Why Negative Feedback is preferred in the Control System?

Why Negative Feedback is preferred in the Control System?
by

1 Answer

Answer :

The role of Feedback in control system is to take the sampled output back to the input and compare output signal with input signal for error ( deviation from the desired result).
Negative Feedback results in the better stability of the system and rejects any disturbance signals and is less sensitive to the parameter variations. Hence in control systems negative feedback is considered.
by

Related questions

What are the Characteristics of Negative Feedback?

Description : What are the Characteristics of Negative Feedback?

Last Answer : Negative Feedback in a Control System has following Characteristics Reduction in the gain at the expense of better stability of the system Rejection of disturbance signals in the system Low Sensitivity to parameter variations Accuracy in tracking the steady state value

What are the basic components of the feedback control system?

Description : What are the basic components of the feedback control system?

Last Answer : Basic components of the feedback control system are process system (open loop system), feedback path element, error detector, and controller.

What is a feedback in Control System?

Description : What is a feedback in Control System?

Last Answer : The Feedback in Control System in one in which the output is sampled and proportional signal is fed back to the input for automatic correction of the error ( any change in desired output) for futher processing to get back the desired output.

What is the effect of positive feedback on stability of the system?

Description : What is the effect of positive feedback on stability of the system?

Last Answer : Positive feedback is not used generally in the control system because it increases the error signal and drives the system to instability. But positive feedbacks are used in minor loop control systems to amplify certain internal signals and parameters

What is Feedback Compensation?

Description : What is Feedback Compensation?

Last Answer : In Feedback compensation method the compensation network is introduced in the feedback path of a control system.

Frequency Domain Analysis in Control System

Description : Frequency Domain Analysis in Control System

Last Answer : Frequency Response: The Frequency Response of the system is the steady state response of the system obtained as the output when a sinusoidal input signal is given to the system. For determining the ... of the system, adjust the gain of the control system and helps in designing the control system.

What is Time response of the control system?

Description : What is Time response of the control system?

Last Answer : Time response of the control system is defined as the output of the closed loop system as a function of time. Time response of the system can be obtained by solving the differential equations governing the system or time response of the system can also be obtained by transfer function of the system.

What is mathematical model of a control system?

Description : What is mathematical model of a control system?

Last Answer : Control system is a collection of physical elements connected together to serve an objective. The output and input relations of various physical system are governed by differential equations. ... the system can be studied by solving the differential equations for various input conditions.

What is Control System?

Description : What is Control System?

Last Answer : In a System the output and inputs are interrelated in such a manner that the output quantity or variable is controlled by input quantity, then such a system is called Control System. The ... is called controlled variable or response and the input quantity is called command signal or excitation.

Closed loop and Open loop Control System Advantages and Disadvantages

Description : Closed loop and Open loop Control System Advantages and Disadvantages

Last Answer : Open Loop Control System: Control System in which output quantity has no effect on the input quantity is called Open Loop Control System. Open Loop Control System has no facility to correct automatically the ... in the closed loop system and more care is needed to design a stable closed loop system

Distributed Control System (DCS) in Power Plant

Description : Distributed Control System (DCS) in Power Plant

Last Answer : Usage of Single Computer for control of all the process variables of plant would result in the loss of control action in the plant if failure occurs to the master single computer. Also, ... control loop This type of distribution results in increase in speed and reliability of the control system.

What are different types of Control Systems?

Description : What are different types of Control Systems?

Last Answer : Two major types of Control Systems are 1) Open loop Control System 2) Closed Loop Control Systems Open loop Control Systems: The Open loop Control System is one in which the Output Quantity has ... quantity to the input quantity for the correction so as to maintain the desired output of the system.

PI Controllers in Process System

Description : PI Controllers in Process System

Last Answer : PI controllers are used in many industrial control applications. The main purpose of using Proportional and Integral (PI) in process system is to improve the steady state accuracy of the ... requires higher values of the proportional and integral gains compared to gains required in PI controllers

What is Zero of the system?

Description : What is Zero of the system?

Last Answer : Zero of a function F(s) is a value at which the function F(s) becomes zero, where F(s) is a function of complex variable s.

What is Pole of the system?

Description : What is Pole of the system?

Last Answer : Pole of a function F(s) is the value at which the function F(s) becomes infinite, where F(s) is a function of the complex variable s.

How Time response of the system is divided?

Description : How Time response of the system is divided?

Last Answer : Time response of the system consists of two parts: 1.Transient state response 2. Steady state response. Transient response of the system explains about the response of the system when the input ... other. Steady state response of the system shows the response as the time t, approaches infinity

What is Order of the system?

Description : What is Order of the system?

Last Answer : Order of the system is defined as the order of the differential equation governing the system. Order of the system can be determined from the transfer function of the system. Also the order of ... function. For nth order system for a particular transfer function contains 'n' number of poles.

Explain Mechanical Translational System?

Description : Explain Mechanical Translational System?

Last Answer : Model of mechanical translational system can be obtained by using three basic elements Mass, Spring and Dash-pot. Weight the mechanical system is represented by mass and is assumed to be ... represented by the spring Friction existing in a mechanical system can be represented by dash-pot.

What is Time Invariant system?

Description : What is Time Invariant system?

Last Answer : Time Invariant System is one in which the input and output characteristics of the system does not change with time.

What is a System?

Description : What is a System?

Last Answer : When a number of elements or components are connected in a sequence to perform a specific function, the group of elements that all constitute a System

Advantages of Frequency Domain Analysis

Description : Advantages of Frequency Domain Analysis

Last Answer : Advantages of Frequency Domain Analysis Frequency Response Analysis: In frequency response analysis the input to the control system is fed with a sinusoidal signal with different frequencies. The output ... system Frequency domain analysis can also be carried out for the non linear control systems.

What are Test signals and their significance?

Description : What are Test signals and their significance?

Last Answer : The knowledge of the input signal is required to predict the response of the system. In most of the systems input signals are not known ahead of the time and it is also difficult to ... the control system. The commonly used test signals are impulse, ramp, step signals and sinusoidal signals.

What are the basic properties of Signal Flow Graph?

Description : What are the basic properties of Signal Flow Graph?

Last Answer : The basic properties of the signal flow graph are: Signal Flow Graphs are applicable to linear systems It consists of nodes and branches. A node is a point representing a variable or signal. A ... the gain of the branch The algebraic equations must be in the form of cause and effect relationship

What is S-domain and its significance?

Description : What is S-domain and its significance?

Last Answer : By taking Laplace transform for differential equation in the time domain equations in S-domain can be obtained. L{F(t)}=F(s) S domain is used for solving the time domain differential equations easily by applying the Laplace for the differential equations.

What is Signal Flow Graph?

Description : What is Signal Flow Graph?

Last Answer : A Signal Flow Graph is a diagram that represents a set of simultaneous linear algebraic equations. By taking Laplace transform the time domain differential equations governing a control system can be ... s-domain. The signal Flow graph of the system can be constructed using these equations.

Where Servomechanism is used?

Description : Where Servomechanism is used?

Last Answer : Servomechanism is used in control system where the output is pertained to vary the mechanical position of a device. Servo Mechanism is widely used in Governor value position control mechanism ... controls using power Thyristors. Servomechanism is also widely used in the robotic hand movements.

What is the basic rule for Block Diagram Reduction Technique?

Description : What is the basic rule for Block Diagram Reduction Technique?

Last Answer : The rules of the Block Diagram reduction Techniques are designed in such a manner that any modifications made in the diagram will not alter the input and output relation of the system

Define Transfer Function?

Description : Define Transfer Function?

Last Answer : Transfer Function of a control system is defined as: i) Ratio of Laplace transform of Output to the Laplace transform of the Input with zero initial conditions ii) Transfer function is defined as the Laplace transform of Impulse response of the system with zero initial conditions

Phase Margin?

Description : Phase Margin?

Last Answer : Answer: The phase margin is the amount of additional phase lag at the gain cross over frequency required to bring the system to the verge of instability.

What is Gain Margin?

Description : What is Gain Margin?

Last Answer : Answer: The Gain Margin is defined as the reciprocal of the magnitude of open loop transfer function at phase cross over frequency. The gain margin indicates the amount by which the gain of the system can be increased without affecting the stability of the system

What is Phase cross over frequency?

Description : What is Phase cross over frequency?

Last Answer : Answer: The frequency at which the phase of the open loop transfer function is 180o is called the phase cross over frequency.

What is Cut-off rate?

Description : What is Cut-off rate?

Last Answer : Answer: The slope of the log-magnitude curve near the cut-off frequency is called the cut-off rate. The cut-off rate indicates the ability of the system to distinguish between the signal and the noise

What is Resonant Frequency?

Description : What is Resonant Frequency?

Last Answer : Answer: The frequency at which resonant peak occurs is called the resonant frequency. Resonance frequency explains about the speed of the transient response.

What is Resonant peak?

Description : What is Resonant peak?

Last Answer : Answer: Resonant peak is defined as the maximum value of the closed loop transfer function.A large resonant peak corresponds to large overshoot in the transient respose

Why derivative controller is not used in control system?

Description : Why derivative controller is not used in control system?

Last Answer : The derivative controller produces a control action based on rare of change of error signal and it does not produce corrective measures for any constant error. Hence derivative controller is not used in control system

Name the test signals used in control system

Description : Name the test signals used in control system

Last Answer : The commonly used test input signals in control system are impulse step ramp acceleration and sinusoidal signals.

What are the major types of control system?

Description : What are the major types of control system?

Last Answer : i. open loop system ii closed loop system

Where is on off control used ?

Description : Where is on off control used ?

Last Answer : On off control is used when ١. Precise control is not needed. ٢. Processes that have sufficient capacity to allow the final operator to keep up with the measurement cycle. ٣. It is mainly used in refrigeration and are conditioning systems. 

What is difference gap control ?

Description : What is difference gap control ? 

Last Answer : Differential gap control is similar to on off control except that a band or gap exists around the control point. Use: In industry differential gap control is often found in non critical level control ... be closed fully. Similarly when it exceeds the lower gap it will open or close fully.  

Why derivative controller is not used in control systems.

Description : Why derivative controller is not used in control systems.

Last Answer : The derivative controller produces a control action based on the rate of change of error signal and it does not produce corrective measures for any constant error.

What are the effects of adding a zero to a system?

Description : What are the effects of adding a zero to a system?

Last Answer : Adding a zero to a system increases peak overshoot appreciably.

What is an order of a system?

Description : What is an order of a system?

Last Answer : The order of a system is the order of the differential equation governing the system. The order of the system can be obtained from the transfer function of the given system.

What is the effect of PI controller on the system performance?

Description : What is the effect of PI controller on the system performance?

Last Answer : The PI controller increases the order of the system by one, which results in reducing the steady state error .But the system becomes less stable than the original system.

What is the effect of PD controller on system performance?

Description : What is the effect of PD controller on system performance?

Last Answer : The effect of PD controller is to increase the damping ratio of the system and so the peak overshoot is reduced.

What are the effects of adding a zero to a system?

Description : What are the effects of adding a zero to a system?

Last Answer : Adding a zero to a system results in pronounced early peak to system response thereby the peak overshoot increases appreciably.

Write the analogous electrical elements in force current analogy for the elements of mechanical translational system.

Description : Write the analogous electrical elements in force current analogy for the elements of mechanical translational system.

Last Answer : Force-current I Velocity v-voltage v Displacement x-flux_ Frictional coeff B-conductance 1/R Mass M- capacitance C Stiffness K-Inverse of inductance 1/L

Write the analogous electrical elements in force voltage analogy for the elements of mechanical translational system.

Description : Write the analogous electrical elements in force voltage analogy for the elements of mechanical translational system.

Last Answer : Force-voltage e Velocity v-current i Displacement x-charge q Frictional coeff B-Resistance R Mass M- Inductance L Stiffness K-Inverse of capacitance 1/C

Name two types of electrical analogous for mechanical system.

Description : Name two types of electrical analogous for mechanical system.

Last Answer : The two types of analogies for the mechanical system are Force voltage and force current analogy

What are the basic elements used for modeling mechanical rotational system?

Description : What are the basic elements used for modeling mechanical rotational system?

Last Answer : Moment of inertia J, dashpot with rotational frictional coefficient B and Rotations spring with stiffness K

What are the basic elements used for modeling mechanical translational system

Description : What are the basic elements used for modeling mechanical translational system

Last Answer : Mass, spring and dashpot