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This work extends the existing output feedback stabilization schemes for the systems in a "perturbed chain-of-integrator" form. In particular, we further relax the triangular-type conditions imposed on the perturbed terms and analyze the robust property of the linear output feedback control law using the newly proposed condition. Index Terms--Global exponential stabilization, output feedback control.

Summary: In this article, we consider a problem of global exponential stabilization for a class of nonlinear systems with the perturbed nonlinearity by output feedback. We provide a newly designed observer‐based output feedback controller with three gain‐scaling factors to deal with extended structure of nonlinearity and larger growth rate of nonlinearity over the existing results. Utilizing three gain‐scaling factors, we have more flexibility in selecting control parameters. Moreover, we present two procedures for selecting gain‐scaling parameters which are associated with stabilizing the system and improving the convergence rate of the system states and observer errors, respectively. Via numerical and practical examples, we illustrate the improved features of the proposed control scheme over the existing schemes. [ABSTRACT FROM AUTHOR]

Summary: In this paper, we consider a global regulation problem for a class of feedforward nonlinear systems. The key features of our considered system are identified by the presence of uncertain time‐varying parameters associated with main diagonal states and input and an unknown time‐varying delay in the input. Moreover, the growth rates of nonlinearity and the input‐delay are only known to be finite. To solve our considered problem, we give a process to obtain a compact set that contains the allowed time‐varying parameters. Then, we propose an adaptive controller which handles both unknown growth rate of nonlinearity and input‐delay for system regulation. We carry out the rigorous system analysis and show the effectiveness of our proposed control scheme via an application example. [ABSTRACT FROM AUTHOR]

Recently, there have been a series of results regarding two time optimal control problems for a class of linear and nonlinear systems ‐ one is to keep the system states within certain bound for the longest time during feedback disruption and the other is to derive the system states to near the origin as fast as possible after feedback recovery, both under bounded control inputs. These are called maximal and minimal time optimal control problems, respectively. In the existing results, a bang‐bang controller has been commonly suggested as the actual implementation of the optimal controller. In this paper, we suggest a modified version of the bang‐bang controller which can also serve as an approximate optimal controller. Our proposed controller provides the (near) optimal performance with (i) possible reduction of a number of switchings; (ii) possible reduction of control input magnitude. [ABSTRACT FROM AUTHOR]

The process of periodic sampling is investigated for a class of nonlinear systems. The objective is to achieve the longest sampling period that is compatible with a specified error bound. It is shown that there are robust optimal controllers that achieve this objective. It is also shown that the performance of such optimal controllers can be approximated by bang-bang controllers – controllers that are relatively easy to design and implement. [ABSTRACT FROM AUTHOR]

The problem of designing robust optimal controllers to reduce in minimal time operating errors that had accumulated during a period of feedback loss is revisited, with the objective of imposing a constraint on the maximal overshoot of the controlled system. It is shown that robust optimal controllers that satisfy this constraint exist under rather broad conditions. It is also shown that optimal performance can be closely approximated by bang–bang controllers – controllers that are relatively easy to design and implement. [ABSTRACT FROM AUTHOR]

The problem of reducing operating errors after a feedback disruption is considered for a class of nonlinear delay-differential systems. It is shown that there are optimal controllers that reduce such errors in minimal time, once feedback has been restored. It is further shown that optimal performance can be approximated by bang-bang controllers – controllers that are easy to design and implement. [ABSTRACT FROM AUTHOR]

Summary: In this paper, we provide a robust observer‐based output feedback control scheme for a class of nonlinear systems where there are uncertain triangular and nontriangular nonlinearities, nontrivial diagonal terms, and external disturbance. The presence of diagonal terms is the main generalized feature over the existing results. In order to handle the diagonal terms, there is a gain‐scaling factor in the proposed controller. Through the analysis, we show that all states and observer errors of the controlled system remain bounded. Moreover, the ultimate bounds of some states and observer errors can be made (arbitrarily) small by adjusting the gain‐scaling factor reflecting on the structure of nonlinearities and external disturbance. The validity of our control scheme is experimentally verified via the ball position control of an electromagnetic levitation system. [ABSTRACT FROM AUTHOR]

Abstract: In this paper, a robust optimal control problem of nonlinear systems with system disturbance during feedback disruption is considered. This is an extended work of previous time‐delay optimal control results, by adding external disturbance in the considered system. It is shown that there exists an optimal input signal which keeps the performance error within the specified bound for the longest time. Then, it is shown that such an optimal input signal can be approximated by an implementable bang‐bang input signal in terms of control performance. Two examples are given for illustration. [ABSTRACT FROM AUTHOR]

The problem of maintaining low operating errors during feedback outages is considered for a class of nonlinear systems with time-delays in the input channel. It is shown that there are optimal controllers that keep operating errors below a specified bound for the longest time possible. Furthermore, it is shown that optimal performance can be approximated as closely as desired by using bang-bang controllers – controllers that are relatively easy to calculate and implement. [ABSTRACT FROM PUBLISHER]

In this paper, we consider a control problem for a class of uncertain nonlinear systems in which there exists an unknown time-varying delay in the input and lower triangular nonlinearities. Usually, in the existing results, input delays have been coupled with feedforward (or upper triangular) nonlinearities; in other words, the combination of lower triangular nonlinearities and input delay has been rare. Motivated by the existing controller for input-delayed chain of integrators with nonlinearity, we show that the control of input-delayed nonlinear systems with two particular types of lower triangular nonlinearities can be done. As a control solution, we propose a newly designed feedback controller whose main features are its dynamic gain and non-predictor approach. Three examples are given for illustration. [ABSTRACT FROM PUBLISHER]

In this paper, we consider a global regulation problem of a class of nonlinear systems that have uncertain high-order nonlinear terms. In particular, we introduce new high-order lower triangular and non-triangular conditions and propose a controller with dynamic gains to regulate the system with uncertain high-order nonlinearities. In designing our controller, the information of the growth rate is not required, and the forms of the high-order nonlinearities are more relaxed. We verify that the proposed method is applicable to the system which cannot be regulated by the existing methods. Examples and simulation results are given for clear illustration. Copyright © 2016 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]