What is Control system: Definition and 103 Discussions

A control system manages, commands, directs, or regulates the behavior of other devices or systems using control loops. It can range from a single home heating controller using a thermostat controlling a domestic boiler to large industrial control systems which are used for controlling processes or machines.
For continuously modulated control, a feedback controller is used to automatically control a process or operation. The control system compares the value or status of the process variable (PV) being controlled with the desired value or setpoint (SP), and applies the difference as a control signal to bring the process variable output of the plant to the same value as the setpoint.
For sequential and combinational logic, software logic, such as in a programmable logic controller, is used.

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  1. Gunter1977

    Engineering Control System mass spring damper

    Hello everybody I have a question about my control system, and I've included a diagram for reference. In the diagram below, I've illustrated three different control schemes using Simulink. The first scheme represents a PI controller for a mass-spring-damper system, which I understand well. It...
  2. P

    Engineering How do I use Simulink to create a control system with a 2nd order ODE?

    Equation: , where matrix D, C, G and F can be represented by I'm supposed to design a control system that looks like this: I am given that the dynamic model = fcn(D,C,G,dq) where the dq is the same as 𝑞̇ and d2q in the diagram is the same 𝑞̈. The default initial value of [𝑞(0), 𝑞̇(0)] is...
  3. K

    Engineering Analyzing the Nyquist Curve for a 5th Order System

    The Nyquist curve for a fifth order system with transfer function G(s) is given in the attached photo. Here we have plotted G(iω) for both positive and negative frequencies ω. The transfer function G(s) has no poles or zeros strictly on the right side of the imaginary axis Point −1 is marked...
  4. zeljkodj2000

    Engineering What are the job prospects for a control systems or electric power engineer?

    Hello, I am a first year student at the Faculty of Electronics in Serbia. In October, I have to choose the direction, I am hesitant between control system(automation) and electric power. What should I choose, what is more promising, where are the higher salaries...
  5. PainterGuy

    Does every control system contain an integrator?

    Hi, Let's call the box in green a plant. Does every plant consist of an integrator? It has to because when \overset{\cdot }{x}(t) passes through the green box, it becomes x(t). It's an operation of integrator; integrator converts the derivative back to the variable. Could you please guide me?
  6. Jason-Li

    Engineering Proportional plus derivative controller

    Hello, There is a thread related to this question however it was marked correct but doesn't look correct to me? https://www.physicsforums.com/threads/step-change-in-a-proportional-plus-integral-controller.961180/ I think I have it but it is quite different to other answers I have seen? I...
  7. Jason-Li

    Engineering Disturbance in a proportional control system

    Hello, I found an old thread related to this question but it doesn't look correct to me so was looking for some guidance. I have equated Qo = (Q2+Q1*G) / (1+H*G) I did this by rearranging Qo=Q2+G(Q1-Q0*H) I then went on to the calculations and found before step disturbance: Qo=...
  8. Jason-Li

    Why Does Increasing G in a Control Loop Cause Vo/Vi to Approach Unity?

    Hi all Physics Forum User, I am again coming to you to ask for help. For the above question I can't make sense of how a larger G will cause Vo/Vi to approach 1. For this I'll call Vo=V and Vi=I As can be seen from the control loop B = A*H and V = B*K hence V = A*H*K Also A = I - C and...
  9. Y

    Engineering Equation for a DC motor driving an arm

  10. N

    Robust control system calculations

    can i solve this problem i didnt go university due to Covid-19
  11. engnrshyckh

    Engineering Control system damping ratio

    I don't know how to calclute error in derivative for daming ratio of 0.5
  12. engnrshyckh

    Engineering Discover the Stability of the System through a Visualization | Learn More

    See the picture I am stuck at 12(1+2k)=0 So k=-1/2 for stability k must have value greater the - 1/2 which means there will no sign changes in rooth array and equation represents a stable system
  13. hdp12

    Help with a control system for a hydroelectric tank

    Hello there, please help if you are able.. So we have a tank with input volumetric flow and output volumetric flow The system is controlled by the height of water in the tank h(t) = hdes + (√h(t))*(-A2*(√2g) / A1) - h'(t) I am trying to find a transfer function for this system but I do not...
  14. J

    Proportional control system: Calculating the change in offset

    Homework Statement I'm having trouble worki out the transfer function of the block. Whats confusing me is the input of O2 input of 50. If that wasn't there I know the transfer function would be Oo/Oi=G/1+GH. Homework EquationsThe Attempt at a Solution
  15. F

    Stability of singular points in a discrete control system

    Homework Statement Give an example of a non-linear discrete-time system of the form x1(k + 1) = f1(x1(k), x2(k)) x2(k + 1) = f2(x1(k), x2(k)) With precisely four singular points, two of which are unstable, and two other singular points which are asymptotically stable. Homework Equations J =...
  16. J

    Find out transfer function in control system

    Homework Statement Homework Equations Using Laplace TF = C (s) / R (s) The Attempt at a Solution Laplacing the equation: 3s C(s) + C(s) = R(s) e-3s So C(s) / R(s) = e-3s / (1 + 3s) Book answer is B I know ramp input is At. Do I laplace it as: A/s2? I'm not sure where I'm wrong
  17. M

    What is speed of response of a control system

    Homework Statement In a report I am asked to assess the speed of response of various systems, however I am not exactly sure what this means, be great if someone could explain The Attempt at a Solution Step response plots were produced for each simulation and MATLAB was used to assign...
  18. S

    Fourier Series Expansion

    Homework Statement There is a sawtooth function with u(t)=t-π. Find the Fourier Series expansion in the form of a0 + ∑αkcos(kt) + βksin(kt) Homework Equations a0 = ... αk = ... βk = ... The Attempt at a Solution After solving for a0, ak, and bk, I found that a0=0, ak=0, and bk=-2/k...
  19. J

    Compensator Design in system control

    Hello, in my final project for System Control i have been stuck for some time on this following task What i cannot figure out is how to make all these condition work at the same time. When I tried designing a PD controller in sisotool or MATLAB for the i and ii part it worked but i couldn't...
  20. J

    Control System: Find the Transfer Function From Block Diagram

    Homework Statement Homework Equations To find Ca / Rb we take Ra = 0 --- is this right? I used mason's formula P1 = -G2 G1 H1 Loop = G1, G2, -H1, -H2 Using Mason's Gain we get: Delta1 = 1 Delta = 1 - G1G2H1H2 Using Mason's Gain TF = -G1G2H1 Divided by ( 1 - G1G2H1H2) But substituting the...
  21. Abdul Wali

    Design of High Pass filter to eliminate an instability in my control system

    HI, i have a first order controller (ts/ks+k) which contain some oscillations and its settling time is very huge, i wanted the controller to have settling time of 10seconds and remove the oscillations. in order to remove the noise and get the expected settling time i added a filter ( s/cs+1)...
  22. N

    MATLAB I with matlab designing a steady state feedback H2 control system

    Hi everyone. I'm designing a steady state feedback H2 control system. Actually, my major is tribology and I have no experience in designing control system. So it is really big problem for me. Anyway, this is my simple model of tribometer which applies normal load on the surface. (is it...
  23. S

    Understanding Total Gain and Phase Angle in Closed Loop Control Systems

    Homework Statement A closed loop control system has three components, Controller, Process, and Measuring System. Each has it's own gain and phase angle. I understand how to find the total of the gain but I'm unsure as to how to find the total phase angle? Homework Equations Total Gain=...
  24. T

    Power System Simulation Program for To Control System Freque

    Hello. I need to simulate a power system including conventional generators, loads and wind farm. I want to measure system frequency and voltage esspecially. According to these values for any kind unwanted of voltage and frequency changes circuit breaker should be opened and wind farm will be...
  25. K

    Steady state error- Control system

    Hello, I have a question about steady state error. how can we get to the C? I think it has to be Ea(G1+D)G2=C which gives(R-NH)(G1+D)G2 / (1+(G1+D)G2H)=C
  26. W

    Document Control System, How Effective?

    Hi! We have been having problems in controlling our documents. We always have a hard time identifying who made mistakes in the details encoded. I heard about this document control system. How effective is this? I want to hear from users before I suggest it to our boss. Thanks for your time.
  27. srinaath

    I Why do we linearise a non linear system

    I am stuck with the concept of linearising the non-linear system...what i thought was...non-linear systems are defined by differential equations which is difficult to solve, hence we linearise them to make the differential equation look like a algebraic equation...am i right ?...or is there...
  28. srinaath

    Queries in control system

    i have few queries regarding control system in electrical engineering... 1)transfer function is defined for linear system ? why is that so... 2)why transfer function is defined with zero initial condition...why not with initial condition
  29. D

    2nd Order Control system PD controller

    Hi, This question on PD control is from a practice quiz. 1. Homework Statement If you can't see it- the question asks to find values for Kp and Kd such that the system achieves 5% OS and has a settling time Ts of 3s. Cs = 3 Cd = 2 m = 5Homework Equations ω_n^2/(s^2 + 2ζw_n + ω_n^2) - 2nd...
  30. cnh1995

    Control System Doubt: Voltage Transfer Function of Resistor

    Consider the following circuit with Vs=1V, R=1Ω and C=1F. The voltage transfer function of the resistor can be written as Vr(s)/Vs(s)=s/(s+1). Now I understand s is complex frequency and at s=∞ the transfer function becomes unity since capacitor acts as a short and Vs=Vr. What I don't...
  31. T

    Water tank level control system

    I have a project to build a water level control system. Basically I will have two sensor probes one connected near the bottom and the other near the top. When the water level goes below the bottom sensor it will trigger a pump to pump water back into the tank until it reaches the top sensor...
  32. U

    Can You Change the Damping Ratio of a Second Order Linear System Easily?

    How to change the damping ratio of dynamical system if it is say for example robotic arm? Can it be changed directly or one need to change natural freqvancy? by which it will automatically change.
  33. L

    Nuclear power plant - Control system

    Hi guys, I do apologize if this thread is in the incorrect place.. Long story short, I'm doing a university project based on developing an AI to control the power plant energy output. From my research so far, I've concluded that the control rods control the fission rate. The problem is, I for...
  34. David Gin

    Automated Chiller Temperature Control System

    Hi All, I'm working on an automated chiller control system for final year project. It is a logic control that automatically set the chill water supply temperature based on current demand load and the chillers performance curve to achieve the best efficiency COP for the system. For a variable...
  35. vinicius0197

    Engineering Job Market for Control Engineers?

    I've been giving a look at some of the electives in my college - I'm a student of MechE - and became interested in Control Systems, specially after I borrowed some books in the subject in the library and read a little bit more about it. I wonder how big is the field of application of this...
  36. Y

    State-space modeling of a control system

    Homework Statement [/B] Here is the problem: And this is the system in question: Homework Equations G(s) = θ_0(s)/θ_i(s) = output/input (open-loop transfer function) The Attempt at a Solution I've been staring at this problem and looking through my textbook for over an hour but...

    Linear control system controllability

    Hello, In a linear system of the form $$\dot{x}=Ax+Bu$$ and $$y=Cx$$ we can use state feedback control $$u=Kx$$ assuming we know the state, or can observe it, to control the system if (A,B) is controllable (all states are reachable). How does the theory on controllability apply to output...
  38. F

    Design of Experiments Ideas - Control Systems?

    Hi everyone, I'm taking a Design of Experiments class which is focused on statistically designed experiments. I'm a bit lost for project ideas and this is my first graduate class. Would anyone have any ideas for an experiment that would have at least controllable factors that might have...
  39. Y

    Modeling a Control System using Transfer Functions

    Homework Statement [/B] Homework Equations Listed under 2.1 in the image above. This is the only relevant equation that I'm aware of, but I'm almost sure that there is something else I need to know before I can solve the problem. The Attempt at a Solution I tried solving for the...
  40. G

    Can a car's reaction to gas pedal be said to be stable ?

    As per control theory, if a bounded input produces a bounded output then a system can be said to be stable. So assuming that I press my cars gas pedal such that it reaches a fixed position, then the reaction of my car would be to reach a corresponding velocity, and assuming the road to be even...
  41. S

    Inverse Discrete Laplace Transform

    Hi, I have an idea which when tested looks like its clearly flawed. I am hoping someone can tell me where my procedure is flawed, or point me to some other theory that has already done something similar. The first two are the laplace transform. The third line is the Fourier Transform. The...
  42. K

    Poles/Zeros of a Control System

    ME student here. I have managed to get through two control theory courses at my university, which I have managed to get A+s in despite having no idea why I am doing all of it. I understand the math (i.e. why RHP poles are not good for the system stability) but do not understand what any of it...
  43. E

    Modeling Ball and Spinning System

    How should I go about modelling a ball and spinning beam system in matlab? It's similar to the ball and beam control system except the beam spins like a propeller so the control system has to account for the centripetal force. Any reference papers?
  44. K

    Step response time of control system

    Homework Statement I'm having a slight problem with the question below. A temperature control process has a first-order response with a step response time of 12 seconds. In selecting a temperature sensor for the control system for the process, for what maximum value of sensor time-constant...
  45. O

    Write function for control system block

    Homework Statement Write function for control system block Homework Equations The Attempt at a Solution 4 and D are parallel so we add them : I am stucking in the simplication of this block Should I group these elements to a function called w[nT], so...
  46. N

    Discrete Control System with Time Delay

    Hello, I am trying to develop a software control algorithm to compensate for oscillator imperfections/frequency drift. I have a NTP server which I can get a pretty good estimation (@1Hz) of the "true" time and compare it to my system's time. I can differentiate the offset-error to calculate...
  47. K

    Control System Gain design problem

    Is it possible for a Type 0 Open Loop Transfer function to have 0 steady state error? Context - Control System Gain design to meet a certain steady state error specification. The open loop T.F - G(s)=3/(s^2 +4s+3) (This is type 0 (n=0)) The closed loop T.F is Gc(s)=G(s)/(1+KG(s)), But my problem...
  48. S

    Relay Control System (Normally Open,Held close)

    Hi guys, currently i am stuck with the limit switches in the sequential control circuit. the Normally open,heldclosed, Normally closed,held open , normally closed and normnally open. Let's say if bo is NO,HC. so the switch will be normally open then once bo is actuated then the switch will...
  49. 3

    Control System Design Homework Help

    Homework Statement Attached below. Homework Equations How can I know I got the correct set of parameter in step 5. I did everything using MATLAB but couldn't figure out how to get the right value of the zero. The Attempt at a Solution Attached below.