Precise control of air–fuel ratio (AFR) is one of the most challenging tasks in lean-burn spark ignition engines control. The main problem arises because of the large time-varying delay in the engine operating envelope. In this study, a new sliding mode-based synthesis method is presented to control AFR in order to improve fuel economy and decrease the tailpipe emissions. The time-varying delay dynamics is first estimated by Padé approximation, which transfers the system into a system with parameter-varying non-minimum phase dynamics. Non-minimum phase characteristics restrict the application of conventional sliding mode control approach because of the unstable internal dynamics. The system dynamics is then rendered into the normal form to investigate the system unstable internal dynamics. A systematic approach is proposed to design a linear dynamic parameter-varying sliding manifold (LDPVSM) in order to stabilise the unstable internal dynamics according to the desired output tracking error dynamics. Additionally, the proposed LDPVSM provides the system with robustness against unmatched perturbation. The method that can be easily implemented in practical settings exhibits the desired dynamics independent of the matched and unmatched disturbances. The results of applying the proposed method to experimental data demonstrate the closed-loop system stability and a superior performance against time-varying delay, canister purge disturbances and measurement noise.

This study investigates the problem of sliding mode control for a class of stochastic Markovian jumping systems with partially known transition rate. A key feature in this work is to relax the requirement that all the elements in transition rate matrix are known, which does not always hold in actual applications. The finite set of modes is firstly divided into two parts, respectively, with known transitions rate and unknown one. Then, the sliding mode controller is designed to cope with the effect of partially known transition rate, in which two different robust terms are proposed, respectively, for the known and unknown modes. It is shown that both the reachability and asymptotic stability of sliding mode dynamics can be ensured by the present method, despite the partially known transition rate. Finally, numerical simulation results are given.

In this study, the authors present an overview of closed-loop subspace identification methods found in the recent literature. Since a significant number of algorithms has appeared over the last decade, the authors highlight some of the key algorithms that can be shown to have a common origin in autoregressive modelling. Many of the algorithms found in the literature are variants on the algorithms that are discussed here. In this study, the aim is to give a clear overview of some of the more successful methods presented throughout the last decade. Furthermore, the authors retrace these methods to a common origin and show how they differ. The methods are compared both on the basis of simulation examples and real data. Although the main focus in the literature has been on the identification of discrete-time models, identification of continuous-time models is also of practical interest. Hence, the authors also provide an overview of the continuous-time formulation of the identification framework.

Networked systems are often subject to environmental uncertainties and communication delays, which make timely and accurate information exchange among neighbours difficult or impossible. This study investigates the distributed consensus problem of dynamical networks of multi-agents in which each agent can only obtain noisy and delayed measurements of the states of its neighbours. The authors consider consensus protocols that take into account both the noisy measurements and the communication time delays, and introduce the notions of almost sure average-consensus and pth moment average-consensus. Using a convergence theorem for continuous-time semimartingales and moment inequality techniques for stochastic delay differential equations, the authors establish sufficient conditions for both almost sure and moment average-consensus. These results naturally generalise to networks with arbitrary and Markovian switching topologies. The consensus protocol considered here can be applied to networks with arbitrary bounded communication delays, which appears to the first consensus algorithm that is both average preserving and robust to arbitrarily sized delays. Numerical simulations are also provided to demonstrate the theoretical results.

This study deals with the problem of reliable precise tracking control for the networked control system with non-zero external inputs (NEIs). A new control scheme is developed by introducing an integral item in the control law and taking stochastic actuator failure (SAF) into account, by which a better steady tracking performances can be achieved. Based on Lyapunov theory, a reliable control design method that guarantees the network-based tracking control systems with zero steady-state error in the conditions of both NEIs and SAFs is designed. Simulation results demonstrate the effectiveness of the developed controller design scheme.

Motivated by tracking a manoeuvring target in electronic counter environments, the authors present the problem of joint estimation and identification of a class of discrete-time stochastic systems with unknown inputs in both the plant and sensors. Based on the expectation-maximum criterion, the joint optimisation scheme of state estimation, parameter identification and iteration terminate decision were derived. A numerical example of tracking a manoeuvring target accompanied range gate pull-off is utilised to verify the proposed scheme.

This study addresses the global pinning synchronisation of directed networks with Lorenz-type node dynamics. By using tools from M-matrix theory and Lyapunov stability theory, the interesting issues of what kind of nodes should be pinned and how large the control strength between neighbouring nodes should be selected for achieving global synchronisation in both fixed and switching networks are clearly addressed. It is theoretically shown that global pinning synchronisation of an arbitrarily given fixed network can be achieved if the network topology contains a directed spanning tree and the coupling strength is larger than a derived critical value depending both on the node dynamics and the network topology. By suitably constructing multiple Lyapunov functions, it is further proved that global pinning synchronisation in switching networks with a suitable coupling strength can be guaranteed if each possible network topology contains a directed spanning tree and the dwell time of switching is less than a positive threshold. Numerical examples are finally given for illustration.

In this study, a robust current switching control of converters is proposed. It is proved that the controller is able to guarantee global current regulation, as well as the maximum voltage and current ripple, simultaneously. Such features make it ideal for implementing power-management strategies and to be used along fuel cells. The control scheme is shown to be robust against model uncertainty and since it is based on the piece-continuous model instead of average models, it is suitable for operation under a wide range of conditions. Moreover, its complexity does not increase with the number of cells. Experimental evidence of the advantages and features of the proposed control is presented in a two-cell boost converter.

The design of quantised dynamic output feedback for decentralised ℋ_∞ control systems is considered with multi-input and multi-output. It is assumed that a decentralised dynamic output feedback has been designed for a decentralised continuous-time LTI system, so that the closed-loop system is stable and a desired ℋ_∞ disturbance attenuation level is achieved, and that each channel’s measurement outputs are quantised before they are passed to the local controller. We propose a local-output-dependent strategy for updating the quantisers’ parameters, so that the overall closed-loop system is asymptotically stable and achieves the same ℋ_∞ disturbance attenuation level. Both the pre-designed controllers and the quantisers’ parameters are constructed in a decentralised manner, depending on local measurement outputs.

This study considers the control problem for a class of non-linear singularly perturbed systems (SPSs) subject to actuator saturation. A sufficient condition for the existence of state-feedback controllers to achieve a prescribed stability bound is proposed and the corresponding basin of attraction is estimated. Then a convex optimisation problem is formulated, by which an optimal controller can be obtained to achieve a prescribed stability bound and simultaneously maximise the estimate of the basin of attraction of the SPSs for any allowable singular perturbation parameter. Furthermore, a stability condition is established, which improves the existing stability bound analysis methods for a class of non-linear SPSs. Finally, examples are given to show the advantages and effectiveness of the obtained results.

The aim of this study is to find an improved dwell time that guarantees the stability of switched systems with heterogeneous constant time-delays. Piecewise Lyapunov–Krasovkii functionals are used for each candidate system to investigate the stability of the switched time-delayed system. Under the assumption that each candidate system is stable for small delay values, a sufficient condition for dwell-time that guarantees the asymptotic stability is derived. Numerical examples are given to compare the results with the previously obtained dwell-time bounds.

This article studies spacecraft rendezvous with the target spacecraft in an arbitrary elliptical orbit. Based on the linearised Tschauner–Hempel equations, state-dependent Riccati differential equation (RDE)-based approaches are proposed to solve the problem. An observer-based output feedback controller is established. To implement the proposed controller, only some forward-type RDEs need to be integrated online, indicating that the controllers can be implemented online as long as some positive-definite initial conditions are given. Moreover, it is shown analytically that the closed-loop system under the proposed feedback controller is exponentially asymptotically stable. Numerical examples show the effectiveness of the proposed approach.

This study investigates the problem of designing a sampled-data output feedback controller to globally stabilise a class of upper-triangular systems with delay in the input. By using a linear observer, a linear dynamic sampled-data output feedback control law is explicitly constructed. To dominate the unknown non-linear perturbing terms and handle the case with a larger input delay, a tunable scaling gain is introduced to the controller by using a coordinates change. With the help of an appropriate Lyapunov–Krasoveskii functional and the technique of sampled-data output-feedback domination, it is shown that the considered upper-triangular non-linear system with any bounded input delay can be globally stabilised by the proposed controller with appropriate gains. Finally, an example is given to verify the efficiency of the proposed method.