11 votes
Accepted

Block diagram vs flow chart?

Use Google's define:<item to look up> feature. block diagram noun: block diagram; plural noun: block diagrams a diagram showing in schematic form the ...
Transistor's user avatar
  • 10.6k
9 votes
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Is nonlinear control slower than linear control?

"Linear" imposes a set of restrictions. "Non-linear" simply means there are no restrictions. Many non-linear control schemes can be faster than linear ones. Linear control schemes are restricted to ...
Olin Lathrop's user avatar
  • 11.4k
9 votes

If a control system is unstable does it mean it will oscillate?

An example of control system with non oscillatory response. $$ \frac{d x}{d t} = 0 + u\\ u = x $$ Closed loop equation of this unstable system is $$ \frac{d x}{d t} = x $$ and its response is $$ x(t) =...
AJN's user avatar
  • 1,039
8 votes

Minimal realization of a MISO system

One way of doing this is using the Kalman decomposition. For this you need the reachable and unobservable subspaces. These subspaces can be constructed using the image of the controllability matrix ...
fibonatic's user avatar
  • 1,653
7 votes
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Why is it impossible to create an observer for this not fully observable system?

Observability means that you can estimate the complete state using only the output, without knowing the initial state. In other words, you have to figure out where you are without knowing where you ...
Daniel Nilsson's user avatar
7 votes

How are bode plots drawn for unstable systems with time delay?

You are absolutely right. Since the magnitude is the absolute value of the complex function $F(j\omega)$ the plot does not change with the sign of the pole or zero. The Phase on the other hand does ...
RaulG's user avatar
  • 71
6 votes
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When are overshooting controllers preferred over asymptotic ones?

For some systems, the salient criterion is settling time to within some error band. Sometimes you can get faster settling by allowing earlier overshoot. If you need a system to get to within some ...
Olin Lathrop's user avatar
  • 11.4k
6 votes
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In Control Systems Engineering, why do imaginary poles and zeros on the LHP indicate stability?

Only the poles in the LHP are necessary for stability. This is because the transient response of a LTI system will consists of a linear combinations of $e^{p_i t}$. If a pole is complex, $p_i=\rho_i+i ...
fibonatic's user avatar
  • 1,653
6 votes
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Advantage of anti-windup

Anti-windup is a concept for feedback controllers with integral terms, e.g. PID, to keep the integral term from „overcharging“ when regulating a large set point error. It basically saturates the ...
OpticalResonator's user avatar
5 votes
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A stable transfer function which diverges?

Without any more info, I think your problem arises from the values of $a_0$ and $a_1$. The answer is a little involved, so a bit of systems background is necessary. The short answer Your system should ...
BarbalatsDilemma's user avatar
5 votes

Why can't proportional gain alone, reduce the error to zero?

To understand why proportional gain won't drive the error point to zero, it is best just to look at the math. Consider the PID loop shown in the image below. The loop algebra in the $s$ domain comes ...
Chris Mueller's user avatar
5 votes

Controllability of $x' = Ax + Bu(t)$ implies controllability of $\left \{ \begin{matrix} x' = Ax + By \\ y'=u(t) \end{matrix} \right.$

The solution is fairly straightforward. Short answer The system is controllable without any modifications. You made a small mistake calculating the new controllability matrix: you are missing the ...
BarbalatsDilemma's user avatar
5 votes
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Continuous time and Discrete time systems

A controller is built around a physical system. What is the open-loop behavior of the system? You have to sample the physical (continuous-time!) system in order to provide feedback to your discrete ...
Chuck's user avatar
  • 3,565
5 votes

Quaternion in control applications

Euler angles are easier to understand and use. Imagine a airtrafic controller getting a aircraft heading info as quaternion data. Euler angles are significantly easier to understand interpret and ...
joojaa's user avatar
  • 3,597
5 votes
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Square wave transfer function?

I thought I would expand a little on the answer offered by Karlo. Long story short, I would not try to calculate the analytical time response of a system to a square wave. That would be a serious ...
ConjuringFrictionForces's user avatar
5 votes

Open loop versus closed loop Model Predictive Control

I think the other answer is not complete. Model predictive control (or 'receding-horizon control' is a technique in which a predictive system model is used to evaluate a sequence of future control ...
Nicholas Moehle's user avatar
5 votes
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Which course to take? Optimal control? Nonlinear control?

In nonlinear control theory, you will recognize most concepts such as controllability and observability where the linear case is often a special case of the nonlinear case. I would highly recommend ...
link's user avatar
  • 98
5 votes
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Root Locus and Routh–Hurwitz stability criterion

Suppose we have a third order polynomial in the form : $$ s^3+a_2s^2+a_1s+a_0 = 0$$ There is nice caveat for third order systems which is derived from the Routh-Hurwitz stability criterion. In order ...
Teo Protoulis's user avatar
5 votes
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Can someone explain how the output of this control system is derived?

Well as a fresh start: net(n) is the value before the node, this can be seen by equation (1). The value after the node is the following (lets call this $x$ for simplicity): $$x(n) = net(n) - a_1x(n-1) ...
Petrus1904's user avatar
  • 1,069
5 votes
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How do I interpret the following Bode, Nyquist and Nichols diagrams?

Your systems shows extremely close pole-zero cancellation. So much even that it nearly removes 4 poles and zeros. Lets look at why, starting with the Bode plot: The magnitude plot is constantly ...
Petrus1904's user avatar
  • 1,069
5 votes

Full state feedback of a closed loop system

Let me phrase this a bit more elaborate. Suppose we have a state space system, ie: $$\dot{x} = Ax + Bu$$ Where the dynamics of the system are presented through $A$. For instance, the poles of the ...
Petrus1904's user avatar
  • 1,069
4 votes
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Control theory - Differential equations and state variable description

A professor of mine, long ago, once quipped: "Give me a word... any word at all... and I'll show you how the root of that word is a PDE!" A touch of Philosophy All physical systems are modeled ...
Paul's user avatar
  • 2,569
4 votes

Difference between PI and PD controller?

PI - Proportional - Integral The output is a combination of how far you are from the goal and the integral of your distance from the goal (total error over time). This means that it will track small ...
Andrew's user avatar
  • 766
4 votes
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What do actually control engineers do?

In short, 'systems' refers to a combination of components that act together and perform a certain objective. A system can span across different physical and virtual domains. Controls engineers ...
RaaziR's user avatar
  • 56
4 votes

Anomaly in viscous force - vs - velocity relationships

The examples you mentioned both occur due to turbulent flow of a gas. However in a lot of mechanical systems damping often occurs due visco-elastic deformation or due to shearing of the lubricant ...
fibonatic's user avatar
  • 1,653
4 votes

How to determine the region in a state plane where the equilibrium state is asymptotically stable

As you might already know your system is nonlinear, which means that it is not trivial at all. See below for the plot of the system. The linearization around $(0,0)$ gives you the information that the ...
MrYouMath's user avatar
  • 1,036
4 votes
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Nyquist plot - what is the meaning of circles with dB values on complex plane

See doc nyquist: The nyquist function has support for M-circles, which are the contours of the constant closed-loop magnitude. M-circles are defined as the ...
user883521's user avatar
4 votes
Accepted

How to execute trajectory?

You have to choose a controller that best fits the system you are trying to control. You have to take into consideration the variables you are trying to control when deciding on the controller. ...
Mika Sundland's user avatar
4 votes
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Time constant - formula

Does the book not give you the mathematics? The underlying expression is: $$parameter = 1-e^{ -t/ \tau }$$ so you see at $t = \tau$ $$parameter = 1 - e^{-1} = 0.63$$ Now the second sentence says ...
agentp's user avatar
  • 969
4 votes
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Why does a proportional controller have to have a steady state (offset) error?

If you open your drain valve, and then close it again, then you're correct, the tank will refill back up to 50, leaving you with no offset. If, however, the valve is left open, then the water may not ...
Jonathan R Swift's user avatar

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