Interview Questions


  1. Define System.

A system is a combination or an arrangement of different physical components which act together as an entire unit to achieve certain objective.

  1. Define Control system.

To control means to regulate, to direct or to command. Hence a control system is an arrangement of different physical elements connected in such a manner so as to regulate, direct or command itself or some other system.

  1. Define Plant.

The portion of a system which is to be controlled or regulated is called the plant or the process.

  1. Define Controller.

The element of the system itself or external to the system which controls the plant or the process is called controller.

  1. Define Input.

It is an applied signal or an excitation signal applied to a control system from an external energy source in order to produce a specified output.

  1. Define Output.

It is the particular signal of interest or the actual response obtained from a control system when input is applied to it.

  1. Define disturbance.

Disturbance is a signal which tends to adversely affect the value of the output of a system.

  1. Define internal disturbance.

If such a disturbance is generated within the system itself, it is an internal disturbance.

  1. Define external disturbance.

The disturbance generated outside the system acting as an input to the system in addition to its normal input, affecting the output adversely is an external disturbance.

  1. Write any four major classification of control system.

Open loop and closed loop control system.

Time varying and time-invariant system.

Linear and nonlinear system.

Lumped parameter and distributed parameter control system. 

  1. What is mean by Principle of superposition?

Principle of superposition means the response to several inputs can be obtained by considering one input at a system and the algebraically adding the individual results.

  1. What is mean by Deterministic control system?

A control system is said to be deterministic when its response to input as well as behavior to external disturbance is predictable and repeatable.

  1. Write short notes about SISO and MIMO.

A system having only one input and one output is called single input and single output system. Some systems may have multiple input and multiple outputs, these are called multiple input and multiple output systems.

  1. Define Open loop system.

A system in which output is dependent on input but controlling action is totally independent of the output or changes in input of the system, is called an open loop system.

  1. Define closed loop system.

A system in which controlling action or input is somehow dependent on the output or changes in output is called closed loop system.

  1. Write any four advantages of open loop system.

Such systems are simple in construction.

Very much convenient when output is difficult to measure.

Such systems are easy when maintenance point is view.

Such systems are economical.

17.Write any four disadvantages of open loop system.

Such systems are inaccurate and unreliable because accuracy of such system is totally dependent on the accurate precalibration of the controller.

Such systems give inaccurate results if there are variations in the external environment.

Similarly they cannot sense internal disturbances in the system, after the controller stage.

To maintain the quality and accuracy, recalibration of the controller is necessary, time to Time.

18.Give any four real time application of open loop system.

Sprinkler used to water a lawn.

Stepper motor positioning system.



What is cascade control loop? Advantages of the cascade control loop 

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