wilamowski-b-m-irwin-j-d-industrial-communication-systems-2011

27-8 Industrial Communication Systems
27.3 Industrial Multimedia Applications
27.3.1 Monitoring Applications
Monitoring applications are very well known in industrial areas, although mainly at the LAN and WAN
level. Typically, in all kinds of industries machines are quite large, and because of this different cameras
transmit the information to the control point to ensure the correct management of the machine by the
worker. Another application is that the images are required from another point of the factory for work
supervision from global control centers. These systems are often used in areas that present a certain
danger for the worker. Finally, global control centers need to monitor the remote installations’ state
in order to control their performance (especially to control network utilities [SAS06][SSA07]). In all of
these situations, multimedia information is transmitted through networks for a better use of machines
and equipments due to the rich context information that multimedia has for the workers.
The requirements of this type of application are not typically too demanding, but they are connected
to the final use of the images in the application and the networks available, since it can involve strong
limitations. The image resolutions are usually between CIF and 4CIF or VGA since these resolutions are
more than adequate to gather the information of interest and do not overload the human capacity for
processing this type of information. Greater resolutions can be used if the images, in addition to live
human supervision, are stored for a later use (e.g., technical reports in the control of utilities networks,
complaints in surveillance applications). The quality of the images is another important parameter, and
for monitoring applications, it is considered appropriate to have at least 30 dB. Concerning transmission
times, we can consider here two groups. In the applications where only live monitoring is performed
(without storage) and the information is used by the worker who is operating the machine, this latency
has to be lower than 1000.ms, since the machinery has to be managed with real-time information. In
the second group we can consider the applications where a human operator receives and processes the
information, usually from several sources, and in which there is no storage. In this case, the latency is
connected with the human capacity for processing this type of information.
27.3.2 Computer Vision Applications
These types of applications are characterized by the use of image processing techniques for industrial
automation. There are basically three application types: offline inspection applications, online inspection
applications, and guidance applications (such as robots). In the first case, they are applications of
quality control. Their objective is to know the product’s state in order to determine what further processing
is necessary, or in the case of finished products, its delivery to the customer. A very high working
speed may be required even though there are no hard real-time requirements. For example, quality
inspection of 20–80.m/min of fabric, but in which the faults are stored for report purposes, or, in cases
where it is necessary to stop the machine, there is some tolerance in the order delay. In the second case,
the vision system inspects the product or the process in order to determine what action is necessary. In
other words, the image processing result will have consequences on the production process (e.g., regulation
on the width of rubber bands [SS07]), and therefore, there are some temporal restrictions that must
be adhered to in the transmission and processing of images. In the third application type, the information
extracted from the images is used to guide the management of cutting stands, robots, etc., and in
which case adherence to temporal requirements is even more important.
A common requirement of the three types of computer vision application is the necessity of highquality
images. There has been some work carried out to analyze the limits of image degradation, but
this has been mainly for specific medical applications, and there have been no studies on industrial
environments or into a general theory to gain prior knowledge of this. The target of the computer
vision application determines the image resolution and the transmission times. Typical applications
use 4CIF resolution with transmission between 1 and 60 frames/s. In some cases, more than one camera
© 2011 by Taylor and Francis Group, LLC