Abstract: This paper considers the passivity-based control problem for stochastic jumping systems with mode-dependent round-trip time-varying delays and norm-bounded parametric uncertainties. By utilizing a novel Markovian switching Lyapunov functional, a delay-dependent passivity condition is obtained. Then, based on the derived passivity condition, a desired Markovian switching dynamic output feedback controller is designed, which ensures the resulting closed-loop system is passive. Finally, two numerical examples are provided to illustrate the effectiveness of the proposed results.

Abstract: A novel Passivity-Based Stability Criterion (PBSC) is proposed for the stability analysis and design of DC power distribution systems. The proposed criterion is based on imposing passivity of the overall bus impedance. If passivity of the overall DC bus impedance is ensured, stability is guaranteed as well. The PBSC reduces artificial design conservativeness and sensitivity to component grouping typical of existing stability criteria, such as the Middlebrook criterion and its extensions. Moreover, the criterion is easily applicable to multi-converter systems and to systems in which the power flow direction changes, for example as a result of system reconfiguration. Moreover, the criterion can be used for the design of active damping networks for DC power distribution systems. The approach results in greatly improved stability and damping of transients on the DC bus voltage. Experimental validation is performed using a hardware test-bed that emulates a DC power distribution system.

Abstract: We investigate input passivity and output passivity for a generalized complex network with non-linear, time-varying, non-symmetric and delayed coupling. By constructing some suitable Lyapunov functionals, several sufficient conditions ensuring input passivity and output passivity are derived for complex dynamical networks. Finally, two numerical examples are given to show the effectiveness of the obtained results.

Abstract: This paper focuses on the temperature control in a multi-zone building. The lumped heat transfer model based on thermal resistance and capacitance is used to analyze the system dynamics and control strategy. The resulting thermal network, including the zones, walls, and ambient environment, may be represented as an undirected graph. The thermal capacitances are the nodes in the graph, connected by thermal resistances as links. We assume the temperature measurements and temperature control elements (heating and cooling) are collocated. We show that the resulting input/output system is strictly passive, and any passive output feedback controller may be used to improve the transient and steady state performance without affecting the closed loop stability. The storage functions associated with passive systems may be used to construct a Lyapunov function, to demonstrate closed loop stability and motivates the construction of an adaptive feedforward control. A four-room example is included to illustrate the performance of the proposed passivity based control strategy.

Abstract: In this paper, the problem of passivity analysis for uncertain neural networks with time-varying delays is considered. By constructing an augmented Lyapunov–Krasovskii’s functional and some novel analysis techniques, improved delay-dependent criteria for checking the passivity of the neural networks are established. The proposed criteria are represented in terms of LMIs (linear matrix inequalities) which can be easily solved by various convex optimization algorithms. Two numerical examples are included to show the superiority of our results.

Abstract: SUMMARY This paper deals with the problems of passivity analysis and passivity-based controller design for Markovian jump systems with both time-varying delays and norm-bounded parametric uncertainties. Firstly, new delay-dependent conditions for the considered system to be passive are obtained by using a mode-dependent Lyapunov functional and by introducing some slack variables. These conditions are expressed by means of LMIs that are easy to check. It is shown through a numerical example that the obtained passivity conditions are less conservative than the existing ones in the literature. Secondly, the passification problem is investigated. On the basis of the obtained passivity conditions, dynamic output-feedback controllers are designed, which ensure that the resulting closed-loop system is passive. The effectiveness of the proposed design method is demonstrated by a numerical example. Copyright © 2011 John Wiley & Sons, Ltd.

Abstract: The robust control of a system which is nominally passive, but experiences a passivity violation is considered in this paper. Specifically, we utilize the hybrid passivity and finite gain stability theorem to robustly control a single-link flexible manipulator experiment. This system is nominally passive, but passivity is destroyed by, for example, sensor dynamics. The hybrid theorem is specifically applicable to such a scenario. We review and develop further the hybrid passivity and finite gain stability theorem in a linear time-invariant, single-input-single-output context. Calculation of the various passivity and finite gain parameters that classify a system as hybrid is discussed. In the interest of developing a hybrid controller that is optimal in some sense, we pose a numerical optimization problem which is constrained by the hybrid passivity and finite gain stability theorem. The numerical optimization objective function seeks to have a hybrid controller mimic a nominal controller. Experimental results successfully demonstrate tip-based feedback control of a single-link flexible manipulator.

Abstract: Passivity is an important property of circuits and systems to guarantee stable global simulation. Nonetheless, nonpassive models may result from passive underlying structures due to numerical or measurement error/inaccuracy. A postprocessing passivity enforcement algorithm is therefore desirable to perturb the model to be passive under a controlled error. However, previous literature only reports such passivity enforcement algorithms for pole-residue models and regular systems (RSs). In this paper, passivity enforcement algorithms for descriptor systems (DSs, a superset of RSs) with possibly singular direct term (specifically, D+DT or I-DDT) are proposed. The proposed algorithms cover all kinds of state-space models (RSs or DSs, with direct terms being singular or nonsingular, in the immittance or scattering representation) and thus have a much wider application scope than existing algorithms. The passivity enforcement is reduced to two standard optimization problems that can be solved efficiently. The objective functions in both optimization problems are the error functions, hence perturbed models with adequate accuracy can be obtained. Numerical examples then verify the efficiency and robustness of the proposed algorithms.

Abstract: This study addresses the control of boost converters applied for power-factor correction in universal-line applications, using adaptive non-linear control based in passivity. The controller design is independent of the operating point and the gains of the control law have a clear physical interpretation. Discussion of the control approach with unknown load is provided. Robustness analysis of the proposed approach and comparison with standard approaches are made. The performance of the proposed power factor correction (PFC) rectifier was evaluated on an experimental 630 W universal-line PFC prototype.

Abstract: In this study is approached the design problem of a control law for an asymmetric nine-level multilevel cascade inverter when it is implemented as active filter for harmonic current mitigation purposes. Two are the main features of the proposed controller, namely, its structure is defined considering at a fundamental level the precise establishment, in terms of mathematical expressions, of the steady-state converter behaviour required to achieve the control objective and its stabilisation properties, that render this desired steady-state behaviour attractive (asymptotically stable), are obtained by exploiting the energy-dissipation (passivity) properties of the circuit. These features lead to a simple controller structure that is easy to tune. The stability, high performance and robustness properties of the presented control scheme are experimentally evaluated.

Abstract: Passivity-based control of under-actuated mechanical systems with nonlinear friction effects in the generalized coordinates of motion is analyzed in this paper Nonlinear friction is modeled with a

Abstract: A novel passivity enforcement technique for passive component modeling subject to variations of geometrical parameters is proposed using combined neural networks and rational functions. A constrained neural network training process to enforce passivity of Y-parameters is introduced. Eigenvalues of Hamiltonian matrix for parametric model at many geometrical samples are used simultaneously as constraints for neural network training. Furthermore, a new passivity conditioning parameter e is proposed to guide the training process. Once trained, the parametric model can provide accurate, fast and passive behavior of passive components for various values of geometrical variables within the model training range. A parametric modeling example of an interdigital capacitor is presented to demonstrate the validity of the proposed technique.

Abstract: This paper is concerned with the problem of passivity-based control for Markovian jump systems via retarded output feedback controllers. A delay-dependent passivity criterion is obtained in terms of linear matrix inequalities. Based on this, a sufficient condition is proposed for the design of a retarded output feedback controller which ensures that the closed-loop system is passive. By using the sequential linear programming matrix method, a desired retarded output feedback controller can be constructed. Numerical examples are provided to demonstrate the advantage and effectiveness of the proposed method.

Abstract: This paper presents a class of nonsmooth convex optimization methods for the passivity enforcement of reduced-order macromodels of electrical interconnects, packages, and linear passive devices. Model passivity can be lost during model extraction or identification from numerical field solutions or direct measurements. Nonpassive models may cause instabilities in transient system-level simulation, therefore a suitable postprocessing is necessary in order to eliminate any passivity violations. Different from leading numerical schemes on the subject, passivity enforcement is formulated here as a direct frequency-domain H∞ norm minimization through perturbation of the model state-space parameters. Since the dependence of this norm on the parameters is nonsmooth, but continuous and convex, we resort to the use of subdifferentials and subgradients, which are used to devise two different algorithms. We provide a theoretical proof of the global optimality for the solution computed via both schemes. Numerical results confirm that these algorithms achieve the global optimum in a finite number of iterations within a prescribed accuracy level.

Abstract: This article studies incremental passivity and the output tracking problem for switched nonlinear systems. The concept of incremental passivity for switched systems is given using the proposed weak-storage functions. Furthermore, conditions for a switched nonlinear system to be incrementally passive are obtained without the requirement of the incremental passivity conditions for subsystems. It is shown that once the incremental passivity is assured, the output tracking problem for switched systems is solvable via the designed controllers, even though the problem for none of subsystems is solvable.

Abstract: This paper presents a new passivity enforcement technique for linear time-invariant multiport systems generated from tabulated measured or simulated data. Traditional methods based on iterative eigenvalue/singular value perturbation do not guarantee convergence, and the error introduced is sometimes large due to the lack of explicit error control. The key to the new algorithm is to correct passivity violations locally with moderate increase of system size. Since all violations are fixed locally, the impact on system transfer function outside the passivity violating frequency range is minimized. Thus, the convergence issue is avoided and the accuracy degradation due to passivity enforcement can also be minimized. The proposed method is very efficient, as optimization procedures are not required. Experimental results demonstrate its performance.

Abstract: In impedance-type haptic interfaces, encoders are typically employed to provide high resolution position measurements from which velocity is estimated, most commonly via the finite difference method (FDM). This velocity estimation technique performs reliably, unless very fast sampling is required, in which case noise or delay due to filtering of the position signals reduces accuracy in the estimate. Despite this limitation, FDM is attractive because it is a passive process, and therefore the passivity of the overall system can be guaranteed. Levant's differentiator is a viable alternative to FDM, and exhibits increased accuracy in velocity estimation at high sample rates compared to FDM. However, the passivity of this nonlinear velocity estimation technique cannot be shown using conventional methods. In this paper, we employ a time domain passivity framework to analyze and enforce passive behavior of Levant's differentiator for haptic displays in discrete time. The performance of this approach is explored both in simulation and experimentally on a custom made one degree-of-freedom haptic interface. Results demonstrate the effectiveness of the time domain passivity approach for compensating the active behavior observed with use of Levant's differentiator for velocity estimation.

Abstract: This paper is concerned with passivity analysis and passivity-based controller design for uncertain singularly perturbed Markovian jump systems with time-varying delay in an interval. Firstly, a delay-dependent condition for the considered system to be mean-square exponentially stable and robustly passive is derived in terms of linear matrix inequality. Then, the passification problem is investigated. Based on the obtained passivity condition, the existence of the desired state feedback controller is established. Numerical examples are presented to show the effectiveness of the proposed method.

Abstract: We present an efficient and scalable framework for the generation of guaranteed passive compact dynamical models for multiport structures. The proposed algorithm enforces passivity using frequency independent linear matrix inequalities, as opposed to the existing optimization based algorithms which enforce passivity using computationally expensive frequency dependent constraints. We have tested our algorithm for various multiport structures. An excellent match between the given samples and our passive model was achieved.

Abstract: Most transient circuit simulators are based on admittance representations of the constituent circuit elements. It is therefore natural to use admittance parameter descriptions of linear networks, preferably in the form of rational transfer functions that can be directly implemented in the analysis. A problem arises when the measured or calculated frequency-domain response of a linear distributed network must be derived from data that has inherent error, is of limited bandwidth, or is not in the appropriate rational form. A reduced-order rational model that is causal, stable, and passive must be developed. Previous methods of deriving rational functions for the admittance parameters of a network do guarantee stability and causality, but passivity of the model must be assured through subsequent post-processing. Enforcing passivity requires modification of the state-space parameters of the model with consequent introduction of errors. This paper reports on a procedure to simultaneously achieve passivity, accuracy, causality, and stability in the development of an admittance macromodel described using a matrix of rational functions. An iterative inverse eigenvalue algorithm enforces passivity, and is applied by conjoining sets of eigenvalue and admittance constraints. These constraints form a monolithic projection matrix, which simultaneously addresses both passivity and accuracy of the model.

Abstract: Stable linear time-invariant systems can be made passive by a feedforward action. In this article, an analytical approach to obtain the matrix which allows to enforce passivity in the system is proposed. This matrix depends only on one parameter, namely α. The introduced method is based on the calculation of the characteristic polynomial of the Hamiltonian matrix associated to the Positive Real problem. This polynomial is then used to derive a finite set of values of the parameter α, in which the value assuring passivity enforcement with minimum dissipation can be selected. Numerical examples are reported.

Abstract: To obtain good dynamic and steady state performances, a passivity-based controller was developed on the basis of the state-space average model of the Buck-Boost converter. The Buck-Boost converter with the passivity-based controller has the fast response and small output ripple, but has difficulty in achieving the output voltage regulation to a desired constant level on the condition of the wide input voltage. Aiming at solving the problem, a passivity-based adaptive control strategy was presented. The Buck-Boost converter adopting the passivity-based adaptive control strategy was simulated and the experiment was carried in the airfield lighting power. The results showed that the converter not only meets the dynamic and steady-state performance, but also has a strong robustness to the disturbance of the wide input voltage.

Abstract: Passivity of metals was initially stated by Faraday1 and Schoenbein2 over 150 years ago. The origin of the passivity was argued and at the present the passivity is thought to be the formation of three dimensional oxide films. It is stably formed in aqueous solution. The passive oxides are extremely thin (usually a few nm), so it is very difficult to detect them analytical techniques. For the quantitative description, electrochemistry is a key technology, because the oxidation state of the metal surface can be precisely controlled by electrochemical apparatus. Since the electrochemical control is restricted into solution phase, the passivated surface should be characterized in the same phase. To overcome the difficulty for characterization, several optical techniques have been applied.

Abstract: This article presents a new passivity-based control law that stabilizes the output voltage of a high-order DC-DC converter. Such nonlinear control law assures robust large-signal stability, provides zero steady-state error despite uncertainty in converter parameters and has enough degree of freedom to satisfy the usual transient specifications of DC-DC converters. This new integral control is derived in three steps. First, a static law is obtained. Second, a positive semidefinite storage function is synthesized to guarantee zero steady-state error of the output voltage. Finally, the storage functions of the first two steps are combined to derive the new control law for high-order DC-DC converters. Copyright © 2011 John Wiley and Sons Asia Pte Ltd and Chinese Automatic Control Society

Abstract: The output characteristics of photovoltaic (PV) cell is nonlinear, changing along with the change of external environment factors. In order to improve photovoltaic system's work efficiency, it's necessary to track the maximum power point. Considering single-stage three-phase photovoltaic grid-connected system as the research object, this paper analyzes the output characteristics of photovoltaic cell and operating principle of the system, and also designs passivity-based power controller. Meanwhile, the Incremental Conductance(INC) method based on power control is applied to the MPPT control, making the system response to the change of external environment quickly and accurately, so that the system is always working in the maximum power point. The Matlab/Simulink simulation results show that this method is feasible.

Abstract: It is shown that the alternate passivity-based control schemes can be designed which explicitly exploit the passivity properties of the Timoshenko model. This approach has the advantage over the conventional methods in the respect that it allows one to deal directly with the system's partial differential equations without resorting to approximations. Numerical results for the tracking control of a translational and rotational flexible Timoshenko arm are presented and compared. They verify that the proposed control schemes are effective at controlling flexible dynamical systems.