Basics of Process Control
All manufacturing systems can be broken down into a series of steps or processes, whether it is making widgets, building a car, or running a Power Station. For effective management of a manufacturing process, control of heat, valves, mechanical robots and production lines is needed. The automation and control of these processes requires suitable hardware and software.
However, this is a simplistic overview of process control. By integrating devices and systems that will allow the process to be controlled, greater efficiencies can be achieved and long term trends can be monitored. If the goal of controlling a process is to maintain or improve product quality while improving performance and management, the system must be able to monitor parameters and make measurements on product and materials as they move through the process.
All the time, the process control system will monitor and measure the required parameters, make decisions that maintain the overall quality, reduce the amount of rework and reject non conforming products before it moves to the next step in the process. While the process control system is doing this in real-time, it can be recording all these measurements and actions to give your Quality Assurance system a history of conformance, and the management team an overall view of the system while allowing them to dig into the data if they need to.
This can be achieved with PC based or distributed I/O systems and suitable software such as a Supervisory Control and Data Acquisition System (SCADA) package running Modbus or Open Process Control (OPC) protocols on reliable communication backbones such as redundant Ethernet.
Because of this, expensive and inflexible Programmable Logic Controllers (PLCs) are being replaced. New, smaller controllers are available that can replace all but the most complicated system. These range from a single function device such as a PID controller to the powerful Programmable Automation Controller (PAC) which uses modular I/O with an on-board operating system and a programming environment familiar to PLC users.
The additional feature of these controllers are their open protocols such as Modbus, Profibus, or ASCII which allows them to communicate with the computer systems providing the monitoring, logging and reporting of the process under control for the management.
Further flexibility can be added with wireless systems such as Wi Fi or cellular communications on the mobile phone network.
If you have existing PLCs or a Distributed Control System (DCS), you can still take advantage of this new family of hardware and software. Utilising new smaller and simpler hardware and software, systems can be easily expanded by using Gateway devices to connect to an existing network, add new features to a PLC without changing its program, or add new data to an existing database without changing the existing control software.