How did analogue and digital computers make modern control systems more complex?

Analogue and digital computers have significantly increased the complexity and capability of modern control systems by moving beyond simple, single-loop operations toward highly integrated, automated processes.1

Analogue Computers

Conventional analogue instruments typically handle single-loop systems, where one input signal results in one output correction. While analogue-type computers allow for the consideration of multiple variables simultaneously, they are highly specific in their application and are not commonly used for broad industrial control.1

Digital Computers

The integration of digital computers transformed control systems in three primary ways:

• Supervisory Control: Computers act in a secondary capacity to "trim" plant operations, such as adjusting set points to optimize production or lower costs.1
• Direct Digital Control: A single digital computer replaces groups of analogue controllers, utilizing its superior computational power to execute advanced control techniques.1
• Hierarchy Control: This represents the most complex application, integrating plant operations from top-level management decisions down to individual valves.1

Unlike conventional hardware, digital systems are easily reprogrammable, allowing for new tasks without physical equipment changes. Furthermore, the microprocessor has enabled sophisticated feedback control in robots and manufacturing, allowing systems to compensate for variations like tool wear in real time.12