# 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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### What is noise gain, really? And how is it determined in the general case?

UPDATE: This question triggered what might fairly be called a research obsession for me. I've gotten pretty close to the bottom of it I think, I've posted my findings as an answer below. There was a ...
11k views

### How to learn PID Control?

I want to learn PID (Proportional–Integral–Derivative) control mainly for temperature. I would like to learn preferably through an easy project to do. Could you please recommend something which ...
8k views

### Why only sine waves?

I have already read a few EE texts where a sine wave is often seen. Why is the sine wave often used as a test function for a circuit or a system? Why don't we use any other signal instead of sine? ...
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### System Modeling for Control Systems

After taking classes in control theory as an undergraduate, I ended up not using them at all after I graduated. I've started to fix that by starting a hobby project in controls. My textbooks are ...
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### Do working electrical engineers in circuit design ever use textbook formulas for rise time, peak time, settling time, etc

This is a very general question. In undergrad electrical engineering, students are usually taught about step response to LC (second order) circuits. This is usually when many parameters are ...
11k views

### How to use measured step response to tune control system

How does one use a measured step response to tune either a PID or convolution control scheme? Inspired by this answer*, I'm interested a more detailed explanation of how to implement a control system ...
3k views

### PID algorithm: how to account for fast input value changes after a long delay

I am trying to implement a basic PID algorithm on an Arduino Leonardo to mix hot and cold tap water using servo-controlled valves. The goal is to hold the temperature as close to a setpoint as ...
2k views

### 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 ...
15k views

### How to implement a self tuning PID-like Controller

I am trying to write a micro-controller program for controlling temperature in a system with the following characteristics: output can only be On or Off, with fixed cycle frequencies (~2-10 per hour) ...
2k views

I'm trying to control a motorized fader (linear slide potentiometer) using an Arduino. PID control gives good results for "jumping" to a specific target position, but tracking ramps is a problem, it's ...
3k views

### 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 ...
41k views

### Gain margin and Phase Margin Physical Meaning

I have been trying to understand the physical concept of Gain and Phase Margin. What I understand about this is that a relative comparison around the critical point $(-1,0)$, which when converted ...
9k views

### Conditional stability

I'm learning about op-amps and feedback and how feedback affects their stability. I've been reading about gain and phase margin and their uses when I came across this: I don't quite understand how ...
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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 ...
2k views

### How does control theory apply to my real-world processor-controlled boost converter?

I have a limited understanding of control theory. I dealt with poles and zeroes and transfer functions in school. I've implemented several microprocessor-based control schemes for DC/DC converters. ...
96k views

### What is a “dry contact input”?

I'm a PC software guy, a newbie to electronics. Recently, I've got a project in which I need to source for a DAQ that can provide dry contact inputs to an interfacing digital output controller. The ...
1k views

### PID Control Loops with large and unpredictable anomalies

Short Question Is there a common way to handle very large anomalies (order of magnitude) within an otherwise uniform control region? Background I am working on a control algorithm that drives a ...
10k views

### Kinetis vs STM32

I'm looking into a new industrial controls application, and from my searches I have narrowed it down to 2 microcontrollers that look to fit the application well. The STM32 and the Kinetis. They both ...
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### Finding the Transfer Function of Spring Mass Damper System

I have been going through Ogata Modern Control Engineering book and working through several exercises to improve my understanding of basic control principles. I came across the following example which ...
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### Conversion of PID controller components with state feedback into single transfer function and discrete state-space form

I've been wrestling with this problem for about a week now, as a part of a year-long project. We're designing a controller for a specific reactor based on a model. After looking at this for a while, I ...
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### Why is the frequency complex

When we take the Laplace transform of a function, why is the frequency (s) complex? I can not understand the significance of complex frequency. Please help or give some references.
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### 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 ...
2k views

### How to design controllers “properly”?

It may sound like the "easy way" to ask it here, but this question (along with a couple others I've posted which were more specific) is the result of years of research on the topic - on and off as it'...
8k 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 ...
20k views

### Building a temperature-controlled water bath

I want to build an accurate (±2 °C) water heater (sous vide) that heats water somewhere between 30-100 °C according to user input. Although I have an engineering background I have no ...
971 views

### The term Feed-forward and its meaning?

I am trying to understand the technical meaning of the term 'feed-forward', when and where it can be used and where it cannot be used? I have seen this term in various different areas. For example: ...
1k views

I'm currently designing an equivalent of the mass-spring-dashpot system, and during the design phase I realized I don't fully understand how PID controllers physically work. Below is an image, the ...
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### Can a DC motor with obstructed movement be damaged?

I am trying to build shades, which should roll up or down, controlled by a DC motor. This motor can only be turned on or off (1/0 to turn it on/off). Also, it should be noted that the microcontroller ...
390 views

### Meaning of an arrow in the control scheme

I cannot understand what the arrow that goes through "internal model" block mean? how can I interpret what does it do? What is the difference from any other "normal" arrow? (source: cam.ac.uk)
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### Control theory: is there any actual application for D in ABCD matrix?

Recall that a LTI state space of a dynamical system is given as: Is there any actual purpose for D in the output equation? If D was not zero, it would mean that the output is "directly" dependent ...
4k views

### Any open tool for graph plotting for determining PID tuning parameters?

I have gone through several PID implementations and its tuning tutorials, documents and all. The Best tuning tutorial was PID-without-a-PhD.pdf . But has not been of much help. I can say it works some....
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### Confusion in PID loop for the case of zero error?

I am already studying PID control and some how to some extent I have understood it except one main confusion. When the difference between reference input $r(t)$ and current output value $y(t)$ is ...
625 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 ...
1k 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 ...
2k views

### Why do digital controllers need A/D and D/A converters?

One of the questions in our final exam will be "Explain the need of A/D and D/A converters in digital controllers". I could not find the reason anywhere why the Plant part of a block diagram requires ...
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### Dimmer to bulb control

I need to control a bulb of 220V, with different intensity light levels. I've an Arduino Uno Board, which receives a variable voltage from a Light-to-voltage converter (TSL12S) (Like a photoresistance)...
462 views

### Confusion in block diagram of open loop and close loop control system?

I am studying Modern Control Systems, 11th edition, by Dorf and Bishop. On page 221 it first shows in fig4.7 open loop control system(the writer names it as open loop) and on page 222 close loop ...
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### How I can set up a transfer function of y = mx+c?

I have a system governed by the following relationship: $V_{OUT} = m * I_{IN} + 5$ I need to write a transfer function for the equation. Would anyone please give me some suggestion of how to ...
5k views

### deriving the transfer function given bode plot

I have been given the following question on finding the transfer function from the following bode plot I know that the transfer function should look like this H\left(jw\right)\:=\:\...
701 views

### 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 ...
2k views

### Type 2 compensation network

I'm working through the excellent text on SMPS design "Switching Power Supplies A to Z", by Sanjaya Maniktala. Right now I'm reading the section on the feedback loop and stabilization. As a first-...
1k views

### Circuit Analysis: Obtaining Close Loop OP - AMP Transfer function

Trying to figure out the Close Loop System transfer function of an op-amp, however the math isn't working out as it should. Circuit In question: simulate this circuit – Schematic created using ...
2k views

### How to mount electronics on a vehicle chassis safely

I want to implement a control system I designed for a light electric motorbike. I would like to mount it as professionally as possible on the chassis. It consists of a power system pcb and a SAMC21 ...
468 views

### M.S. Math to Engineering Ph.D : Mathematics in Electrical Engineering [closed]

I have two Bachelor's degrees. One is electrical engineering and the other one is mathematics. I am studying mathematics (partial differential equations) in the graduate school (Master course) now. ...
1k views

### 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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### What is meant by “plant” in control system?

What is meant by "plant" in control system? Does it also means systems like DC motor or it only includes large systems like chemical (fertilizer or cement) plant?
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### Why are there only PID controllers, no PIIIDDD (higher order) controllers?

Transfer function of a PID controller is: $I\cdot s + P+\dfrac{D}{s}$ Are there controllers like: $A\cdot s^2 + B\cdot s + C+\dfrac{D}{s} + \dfrac{E}{s^2}$ ? If so, are they common? Why do ...
308 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 ...
What's the definition of the undamped natural frequency? I've looked and I cannot find it. A second order system has the following transfer function  H(s) = \frac{A_o \omega_n^2}{s^2 + 2 \zeta \...