Passive Bridge Research Articles

Design and control of high-speed railway bridges equipped with an under-deck adaptive tensioning system

This work investigates the application of an external adaptive tensioning (EAT) system for high-speed railway (HSR) bridges. The design of HSR bridges involves strict displacement and acceleration limits, which typically results in oversizing. The EAT system comprises under-deck cables deviated by compressive struts that are equipped with linear actuators. Since the cable is eccentric to the bridge neutral axis, tensioning the under-deck cables by adjusting the length of the linear actuators generates a bending moment that counteracts the effect of the external loads. The response under variable loading is reduced by computing the actuator commands with a linear quadratic regulator (LQR). Numerical results show that active control through the EAT system allows satisfying displacement and acceleration limits, which otherwise cannot be met without increasing the stiffness and mass of the bridge. A significant reduction of the response is achieved when resonance conditions occur. In addition, peak stresses are significantly reduced, showing the potential for fatigue-life extension. Parametric analyses comparing different bridge depths and spans, EAT system dimensions, controller parameters and actuator placement are carried out to investigate system efficacy. Results show that the adaptive bridge solution can achieve up to 32% mass savings compared to an equivalent passive bridge.

Analysis of Losses in Two Different Control Approaches for S-S Wireless Power Transfer Systems for Electric Vehicle

This paper presents the study and detailed analysis of converter losses at different stages together with the series-series (S-S) compensating coils in wireless power transfer (WPT) systems, via two distinct approaches to control the power converters. The two approaches towards wireless DC–DC power flow control are termed as the Single Active High-Frequency Wireless Power Transfer (SAHFWPT) system and the Dual Active High-Frequency Wireless Power Transfer (DAHFWPT) system. The operation of converters in SAHFWPT and DAHFWPT are controlled by the extended phase shift (EPS) and dual phase shift method respectively. The general schematic of the SAHFWPT system consists of an active bridge and a passive bridge, while the schematic of the DAHFWPT system consists of both active bridges. The efficiency evolutions of ideal SAHFWPT and DAHFWPT are far away from the real ones. Moreover, this article analyzes the operation and losses of the uni-directional power flow of the WPT system, i.e., from the DC bus in the primary side to the battery load in the secondary side. The loss estimation includes high-frequency switching losses, conduction losses, hard turn on and turn off coil losses, etc. Moreover, the efficiency of the WPT system depends on operation of the converter. A 50 W–3600 W Power range system at a resonant frequency of 85 kHz is implemented in MATLAB/SIMULATION to demonstrate the validity of the proposed method.

Local Autonomy-Based Haptic-Robot Interaction With Dual-Proxy Model

We present a new paradigm for performing remote haptic-robot interactive operations. The new paradigm is anchored on an architecture that combines local autonomy with a high-level exchange strategy of reference input. This represents a departure from the conventional reliance on direct exchange of low-level control signals in a global feedback control system. The new approach establishes two local autonomous controllers acting on the robot and the haptic device, interfaced at a higher level via a dual-proxy model. The dual proxy is a passive bridge between the local autonomous controllers. It generates appropriate motion and force reference inputs that are consistent with the task physical interactions and the levels of autonomy. Its model is adjusted online with respect to exchanged position, contact, and environment geometry information. A key component in this methodology is the perception algorithm on the robot side, the force-space particle filter, designed to reliably estimate in real time the environment contact geometry. The series of simulations and physical experimental validations of the approach demonstrate the transparency and high fidelity in haptic-robot interaction and its inherent robustness to communication delays.

An Analysis-Supported Design of a Single Active Bridge (SAB) Converter

Currently, due to its various applications, the high-performance isolated dc-dc converter is in demand. In applications where unidirectional power transfer is required, the single active bridge (SAB) is the most suitable one due to its simplicity and ease of control. The general schematic of the SAB converter consists of an active bridge and a passive bridge, which are connected through a high-frequency transformer thus isolated. The paper summarizes the behavior of this converter in its three operation modes, namely the continuous, discontinuous, and boundary modes. Later, the features of this converter, such as its input-to-output and external characteristics are discussed. Input-to-output characteristics include the variation of converter output power, voltage, and current with an input control variable i.e., phase-shift angle, whereas the external characteristic is the variation of the output voltage as a function of output current. In this discussion, the behavior of this converter in its extreme operating conditions is also examined. The features of the characteristics are elucidated with the help of suitable plots obtained in the MATLAB environment. Afterward, the specifications of a SAB converter are given and, based on the results of the analysis, a detailed design of its electrical elements is carried out. To validate the features and the design procedures presented in this paper, a prototype is developed. An element-wise loss estimation is also carried out and the efficiency of the converter has been found to be approximately equal to 93%. Lastly, the test was executed on this prototype, confirming the theoretical findings concerning this converter.

Rapid Antimicrobial Susceptibility Testing through Phase Noise Measurements of Cellular Biophysics

Antibiotic-resistant strains of pathogenic bacteria are commonplace today, with costs of infections and complications nearing $30 billion each year in the United States. At issue is the rapid evolution encouraged by improperly or over-prescribed antibiotics, which happens in part because culture-based methods for identifying pathogens to guide antibiotic selection are slower (on the order of days) than the progression of dangerous infections. We have developed a label-free measurement technique with the potential to select effective antibiotics within ninety minutes of sample collection. It circumvents the need to identify pathogens by name, instead sensing changes in phase noise of a resonating quartz crystal to which the microbes are adhered. Changes in phase noise are hypothesized to reflect diminished nanomechanical fluctuations of whole cells that indicate an early response to the drug. A novel measurement system that employs a very high stability tunable frequency source and passive bridge electronics has been built to measure phase noise of quartz crystal resonators that are held at controlled temperature with enclosed liquid handling. As a proof of concept we have demonstrated diminished phase noise of Escherichia coli K-12 bacteria upon exposure to the antibiotic ampicillin. Corresponding ampicillin-free controls and microscopic imaging during phase noise sensing demonstrate that phase noise drops are not due to loss of cells from the crystal surface. The measurement technique along with these early results will be discussed in detail.1. Antibiotic resistance threats in the United States, 2013. Centers for Disease Control and Prevention.

Maximum energy transfer condition for piezoelectric energy harvesters with single pulsed vibration inputs

The optimal capacitive load condition is derived for a passive bridge rectifier to harvest the maximum amount of energy when a piezoelectric generator (PG) receives a single vibration pulse (e.g. a button press). When the PG is modelled as a current pulse generator with an internal shunt capacitance (CP), it is shown that an ideal bridge rectifier collects the maximum energy when its output capacitance is set to 3·CP. The impacts of the nonzero turn-on voltage and on-resistance of the diodes are also discussed. The experimental results with a 300 mm2 lead magnesium niobate-lead titanate PG and a Schottky-bridge rectifier with 0.22 V turn-on voltage demonstrate that the maximum energy transfer occurs at a capacitance ratio of 3.3, collecting 117 μJ from a single button press.

Self-sensing and quality factor control circuits for piezoelectric millimeter-sized resonant cantilevers

For ever-increasing applications of resonant piezoelectric-excited millimeter-sized cantilever (PEMC) such as biosensors, viscosity, and density sensors, the need for design and implementation of a portable circuit for measuring the resonant frequency shift and/or the variation in the quality factor of PEMC becomes crucial. In this article, active and passive self-sensing bridge circuits are designed, fabricated, and implemented for a PEMC. The performances of these circuits are examined for the resonant frequency and quality factor measurements for vibration of PEMC in two different environments. For this purpose, a parameter-tuning procedure for the passive bridge based on experimental identification of Van Dyke model parameters is proposed and applied for the vibration of PEMC in air and 98% glycerol solution. Also, a compensation method for potential instability of active bridge circuit is proposed and developed experimentally for the vibration of PEMC in these environments. To increase the quality factor, the fabricated passive bridge is used in a designed control circuit, which is based on positive feedback signal proportional to the vibration velocity. The experiments show that with the proposed and implemented control circuit, the quality factor will increase by about 80% in air and 25% in glycerol.

A descriptor approach to formalizing the synthesis of passive four-armed AC bridge circuits

A procedure is considered for the formalized synthesis of passive bridge circuits, which is based on a descriptor approach to the analysis of null-balance measuring circuits for alternating current. The starting point lies in generalized relations between the parameters of the measurable immitances and bridge circuits, in which one determines the set of values for the Boolean functions relating these parameters to the circuit characteristics.

PTEN, more than the AKT pathway

Phosphatase and tensin homolog deleted on chromosome 10 (PTEN)/phosphatidylinositol 3-kinase (PI3K)/AKT constitute an important pathway regulating the signaling of multiple biological processes such as apoptosis, metabolism, cell proliferation and cell growth. PTEN is a dual protein/lipid phosphatase and its main substrate phosphatidyl-inositol 3,4,5 triphosphate (PIP3) is the product of PI3K. Increase in PIP3 recruits AKT to the membrane where is activated by other kinases also dependent on PIP3. Many components of this pathway have been described as causal forces in cancer. PTEN activity is lost by mutations, deletions or promoter methylation silencing at high frequency in many primary and metastatic human cancers. Germ line mutations of PTEN are found in several familial cancer predisposition syndromes. Recently, many activating mutations in the PI3KCA gene (coding for the p110alpha catalytic subunit of PI3K) have been described in human tumors. Activation of PI3K and AKT are reported to occur in breast, ovarian, pancreatic, esophageal and other cancers. Genetically modified mice confirm these PTEN activities. Tissue-specific deletions of PTEN usually provoke cancer. Moreover, an absence of PTEN cooperates with an absence of p53 to promote cancer. However, we have observed very different results with the expression of activated versions of AKT in several tissues. Activated AKT transgenic lines do not develop tumors in breast or prostate tissues and do not cooperate with an absence of p53. This data suggest that an AKT-independent mechanism contributes to PTEN tumorigenesis. Crosses with transgenic mice expressing possible PTEN targets indicate that neither cyclin D1 nor p53 are these AKT-independent targets. However, AKT is more than a passive bridge toward PTEN tumorigenesis, since its expression not only allows but also enforces and accelerates the tumorigenic process in combination with other oncogenes.

A Descriptive Approach to Analyzing Passive Four-Armed AC Bridge Circuits

A descriptive analysis is applied to alternating-current circuits, which is extended to the most complicated subclass of measurement circuits: passive four-armed bridge ones. General relations are derived between parameters of the measurement specimen and those of the bridge circuit, together with synthesis rules for these circuits that inexplicitly incorporate those relations. The results completely formalize synthesizing passive bridge circuits and reduce the treatment to choosing between possibilities.

Strain gauge transducers: an evaluation of accuracy limits

The detection and the conditioning of a strain gauge bridge low-level signal is analysed. Common DC half- and full-bridge configurations are examined as well as instrumentation amplifiers with respect to the deviations from an ideal behaviour. A peculiar bridge configuration, called ‘active’ bridge, which uses two OP-AMPs, is discussed and its performance is compared with that of the conventional configurations. The sensitivity obtained in this configuration is twice the correspondent sensitivity of the passive bridge. Nonlinear effects due to component tolerances and drifts are usually small, especially for the ‘active’ half-bridge. The noise and offset equivalent input voltages are lower in the active bridge. In this study, conventional metallic foil strain gauges are considered. The influence of higher strain gauge sensitivies on the deviations and inaccuracies is finally discussed.