Understanding Systems and Control

Systems can be either physical, like electrical or mechanical systems, or conceptual, like economic or social systems.
A control system is a device, or set of devices, that manages, commands, directs, or regulates the behaviour of other devices or systems to achieve a desired outcome.
Control systems can be classified into two types: open-loop control systems (non-feedback systems) and closed-loop control systems (feedback systems).
Open-loop control systems are those in which the output has no influence or effect on the control action of the input signal.
Closed-loop control systems are those in which the control action from the controller is dependent on the desired output. The actual system output is fed back to the input for comparison with the desired output (reference point), and the difference between actual and desired outputs is worked upon by the controller to drive the system in the desired manner.

Key Components of a Control System

The major components include process system (also called the plant), controller, actuator and sensor.
Process system / Plant: This component is responsible for the operation to be controlled. For instance, the temperature of a furnace.
Controller: Regulates the operation of the system by processing the error signal from the reference point.
Actuator: The component that takes the signal from the controller and executes the physical motion.
Sensor: Measures the current state of the system and sends the data back to the controller.

Stability: An important characteristic of a control system, indicating the ability of a system to return to its steady state after a disturbance.
Transient Response: The control system’s response from its stable state to another stable state. It should be as small and quick as possible.
Steady State Response: The behaviour of the system after it has reached equilibrium following a change in the system such as a step input. The steady state response should be accurate.
Frequency Response: The magnitude and phase changes in a control system in response to a frequency range of input signals.

Microcontrollers: Microcontrollers are a type of microprocessor optimised for control applications. They are designed for small, low-cost control applications.
Programmable Logic Controllers (PLCs): These are digital computers used for automation of typically industrial electro-mechanical processes.
Digital Signal Processors (DSPs): These are specialised microprocessors with an architecture optimised for the processing of digitised real-time signals.
FPGAs (Field Programmable Gate Arrays): A FPGA is an integrated circuit designed to be configured by a designer or a customer after manufacturing – hence the name “field-programmable”.