Introduction - Advanced Control and Supervision of Mineral Processing Plants - page 8

cated or confusing presentation of any information can lead to serious operational
problems. The displays can take different forms and in general include mimic di-
agrams of the process displaying the status and continuous measurement values.
In many modern installations these displays are supplemented by closed circuit
television cameras, which give an even more enhanced level of plant control.
The operator can override the process through specialized keyboards or pointing
devices such as a mouse or trackballs.
2. Data acquisition and processing. This function processes the data obtained from
the sensors and sends suitable commands to the actuators. Sensors are devices
that obtain information in the form of one or more physical quantities, and con-
vert it into an electrical output signal. They consist of two main basic compo-
nents: (i) a primary measuring element, referred to as a transducer; and (ii) a
transmitter unit, responsible for producing electrical output that has some known
relationship to the physical measurement. Normally, the performed processing
actions are signal filtering, signal sampling and data conversion from raw val-
ues to engineering units. Most of these functions are now performed within the
instrument itself. The advent of more sophisticated sensors, such as visual sen-
sors, has increased the complexity of this function; some related challenges are
described in Chapter 4. The real-time storage of important variables is also car-
ried out by this function. This information can then be used for further process
analysis.
3. Communication. This function deals with communication between the control
system function and other computer systems. In many situations, control actions
need to be supplemented with data located in other systems and communication
between different control or information systems is required. This is also a key
function associated with data acquisition, since all the measurement data can be
digitally transmitted through dedicated fieldbuses such as Foundation fieldbus or
Profibus.
4. Regulatory control. This comprises a combination of discrete and continuous
control functions, which aims at stabilizing the process and keeping its opera-
tion within safe margins for the process, equipment and the workforce.
1.3.2 Advanced Functions
1. Process analysis. This includes tools for modeling and analyzing the process, as
well as incoming flows. These functions can be used to analyze the whole pro-
cess starting with the raw materials through all the process steps down to the end-
products. The operational variables can be analyzed to assess inter-dependencies,
to identify possible improvements based on these findings, and to devise new op-
erational scenarios. In addition, a valuable process tool is signal-characterization
which can reveal how often and by how much disturbances change.
2. Optimization. This function seeks to improve the operational level by taking ac-
tions according to a given performance index. These improvements can be ap-