15 votes
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Why do we use step response?

Step response and transfer function are interchangeable via Laplace transform (step response -> differentiate to get impulse response -> laplace -> transfer function), but you can't run a Laplace ...
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10 votes
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Integral only control (as opposed to PI or PID)

Another way to look at your question is when would you use PI control with the P term 0. The answer is basically "Whenever you think you can get away with it.". This main risk with only integral ...
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8 votes
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I'm confused a bit on basic control stuff for a PID controller

Your control is quite good despite if you feel in other way. I do think that a P-control with feed forward LUT (Look Up Table) would solve 98% of your need. Try this way: For each temperature ...
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7 votes

Why do we use step response?

An impulse, i.e. hit it with a hammer, is not very friendly, particularly in systems that have mechanical bits and pieces. A perfect impulse cannot be generated, so you have to tailor the pulse ...
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6 votes

Are oscillators always non linear?

A practical oscillator has to be designed taking into account component tolerances. In your example the ratio of RG to RF needs to be such that the gain round the loop is unity. Because of the ...
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6 votes
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What is the practical advantage of root locus method in control system engineering?

You might find it interesting to know that the PID controller was around long before root locus. Root locus was so popular when it was first discovered because it was one of the first methods that ...
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5 votes
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Intuitively, why does gain margin and phase margin infer instability in feedback system?

why increasing the "gain" of your system will cause instability If you have a servo control mechanism and you set a demand, the servo should rotate (or move) to the position demanded and all is good. ...
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5 votes
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Steady-state Error Definition

where E(s) is the error (and also the signal carried forward directly from the summing node), R(s) input and C(s) output. The error is "demand" minus "output" and the output and the demand are ...
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5 votes

I'm confused a bit on basic control stuff for a PID controller

The graph with the P-control response looks quite decent already. Based on the P-control response, you just need a little integral action to take out the DC error. (unless you also want to boost the ...
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4 votes

Are oscillators always non linear?

Usually clipping limits the amplitude, but if you want to build a low-distortion oscillator, then every component must stay in its linear range. Clipping is not allowed. Which means we have a problem: ...
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4 votes

Are oscillators always non linear?

Any oscillator needs that little bit extra gain to start. Oscillations build cycle after cycle. Your example circuit is powered with a +5v supply. Oscillation peak-to-peak amplitude certainly cannot ...
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4 votes
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Closed loop transfer function problem

It's eminently possible for an open loop system to have exactly the same TF as a closed loop system: \$ \frac {1}{1+s}\$ could be the TF of a simple series RC circuit with R=1, C=1, or it could be a ...
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4 votes
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How to find system overshoot (Mp) from Bode diagram

The question assumes there is one damping factor i.e. the transfer function is dominated by a 2nd order system. In practice there could be several interacting 2nd order systems so care has to be taken ...
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4 votes

Difference between a controller (e.g PD) and a compensator(e.g Lead)?

In simply words: Regulator (controller) is a device that controls the object in closed loop on the basis of difference (error of regulation) between measurements of object's output and external ...
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4 votes

How to calculate roots using root locus method?

You could use Newton's method. Yeah I know, it's not the "root locus method", but hey, it works. Let \$F(s)=3s^4+10s^3+21s^2+24s+30\$ Clean it up by dividing everything by 3 so our largest s is ...
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4 votes
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How can I calculate gain margin in this transfer function and the constant K?

Working in arctan is quite difficult. Instead, use complex notation, and this will give the answer, \$\omega =\large \frac{\sqrt{5}}{2}\$ rad/sec. ... In response to the OP's comment ... Thus, ignore ...
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3 votes
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Why can't a first-order block have an oscillatory step response?

It's apparent that a first-order block cannot have an oscillatory step response. How come? A first order system will reach a state of equilibrium in the fullness of time and the energy ...
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3 votes
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Transfer function of a digital phase frequency detector

The pfd (with charge pump) generates current pulses of fixed amplitude ICPICP like it is described for example here. For small phase deviations the length of these current pulses is proportional to ...
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3 votes
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Bode Plots - Absolute Value of Complex Function in Magnitude calculation

You should do some revision on complex numbers, e.g. the magnitude of a complex number, \$(a+jb)\$, is \$\sqrt{ (a^2+b^2)}\$ and not \$\sqrt{(a+jb)^2}\$, which is meaningless in this context - you ...
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3 votes

Integral only control (as opposed to PI or PID)

What are the benefits of I control over PI control, and when should it be used / not be used? Just as with any other forms of control, the answer is simple - you should use the form that best suits ...
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3 votes

Effect of RHP zeros on stability

To ensure that any feedback system is stable, the loop gain needs to have a phase difference less than 180 degrees when its magnitude is unity, in other words it needs to ave sufficient phase margin. ...
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2 votes

PID Control: Controller of the type \$\dfrac{1}{s+k}\$

One reason for using an integrator in the forward path of a closed-loop system (if integration is not present, inherently) is that it gives unity 'DC gain' or 'steady-state gain'. That is, the ...
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2 votes
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PID Control: Controller of the type \$\dfrac{1}{s+k}\$

Expanding on Ben's answer, let's presume we construct a PI with the integral replaced with a single pole low-pass filter. The TF for our controller is $$C(s) = K_p + \frac{K_f}{s+k} = \frac{K_ps+kK_p+...
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2 votes

PID Control: Controller of the type \$\dfrac{1}{s+k}\$

"Single-pole lowpass filter", typically. The difference is that the lowpass filter has finite gain (1/k) at low frequencies, while the integrator theoretically has infinite gain at DC.
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2 votes

Object tracking project

(Answering this despite broad scope because this is clearly a student capstone project... I'm treating this as a question about how a university student should approach capstone project management.) ...
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2 votes

Intuitively, why does gain margin and phase margin infer instability in feedback system?

The key of these stability questions is Nyquist´s stability criterion (which - in this case - can be expressed also with Barkhausens`s oscillation condition): LOOP GAIN OF UNITY. That means: A ...
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2 votes

Closed loop transfer function problem

Take the simple example of an op-amp with dominant pole compensation. Open loop it has the approximate transfer function of Ao/(1+s*tau). Put resistive feedback around it and you can get an ...
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2 votes

Steps to hand draw Bode magnitude plot for a particular transfer function

Write it in the form \$\dfrac{K}{s(1+s/\omega_1)(1+s/{\omega_2})}\$, then you have the breakpoints and the correct gain term.
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2 votes
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Steps to hand draw Bode magnitude plot for a particular transfer function

First check the transfer function for poles and zeros. In this case the numerator is a constant, so there are no zeros. The poles are the zeros of the denominator. By inspection we see that they are ...
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