@article{xue_wu_yuan_2021, title={Robust consensus for linear multi-agent systems with structured uncertainties}, volume={94}, ISSN={["1366-5820"]}, DOI={10.1080/00207179.2019.1612096}, abstractNote={ABSTRACT This paper addresses a robust consensus problem for linear multi-agent systems subject to structured uncertainty and external disturbances under the leaderless framework. A distributed dynamic output-feedback protocol is proposed, which utilises not only relative output information of neighbouring agents but also relative state information of neighbouring controllers. Through model transformations, the robust consensus control problem of multi-agents network is reduced to a set of independent stabilisation problems for single linear subsystems. For robust consensus, it is shown that the analysis and full state-feedback synthesis conditions for such subsystems can be formulated as linear matrix inequality (LMI) optimisation problems. On the other hand, the synthesis condition for dynamic output-feedback protocol is formulated as non-convex bilinear matrix inequality (BMI) optimisation problem. An iterative LMI algorithm is then presented to solve the resulting BMI optimisation problem. An example of multiple mass-spring-damper systems has been used to demonstrate theoretical results.}, number={3}, journal={INTERNATIONAL JOURNAL OF CONTROL}, author={Xue, Xiangming and Wu, Fen and Yuan, Chengzhi}, year={2021}, month={Mar}, pages={675–686} }
 @article{xue_yuan_wu_2019, title={Convexified H-infinity output-feedback consensus synthesis for linear multi-agent systems}, volume={13}, ISSN={["1751-8652"]}, DOI={10.1049/iet-cta.2018.5337}, abstractNote={This study addresses the H
 ∞
 consensus problem for linear multi-agent systems subject to external disturbances under the leaderless framework. A novel distributed dynamic output feedback control protocol is proposed, which utilises not only relative output information of neighbouring agents but also relative state information of neighbouring controllers. Through model transformation, the H
 ∞
 consensus control problem of multi-agents network is reduced to a set of independent H
 ∞
 stabilisation subproblems for n
-dimensional linear systems. Sufficient analysis conditions are derived using the Lyapunov method. An important contribution of this work lies in that the leaderless H
 ∞
 output-feedback consensus synthesis conditions are convexified without introducing any conservatism and formulated as linear matrix inequalities, which can be solved efficiently via convex optimisation. This is achieved by using a novel dynamic output-feedback controller structure. A numerical example has been used to demonstrate the advantage of theoretical results.}, number={11}, journal={IET CONTROL THEORY AND APPLICATIONS}, author={Xue, Xiangming and Yuan, Chengzhi and Wu, Fen}, year={2019}, month={Jul}, pages={1619–1628} }
 @inproceedings{yuan_wu_2016, title={A new hybrid LFT control method for missile autopilot design}, DOI={10.1109/chicc.2016.7554273}, abstractNote={This paper presents a new hybrid gain-scheduling control method for missile autopilot design. The nonlinear missile dynamics is first converted to a switched linear fractional transformation (LFT) model for controller design and synthesis purpose. Then, by using multiple Lyapunov functions and average dwell time (ADT) techniques, a new hybrid gain-scheduling autopilot is designed, which consists of a switching dynamic output-feedback LFT controller and a controller state jump dynamics. The associated control synthesis conditions guaranteeing weighted ℒ 2 stability are formulated in terms of a finite number of linear matrix inequalities (LMIs), which can be solved effectively via convex optimization without parameter-space gridding. Nonlinear simulation studies show the effectiveness of the proposed approach.}, booktitle={Proceedings of the 35th chinese control conference 2016}, author={Yuan, C. Z. and Wu, F.}, year={2016}, pages={5852–5857} }
 @inproceedings{boker_yuan_wu_chakrabortty_2016, title={Aggregate control of clustered networks with inter-cluster time delays}, DOI={10.1109/acc.2016.7526506}, abstractNote={We address a control problem for networks that have multiple dense clusters with sparse interconnection structure. By making use of the time-scale separation properties of such networks, we design state-feedback controllers at the cluster level to guarantee stability in the presence of time varying delays in the inter-cluster feedback channels. Applying results from singular perturbation theory, we show that when these individual controllers are implemented on the actual network model, the closed-loop response is close to that obtained from the approximate models, provided that the clustering is strong and the time delay is below the maximum limit. The design procedure is demonstrated by a simulation example.}, booktitle={2016 american control conference (acc)}, author={Boker, A. M. and Yuan, C. Z. and Wu, F. and Chakrabortty, Aranya}, year={2016}, pages={5340–5345} }
 @article{yuan_wu_2016, title={Dynamic IQC-Based Control of Uncertain LFT Systems With Time-Varying State Delay}, volume={46}, ISSN={["2168-2275"]}, DOI={10.1109/tcyb.2015.2503741}, abstractNote={This paper presents a new exact-memory delay control scheme for a class of uncertain systems with time-varying state delay under the integral quadratic constraint (IQC) framework. The uncertain system is described as a linear fractional transformation model including a state-delayed linear time-invariant (LTI) system and time-varying structured uncertainties. The proposed exact-memory delay controller consists of a linear state-feedback control law and an additional term that captures the delay behavior of the plant. We first explore the delay stability and the L2-gain performance using dynamic IQCs incorporated with quadratic Lyapunov functions. Then, the design of exact-memory controllers that guarantee desired L2-gain performance is examined. The resulting delay control synthesis conditions are formulated in terms of linear matrix inequalities, which are convex on all design variables including the scaling matrices associated with the IQC multipliers. The IQC-based exact-memory control scheme provides a novel approach for delay control designs via convex optimization, and advances existing control methods in two important ways: 1) better controlled performance and 2) simplified design procedure with less computational cost. The effectiveness and advantages of the proposed approach have been demonstrated through numerical studies.}, number={12}, journal={IEEE TRANSACTIONS ON CYBERNETICS}, author={Yuan, Chengzhi and Wu, Fen}, year={2016}, month={Dec}, pages={3320–3329} }
 @inproceedings{yuan_wu_2016, title={Dynamic IQC-based analysis and synthesis of networked control systems}, DOI={10.1109/acc.2016.7526507}, abstractNote={This paper presents a new control design approach for networked control systems under the integral quadratic constraint (IQC) framework. In order to apply the IQC and dissipation theory, the networked control system with network-induced time-varying delays is first transformed to an equivalent linear fractional transformation (LFT) model. As such, dynamic IQCs can be used to capture the input-output behavior of the delay nonlinearities. Then, a novel full-information feedback control law is proposed, which utilizes both plant states and the IQC dynamic states, as well as the network-induced delay amounts, as feedback information. Robust ℓ2 stability analysis of the resulting closed loop is performed via dynamic IQCs. Based on the analysis results, the synthesis conditions for the proposed full-information feedback controller are established in a linear matrix inequality (LMI) form, which can be solved effectively using existing convex optimization algorithms. Finally, a servo motor control system is used to demonstrate the effectiveness of the proposed IQC-based control design scheme.}, booktitle={2016 american control conference (acc)}, author={Yuan, C. Z. and Wu, F.}, year={2016}, pages={5346–5351} }
 @article{yuan_wu_2016, title={Hybrid almost output regulation of linear impulsive systems with average dwell-time}, volume={20}, ISSN={["1878-7460"]}, DOI={10.1016/j.nahs.2015.11.001}, abstractNote={This paper deals with the hybrid almost output regulation problem for a class of linear systems with average dwell-time impulses. The proposed hybrid output regulator is constructed as a linear impulsive system that undergoes synchronous impulses with the controlled plant. Lyapunov-based sufficient conditions of the output regulability and weighted L2 performance for the linear impulsive systems are first derived. Based on the analysis results, the hybrid synthesis problem is formulated in terms of linear matrix equations plus a set of linear matrix inequalities (LMIs). With this hybrid synthesis scheme, both flow and jump dynamics of the hybrid regulator can be jointly designed by solving a convex optimization problem in minimizing the weighted L2 gain from the perturbation signal to the error output. A numerical example is used to demonstrate the proposed approach.}, journal={NONLINEAR ANALYSIS-HYBRID SYSTEMS}, author={Yuan, Chengzhi and Wu, Fen}, year={2016}, month={May}, pages={82–94} }
 @article{yuan_wu_2016, title={Robust H-2 and H-infinity switched feedforward control of uncertain LFT systems}, volume={26}, ISSN={["1099-1239"]}, DOI={10.1002/rnc.3380}, abstractNote={This paper presents a new robust switched feedforward control scheme for a class of uncertain systems described in a standard linear fractional transformation form. First, the analysis conditions for switching stability are derived by using a piecewise Lyapunov function incorporated with the min‐switching control technique. Based on the analysis results, the synthesis conditions are then formulated as a special type of bilinear matrix inequalities, which can be solved by means of linear matrix inequalities and line search. Both robust ℋ2 and ℋ∞ feedforward control problems are considered. The proposed robust switched control scheme outperforms existing robust feedforward control approaches for uncertain systems based on single quadratic Lyapunov function, and leads to less conservative control design. Numerical examples will be used to illustrate the effectiveness and advantages of the proposed results. Copyright © 2015 John Wiley & Sons, Ltd.}, number={9}, journal={INTERNATIONAL JOURNAL OF ROBUST AND NONLINEAR CONTROL}, author={Yuan, Chengzhi and Wu, Fen}, year={2016}, month={Jun}, pages={1841–1856} }
 @article{yuan_wu_2016, title={Robust switching output-feedback control of time-varying polytopic uncertain systems}, volume={89}, ISSN={["1366-5820"]}, DOI={10.1080/00207179.2016.1154607}, abstractNote={ABSTRACT The problem of designing a globally optimal robust output feedback controller for time-varying polytopic uncertain systems is a well-known non-convex optimisation problem. In this paper, new sufficient conditions for both robust and switching output-feedback control syntheses are proposed in terms of bilinear matrix inequalities (BMIs) under the multiple Lyapunov function framework. This set of synthesis conditions is further reduced to a special type of BMIs, which can be solved effectively using linear matrix inequality optimisation plus a line search. The associated robust output-feedback controller is constructed as a switching-type full-order dynamic output-feedback controller, consisting of a family of linear time-invariant subcontrollers and a min-switching logic. The proposed approach features the important property of computational efficiency with stringent performance. Its effectiveness and advantages have been demonstrated through extensive numerical studies.}, number={11}, journal={INTERNATIONAL JOURNAL OF CONTROL}, author={Yuan, Chengzhi and Wu, Fen}, year={2016}, pages={2262–2276} }
 @inproceedings{yuan_wu_duan_2016, title={robust gain-scheduling output feedback control of state-delayed lft systems using dynamic IQCS}, DOI={10.1115/dscc2015-9686}, abstractNote={This paper is concerned with the robust gain-scheduling output feedback control problem for a class of linear parameter-varying systems with time-varying state delay. The controlled plant under consideration is described as a linear fractional transformation (LFT) model of scheduling parameters. Dynamic integral quadratics (IQCs) are employed to characterize the input-output behavior of the state-delay nonlinearity. The robust stability and the L2-gain performance are first analyzed using quadratic Lyapunov function. Then, the design of dynamic output-feedback controllers robust against the plant state-delay nonlinearity and gain-scheduled by parameters is examined. The synthesis conditions of such robust gain-scheduling controllers are formulated in terms of linear matrix inequalities (LMIs) plus a line search, which can be solved effectively using existing algorithms. A numerical example has been used to demonstrate the effectiveness and advantages of the proposed approach.}, booktitle={Proceedings of the ASME 8th Annual Dynamic Systems and Control Conference, 2015, vol 3}, author={Yuan, C. Z. and Wu, F. and Duan, C.}, year={2016} }
 @inproceedings{yuan_duan_wu_2015, title={Almost output regulation of discrete-time switched linear systems}, DOI={10.1109/acc.2015.7171961}, abstractNote={In this paper, we propose a new hybrid control approach for almost output regulation of a class of discrete-time switched linear systems with average dwell time (ADT). Both controlled plant and exosystem are described by switched linear systems. The proposed hybrid controller is constructed as a switching impulsive system, where the controller states will undergo impulsive jumps at each switching instant. By using the ADT technique incorporated with multiple quadratic Lyapunov functions, the hybrid synthesis conditions for almost output regulation with asymptotic stability and weighted ℋ∞ performance are formulated as a set of linear matrix equations and linear matrix inequalities (LMIs), which can be solved effectively. The proposed hybrid control method has been demonstrated through a numerical example.}, booktitle={2015 american control conference (acc)}, author={Yuan, C. Z. and Duan, C. and Wu, F.}, year={2015}, pages={4042–4047} }
 @article{yuan_wu_2015, title={Asynchronous switching output feedback control of discrete-time switched linear systems}, volume={88}, ISSN={["1366-5820"]}, DOI={10.1080/00207179.2015.1016454}, abstractNote={In this paper, the problem of dynamic output-feedback control synthesis is addressed for discrete-time switched linear systems under asynchronous switching. The proposed hybrid controller consists of a standard dynamic output-feedback switching control law and an impulsive reset law induced by controller state jumps. Using the average dwell time technique incorporating with multiple quadratic Lyapunov functions, the switching control synthesis conditions for asymptotic stability with guaranteed weighted ℓ2-gain performance are derived as a set of linear matrix inequalities (LMIs). The proposed hybrid synthesis scheme advances existing design methods for output-feedback asynchronous switching control of switched linear systems in two important aspects: LMI formulation of the synthesis problem; and arbitrary order of the controller state. A numerical example is used to illustrate the effectiveness and advantages of the proposed design technique.}, number={9}, journal={INTERNATIONAL JOURNAL OF CONTROL}, author={Yuan, Chengzhi and Wu, Fen}, year={2015}, month={Sep}, pages={1766–1774} }
 @article{yuan_wu_2015, title={Hybrid Control for Switched Linear Systems With Average Dwell Time}, volume={60}, ISSN={["1558-2523"]}, DOI={10.1109/tac.2014.2322941}, abstractNote={This technical note presents a hybrid control scheme for the output-feedback control of switched linear systems with average dwell time. The proposed hybrid controller consists of a standard switching output-feedback control law and a supervisor enforcing a reset rule for the switching controller states at each switching instant. This hybrid control scheme provides an efficient and systematic way for designing average dwell time switched linear control systems in the sense that the boundary condition can be incorporated into the synthesis problem in a convex formulation. Specifically, both full-order and reduced-order controllers with guaranteed stability and optimal weighted H∞ performance will be solved by linear matrix inequality (LMI) optimizations. Simulation studies are included to illustrate the effectiveness of the proposed approach.}, number={1}, journal={IEEE TRANSACTIONS ON AUTOMATIC CONTROL}, author={Yuan, Chengzhi and Wu, Fen}, year={2015}, month={Jan}, pages={240–245} }
 @inproceedings{yuan_wu_duan_2015, title={Robust switching output feedback control of discrete-time linear polytopic uncertain systems}, DOI={10.1109/chicc.2015.7260096}, abstractNote={This paper presents a new switching control approach for robust output feedback control of a class of discrete-time linear systems subject to polytopic time-varying uncertainties. The proposed robust switching controller, which stabilizes the closed-loop system with a pre-specified H∞ performance level, consists of a family of dynamic output feedback controllers (of an arbitrary state order) and a switching law (the relaxed min-switching strategy). Both stability analysis and control synthesis conditions are derived using a piecewise quadratic Lyapunov function. The switching law combined with the controller gain matrices are jointly synthesized by solving a convex linear matrix inequality (LMI) based optimization problem. An academic example has been used to demonstrate the effectiveness and advantages of the proposed approach.}, booktitle={2015 34th Chinese Control Conference (CCC)}, author={Yuan, C. Z. and Wu, F. and Duan, C.}, year={2015}, pages={2973–2978} }
 @article{yuan_wu_2015, title={Switching control of linear systems subject to asymmetric actuator saturation}, volume={88}, ISSN={["1366-5820"]}, DOI={10.1080/00207179.2014.942884}, abstractNote={In this paper, we study the saturation control problem for linear time-invariant (LTI) systems subject to asymmetric actuator saturation under a switching control framework. The LTI plant with asymmetric saturation is first transformed to an equivalent switched linear model with each subsystem subject to symmetric actuator saturation, based on which a dwell-time switching controller augmented with a controller state reset is then developed by using multiple Lyapunov functions. The controller synthesis conditions are formulated as linear matrix inequalities (LMIs), which can be solved efficiently. Simulation results are also included to illustrate the effectiveness and advantages of the proposed approach.}, number={1}, journal={INTERNATIONAL JOURNAL OF CONTROL}, author={Yuan, Chengzhi and Wu, Fen}, year={2015}, month={Jan}, pages={204–215} }
 @article{yuan_wu_2014, title={Analysis and synthesis of linear hybrid systems with state-triggered jumps}, volume={14}, ISSN={["1878-7460"]}, DOI={10.1016/j.nahs.2014.05.002}, abstractNote={This paper investigates first the stability and L2-gain problems for a class of linear hybrid control systems with state-triggered jumps by using an extended Lyapunov-like function (ELF) technique. The obtained results are then applied to facilitate the joint design of a hybrid controller (linear controller plus reset law) for a continuous-time linear time-invariant (LTI) plant. The hybrid H∞ synthesis conditions are expressed in linear matrix inequalities (LMIs) with two line search parameters. An inverted pendulum example is used to illustrate the effectiveness of the proposed approach.}, journal={NONLINEAR ANALYSIS-HYBRID SYSTEMS}, author={Yuan, Chengzhi and Wu, Fen}, year={2014}, month={Nov}, pages={47–60} }
 @inproceedings{yuan_wu_2014, title={Output feedback reset control of general MIMO LTI systems}, DOI={10.1109/ecc.2014.6862225}, abstractNote={This paper presents a systematic Lyapunov-based approach for output-feedback reset control of linear time-invariant (LTI) systems with a general multiple-input multiple-output (MIMO) configuration. The reset controller consists of a base linear controller and a reset law that enforces resets to the controller states. Based on the extended Lyapunov-like function (ELF) technique, the reset controller with guaranteed exponential stability and weighted L2-gain performance is synthesized by solving a set of linear matrix inequalities (LMIs) with linear search over two scalar variables. A numerical example is used to illustrate the effectiveness of the proposed approach.}, booktitle={2014 European Control Conference (ECC)}, author={Yuan, C. Z. and Wu, F.}, year={2014}, pages={2334–2339} }
 @inproceedings{yuan_wu_2013, title={Robust control of switched linear systems via min of quadratics}, DOI={10.1115/dscc2013-3715}, abstractNote={In this paper, we will investigate the robust switching control problem for switched linear systems by using a class of composite quadratic functions, the min (of quadratics) function, to improve performance and enhance control design flexibility. The robustness is reflected in two prospectives including the ℋ ∞ performance and arbitrary switching of subsystems. A hysteresis min-switching strategy is employed to orchestrate the switching among a collection of controllers. The synthesis conditions for both state feedback and output feedback control problems are derived in terms of a set of linear matrix inequalities (LMIs) with linear search over scalar variables. The proposed min function based approach unifies the existing single Lyapunov function based method and multiple Lyapunov function based method in a general framework, and the derived LMI conditions cover the existing LMI conditions as special cases. Numerical studies are included to demonstrate the advantages of the proposed control design approach.}, booktitle={Proceedings of the ASME 2013 Dynamic Systems and Control Conference (DSCC2013), vol. 1}, author={Yuan, C. Z. and Wu, F.}, year={2013} }