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A novel robust Student's t-based Kalman filter is proposed by using the variational Bayesian approach, which provides a Gaussian approximation to the posterior distribution. Simulation results for a manoeuvring target tracking example illustrate that the proposed filter has smaller root mean square error and bias than existing filters. [ABSTRACT FROM PUBLISHER]

In this paper, we analyze all possible situations of rank deficiency that cause breakdown in block conjugate gradient (BCG) solvers. A simple solution, breakdown-free block conjugate gradient (BFBCG), is designed to address the rank deficiency problem. The rationale of the BFBCG algorithm is to derive new forms of parameter matrices based on the potentially reduced search subspace to handle rank deficiency. Orthogonality properties and convergence of BFBCG in case of rank deficiency are justified accordingly with mathematical rigor. BFBCG yields faster convergence than restarting BCG when breakdown occurs. Numerical examples suffering from rank deficiency are provided to demonstrate the robustness of BFBCG. [ABSTRACT FROM AUTHOR]

Most complex engineering structures are three-dimensional in practice. The process of one-dimensional extending to three-dimensional is a challenge that must be conquered by Operational Modal Analysis (OMA) methods when these methods are applied to complex engineering applications supported by scientific researches. This study put forward a new three-dimensional structure OMA method based on Second-Order Blind Identification (SOBI) and general reversion of least square. Firstly, modal coordinates decomposition of one-dimensional structural vibration response signal with SOBI. Secondly, the reasons that modal parameters identified by SOBI including energy uncertainty, order uncertainty and modal missing are explained in theory. Thirdly, the SOBI algorithm is used to decompose the response signals of displacement of a direction whose vibration response is the largest, then the other two directions are calculated by using the least square generalized inverse algorithm, and the modal parameters of three-dimensional structures are identified by the matrix assembly method. Numerical simulation results in a cylindrical shell demonstrated that this novel method is practical and effective by applied to practice in OMA of three-dimensional structures, and robustness to Gauss measurement noise disturbances. [ABSTRACT FROM AUTHOR]

Modelling wave propagation is the most essential part in assessing the risk and hazard of tsunami and storm surge events. For the computational assessment of the variability of such events, many simulations are necessary. Even today, most of these simulations are generally run on supercomputers due to the large amount of computations necessary. In this study, a simulation framework, named TsuPy, is introduced to quickly compute tsunami events on a personal computer. It uses the parallelized power of GPUs to accelerate computation. The system is tailored to the application of robust tsunami hazard and risk modelling. It links up to geophysical models to simulate event sources. The system is tested and validated using various benchmarks and real-world case studies. In addition, the robustness criterion is assessed based on a sensitivity study comparing the error impact of various model elements e.g. of topo-bathymetric resolution, knowledge of Manning friction parameters and the knowledge of the tsunami source itself. This sensitivity study is tested on inundation modelling of the 2011 Tohoku tsunami, showing that the major contributor to model uncertainty is in fact the representation of earthquake slip as part of the tsunami source profile. TsuPy provides a fast and reliable tool to quickly assess ocean hazards from tsunamis and thus builds the foundation for a globally uniform hazard and risk assessment for tsunamis. [ABSTRACT FROM AUTHOR]

This paper investigates the robust dynamic output feedback non-fragile control (RDOFNFC) strategy for spacecraft attitude stabilization problem with nonlinear perturbations. The spacecraft attitude dynamics model takes the actuator saturation limits, external disturbances, controller perturbation and model parameter uncertainty into account. To make spacecraft attitude system satisfy H ∞ performance and quadratic stability, with respect to the additive perturbation in initial state and multiplicative perturbation in decay phase, the corresponding RDOFNFC is designed respectively. Based on Lyapunov theory, the controller design is transformed into a multi-objective convex optimization problem based on linear matrix inequalities (LMIs). Simulation results based on the on-orbit servicing spacecraft show good performance under external disturbances, model parameter uncertainty and controller perturbation, which validates the effectiveness and feasibility of the proposed control method. [ABSTRACT FROM AUTHOR]

For the realistic case where there is no secondary snapshot that does not contain the desired signal and exhibits the statistical characteristics similar to the snapshot under test, direct data domain (D 3 ) beamforming approaches have been proposed to estimate a desired signal in the presence of interference. However, the basic idea of the D 3 methods is realized by making significant sacrifices with respect to the number of degrees of freedom (DoFs). In this paper, we present a multi-snapshot approach for D 3 beamforming. Using the least-squares method with multiple snapshots, we can eliminate the interference without causing a severe reduction in the number of DoFs. In addition, to consider a mismatch between nominal and actual target steering vectors, we propose a D 3 approach combined with a probability constraint to prevent the self-nulling effect, and the relationship between the probability constraint and norm constraint is discovered. The simulations verify that the proposed method provides better performance and robustness than the conventional D 3 approaches. [ABSTRACT FROM AUTHOR]

This paper analyzes the emergent behaviors of pedestrian groups that learn through the multiagent reinforcement learning model developed in our group. Five scenarios studied in the pedestrian model literature, and with different levels of complexity, were simulated in order to analyze the robustness and the scalability of the model. Firstly, a reduced group of agents must learn by interaction with the environment in each scenario. In this phase, each agent learns its own kinematic controller, that will drive it at a simulation time. Secondly, the number of simulated agents is increased, in each scenario where agents have previously learnt, to test the appearance of emergent macroscopic behaviors without additional learning. This strategy allows us to evaluate the robustness and the consistency and quality of the learned behaviors. For this purpose several tools from pedestrian dynamics, such as fundamental diagrams and density maps, are used. The results reveal that the developed model is capable of simulating human-like micro and macro pedestrian behaviors for the simulation scenarios studied, including those where the number of pedestrians has been scaled by one order of magnitude with respect to the situation learned. [ABSTRACT FROM AUTHOR]

The degradation in power quality causes adverse economical impact on the utilities and customers. Harmonics in current and voltage are one of the most commonly known power quality issues and are solved by the use of a hybrid series active power filter (HSAPF). In this paper, a new controller design using sliding-mode controller-2 is proposed to make the HSAPF more robust and stable. An accurate averaged model of a three-phase HSAPF is also derived in this paper. The design concept of the robust HSAPF has been verified through simulation and experimental studies, and the results obtained are discussed. [ABSTRACT FROM AUTHOR]

In this paper an issue related to electric energy management on board an aircraft is considered. A battery pack is connected to a high-voltage bus through a controlled Battery Charge/Discharge Unit (BCDU) that makes the overall behaviour of the battery “intelligent.” Specifically, when the aeronautic generator feeding the high-voltage bus has enough energy the battery is kept under charge, while if more loads are connected to the bus, so that the overload capacity of the generator is exceeded, the battery “helps” the generator by releasing its stored energy. The core of the application is a robust, supervised control strategy for the BCDU that automatically reverts the flow of power in the battery, when needed. Robustness is guaranteed by a low-level high gain control strategy. Switching from full-charge mode (i.e., when the battery absorbs power from the generator) to generator mode (i.e., when the battery pumps energy on the high-voltage bus) is imposed by a high-level supervisor. Different from previous approaches, mathematical proofs of stability are given for the controlled system. A switching implementation using a finite-time convergent controller is also proposed. The effectiveness of the proposed strategy is shown by detailed simulations in Matlab/Stateflow/SimPowerSystem. [ABSTRACT FROM AUTHOR]

This article deals with the design and real-time implementation of three second order sliding mode controllers for the altitude tracking of a quadrotor aircraft. A comparative study based on the analysis of the tracking error was performed in order to determine the controller presenting the best performance in a real-time application at outdoors environments. The compared strategies were the Classical First Order Sliding Mode Controller, the Super Twisting Sliding Mode Controller, the Modified Super Twisting Sliding Mode Controller and the Nonsingular Terminal Super Twisting Sliding Mode Controller. The last three controllers are based on the second order sliding mode technique, and they ensure robustness with respect to modeling errors even under external disturbances while reducing the chattering phenomenon in comparison with first order sliding mode controllers. Lyapunov stability theory is used to prove convergence in finite time of the altitude tracking error in the different proposed control laws. In order to demonstrate the effectiveness of the proposed solutions, an extensive set of simulation and real-time experimental results are presented. [ABSTRACT FROM AUTHOR]

A quantitative evaluation of delaminations in composite laminates encounters multiple difficulties due to the anisotropic behaviour of the laminate. Extensive calibrations for each structure are required and each depth needs certain manual modifications for optimal performance of the estimation routines. In this manuscript, a robust technique is developed using a numerical model to estimate the thermal diffusivity through the anisotropic material which improves defect depth estimation between each layer. Three different calibration depths are necessary to compute the diffusivity through a certain stacking sequence of a multi-layered composite laminate. The results are compared with the state-of-the-arts experimental evaluation techniques and with a regular numerical model. It is seen that especially for deeper defects, the optimised numerical model delivers more accurate results due to the considered anisotropic diffusivity. [ABSTRACT FROM AUTHOR]

This paper deals with the trajectory tracking problem of autonomous underwater vehicles (AUVs) in the presence of dynamic uncertainties and time-varying external disturbances. Three exponentially convergent robust controllers, namely, the min-max type controller, the saturation type controller and the smooth transition type controller are proposed to drive an AUV to track a predefined trajectory. It is shown that the filtered tracking errors, position tracking errors and velocity tracking errors for the three proposed controllers are exponentially convergent. Moreover, all the above tracking errors for the three proposed controllers can be shaped by specific analytic expressions and such expressions illustrate how the transient responses of the above tracking errors can be modified by adjusting the control parameters. The characteristics of the three proposed controllers are summarized and demonstrated with numerical simulations. Theoretical comparison analysis and comparative simulations with the existing RISE-based controller of AUV are presented to show the effectiveness of the three proposed exponentially convergent robust controllers. [ABSTRACT FROM AUTHOR]

This paper deals with a comparative analysis of the performances of sliding mode controller (SMC) and fractional-order sliding mode controller (FOSMC) when applied to the problem of trajectory control of ball in a ball and plate (BP) system. Owing to the open-loop instability, inherent nonlinearity, and under actuation, the BP system is considered a benchmark platform for testing the efficacies of different control algorithms. In this work, a robust cascaded SMC is initially designed to track the desired trajectory and tackle the uncertainties present in the system. In order to improve the speed of response, an FOSMC is designed thereafter. The two-control algorithms are simulated on MATLAB-Simulink environment and the experimental validation is later carried out on a BP laboratory set-up (Feedback Instruments Model No. 033-240). The simulation results and experimental validation convey that FOSMC performs better than SMC in regard to speed of response and tracking accuracy without increasing the level of chattering and control effort. [ABSTRACT FROM AUTHOR]

A robust entry guidance law based on terminal sliding mode and second-order differentiator is designed for trajectory tracking in this paper. The bank angle is regarded as the control variable. A novel nonlinear compound controller is designed to make the system with the trajectory-tracking error and its rate as states be input-to-state stable (ISS) with respect to uncertainties. The terminal sliding mode controller is designed to the problem of entry guidance by using the second-order differentiator to estimate the total disturbances. The proposed nonlinear compound control law by employing the second-order differentiator and the terminal sliding mode controller, provide robustness, higher control precision. Also, simulation results are presented to illustrate the effectiveness of the control strategy. [ABSTRACT FROM AUTHOR]

A Fault Tolerant Attitude Control algorithm for the spacecraft using Single Gimbal Control Moment Gyros (SGCMGs) as actuator is proposed. The controller is designed using the sliding mode control theory to control the gimbal rate directly and there is no singular point in the control algorithm, which means that we don't need to design the steering laws again and the singularity problems can be avoided. Also the gimbal rate saturation is considered when designing the control method. The adaptive control algorithm is used to estimate the disturbance and the boundary of the fault and saturation, which means that no prior information of the fault is needed. Although the controller is designed based on the SGCMGs, it can also be employed when reaction wheels work as the actuator of the spacecraft. Also the complete failure of several SGCMGs is allowed. It is proved based on the Lyapunov stability theorem that the designed control algorithm can achieve the attitude asymptotic stability both on the fault or fault-free condition. The simulation results show that the proposed method has a strong robustness. [ABSTRACT FROM AUTHOR]

This paper studies the problem of designing a robust controller for the nonlinear multi-input multi-output continuous stirred tank reactor (CSTR) in the presence of uncertainties in parameters of the process model. For this purpose, by first using the feedback linearization method, the equivalent linearized model of the CSTR is obtained. In the second step, to cope with uncertainties, two robust controllers are designed; one using H∞ mixed-sensitivity and the other using DK-iteration method. In this step, the required performance and uncertainties are expressed in terms of the suitable weight functions. Finally, the performance of the resulting feedback system is verified through numerical simulations. [ABSTRACT FROM AUTHOR]

Dual-winding bearingless switched reluctance motor (BSRM) is a multivariable high-nonlinear system characterized by strong coupling, and it is not completely reversible. In this paper, a new decoupling control strategy based on improved inverse system method is proposed. Robust servo regulator is adopted for the decoupled plants to guarantee control performances and robustness. A phase dynamic compensation filter is also designed to improve system stability at high-speed. In order to explain the advantages of the proposed method, traditional methods are compared. The tracking and decoupling characteristics as well as disturbance rejection and robustness are deeply analyzed. Simulation and experiments results show that the decoupling control of dual-winding BSRM in both reversible and irreversible domains can be successfully resolved with the improved inverse system method. The stability and robustness problems induced by inverse controller can be effectively solved by introducing robust servo regulator and dynamic compensation filter. [ABSTRACT FROM AUTHOR]

This paper proposes multicriteria adaptive observers for a class of singular systems with unknown time-varying parameters. Two criteria for the H∞ disturbance attenuation level and the upper bound of an ultimate invariant set are scalarized into a single cost function and then it is minimized by varying the weight parameter, which creates the optimal trade-off curve or Pareto optimal points. The proposed multicriteria adaptive observers are shown to be able to easily include integral action for better robust performance. It is demonstrated with numerical simulations that the proposed multicriteria adaptive observers provide the good estimation accuracy and allow effective and compromising design by considering two different cost functions simultaneously. [ABSTRACT FROM AUTHOR]

This paper introduces a novel metaheuristic methodology to address the Multiple Measurement Vectors problem using a well-known greedy search strategy. A modified version of Tabu Search algorithm is utilized to determine a precise estimation of row support and then joint sparse samples are reconstructed using MMSE criterion. The proposed approach is more robust to the sparsity order variations and noise uncertainty, in comparison with the conventional MMV problem solvers. Furthermore, to avoid wastage of the sampling resources and reduce the implementation costs, a two-step joint sparse recovery framework is developed which the first step predicts and adjusts the optimum sampling rate and the second one reconstructs signal vectors applying obtained sampling rate. Numerical simulations demonstrate the superiority of proposed technique for both improving the performance and reducing the computational complexity and sampling costs. [ABSTRACT FROM AUTHOR]

An integrated vehicle dynamics control (IVDC) algorithm, developed for improving vehicle handling and stability under critical lateral motions, is discussed in this paper. The IVDC system utilises integral and nonsingular fast terminal sliding mode (NFTSM) control strategies and coordinates active front steering (AFS) and direct yaw moment control (DYC) systems. When the vehicle is in the normal driving situation, the AFS system provides handling enhancement. If the vehicle reaches its handling limit, both AFS and DYC are then integrated to ensure the vehicle stability. The major contribution of this paper is in improving the transient response of the vehicle yaw rate and sideslip angle tracking controllers by implementing advanced types of sliding mode strategies, namely integral terminal sliding mode and NFTSM, in the IVDC system. Simulation results demonstrate that the developed control algorithm for the IVDC system not only has strong robustness against uncertainties but also improves the transient response of the control system. [ABSTRACT FROM AUTHOR]

This paper presents the design of a single supply CMOS level up shifter for low voltage and low energy consumption. The proposed voltage level converter is implemented using low threshold voltage transistors in 65 nm CMOS technology. The shifter circuit designed for an output of 1.1 V was verified, through the post–layout simulation, to be functional for an input voltage range of 0.45–1 V. We compare our work with several other level shifters. With a 50 fF of capacitive load, the shifter's energy–delay product is a 40% lower than a similar single supply level up shifter. Moreover, the measurements on the fabricated dies show that the proposed structure is able to drive a double capacitive load of up to 105 fF, without any impact on the static power consumption. Monte–Carlo analysis demonstrates the robustness of the proposed shifter within a 3 σ device mismatch. [ABSTRACT FROM AUTHOR]

This paper proposes a fractional order sliding mode control for the deployment of tethered space systems with the consideration of uncertainty of external disturbances and unmodeled system dynamics. The proposed fractional order sliding mode control consists of two sub-sliding manifolds that are defined separately for the actuated and unactuated states. This, in turn, generates a control scheme to make all states move toward to the desired states. The stability analysis of the proposed control law indicates not only all states converge to the desired states at equilibrium but also disturbances caused by the uncertainty can be suppressed satisfactorily. Parametric studies are conducted to investigate the influences of fractional order and sub-sliding manifold of unactuated states on the performance of the proposed control law. The performance is compared with the sliding mode, PD and fractional order PD control laws for a baseline scenario of tether deployment. The proposed control law performs better than others in the settling time and the maximum pitch angle control in the presence of unwanted disturbances. Effectiveness and robustness of the proposed control law are demonstrated by computer simulations. [ABSTRACT FROM AUTHOR]

This paper introduces an adaptive fractional-order sliding-mode controller for stabilization of a two-axis gimbal platform in the presence of the torque disturbance effects. To tend the angular velocities of the inner gimbal in the elevation and azimuth axes to zero, an adaptive fractional-order sliding-mode approach is utilized. To achieve this goal, fractional-order sliding surfaces in both azimuth and elevation axes and the corresponding adaptive controllers with adjustable parameters tuned according to Lyapunov-based adaptation mechanisms are employed. The optimal value of the fractional order is obtained through an integral square error performance index minimization. The moments products uncertainties are incorporated in the design procedure. The numerical simulations demonstrate that the proposed control approach is robust against the moments products variations. [ABSTRACT FROM AUTHOR]

The interaction simulations between particles and structures are often performed in the context of the combined discrete-finite element (DEM-FEM) method, where an efficient, robust and accurate contact algorithm for challenging contact problems is essential. A three-dimensional (3D) discrete and finite element contact algorithm, named ZGL here, has been proposed in our research group (Zang, M.Y. et al., 2011. A contact algorithm for 3D discrete and finite element contact problems based on penalty function method. Comput. Mech. 48, 541–550.). Despite being quite well-established, ZGL algorithm may lack efficiency, robustness and accuracy in certain situations, e.g., when special mesh pattern is applied. However, since such cases are readily to appear in practice engineering application, an algorithm named DZCell is developed to resolve these issues and thus significantly applicable to challenging contact problems. The proposed DZCell algorithm includes an improved global phase to directly find the potential segments rather than the nearest node for discrete elements as contact counterparts. Furthermore, both the memory cost and time consumption of this algorithm are linear, and the algorithm is readily to extend to parallel computing. Several numerical examples demonstrate the achievable improvements in terms of efficiency, robustness and accuracy for 3D contact analysis and validate the capability of the DZCell algorithm in the granular science and mechanical engineering. [ABSTRACT FROM AUTHOR]

This paper studies a class of robust cooperative learning control problems for directed networks of agents (a) with nonidentical nonlinear dynamics that do not satisfy a global Lipschitz condition and (b) in the presence of switching topologies, initial state shifts and external disturbances. All uncertainties are not only time-varying but also iteration-varying. It is shown that the relative formation of nonlinear agents achieved via cooperative learning can be guaranteed to converge to the desired formation exponentially fast as the number of iterations increases. A necessary and sufficient condition for exponential convergence of the cooperative learning process is that at each time step, the network topology graph of nonlinear agents can be rendered quasi-strongly connected through switching along the iteration axis. Simulation tests illustrate the effectiveness of our proposed cooperative learning results in refining arbitrary high precision relative formation of nonlinear agents. [ABSTRACT FROM AUTHOR]

Communication networks are used in load frequency control (LFC) for transmitting remote measurements and control commands, and in demand side response (DSR) for aggregating small-scale controllable loads. This paper investigates modeling and controller design for LFC together DSR in a deregulated environment, considering multiple time delays introduced by the usage of communication channels. Time delay model of the deregulated multi-area LFC with dynamic demand control (DDC) is obtained at first, in which a typical thermostatically controlled appliance, air conditioner, is used for DDC. A robust proportional integral derivative (PID) load frequency controller is designed, through theH∞performance analysis and the particle swarm optimization (PSO) searching algorithm, to deal with the load disturbances and multiple delays in the LFC loop and the DDC loop. Case studies based on a three-area deregulated LFC system demonstrate the effectiveness of the proposed load frequency controller and the performance improvement from the DDC. Simulation results show that the DDC can increase the delay margin of the LFC scheme. Moreover, several delay stable regions are revealed via simulation method. [ABSTRACT FROM AUTHOR]

One important mission of strategic defense is to develop an integrated layered Ballistic Missile Defense System (BMDS). Motivated by the queueing theory, we presented a work for the representation, modeling, performance simulation, and channels optimal allocation of the layered BMDS M/M/N queueing systems. Firstly, in order to simulate the process of defense and to study the Defense Effectiveness (DE), we modeled and simulated the M/M/N queueing system of layered BMDS. Specifically, we proposed the M/M/N/N and M/M/N/C queueing model for short defense depth and long defense depth, respectively; single target channel and multiple target channels were distinguished in each model. Secondly, we considered the problem of assigning limited target channels to incoming targets, we illustrated how to allocate channels for achieving the best DE, and we also proposed a novel and robust search algorithm for obtaining the minimum channel requirements across a set of neighborhoods. Simultaneously, we presented examples of optimal allocation problems under different constraints. Thirdly, several simulation examples verified the effectiveness of the proposed queueing models. This work may help to understand the rules of queueing process and to provide optimal configuration suggestions for defense decision-making. [ABSTRACT FROM AUTHOR]

This paper investigates the control performance of pounding tuned mass damper (PTMD) in reducing the dynamic responses of SDOF (Single Degree of Freedom) structure. Taking an offshore jacket-type platform as an example, the optimal damping ratio and the gap between mass block and viscoelastic material are presented depending on a parametric study. Control efficiency influenced by material properties and contact geometries for PTMD is analyzed here, as well as robustness of the device. The results of numerical simulations indicated that satisfactory vibration mitigation and robustness can be achieved by an optimally designed PTMD. Comparisons between PTMD and traditional TMD demonstrate the advantages of PTMD, not only in vibration suppression and costs but also in effective frequency bandwidth. [ABSTRACT FROM AUTHOR]

This paper proposes a new local texture descriptor, called quad binary pattern (QBP). Compared with local binary pattern (LBP), the QBP is with stronger robustness for feature extraction under complex scene (e.g., luminance change, similar target and background color) and with lower computational complexity. To demonstrate its effectiveness, the proposed QBP is further applied on the mean-shift tracking, in which a joint color-QBP model is developed to effectively represent the color and texture characteristics of the target region. Extensive simulation results have demonstrated that the proposed algorithm is able to improve the tracking speed and accuracy, compared with the standard mean-shift tracking and joint color-LBP model based mean-shift tracking. [ABSTRACT FROM AUTHOR]

Coordination between a specific mobile robot type has been widely investigated, e.g coordination between unicycles. To extend the applicability of the system, a coordinated trajectory tracking of mixed type of mobile robots is considered. We prove that if a certain type of wheeled mobile robot is able to individually track its own reference, then coordination in tracking with other type of robots can be achieved simply by sharing individual tracking errors. Using two types of wheeled mobile robots, namely unicycle types (a nonholonomic mobile robot) and omni wheels type (a holonomic mobile robot), a coordinated control algorithm can achieve a global asymptotically stable condition of the error dynamics of the systems. Under bidirectional communication between robots as a constraint, the group is able to maintain individual tracking while coordinating the movements with other robots regardless occurring perturbations in the system and delays in communication channels. Simulation results suggest that information sharing between the robots increase the robustness in coordinating individual trajectories. Results also show that delays cause drop in performance similar to the case of no information sharing. [ABSTRACT FROM AUTHOR]

This paper presents a composite control strategy integrating adaptive sliding-mode control and the linear quadratic regulator (LQR) technology for a wheeled inverted pendulum (WIP) vehicle system. The system can be partitioned into an actuated rotational subsystem and an underactuated longitudinal subsystem based on the different control input in the mathematical model. In particular, the instability analysis of zero dynamic for the underactuated longitudinal subsystem is investigated in detail using the feedback linearisation technology. Then, an adaptive sliding-mode control is designed for the trajectory tracking, where an adaptive algorithm is developed to handle with the parameter uncertainties. In addition, the LQR technique is employed to guarantee zero dynamics stability so as to achieve simultaneously the vehicle body stabilisation at the upright position. Simulation results show the good performance and strong robustness of the proposed control schemes. [ABSTRACT FROM AUTHOR]

In line of the research on leader-following consensus, this paper studies the consensus problem for the first-order multi-agent system with a smart leader. Different from previous works where the leader is independent of all the other agents, a kind of leader, called smart leader, is proposed, which can gain and utilize its neighboring followers' position information. Whether such information will be used in adjusting the control algorithm for the smart leader is decided by an event-trigger function. The theory and simulation results show that the proposed model can gain advantage in robustness and fault-tolerance ability with the traditional one. Moreover, a sufficient condition is provided, which can ensure that the position-tracking error and velocity-tracking error are bounded when some actuator faults occur on some of the followers in the framework of the fixed topology. In addition, similar results are also given under switching topology. Finally, some simulation examples are presented for illustration. [ABSTRACT FROM AUTHOR]

This paper presents a robust H ∞ output-feedback vehicle lateral motion control strategy considering network-induced delay and tire force saturation. The unavoidable time delay in the in-vehicle networks degrades the control performance, and even deteriorates the system stability. In addition, the tire lateral force suffers saturation phenomenon, which also deteriorates the control effect in extreme driving conditions. To handle the network-induced control delay and tire force saturation, a robust H ∞ controller is presented to regulate the vehicle lateral motion. An output-feedback control schema, which does not need the vehicle lateral velocity, is designed to achieve the desired control performance and reduce the cost of control system. The tire cornering stiffness uncertainty and external disturbances are also considered in the controller design to improve the robustness of the proposed controller. The comparative simulation results based on Carsim-Simulink joint simulation verify the effectiveness and robustness of the proposed control strategy. [ABSTRACT FROM AUTHOR]

In this paper, we consider the problem of quickly detecting an unknown change in the conditional densities of a dependent stochastic process. In contrast to the existing quickest change detection approaches for dependent stochastic processes, we propose minimax robust versions of the popular Lorden, Pollak, and Bayesian criteria for when there is uncertainty about the parameter of the post-change conditional densities. Under an information-theoretic Pythagorean inequality condition on the uncertainty set of possible post-change parameters, we identify asymptotic minimax robust solutions to our Lorden, Pollak, and Bayesian problems. Finally, through simulation examples, we illustrate that asymptotically minimax robust rules can provide detection performance comparable to the popular (but more computationally expensive) generalized likelihood ratio rule. [ABSTRACT FROM PUBLISHER]

This paper investigates the dynamics analysis and robust control law design for the proposed schematic design of electric unicycles. The schematic design of the proposed unicycle possesses a supportive seat for the rider and is also equipped with a handling rod for maneuvering, similar to a Segway device. First, this paper conducts an analysis and comparison of the dynamics properties and derivation of the nonlinear governing equation for the unicycle. Next, it emphasizes the development of an input-constrained robust controller design for the proposed configuration of the electric unicycle. The issues investigated in this paper include the dynamics property analysis and comparison, nonlinear dynamics derivation, robust control diagram formulation, controller synthesis regarding linear matrix inequalities (LMIs), and time response simulations and discussions. In this control law design via LMIs, the desired performances of: (1) relative stability or decay rate for command tracking capability; (2) disturbance attenuation for robustness against uncertainty parameters; and (3) an accommodation of control effort constraints under the regulation or command tracking of certain initial state condition are investigated and demonstrated using time response simulations of the controlled unicycle dynamics. [ABSTRACT FROM AUTHOR]

An adaptive extended Kalman filter is designed to estimate the arc length in a gas metal arc welding system. The simulation results show that the estimated variables track the true variables of the non-linear model with negligible error and are robust against parameters uncertainties. The proposed estimator also operates adequately in a highly noisy welding environment. Because of the low computational requirements and little lag produced in the process dynamic, use of the proposed estimator would be valuable in the design of a controller for the gas metal arc welding system. [ABSTRACT FROM AUTHOR]

The robust fuzzy control for fractional-order hydroturbine regulating system is studied in this paper. First, the more practical fractional-order hydroturbine regulating system with uncertain parameters and random disturbances is presented. Then, on the basis of interval matrix theory and fractional-order stability theorem, a fuzzy control method is proposed for fractional-order hydroturbine regulating system, and the stability condition is expressed as a group of linear matrix inequalities. Furthermore, the proposed method has good robustness which can process external random disturbances and uncertain parameters. Finally, the validity and superiority are proved by the numerical simulations. [ABSTRACT FROM AUTHOR]

Satellite remote sensing image target matching recognition exhibits poor robustness and accuracy because of the unfit feature extractor and large data quantity. To address this problem, we propose a new feature extraction algorithm for fast target matching recognition that comprises an improved feature from accelerated segment test (FAST) feature detector and a binary fast retina key point (FREAK) feature descriptor. To improve robustness, we extend the FAST feature detector by applying scale space theory and then transform the feature vector acquired by the FREAK descriptor from decimal into binary. We reduce the quantity of data in the computer and improve matching accuracy by using the binary space. Simulation test results show that our algorithm outperforms other relevant methods in terms of robustness and accuracy. [ABSTRACT FROM AUTHOR]

The existing Block Compressive Sensing (BCS) based image ciphers adopted the same sampling rate for all the blocks, which may lead to the desirable result that after subsampling, significant blocks lose some more-useful information while insignificant blocks still retain some less-useful information. Motivated by this observation, we propose a scalable encryption framework (SEF) based on BCS together with a Sobel Edge Detector and Cascade Chaotic Maps. Our work is firstly dedicated to the design of two new fusion techniques, chaos-based structurally random matrices and chaos-based random convolution and subsampling. The basic idea is to divide an image into some blocks with an equal size and then diagnose their respective significance with the help of the Sobel Edge Detector. For significant block encryption, chaos-based structurally random matrix is applied to significant blocks whereas chaos-based random convolution and subsampling are responsible for the remaining insignificant ones. In comparison with the BCS based image ciphers, the SEF takes lightweight subsampling and severe sensitivity encryption for the significant blocks and severe subsampling and lightweight robustness encryption for the insignificant ones in parallel, thus better protecting significant image regions. [ABSTRACT FROM AUTHOR]

Modern engine exhaust restriction valves can be applied not only as retarders. A suitable pressure generation can assist the aftertreatment system (exhaust gas temperature management) and raw emission control as well. To provide these functionalities the exhaust backpressure has to be controlled arbitrarily. In this paper a model-based controller design is demonstrated to minimize calibration effort. A first engineering principle based, mean-value, nonlinear model was described and converted into linear parameter-varying (LPV) form. To satisfy the demands of the above applications the controller needs to be a high dynamic, stabilizing, tracking controller which is robust in the whole relevant engine operation range. The exhaust processes of the individual cylinders generate comparable amplitude pressure oscillations to the expected control accuracy. To fulfill the above requirements and manage the challenge of the exhaust pressure waves an H-infinity controller design method was chosen. In order to handle the saturation of the control signal a high gain anti-windup was applied. Seeking for the lowest possible computational demand the controller order reduction was proposed based on Hankel singular values. Finally the controller performance was demonstrated and evaluated in software-in-the-loop simulations. [ABSTRACT FROM AUTHOR]

For the satellite attitude estimation problem, the serious model errors always exist and hider the estimation performance of the Attitude Determination and Control System (ACDS), especially for a small satellite with low precision sensors. To deal with this problem, a new algorithm for the attitude estimation, referred to as the unscented predictive variable structure filter (UPVSF) is presented. This strategy is proposed based on the variable structure control concept and unscented transform (UT) sampling method. It can be implemented in real time with an ability to estimate the model errors on-line, in order to improve the state estimation precision. In addition, the model errors in this filter are not restricted only to the Gaussian noises; therefore, it has the advantages to deal with the various kinds of model errors or noises. It is anticipated that the UT sampling strategy can further enhance the robustness and accuracy of the novel UPVSF. Numerical simulations show that the proposed UPVSF is more effective and robustness in dealing with the model errors and low precision sensors compared with the traditional unscented Kalman filter (UKF). [ABSTRACT FROM AUTHOR]

An assembly supply chain network (ASCN) is composed of manufacturers located in different geographical regions. To analyze the robustness of this ASCN when it suffers from catastrophe disruption events, we construct a cascading failure model of risk propagation. In our model, different disruption scenarios s are considered and the probability equation of all disruption scenarios is developed. Using production capability loss as the robustness index (RI) of an ASCN, we conduct a numerical simulation to assess its robustness. Through simulation, we compare the network robustness at different values of linking intensity and node threshold and find that weak linking intensity or high node threshold increases the robustness of the ASCN. We also compare network robustness levels under different disruption scenarios. [ABSTRACT FROM AUTHOR]

A novel output feedback dynamic excitation control scheme is proposed for efficient load angle trajectory tracking tasks for synchronous generators. In this way, effective tracking of reference trajectories for the state variables and electric power is also guaranteed. The introduced control design approach is robust against parametric uncertainty, unmodelled dynamics, and variable mechanical power input commonly present in practical electric power systems. The control scheme only requires measurements of the load angle variable, and state and disturbance estimation is properly avoided. Computer simulation results are included to show the controller robustness and the satisfactory reference trajectory tracking specified for the machine operation for both continuous and switched control voltage signals. [ABSTRACT FROM AUTHOR]

Monitoring quality of production processes is a complex task consisting of different measurements of product properties and process parameters, as well as visual checks and other activities. One of the most important measurement tasks is measuring complex product geometry. In order to get information about measured quantities as quickly as possible, measurements are made directly on the shop floor. However, assuring traceability of complex co-ordinate measurements in uncontrolled shop floor conditions is an advanced metrological task requiring special measurement standards and procedures. European project EMRP IND62 TIM that was agreed between EC and European metrology association Euramet is aimed to introduce a traceability chain into in-process geometrical measurements by offering different solutions for calibrating machine tools in harsh environmental conditions. One of the tasks of this project was to develop a highly accurate robust 1D measurement standard with very low expansion coefficient. The article presents basic design of this standard and experimental verification of its thermal expansion characteristics in a laboratory, as well as in harsh environment in production companies. Thermal expansion verification was performed by means of measurements on a co-ordinate measuring machine at different temperatures simulating real shop floor conditions. [ABSTRACT FROM AUTHOR]

Dynamic behaviour of a micro-cantilever beam under periodic electro-thermal loading is studied in this paper. For certain applications the beam is required to vibrate at a particular frequency. Modal analysis using 3D finite element is used in order to find the geometrical parameters that makes fundamental frequency of the beam match the required frequency. Then non-linear dynamic thermoelastic analysis is conducted on the system to analyse the time-history (transient) behaviour of the beam and record its tip displacement. However, due to uncertainties and non-repeatabilities that are inherent properties of the system along with those associated with the manufacturing, final product is likely to have deviations from these estimated values (fundamental frequency and tip displacement). Thus, choosing a nominal (desired) design and studying the deviation in natural frequency and tip displacement via 2k factorial Design-of-Experiments (DOE), effect of uncertainties on the overall performance of the system is investigated. This allows finding the significance of individual parameters on the overall robustness of the design as well as potential interactions between various parameters. Finally, the expected behaviour of the micro-cantilever and its robustness to design and implementation uncertainties are elaborated and statements for robust design of this system are made. [ABSTRACT FROM AUTHOR]

This paper presents a data-driven receding horizon fault estimation method for additive actuator and sensor faults in unknown linear time-invariant systems, with enhanced robustness to stochastic identification errors. State-of-the-art methods construct fault estimators with identified state-space models or Markov parameters, without compensating for identification errors. Motivated by this limitation, we first propose a receding horizon fault estimator parameterized by predictor Markov parameters. This estimator provides (asymptotically) unbiased fault estimates as long as the subsystem from faults to outputs has no unstable transmission zeros. When the identified Markov parameters are used to construct the above fault estimator, stochastic identification errors appear as model uncertainty multiplied with unknown fault signals and online system inputs/outputs (I/O). Based on this fault estimation error analysis, we formulate a mixed-norm problem for the offline robust design that regards online I/O data as unknown. An alternative online mixed-norm problem is also proposed that can further reduce estimation errors at the cost of increased computational burden. Based on a geometrical interpretation of the two proposed mixed-norm problems, systematic methods to tune the user-defined parameters therein are given to achieve desired performance trade-offs. Simulation examples illustrate the benefits of our proposed methods compared to recent literature. [ABSTRACT FROM AUTHOR]

This paper proposes, for a class of uncertain nonlinear systems, an adaptive controller based on adaptive second-order sliding mode control and integral sliding mode control concepts. The adaptation strategy solves the problem of gain tuning and has the advantage of chattering reduction. Moreover, limited information about perturbation and uncertainties has to be known. The control is composed of two parts: an adaptive one whose objective is to reject the perturbation and system uncertainties, whereas the second one is chosen such as the nominal part of the system is stabilised in zero. To illustrate the effectiveness of the proposed approach, an application on an academic example is shown with simulation results. [ABSTRACT FROM AUTHOR]

Event-triggering strategy is one of the real-time control implementation techniques which aims at achieving minimum resource utilisation while ensuring the satisfactory performance of the closed-loop system. In this paper, we address the problem of robust stabilisation for a class of nonlinear systems subject to external disturbances using sliding mode control (SMC) by event-triggering scheme. An event-triggering scheme is developed for SMC to ensure the sliding trajectory remains confined in the vicinity of sliding manifold. The event-triggered SMC brings the sliding mode in the system and thus the steady-state trajectories of the system also remain bounded within a predesigned region in the presence of disturbances. The design of event parameters is also given considering the practical constraints on control execution. We show that the next triggering instant is larger than its immediate past triggering instant by a given positive constant. The analysis is also presented with taking delay into account in the control updates. An upper bound for delay is calculated to ensure stability of the system. It is shown that with delay steady-state bound of the system is increased than that of the case without delay. However, the system trajectories remain bounded in the case of delay, so stability is ensured. The performance of this event-triggered SMC is demonstrated through a numerical simulation. [ABSTRACT FROM AUTHOR]

This work presents the design and implementation of a power-efficient 2-tap feed-forward voltage mode driver which has impedance tuning and signal conditioning capabilities. The driver has a robust mechanism to match its impedance to the line impedance even when signal conditioning is enabled which minimizes reflection and improves signal quality. A mixed signal approach that detects and compensates for NMOS and PMOS transistor resistance variation is presented. An analog circuit detects the driver's resistance variation, and a digital circuit controls an analog compensation circuit to maintain line impedance matching for all signal conditioning configurations of the driver. When maximum signal conditioning is enabled, the driver can transmit a 40 Gbits/sec PRBS7 signal through a 10 in. FR4 channel. It achieves a differential eye-opening amplitude of 100 mVppd and an eye-opening width of 0.8 UI consuming 9.7 mW of at-speed power. Simulations demonstrate that worst case impedance deviation from 50 Ω due to process, voltage and temperature variation is 2.7%. The driver is designed in 28 nm CMOS process using a 0.85 V nominal supply voltage. It is simulated using HSPICE circuit simulator and mixed mode simulations tools. [ABSTRACT FROM AUTHOR]

In optical interference-based encryption (IBE) scheme, the currently available methods have to employ the iterative algorithms in order to encrypt two images and retrieve cross-talk free decrypted images. In this paper, we shall show that this goal can be achieved via an analytical process if one of the two images is QR code. For decryption, the QR code is decrypted in the conventional architecture and the decryption has a noisy appearance. Nevertheless, the robustness of QR code against noise enables the accurate acquisition of its content from the noisy retrieval, as a result of which the primary QR code can be exactly regenerated. Thereafter, a novel optical architecture is proposed to recover the grayscale image by aid of the QR code. In addition, the proposal has totally eliminated the silhouette problem existing in the previous IBE schemes, and its effectiveness and feasibility have been demonstrated by numerical simulations. [ABSTRACT FROM AUTHOR]