The Stack Overflow podcast is back! Listen to an interview with our new CEO.

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.

Filter by
Sorted by
Tagged with
3
votes
2answers
988 views

How to determine the phase margin and transfer function of this bode plot?

I have some struggles to find the transfer function of this plot. We got the hint, that the "breaks" of slope can be assumed to be on vertical and horizontal lines. Also we should pay attention on the ...
1
vote
2answers
140 views

Meaning of the “pole” of a transfer function with time delay

I learned in basic control theory that we can determine the stability of an LTI system by the signs of the real part of the poles of its transfer function \$H(s)=\frac{N(s)}{D(s)}\$. For a rational ...
4
votes
4answers
204 views

PID Tuning Issue

I'm having issues tuning a PID controller - specifically the I-term. First - here's a little info about my system: I'm heating a coil (R ~= 1.8 Ohms) to 750°F. My power delivery system is working ...
0
votes
1answer
365 views

Solving the differential equation in control system engineering

While I am continuing my studies of the Norman S. Nise book about Control System Engineering, and while trying to solve exercises of chapter 1, I noticed that I am out of the scope of solving ...
7
votes
3answers
479 views

Block diagrams can be different and still works for the same system?

I am an telecommunications engineer who is working now as a programmer. At university we took a class on digital filters, Laplace transformation and working in the frequency and time domain. At the ...
3
votes
1answer
285 views

PID tuning without plant model

My aim is to keep temperature constant at a certain place. I don't have a mathematical model of the plant. Currently, PID is used with some fixed Kp, Ki, and Kd, and I want to optimize these ...
2
votes
3answers
2k views

Should cable shields be connected to earth ground, or to power supply negative?

I'm working on a PLC cabinet, and I'm wondering whether I should hook cable shields to earth ground, or to the power supply negative. I checked and the power supply DC output is isolated. There's no ...
0
votes
1answer
965 views

Three-phase thyristor rectifier - Minimum firing angle

Why is a minimum firing angle (>0, usually 5-15°) defined for three-phase thyristor rectifier? I would like a technical explanation. Thanks
0
votes
1answer
66 views

Why is this derivation of the unit step function in the Z-domain valid?

This source states that the unit step function in the Z-domain is \$\frac{z}{z-1}\$. However, in its derivation it states \$\sum_{k=0}^{\infty} z^{-k} = \frac{z}{z-1}\$. But doesn't that last ...
1
vote
2answers
368 views

Finding the transfer function of an non-inverting audio op-amp

I am just doing some independent re-search for myself in audio amplifier (CHIP AMPS) such as the LM1875. I want to learn more about how to compensate for audio chip amps and how their bode plot ...
0
votes
1answer
42 views

What's oscillatory instability in the delay differential equations?

Does DDE’s stability depend on forcing term and ODE’s stability does not depend?If yes, then is frequency analysis of stability applicable only to DDE and not ODE? In control systems, we study ...
0
votes
1answer
50 views

Control system error based on differential process value

In a basic PID controller, you measure the process value y (such as temperature) directly; then the error e is equal to the difference between the process value and the set point r. The error feeds a ...
0
votes
1answer
176 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 ...
0
votes
4answers
1k 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 ...
2
votes
2answers
125 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, ...
1
vote
1answer
58 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. ...
0
votes
2answers
88 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 ...
0
votes
1answer
114 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 ...
0
votes
0answers
71 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 ...
5
votes
3answers
499 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 ...
-1
votes
2answers
61 views

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 ...
2
votes
1answer
111 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 ...
1
vote
2answers
122 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 ...
1
vote
2answers
481 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}}...
0
votes
1answer
100 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. ...
7
votes
4answers
6k views

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 ...
3
votes
4answers
408 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 ...
1
vote
1answer
98 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.
0
votes
0answers
368 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, ...
0
votes
1answer
73 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 ...
0
votes
1answer
73 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 ...
1
vote
1answer
74 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 ...
1
vote
1answer
603 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 ...
0
votes
1answer
385 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 ...
0
votes
0answers
57 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 ...
0
votes
0answers
162 views

Why does the gain and phase margin need to be positive for a stable system?

As far as I understood, 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 the amount ...
1
vote
2answers
62 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 ...
1
vote
2answers
339 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.
1
vote
1answer
286 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.
0
votes
0answers
48 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 ...
0
votes
1answer
210 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 ...
2
votes
2answers
485 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 ...
0
votes
2answers
81 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 ...
2
votes
3answers
281 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?
0
votes
3answers
385 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(...
1
vote
4answers
340 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 ...
2
votes
1answer
127 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 ...
2
votes
0answers
74 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: $$\...
0
votes
2answers
201 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): ...
0
votes
2answers
120 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 ...