Questions tagged [control-theory]
For questions about control theory as it relates to electrical engineering, which provides tools to design electronics so that a system's output(s) are driven to the correct state for given input(s) by ensuring stability, reducing steady state error, overshoot, etc. Consider using in conjunction with related tags such as "transfer-function", "stability", "feedback", "frequency-response", "step-response", "nyquist-plot", "phase-margin", etc., if applicable.
99 questions
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Boost PFC small-signal model for determining transfer function
I'm trying to design a digitally controlled boost PFC supply.
I've chosen to implement a converter according to the Biricha/ST presentation found here: here
I think once I have determined the ...
0
votes
1
answer
80
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Why a minimum phase system has to have positive pm and gm to be stable?
I'm very familiar with control theory and I came across this statement "minimum phase system has to have positive pm and gm to be stable" from many places. So I have this open-loop transfer ...
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Open loop transfer function - explaination
Assume there is a simple closed-loop control system with G(s) representing the plant and H(s) representing the feedback element:
Could any one explain what exactly is open-loop transfer function ?
...
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About controllable and observable discrete-time LTI systems
Consider the discrete-time LTI system with the following state-space representation:
\begin{align}
{x}_{k+1}&={A} {x}_k+{B} {u}_k &;{A} \in \mathbb{R}^{n \times n}, {B} \in \mathbb{R}^{n \...
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For the equation below, how would I calculate the gain required for a settling time of 1 s?
The equation is:
\$G=\dfrac{k(s+4)}{(s+1)(s^2+6s+13)}\$
How would I calculate the gain (k) required for a settling time of 1 s?
By using \$ts=\dfrac{4}{(ωζk)}\$ the closest value I got was ...
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2
answers
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Isolation Topology in SMPS
I have been researching SMPS designs as a hobby recently and finally have the courage to build one for theoretical and practical understanding. I have chosen an isolated design looking at several ...
0
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1
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98
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Order of Complexity
Generally, number of independent state variables (order of complexity of a system) is equal to the number of reactive elements in RLC network. But, if capacitor and voltage source loops are present ...
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105
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Derive state space from initial value problem
I am given the following initial value problem
\$ y^{(4)} - y = u \$ with \$ y^{(3)}(0)=0, \ddot{y}(0)=1, \dot{y}=1, y(0)=10 \$
and am supposed to calculate the state space in the usual form
\begin{...
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2
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950
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Assign Bode plots to Nyquist diagrams
How do I assign the following Bode plots to their corresponding Nyquist diagram?
Can i tell the number of poles of the transfer function of the nyquist plot, by looking at w→infinity (from which of ...
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2
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Deriving a transfer function from Nyquist plot
I am given a half Nyquist plot and exercise as below
I know how to plot a Nyquist curve for a given transfer function but I have trouble doing it the other way.
I stumbled upon this post Deriving ...
2
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1
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289
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Compensator design for control systems
Currently, I'm working on linear control course from Nise's book. In the root-locus design chapter, some methods were explained for lag and lead compensator design which uses root-locus properties. ...
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Routh Hurwitz Criterion for Stability
What do the rows of the Routh table represent? What is the significance of writing the powers of 's' in the zeroth column?
user328583
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Confused about how Loop 2 is defined
In one of my exercises, I am presented with the following circuit:
We are asked first to write some loop equations for the circuit. Naturally, they are given to be defined as:
What I cannot ...
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3
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159
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Finding closed loop interval of stability with open loop frequency response data
I have the following open-loop frequency response data of a system:
Frequency (rad/s)
Gain (dB)
Phase (degrees)
0.0628
9.3080
-137.4711
0.1257
8.2370
-126.3069
0.2513
7.8477
-151.0235
0.6283
9....
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2
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What are the gain and phase margins from this Bode plot?
I thought I had a decent grip on how Bode plots work yet for this model that I am working on, I need to implement a lead or a lag compensator. A lead compensator, which I was thinking about ...
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2
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Contradictory relationship between quality factor and damping
I am studying control theory and mechanical vibrations.
From control theory aspect, I know that bandwidth and response time is inversely proportional, which means bandwidth and damping as well.
The ...
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3
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1
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What is the practical advantage of root locus method in control system engineering? [closed]
Recently I learned about the topic.
Decades ago, when no computational power was available for engineers, it was surely helpful in some way. But I do not understand what the advantage is nowadays, ...
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2
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294
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Laplace of third-order lead-lag filter
For Butterworth low-pass filters, the Laplace function of the third-order filter is
$$
H(s)= \frac {1}{\left(1+\frac{s}{\omega_c}\right)\left(1+\frac{s}{\omega_c}+\frac{s^2}{\omega_c^2}\right)}
$$
...
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2
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315
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Why is closed loop frequency response hard to determine?
I'm learning about frequency domain control design and one of its advantages is said to be that: one can deduce the closed loop behaviour of a system by (experimental) data on frequency response on ...
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How to design a 2nd order LP active filter with differents responses?
I have been asked to design and simulate a 2nd order analog low pass filter having the responses of Butterworth, Chebyshev and Bessel.
Im looking for guidance and suggestions,since I understand the ...
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3
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258
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Space State on SEP/Ex DC-Motor
I'm currently studying DC motors and I do have some doubts about the dynamics of it.
As per explained on [Guru, B.S. and Hiziroglu, H.R., 2001. Electric machinery and transformers (Vol. 726). New York:...
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1
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How can I calculate gain margin in this transfer function and the constant K?
This is the problem statement:
There is a mechanical crane whose Transfer Function is shown. If it is implemented
The automatic system shown, closing the loop and adding the G1 block (s), you are ...
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578
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PWM frequency and control system sampling frequency in dc-dc converters
I am trying to control the output voltage of a simple dc-dc buck converter, which is digitally controlled. The output voltage is sampled, and the control algorithm is run, at every \$T_s\$ seconds, ...
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I'm confused a bit on basic control stuff for a PID controller
I'm doing a PID controller demonstration project in which heat is applied to a K type thermocouple and I'm supposed to maintain the temperature read at 50 °C using a PWM signal. I know the basic ...
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0
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76
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Control system -- closed-loop system problem
Given a closed-loop system as shown below:
Suppose that \$x(t) = u(t)\$ and \$d(t)=0.5u(t)\$. Determine the output response of \$y(t)\$ and it's steady state at \$t\rightarrow \infty\$.
I've tried to ...
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3
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527
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Nichols plot confusion
The transfer function is \$F(p)=10/(p^2+2p+1).\$
Using Wolfram Alpha, the Nichols plot shows that the argument \$\to -\pi\$ when \$\omega \to +\infty\$.
However, calculating the argument on paper ...
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52
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Feedforward from measurable disturbance
Gff is chosen so that it completely cancels the disturbance (Gff = -Gv/P) and Lp < Lv. Is it easier to control if Tp < Tv or Tp > Tv. I am a little bit lost on how to begin here? Should I ...
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2
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146
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Meaning of "Dynamics" in terms of control systems?
What is meant by "dynamics" in context of control systems?
For example what is difference between the dynamics of an aeroplane and a car?
This question below answers to some extent my ...
- 1,161
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140
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Linearization of nonlinear plant with system identification in Matlab
I hope this question fits in here and there is someone who can maybe help me.
I am new to control theory and I have a very complex Simulink model which is nonlinear. I want to have a linear ...
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3
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Decide P controller gain K so that phase margin is 50°
I need help finding the gain \$K\$ so that the phase margin for the system equals 50°.
$$F(s) = K$$
$$G(s) = \dfrac{1}{(s+1)^2}$$
\$v\$ is a process disturbance sinusoid with amplitude 2.5 and ...
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2
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0
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141
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From where does State space model equations come from?
I have a good basic understanding on classical control theory. Now I am studying modern control theory.I encountered the following equations as seen below.
Online I have only been able to find ...
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1
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223
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fast analytical technique identifying poles/zeros using degree of freedom
I encounter some engineers who can quickly spot poles and zeros in the circuit by identifying "degree of freedom". For example, a typical technical discussion goes like : "a miller ...
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917
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Determine range of proportional gain with given overshoot
I have given the open-loop transfer function
$$
G_{ol} = 1.42 \frac{(s+3)^2+6^2}{(s-1)(s+2)((s+4)^2+4^2)}
$$
The task I was given is determining the range of the proportional gain, which makes the ...
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2
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Tuning PID without transfer function
I'm very new to control theory and I am stuck at PID tuning.
I have a given Simulink model but I do not know the transfer function. I want to use a PID to provide new input from the output of the ...
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3
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Why do I need phase margin if I know the transfer function?
What is the point of examining the phase margin (or gain margin) for a closed-loop system if I can just solve for the transfer function. The transfer function will give any poles and zeros, which can ...
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1
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Linearization of nonlinear system
I have a nonlinear system described by:
$$\begin{align}
V\,\dot x_1 &= Q_1 C_1 - (Q_1+u)x_1 \\
V\,\dot x_2 &= C_2\,u -(Q_1+u)x_2 \\
y &= -\frac{\log{\left[(x_1-x_2)+|x_1-x_2|+4K\right]}...
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2
answers
389
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Steady-state Error Definition
In the textbooks and reference material which I have been using during my course on control systems, a common definition of steady-state error is as follows:
$$E(s)=R(s)-C(s)$$
where E(s) is the error ...
0
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1
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343
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Finding the overall transfer function and plotting root locus of a digital control system
I have started to learn about digital control theory and struggling with a particular diagram of a digital control system. The system is presented below:
\$D(z)\$ is a digital compensator, \$G_{h0}\$ ...
- 1,191
2
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2
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920
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Nyquist stability criterion for positive feedback
it is known that the stability of a system with negative feedback may be analyzed through the Nyquist stability criterion, which is based on observing the number of turns around the point (-1;0) in ...
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1
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Layman explanation of "dynamics" or "dynamic behaviour"
I often read the term dynamics or dynamic behaviour in electrical engineering especially in control systems course
What is meant by it?
Is it means that the system whose internal state/properties ...
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What will be minimum number of states / state variables for these control systems in state-space model?
Consider the systems as LTI and SISO with transfer functions given below:
I have read that minimum number of states for an LTI SISO system required to represent in state space analysis for any ...
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1
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273
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555 square wave generation with frequency feedback
Knowing that 555's behaviour varies according to temperature, I wondered:
In an astable configuration, is there some way to measure output frequency, compare it with some desired value, and use this ...
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1
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Feedback Circuit schematic to Control Theory block diagram?
I'm studying analog electronics circuit with feedback.
I see that, during analysis, a useful abstraction over the schematic is the block diagram in control theory style, but I stuggle in deriving it ...
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1
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Nomenclature for changing characteristic curve
OK, I'm at a loss for words on this one. I'm looking for a word or phrase to describe the following situation...
I have an open loop control system that when I apply voltage \$A\$ I get output \$A_1\...
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620
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Transfer function with separate time delays in each term
We've been given the problem below for our current assignment
As far as I can recall, I have never seen a transfer function with time units in the function itself, added onto each separate term. I ...
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1
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188
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Looking for a quote on dynamic system identification
Does anyone know of a quote by an eminent control theorist or controls engineer or book author who I could reference who said something along the lines of the following:
The process of control ...
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Effect of RHP zeros on stability
Why do zeros in the right half of the \$s\$ plane reduce stability (i.e., gain / phase margin)?
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1
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3k
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Determining Number of states in State Space Modeling
I want to use state space modeling for representing the following circuit system. However, I am unable to decide the number of states. I am able to describe the system with a set of three equations. ...
user172541
0
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1
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302
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How to calculate roots using root locus method? [closed]
Find the roots of the following polynomial by use of the root locus method.
3s⁴ + 10s³ + 21s² + 24s + 30 = 0
(The root locus plot has not been given.)
Can you please help me with this?
This ...
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2
answers
8k
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Integral only control (as opposed to PI or PID)
I am familiar with PI and PID control but I've recently been reviewing code that seems to use I (Integral) only control. What are the benefits of I control over PI control, and when should it be used /...
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