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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162 views

Nyquist stability criterion for positive feedback

it is known that the stability of a system with negative feedback may be analized through the Nyquist stability criterion, which is based on observing the number of turns around the point (-1;0) in ...
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1answer
48 views

Difference between Linear control theory and non linear control theory? especially topics/contents wise?

Although I know that a linear systems is the one that follows principle of superposition but I want to know what topics/contents do we study in each of both categories linear control and non linear ...
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1answer
61 views

Effect of zero coefficient in polynomial in Routh Hurwitz?

Consider this polynomial: \$s^4+2s^3+3s^2+4s+5\$ What happens if we have zero in place of any coefficient in our polynomial? Will that indicate that the system is unstable? Let say we have zero ...
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1answer
244 views

What does zero transfer function mean?

I am solving a problem where I have to find the transfer function of a system. The system is $$A = \begin{bmatrix}2&-1&2\\0&1&-2\\0&0&-1\end{bmatrix}, B = \begin{bmatrix}1\\1\\...
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2answers
61 views

How to use MATLAB to observe the effect of multiple damping factors?

I want to use MATLAB to observe the effect of changing zeta (damping factor) on system response? Here is a m-file code that plots three responses: underdamped, overdamped and critically damped. <...
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1answer
75 views

Final Value Theorem yielding the wrong result?

C1 has an impedance of 1/0.1s Ohm in S-domain. Its impedance together with R1's is 100/(10s+10) Ohm The transfer function is: $$\frac{V_2}{V_1}=\frac{5}{\frac{100}{10s+10}+5}=\frac{50s+50}{50s+150}$$ ...
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1answer
388 views

Can my PID controller have negative p value and positive i value for a PID logic

I am building my first PID controller. My process variable and my actuator value are inversly related, meaning if actuator value increases process variable decreases, and vice versa. So I have tried ...
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1answer
910 views

Can a phase margin become bigger than 180° and is this bad?

I have a wrong mental model about phase margin in control theory. I see that a phase of -180° is bad. If my input is a sine wave and I have negative feedback, which has a -180° phase shift, the ...
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2answers
156 views

Sluggish step response of control loop

I have a question regarding the PI controller. Lets say I have an actuator via which I control some plant. The control signal at the output of the PI controller is at its maximal realizable value. So ...
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1answer
65 views

How do I calculate this inverse Laplace Transform

I have this transfer function and input, and I have to manually calculate what the systems response will be. The transfer function is: and the input is: I multiplied the two functions and used ...
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1answer
58 views

Method for selecting unique resistor values in all combinations

I do controls, and sometimes I want to monitor more dry contacts than I have digital inputs for. I'm cheap, and don't want to pay for more points, so sometimes I'll put some resistors in parallel ...
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1answer
797 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 ...
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1answer
267 views

Tuning PID coefficients for stationary stability of brushless DC motors

I'm using a commercial off-the-shelf brushless DC motor controller. It combines a PID controller and an absolute encoder to regulate position. When my motor reaches its target state, it generates a ...
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1answer
184 views

Determine whether the system can be stabilized by the control law

I have a controls homework question I am having trouble figuring out where to start. The questions is Determine whether the system can be stabilized by the control law \$u = - {G_1}{x_1} - {G_2}{x_2} ...
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2answers
257 views

Convert PID parameters to Q15 format

I have calculated the transfer function of my system to apply a PID to it. With MATLAB and the PID Tuner tool I got the Kp, Ki ...
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1answer
84 views

Efficient low current buck controller topology

In SMPS there are two sources of loss: parasitics, and the controller. Usually, the load consumes more power than the controller, and the parasitic losses dominate. I have the opposite situation. I ...
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1answer
75 views

Heat exchanger identification

I have been developing a digital controller for water cooling system of power electronics converter. This system consists of plate heat exchanger, pipe with demineralized water flow (this fluid is ...
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1answer
60 views

Closed Loop 4 Sensor Control System

I have 4 on/off motors running individually (call them M1, M2, M3, M4) and 4 ping sensors (call them X1, X2, X3, X4) with a board placed in front of the motors and sensors. As the motors move forward ...
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3answers
889 views

Cascade Control System - Multi-Stage Temperature Control

I am new to the forum, hopefully you can help :) I am a software engineer trying to put together a control system. My controls background is not strong, I have really only tuned PID loops via trial ...
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1answer
2k views

State space modeling with disturbances using Matlab

I am doing a project which involves modeling a quadcopter in state space form using matlab. I first had to linearize the quadcopter equations of motion, and now have to implement them in a matlab ...
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2answers
430 views

Stability of an unstable system using nonlinear element. Is it possible or not?

Say there is an system with open-loop transfer function $$G(s)=\frac{1}{s-1}$$ The system is definitely unstable. If I put an any nonlinear system in cascade with \$G(s)\$ & from the output, a ...
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2answers
14k views

Since the z-transform of the zero order hold is 1, why bother including it in analysis or simulation?

The \$z\$-transform of the zero order hold is 1. So why should it even be considered in the discrete time analysis or simulation of discrete time control systems? $$Z\left(\frac{1-e^{-sT}}s\right)=\...
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1answer
3k views

PID gains from the transfer function of a plant

I am trying to calculate gains ( Kp, Ki, Kd ) of a PID controller. I have to improve the response of a plant. I already have the Transfer function of the plant. I was wondering if matlab has some ...
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1answer
676 views

Interfacing Matlab with a NI real time target (cRIO 9073)

I currently have a control system implemented in Matlab that controls a vehicle. The tracking is performed using an overhead camera, and commands are sent to the vehicle via xbee. I have now added a ...
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1answer
677 views

Derive transfer function from block diagram

I have this block diagram which I already reduced pretty much: Now I want to derive the transfer function from phi_o1 to q. ...
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1answer
103 views

Exclusive control over actuators

I feel kind of stupid asking this question, but after unsuccessfully searching for papers and then starting to draw my own solution with a lot of XORs to the following problem, I started wondering ...
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1answer
310 views

Controlling temperature of a water bath with induction plate

I am thinking of building a sous-vide cooker using some kind of prebuild heater, controled via an AVR and temperature sensor like the LM35. There are a lot of references around using rice cookers, ...
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2answers
397 views

Greenhouse Control Interface

I'm working on a control system for my school's tropical greenhouse based on the Arduino. It'll just do basic logging things, along with allowing someone to selectively water sections of the ...
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5answers
130 views

RL circuit as a feedback loop

As far as I know for a feedback loop , a sensor is required to reduce the effect of disturbances but 1.why a simple RL circuit has a feedback loop but it didn't contain any sensor , so isn't sensing ...
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0answers
61 views

Problem understanding transfer functions of second order filters

The transfer function of any second order filter can be found by analyzing the circuit using the Laplace transform. For example the transfer function of a second order low pass passive RLC filter ...
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0answers
162 views

Mixed sensitivity controller design

I am defining a controller using the mixed sensitivity approach, and I have the following specifications: a low frequency attenuation of 60 dB a maximum resonance peak of 2 and I have chosen to use ...
2
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1answer
164 views

Linearizing hall effect sensors outputs

I'm trying to find a robust solution to linearize four hall effect sensors outout to obtain a signal that I can use in a PID control scheme. The output data is collect via 4 ADC channels on an ...
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3answers
731 views

State Space model for three-loop circuit

How do I choose the least number of state variables for the following circuit? I started out by assuming currents $$i_{1}, i_{2}, i_{3}$$ in each of the loops and applied KVL, which fetched me three ...
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2answers
642 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}}...
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0answers
82 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: $$\...
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0answers
73 views

Designing PID to reject load disturbances of dead-time process

I am using the PID Tuner for the PID Controller Block in Simulink. I am particularly interested in the output disturbance BODE plot. I am trying to achieve an acceptable output disturbance with the ...
2
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1answer
360 views

Least Square Fit - Transfer Function

I have here this continuous transfer function: $$\frac{Y(s)}{U(s)} = \frac{s+3}{s^3 + 12 s^2 + 39 s + 28}$$ Passing this tf to discrete domaing like this: ...
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2answers
10k views

Phase Margin and Damping Ratio Approximation

I have read in many texts that the closed loop system damping factor can be approximated as: \$\Phi_m= 100 * \zeta\$ With \$\Phi_m\$ as the phase margin and \$\zeta\$ as the damping ratio. The ...
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4answers
344 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 ...
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3answers
1k views

Switching frequency and controller's crossover frequency in DC-DC converters

In the context of control loop stability of DC-DC Converters, A switch mode power supply is essentially a sampled-data system, therefore the theoretical maximum bandwidth is one half the switching ...
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2answers
242 views

What is the difference between these two op-amp circuits?

I don't understand why when we design a proportional amplifier, the feedback has to be negative. When I run the simulation in simulink I get the same result for both circuits.
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5answers
3k views

Stability in control theory and electronics

In control theory, if the impulse response of a system dies out then the system is stable. In electronics, Bode plot usually uses the see the gain and phase margins and determines the stability of a ...
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3answers
118 views

How does an active filter transfer function translate to a block diagram?

I am having troubles trying to translate when finding a transfer function of an active filter is it in a 'Close loop' or 'Open loop' state? When finding the transfer function of these active op-amps ...
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5answers
674 views

Condition for absolute stability

A necessary condition for absolute stability of a system is Gain cross over frequency < Phase cross over frequency Where Gain cross over frequency is the frequency at which Gain = 1 or 0 dB ...
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4answers
24k views

Exact definition of overshoot

I am a computational biologist and am working on some aspects of control theory in biological systems. Since control theory concepts are not well known among biologists, I need a good standard ...
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2answers
2k views

How to implement a closed loop control circuit for slow process?

Given a slow process Vout = Process(Vcontr) which takes a control voltage Vcontr and produces an output voltage Vout but with some lag of the order of one second. ...
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2answers
152 views

Why am I getting non-sinusoidal output for sinusoidal input in a mass-spring system?

A mass-spring system is represented by the following transfer function $$ H(s) = \frac{s^{2} + 0.1s + 10}{s^{4} + 0.2s^{3} + 20s^{2}} $$ For a sinusoidal input I am getting a non-sinusoidal output, ...
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2answers
935 views

What is the relationship between a step input and an integrator?

While trying to understand control engineering from first principles I came across the following which I cannot yet explain intuitively or mathematically. What is the relationship, between a step ...
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2answers
579 views

Closed loop transfer function problem

Let's say we have the basic feedback system of the picture We know that the closed loop transfer function is given by $$T(s)=\frac{G(s)}{1+G(s)H(s)}$$ Now, the diagram above is equivalent to an open ...
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4answers
19k views

How to find 3 dB bandwidth of any transfer function?

Suppose we have a transfer function $$ G(s) =\frac{2(s+3)}{(s+6)(s+1)} $$ I want to know how to find out the \$3\textrm{ dB}\$ bandwidth of this transfer function?

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