H2 Control Research Articles

Drinking hydrogen water improves photoreceptor structure and function in retinal degeneration 6 mice

Retinitis pigmentosa (RP) is a genetically heterogeneous group of inherited retinal disorders involving the progressive dysfunction of photoreceptors and the retinal pigment epithelium, for which there is currently no treatment. The rd6 mouse is a natural model of autosomal recessive retinal degeneration. Given the known contributions of oxidative stress caused by reactive oxygen species (ROS) and selective inhibition of potent ROS peroxynitrite and OH·by H2 gas we have previously demonstrated, we hypothesized that ingestion of H2 water may delay the progression of photoreceptor death in rd6 mice. H2 mice showed significantly higher retinal thickness as compared to controls on optical coherence tomography. Histopathological and morphometric analyses revealed higher thickness of the outer nuclear layer for H2 mice than controls, as well as higher counts of opsin red/green-positive cells. RNA sequencing (RNA-seq) analysis of differentially expressed genes in the H2 group versus control group revealed 1996 genes with significantly different expressions. Gene and pathway ontology analysis showed substantial upregulation of genes responsible for phototransduction in H2 mice. Our results show that drinking water high in H2 (1.2–1.6 ppm) had neuroprotective effects and inhibited photoreceptor death in mice, and suggest the potential of H2 for the treatment of RP.

Guaranteed consensus performance in second-order networked multi-agent systems with induced delay

This work described the performance of consensus control of the second-order networked multi-agent system with CAN bus-induced delay. First, the characteristics of controller area networks (CAN) buses and the main causes of CAN bus induce a delay in distributed networked control systems (DNCS) were analysed. Secondly, DNCS is converted into a model of networked multi-agent systems in the frequency domain. Then based on the designed model of networked multi-agent systems, an analytical H2 controller is proposed for performance tracking. Moreover, a complementary sensitivity function is used to assess the robustness of the proposed controller. In the end, delay margin criteria are derived for the consensus of a networked multi-agent system in the presence of CAN bus-induced delay. The results obtained by simulating the second-order networked multi-agent system verified the usefulness of the proposed control protocol.

An optimal H 2 controller based on vibration energy minimization for a horizontal vibration isolator supported by air bearings

To suppress various interferences in the active vibration control process simultaneously, an optimal H2 control method based on vibration energy minimization is proposed in this paper. The interference sources mainly include floor vibration interference, direct interference, and sensor noise as well as electrical noise and quantization noise of the analog to digital and digital to analog converters. The interferences are modeled by weighting filters and the load vibration is weighted by a scaling filter, both of which are introduced into the design of the system’s H2 controller. Thus, the load vibration energy is equivalent to the H2 norm of the system. This method can minimize the total impact of external interferences and improve the vibration isolation performance of the system. Compared with the traditional proportional integral derivative control method, it significantly reduces the root-mean-square value of the load vibration. Simulation and experimental results verify the effectiveness of the proposed control method.

Design and validation of reactant feeding control strategies for the solar-autothermal hybrid gasification of woody biomass

Several hybridization strategies of a solar-autothermal biomass gasifier were examined for stable and continuous operation under variable solar irradiation. The ultimate objective was to demonstrate the feasibility of controlled syngas production, through the modification of oxygen, water, and biomass injection rates. Various hybridization strategies were probed by thermodynamic analysis and experimentally validated. Thermodynamic equilibrium calculations detailed the impact of both H2O and O2 injection rates on the produced syngas composition under constant wood feeding. Oxygen injection decreased the H2:CO molar ratio, while reducing the solar thermal power required to carry out the gasification reaction. Meanwhile, the total H2+CO production dropped by 1.36 mol of H2 and 0.64 mol of CO per mole of O2 added, independently of the quantity of water provided. Validation experiments were then carried out under real concentrated solar flux in a directly-irradiated conical spouted-bed reactor, following distinct hybridization paths. Maintaining constant the H2:CO ratio above 1 during hybridization required to provide high amounts of water steam with oxygen, which penalized the gasifier efficient heating. In contrast, minimizing the water injection rate throughout hybridization strongly altered the H2:CO ratio but decreased the CO2 production and the solar thermal power requirement. Finally, the successful control of the outlet H2+CO volume flow rate with simultaneous oxygen and wood injection was demonstrated (under constant water feeding rate). Solar-to-fuel efficiencies were kept around 20%, while hybridization decreased the cold-gas efficiency below 80%.

Neural H₂ Control Using Continuous-Time Reinforcement Learning.

In this article, we discuss continuous-time H2 control for the unknown nonlinear system. We use differential neural networks to model the system, then apply the H2 tracking control based on the neural model. Since the neural H2 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 H2 tracking control are proven. The convergence of the approach is also given. The proposed method is validated with two benchmark control problems.

The generalized [formula omitted] controller synthesis problem of sampled-data systems

This paper tackles the generalized H2 controller synthesis problem of sampled-data systems, which is associated with the controller minimizing the induced norm from L2 to L∞. To alleviate the difficulty of the linear periodically time-varying (LPTV) nature of sampled-data systems, we first take an operator-based approach to sampled-data systems via the lifting treatment. We next develop a framework for piecewise constant approximation in the context of the generalized H2 controller synthesis problem after further applying the so-called fast-lifting treatment. An optimal controller for the approximate treatment is also shown to achieve the generalized H2 performance for the sampled-data system that is close enough to its optimal generalized H2 performance, if the fast-lifting parameter N is large enough. This is established by deriving, in a fashion suitable for controller synthesis, upper and lower bounds on the resulting sampled-data generalized H2 performance, where their gap tends to 0 at the rate of 1/N. We further introduce a discretization method of the continuous-time plant, with which the controller synthesis in the approximate fashion can actually be carried out through an equivalent discrete-time counterpart of the generalized H2 controller synthesis problem. Finally, numerical examples are given to validate the overall arguments.

Improved ℋ2 and ℒ2 control designs for discrete-time LPV/LFR systems

This paper addresses novel and norm-based controller designs for discrete-time linear parameter-varying (LPV) systems with linear fractional representation (LFR). Despite the importance of LPV/LFR systems to the control literature, there is a lack of works on this topic. The distinctive formulation of the proposed controller designs is given by using parameter-dependent Lyapunov functions in combination with slack variables and general full-block multipliers. Such proposed formulation leads to less conservative synthesis conditions characterised in terms of a finite number of linear matrix inequalities for both state-feedback and static output-feedback controllers subject to and performances for discrete-time LPV/LFR systems. Improvements obtained by the proposed controller design conditions over existing methods in the area are assessed by numerical examples.

Pyrolysis-catalytic steam/dry reforming of processed municipal solid waste for control of syngas H2:CO ratio

The production of syngas from the pyrolysis-catalytic reforming of processed municipal solid waste in the form of refuse derived fuel has been investigated experimentally using a two-stage fixed bed reactor with a 10 wt% Ni–Al2O3 catalyst. The reforming gases used were a combination of steam and carbon dioxide (dry reforming). The main focus of the research was to manipulate the H2:CO ratio in the syngas for targeted end-use applications by optimizing the process conditions, including the input steam/CO2 reforming gas ratio. The experimental results showed that at higher steam:CO2 ratios, there was a marked increase in H2 yield due to the endothermic nature of the steam and CO2 reforming processes. The catalytic reforming temperature also had a major influence on H2 yield, with increasing temperature raising the hydrogen yield to a maximum of ∼41.0 mmol gRDF−1 at 955 °C catalyst temperature. The H2:CO molar ratio was also affected by the process variables and were interdependent on them. For example, the influence of an increase in the catalytic reforming temperature as the content of steam in the reforming gas input was also increased, produced a maximum H2:CO molar ratio of ∼4.7:1 achieved at an input steam:CO2 ratio of 75:25 and a catalyst temperature of 700 °C. Whereas, at higher CO2 content in the reforming gas, the product H2:CO ratio was ∼1:1. Also, for a steam:CO2 input ratio of 50:50, the H2:CO ratio produced was ∼2:1 and for higher steam content in the reforming gas the product H2:CO was ∼3:1. Design of Experiments (DoE) modelling was carried out using the experimental data to identify the process conditions that would produce a target syngas H2:CO molar ratio of 1:1 and 2:1. The predicted optimised process conditions from the DoE modelling produced experimental results close to the targeted syngas H2:CO molar ratios, thereby validating the DoE model.

Robust gain-scheduled output feedback H2 controller synthesis with reduced conservativeness: An application to EMS system

This article investigates the design problem of gain-scheduled output feedback (GSOF) [Formula: see text] controller exploiting uncertain scheduling parameters for continuous-time linear parameter-varying (LPV) systems. The problem of coexistence of absolute and proportional uncertainties on the scheduling parameters is considered to address more practical situations. This challenging issue has been tackled by introducing a novel admissible region for the actual and measured scheduling parameters. Furthermore, all the system matrices of the LPV system are assumed to be polynomially dependent on the scheduling parameters with arbitrary degrees. Both Lyapunov and auxiliary matrices are considered to be parameter-dependent. The merit of the proposed method lies in its less conservativeness in comparison with the available approaches. The design method is presented in terms of solutions to a set of parameter-dependent linear matrix inequalities (LMIs) including parameter searches for two scalar values. The application of the provided method on an electromagnetic suspension (EMS) system is considered to demonstrate the applicability and benefits of the proposed approach for practical systems.

Research on time-delay-dependent H∞/H2 optimal control of magnetorheological semi-active suspension with response delay

Considering the influence of the magnetorheological damper response time delay on the low-frequency vibration (body vibration) and multi-objective control requirements of the semi-active suspension system, a novel H∞/H2 controller (time-delay-dependent H∞/H2 optimal controller) is proposed in this paper. Based on the Lyapunov–Krasovskii function and robust control theory, a time-delay-dependent H∞/H2 controller in consideration of the MR damper response time delay is designed to reduce and remove the effects of time delay on the semi-active suspension system. To obtain better suspension control performances, the optimal selection strategy of anti-interference coefficients in the time-delay-dependent H∞/H2 controller is proposed. Then, the time-delay-dependent H∞/H2 optimal controller is structured built on the optimal selection strategy. With the application of matrix properties and the cone-compensation linearization algorithm, the nonlinear matrix inequality for controller design is linearized, and the feedback gain matrix of the controller is solved iteratively. Finally, comparative simulation and experimental research are conducted to verify the effectiveness and superiority of the designed optimal controller.

Generalized H2 control of discrete‐time semi‐Markov jump systems

AbstractThis 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.

Optimal Active Vibration Isolation System Design using Constrained H2 control.

Active vibration isolation systems can increase the performance over passive vibration isolation systems by mitigating the trade-off in sensitivity to direct and indirect disturbances. However, the potential performance improvement, as well as the optimal system design are not yet fully understood. This paper proposes an optimal system design method based on constrained H2 control and parametrized mechanics, where the disturbance spectra of the floor vibrations, actuator and sensing noise are explicitly taken into account. Using this method, the optimal system parameters, as well as the potential performance improvement can be quantified. This method is applied to a case study to show its usefulness. From this case study, and the thereby imposed constraints, it can be concluded that AVIS can significantly improve the performance for all considered direct disturbance powers.

Stabilization of an arbitrary order transfer function with time delay H2 Controller

Stabilization of an arbitrary order transfer function with time delay H2 Controller

Full Information H2 Control of Borel-Measurable Markov Jump Systems with Multiplicative Noises

This paper addresses an H2 optimal control problem for a class of discrete-time stochastic systems with Markov jump parameter and multiplicative noises. The involved Markov jump parameter is a uniform ergodic Markov chain taking values in a Borel-measurable set. In the presence of exogenous white noise disturbance, Gramian characterization is derived for the H2 norm, which quantifies the stationary variance of output response for the considered systems. Moreover, under the condition that full information of the system state is accessible to measurement, an H2 dynamic optimal control problem is shown to be solved by a zero-order stabilizing feedback controller, which can be represented in terms of the stabilizing solution to a set of coupled stochastic algebraic Riccati equations. Finally, an iterative algorithm is provided to get the approximate solution of the obtained Riccati equations, and a numerical example illustrates the effectiveness of the proposed algorithm.

Robust H2 output-feedback bumpless transfer control of polytopic uncertain LPV systems

The problem of Robust Switching Gain-Scheduled Output-Feedback (RSGSOF) H2 controller synthesis with control bumps limitation is tackled in this paper for polytopic uncertain continuous-time linear parameter varying (LPV) systems. The presented robust switching gain-scheduled control design scheme overcomes the limitation of existing methods based on single quadratic Lyapunov function. However, in practice, RSGSOF controller leads to expressive discontinuities at switching instants. Hence, we aim to investigate of H2 output-feedback Bumpless Transfer Controller (BTC) design problem. In this study, not only stability and an upper bound on the H2-norm performance of the closed-loop system can be guaranteed but also solvability conditions are incorporated in the synthesis procedure to reduce control bumps. The proposed BTC composes multiple LPV controllers with the bumps limitation objective and a Lyapunov-based min-switching rule governing the switching among these controllers. Numerical studies demonstrate the effectiveness of the proposed approach.

Formula omitted]-optimal vibration control using receptance-based regional eigenvalue assignment

This paper proposes a method of H2-optimal vibration control using regional eigenvalue assignment based only on measured receptances, typically from a modal test. The sum of the squared weighted H2-norm of closed-loop receptance matrix and the transfer matrix from the external input to the control input is minimized by exploiting the flexibility from assigning the closed-loop eigenvalues to prescribed stable regions with single- or multiple-input control. It is found that regional eigenvalue assignment and the optimization of a free parameter matrix (in the multiple-input case) provide extra flexibility for improving the closed-loop performance over and above the selection of weighting matrices, as in standard H2 control. Therefore, the internal stability, satisfactory response, and minimum control energy are readily guaranteed by the proposed method, whereas the standard approach is dependent upon the arbitrarily chosen weighting matrices. The method inherits the advantages of both optimal control and eigenvalue assignment by the receptance method. The working of the method and its advantages over the standard H2 control are demonstrated numerically.

Design and Implementation of LMI-Based H2 Control for Vertical Nonlinear Coupled-Tank System

This paper presents the mathematical design and implementation of a robust H_2 output feedback controller for the vertical nonlinear coupled-tank system. Considering the growth of the complicated chemical processes in industries in the last decades, the necessity for the controllers with high robustness and proficiency is demanded. Therefore, to overcome some deficiencies of classical controllers such as Proportional Integral (PI), the robust H_2 output feedback controller is proposed to control the liquid level of the coupled tank system benchmark. Because of the nonlinearity of the system and the interactions between two tanks, the behavior of the controller in terms of the performance and disturbance rejection is on the main scene. The Linear Matrix Inequalities (LMI) is used to derive the design procedure. The effectiveness of the proposed approach in the setpoint tracking is highlighted in comparison with the PI plus feedforward controller and the acceptable results are achieved.

ROBUST FINITE-TIME SUPOPTIMAL CONTROL OF LARGE-SCALE SYSTEMS WITH INTERACTED STATE AND CONTROL DELAYS

This paper is concerned with a problem of supoptimal nite-time control for a class of linear large-scale delay systems. The system under consideration is subjected to the state and control delays interacted between subsystems. Based on improved LMI-based approach combining with new estimation techniques, we derive sucient conditions for solving nite-time H1 control and guaranteed cost control of the system. Numerical examples are given to illustrate the validity and eectiveness of the theoretical results.

Design and Implementation of LMI-based H2 Control for Vertical Nonlinear Coupled-tank System

This paper presents the mathematical design and implementation of a robust H_2 output feedback controller for the vertical nonlinear coupled-tank system. Considering the growth of the complicated chemical processes in industries in the last decades, the necessity for the controllers with high robustness and proficiency is demanded. Therefore, to overcome some deficiencies of classical controllers such as Proportional Integral (PI), the robust H_2 output feedback controller is proposed to control the liquid level of the coupled tank system benchmark. Because of the nonlinearity of the system and the interactions between two tanks, the behavior of the controller in terms of the performance and disturbance rejection is on the main scene. The Linear Matrix Inequalities (LMI) is used to derive the design procedure. The effectiveness of the proposed approach in the setpoint tracking is highlighted in comparison with the PI plus feedforward controller and the acceptable results are achieved.

Time delay compensation control using a Taylor series compound robust scheme for a semi‐active suspension with magneto rheological damper

AbstractTime delay significantly degrades the control performances of semi‐active magneto rheological damper. However, the robust control approaches combined with the Taylor series are difficult to perform time delay compensation because it has strict application conditions. In this study, two Taylor series compound robust control schemes are presented to address the robust control and time delay compensation problems for the semi‐active magneto rheological damper with time delay. The formulation of a quarter vehicle model with a magneto rheological damper is described by a hyperbolic tangent model. Given the mechanical characteristics, an experimental test was conducted to fit the hyperbolic tangent model parameters. As a prototype, the Taylor series‐H2/H∞ control approach is proposed through establishing a first‐order Taylor series‐delay equation in augmented state equation and using the H2/H∞ norms to constrain the predictive control force. Moreover, the Taylor series‐H2/H2 controller is proposed to reduce the conservatism and suppress the predictive control force amplification. Simulation results corroborate the efficacy of both control strategies. Specifically, compared with the Taylor series‐H2/H∞ control, the Taylor series‐H2/H2 control can obtain a better control effect for time delay compensation.