The next wave of control system architecture is already emerging. As processor power continues to grow and cost continues to decline, how do we leverage that emerging capability? Through an understanding of control system architecture.
Industrial control systems are really arrangements of processors whose internal and external structure is designed to solve a unique equipment or process problem. PLCs are architected in hardware and software to solve many different types of equipment needs, both in processes and discrete machinery. Presenting a bill of material to a customer who may be unfamiliar with the hardware does nothing to convey that the proposal is a good solution to the problem. It’s just a price.
Taking the same bill of material and creating a Hardware Architecture Diagram is something different. It takes the hardware and shows something about the functionality and interrelationship of the hardware. This provides a visual basis for how the proposed equipment will solve the customer’s problem. Two totally different scenarios.
Control system architecture can be applied to anything. It is the process of abstracting the process or control application. What it is that needs to be done and the details of quantity, quality and many intangibles that make up the required performance. It is also the process of finding the best, most economical way to perform that task.
System architecture can be used at many different layers. The internal organization of the computer, for example, involves an architecture combining a processor, memory, video control, and I/O control with an operating system that manages the system’s resources. Most of these exist in controllers used in industry. The operating system and internal hardware are layers below the user programming, and so are generally disregarded until a defect or anomaly is found. The level of complexity of today’s control systems makes exhaustive testing prohibitively expensive. In addition, when controller internal operations are broken down to extreme detail, the actual execution may not be quite as expected due to the fact that the programmer who wrote the firmware was a computer science major, not a subject matter expert in the specifics a particular control problem. Notwithstanding the challenge of internal complexity, there are billions of dollars of equipment out there that operate 24/7 with incredible reliability.
What a deal!