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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15
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2answers
369 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. ...
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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 ...
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 ...
11
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3answers
1k views

PID controller explanation

I haven't found a text that explains the PID controller in simple words. I know the theory: that it calculates the derivative and the proportional gain and the integral etc, but I need to know in ...
11
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1answer
269 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 ...
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 ...
10
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5answers
17k views

What do you call the difference between the on and off temperatures in a simple thermostat?

A simple thermostat will turn on at one temperature and off at a higher temperature. This keeps the thermostat from cycling on and off too quickly. The difference between these values is sometimes ...
10
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2answers
620 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 ...
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 ...
10
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1answer
2k views

MIMO (multi input - multi output) system decoupling method

A MIMO system with 2 input and 2 output decoupling method to a SISO system is described in many articles and books. How about m*n size transfer functions systems? How can we generalize the method for ...
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 ...
9
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2answers
7k views

Block diagram vs flow chart?

I was studying a book on control systems where I read that a block diagram is a specialized high-level type of flow chart. What is the difference between a normal flow chart and a block diagram?
9
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2answers
728 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 ...
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
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 ...
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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1answer
327 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 ...
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 ...
8
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1answer
312 views

Why is it impossible to create an observer for this not fully observable system?

Consider a 1D point-mass moving along an axis. A force $u$ is applied as control. There is no gravity or other forces involved. The system can be described in state space equations as: $$\begin{align}...
8
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1answer
273 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 ...
7
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5answers
2k views

Would a centrifugal flyweight governor system slow down the descent of an object that is free falling down to the Earth's surface? (Revised design) [closed]

I am wondering if rotating flyweights would slow down the descent of a object that is free falling down to the Earth's surface. Please reference the conceptual drawing below: This drawing is showing ...
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 ...
7
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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 "...
7
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2answers
118 views

Unexpected Results from my Transfer Function

I have a system that can be modeled with the following picture: There is a mass $m$ connected to a spring $k$ and a dashpot $d$. These are both connected to another dashpot $c$. A force $F(t)$ is ...
7
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1answer
383 views

Computing error dynamics from state space deadbeat observer

I'm trying to solve this problem: Given the transfer function: $$ G(z) = \frac{z^{2}+2z+1}{z^{3}-z^{2}-5z+1} $$ Design a deadbeat observer for this transfer function and compute the ...
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2answers
1k views

Writing a filtered derivative term of the PID controller into the C++ code

Everywhere I look, be it a PID, lead, lag control or anything else, there are Simulink schematics with transfer functions. This is all nice for system response simulation, however currently I have to ...
7
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2answers
165 views

How to optimise feed-forward control of a process based on a prediction using the prediction confidence?

I'm looking for a control method for a production process with the following characteristics: 1 control variable many process parameters (+-50) 1 resulting variable continuous measurement of ...
7
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2answers
371 views

On a Diesel/hydraulic DMU train what exactly does the “go faster” lever control?

Let's say that you are driving a Diesel Multiple Unit† with either mechanical* (i.e. an actual gearbox with multiple ratios) or hydraulic (i.e. two or more torque converters) transmission. When you ...
6
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3answers
507 views

P&ID Symbol identification, unknown meaning

I'm aware that answers may vary and it really does depend on the company/country where the PID was drawn but I have checked back for the last 30 years and found no drawing legend that describes what ...
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 ...
6
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2answers
139 views

A clarifying question on Lasalle invariance principle

Given a nonlinear system \begin{equation} \dot{x}=f(x),~x(0)=x_0 \tag{1} \end{equation} where $f\in{\mathcal{C}^{1}}:D\to\mathbb{R}^{n}$. The Lasalle invariance theorem statement goes as follows: Let $...
6
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1answer
686 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 ...
6
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1answer
215 views

How many states need to be measured for a reduced order observer?

I have a DC motor system with three states. The states are: $x_1$ = position (degrees), $x_2$ = velocity (degrees per second) $x_3$ = current (Amps). My plant input $u(t)$ is measured in volts. ...
6
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2answers
194 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 ...
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 ...
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 ...
6
votes
1answer
539 views

mass calculation from transfer function or bodeplot

I have a double mass rotary model. The two masses are connected by an axis which together acts as a spring damper system of the fourth order. The system is actuated by a motor and the angle of ...
6
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1answer
308 views

Questions regarding Cornering Stiffness for RC Car

I am a bachelor's level student tasked with modeling the vehicle dynamics of an RC Car that will be made to drive autonomously. I lack prior experience or particularly specific education with vehicle ...
6
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3answers
186 views

Need some advice, control system animation. Appreciate some help!

I would like to have a 3d simulation of a helicopter landing on a ship. I thought about using matlab for this, as a far as I know you can connect models from Simulink to virtual worlds using blocks, ...
5
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3answers
132 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 ...
5
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2answers
316 views

Minimal realization of a MISO system

Given the following system: $$\dot{x} = \begin{bmatrix}1 & 1 & 0 \\ 0 & 1 & 0 \\ 0 & 1 & 1 \end{bmatrix}x + \begin{bmatrix}0 & 1 \\ 1 & 0 \\ 0 & 1 \end{bmatrix} u$$...
5
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2answers
365 views

A stable transfer function which diverges?

This question might sound stupid as I'm more of a software guy and never really had to do control engineering (besides the 101 classes). So I have a second order system I could approximate, with the ...
5
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1answer
134 views

When are overshooting controllers preferred over asymptotic ones?

Disclaimer Designing the behavior of controllers is an important task for many applications. Every application needs its own requirements fulfilled. For example a CNC machine needs a controller with ...
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 ...
5
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2answers
149 views

Linearization of dynamic equations/transfer function in control theory

I've gone through a control theory course, and after looking back at what we covered and how the subject was taught to us, I still have quite a few questions (which I unfortunately did not ask in ...
5
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2answers
678 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 ...
5
votes
3answers
290 views

Could a water stream be used as a fiber optic sensor and detect when the stream is broken?

I have a small idea/project I am working on in which I want to use a water fiber optic sensor that can detect whether the water stream is broken and if so shut off the water. Having looked into fiber ...
5
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2answers
1k views

How do I invert a system in state space form?

Suppose I have a system described in state-space form. Can I invert the system (swapping the roles of the input $u$ and output $y$)? If we start with: \begin{align} \dot{x} &= A\,x + B\,u \\ y &...
5
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1answer
128 views

Square shaped position error

I got a position error measured by a linear encoder like in the picture below. Could anyone explain some possible reasons for this kind of shape to occur in control theory? My system looks like ...
5
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1answer
123 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 ...

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