Automating Manufacturing Systems - Process Control and ...

plc software - 32.12
2. A basic model of the system is developed in terms of the inputs and outputs.
This might include items such as when sensor changes are expected, what
effects actuators should have, and expected operator inputs.
3. A system simulator is constructed with some combination of specialized software
and hardware.
4. The system is verified for the expect operation of the system.
5. The system is then used for testing software and verifying the operation.
A detailed description of simulator usage is available [Kinner, 1992].
32.5 DOCUMENTATION
Poor documentation is a common complaint lodged against control system designers.
Good documentation is developed as a project progresses. Many engineers will leave
the documentation to the end of a project as an afterthought. But, by that point many of the
details have been forgotten. So, it takes longer to recall the details of the work, and the
report is always lacking.
A set of PLC design forms are given in Figure 32.6 to Figure 32.12. These can be
used before, during and after a controls project. These forms can then be kept in design or
maintenance offices so that others can get easy access and make updates at the controller
is changed. Figure 32.6 shows a design cover page. This should be completed with information
such as a unique project name, contact person, and controller type. The list of
changes below help to track design, redesign and maintenance that has been done to the
machine. This cover sheet acts as a quick overview on the history of the machine. Figure
32.7 to Figure 32.9 show sheets that allow free form planning of the design. Figure 32.10
shows a sheet for planning the input and output memory locations. Figure 32.11 shows a
sheet for planning internal memory locations, and finally Figure 32.12 shows a sheet for
planning the ladder logic. The sheets should be used in the order they are given, but they
do not all need to be used. When the system has been built and tested, a copy of the working
ladder logic should be attached to the end of the bundle of pages.