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In a closed-loop supply chain, the reuse of spare parts from returned systems is a recovery process referred to as spare parts harvesting. The unpredictability of the parts supply capacity from returned systems is a challenge in healthcare industry as product returns depend on several factors and regulatory and legal requirements must be respected. The focus of this paper is to provide a forecasting method of harvested parts supply capacity in healthcare industry that combines statistical methods with field information and business knowledge to provide an informed forecast. We propose a dynamic forecasting process that gets updated monthly employing TSB-Croston, 12-month moving average, ARIMA, ARIMA with seasonality, and a new business knowledge based model. A prediction method of the inventory state changes is introduced. The forecasters judgment is transformed into validation rules for an automatic forecast adjustment. This method is evaluated on more than 1400 time series with intermittent behaviour representing General Electric Healthcare spare parts harvesting history. We evaluate the performance of our method compared to each tested model using a modified MAPE, MAE, MSE, and RMSE. By means of the designed method, the forecast performance is improved compared to all tested models. [ABSTRACT FROM AUTHOR]

In this article, we study an event-triggered asymptotic tracking control problem for a class of networked nonlinear systems with unmeasurable states. In contrast to the majority of existing event-triggered control results, where only the input or output signal is triggered, the design problem of a dual-channel event-triggered mechanism is studied to achieve a more comprehensive saving of communication resources. Subsequently, in order to reconstruct system states, a continuous-discrete observer that can achieve asymptotic convergence of estimation errors is constructed based on event-triggered output. Then, an event-triggered asymptotic tracking control scheme is introduced through Levant differentiators, filtered error compensation signals, and the backstepping technique. The Levant differentiators not only address the challenge of computational complexity explosion but also effectively resolve the problem of controller segmentation continuity. The control scheme has been proven to maintain all signals in the closed-loop system bounded and achieve zero tracking error as time approaches infinity. Subsequently, numerical simulations are conducted to verify the effectiveness of the proposed approach. [ABSTRACT FROM AUTHOR]

In this article, an adaptive event-triggered bounded control strategy is proposed for a class of high-order uncertain switched nonlinear systems with full-state time-varying constraints under average dwell time switching rule. In order to achieve the boundedness of the control signal, the projection operator is introduced. At the same time, the high-order log-type time-varying barrier Lyapunov function method is chosen to ensure that the desired output and states of the systems do not violate the relevant constraints. In addition, the improved event-triggered control strategy effectively reduces the transmission burden and saves the resource cost. The stability analysis shows that the proposed scheme achieves the ultimate boundedness of all signals in the closed-loop systems and the states of the systems do not violate the corresponding constraints. It should be noted that the proposed controller has a known bound and this bound can be ensured by the rectification of the feedback control gain. Finally, the simulation results verify the effectiveness of the control method. [ABSTRACT FROM AUTHOR]

This study explores the problem of finite-time resilient control for periodic piecewise polynomial time-varying systems in the face of parameter uncertainties, time-varying state delays and external disturbances. Particularly, the considered system is characterized by dividing the fundamental period of periodic systems into numerous subintervals, each of which can be expressed by using matrix polynomial functions. The foremost intention of this work is to lay out a resilient controller such that the resulting closed-loop system is finite-time bounded and satisfies a mixed H ∞ and passivity performance index. Furthermore, by constructing a periodic piecewise time-varying Lyapunov–Krasovskii functional, a delay-dependent sufficient condition is established in line with Wiritinger's inequality and matrix polynomial lemma to guarantee the needed outcomes of the system under study. Following this, the gain matrix of the devised controller can be calculated by solving the established constraints. As a final step, we conclude with a numerical example that validates the potential and importance of the theoretical discoveries and the developed control scheme. [ABSTRACT FROM AUTHOR]

This paper deals with the problem of event-triggered control (ETC) for vertical take-off and landing (VTOL) aircraft systems under actuator saturation. By introducing the VTOL system with saturated actuators, a composite quadratic Lyapunov function (CQLF) approach is first proposed to describe the problem of the event triggering mechanism. The proposed transfer mechanism not only further saves communication resources, but also further suppresses the conservatism of the attraction domain estimation. Then, sufficient conditions are established via linear matrix inequality (LMI) by incorporating new event triggering mechanism condition and prescribed passive performance metrics under the closed-loop system that is asymptotically stable and strictly passive, respectively. Finally, the method proposed in this paper can effectively reduce the number of triggers and expand the domain of attraction. The validity and feasibility of the obtained results are demonstrated by two example simulations. [ABSTRACT FROM AUTHOR]

Due to the influence of material characteristics and engineering imperfections, the residual magnetic fields including static and dynamic field in a lightweight magnetically shielded room (MSR) present non-uniform distribution characteristic. To effectively reduce the residual static field, a non-uniform field compensation method based on distributed coils has been proposed. This method takes the L2-norm of the magnetic field at the target array points as the objective function, to optimize the compensation current in each of the designed distributed coils, achieving non-uniform field compensation. To further achieve compensation for non-uniform residual dynamic field, a closed-loop control system containing a voltage divider and multi-channel amplifiers is designed in this paper. Additionally, the coil constant of the distributed differential coils and the initial magnetic field distribution vector for dynamic compensation are redefined. In conjunction with a PI controller, dynamic compensation is achieved using a single optically pumped magnetometer as the feedback component. The experimental results indicate that the average dynamic field decreased from 376.75 pT to 27.80 pT over the central volume of (300 mm)3 in MSR, achieving a near-zero magnetic environment. This method has universal applicability for compensating non-uniform residual field under different working conditions. [ABSTRACT FROM AUTHOR]

Aims: The study was aimed at assessing the role of the MiniMed780G system of glycemic control before, during, and after Ramadan among people with Type 1 diabetes (PwT1D). Methods: This is a single‐center retrospective analysis of MiniMed780G system users aged 14 years and above whose glycemic profiles were collected from February 21 to May 20, 2023, which corresponds to the Hijri months of Sha'ban, Ramadan, and Shawwal 1444/1445. Data was collected, processed, and analyzed in the framework of the Medtronic Galaxy service of the One Hospital Clinical Service (OHCS) program in Dallah Hospital, Riyadh, Saudi Arabia. Data from 43 PwT1D (24 females, mean age 30 ± 11 years with 14 ± 8 years from diabetes onset) using the MiniMed780G system were collected. Results: Overall, the 3‐month (Sha'ban, Ramadan, and Shawwal) mean sensor glucose (SG), time in range (TIR) (70–180 mg/dL), time below range (TBR) (54–69 mg/dL and < 54 mg/dL), time above range (TAR) (180–250 mg/dL and > 250 mg/dL), and glucose management indicator (GMI) showed no statistical differences within the three periods. No differences in insulin total daily dose have been detected, and no diabetic ketoacidosis (DKA) or severe hypoglycemia events occurred. Conclusion: The use of the MiniMed780G system is safe with favorable glycemic outcomes across nonfasting and fasting months. [ABSTRACT FROM AUTHOR]

Exponential stabilisation is undoubtedly an essential property to study for any control system. This property is often difficult to establish for nonlinear distributed systems and even more difficult if the state of such a system is subject to a time-delay. In this context, this paper is devoted to the study of the well-posedness and exponential stabilisation problems for the one-dimensional delayed Fisher's partial differential equation (PDE) posed in a bounded interval, with homogeneous Dirichlet condition at the left boundary and controlled at the right boundary by Dirichlet condition. Based on the infinite dimensional backstepping method for the linear and undelayed corresponding case, a feedback law is built. Under this feedback, we prove that the closed-loop system is well-posed in $ L^2(0,1) $ L 2 (0 , 1) and locally exponentially stable in the topology of the $ L^2(0,1) $ L 2 (0 , 1) -norm by the use of semigroup theory relating to differential difference equations and Lyapunov–Razumikhin analysis, respectively. A numerical example that reflects the effectiveness of the proposed approach is given. [ABSTRACT FROM AUTHOR]

A novel non-backstepping output feedback control approach, called as the dual-gain scaling approach, is proposed by combining the extended Lyapunov matrix inequalities with dual-domination idea. This approach provides partially decentralised adaptive output feedback controllers with three event-triggered mechanisms to achieve the global practical tracking of a family of uncertain large-scale nonlinear systems subject to unknown control coefficients and strongly interconnected nonlinearities with output-polynomial growth rate. The dual gains are embedded in the observers and controllers, which can effectively compensate for time-varying control coefficients and unknown constant growth rate multiplied by output-polynomial function. Three different threshold schemes including fixed threshold, relative threshold and time-varying threshold are introduced to save communication resources. The stability analysis shows that the solutions of the closed-loop system are globally uniformly bounded and the tracking error converges to a preset compact set after a finite time; also, there will be no zeno behaviour in the closed-loop response. [ABSTRACT FROM AUTHOR]

This paper studies the problem of global output-feedback tracking control for a class of uncertain nonlinear systems. The system studied in this paper has unknown time-varying control coefficients and unknown reference signal. Notably, the nonlinearities of the system are bounded by the lower triangular linear unmeasured states multiplying the unknown constant, the polynomial-of-output and the polynomial-of-input growth rates, which indicates the presence of serious uncertainties. Motivated by the closely related works, by combining the ideas of universal control and deadzone with backstepping technique, this paper presents a new adaptive tracking control scheme based on two dynamic high-gains in the new forms. The proposed control scheme ensures that the tracking error converges to a specified arbitrarily small interval range after a finite time while the state of the resulting closed-loop system is globally bounded. Finally, the effectiveness of the control scheme is verified by an illustrative example. [ABSTRACT FROM AUTHOR]

For the nonlinear systems with input delay, an adaptive fixed-time tracking control strategy based on multi-dimensional Taylor network (MTN) is proposed for the first time. First, to address the main challenge brought by input delay, an auxiliary system is constructed, which transforms the input delay systems into non-delay systems. Second, the MTNs are introduced into the backstepping design process, which reduce the design difficulty by approximating unknown nonlinear functions. Thus, a control scheme subject to low complexity is obtained. Third, aside from ensuring that the tracking error converges within a small neighbourhood of the origin within a fixed-time, the designed control scheme not only makes all signals in the closed-loop system remain bounded, but also avoids the problem of finite-time control relying on initial state. Finally, three simulations are given to prove the feasibility and superiority of the proposed control scheme. [ABSTRACT FROM AUTHOR]

The paper studied the finite-time semi-global stabilisation problems for a class of nonlinear systems with a novel polynomial growth condition. By using some key properties of a class of parametric Lyapunov equations and constructing time-varying Lyapunov-like functions, two time-varying high-gain controllers, where scalar time-varying functions are generated by differential equations, are designed. Both state feedback and observer-based output feedback are considered. It is shown that the proposed methods can achieve finite-time semi-global stabilisation for closed-loop systems and the controls are bound. Two numerical examples verify the effectiveness of the established results. [ABSTRACT FROM AUTHOR]

This paper considers the stability of the one-dimensional parabolic system, where one end changes over time and the other is the control end with the external disturbance. Firstly, by the boundary immobilisation method, the displacement change of the system boundary is transferred into the equation so that the original system is transformed into a system with fixed boundaries. Secondly, by combining the backstepping transformation and the sliding mode control method, the feedback control is proposed to compensate the instability of the system itself and reject the matched disturbance. Then, the resulting closed-loop system will be in the form of $ \mathcal{A}+ \mathcal{B}(\tau)+ \mathcal{C} D(\tau) $ A + B (τ) + C D (τ) , where $ \mathcal{A} $ A generates a $ C_0 $ C 0 semigroup, $ \mathcal{B}(\tau) $ B (τ) and $ \mathcal{C} $ C are bounded and unbounded operators respectively, and $ D(\tau) $ D (τ) is the external input. The existence of the generalised solution to the closed-loop system is proved by using the eigenfunction expansion of the system solution. By the Lyapunov method, the closed-loop system is shown to be exponentially stable. Finally, some numerical simulations are presented to illustrate the effectiveness of the proposed controller. [ABSTRACT FROM AUTHOR]

This paper is concerned with the cooperative control issue of virtually coupled high-speed trains (VCHSTs) under an adaptive dynamic programming (ADP) framework, where a dynamic event-triggered mechanism is employed to govern the communication between sensors and observers. A learning-based observer, equipped with a robust term, is exploited to mitigate the effect of the unknown nonlinear dynamics of the VCHSTs. Furthermore, to realise the distributed design, an auxiliary control signal is employed to simply the closed-loop system and also integrated into the cost function to handle the coupled nature of the investigated systems. The Hamilton–Jacobi–Bellman (HJB) equation is approximated by actor and critic networks in the ADP framework, which iteratively acquires the desired control strategy. By resorting to the common Lyapunov stability, some sufficient conditions are derived to achieve the desired observer gain and learning rates of NNs. Ultimately, the control scheme's efficiency is confirmed by simulations of VCHSTs. [ABSTRACT FROM AUTHOR]

Research on initial errors and constraint restrictions is one of the main research directions in the field of control of uncertain robotic systems. An adaptive iterative learning control (AILC) method based on radial basis function (RBF) neural network is proposed to address the trajectory tracking problem of the long-stroke hybrid robot system with random initial errors and full state constraints. The RBF neural network is used to approximate the unknown nonlinear terms, and the network weights are updated using an iterative learning law that incorporates a projection mechanism. Additionally, a robust learning strategy is used to compensate for both the approximation error of the neural network and the external disturbances that vary with each iteration. To relax the requirement of traditional iterative learning control (ILC) for identical initial condition, an equivalent error function is constructed based on the time-varying boundary layer. The tangent-type barrier Lyapunov function (BLF) is designed to ensure that the joint position and speed of the robot system are bounded within a predetermined range. Through stability analysis based on barrier composite energy function (BCEF), it can be proved that the boundedness of all signals in the closed-loop system and the tracking error of the robot system will converge to an adjustable residual set asymptotically. Finally, through simulation experiments conducted on the MATLAB platform, the results demonstrate that the method overcomes the random initial errors of the system effectively, ensures that the system satisfies the full-state constraints, and realizes high-precision trajectory tracking. [ABSTRACT FROM AUTHOR]

Overhead cranes play a pivotal role in various industrial applications. This paper presents two methodologies for suppressing the payload's swing and completing the accurate positioning. The original crane model is initially transformed into a chained form. Two nonlinear controllers are devised to regulate the trolley's position and achieve the payload's anti-swing control. The first approach utilizes backstepping, extended state observer, and filter technique to effectively estimate system state and disturbance and make the closed-loop system uniformly ultimately bounded. In contrast, the second method involves sliding mode control and finite-time disturbance observer to ensure the finite-time convergence of the resulting closed-loop system and the accurate disturbance estimation. Finally, simulation results are provided to validate the effectiveness of the proposed methods. [ABSTRACT FROM AUTHOR]

Background and Objectives: The two-axis inertially stabilized platforms (ISPs) face various challenges such as system nonlinearity, parameter fluctuations, and disturbances which makes the design process more complex. To address these challenges effectively, the main objective of this paper is to realize the stabilization of ISPs by presenting a new robust model-free control scheme. Methods: In this study, a robust adaptive fuzzy control approach is proposed for two-axis ISPs. The proposed approach leverages the backstepping method as its foundational design mechanism, employing fuzzy systems to approximate unknown terms within the control framework. Furthermore, the control architecture incorporates a model-free disturbance observer, enhancing the system's robustness and performance. Additionally, novel adaptive rules are devised, and the uniform ultimate boundedness stability of the closed-loop system is rigorously validated using the Lyapunov theorem. Results: Using MATLAB/Simulink software, simulation results are obtained for the proposed control system and its performance is assessed in comparison with related research works across two scenarios. In the first scenario, where both the desired and initial attitude angles are set to zero, the proposed method demonstrates a substantial mean squared error (MSE) reduction: 96.2% for pitch and 86.7% for yaw compared to the backstepping method, and reductions of 75% for pitch and 33.3% for yaw compared to the backstepping sliding mode control. In the second scenario, which involves a 10-degree step input, similar improvements are observed alongside superior performance in terms of reduced overshoot and settling time. Specifically, the proposed method achieves a settling time for the pitch gimbal 56.6% faster than the backstepping method and 58% faster for the yaw gimbal. Moreover, the overshoot for the pitch angle is reduced by 53.5% compared to backstepping and 35.5% compared to backstepping sliding mode control, while for the yaw angle, reductions of 43.6% and 37.6% are achieved, respectively. Conclusion: Through comprehensive simulation studies, the efficacy of the proposed algorithm is demonstrated, showcasing its superior performance compared to conventional control methods. Specifically, the proposed method exhibits notable improvements in reducing maximum deviation from desired angles, mean squared errors, settling time, and overshoot, outperforming both backstepping and backstepping sliding mode control methods. [ABSTRACT FROM AUTHOR]

This study delves into an event-triggered hierarchical learning control framework for air-breathing hypersonic vehicles subject to practically constrained actuators. The hierarchical learning mechanism is adeptly integrated into both the control and allocation layers. In the control layer, an emotional deterministic learning control methodology is proposed with predefined-time disturbance observers and filters to attain predefined-time convergence of system tracking and learning, while compensating for lumped disturbances stemming from allocation errors and external disturbances. An intelligent triggered allocation approach is implemented in the allocation layer to distribute the desired control effect to the actuator with fast and low-complexity allocation considering practical actuator characteristics. The proposed control scheme ensures that all signals in the closed-loop system converge to a residual set in close proximity to the origin within a predefined time, whose time constant can be adjusted as desired by the designer. Furthermore, as the system is governed by the event-triggered mechanism, the communication burden can be considerably reduced. The effectiveness of the proposed controller is demonstrated through both theoretical proof and numerical simulations. [ABSTRACT FROM AUTHOR]

In this paper, the problem of real-time reachable set control for fuzzy singularly perturbed systems with time-varying delays and disturbances is investigated. First, by combining the Lyapunov stability theory with the free-weighting matrix approach and linear matrix inequality technique, the real-time reachable set control problem related to fuzzy singularly perturbed systems is given adequate conditions. Subsequently, the matrix decoupling approach is applied to calculate the controller gains. Moreover, the stability boundary $ {\bar \eta } $ η¯ can be established using the dichotomy technique by utilizing the adequate criteria in the following theorems. Finally, two examples are offered to illustrate the effectiveness of the strategy. [ABSTRACT FROM AUTHOR]

The baroreflex is one of the most important control mechanisms in the human cardiovascular system. This work utilises a closed-loop in silico model of baroreflex regulation, coupled to pulsatile mechanical models with (i) one heart chamber and 36-parameters and (ii) four chambers and 51 parameters. We perform the first global sensitivity analysis of these closed-loop systems which considers both cardiovascular and baroreflex parameters, and compare the models with their respective unregulated equivalents. Results show the reduced influence of regulated parameters compared to unregulated equivalents and that, in the physiological resting state, model outputs (pressures, heart rate, cardiac output etc.) are most sensitive to parasympathetic arc parameters. This work provides insight into the effects of regulation and model input parameter influence on clinical metrics, and constitutes a first step to understanding the role of regulation in models for personalised healthcare. Author summary: In the era of personalised healthcare, there is a growing need to develop computational models that accurately represent human physiology. Here, we examine two models of the human circulatory system, incorporating the effects of baroreflex regulation— a key neural homeostatic mechanism responsible for controlling blood pressure during rest and exercise on short timescales. We investigate the impact of including baroreflex regulation on clinically significant metrics such as cardiac output. Due to the model's complexity and a large number of parameters, quantifying the effects of regulation in a closed-loop operation was previously deemed infeasible, but by utilising an efficient in silico encapsulation and high-performance computing we are able, here, to quantify the baroreflex's impact on mechanical outputs. [ABSTRACT FROM AUTHOR]

This study proposes a voltage‐retention circuit (VRC) for a low‐power phase‐locked loop (PLL) designed for mobile interfaces. The PLL, incorporating the proposed scheme, supports the sleep mode to achieve low power consumption and fast switching between the sleep and active modes. To facilitate rapid switching between these modes, the proposed VRC stores the filter information from the previous input during sleep mode, ensuring quick settling upon reactivation. The VRC comprises a resistor‐steering digital‐to‐analog converter (DAC), a comparator, and a counter. During the active mode, the circuit adjusts the DAC using the comparator and counter to track the loop‐filter voltage, and it holds the tracked voltage value during the sleep mode. The proposed circuit, designed using a 65‐nm CMOS process, demonstrates 54% improved settling time compared to conventional circuits. Additionally, it reduces power consumption during sleep mode by 88%. [ABSTRACT FROM AUTHOR]

This study presents an innovative dual closed-loop DC control system for intelligent electric vehicle (EV) charging infrastructure, designed to address the challenges of high power factor, low harmonic pollution, and high efficiency in EV charging applications. The research implements a three-level Pulse Width Modulation (PWM) rectifier with a diode-clamped topology and Insulated-Gate Bipolar Transistors (IGBTs), achieving a power factor of 0.99, a total harmonic distortion (THD) of 1.12%, and an efficiency of 95% through rigorous simulation. These results surpass those of wireless charging technology and bidirectional DC–DC converters, demonstrating the system's superiority in key performance metrics. The dual closed-loop strategy, integrating a current inner loop and a voltage outer loop, ensures rapid response and high steady-state accuracy, with the PI regulator effectively managing phase coupling for balanced power flow. The voltage outer loop's stability is critical for the system's reliable operation. The study also discusses the challenges in the dynamic variation of midpoint source current and proposes future work to increase the system's switching frequency, improve anti-interference capabilities, and enhance the accuracy of the sampling process. Advanced computational intelligence and optimization techniques are highlighted as essential for tackling the complex challenges of modern EV charging systems. The study contributes to the development of efficient, secure technology for the next generation of wireless networks and power systems, providing a robust empirical basis for the proposed control strategies through MATLAB/Simulink simulations. This research sets a solid foundation for the performance assessment of EV charging systems, offering high-performance, environmentally friendly, and economically viable solutions for sustainable transportation. [ABSTRACT FROM AUTHOR]

This paper deals with the problem of robust regulation of a Planar Vertical Takeoff and Landing (PVTOL) aircraft affected by crosswind disturbances. The proposed approach simultaneously exploits the advantages of passivity-based control and the integral sliding mode (ISM) control technique. We demonstrate that the passivity-based controller accomplishes the PVTOL regulation within a guaranteed stability region. At the same time, the ISM controller can effectively counteract the undesirable disturbances effect from the beginning of the operation since the disturbances are never seen in the measurable output. Using the passivity approach with LaSalle's Invariance Theorem, we construct the required Lyapunov function to establish the closed-loop system stability. The proposed combination of controllers results in a robust system that satisfactorily solves the regulation problem. Numerical simulations are provided to show that the proposed approach allows the tracking of different reference signals: pulse-train shaped trajectory and ellipse-shaped trajectory, considering the presence of perturbations (crosswind). Furthermore, to illustrate the effectiveness of the proposed technique, a comparative analysis considering two robust control strategies is provided. [ABSTRACT FROM AUTHOR]

Neurofeedback (NF) is endogenous neuromodulation of circumscribed brain circuitry. While its use of real-time brain activity in a closed-loop system is similar to brain–computer interfaces, instead of controlling an external device like the latter, the goal of NF is to change a targeted brain function. In this special issue on NF, we present current and future methods for extracting and manipulating neural function, how these methods may reveal new insights about brain function, applications, and rarely discussed ethical considerations of guiding and interpreting the brain activity of others. Together, the articles in this issue outline the possibilities of NF use and impact in the real world, poising to influence the development of more effective and personalized NF protocols, improving the understanding of underlying psychological and neurological mechanisms and enhancing treatment precision for various neurological and psychiatric conditions. This article is part of the theme issue 'Neurofeedback: new territories and neurocognitive mechanisms of endogenous neuromodulation'. [ABSTRACT FROM AUTHOR]

The presented research introduces a control strategy for a three-phase grid-tied LCL-filtered quasi-Z-source inverter (qZSI) using a Lyapunov-function-based method and cascaded proportional-resonant (PR) controllers. The suggested control strategy ensures the overall stability of the closed-loop system and eliminates any steady-state inaccuracy in the grid current. The inverter current and capacitor voltage reference values of qZSI are created by the utilization of cascaded coupled proportional-resonant (PR) controllers. By utilizing synchronous reference frame and Lyapunov function- based control, the requirement to perform derivative operations and anticipate inductance and capacitance are avoided, resulting in achieving the goal of zero steady-state error in the grid current. The qZSI can accomplish shoot-through control by utilizing a simple boost control method. Computer simulations demonstrate that the suggested control strategy effectively achieves the desired control objectives, both in terms of steady-state and dynamic performance. [ABSTRACT FROM AUTHOR]

The objective of this research is to reduce the speed fluctuation of Permanent Magnet Synchronous Motor (PMSM) due to periodic torque fluctuation. To achieve this, the authors designed a cascade control system based on Linear/Nonlinear Switching Active Disturbance Rejection Control (SADRC) and Quasi Resonant Controller (QRC). Periodic torque pulsations, mainly the first, second, and fourth harmonics, are analyzed first. The architecture of the SADRC and QRC cascade control systems is then established. Subsequently, the parameters of SADRC and QRC are calibrated by the bandwidth method, and a closed-loop system model of cascade control is developed. Ultimately, periodic load fluctuations with step load fluctuations are applied at the load side to ascertain the efficacy of the SADRC and QRC cascade control systems. The SADRC and QRC cascade control reduce the first, second, and fourth harmonics of speed fluctuations by 74%, 33%, and 47.5%, respectively, through the use of QRC current compensation in the presence of peak 2 N m periodic torque fluctuations. The SADRC and QRC cascade control systems demonstrate excellent performance in the context of cyclic and step load fluctuations. [ABSTRACT FROM AUTHOR]

In this paper, fractional calculus is used to develop a generalized fractional dynamic model of an electrohydraulic system composed of a servo valve and a hydraulic cylinder, where a fractional position controller P I γ D μ is proposed for minimizing the performance index according to the integral of the time-weighted absolute error (ITAE). First, the general mathematical equations of the cylinder and servo valve are used to obtain the transfer functions in fractional order by applying Caputo's definition and a Laplace transform. Then, through a block diagram of the closed-loop system without a controller, the fractional model is validated by comparing its performance concerning the integer-order electrohydraulic system model reported in the literature. Subsequently, a fractional PID controller is designed to control the cylinder position. This controller is included in the closed-loop system to determine the fractional exponents of the transfer functions of the servo valve, cylinder, and control, as well as to tune the controller gains, by using the ITAE objective function, with a comparison of the following: (1) the electrohydraulic system model in integer order and the controller in fractional order; (2) the electrohydraulic system model in fractional order and the controller in integer order; and (3) both the system model and the controller in fractional order. For each of the above alternatives, numerical simulations were carried out using MATLAB®/Simulink® R2023b and adding white noise as a perturbation. The results show that strategy (3), where electrohydraulic system and controller model are given in fractional order, develops the best performance because it generates the minimum value of ITAE. [ABSTRACT FROM AUTHOR]

Many existing control techniques proposed in the literature tend to overlook faults and physical limitations in the systems, which significantly restricts their applicability to practical, real-world systems. Consequently, there is an urgent necessity to advance the control and synchronization of such systems in real-world scenarios, specifically when faced with the challenges posed by faults and physical limitations in their control actuators. Motivated by this, our study unveils an innovative control approach that combines a neural network-based sliding mode algorithm with fuzzy logic systems to handle nonlinear systems. This proposed controller is further enhanced with an intelligent observer that takes into account potential faults and limitations in the control actuator, and it integrates a fuzzy logic engine to regulate its operations, thus reducing system chatter and increasing its adaptability. This strategy enables the system to maintain regulation in the face of control input constraints and faults and ensures that the closed-loop system will achieve convergence within a finite-time frame. The detailed explanation of the control design confirms its finite-time stability. The robust performance of the proposed controller applied to autonomous and non-autonomous systems grappling with control input limitations and faults demonstrates its effectiveness. [ABSTRACT FROM AUTHOR]

A novel, precise disturbance rejection dynamic inversion control algorithm has been proposed. In the high-order dynamic surface control system, an innovative approach utilizes a monotonically increasing inverse hyperbolic sine function to construct an extended state observer, which estimates the uncertain functions at each step. The monotonicity of the inverse hyperbolic sine function simplifies the system stability analysis. Additionally, being a smooth function, it avoids the disturbances caused by piecewise functions at their breakpoints in conventional observer construction, thereby enhancing system stability. The accurate prediction capability of the new observer improves the system's disturbance rejection performance. To address the inherent differential explosion phenomenon in traditional dynamic inversion control schemes, this paper ingeniously employs a tracking signal observer as a substitute for traditional filters, thus avoiding the differential explosion that may occur with first-order filters. Finally, comparative simulations were conducted to validate the effectiveness of the proposed method. The results show that both the observer and the controller possess high-gain characteristics, and the closed-loop system exhibits a fast convergence rate. [ABSTRACT FROM AUTHOR]

Background: Insulin pumps coupled with continuous glucose monitoring sensors use algorithms to analyze real-time blood glucose levels. This allows for the suspension of insulin administration before hypoglycemic thresholds are reached or for adaptive tuning in hybrid closed-loop systems. This longitudinal retrospective study aims to analyze real-world glycemic outcomes in a pediatric population transitioning to such devices. Methods: We evaluated children with type 1 diabetes mellitus (T1D) admitted to the Pediatric Diabetes Department from a major University Hospital in Bucharest, Romania, who transitioned to hybrid closed-loop or predictive low-glucose suspend system from either non-automated insulin pumps or multiple daily injections. The primary outcome was assessing the change in glycated hemoglobin (HbA1c) after initiating these devices. Secondary outcomes analyzed changes in glucose metrics from the 90 days prior to the baseline and follow-up visit. Results: 51 children were included (58.8% girls), the mean age was 10.3 ± 3.7 years, and the mean follow-up duration was 13.2 ± 4.5 months. The analyzed parameters, such as HbA1c (6.9 ± 0.7% vs. 6.7 ± 0.6%, p = 0.023), time in range (69.3 ± 11.2% vs. 76 ± 9.9%, p < 0.001), time in tight range (47.4 ± 10.9% vs. 53.7 ± 10.7%, p < 0.001), time below range (5.6 ± 2.9% vs. 3.5 ± 1.9%, p < 0.001), time above range (25 ± 11.2% vs. 20.4 ± 9.4%, p = 0.001), and coefficient of variation (37.9 ± 4.8% vs. 35.6 ± 4.6%, p = 0.001), showed significant improvements. Conclusions: The application of these sensor-integrated insulin pumps can significantly enhance metabolic control in pediatric populations, minimizing glycemic variations to mitigate complications and enrich the quality of life. [ABSTRACT FROM AUTHOR]

The traditional second-order sliding mode (SOSM) algorithms can only achieve the finite-time regulation for standard integrator sliding mode systems and the convergence time of which is dependent on the system's initial values and grows as the initial values grow. In this paper, we propose a novel fixed-time SOSM controller whose settling time is bounded by a fixed time independent of the system's initial values. First, a new sliding mode system subjects to a non-vanishing mismatched term is developed to reduce the input uncertainties and relax the well-defined relative degree assumption. Second, a Lyapunov criterion for practical fixed-time stability with a less conservative convergence time estimation is introduced, based on which a practical fixed-time SOSM controller is designed for the new sliding mode system. Finally, a strict Lyapunov analysis demonstrates that the closed-loop system is globally practically fixed-time stable (GPFxTS). Particularly, if the mismatched term is vanishing, global fixed-time convergence of the sliding variable to zero can be achieved. Buck converter is given as an application. [ABSTRACT FROM AUTHOR]

This paper concerns with the problem of robust event-triggered data-driven control (DDC) considering control input and rate control constraints, simultaneously for discrete-time multi-input multi-output (MIMO) linear systems such that only the noisy data are measurable. Firstly, the data-dependent representation of the closed-loop system controlled by an event-triggered-based feedback control law is obtained. More precisely, to reduce the unnecessary communication resources, the control input updates and consequently, improve the system performance, event-triggered mechanism is utilized to design a stabilizing controller. Under a decreasing triggering threshold and a quadratic Lyapunov function, the ultimate boundedness stability (UBS) of the closed-loop system is ensured and the bounded region is expressed. Sufficient conditions for the UBS of the system are derived in terms of data-dependent linear matrix inequalities (LIMs). To meet the practical problems such as inherent limitations of the practical systems and to maximize the life-time of the actuators, the control input and rate control constraints are considered, simultaneously in the design procedure. In this scenario, the sufficient conditions are also obtained based on data-dependent LMIs. Finally, to demonstrate the effectiveness of the proposed control method, the recommended robust constrained event-triggered DDC is implemented to a numerical example and the simulation results demonstrate the validity of the proposed control approach. Moreover, a table is presented to compare the practical metrics such as robustness, necessities of the model plant identification, computational burden and control input constraints to verify the superiorities of the proposed method despite the existing results. [ABSTRACT FROM AUTHOR]

Globally, bioenergy development depends on the efficacy and affordability of conversion technologies and the availability of renewable biomass sources. As a tropical country, Indonesia has a wide range of biomass sources, either from land or marine biomass (i.e. macroalgae). The current estimation of macroalgae potential in Indonesia is estimated at approximately 9.96 million tonnes or about 26.86% share of world production in 2021. Specifically, marine macroalgae (wild or cultivated) have received attention for their potential as renewable resources for the sustainable bioenergy production, supporting a move towards a circular economy. However, as a developing country, Indonesia still needs to evolve and further advances its technology and skill capacity to address research, development, and innovation challenges in this area. Thus, this paper examines the potential biorefinery approach for application and commercialisation in Indonesia. It discusses cultivation practices and the future direction of the most sustainable and feasible routes for bioenergy production from macroalgae, exploring recent developments, opportunities, and challenges towards circular processes. The study proposed that the biorefining of macroalgae into bioethanol, biogas, compost, and solid fuels, either as mono – or co-production, are potential. Therefore, this paper may offer to narrowing the literature's gap and adding a new perspective on the adoption of macroalgae-based bioenergy with integrated biorefinery and closed-loop systems approaches. [ABSTRACT FROM AUTHOR]

To study the regulation and feedback mechanism of cholecystokinin and trypsin in Black bream, Megalobrama pellegrini (Tchang, 1930) 60 days after hatching under 15 days short-term fasting and different feeding frequencies within 24 hours during the same period, Black bream (wet weight 183.75 ± 61.16 mg, total length 20.74 ± 4.08 mm) developed in a recirculating aquaculture system (RAS) were selected. In the short-term fasting trial, body weight, trypsin, and cholecystokinin (CCK) of the feeding control group (FCG) were higher than those of the fasting trial group (FTG). Trypsin and CCK in FTG reached the lowest value on day 9, and CCK content reached the highest value on day 11. In the 24-hour daily rhythm experiment, juvenile fish were randomly assigned to (A) once feeding, (B) twice feeding, (C) three times feeding, and (D) fasting. CCK showed a minimum at 1:00+ in group A, a peak at night in group B\C\D, and a maximum in group C, and a single satiety stimulus can lead to increased hunger. The four treatment groups had an apparent closed-loop regulation, while the control point of the fasting group (D) shifted forward to the next day. In this study, we found only negative feedback regulation of CCK and trypsin at the end of fasting, considering whether the secretory site or anti-inflammatory response caused the increase of CCK. The damage of epithelial cells in the villi of the foregut was greater than that in the hindgut and hepatopancreas, and the detachment of epithelial cells and the striatal margin was the main damage. Different feeding frequencies in a single day did not directly affect the long-term fluctuation of CCK and trypsin diurnal rhythm. Three meals per day may be more conducive to the long-term growth of juvenile Black bream. This study aimed to provide a reference for the feeding strategy of juvenile Black bream in the RAS. [ABSTRACT FROM AUTHOR]

This paper designs an online adjustment strategy for dynamic quantizer parameters and investigates the sliding mode control (SMC) problem for uncertain switched systems under a limited network communication bandwidth. Due to the limitation of the coding length in practical transmission, coding errors can significantly impact the system's ideal performance. To address these issues, a dynamic quantizer is introduced to efficiently encode the system state while minimizing quantization error under the constraint of the finite code length. Additionally, a coding and decoding scheme based on dynamic quantization and a suitable sliding mode controller are designed to obtain a closed-loop switched system. Using Lyapunov functions and the average dwell time method, sufficient conditions are derived to guarantee the reachability of the sliding surface and the exponential ultimate bound (EUB) in the mean square for the closed-loop switched system, even in the presence of coding errors and data loss. The theoretical results are validated through numerical simulations, which demonstrate the effectiveness of the proposed approach. [ABSTRACT FROM AUTHOR]

This paper investigated the tracking problem of mixed H ∞ and L 2 − L ∞ adaptive fault-tolerant control (FTC) for continuous-time interval type-2 fuzzy systems (IT2FSs). For the membership function mismatch and uncertainty between the modules of the nonlinear system, the IT2 fuzzy model is applied to linearly approximate it. The observer can sensitively estimate the system state, and the adaptive fault estimation functions can estimate adaptively the fault signals, which enables the designed adaptive FTC scheme to ensure the asymptotic stability of the closed-loop control system and achieve the desired mixed H ∞ and L 2 − L ∞ tracking performance. The designed adaptive control law can achieve the purpose of dynamic compensation for faults and disturbances, and the introduced lemmas further reduce the design conservatism by adjusting the slack parameters and matrices. Finally, a mass-spring-damping system is used to illustrate the effectiveness of the designed method. [ABSTRACT FROM AUTHOR]

Precise current decoupling is required to achieve good control performance in the vector control of permanent magnet synchronous motor (PMSM), but traditional decoupling methods are unable to solve the problem of poor current decoupling effectiveness when the system inductance parameters are mismatched. Therefore, a decoupling control method of PMSM based on improved nonlinear extended state observer (INESO) is proposed in this paper. Firstly, a smooth, differentiable nonlinear function is used to replace the traditional fal function, which overcomes the problem of discontinuous gain changes. Secondly, a time-varying gain is designed to address the problem of reduced observer performance due to differential peak values in traditional NESO. Finally, the stability of INESO and the current loop closed-loop system is proven, followed by simulation and experimental verification. The simulation and experimental results show the proposed method effectively observes and compensates for system uncertainties, including parameter perturbations, external disturbances, and unmodeled dynamics. This method achieves complete decoupling of d and q -axes currents, while suppressing interference and enhancing the control performance of PMSM. The proposed INESO decoupling method reduces the d -axis current fluctuation about 96% and 90% when the load changes abruptly under motor inductance parameter mismatch, and can reduce q -axis current fluctuation about 88% and 78% when the d -axis current steps, respectively, compared with the conventional Current Feedback Decoupling Control (CFDC) and CDDC decoupling methods. [ABSTRACT FROM AUTHOR]

This paper mainly investigates the fixed-time almost disturbance decoupling (ADD) stabilisation problem for a class of nonlinear systems in the p-normal form. Under suitable assumptions, a novel fixed-time ADD feedback controller is designed to ensure all states in the underlying system are not affected by disturbances. By constructing an appropriate Lyapunov function, it is shown that the corresponding closed-loop system is fixed-time stable which means the upper bound of the settling time depends on the control design parameters only. To testify the effectiveness of the proposal, two simulation examples are presented. [ABSTRACT FROM AUTHOR]

This paper presents an observer-based event-triggered boundary control strategy for the one-phase Stefan problem, utilising the position and velocity measurements of the moving interface. The design of the observer and controller is founded on the infinite-dimensional backstepping approach. To implement the continuous-time observer-based controller in an event-triggered framework, we propose a dynamic event triggering condition. This condition specifies the instances when the control input must be updated. Between events, the control input is maintained constant in a Zero-Order-Hold manner. We demonstrate that the dwell-time between successive triggering moments is uniformly bounded from below, thereby precluding Zeno behaviour. The proposed event-triggered boundary control strategy ensures the well-posedness of the closed-loop system and the satisfaction of certain model validity conditions. Additionally, the global exponential convergence of the closed-loop system to the setpoint is established using Lyapunov approach. A simulation example is provided to validate the theoretical findings. [ABSTRACT FROM AUTHOR]

In this paper, we consider cyber physical systems security control problems under DoS attacks via the tracking-removed autoencoder. The DoS attack model is described by the switch signal, which occurs in the controller-actuator transmission channel. Then, the linear matrix inequality theory is used to solve the average dwell time of the attack mode that the system can tolerate. Moreover, when the attack dwell time exceeds the tolerance range, a tracking-removed autoencoder is chosen to train to get the control signal. And it can be proved that the closed-loop system with the controller based on the tracking-removed autoencoder is asymptotically stable with $ H_\infty $ H ∞ performance index. Finally, the correctness and advancement of the theory are proved by an example. [ABSTRACT FROM AUTHOR]

In this paper, a min–max adaptive dynamic programming approach is studied for a zero-sum differential game problem with unknown nonlinear dynamics. The unknown nonlinear dynamics is learned through the online Recurrent Neural Network (RNN). The error between the learned RNN model and the dynamics of the system is proved to converge to zero. The policy iteration algorithm is utilised to solve the Hamilton–Jacobi–Isaacs (HJI) equation associated with the differential game. Furthermore, the value function in the HJI equation is approximated through a critical Neural Network with its weights and activation functions updated online iteratively. The Uniform Ultimate Bounded stability of the closed-loop system is proved based on the Lyapunov theory. Finally, the effectiveness of the proposed solution method is demonstrated by applying it to three examples. [ABSTRACT FROM AUTHOR]

Introduction: Time in tight range (TITR) is an emerging and valuable metric for assessing normoglycemia. The latest advancement in automated insulin delivery (AID) systems, the advanced hybrid closed-loop (AHCL) systems, are particularly noteworthy for managing type 1 diabetes (T1D) and enhancing glycemic control. Methods: In a real-world clinical setting, we carried out a retrospective evaluation of TITR in 42 adult subjects with T1D using the AHCL Minimed™ 780G system over a 12-month period. Results: Within just 14 days of activating the automatic mode, the AHCL Minimed™ 780G system showed rapid improvement in TITR, and in the other continuous glucose monitoring (CGM) metrics. This improvement persisted over 12 months, achieving the proposed 45–50% range for effective glycemic control. Conclusion: The AHCL Minimed™ 780G system significantly enhances TITR, demonstrating continuous improvement throughout a 12-month follow-up period. [ABSTRACT FROM AUTHOR]

The major contribution of this study is the feedback design of a finite-time convergence sliding mode control to solve the trajectory-tracking problem in a class of mechanical systems. Some advantages are that the controller presents a continuous signal by integration of the high-frequency switching term. Another benefit is the design and implementation of an uncertainty and disturbance estimator (UDE) to robustify the closed-loop system. We use Lyapunov tools to develop the closed-loop stability analysis and to give an expression of the convergence time t = t through this, we can reduce the convergence time by tuning the gains of the controller. We illustrate the performance of the proposed control structure via numerical simulations conducted for a mass-spring-damper system and experiments developed in a pendular system. [ABSTRACT FROM AUTHOR]

Cardiac failures and other cardiovascular diseases are a primary cause of death worldwide. Cardiovascular disorders, including heart failure, are the primary cause of death globally. Controller design for pacemakers is a crucial area of research. In this study, a novel proportional-integral-derivative (PID) controller design that can be used to efficiently regulate the heart rate of the cardiac pacemaker is presented. The proposed PID controller employs only one Differential Voltage Current Conveyor (DVCC) active element, two resistors, and two capacitors. The proposed PID controller circuit has voltage differential inputs, thus eliminating the need for the extra differential amplifier (DA) circuit required for closed-loop systems such as the cardiac pacemaker heart rate control system. A fractional-order (FO) PID controller (PIλDμ) circuit is created from the proposed integer order (IO) PID controller circuit. A cardiac pacemaker application example is given to demonstrate the workability of the proposed FO and IO PID controller circuits. Using 0.18 µm CMOS parameters and the PSPICE simulation program, both the proposed FO and IO PID controller circuits in a closed-loop system are performed to verify the theoretical behavior. [ABSTRACT FROM AUTHOR]

An event-triggered-super twisting sliding mode control (ET-STSMC) with saturation function in reaching law have been designed for a nonlinear Quadcopter model with bounded disturbance and its performance is compared with Event Triggered-Sliding mode control (ET-SMC). Simulation results have been obtained for altitude and attitude tracking, demonstrating the stability of the closed-loop system with the proposed control. The event-triggering conditions are derived based on the Lyapunov method, ensuring non-accumulation of inter-event execution time. Experiments have been performed in real-time to analyse the robustness and computational cost in terms of the number of control updates of the proposed control strategy under normal flight, external disturbances, and parameter uncertainty. Simulation and experimental results show that ET-STSMC can achieves better tracking performance and robustness with reduced computational cost compared to ET-SMC during all flight conditions. [ABSTRACT FROM AUTHOR]

This study introduces a novel control approach for a twin rotor multi-input multi-output system (TRMS), specifically targeting the pitch and yaw movements. The proposed method employs a sliding mode controller (SMC) with variable gains, aiming to overcome limitations like chattering and excessive control effort. Unlike traditional controllers, the gains here dynamically adjust based on the error state, enhancing the robustness of the system against external disturbances and parameter uncertainties. The control algorithm draws inspiration from both first-order and higher-order sliding mode controllers. To rigorously assess the robustness of the controller, Gaussian White noise is incorporated into the model. By dynamically adjusting gains, the proposed approach aims to minimize control effort while mitigating control signal overestimation arising from model uncertainties. Furthermore, stability analysis confirms that the operating point of the closed-loop system converges within a finite time. The effectiveness of this novel controller is validated through simulations using the MATLAB/Simulink environment. [ABSTRACT FROM AUTHOR]

This paper investigates the stochastic path following control of underactuated marine vehicles (UMVs) subject to multiple disturbances and constraints. Firstly, the complex marine environment in which UMVs navigate typically contains stochastic components, thus the multiple disturbances are categorized as slow-varying deterministic disturbances and stochastic disturbances. Secondly, a position-constrained line-of-sight (PCLOS) based fractional-order sliding mode stochastic (FSMS) control strategy is established to achieve path following control of UMVs. A PCLOS guidance law based on universal barrier Lyapunov function is proposed to ensure that the position errors remain within the constraint ranges, which is versatile for systems with symmetric constraints or without constraints. An FSMS controller based on fractional-order theory and sliding mode control is designed to improve the dynamic response speed of the system and effectively attenuate chattering phenomenon. A stochastic disturbance observer is developed to estimate the slow-varying deterministic disturbances in the stochastic system, and auxiliary dynamic compensators are used to mitigate the impact of input constraints. Lastly, theoretical analysis indicates that the closed-loop system is stable and the position constraint requirements are satisfied. Comparative simulations illustrate the effectiveness of the proposed control strategy. • The multiple disturbances are categorized as slow-varying deterministic disturbances, and stochastic disturbances. • A novel PCLOS guidance law is designed to ensure that the position errors do not exceed the given constraint ranges. • The fractional-order sliding mode stochastic control method exhibits improved robustness and flexibility compared to traditional integer-order sliding mode control method. [ABSTRACT FROM AUTHOR]

Crane systems are essential systems utilized in industry and for research. Nevertheless, they are always affected by endogenous and exogenous disturbances, which may generate undesirable payload oscillations, compromising people's security and the system itself. Thus, to deal with these issues and control these mechatronic systems efficiently, this manuscript develops a novel robust observer-based proportional-retarded controller for perturbed two-dimensional cranes, considering variation in the rope length. This novel scheme makes the trolley follow a desired reference signal while reducing the payload variations. The controller structure allows for compensating disturbances, while a new control approach introduces artificial delays that stabilize the closed-loop system and attain the desired control objective. A formal theoretical analysis demonstrates the validity of the new proposal. Then, experimental results show the outstanding performance of the proposed control scheme and its superior performance against other methodologies from the literature. [Display omitted] • A novel robust observer-based proportional-retarded controller applied to 2D-crane systems is proposed. • Unlike previous works, artificial delays are utilized to achieve trajectory-tracking tasks while reducing payload oscillations. • The novel controller reduces payload vibrations and avoids derivative actions. • The conjunction of the observer and the proportional retarded controller provides robustness against internal and external disturbances. • Experimental results demonstrate the outstanding performance of the novel controller when compared against other robust control schemes. [ABSTRACT FROM AUTHOR]

In this paper, a feedback controller based on the extended state observer is proposed for fully actuated systems. First, a generalized proportional–integral observer is designed to estimate states and disturbances simultaneously. Using the linear parameter varying approach and the convexity principle, a linear matrix inequality condition is given to obtain the observer gains. Second, on the basis of the full-actuation property and the estimated states, a feedback controller, utilizing estimated disturbances to compensate for system disturbances, is designed to make all the states of the closed-loop system uniformly ultimately bounded. In addition, if disturbances are constant or slow time-varying, the observation errors and the states of closed-loop system are all exponentially convergent. Two illustrations are provided to show the validity and practicality of the proposed approach. Simulation results show that the estimated disturbances can follow the true values with relatively small errors, so compensating the system disturbances with estimated values can effectively reduce the ultimate bounds of states of the closed-loop system. [ABSTRACT FROM AUTHOR]