What is control system? Open loop and Closed loop control system


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What is control system?

Systems that have the ability to regulate and stop a process to get the output as desired is called “Control System” And in general a control system is a collection of electric/electronic equipment, mechanical equipment, or other equipment used to guarantee stability, smooth transition and accuracy of a process.

The input generally comes from the transducer. This transducer is a device that can convert physical quantities into electrical signals. Some examples of transducers include pushbutton, limit switch, thermostat, strain gauges, etc. This transducer sends information about the quantity measured. The picture below shows some examples of input equipment.

The process in this control system can be in the form of a control circuit using electrically arranged control equipment. And there are also those who use control equipment with a renewable or more popular processing system called the PLC (Programmable Logic Controller).

In controls with a programming system that can be updated, the control program is stored in a memory unit and allows or can change the program that has been written before, namely by reprocessing as desired.

The task of the process part is to process data that comes from the input and then, as a result, it is in the form of a response (output).

Open loop system:

Open loop control system is a process in a system where input variables will affect the output produced.

If we look at the diagram block above in the open loop control system where there is no information given to the control equipment that comes from the output equipment, so it cannot be known exactly whether the desired output is in accordance with the wishes or not. Especially if there is interference from outside that can affect output. Therefore this system will have a significant error due to the absence of correction.

Closed-loop Control system:

Closed loop control is a process in which variables that are continuously controlled are censored and then compared with reference quantities.

The variables that are controlled can be in the form of measurements such as measurements of temperature, humidity, mechanical position, rotation speed, etc., then the results of the measurements are feedback to the comparator.

This comparator can be mechanical, electrical/electronic, or pneumatic equipment. In this comparison tool between the reference quantity and the sensor signal originating from the controlled variable compared, and as a result is an error signal. This error signal results can be positive or negative, mathematically this error signal is shown in the equation below.

Error = price of controlled variable measurement - set point (reference)

The control equipment blocks can be equipment that can work mechanically, electrically/electronically, or pneumatically, which in this block receives an error signal and produces an output signal which is then given to the process part to correct errors until the results/products actually match what you want or the error is zero. Thus the mechanism of the closed-loop control system and the mechanism works continuously.