# 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.

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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 ...
174 views

### 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, ...
89 views

### 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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Currently I'm learning about LPV systems and long-story-short I intend to create a simple LPV plant model for a DC motor. Imagine a simple 2x2 matrix for its space-state: $$\begin{bmatrix}\ \dot x_1 \... 0 votes 2 answers 86 views ### 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 ... 0 votes 0 answers 73 views ### 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 ... 0 votes 3 answers 139 views ### 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:... 1 vote 1 answer 741 views ### 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 ... 0 votes 0 answers 175 views ### 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, ... 6 votes 2 answers 998 views ### 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 ... 2 votes 0 answers 64 views ### 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 ... 1 vote 3 answers 74 views ### 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 ... 0 votes 0 answers 40 views ### 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 ... 0 votes 0 answers 72 views ### 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 ... 0 votes 1 answer 225 views ### Decide P controller gain K so that phase margin is 50 deg I need help finding the gain $K$ so that the phase margin for the system equals 50 degrees.$$F(s) = KG(s) = \dfrac{1}{(s+1)^2}$$$v$ is a process disturbance sinusoid with amplitude 2.5 and ... 1 vote 0 answers 79 views ### From where does State space model equations come from? I have a good basic understanding on classical control theory. Now I am studying modern control theory.I encountered the following equations as seen below. Online I have only been able to find ... 1 vote 0 answers 72 views ### fast analytical technique identifying poles/zeros using degree of freedom I encounter some engineers who can quickly spot poles and zeros in the circuit by identifying "degree of freedom". For example, a typical technical discussion goes like : "a miller ... 0 votes 0 answers 241 views ### Determine range of proportional gain with given overshoot I have given the open-loop transfer function$$ G_{ol} = 1.42 \frac{(s+3)^2+6^2}{(s-1)(s+2)((s+4)^2+4^2)} $$The task I was given is determining the range of the proportional gain, which makes the ... 1 vote 2 answers 387 views ### Tuning PID without transfer function I'm very new to control theory and I am stuck at PID tuning. I have a given Simulink model but I do not know the transfer function. I want to use a PID to provide new input from the output of the ... 0 votes 3 answers 148 views ### Why do I need phase margin if I know the transfer function? What is the point of examining the phase margin (or gain margin) for a closed-loop system if I can just solve for the transfer function. The transfer function will give any poles and zeros, which can ... 1 vote 1 answer 86 views ### Linearization of nonlinear system I have a nonlinear system described by:$$\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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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 ...
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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, $G_{h0}$ ...
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### Nyquist stability criterion for positive feedback

it is known that the stability of a system with negative feedback may be analized through the Nyquist stability criterion, which is based on observing the number of turns around the point (-1;0) in ...
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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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### 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 ...
1 vote