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how to use barcode scanner in asp.net c# Proportional bond zoo r2/Tr in .NET
Proportional bond zoo r2/Tr Decode QR In .NET Framework Using Barcode Control SDK for .NET framework Control to generate, create, read, scan barcode image in VS .NET applications. Generate QR Code In Visual Studio .NET Using Barcode printer for VS .NET Control to generate, create QR Code JIS X 0510 image in .NET framework applications. Time
QR Code ISO/IEC18004 Reader In .NET Framework Using Barcode reader for VS .NET Control to read, scan read, scan image in .NET applications. Generating Bar Code In .NET Using Barcode drawer for VS .NET Control to generate, create bar code image in VS .NET applications. FIG 1.23. If the proportional band is widened to 200 T /T,, the intermediate variable will not overshoot. Reading Bar Code In .NET Using Barcode recognizer for Visual Studio .NET Control to read, scan read, scan image in .NET applications. Make QR Code In Visual C#.NET Using Barcode drawer for VS .NET Control to generate, create QRCode image in .NET applications. n Ud erstanding Feedback Control
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The proport ional band of l&2/71 fits right in with t he rest of the table. Gross changes in P are required to affect the damping of the twocapacity process. It is doubtful whether any difference would be discernible between the response of a loop at 30 percent and that at 16 percent. Unfortunately, this is not always so. The twocapacity process has more tolerance for proportional band setting than any more difficult process. Earlier in the chapter it was noted that the damping of the deadtime loop is changed from zero to >iamplitude by doubling the proportional T2/T1
Dynamic Elements in the Control Loop
band. With the twocapacity process, however, the multiplication is infinite. Another important factor must be brought out. By definition of the primary and secondary capacities, 72 is never greater than ~1, regardless of their relative positions in the loop. This means that the most difficult twocapacity process will be one where 72/~1 = 1.0. For >/4amplitude damping, P would be 16 percent. By comparison, the deadtime process is 209{,3 or 12.5 times more difficult to control than the most difficult twocapacity process. Notice also that as 72 approaches zero, the process approaches single capacity and P for any damping approaches zero. It is wise therefore, in the design of the process, to make T~/T~ as low as possible. Since the natural period of the loop varies as r2 only, this should be done by reducing 72 where possible, instead of increasing 71. Proportionalplusderivative Control
Adding derivative to a proportional controller relates output to the rate of change of error: rn=$ (e+D$)+b
(1.26) where D is the derivative time. The parenthetic part of this expression is the inverse of a firstorder lagit is called a firstorder lead. In the twocapacitylevel process, de c+rzdt=h
where c is the result of changes in h. In the proportionalplusderivative controller, m is the result of changes in ethe derivative term is on the input side of the equation. Since c = r  e, the lag may be written in terms of e: If the set point is constant, dr/dt = 0.
e+r2a=r Rearranging, If the derivative time of the controller is set equal to 72, the above expression can be substituted into the proportionalplusderivative controller equa,tion, with the result nz = F (T  h) + b
1 Ud erstanding Feedback Control n
We now have proportional control of the intermediate variable. Adding derivative has caused cancelation of the secondary lag, making the process appear to be singlecapacity. In theory, the proportional band may then be reduced to zero and still produce critical damping. In practice, it is not possible. The gain of a derivative term, 2aD/r,, approaches infinity as the period of the input approaches zero. Noise is a mixture of random periodic signals. A small amount of noise at a high frequency (low period) would be amplified tremendously by a perfect derivative unit. In addition, controllers are made of mechanical or electrical parts that have certain inherent properties of phase lag. Consequently, a high limit is always placed on GD, preventing highfrequency instability within the controller. This high limit is usually about 10. A real derivative unit is actually a combination of a lead whose time constant is D and a lag whose time constant is D/10. In the twocapacity process, then, setting D = 72 will not completely cancel 72, but will replace it with a lag equal to ~~/10. The effect is considerable, however, in that the characteristics of the same process under proportional control are improved tenfold. For piamplitude damping with proportionalplusderivative control, P = 1.672 D = 72 70 = 0.2572 (1.27) Being able to reduce P by 10 also reduces offset by 10. And as a bonus, the loop cycles 10 times as fast as before. Derivative always has this effect, although nowhere else is it so pronounced as in a twocapacity process. There is one best value of derivative for a given control loop. TO O high a setting can be as harmful as none at all. The object is to cancel the secondary lag in the process. If D > TV, the controller will lead the intermediate variable, causing premature throttling of the valve. Figure 1.24 shows the effect of three different derivative settings on the same process.

