# 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.

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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 ...
14 views

### 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 ...
1 vote
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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 ...
33 views

### 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 ...
61 views

### 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 $E\{\hat{H}(f)\} \ne H(f)$ ...
36 views

### 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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### 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 ...
130 views

### 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 ...
5k views

### 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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### 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 ...
34 views

### 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:  \...