Unmeasured States Dependent Growth Research Articles

Global output‐feedback adaptive regulation for planar time‐delay nonlinear systems with polynomial growth

AbstractThis paper addresses the problem of the global adaptive regulation via output feedback for a class of uncertain planar time‐varying delay nonlinear systems with an unknown control coefficient and unmeasured states dependent growth. The growth rate is the form of an unknown constant multiplying polynomial of output, and the upper bounds of unknown control coefficient and unknown time‐varying delay are both not required to be known. A systematic non‐identifier‐based output‐feedback control scheme is developed by combining the idea of universal control, backstepping technique, and Lyapunov–Krasovskii theorem. The global regulation of nonlinear systems and the global boundedness of the closed‐loop system can be simultaneously achieved by the designed controller based on a dynamic high‐gain observer and a proper update law. A practical example illustrates the efficiency of the proposed method.

Global output-feedback adaptive stabilization for uncertain nonlinear systems with polynomial growth nonlinearities

In this paper, the problem of global adaptive stabilization by smooth output-feedback is investigated for a class of uncertain nonlinear system with unmeasured states dependent growth. The highlight of the paper lies in that the growth rate with output-dependent polynomial growth and the measurement sensitivity are both unknown, or the dimension of the closed-loop system is significantly reduced. To handle these, a distinct observer with two high-gains is introduced and two dynamic high-gains are updated in the new forms. Motivated by the closely related works, we propose a systematic non-identifier based output feedback control scheme by using the idea of universal control and backstepping technique. The designed controller can globally regulate the states of the original system and the observer while maintaining global boundedness of the closed-loop system. A numerical example is given to demonstrate the effectiveness of the proposed method.

A switching adaptive scheme for global output‐feedback stabilization of inherent nonlinear systems with unknown control direction

AbstractThis article is devoted to the global output‐feedback stabilization of nonlinear systems with unknown control directions and unmeasured states dependent growth whose rate is an unknown arbitrary function of output. In view of limited capability of continuous feedback in compensating system uncertainties and nonlinearities, a novel switching adaptive scheme is proposed. The scheme involves a logic‐based switching mechanism, based on which, a proper controller is selected (from a family of candidate controllers) to act on the system during its execution interval. The main differences between the proposed scheme and those in the related works are as follows. First, the set of candidate controllers is determined online, rather than specified in advance, which provides foundations for compensating arbitrary function‐of‐output growth rate. Second, an iterative function composed of system memory signals is introduced into the switching mechanism, aiming to evaluate the differences between the system states and observe states. Finally, when switching stops, only by introducing an extra transformation and adopting elaborate analysis, can the boundedness of the closed‐loop system signals be obtained, rather than those in the related works where the boundedness can be naturally established once switching stops. The constructed switching adaptive controller guarantees that all the signals of the resulting closed‐loop system are bounded and ultimately converge to zero.

Event-triggered controller via adaptive output-feedback for a class of uncertain nonlinear systems

This paper addresses the global stabilisation via adaptive event-triggered output-feedback for a class of uncertain nonlinear systems. Remarkably, the systems under investigation simultaneously allow large uncertainties and linearly unmeasured states dependent growth for the first time in the event-triggered framework, for which a dynamic high gain and an observer based on the high gain are introduced. By integrating compensation and time-varying strategies, an adaptive event-triggered output-feedback controller is established. Particularly, a new event-triggering mechanism is introduced, in which the time-varying threshold (strictly positive and gradually decaying) is key to ensure the validity of the event-triggered controller and achieve the convergence. A simulation example is given to illustrate the effectiveness of the proposed approach.

Global output-feedback stabilization for high-order nonlinear systems with unknown growth rate

Summary This paper considers the global stabilization via time-varying output-feedback for a class of high-order uncertain nonlinear systems with rather weak assumptions. Essentially different from the existing literature, the systems under investigation simultaneously have more serious nonlinearities, unknowns, immeasurableness, and time-variations, which are indicated from the unknown time-varying control coefficients and the higher-order and lower-order unmeasured states dependent growth with the rate of unknown function of time and output. Recognizing that adaptive technique is quite hard to apply, a time-varying design scheme is proposed by combining time-varying approach, certainty equivalence principle and homogeneous domination approach. One key point in the design scheme is the selection of the design functions of time, in order to compensate/capture the serious unknowns and serious time-variations, and another one is the design of a time-varying observer to rebuild the unmeasured system states. With the appropriate choice of the involved design functions, the designed controller makes all the signals of the closed-loop system globally bounded and ultimately converge to zero. Copyright © 2016 John Wiley & Sons, Ltd.

Global output-feedback stabilization for a class of uncertain time-varying nonlinear systems

This paper investigates the global output-feedback stabilization for a class of uncertain time-varying nonlinear systems. The remarkable structure of the systems is the presence of uncertain control coefficients and unmeasured states dependent growth whose rate is inherently time-varying and of unknown polynomial-of-output, and consequently the systems have heavy nonlinearities, serious uncertainties/unknowns and serious time-variations. This forces us to explore a time-varying plus adaptive methodology to realize the task of output-feedback stabilization, rather than a purely adaptive one. Detailedly, based on a time-varying observer and transformation, an output-feedback controller is designed by skillfully combining adaptive technique, time-varying technique and well-known backstepping method. It is shown that, with the appropriate choice of the design parameters/functions, all the signals of the closed-loop system are bounded, and furthermore, the original system states globally converge to zero. It is worth mentioning that, the heavy nonlinearities are compensated by an updating law, while the serious unknowns and time-variations are compensated by a time-varying function. The designed controller is still valid when the system has an additive input disturbance which, essentially different from those studied previously, may not be periodic or bounded by any known constant.

Global stabilization via time-varying output-feedback for stochastic nonlinear systems with unknown growth rate

This paper considers the global stabilization via time-varying output-feedback for a class of stochastic nonlinear systems. Different from the related existing literature, the systems possess serious uncertainties/unknowns which are reflected in the uncertain control coefficient and the unknown growth rate of the unmeasured states dependent growth. To deal with these serious uncertainties/unknowns, a time-varying framework, rather than an adaptive one, is proposed in this paper since the latter has not been successfully employed in the topic. Detailedly, due to the absence of precise information on the control coefficient, time-varying K-filters are introduced to construct the unmeasured system states. By a delicate time-scaling transformation, a time-scaled entire system is derived, and from which, the design scheme of a time-varying output-feedback controller is developed by backstepping method and time-varying technique. It is shown that all signals of the resulting closed-loop system converge to zero a.s., and furthermore, when serious time-variations exist as well, it suffices to find a fast enough time-varying gain for the control design scheme. A simulation example is given to show the effectiveness of the theoretical results.

Global output-feedback stabilization for high-order nonlinear systems with unknown control coefficients

This paper is concerned with the global stabilization via time-varying outputfeedback for a class of high-order uncertain nonlinear systems. The remarkable feature of the systems, that is, the unknown time-varying control coefficients and the unmeasured states dependent growth with unknown time-varying rate, makes the existing control design methods unapplicable. By skillfully combining time-varying approach and certainty equivalence principle, a time-varying output-feedback control design scheme is proposed in the paper. It is worth mentioning that the serious unknowns and time-variations in the systems are compensated by introducing time-varying design functions, rather than employing adaptive approach. With the appropriate choices of the design functions, all the states of the closed-loop system are globally bounded and converge to zero.

Global output-feedback tracking for nonlinear cascade systems with unknown growth rate and control coefficients

This paper deals with the global practical tracking problem by output-feedback for a class of uncertain cascade systems with zero-dynamics and unmeasured states dependent growth. The systems investigated are substantially different from the closely related works, and have zero-dynamics, unknown growth rate, and unknown time-varying control coefficients. This makes the problem much more difficult to solve. Motivated by the authors’ recent works, this paper proposes a new adaptive control scheme to achieve the global practical tracking. It is shown that the designed controller guarantees that the state of the resulting closed-loop system is globally bounded and the tracking error converges to a prescribed arbitrarily small neighborhood of the origin after a finite time. This is achieved by combining the methods of universal control and dead zone with backstepping technique, and using the framework of performance analysis in the closely related works. A numerical example demonstrates the effectiveness of the theoretical results.

Global practical tracking by output feedback for nonlinear systems with unknown growth rate and time delay.

This paper is the further investigation of work of Yan and Liu, 2011, and considers the global practical tracking problem by output feedback for a class of uncertain nonlinear systems with not only unmeasured states dependent growth but also time-varying time delay. Compared with the closely related works, the remarkableness of the paper is that the time-varying time delay and unmeasurable states are permitted in the system nonlinear growth. Motivated by the related tracking results and flexibly using the ideas and techniques of universal control and dead zone, an adaptive output-feedback tracking controller is explicitly designed with the help of a new Lyapunov-Krasovskii functional, to make the tracking error prescribed arbitrarily small after a finite time while keeping all the closed-loop signals bounded. A numerical example demonstrates the effectiveness of the results.

New results on global output-feedback stabilization for nonlinear systems with unknown growth rate

In this paper, the global asymptotic stabilization by output feedback is investigated for a class of uncertain nonlinear systems with unmeasured states dependent growth. Compared with the closely related works, the remarkableness of the paper is that either the growth rate is an unknown constant or the dimension of the closed-loop system is significantly reduced, mainly due to the introduction of a distinct dynamic high-gain observer based on a new updating law. Motivated by the related stabilization results, and by skillfully using the methods of universal control and backstepping, we obtain the design scheme to an adaptive output-feedback stabilizing controller to guarantee the global asymptotic stability of the resulting closed-loop system. Additionally, a numerical example is considered to demonstrate the effectiveness of the proposed method.

Global practical tracking by output-feedback for nonlinear systems with unknown growth rate

This paper is devoted to the global practical tracking by output-feedback for a class of uncertain nonlinear systems with only the tracking error measurable. Different from the closely related works, the systems have unmeasured states dependent growth with unknown constant rate, and the reference signal, as well as its first order derivative, has unknown bound. Mainly because of these, the tracking problem can hardly be solved by straightforwardly extending the existing results. In the paper, motivated by the related stabilization results, and flexibly using the ideas of universal control and dead zone, an adaptive output-feedback controller is designed to make the tracking error prescribed arbitrarily small after a finite time while keeping all the states of the closed-loop system bounded. A numerical example demonstrates the effectiveness of the theoretical results.

Adaptive output feedback stabilization for a class of nonlinear systems with inherent nonlinearities and uncertainties

AbstractThis paper investigates the problem of adaptive stabilization by output feedback for a class of uncertain nonlinear systems. The distinguishing feature of such a class of systems is the presence of uncertain control coefficient and unmeasured states dependent growth with growth rate of polynomial‐of‐output multiplying an unknown constant. First, new high‐gain K‐filters with two dynamic gains are introduced, and an appropriate state observer is constructed based on the K‐filters. Then, motivated by the universal control idea, the backstepping scheme is successfully developed for the adaptive output feedback control design. By appropriate choice of the design parameters, the global stability of the closed‐loop system can be guaranteed. Finally, numerical simulations are provided to illustrate the correctness of the theoretical results. Copyright © 2010 John Wiley & Sons, Ltd.

Output-feedback Control for a Class of Uncertain Nonlinear Systems with Linearly Unmeasured States Dependent Growth

摘要: 研究了一类具有不确定控制系数, 稳定零动态和增长线性依赖于不可测状态非线性系统的输出反馈全局镇定问题. 首先引入两种恰当的状态变换, 将原系统变为具有确定虚拟控制系数和分离零动态的新系统. 然后, 构造了基于高增益K-滤波器的恰当观测器, 并且应用反推技术成功设计了输出反馈控制器. 通过选择恰当的设计参数, 可以保证闭环系统的全局渐近稳定性. 给出的仿真算例验证了理论结果的正确性和所提出方法的有效性. 关键词: 非线性系统 / 不确定控制系数 / 高增益K-滤波器 / 输出反馈 / 依赖于不可测状态增长 / 全局渐近稳定性

Output-feedback Control for a Class of Uncertain Nonlinear Systems with Linearly Unmeasured States Dependent Growth

This paper is devoted to the problem of global stabilization by output-feedback for a class of nonlinear systems with uncertain control coefficients, stable zero-dynamics, and linearly unmeasured states dependent growth. First, by introducing two kinds of appropriate state transformations, the original system is converted into a new system with deterministic virtual control coefficients and the separated zero-dynamics. Then, a suitable observer based on high-gain K-filters is constructed for the new system, and the backstepping design approach is successfully proposed to the output-feedback controller. It is shown that the global asymptotic stability of the closed-loop system can be guaranteed by the appropriate choice of the design parameters. A simulation example is also provided to show the correctness of the theoretical results and the effectiveness of the proposed approach.

Global stabilization by output feedback for a class of nonlinear systems with uncertain control coefficients and unmeasured states dependent growth

This paper considers the problem of global stabilization by output feedback for a class of nonlinear systems with uncertain control coefficients and with unmeasured states dependent growth. Mainly due to the uncertain control coefficients, the problem has remained unsolved and its major difficulty stems from the inapplicability of the commonly used high-gain like observer. By introducing an appropriate state transformation and a thoroughly novel observer based on high-gain K-filters, the backstepping design approach is successfully proposed to the output-feedback controller for this class of systems. It is shown that the global asymptotic stability of the closed-loop system can be guaranteed by the appropriate choice of the control parameters.