# 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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### 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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### 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 ...
283 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 ...
257 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 ...
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### 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 ...
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### 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 ...
16k 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 ...
604 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 ...
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 ...
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### 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 ...
232 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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### 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 ...
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### 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 ...
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### 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 ...
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### 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 ...
699 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 ...
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### 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?
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### 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 ...
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### 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 ...
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 ...
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### 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 ...
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### 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 ...
265 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 ...
127 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 ...
117 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 ...
475 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 ...
103 views

### How to compare dynamic systems of different degree of abstraction?

I'm modelling a vehicle as a multibody system in Matlab/Simulink. My goals are: Have a realistic simulation model so I don't have to do prototype measurements all the time. Solve specific parameter ...