I worked with Noosa Yoghurt to implement the process control solution discussed in the June article, "Process Automation, Controls Boost Production at Yogurt Plant ." While most of the details on the application are accurately described within the article, this particular application does not use PC-based control. Noosa uses a Rockwell Automation PlantPAx process control system built on a server and thin-client architecture. The actual control resides within a programmable automation controller (not a PC), despite how it's referenced in the article.
In my experience, PC-based control takes the control functions found on a programmable controller, encapsulates them in software and executes program tasks and I/O communications on the PC's processor along with other overhead related to the host operating system.
PLCs and PACs, on the other hand, are more robust and include more control capabilities than those offered through PC-based control. These could include motion control, integrated safety and advanced PID process control. At Noosa, the PAC-based PlantPAx platform provides the ability to add additional I/O, controllers and servers without adversely affecting the base characterized architecture of the system. This flexibility would not be possible within a PC-based system.
Director of Operations, Malisko Engineering Inc.