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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6
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2answers
196 views

Is it a problem to have two heat sources controlled for different temperatures on the same heating circuit?

This is the situation - I have three heat sources, called CHP, burner 1 and burner 2 on the same circuit. All three feed to the same heating manifold, with various heat demands. Preferably I want to ...
3
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1answer
181 views

Terminology for setting Set Points to avoid "Contact Bounce"-like characteristics

What is the terminology for having different/spaced-out on and off set points for a particular controlled process? When a system does not have the set points set appropriately, it could exhibit ...
2
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1answer
2k views

How to improve a PID control loop by adding feedforward?

Assume you have a system model that is controlled by a PID controller (feedback). You want to add feedforward to improve the characteristics of the controlled system. How can you design the transfer ...
7
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3answers
3k views

What do the zeros of the transfer function tell you about a system?

I come from a mathematics background and I'm familiar with laplace transforms in-as-far-as they provide an algebraic method to solve ordinary differential equations. So, when I read about transfer ...
3
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0answers
516 views

Finding the zeros for a PID controller

I would like to know what I am doing wrong for this PID controller design problem. I have all the parameters calculated ($\zeta$,$\omega_n$,$\sigma$...) and I have my target point set up. But now I ...
3
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2answers
72 views

connectedness between the output voltage and input voltage

Given this circuit I want to deduce the relationship between the output voltage $U_A(t)$ an d the input voltage $U_E(t)$ using Kirchhoff's current law. We're allowed to assume that $R$, $L $and $C_1$ ...
1
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0answers
219 views

Details of the phase margin

In my controls class, we're covering phase and gain margins. We're asked to increase the phase margin of a given plant to greater than 45 degrees using a lag compensator. Initially, the phase margin ...
4
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1answer
260 views

Negative feedback Gain and Phase Margin

Consider the system with unitary negative feedback such that the open loop transfer function is $$G(s) = \frac{as + 1}{s^2}$$ a) Determine the value of $a$ such that the phase margin is 45º b) ...
2
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1answer
4k views

Determining Gain from a root locus plot

I was looking over practice problems for an upcoming exam and I am struggling with root locus. I understand how to plot the basic root locus but for some of the aspects when gain is asked to be ...
6
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2answers
6k views

Calculating a transfer function from a block diagram

I've been having trouble doing this school assignment. My professor has not taught the class how to read control block diagrams so I assumed that we were supposed to research on it. I've watched a few ...
5
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1answer
128 views

How does the DERIVATIVE term slow down the signal?

I look at PID controler and do not understand derivatve term. I know it's used in order to not let the signal to overshoot the set value. BUT when the sigal is arising, its derivative is positive. So ...
6
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2answers
3k views

Feedback control of two-link planar manipulator

TL;DR: how can I calculate the disturbance at each joint due to coupling forces in a two-link planar robot manipulator actuated by two independent DC motors? I'm studying control theory and trying to ...
5
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2answers
712 views

Why do the poles and zeroes of a transfer function cause a slope change in frequency response?

Why is it that as the frequency approaches a pole or zero of a system, the slope of the magnitude of the transfer function changes by 20dB/decade? Whenever I see this stated when reading about ...
1
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1answer
345 views

Is it possible to engineer water-walking boots?

A naive question, yes, I know, but it's something that has plagued me for a long time. Whether by secreting a substance, controlled vibrations, metamaterials, or powered systems, is it possible to ...
4
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2answers
102 views

Analog PID controller - settings wrt $V_{err}$ - setpoint always higher than room temp

I designed from scratch an analog PID controller to mantain a temperature selected in the range of 60 to 80ºC with a room temp say = 20ºC. The "plant" is a simple 4R7 5 W resistor heated by a PWM-...
5
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1answer
1k views

Determine the range of values for a PI controller

This is a basic control theory question, since Control Theory is a part of applied mathematics but also of engineering I was unsure whether to ask this here. The question says: Given the transfer ...
3
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0answers
131 views

Is there a way to obtain a circuit of some sort given a Nyquist plot?

I have some transfer functions and I was wondering if it would be possible to approximate this to an electric circuit equivalent. For example, given the Nyquist plot below, is it acceptable to ...
10
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2answers
624 views

Differential equations of a (simplified) loading bridge

I am having trouble to calculate the differential equations of a simplified loading bridge. The system is build as shown in the picture below (just a sketch): If I use the Newton approach, I am ...
1
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0answers
113 views

How can a piece of steel rotated without any power input? [closed]

Currently I am trying to rotate a piece of steel >90 degrees without any power input. The piece of steel is attached on the wall. A servo is also attached on the steel. This question addresses ...
4
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1answer
4k views

Matched and unmatched uncertainties

In control theory, according to the definition of matched uncertainty, the uncertainty enters the system through the same channel as the control. If we consider the system: $$\dot x = F(x)+G(x)u+Δ(x,...
2
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1answer
280 views

Block Diagram Reduction: Is it necessary to do it stepwise?

Just a short question: Is there any usefulness in doing block diagram reduction piecewise? The reason I am asking is that I find it much (!) easier to just find the final $\frac{output}{input}$ ...
2
votes
1answer
176 views

Can a load be estimated using a Kalman filter?

I have a system with a motor, some masses, damping and springs. One of the masses is loaded with an unknown external force F. I want to estimate the force F using data of the motor (mainly current). ...
3
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2answers
371 views

Gain and phase margins of a system

I have the following system (see picture). When calculating gain and phase margins, should I consider $L=GK$ to be the open loop transfer function? If so, what difference does the transfer function $H$...
9
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1answer
2k views

How can I approach the application of control theory to real control systems?

I am an engineering student and I took my second dedicated controls class last semester. It was cool math and whatnot, but after all was said and done: I still have no idea how to make an actual ...
9
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1answer
330 views

Automatic Shifting without Electronic throttle

I need to design an automatic shifting system, for a FSAE car. Clutch and shifts are electronically engaged and disengaged using a Pi Innovo engine control unit (ECU). The issue I am worried about ...
9
votes
1answer
1k views

How do you set up a PID-Control if the time constants of the controlled system are variable?

The common description for a continous PID-controller is written like this: $$y(t)=K_p⋅e(t)+K_i\int_0^t e(τ)dτ+K_d\dfrac{de(t)}{dt}$$ The best value of the constants $K_p$, $K_i$ and $K_d$ for a given ...
5
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3answers
133 views

Help with closed loop heat controller (for a non engineer)

I am interested in setting up a controller which can modulate the output of 2 hotpads based on input from an infrared thermometer. The hotpads have their own dials, but I am considering controlling ...
4
votes
2answers
5k views

How do I calculate the density of seawater at different temperatures?

I need to know the difference in seawater density at 28 and 98 degrees Fahrenheit for control system synthesis. How can I calculate the density for a given temperature?
1
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2answers
225 views

How to calculate of Second-order system Frequency and Time domain values?

$\frac{0.25}{s^2+0.5s}$ Can I use formulas for 2nd order systems in this pdf? If not, how can I understand if this sytem is underdamped, damped, etc?
4
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2answers
159 views

What is the best method to model the input of an electro-mechanical system for control design and simulations?

In particular, say I have a dynamic model of the inverted pendulum / cart as described here. Instead of using the error difference in force to input into my controller, I want to take into ...
8
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2answers
2k views

How does one become a control systems engineer?

From what I understand, a control systems engineering job is almost always a senior level position. What kind of entry level jobs do most engineers have before they are qualified to actually design ...
3
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2answers
10k views

How to compute the transfer function from a response graph

I understand that the model for a first order system is $$G(s)=\frac{k_m*e^{-\tau s}}{T_ms+1}$$ In this case $\tau=3$ and the system gain $k_m=10$, correct? I need to calculate the transfer ...
6
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2answers
251 views

System identification on a system with constraints

I am trying to estimate a transfer function for a pan - tilt unit which is not as easy as I hoped. Its input parameter is a velocity, but it is constrained to move from 0° - 359° and the other way ...
14
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3answers
5k views

Can I use a ultrasound sensor to measure water level?

If I use an ultrasonic sensor will it detect the water level? I was thinking about a product to read water level on water boxes (common in Brazil). I researched about instrumentation for this ...
7
votes
1answer
2k views

Causal and Non-Causal PD Controller

Why is a Non-causal PD Controller: $C(s) = K_ds + K_p$ When a causal PD Controller is: $C(s) = (K_ds + K_p)/(\tau s + 1)$ The difference being the denominator. $\tau$ is the time constant and is "...
11
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1answer
1k views

Observability using the Discrete Extended Kalman Filter (EKF)

I have built (several) discrete Extended Kalman Filters (EKF). The system model I am building has 9 states, and 10 observations. I see that most of the states converge except one. All except 1-2 of ...
12
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2answers
288 views

How do I solve an optimal control problem where the dynamics depend on some function of the state?

A typical optimal control problem with state $x(t)$ and control $y(t)$ can be expressed as $$\max_{x(t), y(t)} \int_0^{t_1} f(t,x(t), y(t)) dt$$ subject to $x'(t)= g(t, x(t), y(t))$ and boundary ...
6
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1answer
694 views

Second order system with additional pole

Why is it that a second order system with an additional pole or zero can be approximated into the general second order system for analysis? This was asked during our lecture and I am still looking ...
11
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1answer
273 views

What is the significance of a diagonal input in a control diagram?

I have seen several block diagrams with diagonal inputs, drawn with an arrow through the block. and others like that (via Google image search) What is difference between this and a typical signal ...
9
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1answer
2k views

What is the difference between direct and indirect learning control?

I found the following comments on direct and indirect control in "Survey on iterative learning control, repetitive control and run-to-run control." by Wang, Gao, and Doyle: There are two ...
9
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2answers
734 views

Types of state observers/estimators actively used in the industry?

Most introductory books on control theory usually start their state observation part by introducing the Luenberger observer, and after that they might continue by introducing the Kalman filter. When ...
16
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2answers
376 views

Modern method for teaching controls

Background When I took my first class in controls (2006-ish as taught by an aerospace professor for a mix of ME and EE students) it was basically all done in Laplace-transform, transfer functions etc. ...
8
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1answer
274 views

Controlling hydraulic cylinders with variable delay

Electro-mechanical systems typically used in robots have very low delays and are quite simple to build servo controllers for. Hydraulic systems are much less common in robotics and have delay due to ...
10
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1answer
194 views

In the context of a known disturbance $d(t)$ in a control loop, what is the $\Delta t$ at which the control loop has to be executed?

As an example, consider a P-T1-system with a PID-controller. First look only at the P-T1 system, set a $y_r$ and wait a long time - then we take a look on its output $x$ and see that it has still a ...
4
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1answer
314 views

Given drive rotation angle, controlling torque, how do I maintain movement speed with varied load?

I'm working on design of a 3D movement drive (for 3D printers/CNC mills etc) using DC motors and helical drive. A DC motor drives the leadscrew actuator which supports the working elements (head, ...
5
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1answer
517 views

Baffle vs Bottom Temperature Measurement/Control

In an industrial jacketed reactor, we have two temperature probes: one on a baffle the extends down about to the 50% fill line one built into reactor, very close to the bottom valve. When is it ...
9
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5answers
236 views

Knowing how many times the rear wheels have rotated, and the angle of the front wheels at every time interval, how do I find the location of a car?

I'm making a robot for the Sparkfun AVC. I was curious if I could use only the knowledge about How the car is being steered at every time interval, How many times the wheels have rotated, to get a ...

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