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# Control system

by Sudipta Saha
Posted: Dec 01, 2020

Here is block diagram representing a closed loop system which explains the use of a sensor and a controller on the basis of the output of a plant. As we can see, both plant and the controller are on the forward direction and sensor transmits the feedback time. The output is then compared with the desired value at the summing point. The difference is sent to the controller which gives a control signal to drive the plant until desired value is achieved.

## Open Loop

Frameworks in which the control activity is unaffected by the yield are known as open-circle control frameworks.

the yield of an open-circle control framework is not figured or bolstered back for correlation with the Input.

The fundamental disadvantage of this control framework is that the controlled variable is touchy to changes in unsettling influence inputs.

## Closed Loop

Control systems with feedback are most commonly known as to as closed-loop control systems.

In a closed-loop control system the actuating error signal, which is the calculated difference between the input signal and the feedback signal, is fed to the controller in order to reduce the error and stabilize the output of the system by bringing it to a desired value.

Closed-loop control reduces system error by always using the feedback control action.

## Linear Systems

Linear systems are those which follow the basic laws of superposition.

This law of superposition states that when two distinct functions are applied at the same time, the response given is the consequence of the two individual control system responses.

This makes it easy to calculate the response to several input of the linear systems by considering a single input at a given time and adding their outputs.

It is this law that builds up complicated solutions to the linear differential equation from simple solutions possible.

## Control using PID

A proportionalâ€“integralâ€“derivative controller (PID controller or three-term controller) is a control loop mechanism employing feedback that is widely used in industrial control systems and a variety of other applications requiring continuously modulated control.

A PID controller continuously calculates an error value as the difference between a desired setpoint (SP) and a measured process variable (PV) and applies a correction based on proportional, integral, and derivative terms (denoted P, I, and D respectively), hence the name.

The three-label (i.e., P, I and D) convenience manages the issues with relentless state and transient responses.

The development in automated advancement have made the control system modified conceivable offers an arrangement of choices for control plot, the same controllers can facilitate the PID Controller's straightforwardness, accommodation, pertinence, and clear value.

## Control using LQR

The theory of optimal control is concerned with operating a dynamic system at minimum cost. The case where the system dynamics are described by a set of linear differential equations and the cost is described by a quadratic function is called the LQ problem. One of the main results in the theory is that the solution is provided by the linearâ€“quadratic regulator (LQR).

linear quadratic controller (LQR) is a procedure in present day control in which utilizes state space way to deal with examine such a system.

## Control using RFID

Radio-frequency Identification (RFID) enables access to control system wirelessly.

The RFID sub-system is made of three components, a RFID tag, a Reader for the tag and a computing device for managing the information database.

The reader picks up the RFID tag signals and this information is processed and authenticated by the computing device.

With the help of RFID, a wide range of applications of automated tracking and wireless communication were achieved.

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### Sudipta Saha

Member since: Nov 28, 2020
Published articles: 1