# 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.

1,175 questions
Filter by
Sorted by
Tagged with
40 views

### Confusion regarding formula of positive feedback

Please check the attached snap especially the yellow highlighted "plus" sign . According to my understanding it should be "negative" because it is case of positve feedback as shown ...
78 views

### How can I control the power through a resistive load [closed]

I have a project where I need to control the power through a resistive load. The project consists of controlling the temperature on the outlet of a pipe, the inlet will flow at a velocity of 2.2m/s ...
35 views

### Order of Complexity

Generally, number of independent state variables (order of complexity of a system) is equal to the number of reactive elements in RLC network. But, if capacitor and voltage source loops are present ...
41 views

### What is the standard form for writing the second order transfer function for Input impedance?

When writing the transfer function for a system, the Characteristic equation in the denominator which carries information about the poles of the system is equated with the standard second order ...
89 views

### How to get the transfer function out of a Bode Curve on a datasheet?

I am trying to find the transfer function of AMC1350 out of its datasheet. I dont have any information about which degree of a lowpass filter or what kind it has. DC gain is 2/5. Cutoff frequency is ...
37 views

### How can I explain contradictory damping performance between linear and nonlinear systems?

I have a 3rd order nonlinear dynamical system, representing a power system. After linearizing the system, it turns out that by increasing the parameter L_g, damping is reduced and thus the overshoot ...
30 views

### Nyquist Plot Stability with Angle

I don't understand the solution done here. The Nyquist criteria I know is Z=N+P and I don't see the relation with this solution. Where do the angles come from?
51 views

### The center and radius of root locus

With this opened-loop transfer function, \begin{align*} L(s) & = \dfrac{K(s+2)}{s(s+1)} \end{align*} I would like to plot the root locus of this system. Based on the textbook,...
136 views

### Negative phase margin and misconception of the point of instability in negative feedback control loops

Prelude Consider a canonical block diagram of a negative feedback loop with gain $K$, plant transfer function $G(s)$ and feedback transfer function $H(s)$: - Regardless of what functions K, G, ...
57 views

### Integral Controller design

For this system, what method do I use to select a value of Ki? Gh and Gt are first-order blocks with time constants Th and Tt-
52 views

### Stuck during designing a PI Controller

I'm trying to design a PI Controller on the basis of this paper: "Design of robust PI control systems based on sensitivity analysis and genetic algorithms." by Jau-Woei Perng • Shan-Chang ...
87 views

### State space representation of RLC circuit [closed]

Express the circuit in state space equations, the output is V2. I have tried defining the state variables but got stuck with the differential equations.
96 views

### Modelling the PID controller for a Buck Converter from a given schematic

I followed a document to implement a PID controller for a Si MOSFET based buck converter as the traditional multistep analog PID converter was not giving any good results for some reason. The document ...
50 views

### Find the range of variables based on the steady-state response

I have a transfer function as below: $$G(s) = \dfrac{s(s+2)}{s^2+(b+2)s+ab}$$ Now with input as $$u(t) = \sin{t}$$ The maximum steady-state response of y(t) is less than 1, I would like to ...
1 vote
142 views

### Deriving transfer function from nyquist plot

I am given a half Nyquist plot as below The dashed line stands for the asymptote of the locus and the poles are 0 or negative at real parts, besides there is no double root in the transfer function. ...
38 views

### Is it feasible to model a CMOS inverter as a control system?

I have some knowledge of basic control theory from a course I took this summer and I'd like to use it to model CMOS circuits for an independent study project with one of my EE professors this upcoming ...
1 vote
46 views

### Finding transfer function in a balance state

I have an ODE that looks like this: $$\dfrac{d^2y(t)}{dt^2} + 2\sin{y(t)} = u(t)$$ Taking u as input and y as output, considering the balance state with $$u(t) = \bar{u}, y(t) = \bar{y}$$ ...
1 vote
123 views

1 vote
45 views

### Locating variables a and b in a phase lead compensation system

I have a block diagram that looks like this: I am asked to find the maximum angular frequency of the phase lead compensation, thus, in order to locate values a and b, I first find the maximum phase ...
111 views

### Finding K values for all poles of real parts are less than -2

I have an open loop transfer function with k > 0 as below: $$L(s) = \dfrac{k}{s(s^2+8s+25)}$$ Now for the closed loop transfer function, I would like to find the k value which makes all the ...
79 views

### Ziegler–Nichols method of PID auto tuning

I am working on a problem where I need to implement auto tuning PID control using Ziegler–Nichols method. Basically I want to control temperature using it. The PID has to be implemented with the ...
28 views

### Control systems and causality

Given H(s) is LTI and causal, can I say that D(s)=H(s)/(1+H(s)) is causal too? Do I need to satisfy any other conditions?
88 views

### Barkhausen Stability Criterion

Here is what the theory said : Here is the Barkhausen stability criterion : The loop gain is equal to unity in absolute magnitude, that is, $$|\beta A|= 1$$ and the phase shift around the loop is ...
53 views

### PID output to motor rpm

I am working on my project "Control design for tilt rotor." The UAV has 4 tilt rotors and I am using PID to controller for position and attitude control (outer and inner loop). ...
33 views

### Barkhausen stability criterion and poles location in s domain

For studying stability, I am actually working with 2 methods : Here is the Barkhausen stability criterion : The loop gain is equal to unity in absolute magnitude, that is, $$|\beta A|= 1$$ and the ...
1 vote
51 views

### Entire Complex Function for dynamical systems

I am working on my master Thesis and I was going through the 1966 Thesis by K. P. Sriram. Here, the author computes the switching curves for minimum time control of some "famous" systems ...
1 vote
87 views

### What is the Z transform of the discrete PI control model？

I have a discreate PI controller implemented in stm32 MCU, it has the following form: $$PI=K_p\cdot[r(t_i)-y(t_i)] + (K_I)\cdot\sum_{n=0}^{i}[r(t_n)-y(t_n)]\cdot\Delta t$$ where $r(t_i)$ is the ...
1 vote
96 views

### Does the idea of bandwidth make sense for a system with an infinite DC gain?

I'm thinking specifically of systems with ideal PID controllers. The transfer function will always have an integrator term, which, if I understand correctly, means it will always have infinite DC ...
110 views

### Variable Reference point in control system

In some control systems that my be composed of cascaded control loops, the reference signal of an inner loop may come from the output of the outer loop. Example in DC motor control, we have an inner ...
102 views

### How to design a PI/PID controller with a given bandwidth and phase margin?

I've read the article, Introduction: PID Controller Design, which explained really well the effect each branch of the controller has on the rise time, settling time, overshoot, and error, which gives ...
583 views

### What's the point of the proportional branch in a PI controller?

I just watched this MatLab video on the basics of how PI/PID controllers work and for the most part it makes sense. They started with an example with just a P controller and showed that, while it ...
518 views

### What does it mean that an integrator has an infinite DC gain?

I mean, I get that, in the ideal case, $G\rightarrow \infty \text{ as } s \rightarrow 0$, but it doesn't make sense for a physical device to be able to amplify a signal to an arbitrarily large value,...
78 views

### How do I find gain values between decades on asymptotic Bode plots?

I was doing some past exams for my control theory final and came across a question with the following asymptotic Bode plot given: In order to solve for $\omega_c$, I need to essentially find the ...
87 views

### Proportional control: steady state explanation

In this video, a scenario is given to show the failings of using solely proportional control. Consider a drone that must be made to hover at an altitude of 100m. The RPM required to hover the drone is ...
690 views

### Why is the transfer function of this circuit first order, when it has two energy storage elements?

I have the following circuit (assuming an ideal opamp), simulate this circuit – Schematic created using CircuitLab which has a transfer function that looks something like  \frac{As + 1}{Bs + ...
114 views

### Understanding Bode Plot of power supply loop

I am trying to decode the bode plot of a feedback loop of power supply measured on Bode 100 (network analyser) in 'intuitive manner'. 1. High gain (60 to 40 dB) at lower frequencies (0 -100 Hz) ...
91 views

### How to compensate inverter nonlinearities in feedback manner?

I have implemented the direct field oriented control of the three phase induction motor. The control algorithm exploits a speed sensor and machine model based on the Luenberger state observer. The ...
41 views

### Is there a correlation between conditionally stable systems and non-minimum phase systems?

I know bode plots cannot be used for non-minimum phase systems ( eg: delay, Boost converters). Can we identify the closed loop conditional stability from open-loop bode plot response? Conditional ...
25 views

### Is it correct to use the concept of phase margin for not so 'well-behaved systems'?

The TI document mentions the Phase margin as 60 degree for the given bode plot whereas the lowest PM when Gain >1 is around 45 degree. Wiki says: " Ordinarily, as frequency increases the ...
59 views

### Why do we prefer a cross over slope of -1 (20 dB/decade) for bode plot of power converters?

The video mentions (@12:45), we should ensure the slope at cross over should be around -1 (20 dB/decade). He mentions we can apply phase margin test if this condition is satisfied. As far as I know we ...
56 views

### Frequency response measurement of power converter - Why is the injection point across the resistor?

The standard procedure of measuring the frequency response of a buck converter is to inject a small voltage across a small resistor Rt as shown below. (Ref @4:40) Why do we apply the input voltage ...
27 views

### $H_2$/$H_\infty$ control

Typically, $H_2$ control design assumes stochastic noises and $H_\infty$ control design assumes squared-integrable noises. My question is about multi-objective control design, namely mixed \\$H_2/...
144 views

### How to integrate dead-zone in the PID controller implemented in the velocity form?

I have the below given implementation of the PID controller. ...
30 views

### What is the influence of the measurement offset in the PI control loop?

Let's say I have a control loop with a direct acting PI controller Now suppose that there is some positive offset present on the measurment of the controlled variable and at the same time the ...
160 views

### Power converter: Why is audio susceptibility named so?

In power converter, audio susceptibility refers to line-to-output transfer function. ( Line= Input voltage ) [ Ref : Fundamentals of Power electronics: Erickson ] Why is it named so- "audio-...
1 vote
107 views

### Power converter: Why we always focus on loop gain involving control to output transfer function?

While measuring loop gain using AP300 frequency analyzer, why we always focus on loop gain involving control to output transfer function? Is it because input to output transfer depends on power stage ...
355 views

### Frequency analyzer for loop gain measurement - Why should the injection point have low output impedance and high input impedance?

@5:08 The video mentions: "The insertion point should have a low output impedance and high input impedance" What is the background for this condition?