# What is Feedback control: Definition and 17 Discussions

Feedback occurs when outputs of a system are routed back as inputs as part of a chain of cause-and-effect that forms a circuit or loop. The system can then be said to feed back into itself. The notion of cause-and-effect has to be handled carefully when applied to feedback systems:

Simple causal reasoning about a feedback system is difficult because the first system influences the second and second system influences the first, leading to a circular argument. This makes reasoning based upon cause and effect tricky, and it is necessary to analyze the system as a whole.

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1. ### Stability test for Feedback Amplifiers

Does the following simple test deduced from Nyquist criterion also apply to positive feedback or it needs to be modified? If magnitude of loop gain i.e. |T (jω)| > 1 at the frequency where phase(T (jω))= −180◦, then the amplifier is unstable. Reference: Analysis and Design of Analog...
2. ### Engineering Can I use root locus when the input is the negative feedback?

I have used root locus before but my confusion now is that the input is the negative feedback. Usually when I have negative feedback I consider the the error between the input (ideal) signal and the observed signal. Also, in this case what is the tranfer function since u = -k*y, and what does...
3. ### Understanding Feedback Control in Klystrons

I was puzzled when I thought about what happens to a klystron when it's output is fed back to it's input. This doesn't apply to magnetrons because they cannot be driven like amplifiers so they are oscillators by definition. I've dealt with audio amplifiers mostly and there almost always...
4. ### Does the transfer function exist for an unforced system?

Homework Statement c is the coefficient of damping, k is the spring constant, and m is the mass. if the cart is displaced from rest by distance X_0 and released at t=0 with initial velocity v_0=1.Homework EquationsThe Attempt at a Solution Ok this might be a stupid question because I wasn't...
5. ### Calculate the additive RPM required for tension control

In a web tension control system, where feed forward is to be used. A tension set point is desired let's say 20lbs, and a load cell system provides feed back. There will be dead weight on the load cell as the material with no pull sits on top of the load cell system. [Obviously I will need to...
6. ### Why is the output in the middle of the block diagram?

(mentor note: not really a homework as the OP seeks understanding from an article) 1. Homework Statement I saw this on https://www.electronicshub.org/open-loop-system/, I thought the dry clothes should be the output, and heating the cloth should be the plant/process, I am so confused...
7. ### Force Feedback control - Capstone project

I'm attempting to design a force feedback system for my senior capstone project. It will consist of a single lever that is free to move along a single axis. Imagine a video game joystick, but one that only moves forward and back. I need to mimic a given force profile along the stroke of the...
8. ### Engineering Feedback Control: Modeling Mechanical System with Circuit

Homework Statement Find the transfer function for the following mechanical system with force input fin and output x2. Homework EquationsThe Attempt at a Solution The reason I left the equations blank is because I'm not sure how to appropriately model this scenario. I've seen two different...
9. ### Feedback control via ODE variable coefficients?

If one has a simple variable coefficient process like y'(t) = r(t)*y(t), is there a way to control it to a set point by feedback hitting the variable coefficients in r(t)? I am interested in feedback control of population processes. y'(t) = r*y(t) is simple proportional growth with a...
10. ### Feedback Control Systems as an Elective

Hey everyone, I am an undergraduate mechanical engineering major considering a EE feedback controls course as an upper division elective. I have taken ME Control Systems and am also the Lab Instructor for it this semester. I am familiar with signals, filters, sensors, controllers etc. My...
11. ### Mathematical modeling of a feedback control system

My system is a compound pendulum hinged at some distance from one end and have a propeller mounted dc motor at the other end. I wish to position the pendulum with the help of motor propeller system. I tried but i am unable to get a mathematical model for it. I am getting a non linear model...
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### Routh-Hurwitz Stability Criterion: Solving Feedback Control Systems Homework

Homework Statement http://img24.imageshack.us/img24/9028/72841137.jpg Homework Equations Routh-Hurwitz Stability Criterion The Attempt at a Solution For first question, you just write the Routh Array, make sure that the first row is all positive and you get Kmax = 1. Simple enough How...
13. ### Transfer Function & Unity Negative Feedback Control System

Hi there. I'm wondering if anyone can help. I've got a few past papers I'm working on at the moment and there are a few questions I don't even know where to start with. Here's one: a. Write down the transfer function for a time delay and then evaluate its corresponding frequency response...
14. ### Good textbooks for feedback control systems

Hi guys, i am taking a module on feedback control systems this semester and i was wondering if anyone has any good recommendations of textbooks. Thanks guys. Marcus.
15. ### I am interested in building a rocket with feedback control system

I am interested in building a rocket with feedback control system... so I have been interested in model rocketry lately and I was wondering how feasible it would be to design and build a model rocket for my senior project complete with a control system to ensure it flies straight up. I was...
16. ### Feedback control for a metabolic pathway

I'm having a problem setting up a certain differential equation which I need to solve a problem. Here's the problem: I'm given a feedback control for a certain metabolic pathway. I've attached a picture of the network below. Now what I can't figure out is how to write the differential...
17. ### How Does Negative Feedback Control Work in the Adrenal Gland?

How does it work for the 'Adrenal Gland'? I cannot find this information anywhere and I need it as soon as possible, thanks. Thank you.