Control of systems that have had their passive input–output map partially violated is the motivation of this study. The hybrid passivity/finite-gain systems framework is specifically well suited to systems that have experienced a passivity violation. The focus of this study is the extension and application of the hybrid passivity/finite-gain systems framework to a multi-input multi-output (MIMO) control problem. Calculation of the hybrid passivity/finite-gain parameters in a linear time-invariant (LTI) MIMO context is considered. Additionally, we show that a set of hybrid very strictly passive/finite-gain (VSP/finite-gain) controllers gain-scheduled in a particular way also possesses hybrid VSP/finite-gain properties. To synthesise hybrid VSP/finite-gain controllers a frequency-weighted optimal control scheme is used to parameterise controllers that are then constrained and optimised within a numerical optimisation framework. The theoretical contributions of this work are validated experimentally using a two-link flexible manipulator apparatus. Results highlight the utility of the hybrid passivity/finite-gain framework, the scheduling scheme and controller design method.

A reset controller is a controller that operates most of the time as a linear system, except when some condition holds. The typical reset condition is the zero crossing of the tracking error signal, e(t) = 0. At this moment, the controller performs a zero resetting action on its state. It has been shown that reset control is able to overcome fundamental linear limitations. This article studies, within a frequency-domain framework, the generalisation of reset control systems based on including some anticipation on the reset condition.This has a favourable phase lead effect. The paper discusses different reset anticipations schemes, including multiple reset actions in the same period, computes Fourier harmonics and describing function of general reset controllers and shows explicitly the overcoming of frequency-domain limitations (Bode's gain–phase relation).

This study is concerned with the problem of dual communication channels sharing-based network-induced delay and packet dropout compensation for continuous-time networked control systems (NCSs). By introducing the dual communication channels sharing-based compensation method, a new closed-loop model for continuous-time NCSs, which can receive more than one control input during a control input updating time interval, is established. Based on the newly established model and a new Lyapunov functional, an effective controller design criterion is derived to optimise the H _∞ performance of the considered systems. Even for NCSs without considering network-induced delay and packet dropout compensation, the newly derived controller design method is also applicable. Two numerical examples are given to illustrate the merits and effectiveness of the proposed compensation method.

Controllers based on fractional order calculus are gaining more and more interests from the control community. This type of controllers may involve fractional integration, fractional differentiation and/or fractional systems in their structure or implementation. They have been introduced in the control applications in a continuous effort to enhance the system control quality performances and robustness. In this study, a new scheme of fractional order adaptive controller via high-gain output feedback for a class of linear, time-invariant, minimum phase and single input-single output systems of relative degree one is proposed. The basic idea of the new design is a further modification in the adaptive proportional control law by the introduction of a fractional integration besides of the regular one of the squared output of the system in the adaptation gain of the control strategy. An analytical stability proof of the feedback control system is presented. The control quality enhancement of the proposed control scheme compared with the classical one has been presented through the simulation results of an illustrative example.

This study proposes a multiple-input/multiple-output robust approach to the control of bioprocesses based on a cascaded-loop strategy. The internal loop is a classical input-to-output feedback linearising controller which is obtained from the nominal dynamics of the bioprocess. Then, the outer loop is designed based on the internal model principle to obtain zero steady-state tracking error (and disturbance rejection) for constant signals while ensuring the robust stability of the overall closed-loop system. In addition, a robust Luenberger-like observer is proposed to estimate unmeasured state variables for the feedback linearising control law. The approach is applied to the simultaneous control of biomass and substrate concentrations in a perfusion/chemostat bioreactor, where the simulation results demonstrate the effectiveness of the proposed control strategy.

This article studies the consensusability of multi-agent systems with general linear continuous-time dynamics. It is assumed that each agent can only obtain the information of other agents at sampling instants. Some sufficient and necessary conditions for consensusability in the case of state feedback are established, and it is shown that multi-agent systems with periodic sampling are consensusable if and only if the system associated with each agent is stabilisable and the topology graph has a spanning tree. Furthermore, some methods are provided to seek controller gain and sampling period which ensure consensus. Simulations are performed to validate the theoretical results.

This study is concerned with the problem of non-fragile H _∞ filtering for discrete-time non-linear systems in Takagi–Sugeno's form. Additive interval uncertainty that reflects imprecision in filter implementation because of finite word length effects is considered. Based on vertex theory and probabilistic robust approach, deterministic and randomised filtering algorithms are proposed, respectively. Compared with the deterministic algorithm, the randomised algorithm has acceptable computational complexity, especially for high-dimensional systems. Two examples are given to illustrate the effectiveness of the proposed algorithms.

This study is concerned with the problem of fault detection (FD) for networked control systems with discrete and infinite distributed delays subject to random packet losses and non-linear perturbation. Both sensor-to-controller and controller-to-actuator packet losses are modelled as two different mutually independent Bernoulli distributed white sequences with known conditional probability distributions. By utilising an observer-based fault detection filter (FDF) as a residual generator, the FD for networked non-linear systems with mixed delays and packet losses is formulated as an H _∞ model-matching problem. Attention is focused on designing the FDF in the closed-loop system setup such that the estimation error between the residuals and filtered faults is made as small as possible and at the same time the closed-loop networked non-linear system is exponentially stable in the mean-square sense. To show the superiority and effectiveness of this work, two numerical examples are presented.

This study presents a novel hybrid adaptive feedforward cancellation (AFC) methodology in particular for time-varying discrete systems with stochastic periodic disturbance. The proposed hybrid AFC framework is composed of conventional AFC modules and auxiliary PID control variables. The former is traditionally constructed with sinusoidal functions and parameters of the AFC system, and the latter is added for compensating perturbation because of non-stationary random disturbance in practice. The authors derive an estimation algorithm of parameters in the hybrid AFC system by using a gradient descent based optimisation method. In addition, a theoretical investigation is conducted for verifying convergence property of the parameter estimation by means of a well-known Lyapunov stability theory. Lastly, the authors achieve numerical simulation to prove reliability and superiority of the proposed AFC algorithm by comparing to a conventional AFC approach.

This study presents distributed event-based control strategies for a networked dynamical system consisting of N linear time-invariant interconnected subsystems. Each subsystem broadcasts its state over the network according to certain triggering rules that only depend on local information. The system can converge asymptotically to the equilibrium point under the proposed control design, and the existence of a lower bound for the broadcasting period is guaranteed. A novel model-based approach is derived to reduce the communication between the agents. Simulation results show the effectiveness of the proposed approaches and illustrate the theoretical results.

This study addresses the distributed average set-membership filtering of spatially varying processes using sensor networks. The system under consideration contains sensor saturation in the presence of unknown-but-bounded process and measurement noise in the sensor network. The so-called distributed average set-membership filtering is defined to quantify bounded consensus regarding the estimation error. A sufficient condition for distributed average set-membership filtering parameter design is established in terms of a set of time-varying linear matrix inequalities. A recursive algorithm is developed for computing the estimator, controller gains and the ellipsoid that guarantees to contain the true state. Simulation results are provided to demonstrate the effectiveness of the proposed method.

This study addresses two major single-input single-output control problems involving both feedback and feedforward actions: (i) the model matching in reference tracking and (ii) the rejection of measurable disturbances. Its aim is to overcome the limitations of inversion-based feedforward design methods when system uncertainty is considered, and to find a control engineering solution based on the quantitative feedback theory (QFT). The proposed methodology leads to minimum cost of feedback by limiting the feedback action to the strictly necessary amount that enables the use of a feedforward controller. Although the model matching problem had drawn some attention of the QFT community in the last few years, the measurable disturbance rejection problem remained unaddressed. This study provides a novel solution for both of them in which the need for feedback is linked to the existence of a common feedforward solution for all plants within the model uncertainty. This work also deals with the generation of the corresponding quadratic inequalities and new QFT bounds for the mentioned feedback demand. A practical and well-known benchmark example illustrates the main details and advantages of the new methodology.

The present work is concerned with the recursive estimation of the uncertainty polytope in a robust model predictive control (RMPC) framework. For this purpose, the unknown but bounded error method is employed to update the uncertainty polytope on the basis of sensor measurements at each sampling period. The recursive feasibility and asymptotic stability properties of the proposed approach are demonstrated as an extension of previous results concerning the RMPC formulation. For illustration, a simulated example involving an angular positioning system is presented. The results show that the proposed scheme provides a performance improvement, as indicated by the resulting cost function values.

This study is devoted to controlling a class of non-linear systems in the presence of packet transmission delays, packet losses and sampling-related phenomena over a communication network. To increase the applicability of the Takagi–Sugeno (T–S) fuzzy approach for non-linear networked control systems, this study sets the premise variables in T–S fuzzy plant and control to be asynchronous and then introduces a useful relaxation technique in a better position to handle the asynchronous problem. Moreover, this study provides a method capable of exploiting fully the induced delay term d(t) from the derivation of robust stabilisation condition.