8 votes

Intuitive understanding of relation between phase margin and peak overshoot and/or damping factor

There is a way to link the open-loop phase margin \$\phi_m\$ with the closed-loop quality factor \$Q_c\$. The exercise involves concentrating in the vicinity of the crossover frequency and ...
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7 votes

How do I go about solving this block diagram?

Just re-arrange things to get rid of the interlocked feedback loops. Here's the first interlocked loop solved (I'd made a mistake yesterday that I'm correcting today): - OK, there's still some work ...
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  • 384k
6 votes
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Phase Margin and Transient Response Contradicting?

The control loop in your example uses a TL431 which is a self-contained op-amp plus reference. This part needs at least 2.5 V to operate properly. When you reduce your output voltage to 4 V, you are ...
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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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  • 2,124
5 votes

Output Impedance for Stability Analysis

It is necessary to distinguish two measurement methods here even if both deal with output impedance measurements: the first one deals with the measurement of the output impedance in closed-loop ...
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5 votes
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Open loop system instability

Yes, open-loop systems can be unstable (examples below, there's innumerable ones). "Open loop" can be a fuzzy term, and if there was a pitcher of beer on the line I could prove that any ...
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  • 36.3k
5 votes
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Finding transfer function from Bode plot

For a 2nd-order low-pass filter you can use this to calculate what the damping ratio, (\$\zeta\$) is: - Image from my basic website. Look at the peaking frequency in your spectrum and calculate the ...
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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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  • 7,274
4 votes

Understanding how the TS100 soldering iron 'safely' drives its power MOSFET

The circuit is designed such that the microcontroller GPIO controlling the heater circuit must be pulsing in order for the capacitor to couple a signal through to the NPN transistor in order for it to ...
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  • 5,367
4 votes

How will the derivative block of PID controller behave in case of zero error?

The value of the error at a given point of time does not really give you insight into the derivative. If the error is constant with time (and is zero, or something other than zero) then the derivative ...
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3 votes
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What is the phase margin when there are multiple gain crossover frequencies

I found the answer in "Fundamentals of Power Electronics" by Robert W. Erickson and Dragan Maksimovic (Pages 365-367). The book works through an example of testing the stability of a system ...
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3 votes

Intentionally tripping a fuse to disable a circuit in an unrecoverable fault condition?

A fuse will probably work, but that's not how it is done in industry. For starters, you have to deal with replacing a fuse each time there is a fault. I worked on steel annealing furnaces where the ...
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  • 366
3 votes
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Alternative MOS and IGBT for MPPT controllers

Regarding the point about MOS or IGBT transistors - PWM can be achieved with any device that can handle the correct voltage/current and can switch between fully on and fully off. It happens that MOS ...
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  • 13.9k
3 votes

How will the derivative block of PID controller behave in case of zero error?

I have explained operation of a PI controller in my answer to Understanding the flow of a PI Controller?. You might find it useful to read that as it gives a simple example of what happens the P and I ...
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3 votes
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What's the problem with my gain block?

I believe your problem is the 940F capacitor, with a time constant of about 600s in combination with the 0.61Ω resistor. What you are seeing here is a very very slow charging capacitor - check out the ...
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3 votes
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Can any one explain what type of compensation is this

The right hand red box is not a compensating circuit; it just uses the TL431 as a voltage comparator and starts putting current into the opto LED as soon as the output target voltage is reached. This ...
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3 votes
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BIBO and impulsive stability in voltage-controlled electrical circuits

The basic problem here is that your question, as stated, is unanswerable. So rather than try to answer it, I'm going to show you why. The reason it's unanswerable is because you're trying to map ...
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3 votes

Reverse engineering garage door opener signal

I doubt that playback will work. My guess is the protocol uses a similar protection as the rolling code method, and the initial character is identical each time. @Jasen said it is UART protocol, which ...
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3 votes
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Is the resonant frequency as defined for a second order transfer function same as the frequency at resonance in a second order electrical circuit?

I don't understand why You appear to be confusing two things; the natural undamped resonant frequency of an RLC circuit and, the damped resonant frequency of the transfer function. There are several ...
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3 votes
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How output is not zero if error is zero in control systems

A simple P (proportional) controller will, in general, NOT track a set point exactly. As you correctly point out, there must be an error in order for the controller to have a non-zero output. To track ...
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3 votes

Intuitive understanding of relation between phase margin and peak overshoot and/or damping factor

For your "intuitive understanding" it is helpful to realize that your question touches the relation between the time domain (overshoot) and the frequency domain (stability margin, damping ...
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  • 22.6k
3 votes

How to add a constant to a control system block diagram

You cannot get a single-input, single-output transfer function of this system that takes both \$u\$ and \$c\$ into account. Laplace-domain analysis only works for linear systems, i.e. ones that obey ...
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2 votes
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Zero Order Hold Bode diagram

Consider a sinewave sampled close to the Nyquist frequency (this can be an analogue sinewave that is sampled by an ADC or, a digital reproduction of a sinewave created by a DAC). Then, consider what ...
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2 votes

Zero Order Hold Bode diagram

\$ 1 - e^{-sT} = 0 \$ for \$s = \color{red}{0j}, \ j\frac{2\pi}{T}, \ j\frac{4\pi}{T}, \ j\frac{6\pi}{T}\$ etc. The zeros when plotted in dB show up as \$-\infty\$; i.e. sharp dips at equal intervals ...
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  • 3,646
2 votes
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Simulink - Zero Order Hold transfer function

Well, it was my bad. Everything is working perfectly on Matlab. The error was coming from the definition of the ZOH transfer function. I added a gain G0 as you can see. And this gain was not take into ...
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  • 1,440
2 votes

How does negative feedback control system begin to work fast

The actuator cannot become faster if it's not driven harder. The calculated bandwidth widening happens only if there's no overdrive in any part of the system. A simple example: Have an opamp with GBW =...
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  • 21.4k
2 votes
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Space State on SEP/Ex DC-Motor

At this moment, on the second bullet, is there a reason not to consider if time-varying (shouldn't it be \$i_f(t)\$ or was it just a typo)? I would consider it a typo. I've tried to put together the ...
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  • 36.3k
2 votes
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How to calculate inverse Laplace of this response function?

To answer my own question: I think the solution is as follows (it took me incredible long to find it out, although the problem seems quite simple): Assuming to be at the edge of just having no complex ...
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  • 361
2 votes
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Differential Equation to state spaces representation

There is no one correct answer for the state-space representation. If you choose the state as \$x_1=x\$, then the equations are $$ x_1'=-0.2x_1+0.2u\\y=x_1$$ If the state is chosen as \$x_1=2.5 x\$, ...
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