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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243 views

design of compensator type 2 for current mode control of boost converter?

I have designed boost converter with Peak current mode control in PLECS. I have used the method of k factor approach to design the compensator. the bode plot transfer function of the power stage is ...
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4answers
2k views

Approximation of second order system, by step response

I am trying to aproximate a transfer function of a system. The system is a linear actuator, connected to a feedback potentiometer. The following figure is a step respons, with 24 V as input, and the ...
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319 views

Why linearise around an equilibrium point?

In the control theory dealt in class I was taught to always linearise a nonlinear system around an equilibrium point, i.e., where $$\dot x = 0$$ However, linearization is a Taylor series expansion, ...
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60 views

How to go about determing the System Type of my setup?

I have a small project where I am PID tuning two servo motors. Something very similar to this: I am interested in finding the system type of the above setup, which includes the PID loop I have tuned. ...
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102 views

Help with identifying a transfer function - with neuroscience application

This is a question for you electrical network engineers. The problem has arisen in a neuroscience study I am working on, but I hope to be able to glean some insight from other domains that deal with ...
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1answer
123 views

Gain of proportional Controller with distubance \$sin(10t)\$

The diagram below represents the position of ocean oil platform system which use the proportional controller with gain \$k\$. The output \$x(s)\$ is the platform deflection regards the position ...
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85 views

Pole-placement problem

I was following this example of implementing a pole-placement with an Integral controller. Matrices A_star=[-5 -3 0;1 0 0;0 -1 0] B_star=[1;0;0] desired poles -100,-8+i*11,-8-i*11 I know the ...
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3answers
909 views

Why is phase margin considered more important than gain margin in dc-dc converters?

Control theory text books say both gain margin and phase margin give information about relative stability. These quantities also give an idea about the corresponding closed loop system's transient ...
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What does asymptotic stability mean ? and can a system have lower than 90deg of phase margin and still be stable?

why bode stability criteria dictates 90deg of phase margin ? my understanding is that it is so when a system is cascaded with another there's a margin so the phase doesn't get to 180 and over, am i ...
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1answer
126 views

How can infer instability from the frequency response of control system?

When can we judge a control system to be unstable from its frequency response?.For example, thermostat computes the error signal (desired room temperature - actual room temperature) and then actuates ...
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171 views

PR controller electrical circuit

I am attempting to design a PR control feedback loop for a grid tie inverter. The math checks out but I can't seem to convert the transfer function and/or block diagram into an actual electrical ...
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613 views

Transfer function of phase change controlled with capacitance

We have an RLC series circuit with sinusoidal voltage source of frequency \$\omega\$. The normal transfer function of current to voltage is: $$ G(s) = \frac{I(s)}{V(s)} = \frac{1}{R+s L+ \frac{1}{s C}}...
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137 views

Design PI controller using LM2743 analogue controller

I'm final year student currently designing a buck converter with an analogue controller (LM2743). What my supervisor told me is to used a PI controller using bode plot. My design spec: 1. Vin=12V 2. ...
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Why aren't Stepper motors used in closed-loop systems and PID control?

I know stepper motors are usually operated in open-loop systems. I'm curious to why they aren't usually part of closed-loop systems? Also why aren't PID control methods commonly used with stepper ...
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503 views

Is the Nyquist plot useful in actual electrical engineering?

I am currently doing a course on linear control theory, and we are covering Nyquist Plot to study phase and gain margin. I find myself unable to appreciate this concept. One, the proof of the Nyquist ...
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1answer
112 views

How can I find the transfer function of a quadcopter's motor? [duplicate]

I want a model of a quadcopter and, thus, I need the transfer function of the motor. Any suggestions on how to do it will be very helpful for me. Thanks.
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577 views

PI Controller with XLSEMI4016 Buck Converter, unstable VFB seen

I have the following circuit set up to control VOUT (labelled SENSE on my Excel test results). Note that the node between REXT, POT, and R_B is called VFB. It goes to the FB pin of the XL4016 chip, ...
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75 views

Frequency domain representation

I'm studying the space-state representation and I'm not understanding a simple situation that I created. I created the following system, on the frequency domain: By writing the time domain ...
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1answer
75 views

Control Systems - State equations

I'm starting to learn about the state-space representation and i'm facing some difficulties. Suppose we have a system with connected blocks, like the one below: where Sometimes we want to choose ...
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1answer
76 views

Interpretation of block diagram for proportional feedback system with respect to time

Suppose we have a proportional feedback and that the system is modelled by a block diagram i.e where C is a constant. Do we think about this as a signal "moving" in time around this loop or is the ...
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1answer
780 views

Understanding the role of Pole zeros cancellation from the definition of stability

I have encountered the following theorem in a book. According to me, I can get an asymptotically stable system even if cancellations exist for the unstable poles. my example, Then Why does this book ...
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1answer
691 views

FOC current control autotuning PI Controller for BLDC Motors

I try to understand, how the guys from odrive tuned the current control PI parameters for Field Oriented Control: https://github.com/madcowswe/ODrive/blob/master/Firmware/MotorControl/low_level.c In ...
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61 views

Obtaining the analytical expression using the state transformation matrix

I am trying to derive the analytical expression in the box below. T is the state transformation matrix. x_dot=A*x(t) is a second order linear system. A has 2 distinct eigenvalues s1 and s2 and ...
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313 views

Why gain crossover frequency must be lower than phase crossover frequency for stable systems?

As far as I understood from here, phase margin means the amount of phase that needs to be added in order to coincide with 0 db gain and -180 degrees phase. Likewise for the gain margin it means means ...
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2answers
63 views

limits of performance

I am trying to understand a topic on limits of performance. So there is a delay of tau between input and output so the transfer function becomes G(s)*e^-(tau *s). I am unable to understand the ...
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2answers
422 views

Signal Flow Graph Problem

I am confused with the above problem. I have shown my attempt. I doubt the equation x1 = x1 + u. Please help me with this problem.
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1answer
440 views

State Model Representation of RLC network

I am confused with the above problem. Should I take a new state variable for rightmost capacitor or 3 variables are sufficient? Please help me in writing the state space equations.
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49 views

How to derive the Tf of an amplifier from its datasheet?

I am designing a control system, where the forward path has an amplifier in Howland's current pump configuration. I want to derive the TF of the current pump, and also take into consideration the ...
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1answer
306 views

subharmonic instability in average current mode control

The Control Loop Cookbook from TI explained about sub-harmonic oscillation as below. I am really confused by the part "cross over each other at their points of intersection". This is probably due ...
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2answers
701 views

Should the error term of PID be normalized?

By "normalized", I mean +/-1 ~= the maximum error the system can reasonably be expected to experience, or divided by the setpoint. Background: I am working on a PID controller for an SSR heater ...
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2answers
138 views

Can we think of an impedance or an admittance as a case for a transfer function?

We define impedance as the complex ratio of potential (voltage) over flow (current). We can describe it as how much a system "impedes" the flow according to a potential applied to it. But wouldn't it ...
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3answers
313 views

why large signal can make a conditionally stable system unstable?

This image below is from this TI cookbook. Please look at the red box. Question: why large signal can make a conditionally stable system unstable?
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465 views

Stability of a BIBO transfer function

Why is this transfer function unstable? The poles are \$0\$ and \$-4\$, so they are in the negative half-plane, theoretically it was to be stable. Can anyone explain to me what makes it unstable? $$G(...
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4answers
344 views

Effects of feedback

After doing some exercises in control theory I realized that one don't really need feedback to fulfill a lot of specifications. One could in principal introduce a controller giving us stability etc ...
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1answer
150 views

Difference between compensation and using a PID contoller?

I have a hard time understanding the differnce between the two techniques that are introduces in my textbook, a PID controller and Lead/Lag compensation. Ultimately we add a new box to our "loop" and ...
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0answers
81 views

tracking error state space, linear control example

I am trying to understand a detail from an example, from the control textbook Slotine and Li (1991) "Applied Nonlinear Control", Prentice-Hall, Example 6.4, pag. 220. A linear system is given: $$\...
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2answers
294 views

Benefits of higher order low pass in a negative feedback loop

Let \$G(s) = \frac{Y(s)}{R(s)}\$ be the loop gain of a negative feedback loop system. For example a system like this, where Y(s) and R(s) are the laplace transformed functions y(t) and r(t): ...
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136 views

Isolated buck H bridge control system design

Any references on how to go about modelling an AC/DC mains isolated H bridge buck converter in s or z domain? All the current resources online point to modelling buck converter with a single switch ...
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2answers
211 views

Why is this system stable?

I was given the system defined by the open-loop transfer function: \$L(s)=\frac{5(s^2+1.4s+1)}{(s-1)^2}\$ I was told to use the Nyquist criterion to determine stability. Examining the Nyquist plot ...
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1answer
191 views

What's the best starting point for rotor angle estimation for FOC?

I'm driving a BLDC motor with FOC. Right now, I have Space Vector modulation working, where I can give it a magnitude and an angle, and the algorithm will drop the right values into three PWM ...
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1answer
210 views

Ringing NOT at crossover frequency

Assume I have a system with open-loop gain G = (s+1)^2/s^3. This system has a negative feedback with feedback factor 1. I plot the open-loop gain by Bode and see that the phase margin Pm = 21.3877 at ...
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0answers
63 views

Nonlinear system general representation

I am fairly new with non linear systems. I understand that a general representation of a nonlinear system is: $$ \dot{x} = f(x) + g(x)\cdot u $$ where \$x\$ is the state variable, and \$u\$ the input....
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3answers
293 views

Is a decoupling capacitor theoretically required across the supply pins of a Hall sensor?

I am using the Hall-effect sensor OPTEK 3075S to ensure every step commanded to a stepper motor is executed. In the datasheet, they recommend connecting a 100nF capacitor across he input pins for "...
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1answer
78 views

Characterizing a magnetic levitiation system

I've been banging my head on this project for a while and need some guidance. It is a magnetic levitation device that is used in control theory class. I've never taken the class so have been trying to ...
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59 views

What to do with PI feedback value

I've been studying and trying to implement a PI feedback controller for a BLDC. Right now, just to unit test the code for the PI controller, I'm driving two phases with a PWM signal on a MOSFET ...
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2answers
3k views

Using of matrices in simulink block diagrams

All simulations I've done in simulink as yet have not matrix in their block diagram like the following picture : and they have block diagram structure like : for simulating a system that has ...
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3answers
114 views

Reduce time to stable value in PID

I am working with PID controlled temperature controller (SELEC TC544) . I have set P = 5 / I = 0 / D = 3. System get long time to stable at my set point. How to reduce that time?
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4answers
591 views

Control loop for finding maximum value [closed]

I'm trying to build a control system which I control variable x with a feedback y, goal is to find the maximum value of ...
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2answers
975 views

Controlling a dc-motor by keeping electrical power input constant

I have seen dc-motors controlled by current control and rpm control. As I understand it, one could use a PWM for example to control the mean current of a motor while measuring it and therefore keeping ...
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1answer
70 views

Control Systems

How to solve the following question? For a unity feedback control system with a forward-path transfer function G(s)=16/s(s+a), design the value of 'a' to yield a closed-loop step response that has 5% ...

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