Image Processing Reference
In-Depth Information
TABLE .
ISA- Usage Classes
Category
Class
Application
Description
Safety
Emergency action
(Always critical)
Control
Closed-loop regulatory
control
(Often critical)
↑
Closed-loop
supervisory control
(Usually noncritical)
Importance of message
timeliness increases
Open-loop control
(Human in the loop)
Monitoring
Alerting
Short-term operational consequence (e.g.,
event-based maintenance)
Logging and
download-
ing/uploading
No immediate operational
consequence (e.g., history collection,
sequence-of-events, preventive
maintenance)
27.2.3.3 Same-Same, but Different
Industrial automation is a broad industry and comprises many segments and application domains.
A common way to divide the market is according to the type and characteristics of the process being
controlled:
•
Process automation (continuous processes)
•
Discrete manufacturing (manufacturing of discrete units)
•
Hybrid automation (mix of continuous and discrete)
The industry segments can be characterized by a number of process attributes that govern the
requirements on wireless communication technologies, and consequently also the design and imple-
mentation. Table . below provides a description of key process attributes and their impact on the
requirements and design of wireless technologies.
Although similar (bad) environmental conditions can be found throughout the various indus-
try segments, there are distinct segment-specific requirements that have a dramatic impact on the
wireless technologies. Figure . provides a comparison of the key process attributes within process
automation and discrete manufacturing (note that the scale is logarithmic).
As illustrated in Figure ., the two industry segments have quite different characteristics, and
consequently also pose quite different requirements on the wireless technologies employed.
Even though industrial automation standardization activities in the wireless domain have started
out with a quite holistic view of the processes and target applications, these distinct differences have
led to the forming of separate working groups targeting process and discrete applications. For an
overview of the industrial automation wireless standards landscape, see Section ..
27.3 Development Challenges
The previous section presented a definition of the classical WSN, and contrasted that to the complex
set of requirements and applications of industrial automation. hese requirements and use-cases have
a dramatic impact on the development of WSN devices.
Figure . depicts a generic development process.
Embedded development methodology and development processes in general are complex subject
matters that merit a book of its own to do the topic justice. he process depicted above thus only aims
at highlighting some key characteristics of WSN development projects:
. A thorough requirements analysis is required in order to be able to select the right
communications technology.
. Choice of technology is not driven by the requirements alone. Factors such as standards
compliance and legacy systems also have a large impact on the final choice.
