Resilient control of flexible hypersonic vehicles against unmatched distributed faults

This paper studies a robust fault compensation and vibration suppression problem of flexible hypersonic vehicles.The controlled plant is represented by a cascade system composed of a nonlinear Ordinary Differential Equation(ODE)and an Euler-Bernoulli Beam Equation(EBBE),in which the vibration dynamics is coupled with the rigid dynamics and suffers from distributed faults.A state differential transformation is introduced to transfer distributed faults to an EBBE boundary and a longitudinal dynamics is refined by utilizing T-S fuzzy IF-THEN rules.A novel T-S fuzzy based fault-tolerant control algorithm is developed and related stability conditions are established.The robust exponential stability and well-posedness are proved by using the modified l_(0)-semigroup based Lyapunov direct approach.A simulation study on the longitudinal dynamics of flexible hypersonic vehicles effectively verifies the validity of the developed theoretical results.

An adaptive sliding mode controller design to cope with unmatched uncertainties and disturbance in a MEMS voltage reference source

Tunable micro-electro-mechanical systems(MEMS)capacitors as the fundamental parts are embedded in MEMS AC voltage reference sources(VRS).Being concerned with the accuracy of the output voltage in the reference sources,it gets important to address uncertainties in the physical parameters of the MEMS capacitor.The uncertainties have the great inevitable potentiality of bringing about output voltage perturbation.The output deterioration is more remarkable when the uncertainties are accompanied by disturbance and noise.Manufacturers have been making great attempts to make the MEMS adjustable capacitor with desired rigorous physical characteristics.They have also tried to mitigate physical parameter veracity.However,ambiguity in the values of the parameters inescapably occurs in fabrication procedures since the micro-machining process might itself suffer from uncertainties.Employing a proportional integral(PI)adaptive sliding mode controller(ASMC),both terms of matched and unmatched uncertainties as well as the disturbance,are addressed in this work for the MEMS AC VRS so that a strict voltage is stabilized while the system is simultaneously subjected into uncertainties and exogenous disturbance.Cross-talk,some inertial forces,and electrostatic coercions may appear as matched and unmatched disturbances.Alteration in stiffness and damping coefficients might also take place as matched uncertainties due to variations in the fabrication process or even working environment.The simulation results in the paper are persuasive and the controller design has shown a satisfactory tracking performance.

Finite-time convergence of an nth nonlinear system with unmatched disturbance and its application in integrated guidance and control system

The finite-time convergence problem of an nth nonlinear system with unmatched disturbance is primarily studied in this paper. During the recursive procedure, a new finite-timecontroller is designed and proven by adding a sign function and a power integrator. Meanwhile, a C1 positive definite and proper Lyapunov function, which satisfies the finite-timeLyapunov stability law, is designed. Finally, the designed finite-time controller is appliedto some examples and an application of integrated guidance and control system to testand verify its advantage and practicability.

Neural network-based adaptive sliding mode control for underactuated dual overhead cranes suffering from matched and unmatched disturbances

To improve transportation capacity,dual overhead crane systems(DOCSs)are playing an increasingly important role in the transportation of large/heavy cargos and containers.Unfortunately,when trying to deal with the control problem,current methods fail to fully consider such factors as external disturbances,input dead zones,parameter uncertainties,and other unmodeled dynamics that DOCSs usually suffer from.As a result,dramatic degradation is caused in the control performance,which badly hinders the practical applications of DOCSs.Motivated by this fact,this paper designs a neural network-based adaptive sliding mode control(SMC)method for DOCS to solve the aforementioned issues,which achieves satisfactory control performance for both actuated and underactuated state variables,even in the presence of matched and mismatched disturbances.The asymptotic stability of the desired equilibrium point is proved with rigorous Lyapunov-based analysis.Finally,extensive hardware experimental results are collected to verify the efficiency and robustness of the proposed method.

Adaptive Dynamic Surface Control for Integrated Missile Guidance and Autopilot

Integrated guidance and control for homing missiles utilizing adaptive dynamic surface control approach is considered based on the three channels independence design idea. A time-varying integrated guidance and control model with unmatched uncertainties is first formulated for the pitch channel, and an adaptive dynamic surface control algorithm is further developed to deal with these unmatched uncertainties. It is proved that the proposed feedback controller can ensure not only the accuracy of target interception, but also the stability of the missile dynamics. Then, the same control approach is further applied to the control design of the yaw and roll channels. The 6-degree-of-freedom （6-DOF） nonlinear missile simulation results demonstrate the feasibility and advantage of the proposed integrated guidance and control design scheme.

A Comparison of Hierarchical Bayesian Models for Small Area Estimation of Counts

Small area estimation (SAE) tackles the problem of providing reliable estimates for small areas, i.e., subsets of the population for which sample information is not sufficient to warrant the use of a direct estimator. Hierarchical Bayesian approach to SAE problems offers several advantages over traditional SAE models including the ability of appropriately accounting for the type of surveyed variable. In this paper, a number of model specifications for estimating small area counts are discussed and their relative merits are illustrated. We conducted a simulation study by reproducing in a simplified form the Italian Labour Force Survey and taking the Local Labor Markets as target areas. Simulated data were generated by assuming population characteristics of interest as well as survey sampling design as known. In one set of experiments, numbers of employment/unemployment from census data were utilized, in others population characteristics were varied. Results show persistent model failures for some standard Fay-Herriot specifications and for generalized linear Poisson models with (log-)normal sampling stage, whilst either unmatched or nonnormal sampling stage models get the best performance in terms of bias, accuracy and reliability. Though, the study also found that any model noticeably improves on its performance by letting sampling variances be stochastically determined rather than assumed as known as is the general practice. Moreover, we address the issue of model determination to point out limits and possible deceptions of commonly used criteria for model selection and checking in SAE context.

RIDDLE OF THE SANDS

"There is a beauty in the North, matchless and unmatched; one glance from her felled a city,another glance felled a kingdom"goes "The BeautySong,"a famous Han dynasty (206 BCE -220CE)ballad composed by court musician Li Yannian in the second century BCE.