Overshoot Conditions Research Articles

Zero/low overshoot conditions based on maximally‐flatness for PID‐type controller design for uncertain systems with time‐delay or zeros

AbstractThis paper extends the characteristic ratio approach using novel inequalities to ensure zero/low overshoot for linear‐time‐invariant systems with zeros. The extension provided by this paper is based on the maximally‐flatness property of a transfer function, where the square‐magnitude of the transfer function is ensured to be a low‐pass filter. In order to be able to design low‐order/fixed structure controllers, a partial pole‐assignment approach is used instead of the full pole‐assignment used in the Characteristic Ratio Assignment (CRA) method. The developed inequalities and additional stability conditions are combined into an optimization problem using time domain restrictions when necessary. Although the method given in the paper is general, particular inequalities are developed for PI and PI‐PD controller cases, due to their frequent use in industrial applications. Similarly, First‐Order‐Plus‐Delay‐Time (FOPDT) and Second‐Order‐Plus‐Delay‐Time (SOPDT) systems are considered specifically, since most of the practical systems can be approximated by one of these types. The study is extended to plants with uncertainties where a theorem is developed to decrease computation time dramatically. The benefits of the proposed methods are demonstrated by several examples.

The real-time interaction model for transient mode investigations of a dual-piston free-piston engine generator

A free-piston engine generator is being developed worldwide as a novel means of electrical power generator for light vehicle application, which can provide a complementary solution towards reducing carbon dioxide emissions of road vehicles in general. However, the absence of a crank-slider mechanism in free-piston engines resulted in poor transient operations. Transient real-time modelling and simulation can provide the interaction between in-cylinder combustion with dynamics of piston motion, which has not been fully explored previously. This paper presents a real-time interaction model between dynamics of the piston motion and thermodynamics of the in-cylinder combustion of a two-stroke spark ignition dual-piston free-piston engine generator for transient operation investigations. The simulation model was developed based on the working prototype and comprised of zero- and one-dimensional sub-models interacted in real-time governed by a single timestep. The study focuses on three critical transient modes: motoring, starting and generating for the transient performance investigation. A series of experimental results during motoring was used for validating the simulation model, which showed good agreement between simulation and experiment results with 2–5% errors. The targeted brake thermal efficiency is around 20–30% at 50–60 Hz engine speed which has been shown achievable. Transient speeds of 10 and 25 Hz produced higher combustion pressure around the top dead centre but suffered pumping loss at the end of the expansion stroke. The lower peak pressures at 50 and 60 Hz have contributed to the lower brake mean effective pressure values. Maximum brake thermal efficiency of 25.8% lies in the mid-range of compression ratios between 10:1 to 15:1 while at the cyclic speeds of 50 Hz to 60 Hz. Maximum brake mean effective pressure contour occurs between 5 and 12.5 compression ratios and corresponding speeds of 10 to 30 Hz. It was observed that the excess energy from combustion results in piston overshoot condition while insufficient energy prevents the piston from achieving the targeted stroke and compression ratio. Knock events were observed for high compression ratio cases regardless of engine speed. Predictive stroke control and knock detection capability are the main contribution of the real-time interaction model presented in this paper for realistic transient operation investigation and performance prediction of the dual-piston free-piston engine generator.

Carrying Capacity for Land Rehabilitation Strategy in Merawu Watershed, Banjarnegara District

The upstream watershed area (DAS) has a function as a buffer zone. The Merawu watershed is one of the upstream parts of the Serayu watershed which is dominated by agricultural land. The declining carrying capacity of the Merawu watershed is indicated by the imbalance between supply and demand for resources in the Merawu watershed. For a long time, it can interfere with the function of the soil as life support. The research objectives are: 1) analyzing the carrying capacity of the Merawu watershed through 3 approaches, namely: ecological footprint (land capacity), water capacity, and land protection capacity. The research method used is to compare supply and demand. And 2) Formulating a recovery strategy in the Merawu watershed based on an analysis of the environmental carrying capacity and focusing on increasing the carrying capacity. The results showed that the Merawu watershed has the carrying capacity of the protection function in the overshoot condition, the water carrying capacity in the conditionally-save condition, and the carrying capacity of the land in the overshoot condition. There are five watershed recovery strategies in the upstream, middle and downstream areas to increase carrying capacity.

Analisis Stabilitas Sistem Tenaga Listrik Dengan Automatic Generation Control (AGC) Dua Area Menggunakan Fuzzy Logic Controller

The power system must be able to server the load in a sustainable manner with good service quality, such as constant voltage and frequency, quickly stabilized when load changes occur. The control generator automatically changes the frequency to the highest value when the system changes every time. This is called AGC. To keep the frequency in a stable state required frequency control system. Currently developing a lot of control system with fuzzy logic method. The simulation is performed using 5 membership functions and gives a loading of 0.1 pu, using MATLAB-Simulink software. From the analysis result, the comparison of output of frequency response in overshoot condition with conventional method yielded , settling time of 20.5 second. While the fuzzy logic controller method produces frequency response output in the overshoot state that is , settling time is 12 seconds. Whit the fuzzy logic controller method produces better performance and faster than conventional methods.

Reliability of SiC Power Devices against Cosmic Ray Neutron Single-Event Burnout

High-energy neutrons produced by cosmic ray interactions with our atmosphere are known to cause single-event burnout (SEB) failure in power devices operating at high fields. We have performed accelerated high-energy neutron SEB testing of SiC and Si power devices at the Los Alamos Neutron Science Center (LANCSE). Comparing Wolfspeed SiC MOSFETs having different voltage (900V – 3300V) and current (3.5A – 72A) ratings, we find a universal behavior when scaling failure rates by active area, and scaling drain bias by avalanche voltage. Moreover, diodes and MOSFETs behave similarly, revealing that the SiC drift dominates the failure characteristics for both device types. This universal scaling holds for SiC MOSFETs from other manufacturers as well. The SEB characteristics of Si power IGBT and MOSFET devices show that near their rated voltages failure rates of Si devices can be 10X higher than that of comparable SiC MOSFET devices. Thus, Si devices are more susceptible to SEB failure from voltage overshoot conditions.

Intelligent energy harvesting scheme for microbial fuel cells: Maximum power point tracking and voltage overshoot avoidance

Abstract Microbial fuel cells (MFCs) are renewable and sustainable energy sources that can be used for various applications. The MFC output power depends on its biochemical conditions as well as the terminal operating points in terms of output voltage and current. There exists one operating point that gives the maximum possible power from the MFC, maximum power point (MPP), for a given operating condition. However, this MPP may vary and needs to be tracked in order to maintain the maximum power extraction from the MFC. Furthermore, MFC reactors often develop voltage overshoots that cause drastic drops in the terminal voltage, current, and the output power. When the voltage overshoot happens, an additional control measure is necessary as conventional MPPT algorithms will fail because of the change in the voltage-current relationship. In this paper, the extremum seeking (ES) algorithm was used to track the varying MPP and a voltage overshoot avoidance (VOA) algorithm is developed to manage the voltage overshoot conditions. The proposed ES-MPPT with VOA algorithm was able to extract 197.2 mJ during 10-min operation avoiding voltage overshoot, while the ES MPPT-only scheme stopped harvesting after only 18.75 mJ because of the voltage overshoot happened at 0.4 min.

The Huber's Method-based Gas Concentration Reconstruction in Multicomponent Gas Mixtures from Multispectral Laser Measurements under Noise Overshoot Conditions

The Huber's Method-based Gas Concentration Reconstruction in Multicomponent Gas Mixtures from Multispectral Laser Measurements under Noise Overshoot Conditions

Dynamic Field Gradient and Erasure After Write for High Data Rate Recording

Extensive micromagnetic simulations are performed to investigate the impact of the current overshoot amplitude (OSA) on the writer dynamics. The field risetime, dynamic gradient, bubble width, as well as erasure risk due to large stray fields in the neighbouring tracks during the switching are all shown to be very sensitive to the OSA. Numerical results show that increasing OSA can sharply improve the field risetime. However, it also leads to a larger write bubble expansion during switching which could result in a wider track width and reduce track per inch (TPI) capability. The risk of side track erasure for different overshoot conditions are evaluated and also tend to increase with higher OSA. Futhermore, results for remnant fields in the media produced by the writer are shown to be extremely sensitive to the choice of damping parameter used in the simulations.

Tomographic measurements of pore filling at infiltration fronts

For certain porous media and initial conditions, constant flux infiltrations show a saturation profile which exhibits overshoot. This overshoot is the cause of gravity driven fingering, cannot be described by standard models of unsaturated flow, and is likely controlled by the exact nature of the pore filling at the initial front. Here we report synchrotron X-ray micro-tomography measurements of the porous medium and measure which pores are filled by water and air at the initial wetting front as a function of flux. We find that at high fluxes all the pores are filled with water; for intermediate fluxes, the pores along the edge of the column remain unsaturated; and for low fluxes the pores in the bulk of the experimental column remain unsaturated. This suggests that the unsaturated overshoot conditions observed at higher fluxes are primarily an edge effect of the column. The results can help delineate the correct continuum models that can capture overshoot and gravity driven fingering.

Use of stimulus-frequency otoacoustic emissions to investigate efferent and cochlear contributions to temporal overshoot.

Behavioral threshold for a tone burst presented in a long-duration noise masker decreases as the onset of the tone burst is delayed relative to masker onset. The threshold difference between detection of early- and late-onset tone bursts is called overshoot. Although the underlying mechanisms are unclear, one hypothesis is that overshoot occurs due to efferent suppression of cochlear nonlinearity [von Klitzing, R., and Kohlrausch, A. (1994). J. Acoust. Soc. Am. 95, 2192-2201]. This hypothesis was tested by using overshoot conditions to elicit stimulus-frequency otoacoustic emissions (SFOAEs), which provide a physiological measure of cochlear nonlinearity. SFOAE and behavioral thresholds were estimated using a modified maximum-likelihood yes-no procedure. The masker was a 400-ms "frozen" notched noise. The signal was a 20-ms, 4-kHz tone burst presented at 1 or 200 ms after the noise onset. Behavioral overshoot results replicated previous studies, but no overshoot was observed in SFOAE thresholds. This suggests that either efferent suppression of cochlear nonlinearity is not involved in overshoot, or a SFOAE threshold estimation procedure based on stimuli similar to those used to study behavioral overshoot is not sensitive enough to measure the effect.

Spectral integration and wideband analysis in gap detection and overshoot paradigms

Several listening conditions show that energy remote from a target frequency can deleteriously affect sensitivity. One interpretation of such results entails a wideband analysis involving a wide predetection filter. The present study tested the hypothesis that both temporal gap detection and overshoot results are consistent with a wideband analysis, as contrasted with statistical combination of information across independent channels. For gap detection, stimuli were random or comodulated 50-Hz-wide noise bands centered on 1000, 1932, 3569, and 6437 Hz. For overshoot, the masker was an 8-kHz low-pass filtered noise, with 5-ms tone bursts presented at the same center frequencies used for gap detection. Signals were presented with either 0- or 250-ms delay after masker onset. In each paradigm, the target was introduced at only one frequency or at all four frequencies. Results from gap detection conditions did not favor a wideband analysis interpretation: Results in the random condition were consistent with an optimal combination of cues across frequency. An across-channel interference effect was also evident when only one of the four bands contained the gap. Although results from the overshoot conditions were consistent with a wideband analysis interpretation, they were more parsimoniously accounted for in terms of statistical combination of information.

Overshoot and the ‘‘severe departure’’ from Weber’s law

The link between the two phenomena of overshoot and the ‘‘severe departure’’ from Weber’s law in intensity discrimination was investigated. Masked thresholds for a brief 6.5-kHz signal were measured in the presence of a notched-noise masker over a range of masker levels. The masker was either gated with the signal (overshoot condition) or was of long duration with the signal temporally centered in it. At mid masker levels, thresholds in the gated condition were substantially higher than in the long-masker condition (overshoot). The overall amount of overshoot and the variation in overshoot as a function of masker level support the view that, even at high frequencies, the overshoot effect is dominated by off-frequency masker components. Pure-tone intensity discrimination tasks were then performed in quiet, and in the presence of the same notched noise in both gated and long-duration noise conditions. It was found that the temporal characteristics of the notched noise and not, as previously thought, the pedestal determined whether or not a severe departure from Weber’s law in intensity discrimination was observed. The severe departure from Weber’s law was found only in an overshoot condition and then only when the pedestal was presented near masked threshold. This is not in accordance with a previous explanation of the severe departure in terms of two populations of auditory nerve fibers (high- and low-threshold fibers). A further experiment measured psychometric functions for the detection of the 6.5-kHz signal in both gated and long-duration notched noise. It was found that the psychometric function was markedly shallower in an overshoot condition (mid-level gated masker) than in the other conditions. These findings are consistent with a new theory, explaining the severe departure from Weber’s law in terms of both the variance in the internal representation of stimuli in an overshoot condition, and the loudness of partially masked signals.

Individual, sex, and ear differences in measures of overshoot and psychophysical two-tone suppression

Notched-noise overshoot and two-tone suppression were measured at 1000 Hz using standard procedures in 40 normal-hearing, psychoacoustically naive adults, counterbalanced for sex and listening ear. The threshold variability across listeners for the same condition often exceeded 30 dB. In the overshoot conditions, the signal was an average of 7 dB harder to detect when it was presented at the onset of a 500-ms masker (masker notch width: 1000 Hz) than when signal onset was delayed by 400 ms. Across listeners, this overshoot effect ranged from 1 to 17 dB. In the suppression conditions, for some listeners, the forward-masked signal was as much as 15 dB easier to detect when the tonal on-frequency masker (1000 Hz) and suppressor (1150 Hz) were presented together, than when the masker was presented alone, indicating suppression. For other listeners, however, presenting the masker and suppressor together increased thresholds by as much as 13 dB, indicating additional masking (negative suppression). The average amount of suppression was −1.0 dB. ANOVA tests shoed significantly more overshoot and less suppression in females than males, and significantly higher thresholds in left than right ears in the overshoot conditions. Results will be discussed in terms of possible individual, sex, and ear differences in efferent inhibition. [Work supported by NIH.]