Tuning controller problem

Continuous Binary Distillation Column 496 Controller Tuning Problem 427 Three-Stage Reactor Cascade with Countercurrent Cooling 287... 

After the type of feedback controller has been selected, we still have the problem of deciding what values to use for its adjusted parameters. This is known as the controller tuning problem. There are three general approaches we can use for tuning a controller ... 

This is an important area that has to be thoroughly analyzed and studied to obtain the desired performance of the complete line and/or its parts such as the injection mold, extruder puller, and so on. The first task is to determine what is required and how to approach any potential problem. Adequate PC and its associated instrumentation are essential for product control. Sometimes the goal is precise adherence to a control point, other times it is sufficient to maintain a control within a comparatively narrow range. For effortless controller tuning and lowest initial and operating cost, the processor should select the simplest controller (temperature, time, pressure, flow rate, etc. that will produce the desired results. For the complete line, they can range from unsophisticated to extremely sophisticated devices that interrelate information. As an example there is the computer Hosokawa Alpine... 

Real design problems involve discrete design decisions, such as layout of reactors and choice of control scheme, as well as selection of continuous design parameters, such as reactor sizes and controller tuning. The design tools pre-... 

The control computer/DCS system consists of controllers, A/D and D/A converters, and the signal conditioifing hardware and software, i.e., filtering and validation. Each of these components requires separate evaluation. Table 15.5 lists possible problems with the controller/DCS system. One way to initially check controller tuning is to place the control loop in manual (open the control loop) and observe whether the controlled variable lines out to a steady-state or near steady-state value. Comparing the open-loop and closed-loop performance indicates whether the controller is upsetting the process. If not, disturbances to the control loop in question are the primary source of the upsets. 

Step 2. Retune the temperature controller. Result the controller settings did not change significantly therefore, the controller tuning does not appear to be the problem. 

It is clear from the above that a three-mode PID controller should be the best. This is true in the sense that it offers the highest flexibility to achieve the desired controlled response by having three adjustable parameters. At the same time, it introduces a more complex tuning problem because we have to adjust three parameters. To balance the quality of the desired response against the tuning difficulty we can adopt the following rules in selecting the most appropriate controller. 

During the development of several simulation studies using the current Aspen Version 7.3, a strange low-amplitude oscillation has been experienced, which is not affected by controller tuning. The solution to the problem was found to be a modification in the integrator. 

An alternative method for overcoming the Doppler tuning problem in laser cooling has been demonstrated by Ertmer et al. 52] Instead of using a spatially varying magnetic field these authors controlled the frequency of the laser by means of an electro-optic modulator, driven by a radiofrequency source. Varying the frequency of the r.f. field applied produces sidebands to the laser frequency and these can be swept in step with the Doppler shift. 

Methods Dynamic identification techniques have been developed that are simple and provide accurate information (relay-feedback test). Controller tuning methods have improved so that a variety of different types of processes can be effectively controlled. Singular value decomposition has provided a useful tool for the problem of selecting controlled and manipulated variables. 

The main problem with all four of the tuning methods presented so far is that they all have the sole objective of reaching the SP as soon as possible. With the exception of some special cases, such as averaging level control described in the Chapter 4, this usually is a requirement. But it is not normally the sole requirement Figure 3.26 shows the performance of a controller tuned to meet this aim. However, depending on the process, this might result in excessive adjustments to the MV. In our fired heater example it is unlikely that the fuel... 

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