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Quadratic Volterra filters are shown to be very effective in image sharpening applications. The linear combination of polynomial terms, however, yields poor performance in noisy environments. Weighted median filters, in contrast, are well-known for their outlier suppression and detail preservation properties. The weighted median sample selection methodology is naturally extended to the polynomial...
Standard analysis and synthesis techniques for digital control systems assume that the total time-delay in the feedback loop is negligible or precisely known. This might not be the case in some applications. Such systems are quite common in industry, especially due to strong trends towards networking. Under certain circumstances the network-induced delays can be considered constant, and yet it might...
The family of characteristic polynomials of a SISO-PID loop with N representative plant operating conditions is Pi = Ai(s)(KI; + Kps + KDs2) + Bi(s), i = 1,2…N. A basic task of robust control design is to find the set of all parameters KI, KP, KD, that simultaneously place the roots of all Pi(a) into a specified region Γ in the complex plane. For Γ in form of the left half plane it is known that the...
We tackle the problem of controlling a mechanical system by means of a robust discrete-time linear predictive control which is the discrete time version of the Robust Generalized Proportional Integral Control. It is assumed that the model uncertainties and external disturbances are bounded and bandlimited, so that they can be modeled by means of a polynomial approximation which needs to be rejected...
The paper describes a design methodology which allows dynamic and parametric modelling uncertainty to be treated simultaneously. It combines the advantages of H∞ control techniques with those provided by robust design methods based on a polytopic representation of parametric uncertainty. The proposed method uses the Q-parameterization of all solutions of the H∞ control problem in addition to the robust...
This paper is concerned with the stability and control of linear systems with uncertain physical parameters. The case where the characteristic equations of the systems are polynomially dependent on uncertain parameters is studied. A new algorithm is presented for the calculation of stability margins in the parameter space in general / p-norms. The stability is defined with respect to a desired region...
The solution of a H2/H∞ stochastic feedback and feedforward optimal control problem is discussed where the structure of the controller is assumed to be fixed apriori. The controller may be chosen to be of reduced order, lead/lag, or PID forms, and the optimal causal controller is required to minimize H2 or H∞ cost-indices. The continuous-time system includes at tracking controller and a feedforward...
This paper presents a design scheme of robust parallel com. for multi-input multi-output plants with structured uncertainty such that the closed-loop system realizes strict positive realness using the static output feedback. A systematic desi i scheme which includes determining procedure of the parameters of the compensator is developed. An example is presented to show the design procedures and to...
High performance control of fluid actuator system depends on several important choices, like the model on which the synthesis is based and the control criteria. In the case of the optimal LQG control design, the choice of the weighting matrices determines the closed-loop performances and robustness. In the present paper a methodology of LQG synthesis inspired from the literature is applied on an electro-pneumatic...
This paper1 presents a method to estimate a Decision Feedback Equalizer (DFE) directly from training data, which is robust w.r.t. time-variations in the communication channel. It is based on the indirect method proposed in [15], where the time variations in the channel are modeled as a probabilistic uncertainty. The robust DFE optimizes the performance by minimizing the mean squared error averaged...
The design of run-of-river hydro-plant automation remains a challenge in combined terms of performance and security. This paper presents an innovative methodology, based on one hand on identification through available measurements, and on the other hand on a control structure including a local water level control added to a feed-forward action. The water level controller, developed from the continuous-time...
This paper considers robust control with a stable controller using proportional-integral-plus control techniques. A formulation of robust PIP controllers is proposed on the basis of parametric pole assignment. The robustness function in the frequency domain is minimised using the freedom provided by parametric pole assignment. It shows how to combine time-domain performance specifications provided...
A proof of a strengthened version of the phase growth condition for Hurwitz stable polynomials is given. Based on this result, a necessary and sufficient condition for a polynomial p(s) to be a local convex direction for a Hurwitz stable polynomial q(s) is obtained. The condition is in terms of polynomials associated with the even and odd parts of p(s) and q(s).
The robust stabilization of a family of stochastic plants described by interval ARMAX models is here considered. The solution proposed is given by a linear, time-varying compensator and by a supervisor. The compensator may assume a finite number of different, possible configurations, at least one of the which stabilizes the actual unknown ARMAX model. The task of the supervisor is to determine the...
Adaptive controllers based on high gain feedback suffer from lack of robustness with respect to bounded disturbances. Existing modifications prevent the feedback gain from drifting, but introduce solutions that, even in the absence of disturbances, do not achieve regulation. In this paper a further modification that maintains the robustness and rules out undesirable solutions when disturbances are...
We propose a method to compute invariant subsets of the robust region-of-attraction for the asymptotically stable equilibrium points of systems with polynomial nominal vector fields and unmodeled dynamics. The effects of unmodeled dynamics are accounted for as systems satisfying certain gain relations or dissipation inequalities. The methodology is extended to systems with parametric uncertainties...
Given a nominal plant, together with a fixed neighborhood of this plant, the problem of robust stabilization is to find a controller that stabilizes all plants in that neighborhood (in an appropriate sense). If a controller achieves this design objective, we say that it robustly stabilizes the nominal plant. In this paper we formulate the robust stabilization problem in a behavioral framework, with...
We consider shielding critical links to guarantee network connectivity under geographical and general failure models. We develop a mixed integer linear program (MILP) to obtain the minimum cost shielding to guarantee the connectivity of a single SD pair under a general failure model, and exploit geometric properties to decompose the shielding problem under a geographical failure model. We extend our...
Integrated servo-mechanical design is commonly solved using numerical methods. In this paper, allowable regions for the redesigned open loop Nyquist plot are derived based on performance and chance-constrained robust stability specifications, considering high-frequency reshaping of the mechanical plant based on a low-order controller. Our simulation results on the Pb-Zr-Ti active suspension in a commercial...
The main objective of the present work is to investigate the robust stability analysis aspect of Sun Seeker System (SSS) under parametric uncertainties. In this paper robust stability analysis of closed loop block diagram of a SSS is presented with and without proportional-integral-derivative (PID) controller. Transfer functions are derived for both SSS systems i.e., with and without PID controller...
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