Page 24 - DCAP608_REAL TIME SYSTEMS

Unit 2: Introduction to Real-time Applications

Notes
Figure 2.3: A Simple Block Diagram

u
y f g x

Source: http://ptolemy.eecs.berkeley.edu/~johnr/papers/pdf/thesis.pdf
Giving a name to the internal stream between g and f, this can also be written as the system of
equations

u = g(x)
y = f(u)
When implemented in a block diagram system, f and g become blocks, and x, u, and y become
streams. This simple system is shown in Figure 2.3. A very important function in signal processing
systems is the “delay” operator.

0, n k
k
y z x y ( )
n
( x n k ) n k

Did u know? The delay operator is not usually implemented as a process, but by inserting
k initial zero values into a FIFO buffer contained in the relevant channel.

2.4 Other Real-time Applications

Let us now discuss some other real-time applications.

2.4.1 Industrial Applications

Industrial applications constitute a major usage area of real-time systems. A few examples of
industrial applications of real-time systems are: process control systems, industrial automation
systems, SCADA applications, test and measurement equipment, and robotic equipment.

Example: Chemical Plant Control
Chemical plant control systems are essentially a type of process control application. In an
automated chemical plant, a real-time computer periodically monitors plant conditions. The
plant conditions are determined based on current readings of pressure, temperature, and chemical
concentration of the reaction chamber. These parameters are sampled periodically. Based on the
values sampled at any time, the automation system decides on the corrective actions necessary
at that instant to maintain the chemical reaction at a certain rate.
Each time the plant conditions are sampled, the automation system should decide on the exact
instantaneous corrective actions required such as changing the pressure, temperature, or chemical
concentration and carry out these actions within certain predefined time bounds. Typically, the
time bounds in such a chemical plant control application range from a few micro seconds to
several milliseconds.

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