Control system

Control systems that include some sensing of the results they are trying to achieve are making use of feedback and can adapt to varying circumstances to some extent.

Open-loop control systems do not make use of feedback, and run only in pre-arranged ways.

In such systems, the open-loop control is termed feedforward and serves to further improve reference tracking performance.

Today, most such systems are constructed with microcontrollers or more specialized programmable logic controllers (PLCs).

[6] Logic controllers may respond to switches and sensors and can cause the machinery to start and stop various operations through the use of actuators.

Examples include elevators, washing machines and other systems with interrelated operations.

An automatic sequential control system may trigger a series of mechanical actuators in the correct sequence to perform a task.

For example, various electric and pneumatic transducers may fold and glue a cardboard box, fill it with the product and then seal it in an automatic packaging machine.

PLC software can be written in many different ways – ladder diagrams, SFC (sequential function charts) or statement lists.

When the temperature in the room (PV) goes below the user setting (SP), the heater is switched on.

However, the fuzzy logic paradigm may provide scalability for large control systems where conventional methods become unwieldy or costly to derive.

The centrifugal governor is an early proportional control mechanism.
An electromechanical timer, normally used for open-loop control based purely on a timing sequence, with no feedback from the process
Example of a single industrial control loop; showing continuously modulated control of process flow.
A basic feedback loop
A DCS control room where large screens display plant information. The operators can view and control any part of the process from their computer screens, whilst retaining a plant overview on the larger screens.
A control panel of a hydraulic heat press machine