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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171 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
152 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
145 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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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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141 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
72 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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58 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
2k 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
111 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
405 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
831 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
63 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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164 views

What is the relationship between feedforward control and bandwidth?

This is a control theory question, but because there is no control theory stack exchange, I thought this was the closest appropriate location: I've been studying feedforward control system designs, ...
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3answers
308 views

Offsetting a differential amplifier to remove the need for a dual supply

I'm developing two similar circuits that will enable me to differentiate the X and Y coordinates from a segmented photo-diode (Four segments). These coordinates will be dependent upon the position of ...
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1answer
249 views

Characteristics of a DC motor control system

I am designing a DC motor controller model. I have a second order system so the step response oscillates and overshoots the final value somewhat. I have seen a lot of theory on calculating rise time,...
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73 views

State Space Model Basics

I have added the problem with its solution. I tried applying Mason's Gain Formula which led me to the same result and it should have as Transfer Function is unique. Is there a shorter way to get ...
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1answer
96 views

Control System Basics

I am really confused with the difference between steady state error and actuating error. My teacher gave the following notes on this topic and explained using 1 example. He said that there will be 2 ...
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1answer
85 views

Nyquist Plot - Control System Basics

If I have a G(s) plot. Can I draw 1+G(s) plot from it? If yes, then please give an example. If no then explain why?
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1answer
2k views

Why isn't derivative control used without proportional or integral control?

Why isn't derivative control used separately in industrial controller designs? One answer I read online was that derivative control is not used separately, i.e., without proportional (P) and integral ...
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1answer
178 views

Nonlinear time dependent equation in simulink [closed]

My question is about time varying nonlinear equations in simulating of them in simulink. in nonlinear time independent equations x,Dx,D^2(x) are made with multiple integral block like the picture in ...
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4answers
2k 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 \begin{equation} H\left(jw\right)\:=\:\...
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1answer
66 views

Syncing Multiple Motor Drivers

I have put together a 4-axis robot operated by brushed DC motors for a haptic feedback system. Unfortunately I am not well versed in robotic control systems so would really appreciate any advice you ...
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2answers
9k views

What is the difference between relative stability and absolute stability

Is there any difference between relative stability and absolute stability? Do all the control system analysis techniques (Root locus, Routh-Hurwitz, Nyquist, Bode plot) are able to find both ...
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1answer
68 views

What is the mathematical difference between a transfer function and a state transition matrix?

I do know what the difference in meaning is between a transfer function (output over the input) and a state transition matrix $\Phi$ (describes the unforced response of the system). Yet when looking ...
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2answers
367 views

How to determine the critical delay for a closed-loop system?

Using the open-loop transfer function we can easily determine its Nyquist plot, and from it we can get the critical gain such that the system is stable. Now, let's consider a system with delay \$t_d\$....
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122 views

Definition of minimal phase

Let us consider a linear time-invariant system. The term minimum phase is used for a system that has stable poles and stable zeros. A system is called nonminimal phase if it is not minimum phase. ...
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1answer
2k views

How to compute the sensitivity of this control system?

I am learning control systems on my own and am having some trouble understanding how Richard C. Dorf and Robert H. Bishop found \$S^{T}_{G}\$ in Modern Control Systems (12th edition): The problem: ...
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1answer
584 views

control systems - What is \$\det[sI-A]\$?

I am reading the 12th edition of "Modern Control Systems" from Richard C. Dorf and Robert H. Bishop which is about control systems. It is not totally clear to me how the author came up with the ...
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1answer
118 views

What to use in finding frequency response : \$G(s) \cdot H(s) \$ or \$ \dfrac{G(s)}{1 + G(s) \cdot H(s)}\$?

While studying frequency response of control systems, all of the sources I'm referring to is considering unity feedback system i. e. H(s) = 1 & drawing Bode plots and polar plots on basis of that. ...
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2answers
711 views

Polar plot of s/(1+(s*T))

The magnitude at w=0 comes out to be 0 (=1/infinity) , which is different from previous problems (they didn't have any zero) I've calculated, is this right? I guess it should be right (because G(s)...
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2answers
333 views

Mechanical time constant of PMDC Motor in starting and after switching off the supply is same or different?

In my MATLAB/SIMULINK model of the PMDC motor the mechanical time constant has same value in the case starting of motor and after switching off the supply but in experimental setup there is a ...
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1answer
73 views

Find the largest value of \$K_1\$ and \$K_2\$ for instability of the system

A cascade control system with proportional controller is shown below Theroritically the largest values of the gain K1,and K2 that can be set withot causing instability of the closed loop ...
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1answer
62 views

The system is not completely reachable, Is state x1 reachable from x0?

The system is $$ x(k+1)=\begin{bmatrix} 1 & 1 & 0 \\ 0 & 1 & 0 \\ 0 & 0 & 1 \end{bmatrix} x(k)+\begin{bmatrix} 0 \\ 1 \\ 1\end{bmatrix} u(k) \\ y(k) =\begin{...
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5answers
938 views

control systems - how to obtain the transfer function from this block diagram?

I am trying to find the transfer function for this basic block diagram According to the book I am reading I should be able to derive the transfer function (given in the image above) from the block ...
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1answer
363 views

DC gain from Nyquist Plot

In the solution they have given like this Here I did't get how they directly wrote DC gain 1? I solved like this \$GM=\frac{1}{\left |G(s)\right||H(s)|}\$ Here H(s)=1 From the plot GM=0.5 So G(...
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1answer
174 views

Reusing an old Acer screen [closed]

I broke the motherboard of an old Acer notebook, and as a part of my fiddling, I managed to get the screen (+webcam) off the rest of the body. It looks like this : Now, I have two cables going out ...
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0answers
109 views

How to calculate the value of compensation network of DC DC converter

I am designing a circuit to boost voltage from 5V to 9V.I came across various kind of Switch regulator from TI. I don't know how to calculate the R-C value of compensation network. Thanks in Advance.
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4answers
3k views

What is the difference between the forward transfer function and closed-loop transfer function?

We can define the forward transfer function as $$l(s)=g(s)r(s)$$ Thus, the closed-loop transfer function is $$h(s)=\frac{g(s)r(s)}{1+g(s)r(s)}$$ with \$g(s)r(s)\$ the multiplication between all the ...
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1answer
72 views

When supply fan VFD starts up it causes communication problems for my energy management controller

We have an energy management system that controls the air handlers for a building. I have one unit that when the supply fan VFD starts up it cause the unit controller to start having communication ...
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55 views

Find the gain \$K\$ at a point of given rootlocus?

From the given information i can write the transfer function as $$G(s)=\frac{384}{s(s+4)(s+8)}$$ now get the value of \$K\$ at \$s=-1.5+j1.5\$ which is in root locus the generalised TF can be ...
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1answer
232 views

Nyquist plot Phase Question

The above graph is pulled from the book "Automatic Control Systems" by Kuo. The subject loop transfer function is $$L(s)=\frac{K}{s(1+T_1s)}$$ or $$L(j\omega)=\frac{-jK(1-jT_1\omega)}{\omega(1+T_1^2\...
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1answer
68 views

Any transfer function has the same denominator 1+T

Sometime ago, I came across some theory saying that in a control loop any transfer functions such as ...
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2answers
1k views

How to find the intersection point in rootlocus diagram?

Question: Sketch the root locus for the open loop transfer function of a unity feedback control sytem given below and determine the value of K for \$\xi=0.5\$ \$G(s)=\frac{K}{s(s+1)(s+3)}\$ --...
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61 views

variable factors in Simulimk

In my simulation of Van der Pol equation in matlab, I need to have variable factors the same as shown in following picture but Simulink doesn't accept that. how I can solve this problem?
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3answers
1k views

Controller to increase phase or gain margin

I can't find any good sources on this one. The only textbook I have says nothing about it. I've been restricted to the use of some formulas given by our teacher which I don't understand why they ...
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1answer
137 views

Current controller: how to dampen resonance to increase bandwidth?

I need to design a +/-1.5A, 3kHz small-signal-bandwidth (absolute min, for 3° max phase and 1% max error on amplitude) current controller for a 20 Ohm 0.1H load with a +/-100V supply rail (the current ...
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3answers
1k views

Why do we do open loop analysis for closed loop system? Why cant we directly analyse closed loop system?

The intention to ask this question is that, just wanted to know the reason of breaking a loop for bode plot analysis
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3answers
3k views

Can a controller have a negative gain?

I'm working on a problem that involves a Ćuk converter. The question asks "find k_c (a gain for a controller) such that the system is marginally stable". So I got the properly space-state model with ...
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2answers
102 views

Replacement for DC Tachogenerator in hydroelectric control system

I a mechanical engineer working at a mission hospital where we have a relatively new (2013) hydroelectric power plant. The turbine has a speed sensor (DC Tachogenerator) that provides a voltage to a ...
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1answer
56 views

What are the Disadvantages of unnecessary increase in PID gains?

I read somewhere that if we increase the PID gains unnecessarily, it will cause more energy consumption of the controller and it will lead to noise and distortion in the practical. May someone please ...