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Prior research has shown that autocorrelation and variance in voltage measurements tend to increase as power systems approach instability. This paper seeks to identify the conditions under which these statistical indicators provide reliable early warning of instability in power systems. First, the paper derives and validates a semi-analytical method for quickly calculating the expected variance and autocorrelation of all voltages and currents in an arbitrary power system model. Building on this approach, the paper describes the conditions under which filtering can be used to detect these signs in the presence of measurement noise. Finally, several experiments show which types of measurements are good indicators of proximity to instability for particular types of state changes. For example, increased variance in voltages can reliably indicate both proximity to a bifurcation and the location of increased stress. On the other hand, growth of autocorrelation in certain line currents is related less to a specific location of stress but, rather, is a reliable indicator of stress occurring somewhere in the system; in particular, it would be a clear indicator of approaching instability when many nodes in an area are under stress. [ABSTRACT FROM AUTHOR]

The study on stochastic effects occurring at the nanoscales in VLSI memristive devices is a timely topic which is gaining a growing interest. Indeed, these effects are often linked to the occurrence of nonlinear phenomena, such as spatiotemporal chaos. In this paper, we present evidence that spatiotemporal chaos in VLSI memristive systems can also be tamed by exploiting the unavoidable sources of noise affecting the dynamical behavior of the device. In particular, we aim at investigating this scenario starting from the results observed in several nonlinear oscillators, where the presence of noise facilitates their synchronization. In particular, we focus on the role of noise acting on initial conditions in memristive nonlinear oscillators. In this paper, we focus on a nonautonomous memristive oscillator characterizing its dynamics with respect to the memristor initial conditions and deriving a suitable model in which they appear as further system parameters and exploiting this dependence for the synchronization of an array of coupled nonlinear chaotic memristive oscillators. [ABSTRACT FROM AUTHOR]

The aim of this paper is to study the dynamics of a permanent magnet direct current (PMDC) brushed motor while two crucial space-domain effects, namely, slotting effect and commutation phenomenon are taken into account. Semi-analytical dynamic time-domain PMDC brushed motor model inclusive of these space-domain effects is used to analyze and investigate the dynamics. Pulse width modulation operated discontinuous current PMDC brushed motor drive with steady duty cycle is employed to acquire the bifurcation patterns. The chaotic nature due to slotting effect and commutation is identified from the bifurcation patterns and reported. It also has to be admired that such nonlinear dynamical behavior with the same set of parameters at similar operating condition has not been observed when a conventional PMDC brushed motor dynamic model is considered. These space-domain effects, namely, slotting effect and commutation also have a prominent impact to make some time-domain states of a PMDC brushed motor drive chaotic. The role of slotting effect and commutation phenomenon to analyze the chaos over time-domain state variables of the PMDC brushed motor drive is investigated and validated experimentally in this paper. [ABSTRACT FROM PUBLISHER]

Hopf bifurcation phenomenon of a power system results in oscillatory dynamics which can lead to instabilities in the system. Therefore, it is desirable to operate the system such that a sufficient margin to Hopf bifurcation is ensured. This paper presents a methodology based on the adjustment of the setpoint values of the HVDC link controllers, to prevent instability or increase the stability margin of the system subject to Hopf bifurcation. In this paper, the first-order sensitivities of the Hopf stability margin to the setpoint values of the HVDC links are presented. These sensitivities identify the optimum direction to change the HVDC setpoints to steer the system away from instability, increase the stability margin, and improve the damping of oscillatory modes. The proposed method is evaluated on various system configurations subject to Hopf bifurcation phenomena caused by a variety of events, such as load and line impedance variations. Simulation results show that at the optimum operating point, for a variety of Hopf bifurcations, the stability margin and damping of the oscillatory modes improve. [ABSTRACT FROM AUTHOR]

This paper focuses on chaos control of a seven-link torque-stiffness-controlled dynamic walking model, actuated by a bio-inspired control system. The biped consists of compliant hip, knee and ankle joints and flat feet. We employed Ott–Grebogi–Yorke and delayed feedback control methods, responsible for small errors around the equilibrium solution and large errors far away, respectively. In simulation, we study the stabilization of bifurcations and chaotic behaviors under diverse actuation parameters, and the convergence speed to 1-period gaits. The results of this paper may provide insights into motion control of dynamic walking robots and principles of human locomotion. [ABSTRACT FROM AUTHOR]

It is shown that a relatively simple dynamical dc electric arc model shows complicated two-parameter (2-D) bifurcations with both periodic and chaotic responses. 2-D bifurcation diagrams for the arc model [a system of three ordinary differential equations (ODEs)] are obtained by using parallel computations because obtaining a single 2-D diagram requires solving the ODE system hundreds of thousands or even a few millions of times (depending on the intervals of parameters and assumed resolution). Several color 2-D bifurcation diagrams are presented, and the speedup factors of their parallel computations are provided. Numerical computations of periodic and chaotic responses of the 2-D bifurcation diagrams are confirmed by both the one-parameter (1-D) diagrams and the 0-1 test for chaos. Some further theoretical aspects of parallel computing of 2-D bifurcation diagrams are also considered. [ABSTRACT FROM AUTHOR]

In this paper, new formulations of the power flow and continuation power flow that allow for electro-thermal coupling in transmission lines have been proposed. The new formulations capture the overhead lines' electro-thermal coupling effects by treating their series resistances as temperature dependent variables. They generate results that can differ from the results of conventional formulations markedly, particularly for problems centring on line impedances. The paper demonstrates this by applying the new formulations to the power transfer limit calculation. Generally, power transfer limits are defined either by encountering a line's thermal limit or detecting the onset of voltage collapse in the system. Studies based on 2-bus and 14-bus test systems are used to demonstrate the efficacy of the new formulations for both situations. For these studies, specific point-to-point power transfer limits are calculated with and without the lines' electro-thermal coupling effects and the results are compared. [ABSTRACT FROM PUBLISHER]

Compliant grasping systems offer a wide range of robot hand designs. Understanding the stability behavior of compliant grasps can enhance the reliability and security of such hands. A classical result in compliant grasp mechanics states that a stable multifinger grasp can suddenly lose its stability when the finger force magnitudes exceed a critical threshold determined by the grasp's geometry. This event is known as coin snapping. This paper provides a full analysis of the coin snapping phenomenon for planar grasps governed by linear compliance laws. The analysis leads to important insights concerning compliant grasp security. For instance, does a grasping system give warning signs before an object snaps out of the fingers’ grip? Is this an inevitable phenomenon in linearly compliant grasps? By systematically studying the bifurcation patterns of compliant multifinger grasps, this paper provides analytic characterization of the stability behavior of these systems, as well as answers to the mentioned questions under certain simplifying assumptions. Graphical examples and experimental measurements illustrate and validate the results. [ABSTRACT FROM AUTHOR]

This paper presents a theoretical analysis, an optimal design method, and experimental results for a wireless power transfer (WPT) system with an intermediate coil. The analytical expression of the dc voltage transfer function is presented and discussed. In a two-coil WPT system, which has low coupling coefficient, the intermediate coil boosts the apparent self-inductance and magnetizing inductance of the primary side at around the resonance frequency of the intermediate coil, so that the apparent coupling coefficient is compensated. The coupling coefficient makes the system efficiency increase and induces bifurcation phenomenon. From the analysis, this paper proposes an optimal design method using the second resonance frequency operation with the bifurcation phenomenon and presents design procedure for high efficiency. A prototype of the WPT system with the intermediate coil is implemented and experimented to verify the validity of the analysis and the proposed design method. The prototype operates at 100 kHz switching frequency and has an air gap between primary and secondary side of 200 mm. An overall system efficiency of 95.57% has been achieved at 6.6 kW of output power. [ABSTRACT FROM PUBLISHER]

The widespread use of distributed generations (DGs) in utility distribution feeders is a trend, and it brings about several challenges to the operation, planning, and design of general distribution networks. In this paper, a comprehensive tool, Continuation Distribution Power Flow (CDFLOW), is presented and evaluated. CDFLOW can be used for tracing steady-state stationary behaviors of general unbalanced distribution systems due to various types of power injection variations, including high penetration of DGs. The major computation engine behind CDFLOW is the continuation method. Major components, either balanced or unbalanced, grounded or ungrounded, are well modeled in CDFLOW. A detailed description of CDFLOW and its implementation regarding the predictor, corrector, adaptive step-size control and parameterizations are presented. For illustrative purposes, CDFLOW was applied to the IEEE 8500-node test system and a practical 1103-node distribution networks with promising results. [ABSTRACT FROM PUBLISHER]

In this paper, we analyze a model for transport control protocol (TCP) along with a non-adaptive virtual queue (VQ) and an adaptive virtual queue (AVQ) management policy. In the class of transport protocols, we focus on compound TCP as it is the default protocol in the Windows operating system. We start by conducting a local stability analysis for the underlying fluid models. For the VQ policy, we show that small virtual buffers play an important role in ensuring stability, whereas the AVQ policy could readily lose local stability as the link capacity, the feedback delay, or the link’s damping factor gets large. With both the queue policies, the protocol parameters of compound TCP also influence stability. Furthermore, in both the models, we explicitly show that as parameters vary the loss of local stability would occur via a Hopf bifurcation. For the AVQ policy, we are also able to analytically verify if the Hopf bifurcation is super-critical, and determine the stability of the bifurcating limit cycles. Packet-level simulations, conducted over two topologies, using the network simulator (NS2) confirm the existence of stable limit cycles in the queue size. [ABSTRACT FROM AUTHOR]

Matrix-valued covariance extension and multivariate spectral estimation are formulated as generalized moment problems in the “THREE” approach and its extensions. Under this context, we discuss Theorem 6 in the title paper concerning the bijectivity of a moment map defined over a parametric family of spectral densities. In particular, we provide a counterexample in which the moment map under consideration is shown to have a critical point, namely a point at which the Jacobian loses rank. Then, with standard techniques in bifurcation theory, we conclude further that the computed critical point is a bifurcation point, which means that the moment map is not injective. [ABSTRACT FROM AUTHOR]

Resonant inductive power transfer (RIPT) is gaining in popularity for wireless charging applications of future electric transportation. A fundamental impediment to the efficient operation of an RIPT system is the existence of bifurcation phenomenon in a doubly tuned circuit. Bifurcation can be avoided by either selecting complicated control strategies or by proper design strategies. Many control strategies have been presented in the literature for avoiding bifurcation. However, systematic design strategies for avoiding bifurcation are still unknown. This paper presents a simplified, and easy to follow set of design guidelines for series–series compensated RIPT (SS-RIPT) systems. The design guidelines avoid bifurcation by calculating the parameters for a given load profile in a systematic and easy to follow approach. Following the design guidelines, a 3.6-kW setup has been fabricated as an example and verified using a finite element analysis as well as experimental testing. Selection of a resonant frequency and output voltage for 3.6 kW was influenced by the availability of testing equipment available in the lab. However, the design guidelines are generalized, and by following it, an SS-RIPT system of any frequency and output voltage rating, applicable for EV charging, can be designed. [ABSTRACT FROM AUTHOR]

In this paper, we propose a novel vessel tracking method, called active vessel tracking (AVT). The proposed method retains the major advantages that most 2D segmentation methods have demonstrated for 3D tracking while overcoming the drawbacks of previous 3D vessel tracking methods. Under the assumption that the vessel is cylindrical, thereby making its cross-section elliptical, the AVT finds a plane perpendicular to the vessel axis while tracking the vessel along its length. Also, We propose a method for vessel branch detection to automatically track complete vascular networks from a single starting point, whereas the previously proposed solutions have usually been limited in handling vessel bifurcations precisely on 3D or have required considerable user interaction. Our results show that the method is robust and accurate in both synthetic and clinical cases. In an experiment on synthetic data sets, the proposed method achieved a tracking accuracy of 96.1±0.5, detecting 99.1% of the branches. In an experiment on abdominal CTA data sets, it achieved a tracking accuracy of 98.4±0.5 for six target vessels, detecting 98.3% of the branches. These results show that the proposed method can outperform previous methods for vessel tracking. [ABSTRACT FROM AUTHOR]

This paper is devoted to the study of the long-term dynamic behavior of exploited renewable resources. The focus is on the case of protected resources, namely resources that can not be harvested when they are too scarce. The model is a controlled system composed of a nonlinear second-order single-input-singleoutput system and an on-off feedback controller. Thus, the model belongs to the class of discontinuous piecewise-smooth autonomous systems for which bifurcation theory has been recently extended. The analysis is performed through the numerical continuation of the sliding bifurcations of the system, for which specialized software has been developed. The results show that for suitable combinations of the parameters the system can have multiple attractors. [ABSTRACT FROM AUTHOR]

Guyon (Guyon J. Limit theorems for bifurcating Markov chains. Application to the detection of cellular aging. Ann Appl Probab, 2007, 17: 1538-1569) introduced an important model for homogeneous bifurcating Markov chains indexed by a binary tree taking values in general state space and studied their limit theorems. The results were applied to detect cellular aging. In this paper, we define a discrete form of nonhomogeneous bifurcating Markov chains indexed by a binary tree and discuss the equivalent properties for them. The strong law of large numbers and the entropy ergodic theorem are studied for these Markov chains with finite state space. In contrast to previous work, we use a new approach to prove the main results of this paper. [ABSTRACT FROM AUTHOR]

In this paper, we investigate dynamic properties and controllability of a cavity optomechanical system mechanically connected to a single-electron quantum shuttle, which includes three coupled modes, i.e., optical, mechanical, and electrical modes. Based on quantum description and quantum Langevin framework, the dynamics of these three modes under conditions of weak and strong optical driving are investigated via comprehensive bifurcation analysis. In the weak-driving regime, there is a transition point, where the amplitudes of mechanical and optical modes abruptly jump and the electrical mode decays to a static state. In the strong-driving regime, the three modes exhibit more complicated dynamics, where transitions of period 1-period 2 and periodic-chaotic state are observed. However, the electrical mode shows a different dynamical behavior. Finally, current analysis of the quantum shuttle is presented and discussed. The optical-driven quantum shuttle can be realized in experiments and has potential to serve as a new paradigm for exploring photon-based quantum information processing/transacting and quantum sensing. [ABSTRACT FROM AUTHOR]

This paper reports the successful navigation of a 1-mm Chrome-Steel bead along three consecutive polymethyl methacrylate channels inside the bore of a 1.5-T magnetic resonance imaging (MRI) scanner. The bead traveled at a mean velocity of 14 cm·s^-1. This was accomplished using an imaging gradient coil (IGC) insert located inside the MRI tube. While targeting one side of a bifurcation has been previously demonstrated using unidirectional gradient coils, this is the first time that magnetic resonance navigation (MRN) of a bead along consecutive channels is reported. Experimental results confirm that a clinical regular MRI can be used to propel a 1-mm device. In addition, when used at maximum power, IGC temperature rise becomes a serious issue that can ultimately damage the insert and limit the overall performance. Consequently, this paper aims to give some insight into coil temperature management for IGC-assisted procedures. A 33-min thermal stress test was carried out using 100% of the IGC power. Steady-state oscillation can be reached by interleaving propulsion periods with cooling periods, thus enabling longer propulsion procedures. Experimental data showed that the cooling time can be used for imaging purposes with no performance loss, thus enabling MRN-assisted procedures with multiplexed particle distribution assessment. [ABSTRACT FROM PUBLISHER]

Three-phase voltage source converters (VSCs) are commonly used as power flow interface in ac/dc hybrid power systems. The ac power grid suffers from unpredictable short-circuit faults and power flow fluctuations, causing undesirable grid voltage dips. The voltage dips may last for a short time or a long duration, and vary the working conditions of VSCs. Due to their nonlinear characteristics, VSCs may enter abnormal operating mode in response to voltage dips. In this paper, the transient response of three-phase VSCs under practical grid voltage dips is studied and a catastrophic bifurcation phenomenon is identified in the system. The converter will exhibit an irreversible instability after the dips. The expanded magnitude of ac reactive current may cause catastrophic consequence for the system. A full-order eigenvalue analysis and a reduced-order mixed-potential-theory-based analysis are adopted to reveal the physical origin of the large-signal instability phenomenon. The key parameters of the system are identified and the boundaries of instability are located. The bifurcation phenomenon and a set of design-oriented stability boundaries in some chosen parameter space are verified by cycle-by-cycle simulations and experimental measurement on a practical grid-connected VSC prototype. [ABSTRACT FROM AUTHOR]

This two-part paper introduces a dynamic state feedback control law that guarantees the elimination of Hopf bifurcations (HB) before reaching the saddle-node bifurcations (SNB). Part I is devoted to the mathematical representation of the detailed system dynamics, investigation of HB and SNB theorems, and state feedback controller design. For purposes of dynamical analysis, the stable equilibria of the system is obtained. Then the control system is designed with the objective of preventing the voltage collapse before the SNB, such that the structural stability of the system is preserved in the stationary branch of the solutions. The controller aims to relocate Hopf bifurcations to the stationary branch of solutions located after SNB, eliminating the HB from normal operating region of the system. In order to evaluate the performance of the proposed controller, bifurcation analysis has been performed in Part II using single-machine and multi-machine test systems. [ABSTRACT FROM AUTHOR]

This paper describes a method to recover task-related brain sources in the context of multiclass brain-computer interfaces (BCIs) based on noninvasive EEG. We extend the method joint approximate diagonalization (JAD) for spatial filtering using a maximum likelihood framework. This generic formulation: 1) bridges the gap between the common spatial patterns (CSPs) and blind source separation of nonstationary sources; and 2) leads to a neurophysiologically adapted version of JAD, accounting for the successive activations/deactivations of brain sources during motor imagery (MI) trials. Using dataset 2a of BCI Competition IV (2008) in which nine subjects were involved in a four-class two-session MI-based BCI experiment, a quantitative evaluation of our extension is provided by comparing its performance against JAD and CSP in the case of cross-validation, as well as session-to-session transfer. While JAD, as already proposed in other works, does not prove to be significantly better than classical one-versus-rest CSP, our extension is shown to perform significantly better than CSP for cross-validated and session-to-session performance. The extension of JAD introduced in this paper yields among the best session-to-session transfer results presented so far for this particular dataset; thus, it appears to be of great interest for real-life BCIs. [ABSTRACT FROM AUTHOR]

This paper presents a new class of thin, dexterous continuum robots, which we call active cannulas due to their potential medical applications. An active cannula is composed of telescoping, concentric, precurved superelastic tubes that can be axially translated and rotated at the base relative to one another. Active cannulas derive bending not from tendon wires or other external mechanisms but from elastic tube interaction in the backbone itself, permitting high dexterity and small size, and dexterity improves with miniaturization. They are designed to traverse narrow and winding environments without relying on "guiding" environmental reaction forces. These features seem ideal for a variety of applications where a very thin robot with tentacle-like dexterity is needed. In this paper, we apply beam mechanics to obtain a kinematic model of active cannula shape and describe design tools that result from the modeling process. After deriving general equations, we apply them to a simple three-link active cannula. Experimental results illustrate the importance of including torsional effects and the ability of our model to predict energy bifurcation and active cannula shape. [ABSTRACT FROM AUTHOR]

Abstract-This paper investigates impacts of various formations of hysteresis on the stability domain of ferroresonance modes of a voltage transformer (VT). Based on four different hysteretic and two single-valued polynomial models, ferroresonance behaviors of the VT are studied. The hysteretic models are developed based on the Preisach theory. The first hysteretic model accurately duplicates the measured hysteresis loops of the VT in a wide variation range of the core excitation level. The other three hysteretic models represent different hysteresis loop formations. The polynomial models are based on identical single-valued polynomial magnetization characteristics but represent different core loss resistances (i.e., constant and dynamically varying core loss resistances, respectively). All of the models represent the same core losses as the measured value to investigate impacts of hysteresis loop formations on ferroresonance modes, independent of the corresponding hysteresis losses. The studies are conducted in time domain in the PSCAD/EMTDC software environment. The studies indicate that the VT model, which duplicates the measured hysteresis loops and the measured core loss over a wide range of excitation levels, results in more ferroresonance modes, expanded stability domains, and higher overvoltages. This paper concludes that formation of hysteresis is an independent factor which significantly impacts the ferroresonance phenomenon. Not only is it a single-valued magnetization characteristic but also a generic hysteretic characteristic; if it is not accurately constructed based on the measured core hysteresis data, it can result in significant error in determining the ferroresonance overvoltages and stability domains of the ferroresonance modes. [ABSTRACT FROM AUTHOR]

The interest in variable-speed multiphase induction-motor drives has substantially increased in recent years and novel proposals show good prospects for industrial implementation in high-power applications. The additional degrees of freedom existing in multiphase machines have allowed for new applications with high torque density by current harmonic injection in concentrated winding machines. This paper addresses, for the first time, the bifurcation analysis of a five-phase induction-motor drive when a third harmonic is injected for torque-enhancement purposes. The main focus of this paper is to present a mathematically based study of the nonlinear dynamics of the proposed drive with torque enhancement. The overall bifurcation analysis for both concentrated and distributed winding machines confirms that the harmonic injection provides not only torque enhancement but also more robust controllers. This further advantage offers improved performance of multiphase drives compared to their three-phase counterparts. [ABSTRACT FROM AUTHOR]

This paper presents a Matlab-based voltage stability toolbox (VST) designed to analyze bifurcation and voltage stability problems in electric power systems. VST combines proven computational and analytical capabilities of bifurcation theory, and symbolic implementation and graphical representation capabilities of Matlab and its toolboxes. The motivation for developing the package is to provide a flexible simutlation environment for an ongoing research conducted at the Center for Electric Power Engineering (CEPE) of Drexel University, Philadelphia, PA, and to enhance undergraduate/graduate power engineering courses. VST is a very flexible tool for load flow, small-signal and transient stability, and bifurcation analysis. After a brief summary of power system model and local bifurcations, the paper illustrates the capabilities of VST using the IEEE 14-bus system as an example and describes its successful integration into power engineering courses at Nigde University, Nigde, Thrkey. [ABSTRACT FROM AUTHOR]

A set of state equations of the polarization index governing system with saturation nonlinearity is established for a hydroturbine in small perturbation. The dynamic behavior of the proportional-integral governor (controller) governing system with saturation is analyzed and the conditions for the existence of a Hopf bifurcation are obtained by using a simple nonlinear model. The stability condition, which must be satisfied in the governing system, is simulated and supported by numerical calculations. The analysis and simulation show that a supercritical Hopf bifurcation may exist in hydraulic turbine systems. The results of this paper can be considered as an explanation for the sustained oscillations recorded in hydroelectric power stations. [ABSTRACT FROM AUTHOR]

In this paper, a new nodal loading model for use in voltage stability assessment of electric power systems is proposed, and the formulation of worst cases based on this model, as well as related numerical methods, are described. In this nodal loading model, called the "hyper-cone" model, a set of future operating points in a load parameter space is modeled. That is, the "vertex" of the hyper-cone is taken to be the current operating point, and the "thickness" of the hyper-cone represents the uncertainty of future loading. The worst loading case is the point, among the set of transfer limit points on or within the hyper-cone, at which the total load is smallest. In other words, in terms of the uncertainty of future loading, the worst case corresponds to the most conservative transfer limit. Efficient numerical methods to compute this worst case are shown, and these methods are demonstrated on some sample power systems including IEEE ll8-node system. [ABSTRACT FROM AUTHOR]

The paper presents a design-oriented analysis of dc-dc converters valid for both periodic and aperiodic operation. Bifurcation and statistical analysis are applied to a peak current mode controlled boost converter. The main benefit of aperiodic (chaotic) converter operation—reduction of electromagnetic interference—is discussed. Periodic and aperiodic behavior are compared. Periodic converter operation exhibits the smallest ripple waveform but the worst (purely discrete) spectrum. Aperiodic converter operation yields a broader spectrum but a larger ripple. Tradeoffs between ripple and spectrum for the practical use of chaotic dc-dc converters are suggested. The paper discusses the choice of the converter's bifurcation parameter from the ripple and spectrum points of view. [ABSTRACT FROM AUTHOR]

This paper presents a novel approach for estimating 2-D flow angles using a high-frame-rate ultrasound method. The angle estimator features high accuracy and low standard deviation (SD) over the full 360° range. The method is validated on Field II simulations and phantom measurements using the experimental ultrasound scanner SARUS and a flow rig before being tested in vivo. An 8-MHz linear array transducer is used with defocused beam emissions. In the simulations of a spinning disk phantom, a 360° uniform behavior on the angle estimation is observed with a median angle bias of 1.01° and a median angle SD of 1.8°. Similar results are obtained on a straight vessel for both simulations and measurements, where the obtained angle biases are below 1.5° with SDs around 1°. Estimated velocity magnitudes are also kept under 10% bias and 5% relative SD in both simulations and measurements. An in vivo measurement is performed on a carotid bifurcation of a healthy individual. A 3-s acquisition during three heart cycles is captured. A consistent and repetitive vortex is observed in the carotid bulb during systoles. [ABSTRACT FROM PUBLISHER]

To date, many vibration-based sensing modalities have relied upon monitoring small shifts in the natural frequency of a system to detect structural changes (e.g., in mass or stiffness), which are attributable to the chemical or biological species, or other phenomena, that are being measured. Often, this approach carries significant signal processing expense due to the presence of electronics, such as precision phase-locked loops, when high sensitivities are required. Bifurcation-based sensing modalities, in contrast, can produce large easy to detect changes in response amplitude with high sensitivity to structural change if applied appropriately. This paper demonstrates the design and implementation of a tunable, Duffing-like electronic resonator realized via nonlinear feedback electronics, which uses a quartz crystal tuning fork as the device platform. The system in this manifestation uses collocated sensing and actuation, along with readily available electronic components, to realize the desired behavior. The sensitivity of the device is tunable via the control of feedback gain and the type of Duffing-like response (hardening or softening) is also selectable, thus creating a versatile bifurcation-based sensing platform. [2015-0014] [ABSTRACT FROM PUBLISHER]

Presents a paper which examined a technique to calculate parameters of nonlinear systems for distance to a saddle-node bifurcation. Comparison of the proposed method to determine closest saddle-node bifurcations in power system model; Analysis of the optimal shunt and series compensation.