Here are a couple of white papers that we have authored.
Accutrol Machine Control Using Coupled PLC
This first white paper describes performing machine control using a hybrid approach, using a computer for user interface, file I/O, instrument communication, and plant connectivity, and using a PLC for low-level discrete and analog I/O. This approach allows development of a system that is fault tolerant and flexible.
Coupled Data Logger and Analyzer
The second white paper describes a data logger that performs system control and data analysis while logging data.