Abstract: This paper considers a complex dynamical network model, in which the input and output vectors have different dimensions. We, respectively, investigate the passivity and the relationship between output strict passivity and output synchronization of the complex dynamical network with fixed and adaptive coupling strength. First, two new passivity definitions are proposed, which generalize some existing concepts of passivity. By constructing appropriate Lyapunov functional, some sufficient conditions ensuring the passivity, input strict passivity and output strict passivity are derived for the complex dynamical network with fixed coupling strength. In addition, we also reveal the relationship between output strict passivity and output synchronization of the complex dynamical network with fixed coupling strength. By employing the relationship between output strict passivity and output synchronization, a sufficient condition for output synchronization of the complex dynamical network with fixed coupling strength is established. Then, we extend these results to the case when the coupling strength is adaptively adjusted. Finally, two examples with numerical simulations are provided to demonstrate the effectiveness of the proposed criteria.

Abstract: In this note, we address the problem of stabilization of port-Hamiltonian systems via the ubiquitous proportional-integral-derivative (PID) controller. The design is based on passivity theory, hence the first step is to identify all passive outputs of the system, which is the first contribution of the paper. Adding a PID around this signal ensures that the closed-loop system is ${\mathcal L}_2$ -stable for all positive PID gains. Global stability (and/or global attractivity) of a desired constant equilibrium is also guaranteed for a new class of systems for which a Lyapunov function can be constructed. A second contribution is to prove that this class—that is identified via some easily verifiable integrability conditions—is strictly larger than the ones previously reported in the literature. Comparisons of the proposed PID controller with control-by-interconnection passivity-based control are also discussed.

Abstract: This paper respectively studies finite-time passivity of multi-weighted coupled neural networks (MWCNNs) with and without coupling delays. First, based on those existing passivity definitions, several new concepts about finite-time passivity are presented. By exploiting these definitions of finite-time passivity and designing appropriate controllers, we investigate the passivity of MWCNNs with and without coupling delays. In addition, some sufficient conditions to guarantee finite-time synchronization of MWCNNs with constant and delayed couplings are obtained under the condition that the MWCNNs is finite-time passive. Finally, two examples are also given to verify the proposed finite-time passivity and synchronization criteria.

Abstract: This paper deals with the problem of achieving consensus of multiple Euler–Lagrange (EL) systems using the energy shaping plus damping injection principles of passivity-based control. It proposes a novel decentralized controller that is capable of solving the leaderless and the leader–follower consensus problems in networks of fully actuated EL-systems with interconnecting time-varying delays and without employing velocity measurements. This paper also presents a comparative simulation study with different controllers and provides experimental evidence of the performance of the novel controller.

Abstract: This paper focuses on delay-dependent passivity analysis for a class of memristive impulsive inertial neural networks with time-varying delays. By choosing proper variable transformation, the memristive inertial neural networks can be rewritten as first-order differential equations. The memristive model presented here is regarded as a switching system rather than employing the theory of differential inclusion and set-value map. Based on matrix inequality and Lyapunov-Krasovskii functional method, several delay-dependent passivity conditions are obtained to ascertain the passivity of the addressed networks. In addition, the results obtained here contain those on the passivity for the addressed networks without impulse effects as special cases and can also be generalized to other neural networks with more complex pulse interference. Finally, one numerical example is presented to show the validity of the obtained results.

Abstract: A method to passivate a given system by using an input–output transformation matrix is introduced. This matrix generalizes the commonly used methods of series, feedback, and feedforward to passivate a linear or nonlinear system. Through an appropriate design of this matrix, positive passivity indices can be guaranteed for the system. Furthermore, this transformation matrix allows the use of a nonpassive system as a controller to guarantee the passivity and finite-gain $\mathcal{L}_2$ stability of a negative feedback configuration. The passivation parameters can be selected to improve system performance. The results are illustrated by considering nonlinear systems and linear systems with input/output delay. To validate the theory, simulation results in CarSim and Simulink are presented.

Abstract: Passivity is a canonical condition for the safety of interactive systems, but practical limitations restrict its utility as a design tool. A system with a passive model can be unstable in high-stiffness environments, passivity is difficult to show with inner-loop controllers, and as it is a binary condition it provides limited design comparison insight; as a result, it is rarely used for inner-loop design. As passivity safety claims are limited by model accuracy, conditions for the passivity of a system with bounded-magnitude model uncertainty (robust passivity) are developed in this paper. Additionally, a condition for coupled environment–robot stability is developed using mixed passivity and small-gain condition, allowing rigorous relaxation of passivity at high frequencies for typical impedance-controlled systems. These approaches are used in the analysis of an impedance-controlled series-elastic actuated system with inner-loop torque control and also compared with traditional design tools (bandwidth ratio, sensitivity function, etc.). The approach is then validated experimentally, identifying model uncertainty bounds under various load conditions, and then using the measured uncertainty for controller synthesis. Robust passivity is then compared with nominal passivity in a validation experiment under manual excitation and impact.

Abstract: Chaotic oscillation in a power system is considered the main cause of power blackouts in large-scale interconnected power grids. The chaotic oscillation mechanisms and the control methods for chaos oscillation of power systems need to be analyzed. This paper thus proposed an adaptive control method for chaotic power systems using finite-time stability theory and passivity-based control approach. The adaptive feedback controller is first constructed using the finite-time stability theory and the passive theory to make the chaotic power system equivalent to a closed-loop passive system. We then proved that the passive power system can stabilize the equilibrium points. We also extensively studied fourth-order power system. Results show that the controller based on the finite-time theory and the passivity-based control approach can effectively stabilize the chaotic behavior within finite time. The control strategy was also found to be robust to the different power system states.

Abstract: This paper is devoted to the study of two kinds of coupled neural networks with different dimensions for input and output vectors, that is, the case with and without time-varying delay. On one side...

Abstract: This paper investigates an energy conservation and dissipation – passivity – aspect of dynamic models in evolutionary game theory. We define a notion of passivity using the state-space representation of the models. Our main contributions include devising systematic methods to examine passivity and identifying properties of passive dynamic models. We explain how our main results can be used to establish a connection between passivity and stability of equilibrium in population games and provide numerical simulations to illustrate stability in population games.

Abstract: The notion of positive realness for linear time-invariant (LTI) dynamical systems, equivalent to passivity, is one of the oldest in system and control theory. In this paper, we consider the problem...

Abstract: In this paper, an improved active stabilization strategy of the interface converters in microgrid applications is proposed on the basis of the passivity-based stability criterion (PBSC). As a critical part of AC and DC hybrid microgrids, the DC microgrid is taken as an example. In particular, a stabilization method with a proportional-integral (PI) controller and firstorder high-pass filter (HPF) is proposed to meet the passivity requirements of the overall control diagram with respect to the output voltage. Meanwhile, an output current feedback control loop is introduced to ensure the output impedance passivity. Moreover, a small-signal model of the parallel interface converter system is established to comprehensively study the influence of control parameters on the passivity of the converters. Based on the active stabilization method proposed in this study, by manipulating the control diagram of each interface converter, the passivity and stability of the DC microgrids with variable configuration can be guaranteed. Therefore, a generic and simplified design approach is realized. A simulation model with three interface converters is implemented in MATLAB/Simulink, and the effectiveness of the proposed passivity-based active stabilization algorithm is verified by using this simulation model.

Abstract: In this study, finite-time passivity of switched non-linear systems is developed. First, a finite-time passivity concept is proposed using multiple storage functions. Second, a switching law is designed to make a switched non-linear system finite-time passive. Third, on the basis of the proposed concept, finite-time passivity properties are investigated. On the one hand, finite-time passivity can induce finite-time stability. On the other hand, finite-time passivity is preserved under the feedback interconnection and parallel interconnection. Furthermore, the merging switching signal technique is employed to make an interconnected system finite-time passive. Finally, an example is provided to demonstrate the effectiveness of the obtained results.

Abstract: This paper considers the passivity performance analysis of fixed-point state-space digital filters with saturation nonlinearities in the presence of external interference. The purpose is to establish new stability criteria in terms of linear matrix inequality (LMI) such that fixed-point state-space digital filters with saturation nonlinearities in the existence of external interference ensure passivity performance with its storage function. The presented results not only ensure state strict and input state strict passivity in the presence of external interference but also confirm asymptotic stability without external interference. The obtained conditions for fixed-point state-space digital filters are based on passivity properties and, hence, are quite novel to previously proposed criteria. Finally, simulation results are given to demonstrate the effectiveness of the proposed work.

Abstract: In this paper, we consider the problem of mixed H∞ and passivity control for a class of stochastic nonlinear systems with aperiodic sampling. The system states are unavailable and the measurement is corrupted by noise. We introduce an impulsive observer-based controller, which makes the closed-loop system a stochastic hybrid system that consists of a stochastic nonlinear system and a stochastic impulsive differential system. A time-varying Lyapunov function approach is presented to determine the asymptotic stability of the corresponding closed-loop system in mean-square sense, and simultaneously guarantee a prescribed mixed H∞ and passivity performance. Further, by using matrix transformation techniques, we show that the desired controller parameters can be obtained by solving a convex optimization problem involving linear matrix inequalities (LMIs). Finally, the effectiveness and applicability of the proposed method in practical systems are demonstrated by the simulation studies of a Chua’s circuit and a single-link flexible joint robot.

Abstract: In order to achieve the maximum power point tracking of photovoltaic (PV) systems in the presence of time-varying stochastic operation conditions and various uncertainties/disturbances, a passivity-based fractional-order sliding-mode control (PbFoSMC) scheme is proposed. The design can be classified into two steps, i.e., (a) construct a storage function in terms of the tracking error of DC-link voltage, DC-link current, and q-axis current for the PV system, upon which the actual characteristics of each term is thoroughly analyzed. Moreover, the beneficial terms are carefully retained to enhance the dynamical responses of the closed-loop system while the detrimental terms are fully removed to realize a global control consistency; (b) based on the passivized system, a fractional-order sliding-mode control (FoSMC) is incorporated as an additional input, which can considerably improve the control performance with the aim of rapid uncertainties/disturbances rejection. Four case studies, including the solar irradiance change, temperature variation, power grid voltage drop, and PV inverter parameter uncertainties, are undertaken to evaluate the effectiveness of PbFoSMC in comparison to that of proportional-integral-derivative control, passivity-based control, and sliding-mode control (SMC), respectively. At last, a dSpace based hardware-in-loop test is carried out to validate the implementation feasibility of PbFoSMC.

Abstract: This paper presents a passive compliance control for aerial manipulators to achieve stable environmental interactions. The main challenge is the absence of actuation along body-planar directions of the aerial vehicle which might be required during the interaction to preserve passivity. The controller proposed in this paper guarantees passivity of the manipulator through a proper choice of end-effector coordinates, and that of vehicle fuselage is guaranteed by exploiting time domain passivity technique. Simulation studies validate the proposed approach.