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Compensation for Heterogeneous Unknowns and Performance-Prescribed Consensus

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IEEE/CAA Journal of Automatica Sinica 2025年第1期 173-182页

作者： Linzhen Yu yungang Liu the school of Control Science and Engineering Shandong University

In this paper, the multi-agent systems(MASs) typically with heterogeneous unknown nonlinearities and nonidentical unknown control coefficients are studied. Although the model information of MASs is coarse, the leader-following consensus is still pursued, with a prescribed performance and zero consensus errors. Leveraging a powerful funnel control strategy, a fully distributed and completely relative-state-dependent protocol is designed. Distinctively, the time-varying function characterizing the performance boundary is introduced, not only to construct the funnel gains but also as an indispensable part of the protocol,enhancing the control ability and enabling the consensus errors to converge to zero(rather than a residual set). Remark that when control directions are unknown, coexisting with inherent system nonlinearities, it is essential to incorporate an additional compensation mechanism while imposing a hierarchical structure of communication topology for the control design and analysis. Simulation examples are given to illustrate the effectiveness of the theoretical results.

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Coastal wetlands in Lianyungang,Jiangsu Province,China:probably the most important site globally for the Asian Dowitcher(Limnodromus semipalmatus)

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Avian Research 2021年第3期12卷 364-374页

作者： Ziyou Yang Jing Li Yongxiang Han Chris J.Hassell Kar-Sin Katherine Leung David S.Melville Yat-tung Yu Lin Zhang Chi-Yeung Choi Spoon-Billed Sandpiper(Shanghai)Environmental Protection Technology Co. Ltd.Shanghai 201100China Lianyungang Xugou Primary school Lian-yungang 222042China Global Flyway Network PO Box 3089BroomeWA 6725Australia Hong Kong Waterbirds Ringing Group Mai Po Nature ReserveHong KongChina 1261 Dovedale Road RD 2 WakefieldNelson 7096New Zealand Hong Kong Bird Watching Society 7CV Ga Building532 Castle Peak RoadLai Chi KokKowloonHong KongChina school of Environmental Science and Engineering Southern University of Science and TechnologyShenzhen 518055China

Background:Despite an increasing number of surveys and a growing interest in birdwatching,the population and distribution of Asian Dowitcher(Limnodromus semipalmatus),a species endemic to the East Asian-Australasian and Central Asian Flyways,remains poorly understood,and published information about the species is largely *** boreal spring 2019,over 22,432 Asian Dowitchers were recorded in a coastal wetland at Lianyungang,Jiangsu Prov-ince,China,constituting 97.5%of its estimated global ***:In 2019 and 2020,we conducted field surveys at Lianyungang to determine the numbers of Asian Dow-itchers using the area during both southward and northward *** also assessed the distribution and abun-dance of Asian Dowitchers elsewhere along the China coast by searching literature and consulting expert ***:The coastal wetlands of Lianyungang are the most important stopover site for Asian Dowitchers during both northward and southward migrations;they supported over 90%of the estimated global population during north-ward migration in two consecutive years(May 2019 and 2020).This area also supported at least 15.83%and 28.42%(or 30.74%and 53.51%using modelled estimates)of the global population during southward migration in 2019 and 2020 *** wetlands in the west and north of Bohai Bay also have been important stopover sites for the species since the *** comprehensive,long-term monitoring data are lacking,available evidence sug-gests that the population of the species may have ***:The high concentration of Asian Dowitchers at Lianyungang during migration means the species is highly susceptible to human disturbances and natural stochastic *** coastal wetlands of Lianyungang should be protected and potentially qualify for inclusion in China’s forthcoming nomination for World Heritage listing of Migratory Bird Sanctuaries along the Coast of Yellow Sea-Bohai Gulf of China(Phase II)in ***

关键词： Lianyungang Limnodromus semipalmatus Shorebird Stopover ecology Yellow Sea World Heritage

Global adaptive output-feedback tracking with prescribed performance for uncertain nonlinear systems

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Science China(Information Sciences) 2024年第5期67卷 150-164页

作者： Yuan WANG yungang LIU school of Control Science and Engineering Shandong University

At present, one typical control strategy for guaranteeing transient and steady-state performance is funnel control and prescribed performance control. The strategy features completely discarding the system nonlinearities, even if they are completely known and available. Such an intrinsic feature requires the controller to produce a larger control effect to eliminate the negative impact caused by the high nonlinearities, leading to a conservative controller. In this paper, we fully take advantage of known information on nonlinearities in control design, instead of completely discarding it as done in funnel control. Particularly, we leverage adaptive techniques(i.e., high-gain dynamic compensation) to deal with unknown system nonlinearities. Meanwhile, we integrate the tools of output feedback, tracking control, and the performance *** such, an adaptive output-feedback scheme is developed for global tracking with spatiotemporal performance specifications: arbitrarily given tracking accuracy and accuracy-ensured time. A simulation example supports the developed approach.

关键词： uncertain nonlinear systems output feedback prescribed performance unknown control direction dynamic high gain global tracking

Adaptive output-feedback tracking for nonlinear systems with unknown control direction and generic inverse dynamics

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Science China(Information Sciences) 2022年第8期65卷 134-149页

作者： Yuan WANG yungang LIU school of Control Science and Engineering Shandong University

This paper studies adaptive output-feedback tracking for a class of typical uncertain nonlinear systems. In the context of unknown control direction, a generic uncertainty encountered inevitably in practice is adequately taken into consideration, i.e., the ISpS(input-to-state practically stable) inverse dynamics acting as the dynamic differences between the real plants and the models. Besides, the systems in question also permit two critical ingredients, i.e., unmeasured-state dependent nonlinearities and arbitrary functionof-output growth on unknown system nonlinearities. The three ingredients together largely challenge the feasibility/availability of practical tracking by means of output feedback. Nevertheless, a new control strategy is proposed by flexibly integrating the dynamic compensation based on Nussbaum-type gain, backstepping design technique together with the refined pseudo-sign and pseudo-dead-zone functions that were introduced for the first time in our previous studies. The two refined functions, which are sufficiently smooth, can moderately avoid the use of smooth domination/treatment in control design and can potentially render the attained control strategy tighter and less conservative. Moreover, to keep the order of the closed-loop system at a low level, an n-dimensional filter with a dynamic high gain is delicately devised instead of a2 n-dimensional one used in the relevant literature. It turns out that the proposed adaptive output-feedback controller is capable of guaranteeing the global boundedness of all states of the resulting closed-loop system,while steering the system tracking error to enter, in finite time, a prescribed λ-neighborhood of the origin and keeping it inside thereafter. A simulation example is provided to demonstrate the proposed approach.

关键词： nonlinear systems ISpS inverse dynamics unknown control direction practical output tracking global output feedback adaptive compensation

STABILIZATION OF COUPLED PDE-ODE SYSTEMS WITH SPATIALLY VARYING COEFFICIENT

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Journal of Systems Science & Complexity 2013年第2期26卷 151-174页

作者： LI Jian LIU yungang school of Control Science and Engineering Shandong University

The paper is concerned with the stabilization of a class of coupled PDE-ODE systems with spatially varying coefficient,via state-feedback or *** system is more general than that of the related literature due to the presence of the spatially varying coefficient which makes the problem more difficult to *** infinite-dimensional backstepping method,both state-feedback and output-feedback stabilizing controllers are explicitly constructed,which guarantee that the closed-loop system is exponentially stable in the sense of certain *** is worthwhile pointing out that,in the case of output-feedback,by appropriately choosing the state observer gains,the severe restriction on the ODE sub-system in the existing results is completely removed.A simulation example is presented to illustrate the effectiveness of the proposed method.

关键词： Coupled PDE-ODE systems infinite-dimensional backstepping transformation spatially varying coefficient stabilization.

Adaptive control of nonlinear systems with severe uncertainties in the input powers

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Science China(Information Sciences) 2021年第1期64卷 227-238页

作者： Linzhen YU yungang LIU Yongchao MAN school of Control Science and Engineering Shandong University

In this study, we discuss global adaptive stabilization for a class of uncertain nonlinear *** input powers of the system are unknown, and the upper bound and the nonzero lower bound are not known in advance. This suggests that the system suffers from severe uncertainties with respect to the input powers when compared with the related literature, which would considerably challenge the control design. The switching-based strategy can compensate for severe system uncertainties, especially new types of uncertainties, including those associated with the input powers. Herein, a switching adaptive controller is successfully designed to ensure that the resulting closed-loop system states are globally bounded and ultimately converge to the origin(the equilibrium point). The proposed controller is extended to the systems with unknown control directions by redefining the involved switching sequences. A simulation example demonstrates the effectiveness of the proposed switching adaptive controller.

关键词： nonlinear systems severe uncertainties global stabilization unknown input powers switching adaptive control

Global practical tracking with prescribed transient performance for inherently nonlinear systems with extremely severe uncertainties

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Science China(Information Sciences) 2019年第2期62卷 85-100页

作者： Fengzhong LI yungang LIU school of Control Science and Engineering Shandong University

This paper considers the global practical tracking for a class of uncertain nonlinear systems. Remarkably, the systems under investigation admit rather inherent nonlinearities, and especially allow arguably the most severe uncertainties: unknown control directions and non-parametric uncertainties. Despite this,a refined tracking objective, rather than a reduced one, is sought. That is, not only pre-specified arbitrary tracking accuracy is guaranteed, but also certain prescribed transient performance(e.g., arrival time and maximum overshoot) is ensured to better meet real applications. To solve the problem, a new tracking scheme is established, crucially introducing delicate time-varying gains to counteract the severe uncertainties and guarantee the prescribed performance. It is shown that the designed controller renders the tracking error to forever evolve within a prescribed performance funnel, through which the desired tracking objective is accomplished for the systems. Particularly, by subtly specifying the funnel, global fixed-time practical tracking(i.e., that with prescribed arrival time) and semiglobal practical tracking with prescribed maximal overshoot can be achieved for the systems. Moreover, the tracking scheme remains valid in the presence of rather less-restrictive unmodeled dynamics.

关键词： nonlinear systems practical tracking prescribed transient performance unknown control directions non-parametric uncertainties unmodeled dynamics

Global practical tracking via adaptive outputfeedback for uncertain nonlinear systems with generalized control coefficients

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Science China(Information Sciences) 2016年第1期59卷 188-200页

作者： Shaoli JIN yungang LIU school of Control Science and Engineering Shandong University

This paper investigates the global practical tracking via adaptive output-feedback for a class of uncertain nonlinear systems with generalized control coefficients. Notably, the system in question has the function-of-output control coefficients and the serious unknowns in the system and the reference signal, and hence is essentially different from the existing closely related literature. To solve the global practical tracking,a high-gain observer is first introduced to reconstruct the unmeasurable system states, and then an adaptive output-feedback controller is designed. It is worth emphasizing that the gains in the designed observer and controller are functions of time and output, for which a novel updating law of the high-gain is introduced to overcome the additional system nonlinearities and the serious unknowns mentioned above. The designed controller is shown such that all the states of the closed-loop system are globally bounded, and furthermore,tracking error will be ultimately prescribed sufficiently small. A numerical simulation is provided to demonstrate the effectiveness of the proposed approach.

关键词： uncertain nonlinear systems function-of-output control coefficients global practical tracking dynamical high-gain adaptive output-feedback

THE FURTHER RESULT ON GLOBAL PRACTICAL TRACKING FOR HIGH-ORDER UNCERTAIN NONLINEAR SYSTEMS

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Journal of Systems Science & Complexity 2012年第2期25卷 227-237页

作者： Xuehua YAN yungang LIU school of Control Science and Engineering Shandong University

This paper extends the unknown control coefficients with lower and upper constant bounds to the ones which may take arbitrarily large and /or small *** the existing methods are no longer applicable and the technical obstacles caused by the extensions are essential,new control design scheme should be exploited to the global practical *** the approaches of Nussbaum-gain and adding a power integrator,the authors successfully propose the design scheme of the adaptive practical tracking controller for the *** is shown that the designed controller guarantees that all the closed-loop system states are bounded and the tracking error becomes prescribed arbitrarily small after a finite time.

关键词： Adaptive control adding a power integrator global practical tracking Nussbaum-gain,uncertain nonlinear systems unknown control directions.