H2 Control Research Articles

Intelligent method for tuning H2 PID controller of water hydraulic manipulator of CFETR blanket maintenances

Purpose – The purpose of this paper is to investigate an intelligent control for water hydraulic position servo system which is intent to be used in remote control robot for fusion reactor. The dynamic model of water hydraulic servo control system is built and proportional–integral–derivative (PID) controller is used. Design/methodology/approach – PID control is the most common control algorithm used in industry and has been a conventional tool used to operate closed-loop control system; however, it is very difficult to achieve high accuracy and fast response by using the traditional way to tune its perimeters. To improve the control performance, optimization algorithm can be applied to search the best parameters of PID. This paper presents a search algorithm using particle swarm with H2 control standards objective function to optimize PID parameters. Findings – By comparing simulation and mock-up experiments’ results from different control methods, the particle swarm optimization algorithm presents better performance and is more effective for tuning PID parameters. Originality/value – This paper presents an effective way to ensure safety and efficiency for remote handling maintenances of China Fusion Engineering Test Reactor.

Optimal LPV control with hard constraints

This paper considers the optimal control of polytopic, discrete-time linear parameter varying (LPV) systems with a guaranteed l2 to l∞ gain. Additionally, to guarantee robust stability of the closed-loop system under parameter variations, H∞ performance criterion is also considered as well. Controllers with a guaranteed l2 to l∞ gain and a guaranteed H∞ performance (l2 to l2 gain) are a special family of mixed H2=H∞ controllers. Normally, H2 controllers are obtained by considering a quadratic cost function that balances the output performance with the control input needed to achieve that performance. However, to obtain an optimal controller with a guaranteed l2 to l∞ gain (closely related to the physical performance constraint), the cost function used in the H2 control synthesis minimizes the control input subject to maximal singular-value performance constraints on the output. This problem can be efficiently solved by a convex optimization with linear matrix inequality (LMI) constraints. The main contribution of this paper is the characterization of the control synthesis LMIs used to obtain an LPV controller with a guaranteed l2 to l∞ gain and >H∞ performance. A numerical example is presented to demonstrate the effectiveness of the convex optimization.

Reduced basis method for H2 optimal feedback control problems

In this paper we examine the application of recently introduced parametric model reduction techniques to the H2 optimal feedback control problem. The H2 control problem provides a realistic framework for control applications, since it considers disturbances in the system and in the measurement outputs. Furthermore it employs state-estimation to reconstruct the unknown state from the noisy measurements. It turns out, that the controller is a dynamical system and two solutions of algebraic Riccati equations (AREs) are required to form it. We apply parametric model order reduction techniques to the AREs and to the state equation of the observer and show by numerical examples, that this approach can yield a significant speed-up in multi-query scenarios for large scale parametric problems for the control of partial differential equations (PDE).

A new look at the robust control of discrete-time Markov jump linear systems

ABSTRACTIn this paper, we make a foray in the role played by a set of four operators on the study of robust H2 and mixed H2/H∞ control problems for discrete-time Markov jump linear systems. These operators appear in the study of mean square stability for this class of systems. By means of new linear matrix inequality (LMI) characterisations of controllers, which include slack variables that, to some extent, separate the robustness and performance objectives, we introduce four alternative approaches to the design of controllers which are robustly stabilising and at the same time provide a guaranteed level of H2 performance. Since each operator provides a different degree of conservatism, the results are unified in the form of an iterative LMI technique for designing robust H2 controllers, whose convergence is attained in a finite number of steps. The method yields a new way of computing mixed H2/H∞ controllers, whose conservatism decreases with iteration. Two numerical examples illustrate the applicability of the proposed results for the control of a small unmanned aerial vehicle, and for an underactuated robotic arm.

Spacecraft maneuvers via singularity-avoidance of control moment gyros based on dual-mode model predictive control

Attitude control is investigated for a rigid spacecraft using single gimbal control moment gyros (SGCMGs) as actuators. By taking spacecraft and SGCMGs as an integrated system, the combined dynamics of SGCMGs and spacecraft are fully considered. The singularity problem of the SGCMGs is converted into the problem of state constraints and input constraints, and by so doing, the actuation capacity of the SGCMGs is fully utilized. To ensure accurate real-time computation, the Gauss pseudospectral and sequential quadratic programming methods are used to solve the attitude path planning of the system. Considering the uncertainties of the external disturbances and the estimation error of the inertia matrix, feedback control of the system is designed by using nonlinear model predictive control. Finally, dual-mode model predictive control is used to ensure the stability of the system, and the H8 controller and the estimated hyperellipsoid region of attraction of the linearized system are given. Simulation results show good tracking performance and robustness of the designed controller. The modeling method and the control method given in the paper provide a solution to the singularity problem of the SGCMGs.

A mixed H2/passivity performance controller design for a drum-boiler system

The mixed performance control problem of drum-boiler systems is discussed and investigated in this paper, subject to H2 and passivity performances. In order to minimize output energy and guarantee asymptotical stability, an H2 control scheme is employed to solve the stability problem of system. Passivity theory is applied to achieve disturbance attenuation performance. Based on the Lyapunov function, some sufficient conditions are derived into linear matrix inequality (LMI) form to apply a convex optimization algorithm. Based on the derived sufficient conditions, the asymptotical stability and mixed H2/Passivity performance of the system is achieved by the designed controller. Finally, some simulation results are proposed for a drum-boiler system with external disturbance in order to verify the validity and effectiveness of the proposed design method.

An Advanced Robust AVR-PSS Based H2 and H∞ Frequency Approachs Simulated Under a Realized GUI

This article present a comparative study between two advanced robust frequency control strategies and their implementation using our realised Graphical User Interface ‘GUI’ under MATLAB software: the first method based on loop-shaping H∞ optimization technique and the second on robust H2 control method (LQG controller associated with KALMAN filter), and applied on automatic excitation control of synchronous generators, to improve transient stability and robustness of a single machine- infinite bus (SMIB) system operating in different several conditions. The computer simulation results (static and dynamic stability), with test of robustness against machine parameters uncertainty (electric and mechanic), have proved that good dynamic performances, showing a stable system responses almost insensitive to large parameters variations, and more robustness using robust H∞ controller in comparison with H2 approach by exploiting our developed GUI interface in this work.

An Advanced Robust AVR-PSS Based H2 and H∞ Frequency Approachs Simulated Under a Realized GUI

This article present a comparative study between two advanced robust frequency control strategies and their implementation using our realised Graphical User Interface ‘GUI’ under MATLAB software: the first method based on loop-shaping H∞ optimization technique and the second on robust H2 control method (LQG controller associated with KALMAN filter), and applied on automatic excitation control of synchronous generators, to improve transient stability and robustness of a single machine- infinite bus (SMIB) system operating in different several conditions. The computer simulation results (static and dynamic stability), with test of robustness against machine parameters uncertainty (electric and mechanic), have proved that good dynamic performances, showing a stable system responses almost insensitive to large parameters variations, and more robustness using robust H∞ controller in comparison with H2 approach by exploiting our developed GUI interface in this work.

LMI-based H2 Control for T-S Fuzzy System with Hard Constraints

For T-S fuzzy systems with hard constraints and disturbances modeled by impulses, a constrained H2 control scheme in the framework of LMI (Linear Matrix Inequality) optimization is proposed in this paper. First, the H2 norm is chosen as measurement of disturbance attenuation level, and sufficient conditions for guaranteeing an H2 performance are given. Then, under the bound assumption of the disturbance energy, another fixed ellipsoid containing all perturbed trajectories is confirmed. Finally, hard constraints are enforced and translated into LMI conditions. The multi-objective design is lead to solving an optimization problem with LMI constraints. Simulation results for application in TORA system are discussed.

H2 O2 activates matrix metalloproteinases through the nuclear factor kappa B pathway and Ca(2+) signals in human periodontal fibroblasts.

The mechanisms involved in reactive oxygen species and matrix metalloproteinase (MMP)-mediated periodontal tissue breakdown are unknown. To determine the effect of H2 O2 in MMP-2 and MMP-9 activity, and the involvement of nuclear factor kappa B (NFκB) and Ca(2+) -mediated signals in human periodontal ligament fibroblasts. Primary cultures were characterized for their phenotype and exposed for 24 h to sublethal doses (2.5-10 μm) of H2 O2 or control media. NFκB involvement was evaluated through immunofluorescence of p65 subunit, using the NFκB blocking peptide SN50 and catalase. Ca(2+) signals were analyzed by loading the cells with Fluo4-AM and recording the fluorescence changes in a confocal microscope before and after the addition of H2 O2 . 1,2-bis(o-aminophenoxy) ethane-N,N,N',N'-tetraacetic acid-acetoxymethyl was used to chelate intracellular Ca(2+) . The activity and levels of MMP-2 and MMP-9 were analyzed by gelatin zymogram and densitometric scanning, and enzyme-linked immunosorbent assay, respectively. Statistical analysis was performed with stata V11.1 software using the ANOVA test. H2 O2 at concentrations of 2.5-5 μm induced Ca(2+) signaling and NFκB subunit p65 nuclear translocation, whereas catalase, SN50 and BAPTA-AM prevented p65 nuclear translocation. H2 O2 at 2.5-5 μm significantly increased MMP-9 and MMP-2 activity, while SN50 resulted in lower MMP-2 and MMP-9 activity rates compared with controls. Sublethal H2 O2 induces Ca(2+) -dependent NFκB signaling with an increase in MMP gelatinolytic activity in human periodontal ligament.

Control of vehicle suspension using an adaptive inerter

In this paper, we study the suspension performances with an adaptive inerter under the assumption that the inertance may be adjusted in real-time. A quarter-car model with an inerter installed in parallel with a spring and a damper is considered. First, for a given suspension system, a study of the effects of using a fixed inerter is provided. It shows the difficulty in choosing a fixed inerter to satisfy the vehicle performances at the sprung mass natural frequency without deteriorating significantly at the unsprung mass natural frequency. Then, a state-feedback H2 controller for an active suspension system is designed. The active force is approximated by an inerter with adjustable inertance. Ride quality, suspension deflection and tyre deflection performances are considered independently as the prime objective. Simulation results show that comparing with the passive suspension with fixed inerter, for ride quality and tyre deflection, the suspension with adaptive inerter can achieve improvement at the sprung mass natural frequency at the expense of a relatively small deterioration at the unsprung mass natural frequency. For suspension deflection, a better performance can be achieved at high frequencies with almost no loss of performance at other frequencies. This method is easier to implement in practice than the optimized passive suspension with a fixed inerter, which calls for complicated layout.

Mixed H2/H∞ decentralized fuzzy tracking control design for a flexible air-breathing hypersonic vehicle

This article addresses the problem of mixed H2/ H∞ decentralized fuzzy tracking control design for a flexible air-breathing hypersonic vehicle, which includes the intricate coupling between the engine and flight dynamics as well as the complex interplay between the flexible and rigid modes. Initially, the nonlinear longitudinal model of the flexible air-breathing hypersonic vehicle is represented as a nonlinear large-scale interconnected system, which can be described by a Takagi–Sugeno fuzzy model. Then, based on the decentralized Takagi–Sugeno fuzzy model, a mixed H2/ H∞ decentralized fuzzy tracking controller is developed to not only ensure the stability of the whole nonlinear interconnected system but also achieve the suboptimal H2 control performance under a desired H∞ disturbance attenuation level. Furthermore, the problem of mixed H2/ H∞ decentralized fuzzy tracking control design is characterized in terms of a set of linear matrix inequalities. Finally, simulation results on the flexible air-breathing hypersonic vehicle demonstrate the effectiveness and merit of the proposed design method.

A longitudinal flight control law based on robust MPC and H2 methods to accommodate sensor loss in the RECONFIGURE benchmark

The feedback gains in state-of-the-art flight control laws for commercial aircraft are scheduled as a function of values such as airspeed, mass, and centre of gravity (CoG). If estimates of these are lost due to multiple simultaneous sensor failures, the pilot must revert to an alternative control law, or, in the ultimate case, directly command control surface positions. This work develops a robust backup load-factor tracking control law, that does not depend on these parameters, based on application of theory from robust MPC and H2 control. Firstly, the methods are applied with loss only of airdata, and subsequently also with loss of mass and CoG estimates. Local linear analysis indicates satisfactory performance over a wide range of operating points. Finally, the resulting control laws are demonstrated on the nonlinear RECONFIGURE benchmark, which is derived from an Airbus high fidelity, industrially-validated simulator.

Fault Tolerance of Cooperative Vehicle Platoons Subject to Communication Delay

Cooperative Adaptive Cruise Control (CACC) employs wireless intervehicle communication to allow for automatic vehicle following at small intervehicle distances while guaranteeing string stability. Inherent to the CACC concept, however, is its vulnerability to communication impairments, among which latency of the wireless link, which compromise string stability and, hence, safety. To investigate the sensitivity of the string stability property with respect to communication latency, two controllers are developed by means of H8 controller synthesis, employing a one-vehicle look-ahead and a two-vehicle look-ahead communication topology, respectively. The string stability properties of the controlled vehicle platoon are investigated, based on which it is proposed to switch from one-to two-vehicle look-ahead when the latency exceeds a certain threshold, thereby creating robustness against increasing communication delay by retaining string stability at the lowest possible time gap.

Load-dependent LPV/H<SUB align="right">2 output-feedback control of semi-active suspension systems equipped with MR damper

This paper is concerned with the problem of load-dependent H2 control for vehicle semi-active suspension. A quarter-car model equipped with a magnetorheological (MR)-damper, which captures essential features of a real car suspension, is considered in this study. H2-norm measures the root-mean-square (RMS) value of output to white noise input. Considering the fact that road roughness is often modelled as white noise, H2-norm is used to quantify control objectives of ride comfort and safety as well as suspension deflection and control effort. To guarantee system performance against parameter variations, a linear matrix inequality (LMI)-based design framework has been utilised and a linear parameter-varying (LPV) controller is synthesised. The design procedure of the semi-active suspension requires the inverse dynamics of MR damper, which is obtained through a locally linear neuro-fuzzy (LLNF) network. To illustrate the effectiveness of the proposed approach, the system outputs for both impulse and real road inputs are compared with H∞ controller in terms of performances.

H2 control design of Lur’e type switched systems

This paper deals with H2 control design of Lur’e-type switched systems through a generalization of the Popov criterion. More specifically, a state-input dependent switching rule is proposed in order to assure global asymptotic stability and H2 guaranteed cost. This new switching strategy is the key point to generalize the celebrated Popov criterion. Likewise the case of time invariant systems, we propose a frequency domain stability test that is expressed in terms of a certain convex combination of the subsystems state space matrices. Moreover, this test takes into account an H2 performance index whose study in the present context is novel in the literature. The theory is illustrated by an academic example.

Multi-objective and reliable output feedback control for spacecraft hovering

A multi-objective and reliable dynamic output feedback controller design method is proposed in this paper for spacecraft hovering around targets in circular orbits. The hovering process contains two steps namely, orbital transfer and hovering maintenance. Firstly, the dynamical model of spacecraft hovering is built and multi-objective output feedback control problems for the both steps are formulated. For orbital transfer control, we focus on fuel optimization and pole placement. And H2 performance, H∞ performance and pole placement are considered in hovering maintenance control. Then, sufficient conditions for guaranteed cost and pole placement are provided in the forms of nonlinear matrix inequalities. Using some changes of variables and Schur complement, the obtained sufficient conditions can be rewritten as linear matrix inequality constraints. Likewise, sufficient conditions for H2 control, H∞ control and pole placement are presented and transformed into linear matrix inequalities. Thus, the multi-objective controller design problems for both orbital transfer control and hovering maintenance are described as convex optimizations subject to linear matrix inequalities, respectively. Finally, numerical simulations are presented to illustrate the effectiveness and validity of the proposed dynamic output feedback controller design algorithms.

Design of parameter-scheduled state-feedback controllers using shifting specifications

In this paper, the problem of designing a parameter-scheduled state-feedback controller is investigated. The paper presents an extension of the classical regional pole placement, H2 control and H∞ control problems, so as to satisfy new specifications, that will be referred to as shifting pole placement control, shiftingH2control and shiftingH∞control, respectively. By introducing some parameters, or using the existing ones, the controller can be designed in such a way that different values of these parameters imply different regions where the closed-loop poles are situated, or different performances in the H2 or H∞ sense. The proposed approach is derived within the so-called Lyapunov Shaping Paradigm, where a single quadratic Lyapunov function is used for ensuring stability and desired performances in spite of arbitrary parameter time variation. The problem is analyzed in the continuous-time LPV case, even though the developed theory could be applied to LTI systems in cases when it is desired to vary the control system performances online. Results obtained in simulation demonstrate the effectiveness and the relevant features of the proposed approach.

Effects of intravenous infusion of hydrogen-rich fluid combined with intra-cisternal infusion of magnesium sulfate in severe aneurysmal subarachnoid hemorrhage: study protocol for a randomized controlled trial.

BackgroundThe failures of recent studies intended to prevent cerebral vasospasm have moved the focus of research into delayed cerebral ischemia away from cerebral artery constriction towards other mechanisms. Recent accumulating evidence has suggested that early brain injury is also involved in the development of delayed cerebral ischemia, and that hydrogen can prevent early brain injury. Therefore, we have established a combination therapy of intravenous hydrogen infusion and intra-cisternal magnesium sulfate infusion for the treatment of both early brain injury and cerebral vasospasm. The present randomized controlled clinical trial is designed to investigate the effects of this novel therapeutic strategy on the occurrence of cerebral vasospasm, delayed cerebral ischemia, and clinical outcomes after high-grade subarachnoid hemorrhage.MethodsThis study is a randomized, double-blind, placebo-controlled design to be conducted in two hospitals. A total of 450 patients with high-grade subarachnoid hemorrhage will be randomized to one of three arms: (i) Mg + H2 group, (ii) Mg group, and (iii) control group. Patients who are assigned to the Mg + H2 group will receive intra-cisternal magnesium sulfate infusion (2.5 mmol/L) at 20 mL/h for 14 days and intravenous hydrogen-rich fluid infusion (200 mL) twice a day for 14 days. Patients who are assigned to the Mg group will receive intra-cisternal magnesium sulfate infusion (2.5 mmol/L) at 20 mL/h for 14 days and intravenous normal glucose-electrolyte solution (200 mL) without added hydrogen twice a day for 14 days. Patients who are assigned to the control group will receive intra-cisternal Ringer solution without magnesium sulfate at 20 mL/h for 14 days and intravenous normal glucose-electrolyte solution (200 mL) without added hydrogen twice a day for 14 days. Primary outcome measures will be occurrence of delayed cerebral ischemia and cerebral vasospasm. Secondary outcome measures will be modified Rankin scale score at 3, 6, and 12 months and biochemical markers.DiscussionThe present protocol for a randomized, placebo-controlled study of intravenous hydrogen therapy with intra-cisternal magnesium infusion is expected to establish the efficacy and safety of this therapeutic strategy.Trial registrationUMIN-CTR: UMIN000014696

Fixed-structure ℋ2 controller design for polytopic systems via LMIs

In this paper a new approach for fixed-structure H2 controller design in terms of solutions to a set of linear matrix inequalities are given. Both discrete- and continuous-time single-input single-output (SISO) time- invariant systems are considered. Then the results are extended to systems with polytopic uncertainty. The presented methods are based on an inner convex approximation of the non-convex set of fixed-structure H2 controllers. The designed procedures initialized either with a stable polynomial or with a stabilizing controller. An iterative procedure for robust controller design is given that converges to a suboptimal solution. The monotonic decreasing of the upper bound on the H2 norm is established theoretically for both nominal and robust controller design.