This study is concerned with the event-based security control problem for a class of discrete-time stochastic systems with multiplicative noises subject to both randomly occurring denial-of-service ...(DoS) attacks and randomly occurring deception attacks. An event-triggered mechanism is adopted with hope to reduce the communication burden, where the measurement signal is transmitted only when a certain triggering condition is violated. A novel attack model is proposed to reflect the randomly occurring behaviours of the DoS attacks as well as the deception attacks within a unified framework via two sets of Bernoulli distributed white sequences with known conditional probabilities. A new concept of mean-square security domain is put forward to quantify the security degree. The authors aim to design an output feedback controller such that the closed-loop system achieves the desired security. By using the stochastic analysis techniques, some sufficient conditions are established to guarantee the desired security requirement and the control gain is obtained by solving some linear matrix inequalities with non-linear constraints. A simulation example is utilised to illustrate the usefulness of the proposed controller design scheme.
In this study, an adaptive fractional-order terminal sliding mode controller is proposed for controlling robot manipulators with uncertainties and external disturbances. An adaptive tuning method is ...utilised to deal with uncertainties which upper bounds are unknown in practical cases. Fast convergence is achieved using non-singular fast terminal sliding mode control. Also, fractional-order controller is used to improve tracking performance of controller. After proposing a new stable fractional-order non-singular and non-linear switching manifold, a sliding mode control law is designed. The stability of the closed-loop system is proved by Lyapunov stability theorem. Simulation results demonstrate the effectiveness and high-precision tracking performance of this controller in comparison with integer-order terminal sliding mode controllers.
The design of output constrained control system for unmanned aerial vehicles deployed in confined areas is an important issue in practice and not taken into account in many autopilot systems. In this ...study, the authors address a neural networks-based adaptive trajectory tracking control algorithm for multi-rotors systems in the presence of various uncertainties in their dynamics. Given any sufficient smooth and bounded reference trajectory input, the proposed algorithm achieves that (i) the system output (Euclidean position) tracking error converges to a neighbourhood of zero and furthermore (ii) the system output remains uniformly in a prescribed set. Instead of element-wise estimation, a norm estimation approach of unknown weight vectors is incorporated into the control system design to relieve the onboard computation burden. The convergence property of the closed-loop system subject to output constraint is analysed via a symmetric barrier Lyapunov function augmented with several quadratic terms. Simulation results are demonstrated on a quadrotor model to validate the effectiveness of the proposed algorithm.
This studies an adaptive control problem of pure-feedback non-linear systems with full state constraints. The mean value theorem is employed to deal with unknown non-linearities. A novel backstepping ...design is constructed via barrier Lyapunov function (BLF) combined with dynamic surface control (DSC). The BLF guarantees the full state constraints are not violated and all the closed-loop signals remain bounded. DSC solves the problems of restrictions on high order differentiability of stabilising functions and avoiding the complexity that arises due to the explosion of terms in backstepping design. It is shown that all the signals in the closed-loop system are ultimately bounded and the tracking error converges to an adjustable neighbourhood of the origin while the full state constraints remain unchanged. The performance of the BLF-based DSC is illustrated with two simulation examples.
This work strives for the issue of generalised dissipative asynchronous output feedback control for Markov jump repeated scalar non-linear systems with time-varying delay. The objective is to design ...an asynchronous output feedback controller, which ensures that the closed-loop system is generalised stochastically dissipative. Meanwhile, such an asynchronous controller covers not only the asynchronous controller but also the mode-independent one. By means of a stochastic analysis technique and a modified matrix decoupling method, sufficient conditions are given for deriving the desired controller. At length, an illustrative example is provided to demonstrate the availability of the presented approach.
An improved prescribed performance control using a backstepping technique and adaptive fuzzy is proposed for a strict feedback nonlinear dynamic system. A new virtual variable was defined to generate ...the virtual control that forces the tracking errors to fall within prescribed boundaries, and an adaptive fuzzy system was used to obtain required approximation performances. A strict feedback controller and adaptive laws for estimating the unknown non-linear function were designed to avoid a singularity problem and calculation of the explosive number of terms generated by the error transformations of conventional error constraint method and the recursive steps of traditional backstepping control. Lyapunov stability analysis confirmed the boundedness and convergence of the closed-loop system. The prescribed error constraint performance of the proposed control scheme was validated by applying it to control the position of a second-order non-linear system and a robot manipulator.
This study deals with the problem of robust stabilisation for non-linear time-delay semi-Markovian jump systems via sliding mode control (SMC). Such a switching is governed by a semi-Markovian ...process which is time-varying and dependent on the sojourn-time h. The time delay is considered as time-varying and meets the requirements of the upper and lower bounds. By introducing free-connection weighting matrix method and Lyapunov functional, sufficient conditions for the resulting sliding mode dynamics in the form of linear matrix inequalities are derived to guarantee the closed-loop system robustly stochastically stable for all admissible uncertainties and non-linear perturbations. Then, an SMC law is synthesised to drive the system trajectories onto the predefined switching surface in a finite time. Finally, an example illustrates the validity of the obtained results.
In this study, the authors are concerned with the active vibration control of a flexible string system with input backlash. For vibration suppression, active control is applied at the right boundary ...of the flexible string. To deal with the input backlash, a novel ‘disturbance-like’ term is proposed in the control design. A physically motivated Lyapunov function is employed to design boundary control law to ensure the vibration suppression and guarantee the stability of the closed-loop system. Numerical simulations illustrate the effectiveness of the proposed control method.
The problem of adaptive practical finite-time control is considered for a class of single-input and single-output non-linear systems, in which the system non-linear functions are assumed to be ...unknown. By combining adaptive fuzzy control approach with the backstepping technology, a backstepping-based adaptive fuzzy finite-time control scheme is proposed. In the control design procedure, fuzzy logic systems are employed to identify the non-linear uncertainties. The stability analysis of the adaptive closed-loop systems is proposed based on the finite-time Lyapunov stability theory. The proposed adaptive fuzzy controller guarantees that all the closed signals are semi-global practical finite-time stability while the tracking error converges to a small neighbourhood of the origin. Finally, simulation results are presented to validate the effectiveness of our results.
Aim
To investigate real‐world glycaemic outcomes and goals achieved by users of the MiniMed 780G advanced hybrid closed loop (AHCL) system aged younger and older than 15 years with type 1 diabetes ...(T1D).
Materials and Methods
Data uploaded by MiniMed 780G system users from 27 August 2020 to 22 July 2021 were aggregated and retrospectively analysed based on self‐reported age (≤15 years and >15 years) for three cohorts: (a) post‐AHCL initiation, (b) 6‐month longitudinal post‐AHCL initiation and (c) pre‐ versus post‐AHCL initiation. Analyses included mean percentage of time spent in AHCL and at sensor glucose ranges, insulin delivered and the proportion of users achieving recommended glucose management indicator (GMI < 7.0%) and time in target range (TIR 70‐180 mg/dl > 70%) goals.
Results
Users aged 15 years or younger (N = 3211) achieved a GMI of 6.8% ± 0.3% and TIR of 73.9% ± 8.7%, while spending 92.7% of time in AHCL. Users aged older than 15 years (N = 8874) achieved a GMI of 6.8% ± 0.4% and TIR of 76.5% ± 9.4% with 92.3% of time in AHCL. Time spent at less than 70 mg/dl was within the recommended target of less than 4% (3.2% and 2.3%, respectively). Similar outcomes were observed for each group (N = 790 and N = 1642, respectively) in the first month following AHCL initiation, and were sustained over the 6‐month observation period.
Conclusions
This real‐world analysis shows that more than 75% of users with T1D aged 15 years or younger using the MiniMed 780G system achieved international consensus‐recommended glycaemic control, mirroring the achievements of the population aged older than 15 years.
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