC) scheme whereby the nonsingular fast terminal sliding mode (NFTSM) and finite-time disturbance observer (FDO) techniques are deployed. Salient features are as follows. By devising an FDO, complex disturbances arising from marine environments can be exactly identified within a short time, in conjunction with the defined NFTSM manifold, and thereby contributing to exact trajectory tracking. Finite-time disturbance observation is completely decoupled from the nominal FTC scheme, and achieves stronger disturbance rejection and faster transient response, simultaneously. Both disturbance observation and trajectory tracking errors can exactly reach to zero in a finite time. Simulation results and comparisons are comprehensively conducted on CyberShip II and demonstrate remarkable superiority of the FTC scheme.
This paper is mainly focusing on the problem of high-accuracy tracking control design for a class of nonlinear systems subject to mismatched uncertainties. A novel asymptotic control framework is presented. This is achieved by developing an estimator-based controller with an observer-based estimator, which is applied to precisely estimate all the system uncertainties. It is proved that the overall tracking system can be asymptotically stabilized. The estimation error of the system uncertainties is also ensured to be asymptotically stable. The main contribution of this paper is that the proposed solution can control a more representative class of nonlinear systems. Another key feature of this control framework is that the incorporated observer-based estimator can eliminate the assumption that system uncertainties should vary slowly or even have no variation in the existing estimators for uncertainties. This superior tracking control property of the scheme is validated by a robotic manipulator example.
In this paper the design of unknown inputs proportional integral observers for Takagi-Sugeno (TS) fuzzy models subject to unmeasurable decision variables is proposed. These unknown inputs affect both state and output of the system. The synthesis of these observers is based on two hypotheses that the unknown inputs are under the polynomials form with their kth derivatives zero for the first one and bounded norm for the second one, hence two approaches. The Lyapunov theory and L 2-gain technique are used to develop the stability conditions of such observers in LMIs (linear matrix inequality) formulation. A simulation example is given to validate and compare the proposed design conditions for these two approaches.
The issue of observer-based adaptive sliding mode control of nonlinear Takagi-Sugeno fuzzy systems with semi-Markov switching and immeasurable premise variables is investigated. More general nonlinear systems are described in the model since the selections of premise variables are the states of the system. First, a novel integral sliding surface function is proposed on the observer space, then the sliding mode dynamics and error dynamics are obtained in accordance with estimated premise variables. Second, sufficient conditions for stochastic stability with an H∞ performance disturbance attenuation level γ of the sliding mode dynamics with different input matrices are obtained based on generally uncertain transition rates. Third, an observer-based adaptive controller is synthesized to ensure the finite time reachability of a predefined sliding surface. Finally, the single-link robot arm model is provided to verify the control scheme numerically.
This study investigates the problem of fault detection for a class of fuzzy positive systems with time-varying delays. A new fault sensitivity measure, called L− index, is proposed. The L− fault detection filter design and multiobjective L− /L1 fault detection filter design problems are addressed. A co-positive type Lyapunov–Krasovskii functional is constructed for the performance analysis and fault detection filter design. Sufficient conditions for the existence of such two filers are firstly given, and then the design methods are presented. Finally, two examples are provided to show the effectiveness and applicability of the proposed method.
A wavelet-based approach is presented in this paper to reconstruct acceleration pulse of a vehicle involved in a crash event. The described method for time-frequency analysis is based on techniques which investigate both: time and frequency components of a signal being considered. It is achieved in this work by application of Morlet wavelet properties. Major frequency components which are included in the original acceleration pulse are identified. Subsequently, their times of occurrence are detected as well. Those steps are necessary for multiresolution analysis which leads to creation of a scalegram of the reference signal. Finally, having full insight into the time-frequency components of the analyzed characteristics, the reconstruction of the reference signal is executed — superposition principle allows to combine major signal components yielding the reproduced crash pulse. The comparative analysis between the current method's outcome and the behavior of a real car is performed and reliability of the actual methods and tools is evaluated.
In this paper, the problem of robust multi-objective control design with an H <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">∞</sub> constrain is studied for a class of linear two-time scale systems. The design is based on a new modelling approach under the assumption of norm-boundedness of the fast dynamics. In this method, a portion of the fast dynamics is treated as a norm-bounded perturbation in the design by its maximum possible gain. In this view, the problem of robust multi-objective control design is performed only for the certain dynamics of the two-time scale system, whose order is less than that of the original system. One illustrative example is used to demonstrate the validity of the proposed approach.
In this paper, the problem of stability analysis for a class of neutral systems with mixed time-varying neutral, discrete and distributed delays and nonlinear perturbations are addressed. By introducing a novel Lyapunov-Krasovskii functional and combining the descriptor model transformation, the Leibniz-Newton formula, some free weighting matrices and a suitable change of variables, new sufficient conditions are established for the stability of the considered system, which are neutral-delay-dependent, discrete-delay-range-dependent and distributed-delay-dependent. The conditions are presented in terms of linear matrix inequalities (LMIs) and can be easily solved by existing convex optimization techniques. A numerical example is given to demonstrate the less conservatism of the proposed results over some existence results in the literature.
The demand for low-cost and low-power decoder chips has resulted in renewed interest in low-complexity decoding algorithms. In this paper, a novel theoretical framework for improving the performance of turbo decoding schemes that use the max-log-MAP algorithm is proposed. This framework is based on the concept of maximizing the transfer of mutual information between the component decoders. The improvements in performance can be achieved by using optimized iteration-dependent correction weights to scale the a priori information at the input of each component decoder. A method for the offline computation of the correction weights is derived. It is shown that a performance which approaches that of a turbo decoder using the optimum MAP algorithm can be achieved, while maintaining the advantages of low complexity and insensitivity to input scaling inherent in the max-log-MAP algorithm. The resulting improvements in convergence of the turbo decoding process and the expedited transfer of mutual information between the component decoders are illustrated via extrinsic information transfer (EXIT) charts.
