Sine Wave Response Research Articles

A Compound Scheme Based on Improved ADRC and Nonlinear Compensation for Electromechanical Actuator

A compound scheme, based on an improved active disturbance rejection controller (ADRC) and nonlinear compensation, is developed for the electromechanical actuator (EMA) system in this paper. First, considering the influences of backlash, friction on the EMA system, a model for the EMA system is presented. The LuGre model and Hysteresis inverse model are used to compensate for the friction and backlash phenomenon. Then, the method of improved ADRC, based on the Fal function filter and a Linear extended state observer (LESO), is investigated. Simultaneously, since the controller parameters of the improved ADRC are complicated, the non-dominated sorting genetic algorithm II (NSGA-II) is presented to optimize the controller parameters, to achieve the best dynamic response. Finally, simulation and experiment are presented to validate the effectiveness of the proposed method. Under the nonlinear compensation, the performance of the proposed compound scheme is compared with the conventional proportional integral (PI) controller, in terms of step response analysis and sine wave response analysis. Simulation and experiments show that the proposed controller provides high-performance dynamic characteristics.

Buckling and Torsional Instabilities of a Nanoscale Biological Rope Bound to an Elastic Substrate.

Rope-like structures are ubiquitous in Nature. They are supermolecular assemblies of macromolecules responsible for the structural and mechanical integrity of plant and animal tissues. Collagen fibrils with diameters between 50 and 500 nm and their helical supermolecular structure are good examples of such nanoscale biological ropes. Like man-made laid ropes, fibrils are typically loaded in tension, and due to their large aspect ratio, they are, in principle, prone to buckling and torsional instabilities. One way to study buckling of a rigid rod is to attach it to a stretched elastic substrate that is then returned to its original length. In the case of single collagen fibrils, the observed behavior depends on the degree of hydration. By going from buckling in ambient conditions to immersed in a buffer, fibrils go from the well-known sine wave response to a localized behavior reminiscent of the bird-caging of laid ropes. In addition, in ambient conditions, the sine wave response coexists with the formation of loops along the length of the fibrils, as observed for the torsional instability of a twisted filament when tension is decreased. This work provides direct evidence that single collagen fibrils are highly susceptible to axial compression because of their helical supermolecular structure. As a result, mammals that use collagen fibrils as their main load-bearing element in many tissues have evolved mitigating strategies that protect single fibrils from axial compression damage.

Response of the visual system to sine waves under various external conditions

Equations were obtained for the perception threshold of sinusoidal stimuli as a function of angular frequency, grating angular size, adaptation brightness, and duration of perception in the context of modeling the contrast sensitivity of the visual system. The calculated model sine-wave response was found to be consistent with the experimental data. The left and right edges of the response to the sinusoidal wave were found to be determined by the tremor modulation signal. We demonstrated that there are similarities and differences in the perception of sinusoidal gratings and Foucault gratings at different angular frequencies. The resulting functions can be used as a foundation for investigating the visual system under normal and pathological conditions and can also be used for engineering design calculations of optical and optoelectronic instruments.

Analysis and modeling of a proportional directional valve with nonlinear solenoid

To explain the influence of the nonlinear characteristic of a proportional directional valve with double solenoids, a dynamic model with a nonlinear performance in current–force–displacement of double solenoids proportional valve is presented. Despite the analyzing of nonlinear characteristic of the solenoids, the valve spool modeling, the orifice area and the dynamic model of the valve are also presented. The simulation model is set in MATLAB and a test rig is built for the dynamic performance test. At last, the comparison in sine wave and dynamic response of the simulation and the experiments are made. A big distortion occurs near zero spool position because the nonlinear characteristic is mainly manifested when the solenoid current is small. And it is mainly induced by the nonlinear characteristic of the solenoids and the direction switch motion of spool. The output in simulation is almost coincided with that of experimental result. That means the proposed modeling method of solenoids and valve is valid and effective. Some advanced control theories and methods can be applied simultaneously.

Integrated photonic threshold comparator based on square-wave synthesis

A photonic threshold comparator is presented. A step-like electrical-to-optical (E/O) response is obtained by employing Fourier series synthesis in which a set of sine-wave responses of different amplitudes and phases are superimposed according to the Fourier series representation of a square-wave. The proposed comparator does not rely on optical material non-linearity; rather it consists of multimode interference (MMI) couplers and phase shifters.

正弦波応答グラミアンを用いたモデル低次元化

In this paper, we propose a model reduction method by truncation of the balanced realization associated with the sine-wave response observability gramian and the controllability gramian. A feature of the present model reduction method is that the transfer function's value of the reduced-order model is equal to that of the original model at some frequency points. This method is also shown to provide the reduced-order model which minimizes an error norm of the model reduction.

The use of sinusoidal and ramp stretch stimuli in characterizing fusimotor effects on cat muscle spindles.

Comparisons were made between the results of testing muscle spindle primary afferents with low-frequency, large-amplitude sine waves of muscle stretch and with repeating ramp-and-hold stretches. Three different situations were explored, namely, activation with succinylcholine (SCh), generation of various fusimotor outflow patterns by brainstem stimulation and fusimotor activation by stimulation of single ventral root gamma-axons. With ramp-and-hold stretches the effects of bag1 fibre contraction were thought to be generally better represented by increases in the dynamic response to stretch (delta DD) than by increases in dynamic index. The equivalent effect on the sine wave response was an increase in the magnitude of the fitted sine (delta Mag). Static effects were best measured by increases in the initial frequency for ramps (delta IF) and by increases in the fitted centre frequency (delta CF) for sines. There was good agreement between sine and ramp testing in the case of SCh effects, but much less consistency during brainstem stimulation. Sine wave testing can be regarded as less efficient than ramp testing in distinguishing between static and dynamic actions because dynamic fusimotor stimulation causes equal rises in CF and Mag, but fourfold larger rises in DD than in IF. Ramp responses with combined dynamic and static fusimotor stimulation showed increases of both IF and DD as expected, but whilst sine wave responses always showed increase in CF, they often showed no increase in Mag. Comparisons of the effects of SCh, central stimulation and fusimotor stimulation showed that it is important to recognize the different effects of chain and bag2 intrafusal fibre activation as components of static fusimotor excitation. Stimulation of driving static axons (chain activation) raised the IF and CF often with 1:1 or 1:2 driving during the shortened phase of ramps and sines. However, the stretch response in both cases was either unchanged or reduced. Stimulation of a non-driving static fusimotor axon (bag2 activation) caused a marked rise in CF for sine waves and a fall in Mag, but a modest increase in ramp stretch sensitivity (DD) with no increase in dynamic index. A way is described for measuring flattening of sine wave responses as a possible way of detecting chain fibre activation. The consequences of these findings are discussed in relation to previous reports of the use of sine wave testing for assessing fusimotor mechanisms.

Pharmacokinetics and haemodynamic response after an intravenous bolus injection of clonidine in children

SummaryThe pharmacokinetics and haemodynamic response after an intravenous bolus injection of clonidine (2.5 μg·kg−1) were investigated in paediatric patients. Plasma levels of clonidine were determined by radioimmunoassay in eight ASA 1 paediatric patients (age: 33 months (SD 13), weight: 15.1 kg (SD 3.4), body surface area: 0.625 m2 (SD 0.109)). A considerably shorter terminal half‐life (mean 6.13 h (SD 1.33), harmonic mean: 5.55 h, 95% confidence interval 4.60–7.63), a smaller distribution volume (0.96 1·kg−1 (SD 0.43)) and a higher total body clearance (4.85 ml·kg−1 min−1 (SD 1.00)) were found in comparison with previously reported adult studies. The haemodynamic response was investigated during isoflurane anaesthesia in twelve ASA 1 children (age: 31 months (SD 11), weight: 14.4 kg (SD 3.1)) premedicated with rectal midazolam and atropine. A significant reduction in mean arterial blood pressure (MABP) was observed (P= 0.0032). The MABP was found to be reduced by 26.3% (SD 13.6) compared with baseline and the time for 75% of the expected blood pressure reduction to occur was 21.3 min (SD 25.6). A consistent finding in all patients was a harmonic undulation of the blood pressure implying a dampened sine wave response. A small but significant decrease in heart rate (127 bpm (SD 19) vs 119 bpm (SD 20), P= 0.006) was observed immediately after injection following which the heart rate gradually returned to the previous baseline. The observed changes in heart rate and blood pressure responses were of a moderate magnitude. The use of clonidine as a premedicant or adjunct to general anaesthesia in children appears to be appropriate from both a pharmacokinetic and haemodynamic standpoint.

Active Control of Rotating Stall in a Low-Speed Axial Compressor

The onset of rotating stall has been delayed in a low-speed, single-stage, axial research compressor using active feedback control. Control was implemented using a circumferential array of hot wires to sense propagating waves of axial velocity upstream of the compressor. Using this information, additional circumferentially traveling waves were then generated with appropriate phase and amplitude by “wiggling” inlet guide vanes driven by individual actuators. The control scheme considered the wave pattern in terms of the individual spatial Fourier components. A simple proportional control law was implemented for each harmonic. Control of the first spatial harmonic yielded an 11 percent decrease in the stalling mass flow, while control of the first, second, and third harmonics together reduced the stalling mass flow by 23 percent. The control system was also used to measure the sine wave response of the compressor, which exhibited behavior similar to that of a second-order system.

Modulation-transfer function measurement of SPRITE detectors: sine-wave response

A method is presented for measuring the modulation transfer function of signal processing in the element (SPRITE) detectors with a HgCdTe composition optimized for the 3-5-microm band. This method incorporates a 3.39-microm He-Ne laser to generate Young's fringes of varying spatial frequency, which are scanned across the detector elements. The results are consistent with theoretical models for these devices and indicate a limited resolution capability for SPRITE detectors used for the 3-5-microm band.

Motion detection and adaptation in crayfish photoreceptors. A spatiotemporal analysis of linear movement sensitivity.

Impulse and sine wave responses of crayfish photoreceptors were examined to establish the limits and the parameters of linear behavior. These receptors exhibit simple low pass behavior which is well described by the transfer function of a linear resistor-capacitor cascade of three to five stages, each with the same time constant (tau). Additionally, variations in mean light intensity modify tau twofold and the contrast sensitivity by fourfold. The angular sensitivity profile is Gaussian and the acceptance angle (phi) increases 3.2-fold with dark adaptation. The responses to moving stripes of positive and negative contrast were measured over a 100-fold velocity range. The amplitude, phase, and waveform of these responses were predicted from the convolution of the receptor's impulse response and angular sensitivity profile. A theoretical calculation based on the convolution of a linear impulse response and a Gaussian sensitivity profile indicates that the sensitivity to variations in stimulus velocity is determined by the ratio phi/tau. These two parameters are sufficient to predict the velocity of the half-maximal response over a wide range of ambient illumination levels. Because phi and tau vary in parallel during light adaptation, it is inferred that many arthropods can maintain approximately constant velocity sensitivity during large shifts in mean illumination and receptor time constant. The results are discussed relative to other arthropod and vertebrate receptors and the strategies that have evolved for movement detection in varying ambient illumination.

Estimating and removing sensor‐induced correlation from advanced very high resolution radiometer satellite data

In order to estimate the spatial covariance structure of sea surface temperature (SST) using advanced very high resolution radiometer (AVHRR) satellite data, autocorrelation induced by the sensor itself must be determined and then removed before the correlative properties of SST per se can be found. Sensor‐induced autocorrelation arises from (1) partially redundant sampling and (2) a nonideal impulse response. Simulation techniques are used to model the correlation structure produced by the AVHRR. Results indicate that an autocorrelation of 0.39 at lag 1 arises from the overlap of adjacent pixels in the alongscan direction. Autocorrelations of 0.51 (alongscan) and 0.43 (alongtrack) arise from the sensor impulse response at lag 1. The autocorrelation at lag 2 is still significant (0.07) due to the sensor impulse response in the alongscan direction. Overall, an autocorrelation of 0.46 occurs at lag 1 due to the combined effects of pixel overlap and the sensor impulse response, at nadir. Procedures for removing this sensor‐induced correlation are presented. Oceanographically, these results indicate, for example, that the gradients associated with sharp oceanic fronts will be suppressed. Application of the results to observed AVHRR satellite data indicate that correlation length scales for SST over one portion of the Gulf Stream are on the order of 20 km. The results also indicate that the effective spatial resolution of the AVHRR is roughly 1.25 km at nadir, somewhat lower than the commonly accepted value. Finally, it is concluded that the accuracy of the calculations is limited by (1) an incomplete specification of the AVHRR system modulation transfer function (MTF) and (2) the sine wave response function that is used to approximate the system MTF.

Sinusoidal and pulse responses of FIR-median hybrid filters

Amplitude and phase responses of several types of FIR-median hybrid (FMH) filters are analyzed using sinusoids and rectangular pulses as input signals. It is shown that the linear substructures used in FMH filters limit the overall filter to behave like a lowpass filter, as opposed to the standard median (SM) filter which has some spurious high-gain areas in the otherwise attenuated frequency range. It is shown that the sinewave response of the averaging FMH filter can exceed the response of the FIR subfilter by a factor of >4/ pi . The effect of the phase of the input signal is analyzed. It is found that the phase changes the sinewave responses only at some discrete frequencies. The pulse discrimination responses of several FMH filters are computed. They show that, in noisy conditions, the filter is able to retain pulses longer than the root length and to eliminate those shorter than the root length.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

Superimposing noise linearizes the responses of primary muscle spindle afferents to sinusoidal muscle stretch.

Experiments were conducted in anaesthetized and spinalized cats to measure the extent to which the non-linear response of Ia afferent fibers to sinusoidal muscle stretch as expressed by the peristimulus-time-histograms, PSTHs, can be transformed into a linear one by means of the superposition of random stretch ("mechanical noise"). The gastrocnemius muscles of one hind leg were stretched and the response to sinewave muscle stretch (amplitudes between 0.01 and 4.0 mm, frequencies between 0.1 and 20 Hz) were investigated while band-limited mechanical noise was superimposed on the sinewave stretch. The random stretch upper cut-off frequency was varied between 60 and 300 Hz; the displacements were normally distributed. The noise amplitude sigma, i.e. the standard deviation of the displacement distributions, was varied systematically between 0.002 and 0.4 mm. Mechanical noise was very effective in raising the mean discharge rate. Added to the sinusoidal stretch it prevented the cessation of firing during the release phase of the stretch cycle, or at least reduced the duration of discharge pauses, i.e., a linearization occurred. In general, the larger the noise amplitude, the more the amplitude of the fundamental harmonic component was attenuated and the phase lead reduced. Apart from this rule the particular combination of superimposing small noise (sigma less than 0.02 mm) on small sinewave stretch (A less than 0.02 mm) could enhance the depth of sinusoidal modulation of cycle histograms (compared with responses to pure sinusoids). Linearizing the sinewave response by additional noise allowed the estimation of frequency response characteristics in the otherwise non-linear range of amplitudes (sinewave amplitude 0.5-1.0 mm).(ABSTRACT TRUNCATED AT 250 WORDS)

Temporal response patterns of single auditory nerve fibers elicited by periodic electrical stimuli.

Single auditory nerve fibers exhibit firing synchronized to one or both phases of periodic AC stimulus currents. Responses to biphasic pulses depend on order and excitation sites of the two phases. Sine and triangle stimuli between 100 Hz and 500 Hz elicit similar response patterns. Responses to square waves are sometimes more synchronized and generally shifted in phase with respect to sine wave responses. Preferred firing phase(s): (1) are largely independent of stimulus intensity; (2) vary among fibers; (3) may shift continuously or discontinuously over several seconds before steady state is achieved. Responses to an unprocessed synthetic vowel stimulus were dominated by pitch period, first formant, and 'spurious' components.

Radio Frequency Response of a Large Turbine-Generator Stator Winding

Long term experience with on-line radio frequency monitoring of large turbine generators has shown a need for increased understanding of the propagation of arc generated radio frequency signals in a stator winding. This paper presents the results of an on going research program designed to obtain an increased understanding of radio frequency arc detection in large turbine generators. Test results from AC arcing response and sinewave response measurements made on a generator stator are presented in addition to the results obtained from a computer circuit analysis performed on a radio frequency circuit model of a portion of the same generator stator. These results led to a better understanding of RF arc signal propagation and helped to identify improved detection techniques. Three RF measurement techniques were studied for both the measurements and calculations, resulting in good agreement. Arc voltage detection sensitivity calculations give a minimum detectable level of arc voltage for each RF measurement technique.

Spectral response from perpendicular media with gapped head and underlayer

A general spectral formulation is presented, in the spirit of the Karlquist approximation, for the field from a gapped head with a permeable underlayer. For an infinite permeability underlayer, of particular interest in perpendicular recording, the fields and readback response are derived for sine-wave and square-wave magnetization, as well as for an isolated transition. The sine-wave response is given in a simple form, allowing interpretation in terms of a reduced pole density from the medium at the underlayer. The square-wave response is given as a Fourier series of sine-wave amplitudes. Approximate analytical functions are constructed for the response to an isolated transition.

The thermal frequency response of rooms

The theoretical background to the prediction of room thermal dynamics is described, using the sinusoidal frequency response of room air temperature to a convective heat input. A computer program is described, for predicting the sine wave response of a room over a wide range of frequency. Some computed results are presented and compared. A simple test enclosure is described and a comparison is made between computed and experimental results.

Wiener kernels and frequency response functions for the human retina.

The human electroretinogram (ERG) was analyzed for white noise and sinusoidal stimuli. The frequency response function calculated for white noise stimuli matched the Bode plot obtained using sinusoidal stimuli. Similaly, the second-order kernel accurately predicted the second harmonic of the measured sine wave responses.

矩形波MTFとColtman補正の検討

It has been known that contrast method for the measurement of response function has two ways, i.e. rectangular wave's chart method which is commonly used and sine wave's exposure method of which manufacture is technically difficult. Fundamental difference between rectangular and sine wave's response obtained with each method were studied in this paper. We assumed that six kinds of line spread distribution had its own function, F (x), respectively, and both sine and rectangular wave's response for these functions were calculated to compare. By using Coltman's formula, the rectangular wave's responses calculated above was corrected by various numbers of correction terms on its formula to observe the degree of approximation to the standard formula of sine wave's responses.