Control system
Introduction
A control system is a device, or set of devices, that manages, commands, directs or regulates the behavior of other devices or systems. Industrial control systems are used in industrial production for controlling equipment or machines.
There are two common types of control systems, with many variations and combinations: open-loop control systems and closed-loop control systemsControl System Types.
Open-loop control systems
Open-loop control systems (also known as non-feedback control systems) are systems where the control action is independent of the "process output" (or "controlled process variable"). A good example of this is a central heating boiler controlled only by a timer, regardless of how cold it is outside or inside the building.
Closed-loop control systems
Closed-loop control systems (also known as feedback control systems) are systems where the control action is somehow dependent on the process output. In the case of the boiler analogy, this could be an additional thermostat that switches the heating off when a certain temperature is reached and switches it back on again when the temperature drops too far.
Control theory
Control theory is an interdisciplinary branch of engineering and mathematics that deals with the behavior of dynamical systems with inputs. The external input of a system is called the reference. When one or more output variables of a system need to follow a certain reference over time, a controller manipulates the inputs to a system to obtain the desired effect on the output of the system.
Control engineering
Control engineering is the engineering discipline that applies control theory to design systems with desired behaviors. The practice uses sensors to measure the output performance of the device being controlled and those measurements can be used to give feedback to the input actuators that can make corrections toward desired performance.
Control systems in different fields
Control systems are used in many different fields, including:
- Chemical engineering
- Electrical engineering
- Mechanical engineering
- Aerospace engineering
- Environmental engineering
- Civil engineering
- Biomedical engineering