10 votes

Relation between signal processing and control systems engineering?

I did my signal processing Ph.D. in a control systems department. My take is that signal processing is open loop; control systems close the loop. Apart from that, the mathematics behind both are very ...
Peter K.'s user avatar
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8 votes

Relation between signal processing and control systems engineering?

Both draw on Linear System Theory (a.k.a. "Signals and Systems"). So also does Communications Systems and Linear Electric Circuits, Electronic Circuits,and Distributed Networks (a.k.a. Transmission ...
robert bristow-johnson's user avatar
7 votes
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In the context of transfer functions, what is the relationship between the terms "proper", "causal", and "realizable"?

Causality is a necessary condition for realizability. Stability (or, at least, marginal stability) is also important for a system to be useful in practice. For linear time-invariant (LTI) systems, ...
Matt L.'s user avatar
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6 votes
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How can a system be unstable if $L(j\omega)$ is never exactly $-1$?

You cannot make conclusions about the stability of a system by only considering its transfer function evaluated on the imaginary axis $s=j\omega$. Replacing $s$ by $j\omega$ in the transfer function ...
Matt L.'s user avatar
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6 votes

What is the principle behind my voice echoing perpetually when 2 separate devices are used for playback and recording on video calls?

On each individual device, the speaker output can get subtracted from the microphone before it gets sent to other locations. This prevents others from hearing themselves through your microphone. When ...
ScienceGeyser's user avatar
6 votes

State space physical meaning

As you pointed out, there are many state-space realizations of one particular transfer function. The reason is that a transfer function only represents the input-output behavior of a system (...
Gab's user avatar
  • 75
6 votes
Accepted

How accurate is the dominant poles approximation in higher order control systems?

It depends entirely on how close the less dominant poles are to the dominant poles. A simple way to understand what is happening is consider poles on the real negative axis for continuous time systems:...
Dan Boschen's user avatar
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5 votes
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What is the Reference in Control Theory?

Imagine that you're heating (or cooling) a home with a modern furnace (or air conditioner). the reference or set point is the temperature that you set your thermostat to be. the feedback signal is ...
robert bristow-johnson's user avatar
5 votes

What are the advantages of LTI ( Linear Time Invariant ) systems over other systems?

It's important to realize that in practice many types of systems are used, and only some of them can be regarded as (approximately) LTI. The (didactical) advantage of treating LTI systems in a basic ...
Matt L.'s user avatar
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5 votes
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Why oscillations in PI control?

Integration has memory. When the error becomes zero, there is no guarantee that the integrator has reached to zero sum of the previous errors. So even when there is no error at a particular time the ...
percusse's user avatar
  • 522
5 votes

Why do these 2 methods give different solutions?

The problem is that you took the derivative of the function $$\hat{x}_u(t)=2e^{-3t}-e^{-4t}\tag{1}$$ whereas using the Laplace transform you implicitly assumed that $x_u(t)$ equals zero for $t<0$:...
Matt L.'s user avatar
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5 votes
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How do I stabilize my oscillating system?

First, combine your two variable set of first order differential equations into a single variable second order one. $$ \frac{d^2y}{dt^2} = c \frac{dx}{dt} = acy + bc $$ $$ \frac{d^2y}{dt^2} - acy = ...
Cedron Dawg's user avatar
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5 votes
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State space equations

Two principles here: When dealing with a differential equation, you define intermediate state variables so everything is in terms of first derivatives. This system is nonlinear, so the state-space ...
Robert L.'s user avatar
  • 2,212
5 votes

Which step response matches the system transfer function

Open loop gain at DC is -3dB or .707 and 0 degrees. We don’t know the forward gain but assuming it is the open loop gain, the closed loop gain would be $.707/(1+.707)= .4148$, matching the first plot. ...
Dan Boschen's user avatar
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5 votes
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Which step response matches the system transfer function

The final value of the step response is the DC gain of the closed-loop transfer function, which is generally different from the open-loop DC gain. Assuming unity gain feedback, the feed-forward ...
Matt L.'s user avatar
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5 votes
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How do you design using bode plots?

The Bode Plot is typically used to display the open loop magnitude and phase response, for which we can assess stability in many cases (not all). The stability criteria that the phase is less than -...
Dan Boschen's user avatar
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5 votes
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Intuition for $\mathbf{P} = \mathbf{0}$ in steady-state when $\mathbf{Q} = \mathbf{0}$ (Kalman filter)

We each have different life experiences to fuel our intuition, but try this one out: Let $\mathbf A = 1$ and $\mathbf Q = 0$, and $\mathbf C = 1$ -- i.e., the actual state variable just doesn't change,...
TimWescott's user avatar
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4 votes
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Mathematically speaking, is a "signal" a function or the set of outputs from a function

A signal is a physical quantity (e.g. voltage) carrying information, or a set of values (e.g. samples in discrete case) of the given function for different values of the underlying independent ...
Gilles's user avatar
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4 votes

Are there theories to manage states of signal volatility around a limit

In electronics, a Schmitt trigger converts an analog signal to a digital signal by using two different thresholds (limits as you call them), one for an output state change from 0 to 1 and another for ...
Olli Niemitalo's user avatar
4 votes
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Do we use closed loop or open loop information in Bode plot, Nyquist plot and Root Locus?

The root locus is a way to see how the poles of your system vary from their open loop locations to their closed loop locations. If the closed loop system is $$ C(s) = \frac{O(s)}{1+KO(s)} $$ where $O(...
Peter K.'s user avatar
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4 votes

Do we use closed loop or open loop information in Bode plot, Nyquist plot and Root Locus?

The bode plot is just a plot showing the frequency representation of your system. Any transfer function has one, hence you can use it to see the response of both closed or open loop. Nyquist and the ...
LJSilver's user avatar
  • 768
4 votes

Do FIR filter have any application in control theory?

FIR filters are fairly common in some areas of control theory. As they usually incur a lot of added phase/time-delay, they are not really usable in the feedback path of regular control systems, but ...
Arnfinn's user avatar
  • 1,035
4 votes

Why oscillations in PI control?

For symplicity, consider the SISO linear system \begin{align*} \dot x &= ax +bu\\ y &= cx \end{align*} with $x$,$u$ and $y$ taking values in $\mathbb R$. Assume that you want to stabilize the ...
LJSilver's user avatar
  • 768
4 votes
Accepted

What is the difference between a lag compensation and PI control?

Well, the two systems differ only at low frequencies. In fact, if you define $$ R_L = \dfrac{\tau_zs+1}{\tau_ps+1},\qquad R_I = \dfrac{\tau_zs+1}{\tau_ps} $$ you have that $R_I(j\omega)\underset{\...
LJSilver's user avatar
  • 768
4 votes

When can the $\mathcal Z$-transform be inverted? When not?

If I understand your question correctly then you're asking under which conditions the inverse $\mathcal{Z}$-transform of a given function $F(z)$ exists. Since the inverse $\mathcal{Z}$-transform is ...
Matt L.'s user avatar
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4 votes
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Step response of a differentiating system

If your system is an ideal differentiator with input-output relation $$y(t)=\frac{dx(t)}{dt}\tag{1}$$ then its transfer function is $$H(s)=\frac{Y(s)}{X(s)}=s\tag{2}$$ From the equation in your ...
Matt L.'s user avatar
  • 89.6k
4 votes
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Discrete State Space Model - Why Are We Calculating $ x \left[ k + 1 \right] $ Instead of $ \dot{\boldsymbol{x}} \left( t \right) $?

I will ask you something that will give you intuition. How would you calculate the Gradient of an image? Image is a discretization of reality, so how would you estimate the gradient of the "Reality" ...
Royi's user avatar
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4 votes

Discrete State Space Model - Why Are We Calculating $ x \left[ k + 1 \right] $ Instead of $ \dot{\boldsymbol{x}} \left( t \right) $?

Hi: I've been wondering about the same exact thing myself and the light bulb finally turned on a few days ago when I went back to Kalman's 1960 paper. ( I've read it many times but not recently ). ...
mark leeds's user avatar
  • 1,107
4 votes

Relation between signal processing and control systems engineering?

There's a fairly simple distinction. Signal processing is a set of tools that can be used for control engineering. Control engineering is about making something move how you want it to move. Some of ...
Graham's user avatar
  • 311

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