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Large offshore wind farms (OWFs) connected to a modular multilevel converter (MMC) based highvoltage direct current (HVDC) transmission system may experience electrical resonance in a wide frequency range. The frequency-domain passivity theory offers an effective method for the stability assessment. This paper performs a systematic passivity-based stability analysis of an OWF connected to a MMC-HVDC, where the controller parametric effect on system passivity is thoroughly investigated, and guidelines for minimizing the non-passive region of OWFs and MMC-HVDC by optimizing controller parameters is provided. It is found out that much better stability robustness of the system can be achieved if the central frequency of the notch filter used in the OWF control is tuned lower than the network resonance frequency. Time-domain simulations are given to verify the theoretical analysis. [ABSTRACT FROM AUTHOR]

We consider splitting methods for the numerical solution of differential equations with controls, arising from a marine vessel rigid body model. This model is used in simulations of offshore pipe-lay operations. The system of ordinary differential equations comprises a Coriolis centripetal term, a damping term, a term for environmental forces, a term for restoring forces and moments, and a control term. We propose a splitting into the conservative part, which is nonlinear, but completely integrable (i.e. solutions of the system can be obtained by quadrature), and the damping and control parts, which are linear and can be integrated exactly. The passivity of this system is also considered. [ABSTRACT FROM AUTHOR]

Although various adaptive control techniques have been around for a long time and in spite of successful proofs of stability and even successful demonstrations of performance, the eventual use of adaptive control methodologies in practical real world systems has met a rather strong resistance from practitioners and has remained limited. Apparently, it is difficult to guarantee or even understand the conditions that can guarantee stable operations of adaptive control systems under realistic operational environments. Besides, it is difficult to measure the robustness of adaptive control system stability and allow it to be compared with the common and widely used measure of phase margin and gain margin that is utilized by present, mainly LTI, controllers. Furthermore, customary stability analysis methods seem to imply that the mere stability of adaptive systems may be adversely affected by any tiny deviation from the pretty idealistic and assumably required stability conditions. This paper first revisits the fundamental qualities of customary direct adaptive control methodologies, in particular the classical Model Reference Adaptive Control, and shows that some of their basic drawbacks have been addressed and eliminated within the so-called Simple Adaptive Control methodology. Moreover, recent developments in the stability analysis methods of nonlinear systems show that prior conditions that were customarily assumed to be needed for stability are only apparent and can be eliminated. As a result, sufficient conditions that guarantee stability are clearly stated and lead to similarly clear proofs of stability. As many real-world applications show, once robust stability of the adaptive systems can be guaranteed, the added value of using Add-On Adaptive Control along with classical Control design techniques is pushing the desired performance beyond any previous limits. [ABSTRACT FROM AUTHOR]

For wind farm connection VSC-HVDC transmission has obvious technical and economic advantages, but concentrated integration of large scale wind power requires stronger robustness. Based on the mathematical model of VSC-HVDC in abc frame, the Euler-Lagrange mathematical model of voltage-source-converter(VSC) in d-q rotating frame is built and the strict passivity of VSC is proved. Based on the energy dissipativity of VSC, energy storage function is established by using state error and it is used as Lyapunov function, VSC-HVDC is astringed to expected stable equilibrium point rapidly by damping addition. The passivity controller is designed according to expected equilibrium point, state variable and state error, and decoupling control for various variable is achieved. With different operation conditions, VSC-HVDC and its control system are simulated by software PSCAD/EMTDC the results show that the proposed control strategy has good performance and strong robustness either in dynamic state or steady state. [ABSTRACT FROM PUBLISHER]

This paper proposes a control law for Planar Vertical Take Off and Landing (PVTOL) system based on feedback passivation method. The PVTOL system is a benchmark control system problem which embodies in itself many control theoretic challenges due to its nonlinear and underactuaed dynamics. Trajectory tracking of PVTOL system with its roll angle control is investigated in the paper. Stability of the PVTOL roll angle is ensured by the property that the equilibrium point of a passive system always remains stable. The equivalence of PVTOL dynamics with the pendulum dynamics is exploited to design a simple passivity based feedback controller. The proposed framework interprets PVTOL dynamics as pendulum dynamics and integrator systems whose interconnection can be made passive under the action of the designed control law. The forces exerted by the actuators can be synthesized from the control law. [ABSTRACT FROM PUBLISHER]

This paper describes a remote control system for a crawler-type mobile robot with a passive sub-crawler. Such a system is greatly advantageous because it has an essentially compliant mechanism in that the sub-crawler angle can be adapted to a road surface shape. Its operation is extremely simple, and it is only necessary to control the movement direction and driving speed in comparison with the case of controlling active sub-crawlers. However, a robot with a passive sub-crawler cannot recover from a situation in which it is stuck. The operator must select a traversable route for unknown rough terrain using only the information obtained from camera images and some sensor data from the robot. In this study, a remote control system for a crawler robot with a passive sub-crawler is developed based on a warning system. The currently selected route is evaluated by calculating the stabilization for the robot when falling down in the roll and pitch directions. Experimental results obtained using a prototype crawler robot with a passive sub-crawler demonstrated the effectiveness of the proposed system. [ABSTRACT FROM PUBLISHER]

This paper introduces a fault tolerant control approach based on direct compensation of the power, which is generated by a fault source located at the input of the controlled system. The power of the fault is estimated from the energy balance of the controlled system. The control law, proposed for fault accommodation, depends directly on the estimated fault power and it is formulated such to avoid large, unimplementable control signals that could appear in some specific operating conditions of the system. The method is directly applicable to guarantee the stability of bilateral control systems in the presence of communication delay between the master and the slave. The resulting control algorithm is an extended Passivity Observer - Passivity Controller scheme, which guarantees that the magnitudes of the control signals always remain in an admissible domain. Simulations and realtime experimental measurements are presented to show the efficiency of the proposed control scheme. [ABSTRACT FROM PUBLISHER]

This paper presents a comparison of the modelorder reduction and fast convolution techniques for the macromodel simulation. Model-order reduction techniques using the vector fitting method have been extensively employed. In parallel, convolution techniques using scattering parameters have demonstrated special properties that can be exploited by acceleration techniques to achieve superior performance. The comparison is performed using simulations for various blackbox data. [ABSTRACT FROM PUBLISHER]

The design of a passivity-based non-linear controller for a shunt active filter to be used for the compensation of the harmonic components consumed by non linear loads is presented in this paper. The main objective of this control strategy is to inject the necessary compensation current into the system so that the grid current is sinusoidal and balanced, regardless of whether the grid voltage is unbalanced and/or distorted. The reference values for the compensation currents are obtained from applying the Instantaneous Active-Reactive Power Theory. The system is represented by its port-controlled Hamiltonian model and the controller designed on the basis of interconnection and damping assignment using a method based on Lyapunov techniques. The behavior of the proposed control strategy is validated through simulation using a realistic model. [ABSTRACT FROM PUBLISHER]

The proposed observer could estimate AUV's low frequency motion and environmental disturbance force from the synthetical signals which include the low frequency motion signals, high frequency motion signals and measure noise from the sensors. The nonlinear observer is proved global exponential stability and passive. Passivity theory is used in designing the tuning parameters of the observer. The observer overcomes the essential shortcomings of the tradition Kalman filter which applies the linear theory and gain scheduling techniques. A set of computer simulations which is carried out to test the performance of the proposed observer proves the excellent capability. [ABSTRACT FROM PUBLISHER]

In this paper we derive sufficient conditions for passivity of singular neutral time delay systems (TDS) involving norm bounded parametric uncertainties. The states and state derivatives involve time varying delays. Delay dependent sufficient conditions are formulated in terms of Linear Matrix Inequalities (LMIs). The problems of regularization and removal of impulsive solutions have been addressed. Applications of proposed approach have been presented in the form of numerical examples at the end. [ABSTRACT FROM PUBLISHER]

This paper deals with the analysis of a closed-loop identification technique applied to a DC servomechanism from a passivity point of view. It is shown that the closed-loop system together with the identification algorithm can be divided into simpler subsystems easier to analyze and then, many properties related to passivity and stability can be deduced. Furthermore, it is shown that with this separation approach we have the freedom to select many controller structures, which could let to improve the performance of the identification algorithm, even in presence of perturbation signals. [ABSTRACT FROM PUBLISHER]

Recently, study on a control of flexible manipulators have been receiving increasing attension in the domain of master-slave system. The master-slave system is a control system to operate a manipulator for objects in a remote environment which is at a distance from the presence of a human operator. In order to consider the influence by the elasticity of flexible manipulators, it is necessary to study on the control of vibration of flexible master-slave manipulators and the passivity. Thus in this paper, we discuss about a new modified bilateral controller considering the elasticity by using intervention impedance in basis on the passivity and a control performance of the system. This paper is organized in the following way : First, we introduce mechanical models of manipulators. Second, we propose bilateral controls by using intervention impedance based on passivity. Third, we transeform each models represented by time domain into models represented by s-plain, find the scattering matrix, and prove the passivity of system. Fourth, we propose a new modified controller controller for the purpose of realizaion. Lastly, we show some results of experiments in order to verify the usefulness of proposed controller. [ABSTRACT FROM PUBLISHER]

In this paper, we propose the Sliding Mode Control (SMC) for a class of uncertain singular Neutral Time Delay Systems (NTDS) with time varying delays. An integral type sliding manifold is selected by considering the singular matrix. Delay dependent sufficient conditions are derived in terms of Linear Matrix Inequalities (LMIs) for robust passivity of sliding mode dynamics. The system is assumed to have unmatched norm bounded uncertainties in system parameters and matched bounded external disturbances and uncertainties due to unmodeled dynamics. The regularization and removal of impulsive solutions have been considered. The problem of feedback passification of unstable systems is solved and robust controller with memory is synthesized that ensures the passivity of sliding mode dynamics. An SMC law is established that guarantees the reach ability of states to sliding surface in a finite time. The derived results are validated by a numerical example at the end. [ABSTRACT FROM PUBLISHER]

This paper focuses on robust passification for singular neutral systems with time varying delays and estimation of their domain of attraction considering bounded control effort (actuator saturation). The delays in states and state derivatives have upper and lower bounds. The system is assumed to have polytopic parametric uncertainties. Memory less state feedback controller for robust passification is synthesized. The delay range dependent sufficient conditions for robust passivity of closed loop system are derived in terms of Linear Matrix Inequalities (LMIs). The domain of attraction is estimated by solving an optimization problem in terms of LMIs to obtain less conservative results. Numerical example is presented at the end that shows the effectiveness of the proposed theoretical results. [ABSTRACT FROM PUBLISHER]

By using the Lyapunov-Krasovskii functional approach, the robust passive control problem for uncertain linear singular time-delay systems is investigated. Sufficient conditions are firstly given to ensure that linear singular systems are admissible (that is, regular, stable, impulse-free) and passive. Secondly, based on the linear matrix inequality method and cone complementarity linearization (CCL) technique, the robustly state-feedback controller is designed to guarantee that the resultant closed-loop singular systems are admissible and robustly passive with dissipation. Finally, two illustrative examples and their simulations are presented to show the effectiveness of the obtained results. [ABSTRACT FROM PUBLISHER]

Traditional definitions of dissipativity require an assumption that the admissible control should guarantee that the system has a unique solution and the supply rate is locally integrable. In this paper, by introducing the first exit time from a changeable domain of state and input, a novel dissipativity in the local form and the global sense is defined based on some easily-checked conditions. By the aid of the new definition, a criterion on existence of solution (which will be used before stability analysis) is proposed. All our efforts are to construct a new framework of dissipative-system theory which includes some standard results in traditional dissipative theory and Lyapunov methods as special cases. Therefore, the theoretic analysis is more rigorous and the range of applications is greatly broadened. [ABSTRACT FROM PUBLISHER]

This paper considers the passivity-preserving model reduction problem for positive real descriptor systems. The model reduction principle is presented first, then a sufficient and necessary conditions is provided to check whether the high-order descriptor systems can be reduced with preservation of passivity. A model reduction algorithm is provided. Moreover, the presented method provides an H∞ norm bound on the approximation error. [ABSTRACT FROM PUBLISHER]

This paper deals with output synchronization of linear interconnected system with general interconnection. The main result is that output synchronization of the interconnected system can be achieved through the consensus algorithm if passivity of the system is satisfied. Furthermore, the analysis is released in decentralized way, and we design observer-based state feedback controller. The following controller and observer gains can be calculated from LMI conditions in the decentralized scheme. Two simulations and conducted to evaluate the validity of the synchronization analysis and effectiveness of design of the control law. [ABSTRACT FROM PUBLISHER]

The object of this work is to highlight, on a physical coupled tanks system, the performances of a digital design of a continuous-time passivity based controller. The design considers the sampled-data model of the plant and provides better results compared to the emulations of given continuous-time controllers. A two-state continuous-time non-linear model is used to design the digital controller. A feedback passivating controller is developed in continuous-time from a suitable choice of the storage function V. The results show good performances of the controller when increasing the sampling period or the controllers gain. [ABSTRACT FROM PUBLISHER]

In this paper, we present a multi-fingered robot hand model with 20 Degrees of Freedom (DoF). We have developed a humaniform robot hand which containts 14 servomotors, equipped with several sensors and a wireless communication set. Based on the proposed design of the multi-fingered robot hand, efficient global model equations have been generated by the Lagrange formulation. Furthermore the dynamic model emphasize the coupling dynamic characteristics. The system is split to seven sub-blocs which can be separately simulated. The passivity approach is proposed and properties are illustrated by simulation results. Several simulation results show that the derived dynamic model can predict the motion of the multi-fingered hand in free motion or in constrained behavior. [ABSTRACT FROM PUBLISHER]

The passivity conditions for delayed neural networks (DNNs?) are considered in this paper. The interval of the time delay is divided into two subintervals by introducing an arbitrary interior point. By choosing an augmented Lyapunov-Krasovskii functional and checking its variation in the two subintervals, respectively, two novel conditions are obtained in terms of linear matrix inequalities (LMIs), which can be easily checked by Matlab LMI Toolbox. Finally, two numerical examples are given that our results are less conservative than some existing ones. [ABSTRACT FROM PUBLISHER]

Rate Mode is utilized in many telemanipulation applications where the master workspace is limited compare with the slave workspace. Beside transparent, stability is the main issue of teleoperation systems and time delay communication is the main factor lead to the instability of the system. Many methods have been proposed in order to stabilize the rate mode teleoperation system working under varying time delay and data - cropped telecommunication environments. In this paper, Time Domain Passivity Approached and recently proposed energy based framework are implemented to stabilize the teleoperation system under variable time delay communication. Experiments have also been done and showed that the proposed method helps operators to control the speed of slave robot much easier and smoother without any unstable behaviour. [ABSTRACT FROM PUBLISHER]

Signal speeds of high speed serial links double almost every generation and with these increasing speeds come a wide range of new modeling and simulation challenges. Modeling challenges involve making sure that models are passive, stable and causal. Frequency-domain models, such as scattering parameter models that have measurement noise or limited bandwidth or incorrectly performed interpolation or extrapolation operations, may exhibit non-causality and non-passivity in time domain. Simulating millions of bits in timedomain to measure the interface merit in terms of bit error rate (BER) is CPU and memory intensive. This challenge has given way to new simulation algorithms and methodologies. The challenge here is that no two simulation approaches result in the same answer. The difference between approaches is aggravated at high frequencies and with inclusion of effects like crosstalk and transmitter and receiver equalization. In this paper, the results from various simulation approaches are contrasted against each other and also against measurements to understand their inherent assumptions along with their impact in designing high speed SerDes. [ABSTRACT FROM PUBLISHER]

In this paper, we investigate the realization problem of a special class of positive-real admittances in a form similar to biquadratic functions but with an extra pole at s = 0, which is common in vehicle suspension designs. The number of inerters and dampers is restricted to one in each case and number of the springs is arbitrary. To solve the problem, we first convert a previous result by Chen & Smith, 2009 to a more direct form. A necessary and sufficient condition for realizability is then derived and explicit circuit arrangements are provided to cover the realizability conditions. [ABSTRACT FROM PUBLISHER]

The role of internal model principle is investigated in this paper in the context of collective synchronization and formation control problems. In the collective synchronization problem for nonlinear systems, we propose distributed control laws for passive systems which synchronize to the solution of an incrementally passive exosystem. This generalizes the result from linear systems where the existence of an internal model is required for the output synchronization of networked systems. In our second result, a distributed control law that solves a formation control problem for incrementally passive systems is proposed based also on the internal model principle. [ABSTRACT FROM PUBLISHER]

In this paper we derive sufficient conditions for passivity of neutral type time delay systems (TDS) with time varying parametric uncertainties. The delays in states and state derivatives are assumed to be time varying. Delay dependent sufficient conditions for robust passivity, are derived in terms of Linear Matrix Inequalities (LMIs). Feedback control law is formulated for robust passification of unstable systems. Numerical examples are given at that end that show the effectiveness of the proposed approach and reduced conservatism as compared to previously used passivity analysis and passification techniques. [ABSTRACT FROM PUBLISHER]

This paper presents an approach to address conflicting motion tasks in multi-objective control of virtual humans. The novelty in our approach is that we can handle the inequality constraints and maintain the passivity as well. The targets associated with lower priority tasks are constrained so as to guarantee that the higher priority tasks can be sufficiently fulfilled. The multi-objective controller takes as inputs the desired task targets and computes the optimal task wrenches by solving an optimization problem. Finally, the joint torques are computed according to the optimal task wrenches. This control approach can be realized in real-time. Simulations demonstrate that the proposed method can improve the behavior of a virtual human. [ABSTRACT FROM PUBLISHER]

Flexible structure dynamics with collocated force actuators and position sensors lead to negative imaginary (NI) systems. However, in some cases, the models obtained for these systems may not satisfy the NI property. This paper provides a new method for enforcing such models to be NI. The results are based on a study of the spectral properties of related Hamiltonian matrices. A test for the negativity of the imaginary part of a corresponding transfer function matrix is first performed by checking for the existence of imaginary eigenvalues of the associated Hamiltonian matrix. In the presence of imaginary eigenvalues, the system is not NI. In such cases, a first-order perturbation is presented for the precise characterization of frequency bands where violations of the NI property occur. This characterization is then used for the design of an iterative perturbation scheme for state matrices aimed at displacing the imaginary eigenvalues of the Hamiltonian matrix away from the imaginary axis. [ABSTRACT FROM PUBLISHER]

There is abundant evidence that African American children, despite civil rights legislation of the 1960s, are segregated from their white counterparts in three systems whose mission is to serve children: special education, child welfare, and juvenile justice. Studies of the overrepresentation of black children in each of these systems show that racial bias accounts for some measure of the problem (Harry et al. 2002; Johnson et al. 2007; Markowitz 2000). The theory of silent racism—the negative images and assumptions that white Americans, generally, hold about black Americans—sheds light on the racial bias associated with disproportionality in all of the service areas mentioned above. I argue that service providers are likely to be unaware that their decisions hurt the very children they are dedicated to helping. Part of the problem lies in the belief that people are either racist or not racist, a view that encourages defensiveness, not openness, when considering one's own racial bias. Changing this categorical way of thinking about racism, plus increasing race awareness among the white professionals who provide needed services to our country's children, are necessary conditions of lessening the racial disproportionality that affects those children today. [ABSTRACT FROM AUTHOR]

Time-domain passivity approach (TDPA) is a way of stable haptic interaction and robot control, such that at any given time the passivity of the system is guaranteed. It is formulated in time-domain, which facilitates its integration in control loop. In this paper we discuss application of this approach to the teleoperation system, model of which assumes admittance mode - with input of effort (force) and output of flow (velocity). [ABSTRACT FROM PUBLISHER]