With few exceptions, control architecture has changed little over the past 40 years. However, advances in processing power, network technologies and software will enable greater value for end users in the near future by changing the way controllers are implemented and interface to the field.
With few exceptions, the basic architecture of a process (DCS) or discrete (PLC) control system consists of a set of I/O cards logically connected or assigned to a single control processor housed in dedicated hardware. This has been the general state of affairs since the first digital controllers were introduced over 40 years ago. Initial control system incarnations consisted of a card rack in which a local real-time control processor communicated to a set of I/O directly coupled to the same backplane.
As network technologies advanced, systems began to employ architectures in which a single control processor might support several card racks of I/O connected via proprietary, deterministic protocols. While still widely employed today, this predominant architectural approach is effective, but potentially wasteful.
