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This paper addresses a problem of optimal error quantification in the framework of robust control theory in the 1 setup. The upper bounds of biased external disturbance and the gains of coprime factor perturbations in a discrete-time linear time invariant SISO plant are assumed to be unknown. The computation of optimal data-consistent upper bounds under a known bias of external disturbance has been simplified to linear programming. This allows for the computation of optimal estimates in real-time and their application to achieve optimal robust steady-state tracking even when facing an unknown bias in the external disturbance. The presented results have been illustrated through computer simulations. [ABSTRACT FROM AUTHOR]

We study a single machine scheduling problem (SMSP) with uncertain job release times (JRTs) under the maximum waiting time (MWT) criterion. To deal with the uncertainty, a robust model is established to find an optimal schedule, which minimises the worst-case MWT (W-MWT) when JRTs vary over given time intervals. Although infinite possible scenarios for JRTs exist, we show that only n scenarios are needed for calculating the W-MWT, where n is the number of jobs. Based on this property, the robust (SMSP) with uncertain JRTs to minimise the W-MWT is formulated as a mixed integer linear programming problem. To solve large-size problem instances, an efficient two-stage heuristic (TSH) is proposed. In the first stage, n near-optimal schedules are obtained by solving n deterministic scenario-based SMSPs, and their W-MWTs are evaluated. To speed up the solution and evaluation process, a modified Gusfield’s heuristic is proposed by exploiting the inner connections of these SMSPs. To further improve the schedule obtained in the first stage, the second stage consists of a variable neighbourhood search method by combining both swap neighbourhood search and insert neighbourhood search. We also develop a method to calculate the lower bound of the proposed model so that we can evaluate the performance of the solutions given by the TSH. Experimental results confirm the robustness of schedules produced and advantages of the proposed TSH over other algorithms in terms of solution quality and run time. [ABSTRACT FROM AUTHOR]

We propose a theory for preventing instabilities and inducing controlled, slow‐slip in frictionally unstable systems, such as the Generalized‐Burridge‐Knopoff (GBK) model and seismic fault models. We exploit the dependence of friction on pressure and use it as a backdoor for altering the dynamics of the underlying dynamical system. We use the mathematical Theory of Control and, for the first time, we manage to (a) stabilize and restrict chaos in this kind of systems, (b) guarantee slow frictional dissipation and (c) tune the system toward desirable global asymptotic equilibria of lower energy. Our control approach is robust and does not require exact knowledge of the frictional or elastic behavior of the system. Numerical examples of control are given for a Burridge‐Knopoff system and a strike‐slip fault model obeying rate‐and‐state friction. GBK models are known to present Self‐Organized Critical (SOC) behavior. Therefore, the presented methodology shows an additional example of SOC Control. Even though further developments are necessary before any practical application, we expect our methodology to inspire earthquake mitigation strategies regarding anthropogenic and/or natural seismicity. Plain Language Summary: Frictional instabilities are omnipresent in nature. A characteristic example is that of earthquakes. Earthquakes are dynamic instabilities that occur when the elastic unloading of the rocks surrounding a fault zone cannot be counterbalanced by fault friction. Recent experience shows that friction can be altered by injecting fluids in the earth's crust. However, until now, most attempts of fluid injections result, sooner or later, in provoking earthquakes. In this work, we present a general mathematical theory that shows that it is possible to adjust the fluid pressure to prevent these instabilities. Moreover, we show how we can induce slow‐slip and allow smooth energy relaxation in such systems. We show also how to drive these systems to desirable stable equilibria of lower energy in a controlled manner. This is achieved even in the absence of complete information about the frictional properties and other uncertainties and unmodeled dynamics. In order to illustrate the theory, we provide numerical examples for spring‐dashpot‐slider (Burridge‐Knopoff) systems, which are characterized by rich dynamics, chaos and self‐organized criticality, and for a seismic fault model. The current limitations of the proposed approach are also extensively discussed. The proposed theoretical framework could inspire strategies for controlling anthropogenic and natural seismicity. Key Points: We present a theory for preventing dynamic events, inducing slow‐slip and allowing smooth energy release in frictionally unstable systemsWe use the mathematical theory of control and we derive robust controllers covering a wide range of uncertainties and unmodeled dynamicsWe provide numerical examples of robust control for Generalized Burridge‐Knopoff systems and seismic fault models [ABSTRACT FROM AUTHOR]

The paper develops a methodology for the design of coherent equalizing filters for quantum communication channels. Given a linear quantum system model of a quantum communication channel, the aim is to obtain another quantum system which, when coupled with the original system, mitigates degrading effects of the environment. The main result of the paper is a systematic equalizer synthesis algorithm which relies on methods of state–space robust control design via semidefinite programming. [ABSTRACT FROM AUTHOR]

For example, sparsity-inducing optimization has proven to be a powerful principle for developing resilient estimation and control algorithms that can withstand random system failures and malicious attacks. From a methodological viewpoint, sparsity-inducing optimization is a powerful paradigm for developing control and estimation schemes that are robust to the aforementioned sparse uncertainties. Modern control theory is challenged by an increasing complexity of the systems to be controlled and meanwhile by the increasing level of demanded performance. [Extracted from the article]

In this survey, we discuss various approaches to control theory that have arisen in the recent decades and reflect the desire to reach a trade-off between the -control theory and the -control theory. The theories of the kind include the theory of risk-sensitive controllers, the theory of suboptimal control with a constraint on the -entropy functional, the mixed -control theory, the minimax -control theory, the anisotropy-based theory, and some others. The survey discusses in more detail the anisotropy-based control theory, which includes both the - and the -theory within a single statement of the problem. [ABSTRACT FROM AUTHOR]

The article reports a sprout of 3‐degree‐of‐freedom (DOF) control. The limitation of feedback control, including 2‐DOF control, has been raised for a long time; however, a suitable control theory for overcoming those limitations has still not been formulated. An underlying reason is that the disturbance‐suppression performance and noise sensitivity cannot be decoupled. Several researches have tried to tackle this problem using a hardware approach, as a noise level depends on a hardware configuration. It should be noted that the hardware design expands spatiotemporal resolution of a system. This approach helps in reducing noise, namely, it works as the 3rd‐DOF for a control system. Therefore, an improvement in the hardware design could be a new angle for solving a mixed‐sensitivity problem. This article quantitatively presents the relation between noise‐reduction performance and the spatiotemporal resolution, and provides a foothold for the 3‐DOF control. [ABSTRACT FROM AUTHOR]

This article presents lifetime estimation using robust control based on thermal path degradation condition of insulated-gate bipolar transistor wind power modules. Online measurements of the on-state voltage V C E ON are considered to be a promising method for obtaining a thermal-sensitive electrical parameter for wire-bond lift-off. This parameter demonstrates a good correlation with junction temperature. Due to the harsh environment, disturbances and uncertain parameters are founded within the compact set of wind energy generation systems. The uncertainty sacrifices some degree of accuracy of junction temperature measurements. Hence, robust control theory has been utilized to synthesize ℋ ∞ controller for the thermal impedance of high-power insulated-gate bipolar transistors. To study this reliability problem, an integrated model of wind energy generation system is built in MATLAB/Simulink for the closed-loop system. Simulation results show the benefit of the designed controller compared to the open-loop system in terms of thermal cycles of junction temperature and lifetime estimation. [ABSTRACT FROM AUTHOR]

In order to make active air suspension have a better vibration control effect while driving, dynamic equation of parameter uncertainty two-degree-of-freedom quarter-vehicle suspension model and non-stationary pavement excitation model are established, analyzing and optimizing active suspension control under linear matrix inequalities with robust H∞ control theory. Under the time domain hard constraints, H∞ state feedback control strategy is proposed and used in the design of the active suspension control system of the quarter vehicle model. The stability of the controller is obtained through time domain analysis and robust parameter stability analysis. For non-steady running roads, the use of a robust H∞ control strategy can effectively improve the riding comfort under the given constraint control force, reduce the body acceleration by about 40% and meet the requirements of limit suspension dynamic deflection of 0.08 m and tire dynamics load of 1 500 N, which improves the vehicle’s handling stability and ride comfort. [ABSTRACT FROM AUTHOR]

This paper presents a novel robust control design for a class of home pension service mobile robots (HPSMRs) with non-holonomic passive constraints, based on the Udwadia-Kalaba theory and Udwadia control. The approach has two portions: dynamics modeling and robust control design. The Udwadia-Kalaba theory is employed to deal with the non-holonomic passive constraints. The frame of the Udwadia control is employed to design the robust control to tracking the servo constraints. The designed approach is easy to implement because the analytical solution of the control force can explicitly be obtained even if the non-holonomic passive constraints exists. The uniform boundedness and uniform ultimate boundedness are demonstrated by the theoretical analysis. The effectiveness of the proposed approach is verified through the numerical simulation by a HPSMR. [ABSTRACT FROM AUTHOR]

In this paper, we research the resilient control problem for cyber-physical system (CPS) under denial-of-service (DoS) attacks. These malicious DoS attacks aim to impede the communication of measurement data or control data in order to endanger the functionality of the closed-loop system. Meanwhile, in order to save network resources, event-triggered mechanism has been introduced into this CPS. By exploiting the relationship between cyber system and physical system, we aim to design the resilient controller and resilient control strategy to tolerate a class of DoS signals characterised by probability without serious hazard to the stability and performance of CPS. Furthermore, considering that the transition probability of cyber state is unknown, the on-policy reinforcement learning method – SARSA (State-Action-Reward-State-Action) – is used to solve this problem. Thus a resilient control algorithm that integrates game theory, robust control theory, event-triggered control method and SARSA learning method is presented to enhance the security and robustness of the CPS. At last, the numerical simulation and experimental results are given to demonstrate the validity and applicability of the proposed algorithm. [ABSTRACT FROM AUTHOR]

The design problem of the adaptive robust prescribed performance controller with external disturbance is studied for the excitation system of single-machine infinite power system in here. By combining the H ∞ theory and adaptive control method, the designed controller not only ensures that the external interference influence on the system is attenuated to a degree of giving, but also the unknown parameter existed in the system can also be estimated. The transient performance of the generator rotor angle can be set in advance with the help of the prescribed performance control (PPC) strategy. Finally, the simulation experiment considers two kinds of faults, namely mechanical fault and short circuit fault, and proves the feasibility and effectiveness via simulation results. • The PPC method is first extended to the power systems. For this case, the transient performances of the generator rotor angle can be pre-assigned. • The adaptive control is utilized to estimate the damping coefficient with the aim of improving the stability and transient performance. • With the help of H ∞ control, the influence of the disturbances can be reduced to a given degree. [ABSTRACT FROM AUTHOR]

In this paper, an experimental procedure used efficiently and successfully for teaching in practical classes of digital control course for undergraduate students who are attending the fifth year in Industrial Electrical Engineering at Federal Institute of Education, Sciences and Technology, in Brazil, is presented. The adopted methodology is characterized by the following steps: modeling of the dynamic system to be controlled from experimental data, model-based digital controller design according to pre-established performance specifications and implementation of the designed digital controller. The experiments are performed on a data acquisition platform, in real time, based on high performance virtual/electronics instrumentation, at Laboratory of Computational Intelligence Applied to Technology. Results from an experimental activity, developed by students in the digital control course, illustrate the main practical aspects that must be taken into account in design and implementation of real time digital PI/PID control. [ABSTRACT FROM AUTHOR]

Summary: The ability of helicopters to hover and land vertically has spurred an interesting field of research on the development of autonomous flight for these rotatory wing aircrafts. Linear control theory with gain scheduling, which is based on linearizing the system at the equilibrium points, dominated the helicopter autopilot design. Unlike the linear cascaded autopilot structure used in the existing literature, this paper uses state‐dependent linear like structure, including rate‐limited actuator dynamics, with cascaded autopilot topology. This approach allows nonlinear control laws to be implemented throughout the entire flight envelope, providing satisfactory robustness and stability over the various parameter uncertainties and time delays. The cascaded autopilot topology with nonlinear dynamical equations contains a new sliding sector control (SSC) mechanism which is derived for multi‐input nonlinear dynamical systems. The proposed SSC structure for multi‐input nonlinear systems is used in the inner loop of the cascaded autopilot system where the fastest dynamics are required to be controlled for rapid changes in the helicopter dynamical characteristics which enables one to stabilize the helicopter over a wide range of flight conditions. The proposed cascaded autopilot topology with the new SSC mechanism is tested in simulations to assess its robustness and stability properties. To establish its feasibility, the proposed control method is replaced with a suboptimal control method, namely state‐dependent differential Riccati equation (SDDRE) method, for the inner loop and the results of the proposed control architecture are compared with those of SDDRE method. [ABSTRACT FROM AUTHOR]

Copyright of Control Theory & Applications / Kongzhi Lilun Yu Yinyong is the property of Editorial Department of Control Theory & Applications and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Aiming at solving the attitude control problem of a hypersonic glide vehicle, this paper proposes a decoupling control method based on a nonlinear extended state observer (NESO). According to the decentralized robust control theory of Tornambè, the coupling terms and the uncertainties are regarded as generalized uncertainties, and the NESO-based estimation and compensation signals are added to the closed-loop control law. The theoretical deduction proves that the proposed method can ensure that the tracking error of the closed-loop system is uniformly bounded. The simulation is carried out on the hypersonic glide vehicle model and compared with the traditional subchannel feedback control method. The simulation results show that the designed decoupling control method has superior control performances, and the influence of channel-coupling and uncertainty is compensated to a great extent. [ABSTRACT FROM AUTHOR]

This paper presents a new disturbance decoupling and rejection method for a multi-connected system, and introduces the composite controller based on disturbance compensator and the state feedback control. While in action, a developed dynamic model of a 2DOF robot system was studied and analyzed. The movement of one joint affects the motion of the other, which brings the control performance down. In order to compensate and keep the desired control performances, we designed a double active control system which can effectively reject the direct mutual disturbances. These disturbances are considered the known uncertainties and can be experimentally determined. The designed control system consists of two controllers, the first one is an inner loop controller and works as a disturbance compensator that attenuates the known disturbances. And the second one, on the other hand, is an outer loop controller, which was designed based on H∞ control theory to maintain the system stability and a robust control performance under the unpredictable uncertainties. In this paper, simulation and experiments were conducted using a PID controller, and the designed control system, as well as changing the payload attached to the end-effector in order to test the control performance. Finally, the results show that the proposed system suppresses and rejects the mutual disturbances effectively with enhanced tracking performances. [ABSTRACT FROM AUTHOR]

Youla-Kucera (YK) parametrization was formulated decades ago for obtaining the set of controllers stabilizing a linear plant. This fundamental result of control theory has been used to develop theoretical tools solving many control problems ranging from stable controller switching, closed-loop identification, robust control, disturbance rejection, adaptive control to fault tolerant control. This paper collects the recent work and classifies them according to the use of YK parametrization, Dual YK parametrization or both, providing the latest advances with main applications in different control fields. A final discussion gives some insights on the future trends in the field. [ABSTRACT FROM AUTHOR]

The explicit consideration of a communication channel model in a feedback control loop is known to be constrained by a fundamental limitation for stabilizability on the channel signal-to-noise ratio (SNR) when the linear time invariant (LTI) plant model is unstable. The LTI modelling approach for real, usually nonlinear, processes compromises accuracy versus complexity of the resulting model. This in turn introduces a gap between the proposed model and the real process, which is known as the model uncertainty. In this paper we then study SNR limitations by considering the continuous-time scenario and the case of an additive coloured Gaussian noise (ACGN) channel with bandwidth limitation, for which we then quantify the infimal SNR subject to the simultaneous presence of plant, channel and noise model uncertainties. We observe, for the special case of memoryless additive white Gaussian noise (AWGN) channels, that the obtained SNR limitation subject to plant model uncertainty can be redefined as a channel capacity limitation for stabilization. • Signal transmission through communication channels is increasingly relevant in Control Theory. • Many relevant communication features can be considered: power, channel bandwidth, time delay, etc. • Control Theory require analysis tools for studying model uncertainty and communication features simultaneously. • The SNR approach can provide such analysis tool, and in turn better inform the controller design. [ABSTRACT FROM AUTHOR]

Typical for qubit realizations are two performance-limiting shortcomings: the physical system is not a perfect two-level system and it couples to an environment. In this work we investigate the limits of performance of the Josephson charge qubit due to the interplay of leakage into unwanted states and dissipative effects due to environmental noise within optimal control theory. For the example of the Hadamard transformation, we show that external control field-gate bias and magnetic flux, which perform the operation for the ideal qubit perfectly, show different robustness regarding leakage into unwanted states and against dissipation. Proper selection of the temporal evolution of gate bias and magnetic flux leads to performance improvements of typically 20% regarding dissipative effects with a predicted optimal fidelity of typically 98%, presuming perfect initial-state preparation and switching times of the order of 500 ps. [ABSTRACT FROM AUTHOR]

In order to solve the nonlinear uncertain system of ship heading control and deal with the influence of interference factors such as external environment and ship speed on ship heading control, this paper proposes a ship controller design method combining the backstepping technique and the adaptive control theory considering the robustness, at first, it describes the mathematical model for ship motion and proposes a nonlinear ship heading control system mathematical model considering the influence of external interference factors; Then, on this basis, the paper designs a ship heading adaptive nonlinear controller with robustness function and achieves the adaptive tracking of ship heading. Simulation results show that the heading control system with adaptive robustness can eliminate influence of certain interferences. The research results indicate that the study of this paper is of great significance for further promoting the development of ship heading nonlinear control theory. [ABSTRACT FROM AUTHOR]

This paper proposes a new battery management system (BMS) for a series string of battery cells. The proposed control structure is based on the duality of the adaptive droop control theory used in dc micro-grid connected sources. An adaptive virtual admittance is used in this paper similar to the virtual resistance control structure used with dc micro-grid connected sources. The virtual admittance value is adjusted according to the associated state of charge for every connected battery cell. The presented BMS control structure yields higher reliability compared to the conventional ones due to its decentralization features and its communication-less ability. Thus, balanced power-sharing is realized among the connected battery cells during charging/discharging conditions. The stability of the proposed control is analyzed using the small signal model. The proposed BMS control structure is validated using simulation results and an experimental prototype for three connected battery cells. [ABSTRACT FROM AUTHOR]

In this paper, a cooperative control of clutch and hydraulic control unit is proposed for the hill-start assist control (HAC) based on the autohold system in order to improve safety and ride comfort. The autohold system model is established as a linear system with bounded uncertainty and disturbance. Then, a novel disturbance-observer-based control is adopted based on an integrated feedforward-feedback compensation, of which the stability and robustness are guaranteed by the $H_\infty$ control theory. The feedforward compensation is recast to a nonlinear and multiobjective optimization problem with some constraints. Finally, the proposed method is verified by the experiments performed on a standard proving ground, and the main results are also provided. [ABSTRACT FROM AUTHOR]

Robust H∞ performance is studied for a class of second-order linear systems with complex eigenvalues， especially the impact of imaginary part of complex eigenvalues on the H∞ performance is studied. It is found that when the real part of the complex eigenvalues is fixed， the impact of the imaginary part of the complex eigenvalues on the H∞ performance becomes little when the value of the imaginary part exceeds a threshold. Based on this observation， a fixed proportional relation between the imaginary part and the real part of the complex eigenvalues is found for a given system matrix under the framework of H∞ performance. Referring to the classical control theory of second-order systems in frequency domain， the relationship between the selection ranges of damping ratio and the complex eigenvalue is further discussed in the framework of H∞ performance， in which a reasonable explanation on the selection ranges of damping ratio is presented. This analysis procedure forms the time-frequency domain interaction synthesis method， which provides a theoretical guidance for the selection and determination of the desired closed-loop poles in the control theory based on the pole placement method. [ABSTRACT FROM AUTHOR]

Copyright of Systems Engineering & Electronics is the property of Journal of Systems Engineering & Electronics Editorial Department and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Collaborative object transportation using multiple MAV with limited communication is a challenging problem. In this paper, we address the problem of multiple MAV mechanically coupled to a bulky object for transportation purposes without explicit communication between agents. The apparent physical properties of each agent are reshaped to achieve robustly stable transportation. Parametric uncertainties and unmodeled dynamics of each agent are quantified and techniques from robust control theory are employed to choose the physical parameters of each agent to guarantee stability. Extensive simulation analysis and experimental results show that the proposed method guarantees stability in worst-case scenarios. [ABSTRACT FROM AUTHOR]

The problem of poles assignment and robust poles assignment in linear discrete-time periodic (LDP) system via periodic state feedback is discussed in this paper. Based on a numerical solution to the periodic Sylvester matrix equation, an iterative algorithm of computing the periodic feedback gain can be obtained. By optimizing the free parameter matrix in the proposed algorithm, according to robustness principle, an algorithm on the minimum norm and robust poles assignment for the LDP systems is presented. Two numerical examples are worked out to illustrate the effect of the proposed approaches. [ABSTRACT FROM AUTHOR]

This paper proposes observer-based output feedback force reflecting robust coordination control for networked bilateral shared telerobotic system with asymmetrical delay and uncertainty. We design state feedback-based force reflecting control algorithm provided that all the states are available for feedback. We then replace the unknown velocity states by model-free observer to develop output feedback-based force reflecting robust coordination control algorithm for bilateral shared autonomous system. The coordination control algorithm is designed by combining delayed position and velocity states with the reflected interaction forces from human and environment. Robust adaptive control theory is employed to deal with uncertainty. The stability analysis is shown by using Lyapunov method. The method does not require linear matrix inequality and uncertainty. Compared with other force reflection methods, the design uses reflected forces from both interaction between master and human and between slave and environment. Experimental results are presented to demonstrate the validity of the proposed design for real-time applications. [ABSTRACT FROM AUTHOR]

In this paper, a novel control scheme of the bidirectional isolated dual-active-bridge (DAB) dc–dc converters is proposed to regulate the output voltage and current, based on a sliding mode (SM) control. At first, a mathematical model of the DAB converter is expressed in a state-space form. Then, the output voltage and current controllers of the DAB converter are designed with the double-integral SM control theory, which is robust to the model uncertainty and disturbance. The proposed control method provides not only the zero steady-state error without any chattering but also the fast transient response for load variations and reference changes. The validity of the proposed control algorithm has been verified by simulation and experimental results for a 1.5-kW DAB converter. [ABSTRACT FROM AUTHOR]

This paper deals with the robust control system design and implementation of a brake actuator for a smart car. To deliver robust performance, an H8 controller had been chosen for the task. This allows excellent disturbance rejection while requiring low computational needs. In order to realize the controller a nominal model of the system has been identified, then, the parameter uncertainties were taken into account to find the stabilizing controller. The brake system consists of a low level H8 controller sustaining robustness, a mid-level serial compensator for effective setpoint tracking and a high level supervisory control logic to deliver a reliable system. The implementation was tested and verified on a test bench using rapid prototyping tools and HIL methods. [ABSTRACT FROM AUTHOR]

A defender–attacker–target problem with non-moving target is considered. This problem is modelled by a pursuit-evasion zero-sum differential game with linear dynamics and quadratic cost functional. In this game, the pursuer is the defender, while the evader is the attacker. The objective of the pursuer is to minimise the cost functional, while the evader has two objectives: to maximise the cost functional and to keep a given terminal state inequality constraint. The open-loop saddle point solution of this game is obtained in the case where the transfer functions of the controllers for the defender and the attacker are of arbitrary orders. [ABSTRACT FROM AUTHOR]

By means of the differential geometry method and the robust H○∞ control theory， a robust H○∞ control strategy for active seat suspension and vehicle active suspension based on differential geometry method is proposed. On the basis of establishing the three-degree-of-freedom model of the "car-chair" vehicle， considering the nonlinear characteristics of the elastic force and damping force of seat suspension and vehicle suspension， the differential geometry method and the nonlinear state feedback transformation method are applied to precisely linearize the active suspension nonlinear system. Then， the vertical accelerations of the chassis and the seat are taken as the control targets， and the robust suspension H○∞ controller of seat suspension and vehicle suspension is designed with the wheel dynamic displacement and the vehicle suspension deflection range less than the specified value as the constraint conditions. The simulation experiment with Matlab/Simulink is carried out to verify the effectiveness and feasibility of the integrated variable gain LQR control method. [ABSTRACT FROM AUTHOR]

Copyright of Systems Engineering & Electronics is the property of Journal of Systems Engineering & Electronics Editorial Department and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Motivation Flow cytometry and mass cytometry are widely used to diagnose diseases and to predict clinical outcomes. When associating clinical features with cytometry data, traditional analysis methods require cell gating as an intermediate step, leading to information loss and susceptibility to batch effects. Here, we wish to explore an alternative approach that predicts clinical features from cytometry data without the cell-gating step. We also wish to test if such a gating-free approach increases the accuracy and robustness of the prediction. Results We propose a novel strategy (CytoDx) to predict clinical outcomes using cytometry data without cell gating. Applying CytoDx on real-world datasets allow us to predict multiple types of clinical features. In particular, CytoDx is able to predict the response to influenza vaccine using highly heterogeneous datasets, demonstrating that it is not only accurate but also robust to batch effects and cytometry platforms. Availability and implementation CytoDx is available as an R package on Bioconductor (bioconductor.org/packages/CytoDx). Data and scripts for reproducing the results are available on bitbucket.org/zichenghu_ucsf/cytodx_study_code/downloads. Supplementary information Supplementary data are available at Bioinformatics online. [ABSTRACT FROM AUTHOR]

In this paper we present an approach to reconstruct the 3D shape of multiple deforming objects from a collection of sparse, noisy and possibly incomplete 2D point tracks acquired by a single monocular camera. Additionally, the proposed solution estimates the camera motion and reasons about the spatial segmentation (i.e., identifies each of the deforming objects in every frame) and temporal clustering (i.e., splits the sequence into motion primitive actions). This advances competing work, which mainly tackled the problem for one single object and non-occluded tracks. In order to handle several objects at a time from partial observations, we model point trajectories as a union of spatial and temporal subspaces, and optimize the parameters of both modalities, the non-observed point tracks, the camera motion, and the time-varying 3D shape via augmented Lagrange multipliers. The algorithm is fully unsupervised and does not require any training data at all. We thoroughly validate the method on challenging scenarios with several human subjects performing different activities which involve complex motions and close interaction. We show our approach achieves state-of-the-art 3D reconstruction results, while it also provides spatial and temporal segmentation. [ABSTRACT FROM AUTHOR]

Summary: This work deals with the optimal controller synthesis against high‐level multiple requirements using evolutionary computation. Indeed, such stochastic algorithms are interesting to solve problems based on complex industrial specifications and so seem to be particularly well suited to optimal robust controller synthesis. Using the H∞ loop‐shaping framework, the optimal weights/controller tuning without any structural assumption (in terms of poles/zeros/damping) on the searched filters (except of course their order) is investigated. The absence of such any structural assumption is important to avoid affecting the quality of the solution toward a complex specification and allows reducing the synthesis problem to a simple one with static scalings in place of frequency weights. Using a version of differential evolution algorithm well adapted for high dimensional control problems, computing directly a fixed‐structure controller for complex industrial specifications toward a generic nonconstraint fitness with quite reasonable computing time is achieved. The illustrating example deals with the line‐of‐sight stabilization problem. [ABSTRACT FROM AUTHOR]

Summary: In this paper, we provide a robust observer‐based output feedback control scheme for a class of nonlinear systems where there are uncertain triangular and nontriangular nonlinearities, nontrivial diagonal terms, and external disturbance. The presence of diagonal terms is the main generalized feature over the existing results. In order to handle the diagonal terms, there is a gain‐scaling factor in the proposed controller. Through the analysis, we show that all states and observer errors of the controlled system remain bounded. Moreover, the ultimate bounds of some states and observer errors can be made (arbitrarily) small by adjusting the gain‐scaling factor reflecting on the structure of nonlinearities and external disturbance. The validity of our control scheme is experimentally verified via the ball position control of an electromagnetic levitation system. [ABSTRACT FROM AUTHOR]

Abstract In this paper, the finite-frequency H ∞ control problem of active suspensions is investigated. In view of the human body is much sensitive to the vertical vibrations between 4 and 8 Hz, a robust finite-frequency state-feedback H ∞ controller is introduced to suppress the sprung vibration in the concerned frequency range. In order to simultaneously control the vehicle heave, roll, and pitch motions, a full-car suspension model is adopted. Suspension parameter uncertainties, actuator saturation, and suspension deflection constraints are all considered in the model, and a robust controller is designed to handle the parameter uncertainties and achieve the prescribed H ∞ performance. Simulation with different road conditions and parameter uncertainties are performed and the results illustrate the effectiveness of the proposed controller. Highlights • A full-car model is adopted to control the heave, pitch and roll motions. • The 4–8 Hz range disturbance is attenuated by a finite-frequency controller. • The parameter variations are considered to guarantee the system robustness. [ABSTRACT FROM AUTHOR]

The design of robust tracking control for quadrotors is an important and challenging problem nowadays. In this paper, a robust tracking output-control strategy is proposed for a quadrotor under the influence of external disturbances and uncertainties. Such a strategy is composed of a finite-time sliding-mode observer, which estimates the full state from the measurable output and identifies some types of disturbances. It is also composed of a combination of PID controllers and continuous sliding-modes controllers that robustly track a desired time-varying trajectory with exponential convergence despite the influence of external disturbances and uncertainties. The closed-loop stability is provided based on the input-to-state stability (ISS) and finite-time ISS properties. Finally, experimental results in real time show the performance of the proposed control strategy. [ABSTRACT FROM AUTHOR]

Abstract Renovation and retrofit of gas turbine control systems yield significant economic savings, enhanced reliability, and improved performance. In recent years, the gas turbine industry is increasingly facing the need to well-established procedures for the acceptance tests of renovated control systems. This paper proposes a unified framework to evaluate the performance of renovated gas turbine control systems. Under a set of assumptions on the ambient and fuel conditions, a low-complexity modular model is presented and identified using optimization-oriented identification techniques. The accuracy of the proposed model is validated through experimental studies in full-load, min-load, and no-load operating conditions. Subsequently, a model-based analysis framework is proposed to determine realistic levels of tracking performance, robustness margin and disturbance attenuation by utilizing the supporting tools in robust control theory. Quantitative and qualitative performance indices are introduced to provide acceptance criteria for the existing control loops as compared to the optimal ones. The proposed procedure is applied to a W251-B2 gas turbine manufactured by Westinghouse company, and the results show that the optimal control system outperforms the existing controllers based on quantitative and qualitative indices. The proposed procedure determines whether the overall performance of the renovated control system sufficiently meets the requirements. Highlights • A unified framework to evaluate performance of renovated gas turbine control systems. • A low-complexity modular model. • Model-based analysis and design framework. • Quantitative and qualitative performance indices to provide acceptance criteria. • Application to a W251-B2 gas turbine. [ABSTRACT FROM AUTHOR]

Abstract A bipartite network is a graph that contains two disjoint sets of nodes, such that every edge connects the two node sets. The significance of identifying influential nodes in bipartite networks is highlighted from both theoretical and practical perspectives. By considering the unique feature of bipartite networks, namely, links between the same node set are forbidden, we propose two new algorithms, called SVD-rank and SVDA-rank respectively. In the two algorithms, singular value decomposition (SVD) is performed on the original bipartite network and augmented network (two ground nodes are added). Susceptible–Infected–Recovered (SIR) model is employed to evaluate the performance of the two algorithms. Simulations on seven real-world networks show that the proposed algorithms can well identify influential spreaders in bipartite networks, and the two algorithms are robust to network perturbations. The proposed algorithms may have potential applications in the control of bipartite networks. Highlights • We proposed SVD-rank to identify influential spreaders in bipartite networks. • Inspired by the LeaderRank, we also proposed SVDA-rank. • Simulations on seven bipartite networks show effectiveness of the algorithms. • The proposed algorithms are robust to network perturbations. [ABSTRACT FROM AUTHOR]

Abstract Soft sensor plays a decisive role in making control strategies and production plans. However, the difficulty in establishing accurate and robust soft sensors using an individual model is continuously increasing due to the increasing scale and complexity in modeling data. To handle this problem, an effective ensemble model using partial least squares regression (PLSR) integrated with extreme learning machine (ELM) with multiple activation functions (PLSR-MAFELM) is proposed in this paper. The proposed PLSR-MAFELM is simple in construction: firstly, train several ELM models assigned with different activation functions using the least squares solution; secondly, combine ELM models for enhancing accuracy and stability performance; finally, obtain the optimal ensemble outputs by aggregating the outputs of individual ELM models using PLSR. To test the performance of the proposed PLSR-MAFELM model, a UCI benchmark dataset and two real-world applications are selected to carry out simulation case studies. Simulation results show that PLSR-MAFELM can achieve good stability and accuracy performance, which indicates that the generalization capability of soft sensors can be improved through combining some single models. Highlights • A multi-activation functions based extreme learning machine ensemble is proposed. • The ensemble model utilizes different and effective nonlinear activation functions. • Partial least squares regression is used to aggregate the outputs of single models. • The ensemble model can be accurate, stable and efficient in intelligent measurement. • Simulation results confirm the effectiveness of the proposed ensemble framework. [ABSTRACT FROM AUTHOR]

In this paper, the problem of robust preview control for uncertain discrete singular systems is considered. First of all, by employing the forward difference for uncertain discrete singular systems, the singular augmented error system with the state vector, the input control vector, and the previewable reference signal is derived. Since there is a singular matrix in the system, the existing method cannot be directly applied to this problem. By considering the stability of the transposition system with Linear Matrix Inequality (LMI) method, a new stability criterion for the transposition system is introduced. Then, the robust controller for the augmented error system is obtained, which is regarded as the robust preview controller for the original singular system. At last, the numerical simulation shows the correctness and effectiveness of the results. [ABSTRACT FROM AUTHOR]

This paper considers the problem of recovering a group sparse signal matrix Y = [ y 1 , ⋯ , y L ] from sparsely corrupted measurements M = [ A ( 1 ) y 1 , ⋯ , A ( L ) y L ] + S , where A ( i ) 's are known sensing matrices and S is an unknown sparse error matrix. A robust group lasso (RGL) model is proposed to recover Y and S through simultaneously minimizing the ℓ 2 , 1 -norm of Y and the ℓ 1 -norm of S under the measurement constraints. We prove that Y and S can be exactly recovered from the RGL model with high probability for a very general class of A ( i ) 's. [ABSTRACT FROM AUTHOR]

Summary: This paper examines the problem of codesigning a robust L2‐gain networked control system along with the network's properties such as sampling interval, service rate, and packet dropout. On the basis of the generalized integral inequality of Bessel‐Legendre inequality approach, sufficient conditions for the existence of a robust L2‐gain controller that incorporates the network's properties are derived and expressed in terms of linear matrix inequalities. Finally, two examples are used to illustrate the effectiveness of the proposed methodology. [ABSTRACT FROM AUTHOR]

In this paper, generalized form of transfer function model of a cart inverted pendulum system is presented. Furthermore, robustness analysis of PID-based cart inverted pendulum using LQR approach and SBL approach are carried out using Krishnamurthi's corollary on Routh criterion by considering variations in cart mass, pendulum length, and also applied force to the cart. Here, the mathematical formula is developed which provides limit for the mass of cart before the pendulum becomes unstable. The most important advantage of the proposed approach is that the analysis is carried using classical approach without using advanced robust control techniques. The results have been verified on a hardware set-up of cart inverted pendulum system. Finally, practical issues have been identified by comparing simulation and hardware results. The results can be expected to be useful in other real-time applications. [ABSTRACT FROM AUTHOR]

Abstract An adaptive fault-tolerant nonlinear control scheme is proposed for precise 3-axis attitude tracking of miniature spacecraft in the presence of control input saturation, model uncertainties, external disturbances, and reaction wheel faults. Two configurations of reaction wheel assembly are examined in this paper, (A1) Traditional four wheel setup where three reaction wheels are in orthogonal configuration along with one oblique wheel; and (A2) Four wheels in a pyramid configuration. Multiplicative reaction wheel faults are considered along with complete failure of one wheel (A1) and two wheels (A2). The proposed control algorithm does not require an explicit fault detection and isolation mechanism and therefore failure time instants, patterns, and values of actuator failures remain unknown to the designer. The stability conditions for robustness against model uncertainties and external disturbances are derived using Lyapunov stability theory to establish the regions of asymptotic stabilization. The benefits of the proposed control methodology are analytically authenticated and also validated using hardware-in-the-loop simulations. The experimental results clearly establish the robustness of the proposed autonomous control algorithm for precise attitude tracking in the event of reaction wheel faults and failures. Highlights • Faults tolerant control for spacecraft attitude tracking is examined. • Multiplicative reaction wheel faults are considered. • Control input saturation and model uncertainties are considered. • An adaptive nonlinear control scheme based on sliding mode technique is proposed. • Lyapunov stability proof and hardware-in-the-loop simulations are conducted. [ABSTRACT FROM AUTHOR]

This paper investigates the control issue of uncertain systems in presenting of time-varying delay and stochastic disturbance. The state information is real-timely measured by the sensor and directly sent to an event-trigger, then only necessary data is transmitted by the event-trigger to the controller while the rest redundant information is simply discarded. Since the controller receives a discontinuous-time data sequence, an observer is designed to restructure a substitutional continuous-time state and an observer-state-dependent sliding mode control law is proposed. By the proposed method, not only the mean square exponential stability of closed-loop system can be guaranteed almost surely but also the data transmission amount can be reduced. In addition, the chattering behaviour can be alleviated, meanwhile, the match conditions of uncertainty and disturbance are not required. More significantly, the Zeno phenomena of the event-trigger can be conveniently excluded and the minimal event-triggering interval is also given. A numerical example is provided to demonstrate the effectiveness of the proposed method. [ABSTRACT FROM AUTHOR]

Summary: This paper is concerned with the stabilization of linear systems with both state and distinct input delays. Nested predictor feedback controllers are designed to predict the future states such that the distinct input delays that can be arbitrarily large yet bounded are compensated completely. It is shown that the compensated closed‐loop system possesses the same characteristic equation as the closed‐loop system without distinct input delays. Both continuous‐time and discrete‐time time‐delay systems are studied in this paper. Moreover, the safe implementation problem for the continuous‐time nested predictor feedback controller is solved via adding input filters. Three numerical examples show the effectiveness of the proposed approaches. [ABSTRACT FROM AUTHOR]