Questions tagged [control-engineering]
Questions about the models and theories of control engineering and the application of control theory to design systems with desired behaviors.
647
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Linearization about equilibrium point 0 in the presence of unknown input
Consider a SISO non-linear system $$\dot{x} = F(x,u)$$ in which $\vec{0}$ is an equilibrium point. In the process of determining that it is indeed an equilibrium point, the input did not matter at all....
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Phase shift in Fourier transform
Suppose we have a signal x(t). If we Fourier transform the signal to the frequency domain we get a complex function (has js in it).
Do the js mean a phase shift and what does phase shift in a Fourier ...
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Fourier analysis of delta function
I have this periodic function:
$f(t) =\delta(t)+ \sum_{n=1}^{\infty }\delta (t-n)+\delta (t+n)$
and I need to find its harmonics by finding the coefficients for the Fourier series.
But how is this ...
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Control Engineering: Formal vs. Trial-and-Error
At university, my control engineering courses are focused on a more theoretical approach, but the main message from our professors was clear: When designing a feedback controller (PID, H-infinity, MPC,...
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Which controller is more suitable in this scenario? P, I or PI controller?
Scenario:
A robot has a ultrasonic sensor which measures the distance to the nearest object in centimetres. The robot has two motors, a motor for the left wheels and a motor for the right wheels. The ...
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How to determine the components of a feedback control loop given following context?
Based on this feedback control loop
where $w$ is the desired setpoint, $x$ the process variable, $e$ the error value, $y$ the correcting value and $z$ the disturbance value.
Did I interpret the ...
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61
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Measure a frequency response function
I have a slide here which says following:
For the control loop
...apply $d$, measure $u$ and $y$, calculate
$\hat{H}(f) = \frac{S_{yu}(f)}{S_{uu}(f)}$
but then typically
$E\{\hat{H}(f)\} \ne H(f)$
...
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Do asperity junctions break every time a machine starts to rotate?
After reading CONTROL OF MACHINES WITH FRICTION by Brian Armstrong-Helouvry, some questions rised.
The main question I ask you is:
Suppose two metal surfaces in relative motion first in static ...
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deal with algebraic loop in distributed control algorithm
Recently I found a distributed control method for multi-agent system, which implements an algebraic loop like:
$$
u_{i}=(l_{ii}+b_{i})^{-1}\left [{\sum _{j\neq i}a_{ij}u_{j} -\mu e_{2i}+b_{i} u_{0} }\...
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How can I find characteristic equation of complex systems?
I am working on an Overhead crane, where I am supposed to design a controller that controls the position of the crane while minimizing the load's sway angle. I have derived the transfer functions for ...
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Contradiction of bandwidth and damping
I am studying control theory and mechanical vibrations.
From control theory aspect, I know that bandwidth and response time is inversely proportional, which means bandwidth and damping as well.
But in ...
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How does adding a long fixed pole on top of a drone with a certain mass change the dynamics of a quadcopter?
I have to model a quadcopter with a long rod on top of it so I can later design a control system for the system. I'm a bit lost as to how the dynamics of the system change by adding the rod, can ...
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What's a real life example of linearization of a system around a fixed point
I'm tasked on finding a example of a real non-linear control system. a real paper or publication on a website like the IEEE thats describes the model of the system so I can then linearizy it around a ...
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Bode plot phase margin concept details
I know a closed-loop system $\frac{G}{1+G}$ is unstable when the open-loop transfer function $G$ equals -1 or $0dB\angle-180^{\circ}$. The denominator becomes 0 so the gain is infinite. This is why ...
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Phase margin concept: why can there be instability when the gain never reaches 0dB?
If the open-loop transfer function is always below 0dB but the phase crosses or approaches 180 degrees, the closed-loop system can still be unstable. Why? Example: open-loop transfer function $\frac{0....
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SMC: Is there a way to control two sliding surfaces with just one control input?
This is a question related to Control Systems.
I've been searching papers all over the internet with very little success. I know that traditionally we want one control per sliding surface but If ...
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How can nuclear reactors control the exponential cascade of neutrons fast enough to prevent an explosion?
The Wiki article on nuclear reactor physics states that
the average neutron lifetime in a typical core is on the order of a millisecond, the exponential factor is as small as 0.01, in one second the ...
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Steady state error of negative feedback system - zeroes of feedback function
I am currently studying control systems from the KUO - GOLNARAGHI book. Regarding the steady state error the book makes the following distinction:
Feedback function H(s) has no zero at s = 0
Feedback ...
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26
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Can I drive a pulley with two shaded pole motors using one motor at a time with different size pulleys for speed control?
Using two same RPM shaded pole motors, one with a one inch diameter motor and one with a two inch diameter. Using a DTDP switch to swap power from one pulley to the other. For a two speed rotation ...
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Control strategy for upper/lower limit control
I am currently facing a problem, for which I cannot find a decent control strategy. The problem is that I want to limit an observable/measurable variable in its maximum and minimum.
As an example I ...
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How to control speed of DC Gearmotor with Varying Torque
I have a system where the torque is constantly changing, but I need the speed to remain at 9RPM. I have enough room for error where I can be between 8 and 10RPM. How can I achieve this? All I can find ...
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Modelling an S-shaped Second Order Process Response
I am trying to model an S-shaped second order process response as a transfer function in Simulink, as shown in figure 3 in the linked article. Ideally the response should be overdamped. I have tried ...
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Modeling a second order system in time and frequency domain
For school I was asked to model the transfer function $H(s)=\frac{3}{(s+4)(s+5)}$ in both the time and frequency domains using initial conditions $y(0)=2,y'(0)=3$, a step input, and Simulink. I would ...
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Unexpected uncontrollable double integrator system during reference tracking (augmented state-space)
I'm trying to design a controller that will achieve reference tracking of the second state for the following system.
$$
\begin{aligned}
\dot{x} &=\underbrace{\left[\begin{array}{ll}
0 & 1 \\
0 ...
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1
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Stability properties of controllers with independent control laws applied in underactuated systems
I am interested in designing a GNC controller for a 3DOF underactuated vehicle that follows a path in 2D space. The two available control inputs are the thrust force in the surge direction and a ...
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130
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How to model the state space matrix of a pendulum?
Here's an image of the problem:
I'm trying to put the following problem in matrix form (state space) but I don't know how would I put -(g/L)sin(x1) in the A matrix since the x1 value is inside the ...
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Dynamical system problem
I have this dynamical system:
A = [ -0.313 56.7 0
-0.0139 -0.426 0
0 56.7 0];
B = [0.232
0.0203
0 ];
C = [0 0 1];
D = 0;
I'm ...
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Motor that plugs directly into wall outlet
I am looking to drive a disk at relatively low speeds (9rpm) and somewhat high torque (not sure on exact numbers, 100+ in-lb.) I am looking for a motor that can plug directly into the wall and just ...
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Finding optimal PID gain values with no Transfer Function or Plant model
Background:
I have a Matlab simulation model with .m files. The functions simulate a speed control system of a vehicle. I can control the vehicle's speed by adjusting the vehicle’s acceleration and ...
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Control scheme for roll compensation
I'm working on an application that rotates a cylindrical mass in a manner to compensate for roll in a boat. The roll of the boat is rather slow so I was thinking it might be possibly to simply use a ...
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Why are train brakes so complicated?
The concept is simple enough: no pressure in the train line has the brakes locked, full pressure is loose, and partial pressure drags accordingly. So if pressure is lost for any reason, the train ...
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Definition of Bandwidth as angular frequency
I am searching for a Formal Definition of bandwidth given the transfer function of a system, or the bode plot.
Is it the frequency $\omega_b$ in which
$$20log|H(j\omega_b)| = -3\text{dB}$$
or
$$20log|...
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Double Summation of Matrices in Convex Optimization in CVX
I want to implement the following optimization problem from the following paper Randomized Gossip Algorithms, Page 10 Eq. 53\
1- In this problem, $W$, $P$, and $P_{ij}$ are $n\times{n}$ matrices. I ...
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Control Systems: 3rd order system project [duplicate]
I'm in need of help finding a third-order or higher system in which I can derive a transfer function. We have a class project in which we need to find a real-life example of the system that equates to ...
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How to model a cable for control?
I'm studying a system in space that uses centrifugal force to keep four tip masses extended. The system is defined as follows : a central hub that has rotation freedom in all directions, four tip ...
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Simulink Treating Discrete-Time State-Space as Continuous-Time?
I have a MATLAB script wherein I take a second-order ODE on $\mathbb{R}^3$ (vector field on the phase space), then, at a critical point, take the Jacobian matrix $A$, use a "fully-actuated" ...
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What is a "Unidirectional Input" (?) Closed Loop Control Algorithm Called and How Does it Work?
PID systems inherently require some amount of overshoot in order to stabilize around a target. This often requires adding or subtracting some resultant term in order to shrink the relative error. ...
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Relationship between the infinity norm of estimation error and the trace of estimation error covariance matrix in Kalman filter
I am working on designing an interconnected distributed control system. In this system, I need to use Kalman filter because the measurements are noisy.
I have two questions:
1 - What is the ...
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Best Techniques to design a cascaded precision position controller
I'm looking to design a cascaded controller to transform a BLDC into a servomotor. The system has a motor current controller in the inner loop, which is controlled by a torque controller, which is ...
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How do you generate an impulse signal in a mechatronic system?
Background:
I have a piezoelectric force transducer that I am using to measure the force produced by a combustion reaction in a tube. The issue is that there is a lot of ringing that occurs during the ...
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What are disadvantages if increasing the gain Kd for a PD(Proportional Plus Derivative ) controller
What are disadvantages if I increase the gain Kd for a PD(Proportional Plus Derivative) controller, someone told me larger gain for derivative error for will reduce the stability margin, while the ...
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Why do pneumatic valves need both a Safety Relay and an Air Dump to be safe?
If air dumps safely release pneumatic pressure from an industrial machine when an E-Stop is pressed, why is it also standard practice to cut electrical control power from the valves with a safety ...
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How could I compute the stability margin from a closed loop response?
Why the stability margin is typically computed by the open loop response or transfer function rather than the closed loop response or transfer function, how could I measure/compute the stability ...
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Transfer Function for Electro-Mechanical System
Can anyone please lead me in the right direction as to how to solve for the transfer function given this motor schematic
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Additive perturbation
consider the following transfer functions:
$$
G(s)=\frac{1}{\tau s+1}G_0 \quad \tau_{min}<\tau<\tau_{max}
$$
show that this system equal to model with additive perturbation as follow
$$
G(s)=...
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Limitations to consider when picking a cut-off frequency low-pass filter for PID control?
Considering a first-order low-pass filter transfer function:
$$ \frac{\omega_c}{s + \omega_c} $$
Where $\omega_c$ is the cut-off frequency. Are there any limitations on where to place this pole?
For ...
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Question about how to study for engineering university exams [closed]
What are some of the ways to predict exam questions from class lectures in university final exams? How should one understand the mindset of the professor & find out important maths/questions he ...
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Time Constant For Step Response First Order System
I ran several experiments where I attached my phone to a motor and collected the angular velocity at different step inputs( different voltage values). My question is, is it possible for the motors to ...
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Block-diagram combining two controlled subsystems
I have two subsystems which are shown in the picture below.
One of them is a system of stable and controlled differential equations of a mechanical system.
Second is a block that implements a function ...
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plotting time delay system eigenvalues
I want to plot eigenvalues of below time-delay system in MATLAB
$$\dot x(t)= x(t)-a x(t-T)$$
T is delay
what I did until now is first I find the constitutive equation of this system as follow:
$$
\...
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