Passivity analysis of impulsive complex networks

In this paper, we first investigate input passivity and output passivity for a class of impulsive complex networks with time-varying delays. By constructing suitable Lyapunov functionals, some input passivity and output passivity conditions are derived for the impulsive complex networks. Finally, an example is given to show the effectiveness of the proposed criteria.     

Improved passivity criterion in haptic rendering: influence of Coulomb and viscous friction

In this paper, a new criterion for passivity of haptic devices is obtained. This criterion creates a relationship between Coulomb friction coefficient, viscous friction coefficient, sampling rate, and the maximum simulated stiffness. The process of derivation of the passivity criterion is described in detail. This criterion is improved compared with other existing criteria and predicts passivity in haptic rendering more accurately. In particular, for speeds of less than 5?cm/s, the new passivity criterion should replace the previous criteria to avoid unwanted vibrations of stiff virtual walls. Analytical and numerical investigations are presented to validate the new criterion. A specific trajectory is designed and the movement of the haptic robot is investigated on this trajectory to validate and compare this passivity criterion with the previous criteria.     

Passivity-based decentralized stabilization of multi-agent systems with uncertainty and mixed delays

In this paper, we investigate a decentralized stabilization problem of uncertain multi-agent systems with mixed delays including discrete and distributed time-varying delays based on passivity stability. We design a decentralized state-feedback stabilization scheme such that the family of closed-loop feedback subsystems enjoys the delay-dependent passivity stability for each subsystem. Then, by employing a new Lyapunov-Krasovskii function, a linear matrix inequality （LMI） approach is developed to establish the delay-dependent criteria for the passivity stability of multi-agent systems. The sufficient condition is given for checking the passivity stability. The proposed LMI result is computationally efficient. An example is given to show the effectiveness of the method.     

Sampled- and continuous-time passivity and stability of virtual environments

We propose a new time-domain passivity observer (PO) and passivity controller (PC) which removes the constant-velocity assumption during one sample time, which was used in our previous PO/PC approach. A new sampled-time definition of passivity is introduced, and this new definition is compared with the previous sampled-time definition of passivity. Through this comparison, we propose the more accurate PO/PC approach. The proposed new PO/PC approach is applied to the "Excalibur" haptic interface system with very high stiffness (K = 120 kN/spl middot/m) virtual environment, and stable contact is demonstrated.     

Incremental passivity and output tracking of switched nonlinear systems

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.     

Wave-based passive control for transparent micro-teleoperation system

A wave-based bilateral controller for a micro-teleoperation system is presented for stability and transparency via a passivity approach. We showed that the application of wave variable formalism allows the passivity of the system in spite of external perturbations and environment uncertainties. While most of the existing wave-based approach assumes LTI and fixed time-delay, this paper extends the research domain to a scaled teleoperation system with variable time-delay, asymmetric gains in force and velocity variables or model uncertainties in the microenvironment. Based on the wave-based analysis of a time-varying system, a variable gain controller is proposed in order to guarantee the passivity of the system. Furthermore, in scaled teleoperation there exist positive gain matrices (scaling position and force factors) that preserve its passivity only if gain matrices are equal, which is hard to find in a real system. In case the equality condition is not satisfied, we introduced filter functions with a set of conditions for two operating cases: a structurally dominated system and a surface-dominated system. Finally, as the nonlinear nature of small scale environments with unknown dynamic passivity condition can not be satisfied, we analyzed the constraints inevitably occurring in a micro-teleoperation system and derived conditions between the parameters. The stability is analyzed based on the passivity of the resultant operator–telemanipulator–environment system. The experimental results show clearly that the proposed passivity conditions ensure stability and transparency performances against variable time-delays and scaling factors.     

时变时滞不确定性神经网络的被动性准则

研究具有时变时滞不确定性神经网络的被动性问题。通过构造适当的Lyapunov泛函并利用一些分析技巧,给出一个新的条件,以确保与时变延迟的不确定性神经网络的被动性。被动条件以线性矩阵不等式(LMI)表示,可以很容易地通过有效内点算法进行求解。通过一个数例证明了该方法的有效性。     

Passivity and robust synchronisation of switched interval coupled neural networks with time delay

This paper is concerned with passivity and robust synchronisation of switched coupled neural networks with uncertain parameters. First, the mathematical model of switched coupled neural networks with interval uncertain parameters is established, which consists of L modes and switches from one mode to another according to the switching rule. Second, by employing passivity theory and linear matrix inequality techniques, delay-independent and delay-dependent conditions are derived to guarantee the passivity of switched interval coupled neural networks. Moreover, based on the proposed passivity results, global synchronisation criteria can be obtained for switched coupled neural networks with or without uncertain parameters. Finally, an illustrative example is provided to demonstrate the effectiveness of the obtained results.     

Passivity and global stabilization of cascaded nonlinear systems

An alternative stability analysis is presented for recent results on global stabilization of a nonlinear system in cascade with a linear system. The analysis is carried out using passivity arguments. The relationship between passivity and an important class of Lyapunov function is also presented     

Passivity and feedback passification of switched discrete-time linear systems

This paper focuses on the passivity analysis and feedback passification for switched discrete-time linear systems using multiple storage functions under a certain switching law. Controllers and switching laws are designed based on complete and partial state measurements, respectively. Conditions for strict passivity of a switched discrete-time system are obtained without the requirement of strict passivity of subsystems. In the case of partial state measurements, dynamic output feedback controllers for subsystems are designed, and a switching law depending only on the state of the output feedback controllers is constructed to guarantee strict passivity of the closed-loop switched system. Finally, a numerical example is provided to demonstrate the feasibility of the theoretical results.     

Novel passivity criteria for neural networks with discrete and unbounded distributed time-varying delays

Novel passivity criteria are presented for the passivity of a class of cellular neural networks with discrete and unbounded distributed time-varying delays. Two types of uncertainty are considered: one is time-varying structured uncertainty while the other is interval uncertainty. The Gu's discretized Lyapunov–Krasovskii functional method is integrated with the technique of introducing the free-weighting matrix between the terms of the Leibniz–Newton formula. The integrated method leads to the establishment of new delay-dependent sufficient conditions in form of linear matrix inequalities for passivity of delayed neural networks. A numerical simulation study is conducted to demonstrate the obtained theoretical results, which shows their less conservatism than the existing passivity criteria.     

遥操作系统力觉接口的无源性设计

力觉接口是指人和遥操作机械手之间的接口,用来给操作人员提供操作时的一种虚拟环境．无源性是这种接口系统设计的主要要求,但是前人得出的无源性条件过于保守．本文从采样控制系统的频率特性出发推导了一个没有保守性的接口系统无源性的条件．文中并指出无源性只是接口的一个属性,要正确设计还需考虑到伺服设计的一些基本要求,诸如系统的带宽、阻尼等．文中还结合例子给出了接口系统无源性设计的步骤．     

Feedback passivation of switched nonlinear systems using storage-like functions

This paper addresses the issues of passivity and feedback passivation of switched nonlinear systems via multiple storage functions. The concept of storage-like functions for switched systems is presented. A sufficient condition for passivity of switched nonlinear systems is given via multiple storage functions under some switching signal. Then, the result is extended to find conditions under which a switched system is feedback equivalent to a passive switched system. Furthermore, passivity of switched cascade systems is investigated.     

交直流混合输电系统的新型无源性调制

交直流混合输电系统的动态响应性能直接影响电力系统的稳定性.为提高系统的动态响应速度和控制器的鲁棒性,本文基于无源性理论从具体结构出发,设计了直流输电系统的无源性调制控制器.以交直流并联的两机系统为研究对象,对系统的输入输出进行重构,并对系统的无源性进行验证.根据稳定性和无源性之间的关系,设计出反馈控制规律.对两种不同情况的仿真,显示出该控制律在保证系统的稳定性的同时.提高了系统的动态响应速度.     

Passivity‐based sliding mode controller/observer for second‐order nonlinear systems

A passivity‐based sliding mode control for a class of second‐order nonlinear systems with matched disturbances is proposed in this paper. Firstly, a nonlinear sliding surface is designed using feedback passification, in which the passivity is employed to guarantee the closed‐loop system's stability. The passivity‐based controller comprising a discontinuous term guarantees globally asymptotical convergence to the sliding surface. A sliding mode‐based control law that satisfies the reaching and sliding condition is also developed. Moreover, the passivity‐based sliding mode observer is also developed to effectively estimate the system states. Compared with conventional sliding mode control, the proposed control scheme has a shorter reaching time; and hence, the system performance is less affected by disturbances, thus eliminating the need to increase the control input gain. Finally, simulation results demonstrate the validity of the proposed method.     

A passivity approach to game-theoretic CDMA power control

This paper follows a game-theoretical formulation of the CDMA power control problem and develops new decentralized control algorithms that globally stabilize the desired Nash equilibrium. The novel approach is to exploit the passivity properties of the feedback loop comprising the mobiles and the base station. We first reveal an inherent passivity property in an existing gradient-type algorithm, and prove stability from the Passivity Theorem. We then exploit this passivity property to develop two new designs. In the first design, we extend the base station algorithm with Zames-Falb multipliers which preserve its passivity properties. In the second design, we broaden the mobile power update laws with more general, dynamic, passive controllers. These new designs may be exploited to enhance robustness and performance, as illustrated with a realistic simulation study. We then proceed to show robustness of these algorithms against time-varying channel gains.     

Passivity and Pinning Passivity of Coupled Delayed Reaction–Diffusion Neural Networks with Dirichlet Boundary Conditions

This paper respectively considers passivity problem and pinning passivity problem for coupled delayed reaction–diffusion neural networks (CDRDNNs). By construction of appropriate Lyapunov functionals and utilization of inequality techniques, several passivity conditions are derived for the CDRDNNs. Moreover, the pinning control technique is developed to obtain some passivity criteria for CDRDNNs. Finally, two numerical examples are also provided to verify the correctness of the theoretical results.     

Passivity analysis and control for discrete-time two-dimensional switched systems in Roesser model

This paper investigates the passivity issues of discrete-time two-dimensional switched systems in Roesser model under a state-dependent switching law. Conditions for passivity of discrete-time two-dimensional switched systems are obtained without the requirement of passivity of subsystems. When the system states are completely available, state feedback controllers and switching laws are designed. In the case of partial state measurements, dynamic output feedback controllers and switching laws depending only on the state of the output feedback controllers are constructed to guarantee passivity of the closed-loop switched system. Finally, numerical examples are provided to illustrate the efficiency of the results.     

非线性机电换能器混沌系统的无源化控制

针对一类相对阶为2的非线性机电换能器混沌系统,研究其无源化控制问题．所分析的系统具有标准链式结构,利用逆步（Backstepping）方法及无源性与稳定性之间的等价关系,设计并证明了系统的反馈镇定控制器．仿真算例验证了所提出方法的有效性．     

Equilibrium-independent passivity: A new definition and numerical certification

We extend the traditional notion of passivity to a forced system whose equilibrium is dependent on the control input by defining equilibrium-independent passivity, a system property characterized by a dissipation inequality centered at an arbitrary equilibrium point. We provide a necessary input/output condition which can be tested for systems of arbitrary dimension and sufficient conditions to certify this property for scalar systems. An example from network stability analysis is presented which demonstrates the utility of this new definition. We then proceed to numerical certification of equilibrium-independent passivity using sum-of-squares programming. Finally, through numerical examples we show that equilibrium-independent passivity is less restrictive than incremental passivity.