Maximum Allowable Gain Research Articles

Nonfragile high‐gain observers for nonlinear systems with output uncertainty

AbstractIn this paper, we present the definitions of nonfragile high‐gain observers and design method for lower‐triangular nonlinear systems with output uncertainty. Radial basis function neural networks (RBFNNs) are used to approximate the output uncertainty. By inserting an output filter and an input‐output filter, a new augmented adaptive observable canonical form is derived. Then, a corresponding observer with gain perturbations is designed to estimate the states and the coefficients of the RBFNNs, and a disturbance observer is designed to estimate the approximation error. The maximum allowable gain perturbation is also given. Then, the obtained results are extended to nonlinear systems in adaptive observer form with output uncertainty. Finally, some numerical simulations are offered to corroborate the theoretical results.

Examining the impacts of DM filters to PFC isolated Ćuk converter for DCM operation by comparing Si and SiC MOSFET

Examining impacts of differential mode (DM) filter topologies covering pi, LC with damping, LC, LCL filter through isolated Ćuk single phase PFC converter is realized in this paper regarding to power factor, THD and efficiency. Application of PFC isolated Ćuk converter is conducted with 42 kHz switching frequency and 50 W power. Each filter is modeled, designed, and applied experimentally via isolated PFC Ćuk converter. Average model derivation based on state-space, for DCM operation of input side inductor of isolated PFC Ćuk converter that is not introduced in literature is the main contribution of the paper. Second main contribution is to analyze filter types by linear methods for the transfer functions cascading the converter and filter transfer functions, which is not presented for PFC converters. It is also presented that solely LCL filter which is not analyzed for PFC converters in detail in literature, does not give desired results. So, increasing the effectivity of LCL filter, new filter structure LCL with parallel C filter is proposed and modeled in this paper. Thanks to the applications, presented results of LCL with parallel C filter is better than others with 4.9% current THD and ‘1’ power factor. Proposed LCL filter ensures 45% reduction of total inductor value, comparing to LC filter. Besides, LCL with C filter provides better control characteristics with maximum allowable gain for stability as 0.7585 higher than other topologies. Moreover, practical design methodology of filter types avoiding complex mathematical procedure is given in this paper. Applications with each filters provide THD requirements, obtained 4.9% as a best value, lower than IEC61000-3-2 standard. Maximum percentage improvement comparing to the IEC61000-3-2 is 27.5% for third harmonic. Furthermore, SiC and Si Mosfets are employed separately in the converter and compared by using each DM filters regarding to power factor, THD, efficiency through applications. As a result, better efficiency with SiC Mosfet as 83% and better THD with Si Mosfet as 4.9% are conducted.

Performance Resilience Analysis of Dynamic Feedback Controllers for both Multiplicative and Additive Gain Perturbations

In this work, a procedure is presented for performance resilience analysis of continuous-time systems controlled by full-order dynamic feedback compensators. The resilience property is defined in terms of defining maximum perturbations on both the controller and observer gains that will maintain controller and observer eigenvalues in disjoint regions in the complex plane so that the closed loop system will sustain certain performance characteristics. The desired performance is characterized by the response speed and magnitude bounds on the response. Therefore, the intersection of two regions are chosen, vertical strips and sector regions, to guarantee upper and lower bounds on the settling (or response) time and an upper bound on the percent overshoot simultaneously. Maximum allowable gain perturbations are obtained based on the designer’s choices of closed loop eigenvalues and the regions in which eigenvalues remain when the gains are perturbed. The linear matrix inequality technique is used throughout the analysis process. Illustrative examples are included to demonstrate the effectiveness of the proposed methodology.

Neural Network Based Lna Design for Mobile Satellite Receiver

Paper presents a Neural Network Modelling approach to microwave LNA design. To acknowledge the specifications of the amplifier, Mobile Satellite Systems are analyzed. Scattering parameters of the LNA in the frequency range 0.5 to 18 GHz are calculated using a Multilayer Perceptron Artificial Neural Network model and corresponding smith charts and polar charts are plotted as output to the model. From these plots, the microwave scattering parameter description of the LNA are obtained. Model is efficiently trained using Agilent ATF 331M4 InGaAs/InP Low Noise pHEMT amplifier datasheet and the neural model’s output seem to follow the various device characteristic curves with high regression. Next, Maximum Allowable Gain and Noise figure of the device are modelled and plotted for the same frequency range. Finally, the optimized model is utilized as an interpolator and the resolution of the amplifying capability with noise characteristics are obtained for the L Band of MSS operation.

Computational model to design plastic multi-layer films for food packaging to assure a shelf life at the best cost

A computational model to design plastic food packaging is proposed. The model minimizes the cost of the multi-layer structure satisfying the specific product requirements, using a heuristic optimization algorithm. The product requirements are defined by the expected shelf life, the storage conditions, the water sorption isotherms of foods and the maximum allowable gain or loss of gases (O2, CO2, N2, etc.) and moisture for the packaged food. In order to assure the food shelf life, these product requirements should be fulfilled to estimate the maximum permeance values of the plastic package. The computational algorithm automatically generates different multi-layer film structures that satisfy the product requirements. This algorithm combines different polymeric materials taking into account the barrier properties and cost of each layer, the compatibility between layers, the maximum number of layers and the minimum and maximum film thickness for each layer. Temperature and relative humidity corrections for the permeance calculations are considered. Permeance calculations of several barrier films are compared with oxygen transmission rate (OTR) and water vapor transmission rate (WVTR) measurements. The optimization model algorithm is evaluated by means of standard numerical routines and numerical benchmarking.

The effects of mechanical response on the dynamics and string stability of a platoon of adaptive cruise control vehicles

The dynamics of a platoon of adaptive cruise control vehicles is analyzed for a general mechanical response of the vehicle. Effects of acceleration-feedback control that were not previously studied are found. For small acceleration-feedback gain, which produces marginally string-stable behavior, the reduction of a disturbance (with increasing car number n) is found to be faster than for the maximum allowable gain. The asymptotic magnitude of a disturbance is shown to fall off as erf(ct.√n) when n→∞. For gain approaching the lower limit of stability, oscillations in acceleration associated with a secondary maximum in the transfer function (as a function of frequency) can occur. A frequency-dependent gain that reduces the secondary maximum, but does not affect the transfer function near zero frequency, is proposed. Performance is thereby improved by elimination of the undesirable oscillations while the rapid disturbance reduction is retained.

Multivariable H2 and H∞ control for a wind energy conversion system: a comparison

The Wind Energy Conversion System (WECS) is a nonlinear system, highly dependent on a stochastic variable characterized by sudden variations, and subjected to cyclicaldisturbances caused by operational phenomena. Thus, the quality of a WECS controller is measured by its capacity to deal with unmodeled dynamics, stochastic signals, andperiodic, as well as non-periodic disturbances. Since the WECS' objectives can be easily specified in terms of maximum allowable gain in the disturbance-to-output transfer functions, H2 and H∞ methodologies can be good options for designing a WECS stabilizingcontroller, combining specifications such as: disturbance attenuation, asymptotic tracking, bandwidth limitation, robust stability, and trade-off between performance and controleffort. Designs for WECS multivariable feedback controllers based on H2 and H∞ methodologies are presented in this paper. The performances of both controllers are computationally simulated, analyzed and compared in order to identify the advantages anddrawbacks of each controller design.

The EarLens system: New sound transduction methods

The hypothesis is tested that an open-canal hearing device, with a microphone in the ear canal, can be designed to provide amplification over a wide bandwidth and without acoustic feedback. In the design under consideration, a transducer consisting of a thin silicone platform with an embedded magnet is placed directly on the tympanic membrane. Sound picked up by a microphone in the ear canal, including sound-localization cues thought to be useful for speech perception in noisy environments, is processed and amplified, and then used to drive a coil near the tympanic-membrane transducer. The perception of sound results from the vibration of the transducer in response the electromagnetic field produced by the coil. Sixteen subjects (ranging from normal-hearing to moderately hearing-impaired) wore this transducer for up to a 10-month period, and were monitored for any adverse reactions. Three key functional characteristics were measured: (1) the maximum equivalent pressure output (MEPO) of the transducer; (2) the feedback gain margin (GM), which describes the maximum allowable gain before feedback occurs; and (3) the tympanic-membrane damping effect (DTM), which describes the change in hearing level due to placement of the transducer on the eardrum. Results indicate that the tympanic-membrane transducer remains in place and is well tolerated. The system can produce sufficient output to reach threshold for those with as much as 60dBHL of hearing impairment for up to 8kHz in 86% of the study population, and up to 11.2kHz in 50% of the population. The feedback gain margin is on average 30dB except at the ear-canal resonance frequencies of 3 and 9kHz, where the average was reduced to 12dB and 23dB, respectively. The average value of DTM is close to 0dB everywhere except in the 2–4kHz range, where it peaks at 8dB. A new alternative system that uses photonic energy to transmit both the signal and power to a photodiode and micro-actuator on an EarLens platform is also described.

Increasing repeater span in high-speed bidirectional WDM transmission systems using a new bidirectional EDFA configuration

When fiber-optic systems contain erbium-doped fiber amplifiers (EDFA), reflections are enhanced by the gain of the amplifiers and severe system performance degradations and bit-error-rate (BER) floors can be observed. This provides a very restrictive limit on the usable amplifier gain. We present a new configuration for a bidirectional EDFA that allows for a significantly higher maximum allowable gain while introducing a very small BER penalty. A 2.5 Gb/s, 300 km bidirectional wavelength-division multiplexing (WDM) transmission experiment using the new bidirectional EDFA is reported. Experimental results show that allowable gain of the new EDFA is significantly increased while the associated BER penalty remains negligible.

Impact of multiple reflection noise in Gbit/s lightwave systems with optical fibre amplifiers

Severe systems degradations and bit error ratio floors are observed in high-speed (11 Gbit/s) lightwave transmission systems with optical amplifiers due to multiple reflections which convert laser phase noise into intensity noise. This effect is greatly intensified due to the amplifier gain, and also because of the additional presence of signal-spontaneous emission beat noise. Furthermore, even if discrete reflections in the fibre transmission path are eliminated, the multiple reflection noise arising from Rayleigh backscattering ultimately limits the maximum useful gain for optical repeaters to a level far below the maximum allowable gain to avoid lasing, unless optical isolators are employed.

Necessary and Sufficient Conditions for the Stability of Buck-Type Switched-Mode Power Supplies

Necessary and sufficient conditions are derived for the small-signal stability of forward (buck-type) switched-mode power supplies with a constant switching frequency in the continuous conduction mode. It is shown that the maximum allowable gain of the error amplifier is a function of the modulation process, the duty cycle of the switch, and the filter elements of the supply. Under certain conditions, the gain can be made infinitely large. This can occur for duty cycles less than 50 percent if the end of the ``on'' time is modulated and for duty cycles between 50 and 100 percent if the start of the ``on'' time is modulated. Excellent agreement with computer simulations and laboratory measurements has been observed.

Quasi-asymptotic stability of a class of non-linear systems

The paper presents an extension of Popov's frequency domain stability criterion to quasi-asymptotic stability of a class of systems involving both distributed as well as lumped elements and one bounded non-linear element. The results are presented in the form of a theorem to cover plants which may include a pure integration as well as direct transmission. Through a computer-derived transformation of the classical Popov plot, a simple interpretation of the new theorem for quasi-asyinptotic stability is given. It is shown that significant improvement in maximum allowable gain is obtained over the Popov value for a system not satisfying Aizerman's conjecture.