Control System Configuration

Dynamics of Process Measurements Especially where the measurement device is incorporated into a closed loop control configuration, dynamics are important. The dynamic characteristics depend on the nature of the measurement device, and also on the nature of components associated with the measurement device (for example, thermowells and sample conditioning equipment). The term mea-.sui ement system designates the measurement device and its associated components. 

Systems and control configurations as required may not be available in the simulation code or may not be able to be described and modeled in the required detail. Depending on the application, an optional system extension or change can be defined using the existing model. Otherwise, a new model has to be developed and integrated into the code. In these cases, it is decisive for the selection of code used whether and how easily such an extension can be implemented. 

A properly configured advanced process control (APC) system could allow for on-line, continuous optimal unit operation and push the FCC operations to multiple constraints simultaneously. 

Note that in the following analyses, we will drop the prime symbol. It should still be clear that deviation variables are being used. Then this linear representation can easily be separated into the standard state-space form of Eq. (72) for any particular control configuration. Numerical simulation of the behavior of the reactor using this linearized model is significantly simpler than using the full nonlinear model. The first step in the solution is to solve the full, nonlinear model for the steady-state profiles. The steady-state profiles are then used to calculate the matrices A and W. Due to the linearity of the system, an analytical solution of the differential equations is possible ... 

The two possible control configurations for a system with two inputs and two outputs are shown in Fig. 7.77. One example of this is illustrated in Fig. 7.73 where the overhead and bottoms product compositions of a distillation process are controlled using the reflux and steam-to-reboiler flowrates respectively as the manipulated variables. Theoretically, we could employ the reflux flowrate to control the bottoms product composition and the steam-to-reboiler flowrate to control the overhead product composition. It is possible to determine which configuration produces the least interaction by forming the system relative gain array A, where ... 

Auditable validation life-cycle documents and software Procedures/records Change control Configuration control Document control On-site work procedures System security (closed and open systems)... 

Jaeger, T., Access control in configurable systems, Lecture Notes in Computer Science, 1603 289-316, 2001. 

Selective control configurations also require external feedback to protect them from reset windup. Part (d) has a combination of selective and cascade systems and in such configuration, the external reset (ER) signal (not shown) is taken from the measurement of the slave controller (FRC). 

Luyben (1993a) provided valuable insights into the characteristics of recycle systems and their design, control, and economics, and illustrated the challenges caused by the feedback interactions in such systems, within a multi-loop linear control framework. Also, in the context of steady-state operation, it was shown (Luyben 1994) that the steady-state recycle flow rate is very sensitive to disturbances in feed flow rate and feed composition and that, when certain control configurations are used, the recycle flow rate increases considerably facing feed flow rate disturbances. This behavior was termed the snowball effect. ... 

Such a partially configured system could, for example, have all control modules and graphics configured, but with no phases or procedures. The hardware supplied could be a subset of the final... 

Change Control Configuration Management System Backup/Restore Data Archiving/Restore System Access... 

When tronbleshooting a more complex control system, it is advisable to start by comparing the existing control loops with those from the piping and instrnmentation diagram (P ID). The current problem may be the resnlt of inappropriate modifications to the original control configuration. 

This section considers the application of PID controllers to coupled MIMO processes. A key issue when applying PID controllers to MIMO systems is deciding which manipulated variable should be used to control which controlled variable. This is referred to as choosing the manipu-lated/controlled variable pairings [(c, y) pairings] or the control configuration. The factors that affect the choice of (c, y) pairings are analyzed here. 

An Intelligent System for the Design of Plant-Wide Control Configuration... 

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