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Hydrogen (H2) therapy is an emerging, novel, and safe therapeutic modality that uses molecular hydrogen for effective treatment. However, the impact of H2 therapy is limited because hydrogen molecules predominantly depend on the systemic administration of H2 gas, which cannot accumulate at the lesion site with high concentration, thus leading to limited targeting and utilization. Biomaterials are developed to specifically deliver H2 and control its release. In this review, the development process, stimuli‐responsive release strategies, and potential therapeutic mechanisms of biomaterial‐based H2 therapy are summarized. H2 therapy. Specifically, the produced H2 from biomaterials not only can scavenge free radicals, such as reactive oxygen species (ROS) and lipid peroxidation (LPO), but also can inhibit the danger factors of initiating diseases, including pro‐inflammatory cytokines, adenosine triphosphate (ATP), and heat shock protein (HSP). In addition, the released H2 can further act as signal molecules to regulate key pathways for disease treatment. The current opportunities and challenges of H2‐based therapy are discussed, and the future research directions of biomaterial‐based H2 therapy for clinical applications are emphasized. [ABSTRACT FROM AUTHOR]

We present a new balancing-based structure-preserving model reduction technique for linear port-Hamiltonian descriptor systems. The proposed method relies on a modification of a set of two dual generalized algebraic Riccati equations that arise in the context of linear quadratic Gaussian balanced truncation for differential algebraic systems. We derive an a priori error bound with respect to a right coprime factorization of the underlying transfer function thereby allowing for an estimate with respect to the gap metric. We further theoretically and numerically analyze the influence of the Hamiltonian and a change thereof, respectively. With regard to this change of the Hamiltonian, we provide a novel procedure that is based on a recently introduced Kalman–Yakubovich–Popov inequality for descriptor systems. Numerical examples demonstrate how the quality of reduced-order models can significantly be improved by first computing an extremal solution to this inequality. [ABSTRACT FROM AUTHOR]

TiO 2 -based photoelectrocatalysts are synthesized by anodization at 90, 70 and 50V, using ethylenediamine to incorporate C and N elements (i.e. formation of coordinated complexes). The analysis is focused on determining the effects of oxygen vacancies, crystallite size, phase type, band gap size, elemental surface composition, roughness, and thickness of the photoelectrodes, to establish those influencing the photoelectroactivity of H 2 production. H 2 is generated with irradiations simulating solar conditions, and only visible-light. The photoelectrode formed at 70V develops the largest photocurrent, and consequently the largest H 2 production. It is revealed that the lowest content of oxygen vacancies, the highest amount of elemental C and O at the surface, and the reduction of the main band gap in this photoelectrode substantially control the photoactivity of this reaction. While the roughness and thickness of the coatings, the crystallite size, the specific surface area, and the surface compositions of elemental Ti and N are found to be negligible. [Display omitted] • Ethylenediamine was effective to incorporate C and N species into anodized TiO 2. • C and N incorporations reduced the main band gaps of all (CN)–TiO 2 photoanodes. • Oxygen vacancies, surface contents of C and O, and band gap size control H 2 yield. • Roughness, thickness, and crystallite size of catalysts do not impact H 2 activity. • Specific area and surface compositions of Ti and N are negligible for H 2 generation. [ABSTRACT FROM AUTHOR]

Unmanned aerial vehicles (UAVs) are a new, adaptable technology that has found its way into both military and civilian applications. Preserving the integrity of the UAV and its security during flight and, in particular, during the landing stage is essential for the performance of the assigned mission of the aircraft. This research examines a developed aircraft scheme. It was tested for static and dynamic stability in an XFLR5 virtual aerodynamic environment. The obtained results were transferred to MATLAB-Simulink, where the flight control algorithm was synthesized, the landing mode was set using an engineering flight plan, and an autonomous landing was simulated in the presence of wind disturbances with turbulence and noisy operation of the information measurement complex of the UAV. The algorithm for controlling the landing during the execution of the set flight trajectory, which contains a Kalman estimator and an optimal LQR controller combined in a general LQG control algorithm, is studied. [ABSTRACT FROM AUTHOR]

The pure H2 production procedure for polymer fuel cell applications by the chemical loop reforming of methanol in the presence of 0.3CoFe2O4-0.4ZrO2 as an oxygen carrier in a micro-channel reactor was studied and the results of this study showed that the production of pure H2 is possible only if the coke deposition is controlled. By optimizing the reduction time to 7 minutes, the coke deposition controlled and pure H2 flow was produced with an average yield of 2.6%, which was an interesting result and so far, this degree of purity of H2 has not been reported by the chemical loop reforming of methanol. To increase the yield of pure H2 in this study, a two-layer catalyst concept is proposed in the form of an additional layer coating with high resistance to coke and suitable reactivity with methanol from NiO/MgAl2O4 to 10% on 0.3CoFe2O4-0.4ZrO2 layer. Optimizing the reduction time using the concept of double-layer oxygen carrier showed that the use of 20% nickel concentration with a reduction time of 11 minutes increased the yield of H2 with 100% purity, which increased by 42% in the double-layer arrangement compared to the singlelayer state, and it is a promising result for the concept of double-layer oxygen carrier in this process. [ABSTRACT FROM AUTHOR]

Objective Our research was performed in order to explore the effects of molecular hydrogen (H2), a novelly-established antioxidant, on the retinal degeneration in rd1 mice, an animal model of inherited retinitis pigmentosa (RP). Methods The rd1 mice were divided randomly into control and H2 intervention groups. Mice from other groups received H2 intervention in three modes, two modes of the hydrogen gas (HG) and one model of hydrogen-rich saline (HRS). At 14 days post born (P14) and P21, various indicators were detected in all mice, including eletroretinogram (ERG), fundus phography, optical coherence tomography (OCT), and retinal immunotaining of microglia cells' marker, Iba1. Results The ERG amplitude in mice from the control and H2 intervention groups showed no statistical differences (p > 0.05). At P14 and P21, no significant difference in the distance from the retinal pigment epithelium to the outer plexiform layer on OCT from mice of the above two groups was found (p > 0.05). The thickness of the outer nuclear layer (ONL) in mice at P14 and P21 showed no statistical differences between the control group and the H2 intervention group (p > 0.05). In the aspect of the number of Iba1-positive cells, we did not found any significant differences between the two groups (p > 0.05). Conclusion Different forms of H2 intervention (hydrogen-rich saline and hydrogen gas) had no obvious effects on the course of retinal degeneration in rd1 mice. The specific mechanism of photoreceptor degeneration in the hereditary RP mouse model may be different, requiring different medical interventions. [ABSTRACT FROM AUTHOR]

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Purpose: Semi-active control is considered to be very interesting for its engineering sophistication/effectiveness like the active control strategy, however, requiring significantly lesser amount of control effort/input. In view of the devastating damages of soft-storey building structures in case of real-life seismic events, a study on semi-active vibration control for vulnerable structures like soft-storey buildings appears very interesting. Methods: The magnetorheological (MR) damper is taken as the control device which produces control force through modulating its damping coefficient with the help of external input voltages in a semi-active control framework based on the widely used Linear Quadratic Gaussian (LQG) control. The Bouc–Wen hysteresis model is considered to calculate the control force. A realistic five-storey building with soft-storey at the ground is considered for validation. Besides, the performance of LQG control is compared with the proportional-integral-derivative (PID) control. Results: It is observed that LQG-based semi-active control strategy has been able to perform satisfactorily (in reducing soft-storey response) with the cost of surprisingly insignificant amount of control effort (with supply voltage in the range, 0–2.5 V) by reducing the peak response as 67.5%, 78.05%, 67.57%, 75%, and 51.02% against El Centro, Northridge, Kobe, Bhuj, and Tohoku earthquakes, respectively, while 68.85%, 79.42%, 65.26%, 73.38%, and 51.65% in case of root-mean-square response. Higher range of supply voltage is found to provide even better control performance. Conclusion: In view of the satisfactory control performance, the semi-active control with MR dampers using LQG control is well encouraging in protecting the highly vulnerable soft-storey building structures under seismic events. [ABSTRACT FROM AUTHOR]

Redundancies in modern systems, including multiple channels, processes, and storages, are often exploited to ensure robust operation. Similarly, a Networked Control System (NCS) may utilize multiple channels to facilitate reliable information transfer in case of channel failure. To enhance the performance of Linear Quadratic Gaussian (LQG) control in environments with multiple channels, delays, and packet errors, we propose channel-switching algorithms. Leveraging the encoder and decoder structure for channel modeling, we derive the decoder estimation error covariance matrix, characterizing LQG control performance with respect to delay. Based on this insight, we develop two threshold-based channel-switching algorithms, proven to ensure finite total decoder estimation error variance under certain conditions. Specific conditions are also identified where the proposed algorithms offer improved probabilistic stability. Numerical simulations confirm the superior performance of the proposed algorithms compared to conventional methods across diverse channel environments. Notably, the proposed algorithms demonstrate near-optimal performance in a practical operational scenario involving multiple channels, specifically 5G cellular link and Starlink. [ABSTRACT FROM AUTHOR]

The minimum expected energy cost model, which has been proposed as one of the optimization principles for movement planning, can reproduce many characteristics of the human upper-arm reaching movement when signal-dependent noise and the co-contraction of the antagonist's muscles are considered. Regarding the optimization principles, discussion has been mainly based on feedforward control; however, there is debate as to whether the central nervous system uses a feedforward or feedback control process. Previous studies have shown that feedback control based on the modified linear-quadratic gaussian (LQG) control, including multiplicative noise, can reproduce many characteristics of the reaching movement. Although the cost of the LQG control consists of state and energy costs, the relationship between the energy cost and the characteristics of the reaching movement in the LQG control has not been studied. In this work, I investigated how the optimal movement based on the LQG control varied with the proportion of energy cost, assuming that the central nervous system used feedback control. When the cost contained specific proportions of energy cost, the optimal movement reproduced the characteristics of the reaching movement. This result shows that energy cost is essential in both feedforward and feedback control for reproducing the characteristics of the upper-arm reaching movement. [ABSTRACT FROM AUTHOR]

In this paper, the problem of designing static output feedback (SOF) H 2 negative imaginary controller has been studied. Because the constraints brought by negative imaginary (NI) property and H 2 performance are a set of bilinear matrix inequalities (BMIs), designing an SOF NI controller with H 2 performance is a non-trivial problem. To overcome the difficulty of solving BMIs, a linearisation-based method is proposed. First, a necessary and sufficient condition is established, where the constraints of NI property and H 2 performance are reformulated as similar forms. Second, inspired by the semidefinite programming, the derived condition is converted to the difference between two convex functions. Then a linearised iterative algorithm with initialisation process is provided to compute the desired SOF H 2 NI controller. Finally, two numerical examples are presented to illustrate the proposed results. [ABSTRACT FROM AUTHOR]

The Quadcopter is a flying machines that has four propellers driven by rotors. It has a simple mechanical design and excellent maneuverability and can perform vertical takeoff and landing. In order for the quadcopter to fly properly, a controller is needed that can maintain the stability of its flight. In this paper, a comparison of quadcopter motion stability testing using the Feedback control and LQG methods was carried out. The Linear Quadratic Gaussian control method is used in this research, which combines the Linear Quadratic Regulator with Kalman Filter. LQG control was chosen because it can estimate state variables that are not measured and save costs and time. At the same time, the feedback control system was selected because it can improve systems performance from the feedback generated. This research shows that the LQG control system is better than the feedback control. [ABSTRACT FROM AUTHOR]

Dead-time is the most important disturbance in a voltage-source inverter's operation. It introduces low-order harmonics at the inverter's output voltage. To compensate for the dead-time effects in three-phase grid-tied inverters, this paper proposes a Linear Quadratic Gaussian (LQG) multivariable control approach. The LQG multivariable control is known as a robust control approach while provides a high band-width for the closed-loop system. Therefore, it promises significant attenuations in the dead-time introduced harmonics. To achieve a high performance, we run the three-phase grid-tied inverter in the current-controlled mode. Based on the nominal multivariable model derived for the three-phase grid-tied inverter in a synchronous reference frame, the LQG controller is composed such that the closed-loop system exhibits robust stability while attenuates disturbances significantly. The dead-time introduced harmonics produce disturbances in the synchronous reference frame with the highest frequencies. This is the reason for considering the dead-time as the most important disturbance in an inverter's operation. For an experimental set-up manufactured for the three-phase grid-tied inverter, we developed a detailed model in MATLAB/Simulink. It is employed for the performance verifications of designed LQG controller. Extensive results are presented for different important scenarios, based on which, the excellent performance of proposed approach is proven. In fact, by employing the proposed approach, the dead-time introduced harmonics are significantly attenuated such that a Total Harmonics Distortions (THD) of about 5% is achieved for the injected currents to grid which meets the IEEE 1547 standard. [ABSTRACT FROM AUTHOR]

Purpose: The purpose of this study is to test the performance of the designed automatic control system based on the Linear Quadratic Regulator (LQR) and Linear Quadratic Gaussian (LQG) algorithms during landing of the helicopter on the ship deck. This paper is a further development of the series based on Topczewski et al. (2020). Design/methodology/approach: The system consists of two automatic control algorithms based on LQR and the LQG. It is integrated with the ship motion prediction system based on autoregressive algorithm with parameters calculated using Burg's method. It is assumed that the source of necessary navigation data is integrated Inertial Navigation System with Global Positioning System. Landing of the helicopter on the ship deck is performed in automatic way, based on the preselected procedure. Performance of the control system is analyzed when all necessary navigation data is available for the system and in case when one of the parameters is unavailable during performing the procedure. Findings: In this paper, description of the designed control system developed for performing the approach and landing of the helicopter using selected procedure is presented. Helicopter dynamic model is validated using the manufacturer data and by test pilots, overview is presented. Necessary information about ship motion model is also included. Tests showing mission performance while using LQR and LQG algorithms applied to the control system are presented and analyzed, taking into account both situations when full navigation data is available/unavailable for the control system. Practical implications: Results of the system performance analyses can be used for selection of the proper control methodology for prospective helicopters autopilots. Furthermore, the system can be used to analyze the mission safety when information about one of the navigation parameters is identified by the navigation system as unavailable or incorrect and therefore unavailable during landing on the ship deck. Originality/value: In this paper, control system dedicated for the automatic landing of the helicopter on the ship deck, based on two different control algorithms is presented. Influence of lack of information about one of the navigation parameters on the mission performance is analyzed. [ABSTRACT FROM AUTHOR]

An induction motor's speed can be managed in a variety of ways using a Variable Frequency Drive (VFD). In this study, the speed control of an induction motor will be controlled by applying Indirect Field Oriented Control (IFOC) combined with Linear Quadratic Gaussian (LQG). Conventional LQG control is a linear controller; therefore, if the system's dynamic is high and over the linear boundary, the LQG performance will not be optimal. Therefore, Adaptive LQG (ALQG) is proposed. Fuzzy logic is used as an adaptive algorithm with low complexity and ease of implementation. The significance of this study lies in its endeavor to tackle the challenges associated with nonlinearities and high dynamics in induction motor control. The average performance of speed variation and load variation tests proves that ALQG is superior in terms of settling time and undershooting than PID and LQG. PID has the highest overshoot with the smallest Integral Absolute Error (IAE). In comparison, ALQG is superior to conventional LQG in terms of IAE with 3.59% lower. [ABSTRACT FROM AUTHOR]

The decentralized linear–quadratic–Gaussian (LQG) control problem for networked control systems (NCSs) with asymmetric information is investigated, where controller 1 shares its historical information with controller 2, and not vice versa. The asymmetry of the information structure leads to the coupling between controller 2 and estimator 1, and hence the classical separation principle fails. Through the assumption of linear control strategy, the coupling between controller 2 and estimator 1 (CCE) is decoupled, but the estimation gain is still coupled with the control gain. It is noted that the control gain conforms to the backward Riccati equation while estimation gain abides by the forward equation, which is computationally challenging. Applying the stochastic maximum principle, the solvability of the decentralized LQG control problem is reduced to that of corresponding forward and backward stochastic difference equations (FBSDEs). Further, necessary and sufficient conditions for the solvability of optimal control problem are presented by two Riccati equations, one of which is nonsymmetric. Moreover, a novel iterative forward method is proposed to calculate the coupled backward control gain and forward estimation gain. [ABSTRACT FROM AUTHOR]

This paper proposes a Linear Quadratic Gaussian (LQG) control design for a grid-connected and Islanded mode Microgrid composed of a single-network feeding and forming converter with one local load. The LQG controller was designed for two different Microgrid modes: Grid-connected mode and islanded mode. A separate LQG controller was designed for each mode and a comparative analysis was made. The LQG controller was designed using the State-Space variables determined by linearizing the model. The controller consists of the optimal gain 'K', optimal Linear Quadratic Regulator (LQR), and the Kalman Filter. In both Microgrid modes, the LQG eliminates disturbance and noise in the system and makes the system optimally controlled. The Microgrid system also consists of another control system that comprises the subsequent control subsystem, i.e., Alpha–Beta control, Power and Current loop, and Space Vector Modulation. The steady-state response of the Microgrid system, noise, and disturbance present in Grid-connected and islanded modes was rectified by the LQG controller. The design environment used for developing the Microgrid and LQG controller was the MATLAB/Simulink platform. The effective simulations have permitted and determined results that convey the optimal control and stable performance of the proposed system. [ABSTRACT FROM AUTHOR]

In this paper we describe the certainty-equivalent of the infinite horizon with discounted cost for the linear-quadratic-Gaussian model. Existence of optimal solution is investigated as well as explicit formulas for the value function. This problem is related with the ergodic (average cost per unit time) criterion, analyzing the asymptotic behavior when the discount factor vanishes. It is shown that under a suitable log transformation, a functional of the risk-sensitive discounted cost converges to the risk-sensitive average cost. This convergence is studied through the solutions of the associated Bellman equations. In addition, we obtain explicitly the set of values for the risk parameter for which no breakdown exists for the value functions. [ABSTRACT FROM AUTHOR]

This paper proposes a robust guaranteed-cost controller for a half-vehicle active suspension system (HVASS) where the controller is subject to stochastic gain fluctuations. This randomly occurring uncertainty is a result of the imperfect implementation of the controller as well as the aging of the components. In this approach, the state-feedback controller is represented via multiple gains orchestrated by a Markovian process, and then an optimal multi-mode design approach with H2 norm constraints is considered to ensure system's asymptotic stability with a prescribed disturbance attenuation level. This design is based on Lyapunov theory and the controller is realized via a set of linear matrix inequalities. Compared to the existing works, the design is more reliable for practical HVASSs and is directly reducible to systems with perfectly implemented controllers. Simulation results and comparisons demonstrate the applicability and potentials of the proposed method. [ABSTRACT FROM AUTHOR]

Designing a robust aircraft control system used to achieve a good tracking performance and stable dynamic behavior against working disturbances problem has attracted attention of control engineers. In this paper, a pitch angle control system for aircraft is designed utilizing liner quadratic Gaussian (LQG) optimal controller technique with a numerical tuning algorithm method in the longitudinal plane through cruising stage. Main design approach of LQG controller includes obtaining best weighting matrices values using trial and error method that consumes effort and takes more time, in addition, there is no guarantees to obtain optimum values for weighting matrices elements. In this research, genetic algorithm (GA) is used to optimize the state and control weighting matrices and determine best values for their elements. The proposed traditional and optimized LQG pitch controller schemes are implemented utilizing Matlab simulation tool and their performance are presented and compared based on transient and steady state performance parameters. The simulation results reveal the ability of the optimized GA_LQG controller to reject the effect of the noises in the aircraft system dynamic and achieve a good and stable tracking performance compared with that of the conventional LQG pitch control system. [ABSTRACT FROM AUTHOR]

This work proposes a novel Linear Quadratic Gaussian (LQG)-based blade pitch control method for floating offshore wind turbines, in which a state-space model of the turbine and water hydrodynamics is included in the LQG design. The actuation considered is collective blade pitch control with the objective of generator power stabilisation and platform motion reduction. A linear Kalman filter is used to estimate un-measurable states relating to wave excitation and radiation through measurements of generator speed, platform pitch, and wind disturbance. Controller design models were validated with the full order nonlinear model under various testing conditions. The new controller design is tested on a nonlinear high-fidelity simulation model of the 15 Mega-Watt (MW) floating semi-submersible wind turbine. In simulations with realistic stochastic wind and wave disturbances, the new controller achieves 32% lower generator speed Root Mean Square Error (RMSE) and 16% lower platform pitch RMSE compared to a standard LQG controller that does not include hydrodynamic states, for equivalent levels of pitch actuation and with a 2 ° /sec rate limit on pitch. The inclusion of hydrodynamics in the controller design not only reduced platform pitching fluctuation, but also had a strong effect of hub-height factors such as the generator speed. • Evaluate LQG controllers on the recently released IEA 15 MW floating wind turbine. • Incorporate wave excitation and radiation state space approximations in LQG control. • Estimate non-measurable states for control of hydrodynamics using Kalman filters. • Test controllers on stochastic wind and wave elevation cases in OpenFAST. [ABSTRACT FROM AUTHOR]

Active vibration control systems are commonly reported to be the most robust and effective method for vibration control of structures. However, the type of ground motions and the type of analysis may greatly influence their performances. This study investigates the seismic response of building with and without an active controller under pulse-type ground motions. A 20-story non-linear steel benchmark building is considered. Linear and non-linear analysis is conducted to check the effectiveness of the active control system. Active control with a linear quadratic Gaussian (LQG) control algorithm is applied to the benchmark building for seismic control purposes. Initially, some ground motions are selected following earlier studies from the literature concerning the benchmark building. It is found that the LQG control algorithm is quite effective under the considered earthquakes, and the analysis type does not affect the effectiveness of the controller. Thereafter, a set of additional 69 pulse-type ground motions are considered to check the performance of the LQG control algorithm and to find the suitability of linear analysis. It is noticed that under such pulse-type ground motion, the LQG control algorithm is not much effective if the non-linear behavior of the structure is incorporated in the seismic analysis, whereas in case of linear analysis, the LQG control algorithm is still effective. It is concluded that neglecting the non-linear behavior may lead to unconservative estimates of the seismic response when performing seismic analysis and designing structures equipped with active vibration control systems. [ABSTRACT FROM AUTHOR]

This paper examines how the combined use of hydro governors and a wide‐area damping controller (WADC) can improve the damping of inter‐area oscillations in power systems. Such oscillations can endanger the stability of power grids, thus damping them is a high priority for transmission system operators (TSO). To ensure that low‐frequency oscillations decay as fast as possible, a modal linear quadratic Gaussian (LQG) is proposed as a wide‐area controller approach. Using the 10‐machine New England Test System, the combined application of the WADC in hydropower plants via generator excitation as well as via the hydro governor is examined for their effectiveness in terms of damping capability. In order to minimize the number of essential PMUs in power systems for the model‐based WADC, the residue‐based input/output signal selection method is applied. To increase the robustness against large disturbance faults, the generator voltage as additional signal is utilized for the WADC. For controller performance and robustness, the verification has been done under various operating points, tie‐line failures as well as different PMU delays. The successful damping of the inter‐area oscillation by means of wide‐area controlled hydropower plants has been also demonstrated through a nonlinear time domain simulation. [ABSTRACT FROM AUTHOR]

Spherical motors capable of omnidirectional rotations in a ball joint provide a highly dexterous actuator system yet also present great challenges in developing a high-performance regulation and tracking controller due to the complex rotor dynamics. This article presents a complementary H2-H∞(C-H2-H∞) control method for precisely controlling the multidegree of freedom (DOF) orientation of spherical motors in presence of external disturbances as well as model uncertainties and inaccuracies. In order to deal with the tradeoff between the robustness and control performance resulted from conventional control methods, the proposed controller featured with a 2-DOF structure presents an H2 controller for a nominal plant and then complements it with an additional regulator designed in H∞sense to assure robustness. Unlike traditional H∞ or mixed H2and H∞ controller, the H∞regulation is conducted online in accordance with the monitored modeling mismatch in a way that does not adversely degrade the performance delivered by H2 control, hence, improving the conservativeness of the total control performance and leading to significant improvements of tracking accuracy and response time at same time. Both numerical simulations and experiments on a spherical motor testbed are conducted to validate the superior performance of the proposed controller versus conventional control methods. [ABSTRACT FROM AUTHOR]

This paper mainly studies the generalized H2 control of discrete‐time semi‐Markov jump systems with bounded sojourn‐time. By constructing the mode‐dependent Lyapunov function related to the elapsed‐time and the semi‐Markov process, we obtain sufficient conditions to ensure the σ‐error mean square stable and generalized H2 performance of the semi‐Markov jump system. Moreover, by introducing slack variables, the generalized H2 performance index is reduced and the feasible region is expanded. Finally, through numerical calculations, we confirm the effectiveness of the design methods. [ABSTRACT FROM AUTHOR]

In this research, a novel robust decentralised H (H ∞ and H 2) design combined with a pattern search method (PSM), incorporating considerations of multiple modal dynamics, was developed to address the vibration issue in slender structures. To verify the effectiveness of the concept, a full-scale laboratory reconfigurable multiple degrees of freedom (MDOF) test-bed floor panel structure was selected, equipping with a passive multiple-tuned mass damper (MTMD) as a coupling system. The optimal parameters of the MTMDs were tailored using the decentralised H design and the PSM, considering the dynamic engagement of multiple modes. Furthermore, a crucifix-type configuration of 2DOF MTMDs was proposed to mitigate the vibration of the floor panel structure. Full-scale forced vibration testing (FVT) was conducted to validate the dynamic performance of the 2DOF MTMDs. The test results provide satisfactory verification and high-quality curve-fitting testing data for parameter study and dynamic simulation. By examining the field data from the 2DOF MTMDs and performing various numerical simulations and analyses, the control performance robustness of the MTMDs was comprehensively evaluated, considering practical engineering variations such as the number and stiffness of MTMDs, as well as the stiffness and mass of the floor panel structure. As a result, the proposed H control strategies for the MTMDs demonstrated robust control capabilities by effectively dissipating significant amounts of externally applied energy. • A novel decentralised strategy with H ∞ and H 2 control, pattern search method (PSM), and multiple modal dynamics for multiple degrees of freedom (MDOF) multiple tuned mass dampers (MTMD) design. • Validation via full-scale force vibration testing (FVT) on a reconfigurable MDOF test-bed floor panel. • Prototype of 2DOF MTMDs integrated for vibration suppression through energy dissipation. • Comprehensive analysis of numerical MTMDs models to evaluate robustness and sensitivity. [ABSTRACT FROM AUTHOR]

This article presents a design method to improve the robustness in stability and performance of an LQG controller by the LMI approach applied to a multivariable system subject to parametric uncertainties, where its variations are known to have a direct impact on the degradation of the robustness margins of a classical LQG controller. The main of this work is to synthesize a robust Linear Quadratic Gaussian (LQG) controller reformulated by the Linear Matrix Inequality (LMI) approach and to apply it on an illconditioned system. Our choice fell on a doubly fed induction generator (DFIG) of the aero-generator to produce electrical energy, whose physical parameters are uncertain due to several factors: winding heating, magnetic saturation..., this makes it difficult to maintain the voltage at 220V and the frequency at 50Hz. First, the mathematical model of DFIG is written in a d-q reference frame. The singular values of the uncertainties are quantified and multiplied at the system output, and then the robustness conditions are determined. Secondly, the robust control law by the LQG synthesis based on the solution of the convex optimization problem under LMI Eigenvalue problem is elaborated and detailed. The simulation results of the stability and performance robustness of the LQG controller by the LMI approach with nominal and disturbed model of the DFIG are presented and discussed on the method efficiency. [ABSTRACT FROM AUTHOR]

In recent years, the development of hydraulic variable displacement axial piston machines has been focused in two main directions: improvement of their construction and improvement of their displacement control methods. The goal of both directions is to increase the efficiency of the machines. Increasing their efficiency is key to improving the efficiency of the entire hydraulic system, whether they are used as pumps or hydraulic motors. This motivates the present work, which essentially contains a developed embedded control system designed for a known type of open circuit axial piston pump. The developed solution is implemented on a laboratory test rig. A detailed description of the hydraulic system in the context of pump displacement control is presented, as well as the developed system architecture for its control. The control system is based on a linear-quadratic Gaussian (LQG) controller. The controller is synthesized on the basis of a model obtained by means of identification based on experimental data. The designed controller is validated through experimental studies, enabling the analysis of its performance. [ABSTRACT FROM AUTHOR]

Summary: The tuned mass damper (TMD) is widely used to mitigate vortex‐induced vibration (VIV) that approximates harmonic vibration in bridges. Robust performance is, however, still a significant concern in the VIV mitigation of bridges, especially when using a TMD with a small mass ratio. This study presents a study to apply an active tuned mass damper (ATMD) to control VIV in bridges. The control algorithm is independent of bridge parameters and can achieve real‐time tuning to the bridge motion by a few measurements. An adaptive TMD, obeying the parameter‐independent algorithm, is developed to improve its robust performance when exposed to uncertainty in the natural frequency of the bridge, and then, the ATMD is used to implement such an adaptive TMD. The ATMD control using the LQG algorithm is used as a comparison to illustrate the advantage of the parameter‐independent algorithm in the VIV mitigation of bridges. The effect of the control‐structure interaction on the control effect is also discussed. Demonstration of the method on a numerical simulation of a long‐span box‐girder bridge confirms the potential superiority of the ATMD control using the parameter‐independent algorithm in the VIV mitigation of bridges. [ABSTRACT FROM AUTHOR]

We investigated the effects of Ni concentration on hydrogen (H2) net production and nitrogen (N2) fixation rates in a model unicellular diazotrophic cyanobacterium, Cyanothece. We quantified NiFe uptake hydrogenase of the diazotroph to examine how Ni deficiency affects the expression of hydrogenase and nitrogenase and N2 fixation rates. We found that Ni availability controls its H2 net production and the expression of HupL, the major subunit of the uptake hydrogenase. Low Ni availability induced low HupL expression levels while yielding high H2 net production, and vice versa. We also identified the threshold range of Ni concentrations that may differentiate low and high H2 net production patterns in the diazotroph. However, the substantial variations in Ni availability and H2 net production did not affect nitrogenase expression and N2 fixation rates in Cyanothece. From two independent studies in the Atlantic tropical and subtropical oceans, we found that dissolved Ni concentrations and H2 oversaturation percentage exhibited a statistically significant negative correlation, which is consistent with the findings of this culture study. Overall, these results indicate that Ni availability may affect H2 net production and concentrations in the euphotic zone of the oceanic regions. H2 concentrations may be used as a promising proxy to reflect N2 fixation activities in tropical and subtropical oceans only under Ni‐deficient conditions. [ABSTRACT FROM AUTHOR]

This paper studies the agent identity privacy problem in the scalar linear quadratic Gaussian (LQG) control system. The agent identity is a binary hypothesis: Agent A or Agent B. An eavesdropper is assumed to make a hypothesis testing the agent identity based on the intercepted environment state sequence. The privacy risk is measured by the Kullback–Leibler divergence between the probability distributions of state sequences under two hypotheses. By taking into account both the accumulative control reward and privacy risk, an optimization problem of the policy of Agent B is formulated. This paper shows that the optimal deterministic privacy-preserving LQG policy of Agent B is a linear mapping. A sufficient condition is given to guarantee that the optimal deterministic privacy-preserving policy is time-invariant in the asymptotic regime. It is also shown that adding an independent Gaussian random process noise to the linear mapping of the optimal deterministic privacy-preserving policy cannot improve the performance of Agent B. The numerical experiments justify the theoretic results and illustrate the reward–privacy trade-off. [ABSTRACT FROM AUTHOR]

This paper addresses the design and analysis of path-following controllers for an autonomous underwater vehicle (AUV) using a robustness analysis framework based on integral quadratic constraints (IQCs). The AUV is modeled as a linear fractional transformation (LFT) on uncertainties and is affected by exogenous inputs such as measurement noise and ocean currents. The proposed approach leverages a learning-based method to approximate the nonlinear hydrodynamic model with a linear parameter-varying one. Additionally, modeling uncertainties are incorporated into the other subsystem models of the AUV to capture the discrepancies between the outputs of the postulated mathematical abstractions and the experimental data. The resulting uncertain LFT system adequately captures the AUV behavior within a desired envelope. Ocean current disturbances are treated as uncertainties within the LFT system and properly characterized to reduce conservatism. The robust performance level, obtained from IQC analysis, serves as a qualitative measure of a controller's performance, and is utilized in guiding the controller design process. The proposed approach is employed to design H ∞ and H 2 controllers for the AUV. A comprehensive IQC-based analysis is subsequently conducted to demonstrate the robustness of the designed controllers to modeling uncertainties and disturbances. To validate the analysis results, extensive nonlinear simulations and underwater experiments are performed. The outcomes showcase the efficacy and reliability of the proposed approach in achieving robust control for the AUV. • Uncertainties inherent to an underwater vehicle are characterized and quantified. • Deep learning is used to generate a linear approximation of the hydrodynamic model. • Robustness analysis is conducted to compare controllers. • A control tuning routine is utilized to construct robust H 2 and H ∞ controllers. • Robustness analysis results are validated through simulations and field tests. [ABSTRACT FROM AUTHOR]

Fracturing flowback fluid is the most important contaminant associated with oil and gas exploration and production, which requires low-cost and sustainable technologies for treatment. This study proposed an electrocoagulation (EC) method that is time saving, highly efficient, and easy to apply to deal with this problem. A Box-Behnken design coupled with the response surface methodology (RSM) was used to construct a model of the EC process to intensively control hydrogen (H2) production and to reduce potential safety risks while achieving high treatment efficiency. The model describes the change in the responses of decolorization rate and H2 production in accordance with electrolysis current, plate spacing, electrolysis time, and S/V. Results show that the turbidity removal rate, decolorization rate, and H2 production are predicted to be 87.03%, 89.14%, and 138.12 mL under the maximum H2 production process. On the contrary, the turbidity removal rate, decolorization rate, and H2 production are predicted to be 91.23%, 95.7%, and 7.86 mL, respectively, under minimum H2 production conditions obtained through the model. The relative error between all the predicted and measured values is less than 2.5%. Overall, the RSM is feasible to optimize and predict the process conditions, treatment effect, and H2 production of EC-treated fracturing flowback fluid. This optimization and prediction study can provide a reference for the efficient and safe application of EC to improve the treatment effect and control the H2 production in the wastewater treatment process. [ABSTRACT FROM AUTHOR]

We study linear quadratic Gaussian (LQG) control design for linear port-Hamiltonian systems. To this end, we exploit the freedom in choosing the weighting matrices and propose a specific choice which leads to an LQG controller which is port-Hamiltonian and, thus, in particular stable and passive. Furthermore, we construct a reduced-order controller via balancing and subsequent truncation. This approach is closely related to classical LQG balanced truncation and shares a similar a priori error bound with respect to the gap metric. By exploiting the non-uniqueness of the Hamiltonian, we are able to determine an optimal pH representation of the full-order system in the sense that the error bound is minimized. In addition, we discuss consequences for pH-preserving balanced truncation model reduction which results in two different classical H ∞ -error bounds. Finally, we illustrate the theoretical findings by means of two numerical examples. [ABSTRACT FROM AUTHOR]

The linear quadratic Gaussian (LQG) control for a quadrotor unmanned aerial vehicle (UAV) under false data injection attacks is studied. The LQG control depends on optimal state estimation, while this type of attacks makes the optimal state estimation unimplementable in practice. To address this problem, the authors prose a framework to detect attacks and then augment the information for controller design. Based on this framework, the LQG control is designed and a sufficient condition for the security of the closed‐loop control system is given. Finally, the LQG controller is applied to a quadrotor UAV, and some experiments are carried out to illustrate its effectiveness. [ABSTRACT FROM AUTHOR]

The radiolysis of porewaters by uranium, thorium, and potassium in mineral grains is a recognized source of molecular hydrogen in rock‐hosted and sediment‐hosted fluids. This radiolytic hydrogen is of geomicrobiological interest as a potential energy source (electron donor) for microbial metabolism, especially in energy‐limited settings such as the marine deep biosphere or the subsurface of Mars. Previous efforts to predict the production of radiolytic hydrogen from columns of rock and sediment have tended to rely upon analytic models that cannot account for the attenuation of mineral radiation by grains larger than ∼30 µm. To address this, we have developed a Monte Carlo method to simulate the physics of mineral radiation and evaluate the production of H2 as a function of mineral grain size and radioisotope composition. The results confirm that grain size is a major control on radiolytic H2 yield. For example, using the standard geological classification of grain sizes, we find that clay can produce up to an order of magnitude more H2 per unit time than sand. The magnitude of this effect is illustrated using compositional data from real geological units in order to demonstrate the dependence of radiolytic hydrogen flux on natural radionuclide concentration and bulk porosity. Key Points: Porewater radiolysis in rocks and minerals yields molecular hydrogen (H2), an energy source for microbial life on Earth and perhaps MarsOur Monte Carlo simulations of mineral radiation reveal how grain size controls H2 yield for a given radioisotope composition and porosityFor some realistic scenarios, clay‐sized grains can produce up to an order of magnitude more H2 per unit time than sand‐sized grains [ABSTRACT FROM AUTHOR]

This paper investigates the security issue of the data replay attacks on control systems with the LQG controller. The attacker tries to store measurements and replay them in further times. The main novelty in this paper is stated as proposing a different attack detection criterion under the existence of a packet-dropout feature in the network by using the Kullback-Leibler divergence method to cover more general problems and with higher-order dynamics. Formulations and numerical simulations prove the effectiveness of the newly proposed attack detection procedure. Unlike previous approaches that the trade-off between attack detection delay or LQG the performance was significant, in this approach it is proved that the difference in this trade-off is not considered in early moments when the attack happens since the attack detection rate is rapid and thus, the attacks can be stopped with defense strategies in the first moments with the proposed attack detection criterion. [ABSTRACT FROM AUTHOR]

In this article, we discuss continuous-time $\mathcal {H}_{2}$ control for the unknown nonlinear system. We use differential neural networks to model the system, then apply the $\mathcal {H}_{2}$ tracking control based on the neural model. Since the neural $\mathcal {H}_{2}$ control is very sensitive to the neural modeling error, we use reinforcement learning to improve the control performance. The stabilities of the neural modeling and the $\mathcal {H}_{2}$ tracking control are proven. The convergence of the approach is also given. The proposed method is validated with two benchmark control problems. [ABSTRACT FROM AUTHOR]

RNase H2 is a specialized enzyme that degrades RNA in RNA/DNA hybrids and deficiency of this enzyme causes a severe neuroinflammatory disease, Aicardi Goutières syndrome (AGS). However, the molecular mechanism underlying AGS is still unclear. Here, we show that RNase H2 is associated with a subset of genes, in a transcription-dependent manner where it interacts with RNA Polymerase II. RNase H2 depletion impairs transcription leading to accumulation of R-loops, structures that comprise RNA/DNA hybrids and a displaced DNA strand, mainly associated with short and intronless genes. Importantly, accumulated R-loops are processed by XPG and XPF endonucleases which leads to DNA damage and activation of the immune response, features associated with AGS. Consequently, we uncover a key role for RNase H2 in the transcription of human genes by maintaining R-loop homeostasis. Our results provide insight into the mechanistic contribution of R-loops to AGS pathogenesis. RnaseH2 is mutated in severe neuro-inflammatory disorder Aicardi‐Goutières syndrome. Here the authors reveal that RNase H2 controls cellular R-loop homeostasis to promote transcription, genome integrity and prevent R-loop-associated inflammation. [ABSTRACT FROM AUTHOR]

Simultaneous treatment of CO2 and H2S by photocatalytic technology is of great significance in mitigating the greenhouse effect and environmental hazards, while producing valuable solar fuels at the same time. In this study, well‐defined CdS/TiO2:Cu hollow spheres with highly dispersed heterointerfaces are successfully constructed for photoreduction of CO2 in presence of in situ generated H2S. Benefiting from the consumption of photo‐generated holes (h+) and large production of protons by H2S decomposition, the generation rates of CO (781.3 µmol·g−1∙h−1, accounting for 94.9 v/v% of CO2 reduction products) and H2 (5875.1 µmol·g−1∙h−1) increased significantly, which are 1.4 and 68.9 times higher than that of the system without H2S, respectively. Moreover, the remediation of photocorroded CdS by H2S prolonged the service life of the heterojunction, and maintained a CO generation rate of 96.8% after 4 cycles with or without H2S. Notably, as a potential syngas production strategy, by adjusting the initial concentration of Na2S, the ratio of CO and H2 is controlled from 1.07 to 7.21 to fulfill the demands of different chemical synthesis. This strategy opens up a new horizon for the combination of energy photocatalysis and environmental photocatalysis, which has great research and application prospects. [ABSTRACT FROM AUTHOR]

In the paper, the Linear–Quadratic–Gaussian (LQG) control strategy in regulatory mode (disturbance attenuation, zero value of the reference signal) in single-loop control is used to stabilize the system equipped in a non-integer order plant. The influence of the optimal controller design sophistication on control quality in terms of output variance is examined. It has been shown that the optimal implementation length of fractional-order difference is relatively low (several dozen in considered examples). Therefore, further increasing the controller's complexity in terms of approximation length does not improve the control performance. Furthermore, it is presented that, under bounded control signal variance, the optimal fractional order of the controller may be significantly different from the actual fractional order of the plant (in the examples, the difference is up to 0.66). [ABSTRACT FROM AUTHOR]

Summary: In this study, an optimal design of a tuned viscous mass damper (TVMD) incorporated into a single‐degree‐of‐freedom structure system subjected to earthquake‐induced random vibrations is studied. Closed‐form design formulas of the optimal frequency ratio and damping ratio are proposed for the control of structural displacement and acceleration responses based on H2 norm optimization. The optimal solutions exist when the mass ratio is smaller than 0.11. The calculated optimal parameters for displacement control and acceleration control are close to each other, which indicates that the displacement and acceleration responses can be controlled simultaneously with the TVMDs designed by the easy‐to‐use formulas proposed in this study. To expand the use of the proposed formulas for cases with large mass ratios, the alternative suggested design (ASD) is proposed to explicitly represent the recommended relationships between the design parameters. This paper also examines the control effect of a TVMD over linear viscous dampers, defining an efficiency index as a ratio of the response yielded by a TVMD system to that of a viscous damper system. The optimally designed TVMD is generally more efficient than directly adding damping with viscous dampers when the mass ratio is small, while this advantage is insignificant when the mass ratio grows. Based on this outcome, a new method termed efficiency‐based design is proposed. This user‐friendly method can assist practicing engineers in determining the mass ratio, the frequency ratio, and the damping ratio of TVMDs. [ABSTRACT FROM AUTHOR]

Design of effective control strategies to protect structural buildings from seismic hazards is gaining increasing attention. In this paper, an intelligent semiactive control strategy, which combines linear-quadratic-Gaussian (LQG), whale optimization algorithm (WOA), and adaptive neuro-fuzzy inference system (ANFIS) strategy is designed to mitigate structural vibration by using magnetorheological (MR) dampers, here known as WLQG-ANFIS control. Firstly, considering that the performance of the LQG control for the structures under seismic excitations strongly depends on skill and experience of the experts in determining the weighting matrix of the feedback gain, a WOA with constraints is adopted to optimally design the LQG control due to the strong ability to avoid local optima. Secondly, the inverse dynamic model of the MR damper is developed with the ANFIS technique which combines the fuzzy system and artificial neural network. Finally, according to the active force estimated by the proposed LQG control, the developed inverse model is utilized to calculate the MR damper command signal. Numerical analyses are conducted for a 10-story structural building installed with MR dampers under earthquake excitation. Through a test called analysis of variance in optimizing the LQG control, the superiority of WOA over other three meta-heuristic algorithms, i.e. GA, DE, and ABC, in terms of convergence performance and robustness is validated. The proposed WLQG-ANFIS control can reduce the maximum displacement, interstory drift and acceleration responses by 64%, 65%, and 53%, respectively, which can achieve better overall performance than on-off control, LQG-ANFIS control, fuzzy control, and H∞-ANFIS control. Moreover, this control strategy exhibits the ability to handle the uncertainties in structural parameters as well as seismic excitations. [ABSTRACT FROM AUTHOR]

Elastic vibration can arise in annular and thin-walled rotor structures, impacting on operating performance and the risk of failure. Feedback control to reduce flexural vibration can be realized using lightweight actuators and sensors embedded in the rotor structure. To design optimal controllers, rotating-frame models of both the structural dynamics and sources of excitation are required. This paper describes a solution to this problem for the case of an annular rotor equipped with piezo patch actuators and sensors. To account for space-fixed external excitation sources, a forcing function is considered involving specified spatial and frequency domain distributions. A model-based H 2 synthesis is used to compute optimal control solutions. These are tested experimentally on a thin-walled cylindrical steel rotor for cases with narrowband and broadband excitation sources, applied from the fixed frame. The results show that frequency-splitting within the rotating-frame dynamics plays a key role in predicting and controlling resonance. The effectiveness of the optimal control methodology in reducing circumferential vibration of the annular rotor is also confirmed. [ABSTRACT FROM AUTHOR]

Plenty of studies focused on single-direction active suspensions on railway vehicles; at least four actuators per vehicle are needed forconventional active secondary suspensions in both lateral and vertical directions, leading to a sharp increase in costs and reduction inreliability. This paper proposes a novel configuration, lateral-vertical coupled (LVC) active secondary suspension, with only two actuators and two accelerometers per vehicle. To deal with the coupled dynamics, linear quadratic Gaussian (LQG) method and optimal skyhook damping (OSD) method are developed for achieving optimal control. OSD method has similar advantages as LQG method and is easier to implement. Then, linearised vehicle dynamics is modelled to design the controllers and observer, and a more complete nonlinear simulation model is established for verification. Theoretical analysis and simulation results show that LVC active suspension reduces car body vibration in one direction at the cost of negative effects in the other. LQG control fails to provide satisfying performance compared with passive suspensions, whereas OSD control can effectively improve lateral and vertical vibration and ride comfort by applying reasonable actuator forces. Besides, actuator dynamics is important to the effectiveness of LVC active suspension, and OSD controller is robust to measurement noise and model errors to some extent. [ABSTRACT FROM AUTHOR]

In this paper a flexible smart wing is presented. The aileron wing with aileron was tested in the INCAS Subsonic Wind Tunnel with the aim of flutter mitigation and vibrations attenuation. The work takes over some of the results of the active anti-flutter control tests performed in the wind tunnel based on the receptance method. More specifically, the mathematical models in the time domain, necessary for the synthesis of control laws, are obtained from experimentally identified transfer functions. The main part of the paper presents the synthesis and analysis of the robustness of the control laws LQG, LQG/LTR, 𝐻𝐻∞ standard and 𝐻𝐻∞ robust from which the optimal solution will be chosen in a later work for the active vibration control tests on this smart wing model. [ABSTRACT FROM AUTHOR]