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Aiming at the problem of distributed target detection when there is signal mismatch, this paper proposes a tunable detector, which is characterised by a tunable parameter. The proposed detector can realise the flexible detection of mismatch signals by adjusting the tunable parameter, and hence the directivity (robustness or selectivity to mismatched signals) of the tunable detector can be smoothly adjusted. In addition, the tunable detector can obtain approximately the same detection performance as the corresponding generalised likelihood ratio test in the absence of signal mismatch. The proposed tunable detector also possesses the constant false alarm rate property. Numerical examples illustrate the effectiveness of the proposed detector. [ABSTRACT FROM AUTHOR]

SUMMARY To design highly efficient and robust detectors of a weak signal, an asymptotic approach to stable estimation exploiting redescending score functions is used. Two new indicators of robustness of detection, the detection error sensitivity and detection stability, are introduced. The optimal Neyman-Pearson rules maximizing detection efficiency under the guaranteed level of detection stability are written out. Under heavy-tailed noise distributions, the proposed asymptotically stable detectors based on redescending score functions, namely, the minimum error sensitivity and the radical ones, outperform conventional linear bounded Huber's and redescending Hampel's detectors both on small and large samples. Copyright © 2013 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

Automatic design of synthetic gene circuits poses a significant challenge to synthetic biology, primarily due to the complexity of biological systems, and the lack of rigorous optimization methods that can cope with the combinatorial explosion as the number of biological parts increases. Current optimization methods for synthetic gene design rely on heuristic algorithms that are usually not deterministic, deliver sub-optimal solutions, and provide no guaranties on convergence or error bounds. Here, we introduce an optimization framework for the problem of part selection in synthetic gene circuits that is based on mixed integer non-linear programming (MINLP), which is a deterministic method that finds the globally optimal solution and guarantees convergence in finite time. Given a synthetic gene circuit, a library of characterized parts, and user-defined constraints, our method can find the optimal selection of parts that satisfy the constraints and best approximates the objective function given by the user. We evaluated the proposed method in the design of three synthetic circuits (a toggle switch, a transcriptional cascade, and a band detector), with both experimentally constructed and synthetic promoter libraries. Scalability and robustness analysis shows that the proposed framework scales well with the library size and the solution space. The work described here is a step towards a unifying, realistic framework for the automated design of biological circuits. [ABSTRACT FROM AUTHOR]

In this paper, the problem of attitude control of a three dimension nonlinear flexible spacecraft is investigated. Two nonlinear controllers are presented. The first controller is based on dynamic inversion, while the second approach is composed of dynamic inversion and µ-synthesis schemes. It is assumed that only three torques in three directions on the hub are used. Actuator saturation is also considered in the design of controllers. To evaluate the performance of the proposed controllers, an extensive number of simulations on a nonlinear model of the spacecraft are performed. The performances of the proposed controllers are compared in terms of nominal performance, robustness to uncertainties, vibration suppression of panel, sensitivity to measurement noise, environmental disturbance and nonlinearity in large maneuvers. Simulation results confirm the ability of the proposed controller in tracking the attitude trajectory while suppressing the panel vibration. It is also verified that the perturbations, environment disturbances and measurement errors have only slight effects on the tracking and suppression performances. Copyright © 2010 John Wiley and Sons Asia Pte Ltd and Chinese Automatic Control Society [ABSTRACT FROM AUTHOR]

In this paper, a new simple derivation of all stabilizing proportional controllers, for first order linear time invariant systems with time-delay, is presented. Although several results based on the Hermite-Biehler theorem for finding such a set of controllers exist, the aim of this article is to present a shorter and more instructive derivation, which can be followed easily. Copyright © 2010 John Wiley and Sons Asia Pte Ltd and Chinese Automatic Control Society [ABSTRACT FROM AUTHOR]

In this study, Sliding Mode Control (SMC) and High Order Sliding Mode Control (HOSMC) methods are applied to a single Flexible Link Robot Arm (FLA) with payload. A sliding mode and high order sliding mode controllers are designed to achieve set point precision positioning control and trajectory tracking control for a FLA. Flexible robot arms have structural flexibilities and resulting high number of passive degrees-of-freedom. They cannot be decoupled due to the highly nonlinear structure. Since the flexible systems have highly nonlinear structure and coupled dynamics, the sliding mode based control approach is chosen a powerful method to overcome the unmodeled and parametric uncertainties. One of the proposed controllers is 2nd order HOSMC method is compared with classical SMC method. Comparison of the methods is experimentally fulfilled using HIL simulator, and additionally torque ripple analysis is made to evaluate of the methods aspect from system harmonics. Direct drive motors are used as actuator in controlled systems. Of all system dynamics affect system harmonics via motor shaft due to the direct drive system that is no gear box. Therefore, harmonics analysis is crucial to investigate of designed controllers effects on system harmonics. To precise set-point and trajectory tracking control of 1-DOF DD FLA has been derived SMC and HOSMC. Sliding Mode Controllers (SMCs) have the robustness properties, while also increasing accuracy by reducing chattering effects. The performance of the designed control methods are tested for the precise position and targeting control of a 1- DOF-DD-FLA system under heavy uncertainties. Comparative results of both methods have been evaluated in real-time using a Hardware-in-the- Loop (HIL) simulator designed for robotics. Especially, HIL simulator for this system includes DD motors and obtained results can be evaluated more realistically according to pure computer simulations Additionally, torque ripples of whole system with HIL simulator have been determined and their eliminations using for both methods are introduced. HIL simulator is used to implement designed controller for a flexible-link arm. Direct drive joint motors are important parts of the direct drive underactuated robot manipulators. Therefore two DD motors take part in HIL simulator and couple through their shaft. One of the motors represents joint actuator, while the other motor is used for generation of the dynamics of the controlled system via the torque applied to the shaft. The two motors acting as "actuator" and "load torque simulator" are driven separately by a high performance controller board. HIL Simulator is expressed briefly as software that is modeled control algorithm and system dynamic model via controller board is integrated with hardware. HIL simulation differs from computer simulation as it involves actual hardware and is not limited with a software-based representation of the system.… [ABSTRACT FROM AUTHOR]

Abstract: An improved auto-tuning scheme is proposed for Ziegler–Nichols (ZN) tuned PID controllers (ZNPIDs), which usually provide excessively large overshoots, not tolerable in most of the situations, for high-order and nonlinear processes. To overcome this limitation ZNPIDs are upgraded by some easily interpretable heuristic rules through an online gain modifying factor defined on the instantaneous process states. This study is an extension of our earlier work [Mudi RK., Dey C. Lee TT. An improved auto-tuning scheme for PI controllers. ISA Trans 2008; 47: 45–52] to ZNPIDs, thereby making the scheme suitable for a wide range of processes and more generalized too. The proposed augmented ZNPID (AZNPID) is tested on various high-order linear and nonlinear dead-time processes with improved performance over ZNPID, refined ZNPID (RZNPID), and other schemes reported in the literature. Stability issues are addressed for linear processes. Robust performance of AZNPID is observed while changing its tunable parameters as well as the process dead-time. The proposed scheme is also implemented on a real time servo-based position control system. [Copyright &y& Elsevier]

In this paper, based on the local information about nodes, we propose a new attack strategy, considering the average degree of the node's neighboring nodes. Adopting the cascading model proposed in Chin. Phys. Lett.25(10) (2008) 3826, we investigate the effect of the new attack strategy for the robustness against cascading failures on a typical network, i.e. BA scale-free networks. Compared with two attacks on the nodes with the highest load or the lowest load, numerically we find that our presented attack is the most efficient way to destruct the BA scale-free networks in the case of α ≤ 0.6, where α is a tunable parameter and determines to the load strength of a node. In addition, we also find that the efficiency of the new attack strategy is more obvious near the parameter α = 0.5. We expect our findings to provide insights into the protection of the key nodes for real-life networks to avoid cascading-failure-induced disasters. [ABSTRACT FROM AUTHOR]

The problem of controlling a perturbed open loop system so as to keep its performance errors within bounds is considered. The objective is to maximise the time during which performance errors remain below a prescribed ceiling, while the controlled system's parameters are within a specified neighbourhood of their nominal values. It is shown that there is an optimal open loop controller that achieves this objective. Conditions under which the optimal controller generates a bang-bang control input signal are characterised. In general, it is shown that the performance of the optimal controller can always be approximated by a bang-bang signal. [ABSTRACT FROM AUTHOR]

Abstract: This paper presents a robust adaptive fuzzy control algorithm for controlling unknown chaotic systems. The control approach encompasses a fuzzy system and a robust controller. The fuzzy system is designed to mimic an ideal controller, based on sliding-mode control. The robust controller is designed to compensate for the difference between the fuzzy controller and the ideal controller. The parameters of the fuzzy system, as well as uncertainty bound of the robust controller, are tuned adaptively. The adaptive laws are derived in the Lyapunov sense to guarantee the stability of the controlled system. Numerical simulations show the effectiveness of the proposed approach. [Copyright &y& Elsevier]

Abstract: In this paper, a method is proposed for the adaptive model predictive control of constrained nonlinear system. Rather than relying on the inherent robustness properties of standard NMPC, the developed technique explicitly account for the transient effect of parametric estimation error by combining a parameter adjustment mechanism with robust MPC algorithms. The parameter estimation routine employed guarantees non-increase of the estimation error vector. This means that the controller employs a process model which approaches that of the true system over time. These estimates are used to update the parameter uncertainty set at every time step, resulting in a gradual reduction in the conservative and/or computational effects of the incorporated robust features. [Copyright &y& Elsevier]

A robust control-oriented modelling approach for networked controlled systems (NCS) with uncertain, varying, bounded transmission delays and asynchronous discrete-time control laws is presented. The resulting model is then used for the derivation of sufficient conditions for the robust stability of NCSs and the computation of the maximum allowable delay (constrained within one sampling period) that the closed-loop system can tolerate given a pre-selected set of stabilising gains for the nominally delayed system. The derived stability conditions can be used for both open-loop stable and unstable systems and are numerically simple to use because they rely on singular-value calculations and the solution of a standard discrete Lyapunov equation. The impact of certain designer choices (such as sampling period, nominal delay and tuning parameters appearing in the stability conditions) on the delay range is also investigated. Simulation studies are used to investigate the efficiency of the derived robust stability bound. [ABSTRACT FROM AUTHOR]

This paper is concerned with the robust H∞ filtering problem for uncertain switched linear discrete-time systems. Combining the mode-switching idea with the well-known Finsler's lemma, and further utilising the parameter-dependent result, a new characterisation of the asymptotic stability with an H∞ noise-attenuation level bound for the filtering error system has been addressed. The existence condition of such a filter is formulated in terms of dilated linear matrix inequalities. This directly leads to performance improvement and reduction of conservativeness in the filtering solution. Performance of the presented approach in comparison with that of the existing results is illustrated by a numerical example. [ABSTRACT FROM AUTHOR]

Based on a general controller evaluation method, taking both performance and robustness in different frequency regions into account, an analytical PID design method is presented. It is related to the well known and often used lambda tuning approach, which is based on internal model control (IMC) for a specific second-order non-minimum phase plant model. The analytical method introduced in this paper includes two tuning parameters, one that guarantees a specified stability margin for the given model, and one that is also able to adjust the control activity to a desired level. The suggested method, called robust IMC, gives the user the important freedom to control both mid- and high-frequency robustness. An extended evaluation procedure also illustrates how efficiently PI and PID controllers including a Smith predictor (SP) can control time delayed plants. More specifically, it is shown to be more profitable to provide a PI controller with derivative action than with a SP for plants with long time delays. [ABSTRACT FROM AUTHOR]

A feature detector and a feature descriptor are presented, which are applicable to 3D range data. The feature detector is used to identify locations in the range data at which the feature descriptor is applied. The feature descriptor, or feature transform, calculates a signature for each identified location on the basis of local shape information. The approach used in both the feature detector and the descriptor is motivated by the success of the scale invariant feature transform and speeded up robust features approaches in the 2D case. Using synthetic data, the authors evaluate the repeatability of the detector and robustness of the descriptor to global transformations and image noise. The complete system is then applied to the problem of automatic detection of repeated structure in real range images. [ABSTRACT FROM AUTHOR]

Abstract: This paper investigates the feedback stabilization problem for SISO linear uncertain control systems with saturating quantized measurements. In the fixed quantization sensitivity framework, we propose a time varying control law able to effectively account for the presence of saturation, which is often the main source of instability, designed using sliding mode techniques. Such controller is proved able to stabilize the plant both in the presence and in the absence of quantization. [Copyright &y& Elsevier]

Abstract: In this paper, we examine the statistical properties of the holographic watermarking system [C.J. Cheng, L.C. Lin, W.T. Dai, Opt. Commun. 248 (2005) 105] and facilitate a systematic way to determine an optimal threshold of the correlation signal for detecting the authorized mark pattern. The holographic watermarking system constructs a digital holographic watermark using modified Mach–Zehnder interferometric architecture, and the correlation signal is obtained using an optical VanderLugt 4-f correlator to identify the authorized mark in the watermarked image. To obtain the best detection performance, we use statistical modeling of the entire holographic watermarking system. Accordingly, we derive correlation signal statistics and hypothesis testing to obtain an optimal threshold for the watermark detector that minimizes the detection error. The theoretical result of this paper allows us to easily determine an optimal threshold and evaluate the robustness of the watermark detector. The robustness of the proposed optimal detector is evaluated using detection error, and detection performance is demonstrated by simulation experiments. [Copyright &y& Elsevier]

Abstract: This paper presents the solvability conditions for the global robust output regulation problem for lower triangular nonlinear systems assuming the control direction is unknown. The approach used is an integration of the robust stabilization technique and Nussbaum gain technique. [Copyright &y& Elsevier]

This paper investigates two situations in which the forward kinematics of planar 3-RP_R parallel manipulators degenerates. These situations have not been addressed before. The first degeneracy arises when the three input joint variables ρ1, ρ2, and ρ3 satisfy a certain relationship. This degeneracy yields a double root of the characteristic polynomial in t=tan(φ/2), which could be erroneously interpreted as two coalesce assembly modes. However, unlike what arises in nondegenerate cases, this double root yields two sets of solutions for the position coordinates (x,y) of the platform. In the second situation, we show that the forward kinematics degenerates over the whole joint space if the base and platform triangles are congruent and the platform triangle is rotated by 180 deg about one of its sides. For these “degenerate” manipulators, which are defined here for the first time, the forward kinematics is reduced to the solution of a third-degree polynomial and a quadratic in sequence. Such manipulators constitute, in turn, a new family of analytic planar manipulators that would be more suitable for industrial applications. [ABSTRACT FROM AUTHOR]

Based on the Lie-group-algebraic properties of the displacement set, the three-degree-of-freedom (3DOF) pseudoplanar motion often termed Y motion for brevity is first introduced. Then, all possible general architectures of the mechanical generators of a given Y subgroup are obtained by implementing serial arrays of 1DOF Reuleaux pairs or hinged parallelograms. In total, five distinct mechanical generators of Y motion are revealed and seven ones having at least one parallelogram are also derived from them. In order to avoid the singularity that may occur in the limbs, all singular postures of Y-motion generators are also located by detecting the possible linear dependency of the joint twists and the group dependency of displacement sets. The parallel layout of three 4DOF limbs including Y-motion generators with orthogonal planes make up a Cartesian translational parallel manipulator, which produces a motion set of spatial translations. The 3DOF translation of the moving platform is directly controlled by the three 1DOF translations in three orthogonal prismatic fixed joints. [ABSTRACT FROM AUTHOR]

This paper presents a methodology for design of dissipative assist robots with proven stability during set-point control. A dissipative assist robot is defined as one where the actuators continuously dissipate energy from the robot until the robot reaches the desired set point. We have discussed in this paper that, under well known control laws, it is hard to characterize dissipativity of a general assist robot. However, by appropriately designing the robot through inertia redistribution, the dynamic equations can be modified so that the control laws can now be proven to be both dissipative and stable under set-point control. The proposed method is demonstrated through simulation of a three-link planar manipulator used as an assist robot to modify human functional movements in a vertical plane. [ABSTRACT FROM AUTHOR]

Abstract: In this paper, we consider the robust stabilization problem for linear discrete time-varying (LTV) systems using the gap metric. In particular, we show that the time-varying (TV) directed gap reduces to an operator with a TV Hankel plus Toeplitz structure. Computation of the norm of such an operator can be carried out using an iterative scheme involving a TV Hankel operator defined on a space of Hilbert–Schmidt causal operators. The “infimization” in the TV directed gap formula is shown to be, in fact, a minimum by using duality theory. The latter holds as well in the time-invariant case. [Copyright &y& Elsevier]

Abstract: In this paper we address the problem of designing the feedforward block of a two degrees of freedom controller in the case of single input single output (SISO) discrete-time linear systems with model uncertainty. In this work the design of the feedforward filter is formulated as a robust model matching problem. First, a closed form solution of the optimal noncausal filter, which minimizes the worst-case model matching error for each , is obtained. Then, suitable rational stable approximations of the optimal solution are derived either by means of causal filters or, when a preview of the reference signal is available, by means of noncausal FIR filters. The efficiency of the proposed method is tested on a simulated example. [Copyright &y& Elsevier]

With system parameters falling into a certain area, power system with excitation limits experiences complicated chaotic oscillations which threaten the secure and stable operation of power system. In this paper, to control these unwanted chaotic oscillations, a straightforward adaptive chaos controller based on Lyapunov asymptotical stability theory is designed. Since the presented controller does not need to change the controlled system structure and not to use any information of system except the system state variables, the designed controller is simple and desirable. Simulation results show that the proposed control law is very effective. This work is helpful to maintain the power system's security operation. [ABSTRACT FROM AUTHOR]

This paper is concentrated on a perturbed vehicle control system whose gain margin (GM) and phase margin (PM) are analyzed and for which a novel controller design method satisfying the given specifications on GM, PM, and sensitivity is developed. The approach is applied to the plants with uncertain parameters that vary in intervals. Based on the parameter space method and robust stability criteria, gain and phase boundary curves are generated from the characteristic polynomial of the system with which a gain-phase tester is included in series to perform system stability analysis and controller design. The main concern in the controller design is to find a region in the controller coefficient plane so that the performance of the uncertain system satisfies given specifications. The proposed method is applied to an example of a bus system. Simulation results are given for illustration to show the system performances on GM and PM, and the desired controller meeting the specified conditions in frequency domain for the perturbed system is derived. [ABSTRACT FROM AUTHOR]

The present paper proposes an alternative performance index for the design of robust controllers to damp low-frequency electromechanical oscillations in power systems. The concept of output energy is used as performance index as opposed to the usual criterion of minimum damping ratio. The control problem with both performance indices was structured in the form of linear matrix inequalities and it was verified that the formulation with the output energy is less costly in terms of computational effort when compared to the one with the traditional minimum damping ratio. This characteristic allows the application of the proposed methodology to controller design involving large power system models. The design methodology is based on a multimachine model, without requiring the assumption that some part of the system can be modelled as an infinite bus. Such assumption is usual in control designs based on many modern control techniques, and may modify the dynamics described by the system model and consequently affect the performance of the designed controllers. The design methodology provides controllers that fulfill various practical requirements of the oscillation problem. The methodology has provided effective controllers with acceptable performance as shown in the results, and the gain in computational time was significant. [ABSTRACT FROM AUTHOR]

Abstract: The internal model control (IMC) design method for stable plants has enjoyed much popularity due to its simple yet effective procedure. However, there are some shortcomings and inadequacies with the IMC design method for both stable and unstable plants which will be exposed in this paper. We propose a new control design method that somehow captures the useful properties of the IMC design method but can be used for both stable or unstable plants (LTI, SISO) in a coherent framework. Moreover, some restrictive assumptions on the plant are relaxed and some of the IMC shortcomings and limitations are tackled. [Copyright &y& Elsevier]

The paper presents a cascade generalized predictive controller. The cascade control task is performed by one predictive controller and the cascade feature is incorporated in a special predictor. Simulation results are presented comparing the performances of the proposed control algorithm to traditional cascade loops including two PI or two GPC controllers. The paper investigates the effects of noise filter on the robustness of the control loops in the cascade control structure. It shows, that with the proposed predictor it is possible to adjust independently the robustness of the inner and outer loops, meanwhile in the traditional cascade loop there are cross effects in this sense. Finally a real time application of the proposed algorithm is presented: the cascade GPC was tested in the oxygen control loop of an experimental fluidized bed boiler. [ABSTRACT FROM AUTHOR]

An application of a new controller order reduction technique with stability and performance preservation based on linear matrix inequality optimization to an active suspension system is presented. In this technique, the rank of the residue matrix of a proper rational approximation of a high-order H∞ controller subject to the H∞-norm of a frequency-weighted error between the approximated controller and the high-order H∞ controller is minimized. However, because solving this matrix rank minimization problem is very difficult, the rank objective function is replaced with a nuclear-norm that can be reduced to a semidefinite program so that it can be solved efficiently. Application to the active suspension system of the Automatic Laboratory of Grenoble provides a fourth-order controller. The experimental results show that the control specifications are met to a large extent. [ABSTRACT FROM AUTHOR]

Abstract: A controller change from a current controller which stabilises the plant to a new controller, designed on the basis of an approximate model of the plant and with guaranteed bounds on the stability properties of the true closed loop, is called a safe controller change. In this paper, we present a model reference approach to the determination of safe controller changes on the basis of approximate closed loop models of the plant and robust stability results in the -gap. [Copyright &y& Elsevier]

Abstract: This paper considers the problem of delay-dependent robust control for uncertain systems with time-varying delays. An improved delay-dependent bounded real lemma (BRL) for time-delay systems is established in terms of a linear matrix inequality. Based on the obtained BRL, a delay-dependent condition for the existence of a state feedback controller, which ensures asymptotic stability and a prescribed performance level of the closed-loop system for all admissible uncertainties, is proposed in terms of a matrix inequality. [Copyright &y& Elsevier]

This paper presents a novel control method for the stabilization of railway bogies using a strategy based on the concept of an absolute stiffness, in which the control effort is proportional to the yaw movement of the wheelset alone. The idea can be considered as if a spring is connected between the sky and a wheelset, hence termed a 'sky-hook spring'. In this paper, the effectiveness of the control strategy is studied in detail and compared with other control solutions. It is shown that the new approach offers a number of advantages: it provides a robust control solution for the stability of railway wheelsets and there is no need for the measurement of bogie motions or the use of secondary yaw dampers. Sensing requirement can be readily met and control design is relatively simple. [ABSTRACT FROM AUTHOR]

Abstract: The failure signatures of a grounded-base NPN bipolar ESD protection under multiple TLP and HBM stresses are analyzed. For this particular device having a graded collector region, multiple TLP or HBM stresses result in different types of defects. OBIC techniques and TCAD simulations are used to thoroughly analyze the involved physical mechanisms. [Copyright &y& Elsevier]

This paper is devoted to the design of robust controllers for sliding mode control systems. A linear fractional transformation (LFT) framework is adopted to describe the systems subject to model uncertainties and external disturbances. A linear matrix inequality (LMI) technique is then developed into the design of both sliding mode and reaching phase control laws. It is shown that by solving a set of LMIs, the switching surface can be designed such that the dynamics in the sliding mode achieve robust stability and bounded L 2 gain performance with respect to matched and unmatched uncertainties in the presence of disturbances. Furthermore, a reaching phase control law is presented to eliminate the undesirable chattering effect and maintain the robustness property all the time whether the system evolves into its sliding mode in finite time or not. Finally, an observer based control law is also developed to achieve the robust performance during the reaching phase. The results are illustrated by an example. [ABSTRACT FROM AUTHOR]

Abstract: It is shown that a general uncertain single-input–single-output regulation problem is solvable only by means of discontinuous control laws, giving rise to the so-called high-order sliding modes. The homogeneity properties of the corresponding controllers yield a number of practically important features. In particular, finite-time convergence is proved, and asymptotic accuracy is calculated in a very general way in the presence of input noises, discrete measurements and switching delays. A robust homogeneous differentiator is included in the control structure thus yielding robust output-feedback controllers with finite-time convergence. It is demonstrated that homogeneity features significantly simplify the design and investigation of a new family of high-order sliding-mode controllers. Finally, simulation results are presented. [Copyright &y& Elsevier]

This paper presents a hybrid control approach to circumvent the basic trade-off between performance and robustness from an individual controller. This hybrid control strategy utilizes a robust controller for guaranteed robustness when the plant model is not well known, and employs an adaptive controller for high performance after sufficient plant information has been collected. To avoid a degraded transient after controller switching, a bumpless transfer scheme is designed and incorporated into this hybrid control approach. This bumpless transfer design is an extension from a conventional latent tracking bumpless transfer design for a single-input single-output (SISO) plant with 1 degree of freedom (DOF) controllers to either a SISO plant with multiple DOF controllers or a multi-input multi-output (MIMO) plant. Experimental results implemented on an active vibration isolation testbed demonstrate the effectiveness of the proposed hybrid control strategy. [Copyright &y& Elsevier]

A multiple bifurcation phenomena is observed in a two-area example power system. A local bifurcation and an inter-area bifurcation develop because of the multiple bifurcation parameter changes. The dynamic behaviors of the bifurcating system are complex due to the overlapping of the two different bifurcation subsystems and are shown to be difficult to control. The double bifurcations are studied in this paper and in order to stabilize them, three kinds of μ-synthesis robust controls are designed: 1) p-synthesis power system stabilizer (MPSS); 2) μ-synthesis SVC control (MSVC); and 3) a mixed MPSSIMSVC control. Based on the bifurcation subsystem analysis, the measurement signals and locations of the controls are selected. The control performances and the RGA matrix information of three kind of controls are compared. The conclusions are given according to the analysis and lime simulation results. [ABSTRACT FROM AUTHOR]

A robust optimal preview control method is presented in this paper for path tracking control problems to improve robustness and tracking precision of path tracking control systems. The known path information is used as reference input signals. Simulation results show that this method is valid not only for improving the performance of highly accurate trajectory control but also for improving system stabilization. [ABSTRACT FROM AUTHOR]

An approach for improving the quality of bounds on the structured singular value in the case of mixed real and complex uncertainty models is described. The proposed approach uses constrained non-linear optimization to improve the lower bound on μ generated by standard commercially available algorithms. A similar approach is used to compute more reliably bounds on the peak value of μ for problems that give rise to sharp peaks in the μ plot as a function of frequency. Both approaches are shown to be simple and computationally efficient to implement, and their practical usefulness is demonstrated on the problem of checking a stability margin clearance criterion for a V/STOL (vertical/short take-off and landing) aircraft flight control law. [ABSTRACT FROM AUTHOR]

This paper presents a novel method for increasing the robustness of visual tracking systems by incorporating information from inertial sensors. We show that more can be achieved than simply combining the sensor data within a statistical filter: besides using inertial data to provide predictions for the visual sensor, this data can be used to dynamically tune the parameters of each feature detector in the visual sensor. This allows the visual sensor to provide useful information even in the presence of substantial motion blur. Finally, the visual sensor can be used to calibrate the parameters of the inertial sensor to eliminate drift. [Copyright &y& Elsevier]

The problem of determination of conditions of robust stabilization of linear stationary objects with prescribed multiple estimates of their parameters, is studied. This means, we consider the problem of finding existence conditions of such linear feedback by the state vector, which ensures asymptotic stability of the whole class of closed-loop discrete control systems. On the basis of sufficient conditions of asymptotic stability of linear discrete systems of this class of control systems, easily verified conditions of robust stabilization are derived. [ABSTRACT FROM AUTHOR]

Criteria based on disturbance rejection and system robustness are proposed to assess the performance of PID controllers. The robustness is measured by a two-block structured singular value, and the disturbance rejection is measured by the minimum singular value of the integral gain matrix. Examples show that the criteria can be applied to a variety of processes, whether they are stable, integrating, or unstable and single-loop or multi-loop. [ABSTRACT FROM AUTHOR]

The problem of designing a transmit pulse such that after transmission over a dispersive channel the received pulse fits in a prescribed template can be formulated as a quadratic programming problem with affine semi-infinite constraints. In constrained optimisation, the optimal solution invariably lies on the boundary of the feasible set, and consequently perturbations on the optimal solution or the constraints means that the received pulses may no longer fit in the template. Perturbations to the optimal transmit pulse and the constraints arise, in practice, from errors in the implementation and uncertainty in the channel parameter, respectively. In the paper, a robust formulation is presented which ensures that the constraints are satisfied even in the presence of implementation errors and channel parameter uncertainty. The technique developed is applied to determine the optimal transmit pulse shape to be programmed on a commercial T1 (1.544 Mbit/s) line interface unit. [ABSTRACT FROM AUTHOR]

Presents the development of a fault tolerant control (FTC) strategy to compensate for the degrading effects of fluid leakage across a faulty actuator piston seal in an electrohydraulic positioning system. Description of the experimental test station; Development of nonlinear dynamic equations governing the motion of the experimental system; Application of the quantitative feedback theory to develop the set of local control laws; Outline of a simple control law switching scheme; Demonstration on the efficacy of the local controllers as well as the switching scheme.

In this paper a new VSS control law using a combination of feedforward control and VSS control for systems having unknown parts is proposed. The full dynamic model of the manipulator is generated, a very robust VSS control method is proposed, and the stability and the tracking error convergence of the model are analyzed by means of Lyapunov stability theory. The tracking error closed loop system is stable and the error converges asymptotically to zero. A modification of the VSS control method to deal with external disturbances is proposed. The validity of the proposed method is shown by simulations. © 1998 Scripta Technica. Electron Comm Jpn Pt 3, 81(2): 60–68, 1998 [ABSTRACT FROM AUTHOR]

An adaptive lattice filter for filtering impulsive noise is designed using a cyclic enzyme system. The cyclic enzyme system has a memory mechanism and can maintain the previous output for some duration independently of the system input. The partial autocorrelation (PARCOR) coefficient computed through the system is then robust against impulsive noise that appears as large spikes of short duration. Furthermore, a set of PARCOR coefficients estimated by the new filter is always stable. The effectiveness is investigated analytically and through computer simulation. [ABSTRACT FROM AUTHOR]

This paper considers a plant with structured uncertainties, such as one with a transfer function where the denominator and the numerator, respectively, are represented by a convex combination of two polynomials. A necessary and sufficient condition for the robust stabilization is presented, and the systematic design method for the compensator is shown. Key words: Uncertain system; feedback control; robust stabilization; Hurwitz polynomial; interpolation. [ABSTRACT FROM AUTHOR]