Self-tuning temperature controllers

Self-tuning temperature controllers are also available in extrusion [49]. They have become commercially available since around 1982. These controllers are microprocessor-based they are programmed to detect certain process conditions and adjust the controller parameters when necessary. These adjustments are made internally by the controller itself without the help of an operator. 

To properly evaluate the goodness of the self-tuning controller, one would have to know the details of the internal controller software. However, suppliers of self-tuning controllers are not likely to give out such information because the software is the main factor that sets one controller apart from another. Thus, the details of the software will likely be treated as proprietary information. Therefore, the best method to evaluate a self-tuning controller is to install the controller on an extrusion line and closely monitor the actual performance. 

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Figure 3. Example of Graphical Output from Analysis Mode. Reaction progress for water-jacketted reactor, with Cascade coupled temperature controllers, both in self-tuning mode.

Supervisory control and data acquisition Solid-state relay Self-tuning regulator Temperature recorder controller Transistor-transistor logic Zero order hold element... 

There are many heat choices available and a wide choice of temperature controls as there is with other fabricating processes. They range from simple mechanical thermostats to solid state units with PID control, to microprocessors that are proportional, programmable, and self-tuning (Chapter 3). 

At this writing, programmed adaptive systems have been used for certain critical applications such as temperature control in once-through boilers and heat exchangers. But there apparently is no published report on a self-tuned controller operating successfully on a critical loop in a process plant. (They have been used in aircraft controls.) From the foregoing discussion it should be evident that, no matter how skillfully mechanized, a self-tuning controller is by no means a panacea. 

It is well known that a nonlinear system with an external periodic disturbance can reach chaotic dynamics. In a CSTR, it has been shown that the variation of the coolant temperature, from a basic self-oscillation state makes the reactor to change from periodic behavior to chaotic one [17]. On the other hand, in [22], it has been shown that it is possible to reach chaotic behavior from an external sine wave disturbance of the coolant flow rate. Note that a periodic disturbance can appear, for instance, when the parameters of the PID controller which manipulates the coolant flow rate are being tuned by using the Ziegler-Nichols rules. The chaotic behavior is difficult to obtain from normal... 

Efficient and defect-free folding of the polymer will, at least, require a control of the regioselectivity of monomer incorporation and polymer tacticity. If, for example, the degree of tacticity control is poor, the stereochemical defects are irreversibly incorporated into the polymer, and the subsequent folding may fail or produce defective structures. By contrast, dynamic self-assembly may allow defects to be corrected and the hierarchical structure to be controlled or fine-tuned using external parameters (solvent, additives, temperature) prior to covalent fixation by polymerization. 

Controls (1) provide closed-loop control of temperature, pressure, and thickness (2) maintain preset parameters (3) monitor or correct equipment operations (4) con-standy fine tune equipment (5) provide consistency and repeatability in the operations and (6) provide self-optimization of the process. Most processes operate more effi-ciendy when functions must occur in a desired time sequence or at prescribed intervals of time. In the past, mechanical timers and logic relays were used. Now electronic logic and timing devices are used based on computer software programmable logic controllers. They lend themselves to easy set-up and reprogramming. See computer batch processing computer continuous pro-... 

What all of the work described so far has in common is that ratio of polycation to polyanion did not vary significantly in the investigated materials. In PEM materials this ratio cannot be tuned, because in multilayer formation the polyelectrolyte stoichiometry is controlled by self-assembly. The work of Michaels on PEC was devoted to 1 1 complexes, which are almost completely intrinsically charge-compensated. In the following sections we will review recent systematic studies on conductivity spectra of PEC, where the composition was varied. We will present the influences of PEC composition, type of alkali ions present in the PEC, temperature and RH on the dynamic conductivity of solid PEC. Based on the presented analysis, we will be able to arrive at further conclusions about how the microscopic ion dynamics in PEC can be visualized and how it is influenced by different parameters. With the help... 

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