Questions tagged [control-system]

A system that may be electronic circuits or even software that uses control theory (principally differential equations) to control an output by monitoring various aspects of the system under control and varying inputs all towards meeting a defined goal. Some famous examples are controlling a rockets thrust angle to ensure directional control.

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Root locus of discrete time system

I have a question about a probably easy task, but I can't find the right K. I have the loop with an adjustable gain element given: $$Q(z) = \frac{H(z)}{1+ K\cdot G(z)H(z)} $$ I have given: $$H(z) ...
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Can 3-phase FOC control be done without current measurement?

Can a FOC control scheme be done using a rotary encoder to measure the position, speed and acceleration directly, or is measuring current necessary? FOC is a motor control scheme as described in ...
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Control system stability with respect to gain margin and phase margin

I have learn from control system that for a stable system gain margin and phase margin both must be positive. That is the truth. But I have a doubt about this simple third order type 2 open loop ...
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How to measure temperature of a syrofoam cutter hot wire?

I would like to create a hot wire foam cutter device. The wire material is nichrome, diameter 0.9mm, resistance is about 1.7 Ohm/meter. For best cutting results, I would like to control the ...
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728 views

Automatic calibration of a zero cross detector latency

I have a circuit similar to this one (different component values, different uC): I expect a large phase error in the ZCD. The load is purely resistive and of unknown value between 100W and 1000W. I ...
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Stability of a differentiator

I'm a bit confused regarding the stability of a differentiator and an integrator. When an integrator is added to the system it decreases the stability as it adds a pole at origin and bends the root ...
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Laplace transform and the idea of frequency domain analysis

I have studied control theory in depth in my undergrad and still continue to use it on many occasions in my PhD work, but i still don't fully understand why we call Laplace transformation of system a "...
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137 views

How to perform a \$\dfrac{1}{s+a}\$ type integration in MATLAB?

Currently, I am integrating an ODE of the form \$\dot x = f(x,t)\$ in MATLAB using the function ode45 This is equivalent (in block diagram form) as passing \$\dot x\$ through an integrator \$\dfrac{1}...
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Control theory - how to represent these transfer functions?

I'm learning control theory. Block diagram for transfer function: is: What would be block diagram for these two transfer functions: $$H(s)=\frac{1}{s^{2}+1}$$ and $$H(s)=s\frac{1}{s+1}$$?
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Finding Open/closed loop transfer function

I plan to determine the open/close loop transfer function of the attached motor. I have been able to combine K(s) to 1/s in series but am not too sure of how to add up 12/pi outside the summing ...
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Design a P-Controller given the root locus ?

I used to have the transfer function given but here the root locus instead ... Can one help with the start...
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problem : find the coefficients of linear system used to build a digital oscillator ..?

Please can one explain to me I having difficulty on how to start Thank you all *** can anyone correct me if anything is wrong !
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Determine unhampered natural frequency and motor constants from graph?

I can find zeta from the PO given in the graph but I don't know any rule relate wn with tp and I don't have value of the of ts and tr For part b and c I don't know where to start please help me to ...
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898 views

System response with initial condition

I have a small problem figuring out how to properly solve that. I could use help. Say a system with a transfer function \$ H(s) = \frac{100}{0.4s + 1} \$ is excited with an excitation \$u(t) = 8V\$ ...
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Quick question about a closed loop control system

Using above loop, we see that \$ \dfrac{y(s)}{r(s)} = \dfrac{p(s)c(s)}{1+p(s)c(s)} \$ and \$ \dfrac{e(s)}{r(s)} = \dfrac{1}{1+p(s)c(s)} \$ (well known results) Why is that: If the close loop ...
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Does movement along the imaginary axis of a root locus change the natural frequency?

I have two root locus plots (x-real, y-imaginary) of the same oscillating mode: (1) for a base case system and (2) a system with added feedback. They are so similar, almost identical that I am having ...
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Systems stability with zero poles

I have a rather simple question I would say. I know that systems having real poles to the right side of the plane will inevitably be instable (for LTI systems at least). But I'm confused with ...
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Explanation of 2nd order transfer function

I am reading about the 2nd order transfer function of a 2nd order system (like the mass-spring-damper system). I am constantly seeing the following form as the standard one: \begin{equation} H(s) = \...
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CONTROL CIRCUIT : Question Regarding Voltage and Resistance

I was wondering, whether my explanation was correct or not. I checked with online sources and they say I was incorrect, but I cannot understand how I am incorrect. As the resistance increases, doesn'...
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Is it possible for two different systems to have the same step response, and vice-versa?

Every time I have had to tune a controller (PID, usually) to a process, I have first matched an equivalent first order or second order model by doing some curve fitting on the step responses; and then ...
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Interpreting bode plot of type 3 compensation network for buck regulator

I'm struggling to design the type 3 compensation network for a simple buck PWM controller. The controller is a Richtek RT8110B. According to the datasheet, half of the type 3 network is in-built and ...
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Step response of feedback system

We have a feedback system F(s) as in this figure: and this is the step response of G(s): and H=10. F(s): We got the root locus of the system F(s) as this: then we determined the gain at ...
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Why are linear systems poor oscillators?

Given a linear system with initial conditions. If you have conjugate poles in D(s) that lie right on the jw axis, you should, in theory, be able to get sustained oscillations that do not grow unbound ...
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How to tune a PID controller to a nonlinear process

I have a nonlinear thermal process (nonlinear radiation becomes more and more present as temperature goes up) that I would like to tune a PID controller to. I'd like to control the temperature as ...
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evaluate number of poles lying on the right,left side of s-plane and on the jw-axis? [closed]

the transfer function is \$\ T(s)= \dfrac {1} {2s^5+3s^4+2s^3+3s^2+2s+1} \$ I solved it using RH criterion by evaluating the columns but results are different when i solved it with by matlab they ...
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Equilibrium points of a circuit with a diode

The given circuit is shown in the first picture, whereas the characteristic curve of the diode in the second one. I want to calculate a model in the form of $$\frac{d\textbf{x}}{dt}=f(x,u) \\ \textbf{...
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242 views

Bode plot of poles that are close to each other

I have a transfer function of the following form: \$\ T(jw)= a0 / (1+ s/w1) (1+ s/w2) (1+ s/w3) \$ where a0 = 3600 w1= 1MHz w2= 4MHz w3= 40MHz I drew the the bode plot and double checked with ...
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root locus of \$t(s)=\frac{K(s+2)}{(s+3)(s^2+2s+2)}\$?

I calculated the breakaway points. They come out to be Root 1: -2.481 Root 2: -0.689 Root 3: 1.17 because of root locus properties only the -2.481 will fall on root locus . But when I saw the ...
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control 2 outputs with a single input and pid

Overview I'm trying to levitate a constrained permanent magnet with 2 electromagnets. I'm having trouble conceptualizing the control system for such an operation. Setup The permanent magnet is ...
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142 views

Why is this second order system difficult to control?

Why is system of the type $$T = 1/(s^2 - 1)$$ Difficult to control using standard control methods? When I look at frequency plots, it doesn't seem to give me any important information as to why ...
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How do I size the output capacitor for a DC bench power supply?

I'm designing a DC bench power supply and have come to the matter of choosing the output capacitor. I've identified a number of related design criteria, but I'm finding my reasoning still going a bit ...
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Deriving PI controller transfer function when input is reversed

I'm developing the compensator for the linear DC Bench Power Supply I'm designing. As I've come to deriving the transfer function for the op amp-based compensator, I realize I've been depending on a ...
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628 views

What is this RC local feedback configuration?

I'm studying power converter control loops using Christophe Basso's book Designing Control Loops for Linear and Switching Power Supplies. A very common pattern in the compensator circuits is a ...
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2answers
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Is a Type 2a PID(ish) controller just an example of an augmenting integrator?

In a previous question I finally cracked the code on deriving for myself the transfer function for a Type 2(a) compensator like this one, built around an op amp. As it turns out, for AC analysis ...
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4answers
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Getting transfer function from block diagram

I am having trouble figuring out this step in an example question I've been given. I'm supposed to be finding the 'transfer function in the forward path'. This image shows the block diagram (top) and ...
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930 views

Find the first-order transfer function from a measured step response data

In a school experiment, we had to measure an output voltage from an IC. We gathered the data with respect to time. Now we have to find the transfer function given the output data. I think the whole ...
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How to find the transfer function of a frequency counter?

I am designing a mathematical model for my control systems project and in that there is this block which measures the frequency of the wave. For the practical application I fed this wave into a micro ...
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1answer
496 views

Is there a standard symbol for gain margin?

In the context of control loops, specifically power supply control loops in my case, the symbol \$\phi_m\$ is used for phase margin. I've occasionally seen it with a capital M, but on balance it seems ...
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295 views

Equivalent block diagrams, how to infer?

Assume I have one block diagram and I want to simplify it to an equivalent block diagram, how do I find such block diagram apriori? For example, Smith Predictor structure The first pic above is ...
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1answer
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Developing \$C_{out}\$ spec for DC Bench Power Supply

I'm designing a DC Bench Power Supply, following the general design procedure described by Christophe Basso in his book Designing Control Loops for Linear and Switching Power Supplies: A Tutorial ...
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Control: what is the proper justification that you can't just make the output equal to the input if the system produces unstable output

Suppose we have a signal, it goes into the plant and generates an unstable response, a common question then arise at that point is why can't we just set our output to a "hard-coded" input. Think of ...
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Why are low-dropout (LDO) voltage regulators unstable?

LDO regulators based on P-type transistors seem to be the preferred form of linear voltage regulator today, but I keep hearing about how I have to choose the output capacitor(s) carefully to guarantee ...
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How to control 220 volts without using relays?

I have a fan in my house, It has an electronic PCB that responds to a remote control. The PCB has a voltage dropping capacitor so, I think it is supplied with a very low voltage such as 9 or 12 volts. ...
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What is the difference? [closed]

What is the difference between embedded systems and control systems? I have to choose my future career and I don't now the difference.
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Is time-invariant system taking system initial state account?

The time-invariant system is defined as following: If y(t) = (H(x))(t) and y(t − τ ) = (H(x))(t− τ ) Then H is a time-invariant system. Has this definition taken system initial stats account? At t=0 ...
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speed control loop for line following Robot

I am working to control the speed in my line following Robot (using arduino uno),by using proportional constant Kp in a closed loop, in my code I calculate the RPM from The Right Motor and the Left ...
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Classic control theory - Negative gain required for a finite velocity error?

I have an assignment to design a control system with 2 degrees of freedom (Prefilter + Controller) to control a plant with the following transfer function: $$P(s)= \frac{2}{s(s-3)}$$ I am required to ...
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7answers
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Control theory basics

I'm trying to understand something very basic about Control Theory. Let's say I have the following loop: If we'll relate this loop to a cart with a motor going in its single axis from X = 0 to X = 50,...
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1answer
827 views

Solenoid Valve for Selecting Between 2 Outputs

I'm looking for a solenoid (like) valve which will have 1 flow input, and which depending on the applied signal, will switch between 1 of 2 flow outputs. The electronic equivalent of what I'm ...
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2answers
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Stability of an unstable system using nonlinear element. Is it possible or not?

Say there is an system with open-loop transfer function $$G(s)=\frac{1}{s-1}$$ The system is definitely unstable. If I put an any nonlinear system in cascade with \$G(s)\$ & from the output, a ...