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This article aims to solve the problem of decentralized event-based finite-time control for a class of high-order interconnected nonlinear systems with an asymmetric output constraint. In order to achieve finite-time stability and reduce the update frequency of the controller, a novel controller and its event-trigger mechanism is proposed by adding a power integral technique and utilizing sign function. To fulfill the requirement of asymmetric output constraints, an asymmetric barrier Lyapunov function (BLF) is constructed, which is different from tan-type and log-type BLFs. Based on the contradictory idea and finite-time stability theory, it is proved that there is no Zeno phenomenon under this event-trigger mechanism and all state variables of the closed-loop system attenuate to the origin in the finite-time while the output signals never violate the constraint. Furthermore, the result in this article is expanded to fixed-time control. Finally, a simulation example is given to demonstrate the effectiveness of the presented strategy. [ABSTRACT FROM AUTHOR]

This article addresses the distributed asynchronous consensus problem for nonlinear multiagent systems with switching topologies. Different from the existing results, we consider the detection delay of topology modes and some topologies having no directed spanning tree with leader as the root. In these conditions, the distributed asynchronous switched observer is first developed for each follower to accurately estimate the state information of the leader. Then, an output feedback distributed controller is designed for each follower by means of the switched observer. According to the Lyapunov stability theory, it is proved strictly that the controller can guarantee all agents achieving a consensus if the topologies are switched by the switching signal fulfilling a general rule. Moreover, the switching rule compared with the one satisfying average dwell-time condition can render the number of topology switches growing faster on any time interval. Finally, the numerical simulation is presented to verify the effectiveness of proposed theoretical results. [ABSTRACT FROM AUTHOR]

This article addresses the leader-following consensus problem for multiagent systems with unknown output measurement sensitivity based on a fixed directed topology. Different from the existing works on the consensus problem, the output measurement sensitivity is described as a total unknown parameter. Under this nonideal condition, we put forward a distributed output-feedback consensus control algorithm for the first time. To start with, we design the novel distributed high-gain observer and a high-gain K-filter for each follower, which are utilized to reconstruct the state of the leader and the follower, respectively. Subsequently, the consensus problem is transformed into the stability problem by introducing appropriate state transformation. By using the backstepping control method, the distributed output-feedback controller with an adaptive law is designed for each follower with the help of a Nussbaum-type function. Based on the Lyapunov stability theory, it is strictly proved that all agents can achieve a consensus with the designed controller. Finally, the numerical simulation is presented to illustrate the effectiveness of theoretical results. [ABSTRACT FROM AUTHOR]

This article focuses on distributed consensus control for nonlinear multiagent systems under directed graphs of dynamic frequency switches. The agents exchange information with each other through directed graphs that are switched based on a new general switching law. Not all graphs contain a spanning tree with the leader as the root. Under this condition, a novel distributed switched observer is constructed for each follower, and it can accurately estimate the state information of the leader by means of the switching law. Subsequently, a unified distributed controller is designed for each follower with the observer. Based on the Lyapunov stability theory, it is strictly proved that all agents can achieve a consensus with the controller. More importantly, our proposed algorithm can render the number of switches of the graphs to grow faster than an affine function of the length of a time interval, which greatly reduces the conservativeness on graphs switches. Moreover, the consensus algorithm has a wide application prospect in cooperative control. Finally, the effectiveness of theoretical results is illustrated by making numerical simulations. [ABSTRACT FROM AUTHOR]

This technical note focuses on the leader-following output consensus problem for a class of high-order nonlinear multiagent systems under a fixed directed graph. To obtain the global result of output feedback control for the system with the less conservative condition on nonlinear terms than traditional Lipschitz one, the novel reduced-order dynamic compensator is constructed. By introducing an appropriate state transformation, a new fully distributed output feedback control method is proposed, which greatly simplifies the design procedure compared with the backstepping method. The distributed linear-like controller with a dynamic gain is designed for each agent based only on the relative output measurements of neighboring agents. The condition that the orders of all agents should be the same is not needed anymore with the proposed method; thus, the novel result will have extensive applications. Finally, the theoretical results are supported by a numerical simulation. [ABSTRACT FROM AUTHOR]

This paper describes a linearization method to enhance the third-order distortion performance of a subthreshold common-source cascode low-noise amplifier (LNA) without extra power consumption by using passive components. An inductor between the gate of the cascode transistor and the power supply in combination with a digitally programmable capacitor between the gate and the drain of the cascode transistor enable to improve the third-order intermodulation intercept point (IIP3) of a subthreshold LNA. The theoretical mechanisms that underlie the linearity improvement are analyzed comprehensively under the consideration of the LNA’s input stage, cascode stage, reverse isolation, and stability. A 1.8-GHz LNA was designed and fabricated using 0.11- \mu \textm CMOS technology to prove the concept. Measurement results reveal that the linearized low-power LNA has a 14.8-dB voltage gain, a 3.7-dB noise figure, and a −3.7-dBm IIP3 with a power consumption of 0.336 mW. [ABSTRACT FROM AUTHOR]

This paper demonstrates an input impedance boosting method that was developed for long-term monitoring of electroencephalography signals. An instrumentation amplifier was designed with a negative capacitance generation feedback (NCGFB) technique to cancel the adverse effects of input capacitances from electrode cables and printed circuit boards. The NCGFB boosts the measured impedance from below 40 M $\Omega $ to above 500 M $\Omega $ at 50 Hz when the equivalent capacitance at the inputs is up to 150 pF. The prototype chip includes an automatic calibration system to adaptively enhance the input impedance through on-chip test signal generation, measurement, and the automatic digital control of the NCGFB. Consisting of an instrumentation amplifier, a low-pass notch filter, and a variable gain amplifier in 130-nm CMOS technology, the signal path has a combined gain range of 66–93 dB with a total power consumption of 42 $\mu$ W. The front-end bandwidth covers 0.5–48 Hz, and its integrated input-referred noise over the bandwidth is 3.75 $\mu$ Vrms. The measured third-order harmonic distortion component is at least 57 dB below the fundamental signal level. A common-mode rejection ratio of 77.6 dB and a power supply rejection ratio of 74 dB were measured at 10 Hz. When activated, the auxiliary test signal generation and calibration circuits consume a power of 542 $\mu$ W. [ABSTRACT FROM PUBLISHER]

The domain of attraction problem is investigated for networked teleoperation system subject to actuator saturation. The forward and backward time-varying communication delays are assumed to be interval and asymmetric, which is the case for network-based teleoperation system. We propose a novel Lyapunov-Krasovskii functional for the closed-loop teleoperation system with the consideration of the interval values of the time delays. The delay-dependent estimation of the domain of attraction is presented using linear matrix inequality (LMI) technique. The problem of designing \mathrmP+\mathrmd control law such that the domain of attraction is enlarged is formulated and solved as an optimization problem with LMI constraints. Experiments are performed to verify the effectiveness of the proposed approach. [ABSTRACT FROM AUTHOR]

Abstract: The nonlinear effect of a moving-coil loudspeaker, originating from its magnetic coupling factor and the system’s stiffness, presents a significant impact on the sound quality. For improving the sound quality, this article proposes an approach to reduce the total harmonic distortion (THD) by adjusting the initial position of its voice-coil. First, a mathematical model involving the nonlinearities of force factor, mechanical stiffness, and inductance of voice coil is constructed and then solved using a novel algorithm called the parameter spline difference method (PSD). In the course of pursuing reduction of the corresponding THD of a typical moving-coil loudspeaker, the model was used to analyze the nonlinearity of the THD, revealing itself as a nonlinear function of force factor, the system’s stiffness and inductance of voice coil. For various initial positions of the voice-coil, the coupled nonlinear differential equations were solved using the PSD to yield corresponding sound pressure level and THD. To our satisfaction, the loudspeaker driver with its voice-coil optimally tuned for the initial position turns out to have a THD reduction of 10%, which is also consistent with our experimental observations. [Copyright &y& Elsevier]

The model following control problem is addressed for a class of nonlinearly interconnected systems with time delays. The subsystems are with multiple dead-zone actuators and mismatched time-varying disturbances. To deal with the multiple unknown dead-zone inputs, we decompose the system properly based on the input matrix. By using the adaptive method to compensate the unknown parameters, we design a new and simple memoryless controller. The stability of the resultant closed-loop error system is proved by employing a new Lyapunov Krasovskii functional. The designed controller is tolerant to any dead-zone inputs and general time delays. Finally, the simulations are performed and the results show the potential of the proposed method. [ABSTRACT FROM AUTHOR]

Abstract: In this paper, the dual reciprocity boundary element method wave model that is governed by a modified mild-slope equation is developed. Instead of addressing the infinite boundary condition, the model automatically satisfies the Sommerfeld radiation condition. This work examines the effects of both the bottom curvature and the slope-squared terms. The conducted numerical experiments have a topography that is composed of a cylinder mounted on two kinds of basic shoal: types 1 and 2 cubic. In addition, numerical experiments that combine two cubic type islands with ripple-beds are performed. The results show that the curvature term dominates the calculation of the sinusoidal-varying topography; even a disturbance in the topography is insignificant. In contrast to smooth topographies, the bottom curvature and the slope-squared terms are not dominant. Thus, the extended terms can be neglected if the seabed is smooth and gentle. When the topographies are combined with ripple-beds, the difference in the dimensionless wave amplitudes along the sidewall of the types 1 and 2 cubic islands is found to be 2.9 and 3.02, respectively. According to our study of cubic islands that are combined with ripple-beds, we can conclude with certainty that even though the variation of the seabed is very slight, the curvature and the slope-squared terms cannot be neglected for an uneven bottom. [Copyright &y& Elsevier]

Abstract: This paper investigates the robust stability of uncertain neutral system with time-varying delay and nonlinear uncertainties. By using Lyapunov method and linear matrix inequality technology, a new delay-dependent stability criteria is obtained and formulated in terms of linear matrix inequalities (LMIs) which can be easy to check the robust stability of the considered systems. Numerical examples are given to indicate significant improvements over some existing results. [Copyright &y& Elsevier]

Abstract: This paper applies the newly developed panel cointegrated technique [R. Larsson, J. Lyhagen, M. Lothgren, Likelihood-based cointegration tests in heterogeneous panels, Econom. J. 4 (1) (2001) 109–142] that allows for multiple cointegrated relationships to empirically re-examine the long-run money demand function for six selected countries of the Gulf Cooperation Council (GCC) in 1979–2000. At the center of focus is a discussion on the regional money demand phenomena with challenges and potential benefits, because of these GCC member adoption this monetary integration policy. It is determined that there are at least two cointegrated relations in the four-dimensional vector error correction model for the variables of the real money balance, the real scale variable, the nominal interest rate, and the exchange rate. The coefficient restriction test is also conducted, and it substantiates that the full panel test significantly rejects the hypothesis of the quantity theory of money for the long-run elasticity of income equal to unity, and we are able to reject the null hypothesis when the semi-elasticities of the nominal interest rate and exchange rate are equal to zero. Some critical policy implications emerge from the results. [Copyright &y& Elsevier]

This paper focuses on the tracking control problem for a class of nonlinear system with time delays and dead-zone input. The nonsymmetric dead-zone input case is considered without the knowledge of the dead zone parameters. The time delay uncertainties are bounded by a non-linear function with unknown coefficients. By constructing a novel Lyapunov functional, we design a simple and smooth adaptive state feedback controller. It is shown that the solution of the resulting closed-loop error system converges to an adjustable region exponentially. Finally, numerical examples are included to show the effectiveness of the theoretical results. [ABSTRACT FROM AUTHOR]

The robust control problem for a class of uncertain time- delay systems is investigated. The systems include multiple time delays and uncertain nonlinear functions. To our best knowledge, no controller design method for the systems is reported in the literature except for sliding mode control (SMC). However, the sliding mode controller must use the delayed state of the system, so that the precise time delays have to be known, and also a large memory is needed for controller implementation. To overcome the shortcomings, we employ the backstepping method to design a memoryless state feedback controller. By constructing a novel Lyapunov-Krasovskii functional, we show that the resulting closed-loop system is asymptotically stable. Simulations are done to verify the effectiveness of the proposed method. [ABSTRACT FROM AUTHOR]

Abstract: This paper develops a modified Trefftz method (MTM) associated with the group-preserving scheme (GPS) to deal with the two-dimensional non-linear sloshing problem. For non-linear sloshing phenomena, the conventional numerical method may encounter numerical instabilities and numerical dissipation, as the coefficient matrix obtained from the conventional numerical method is ill-posed, and the free surface exhibits non-linear kinematics. To overcome these problems, we introduce the concept of controlled volume into the numerical procedure to prevent the elevation from vanishing, and we take the characteristic length into account to maintain the stability of the new numerical method. Moreover, the use of the GPS eliminates the need to use second-order derivatives, thus increasing the numerical efficiency, and weighting factors can be used to observe the vanishing of the velocity potential. Comparisons of results of the present study with those in the literature show that the numerical results are better than those obtained using previous methods. The method developed here is a simple and stable way to cope with the non-linear sloshing problem. [Copyright &y& Elsevier]

Abstract: The motivation behind this paper is to re-investigate the stability of the long-run money demand function (MDF) in a non-linear cointegrating framework for G-7 countries. Previous studies on non-linearity in the MDF are only related to the short-run dynamics and assume that long-run cointegrating relations are linear, which according to economic theory need not be the case. Thus, we really need to focus on the variables in the long-run MDF and their determinants through the adoption of a cointegrating smooth transition regression (CSTR) test developed by [I. Choi, P. Saikkonen, Testing linearity in cointegrating smooth transition regressions, Economet. J. 7 (2004) 341–365]. The reason is due to this model being more general than the traditional STR model in that it may contain several transition functions and has more than a single transition variable. Our evidence demonstrates the existence of a non-linear cointegrating relationship, and as such several transition variables should be of more concern under the non-linear hypothesis. Overall, we propose more possibilities that will bring about the unstable phenomenon of the long-run MDF. [Copyright &y& Elsevier]

Teleoperating Cyber-Physical System (TCPS) is referred as a new generation of networked teleoperating system. Question of how to enable master operator and slavers to collaborate for sensing and control is largely unexplored. This paper is concerned with a distributed formation control problem for multi-slave TCPS under time delay and actuator saturation constraints. We first develop a min-weighted rigid graph based topology optimization scheme to reduce the redundancy of communication links in slavers, such that the information fusion can be simplified in the formation controller design. The sufficient conditions for stability are presented to show that the formation controllers can stabilize the master-slave TCPS in the presence of time-varying delay and actuator saturation constraints. Finally, to show the validity of our proposed result, both simulations and experiments are performed. It is demonstrated that the topology optimization reduces the redundancy of communication links in slave site at the expense of increased convergence time, while the formation controllers guarantee global asymptotic stability of teleoperation systems subjected to time-varying delay and actuator saturation constraints. [ABSTRACT FROM AUTHOR]