Outputs variation

Gerth, R. and Hancock, W. M. 1995 Reduction of the Output Variation of Production Systems Involving a Large Number of Processes. Quality Engineering, 8(1), 145-163. 

If on-off control is being considered, the achievable performance can be estimated by considering a limit-cycle at the natural period, t . The change in concentration from maximum to minimum reagent addition, A <, must he attenuated sufficiently so that the outlet concentration variation is less than the acceptable variation, Attributing the output variation to the first harmonic... 

Here we adopt the following definition valid for linear systems a system is stable if bounded input variations produce bounded output variations as t —>oo otherwise the system is unstable (Ogunnaike Ray, 1994). One of the main issues in designing feedback controllers is stability. Let consider the response of a closed-loop system under proportional control, as deviation in outputy vs. time (Fig. 12.5). If the controller gain is moderate then y goes to zero after some oscillations. By increasing gain... 

Output variations are caused hy cyclic variation or random fluctuations. These include melt fracture, variation in screw speed, feed stock, melt temperature, take-up speed and plant voltage. A fluctuation in feed rate and temperature and melting instabilities can also cause output variations. 

Output variation can be controlled by applying the following steps ... 

In addition to increased output, grooved feed throats have a couple of other benefits. A decrease in output variation (i.e., less surging) often results from creating high barrel friction. This is because of a decreased sensitivity to fluctuations in two common variables ... 

These patterns are often related to line tension, more specifically uneven line tension. In advanced cast film lines (BOPP or BOPET), there are tension-control systems that allow tension adjustment in specific regions of the film. In these lines, a gear pump is often necessary to minimize output variation. The diehead pressure in such extrusion operations can be very high (up to 600 bar). 

FIGURE 138 Example of a hazard (output variation) caused by unequal delay paths (a) circuit for illustrating a hazard, (b) ideal case, no delays, T = T2 = T3 = 0, no hazard introduced (c) signal paths with different delays, ti + T2 + T3 > T5, hazard introduced. 

The multivari chart is used to classify the family into which the red X or pink Xs fall. A parameter that is indicative of the problem, and can be measured, is chosen for study. Sets of samples are then taken and the variation noted. The categories used to distinguish the parameter output variation are (1) variation within sample sets (cyclical variation) is larger than variation within samples or variation over time, (2) time variation (temporal variation) between sample sets is larger than variation within sample sets or variation of the samples, and (3) variations within samples (positional variation) are larger than variation of sample sets over time or variation within the sample sets. These are demonstrated in Fig. 23.21. 

For the first-of-a-kind BN GT unit, base load mode of operation was selected further BN GT units could be operated in load follow modes within electric output variation between 90 and 300 MW(e). The prerequisites for this are fast neutron spectrum (no effect of xenon poisoning in reactivity) and the use of a special gas turbine. To realize load follow operation modes, a demonstration of fuel element reliable performance under multiple power ramps and associated thermo-cycling would be needed, which could be accomplished during the operation of a first-of-a-kind plant. 

Sq2 variance of the output variations within the reclaimed slice Sx2 variance of the averages of the slices. 

On these assumptions, the reclaiming operations can be described as follows Because of the superposition of the input variations in the composition of the material stacked on the stockpile, the material reclaimed in slices at right angles to the stacking layers will be subject to certain output variations, which are of two kinds ... 

Figs. 2 and 3 show two theoretical blending bed reclaiming models. The material slices and the statistical frequency distributions of the input and output variations... 

Fig. 2 relates to reclaiming from an ideal blending bed. The continuous line represents the input variations, the dotted line the output variations. Ideal" stacking of the material signifies that the chemical composition at every cross-section of the blending bed is equal to the overall average composition ... 

The remaining output variations exist only within the slices of material. There are no variations between one slice and another. 

Sa overall variance of the input variations Sp2 overall variance of the output variations... 

For estimating the output variations the following relation is available ... 

Table 2.1 Typical Power Output Variations in Satellite Solar Panels...

The best fits parameter indicates the percentage of output variation that is reproduced by the model. 

As can be seen, a model with eight parameters na = 4, nb = 4, nk = l(or/ , the dead time) leaves 4% of the output variation unexplained. For models with more parameters, there is little advantage in reducing the model error, the percentage unexplained output remains around 4%, this will be primarily process noise. 

Fig. 52. Sensor output variation with the SO2 gas concentration at 973 K. Solid line, calculated EMF (Imanaka...

Fig. 54. Sensor output variation with the NOj or CO2 gas concentration. Open squares, N02(S02 content 230 ppm) solid circles, CO2 (SO2 content 330ppm) solid lines, calculated EMF (Adachi and Imanaka 1991). (Reprinted by permission of the publisher, Kodansha Ltd.)...

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