Control system is a system of devices which is used to manage, commands, directs and regulates the behaviour of the other devices to accomplish a desired level. In other words, it is a system which controls other device system to achieve a desired result. Control systems are present almost everywhere. For eg. Control system is used in a single home heating controller using a thermostat as a controller for domestic boiler to a large scale industrial system.
Aricle written By : Pallavi Wankhede
There are two main types of control system: Open loop control system and closed loop control system.
2. Closed Loop Control System
For an instance, an air conditioner is used for cooling the room. Initially, the actual temperature of the room is measured once you switch on the conditioner. During regulating a specific temperature as per requirement, air conditioner uses a thermostat which gives feedback to the control system.
Other than these two control systems, the types may vary depending on the application requirement. These are as follow:
3. Feedback Control System : In this type of control system, sensors, control algorithms, and actuators are involved to regulate the process variable at a setpoint. Feedback Control System tries to achieve a desired result with the help of feedback and can change the output at some extent when conditions vary. The closed loop control systems are the example of feedback control system. (see closed loop control system block diagram fig. 2)
4. Feedforward Control System : In this type of control system
Figure 3 : Feed Forward Control loop
5. Linear and Nonlinear Control System: Linear Control System use negative feedback to produce a control signal to maintain the controlled Process Variable (PV) at the desired Setpoint (SP). It also follows homogeneity and additivity. While nonlinear control system does not follow homogeneity.
6. Continuous time and discrete time control system: This type of control system is based on the type of signal used. In continuous time control system, all the signals are continuous in time. In discrete time control system, one or more signals are discrete time signals.
7. SISO and MIMO Control System: Based on the number of input and output, control system can be classified as SISO (Single Input Single Output) and MIMO (Multiple Input Multiple Output). SISO stands for Single Input and Single Output, the name SISO itself suggest that control system has one input and one output. On the other hand, MIMO stands for Multiple Inputs and Multiple Outputs. MIMO has more than one input and one output.