Questions tagged [control-systems]

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19
votes
3answers
5k views

A good textbook for designing signal filters

Since a couple of months ago I started being actively involved in the area of control of dynamical systems. In most cases, designing a controller for a given dynamic system will require the ...
16
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1answer
1k views

How to deal with a negative pole (unstable) in the pre-filter of a control system?

So while answering how to design a PI controller for a first order time delayed system (Question Here ) Here is the closed loop equation to a control system: $$ G_C(s) = \frac{\frac{K}{T}(1-sT)(s)...
13
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6answers
4k views

Relation between signal processing and control systems engineering?

Control systems engineering and Digital signal processing are both important courses/subjects of electrical engineering But how these two subjects/courses are related to each other?? Also please ...
11
votes
2answers
5k views

How to do prediction using frequency domain data?

Both linear regression and Kalman filtering can be used to estimate and then predict from a time domain sequence of data (given some assumptions about the model behind the data). What methods, if ...
11
votes
1answer
3k views

What is the "waterbed effect" in control system design?

I recently stumbled across some notes on the "Waterbed effect" in some notes by A. Megretski for an MIT course on "multivariate control systems". Here's an excerpt: A common effect, usually ...
10
votes
0answers
183 views

Estimating the input to a system from a system state using EKF [closed]

[ Cross-posted from: https://math.stackexchange.com/questions/164169/estimating-the-input-to-a-system-from-a-system-state ] I have a system for which I have obtained a non-linear time-varying state-...
8
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4answers
11k views

Do we use closed loop or open loop information in Bode plot, Nyquist plot and Root Locus?

When analyzing a control system via Bode, Nyquist and Root-Locus, are we using open or closed loop information? I'm not able to understand when the poles of the open loop are used and when the one of ...
7
votes
1answer
101 views

Kalman Filter: How to Define Inputs and Outputs of a Model

I'm a software engineer with a CS degree working in machine learning. I'm trying to learn about Kalman Filters. In this short YouTube video from Mathworks, there's a discussion on a Kalman Filter with ...
7
votes
1answer
268 views

Fundamental questions about state-space and Kalman filters

I am a dsp guy, I only did a minimum of control theory back in university. While trying to grok state space analysis and (discrete time) regular Kalman filters, I am hitting a few questions that ...
7
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2answers
277 views

Regarding the choice of cost function in adaptive control - squared error vs absolute error

I did search the question database regarding this question, and although one or two questions came close, they didn't really address my specific question. In adaptive control based on minimizing ...
6
votes
3answers
837 views

Why is an RC circuit a first order system?

I am going through the following tutorial: Time-Response Identification of a Resistor–Capacitor (RC) Circuit Why do we call the RC circuit a first order system? I understand the order of a system ...
6
votes
1answer
13k views

Why eigen values and poles of a system are equivalent?

In control systems engineering, the stability of a system (modeled in the form of Transfer Function) is determined by the poles of the system in the right or left hand sides. When the model is ...
6
votes
4answers
371 views

Make a signal that fits another the best possible with a limitation in the 2nd derivative

Consider this step function: The signal that "fits" this should look like the following (in green): The corners are now smooth because the maximum second derivative allowed is not infinite anymore. ...
6
votes
1answer
2k views

AutoExposure with nonlinear camera: Non linear proportional PID?

Now I', wondering how to best implement a control algorithm for it. I tried using a PID controler but started with a simple P-control first. The problem is, that when using the equation ...
6
votes
1answer
249 views

Is there a strategy for discrete control of a system with dynamics near sample rate?

I'm trying to control a system where the controller sample rate is physically fixed and the plant has significant dynamics on the same order as the sample rate. I understand that one would prefer to ...
5
votes
3answers
338 views

Discrete State Space Model - Why Are We Calculating $ x \left[ k + 1 \right] $ Instead of $ \dot{\boldsymbol{x}} \left( t \right) $?

A continuous state space model is defined as follows. $$ \dot{\boldsymbol{x}}(t) = A \boldsymbol{x}(t)+ B \boldsymbol{u}(t) \\ \boldsymbol{y}(t)= C \boldsymbol{x}(t)+ D \boldsymbol{u}(t) $$ If we ...
5
votes
3answers
348 views

Frequency warping when integrators are replaced with backward-euler and forward-euler integration

Resonant controllers are used in the power industry. The transfer function is $G_{res}(s) = \frac{K_i s}{s^2 +2\omega_c s+ \omega_o^2}$ The "textbook" discrete implementation is depicted in ...
5
votes
2answers
1k views

Does the impulse response of a system have any physical meaning?

In other words, what does the impulse response tell us about the characteristics of the system? For simplicity, let's assume we deconvolve a discrete output and a discrete input to obtain an impulse ...
5
votes
2answers
4k views

Inverse system in Simulink

I have the following inverse system $$G(s)= s^2 + 2s + 3$$ How do I implement it in Simulink? Note that the transfer function is only accepted if and only if the order of the numerator is less than ...
5
votes
1answer
97 views

Unstable plant transfer function identification

I would like to find the transfer function of an unknown unstable SISO plant. If it was a stable plant, I would input a sine sweep and measure the frequency response at the output; but I cannot do ...
4
votes
2answers
357 views

Which step response matches the system transfer function

A system has the following open loop bode plot: - Which one of the plots below describe the closed loop step response for the entire system? My attempt My initial thought was to look at the static ...
4
votes
4answers
280 views

Layman Description of the Kalman Filter

I want to know about Kalman Filter but i tried searching different links including Electrical Engineering StackExchange but the information available there was hardly digestible. All I am able to ...
4
votes
2answers
165 views

How to set parameters of the PI controller inside the PLL?

I am going to implement in C++ software the synchronous frame phase locked loop (SFPLL) for estimation of angle and frequency of the three phase grid 220V/50Hz. For the internal PI controller setting ...
4
votes
1answer
282 views

How do I get a faster system response?

I have this model in simulink (the graph is my output): The step input has amplitude 0.5 m/s, and it steps up after 0.1 seconds. The gain $K_p=5$. The saturation block is to keep the voltage between -...
4
votes
2answers
117 views

Stabilizing the inverse transform of a system

Currently I am trying to understand an unknown mechatronic system. I used white noise as an input signal and measured the output of the system. Then I estimated a second order SISO transfer function (...
4
votes
2answers
3k views

What is the difference between a controller and a compensator?

I recently revisited some texts on control theory. In some textbooks the term compensator is used, seemingly interchangeably with controller (see e.g. The Control Handbook by Levine, chapter 14 on ...
4
votes
2answers
8k views

What is the difference between a lag compensation and PI control?

A lag filter or compensator has the Laplace transform transfer function $$G_c(s) = \frac{s+z}{s+p},$$ with $-z < -p < 0$. In practice, the effect of lag compensation in feedback control, is to ...
4
votes
2answers
2k views

How to establish transfer function of a speaker?

I'm working on a signal processing project about vocal system, and I'm trying to use controlling theories to solve the problem. I need to get the transfer function, $H(s)$, of a speaker, from ...
4
votes
1answer
913 views

Determining the final value of the output of a discrete system

I'm going through an exam question where I've been told that the samples $f(kT)$ of the following function \begin{equation}{F\left(z\right)=\frac{1}{1-0.819z^{-1}}} \end{equation} are applied to a ...
4
votes
1answer
3k views

Find transfer function from root locus and step response diagram?

I am given the response of a step of magnitude of 3 and the root locus and I have to find the transfer function of the system. The function I find gives me the step response(magnitude of 3 again) of ...
4
votes
1answer
52 views

How to evaluate a close-loop control during transient?

I have implement a close-loop control in order to perform the tracking of the desired signal R. The basic scenario shall be summarized as follow: I have to evaluate the performance of my control G ...
4
votes
1answer
2k views

Measuring the open loop transfer function in closed loop: what's the better approach?

Considering the closed loop system; $C$,$G$, and $H$ all linear and stable transfer functions, If I chose to excite $\bf r$ and measure $\bf e$, I get the Sensitivity Function, $S$ $$S=\frac{1}{1+CGH}...
4
votes
1answer
148 views

Developing Lead Compensator to Decrease Settle Time

This is a follow up to this question. I've approximated the transfer function for a system to be H = zpk([0.012 -1.05 18],[-0.22 -0.22 -45 -1000],10000);. My goal ...
4
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0answers
222 views

Digital control: Exercise solution

Can you help me (show me how) to solve the following exercise? For the process with transfer function $G(s)=e^{-2s}/(s+1)$ design a digital controller with sampling time $T_{s} = 1$ that meets the ...
3
votes
3answers
7k views

Why oscillations in PI control?

When integral control is added to proportional controller (i.e. PI control), why steady state error becomes 0 and why oscillations appear , how actually the integrator works ?
3
votes
2answers
518 views

State space physical meaning

Let $T(s)$ be a transfer function that describes a mechanical system, where the input is force and the output is position. And let $[A,B,C,D]$ be the equivalent state-space representation of $T(s)$, ...
3
votes
1answer
1k views

In the context of transfer functions, what is the relationship between the terms "proper", "causal", and "realizable"?

I am thinking about these terms in the context of linear control. A transfer function is proper if the degree of the numerator is not greater than the degree of the denominator. I've read often that ...
3
votes
1answer
729 views

How can a system be unstable if $L(j\omega)$ is never exactly $-1$?

Say we have a linear system with unity feedback, with loop transfer function $L(j\omega)$. The closed-loop transfer function from reference to output is $T(j\omega) = \frac{Y(j\omega)}{R(\omega)}=\...
3
votes
2answers
414 views

Why does the control effort increase if the bandwidth of the system is higher then the bandwidth of the plant?

I am studying control systems and I am focusing on the control effort. I have seen that if I place a pole at higher and higher frequencies, if the bandwidth of the system goes above the bandwidth of ...
3
votes
2answers
2k views

Is this system time invariant?

I've been working at this problem for a while now, and can't seem to come to a solid conclusion - is this system time invariant? $y(t) = \int_{-\infty}^{t} e^{-9(t-\tau)} x(\tau)d\tau $ My reasoning ...
3
votes
1answer
2k views

What is the Reference in Control Theory?

I've started studying Control and I've come across some concepts that I'm finding a bit difficult to understand. For example, in the system showed here, there is a signal called "reference" as well ...
3
votes
2answers
1k views

Control design: under what conditions can closed-loop poles be placed arbitrarily?

Say we have a single-input linear system $\dot{\mathbf{x}} = A\mathbf{x}+Bu$. With full-state feedback ($u=-G\mathbf{x}$), it is straightforward to arbitrarily place the $n$ closed-loop poles (i.e., ...
3
votes
1answer
109 views

Improving Velocity Estimation Using Multiple Sensors in a Dynamic System

I have a sensor reduction model which gives me a velocity estimate of a suspension system(velocity 1) . This suspension system estimate velocity is used to calculate another velocity(velocity 2) via ...
3
votes
1answer
107 views

What does it mean that a zero is slow?

I am studying control systems, and have encountered the definition of a slow zero. I am searching on internet and in books, but I don't understand the meaning this. I know that if a zero is too slow, ...
3
votes
1answer
311 views

SRF-PLL discretization problem

So I've been working on how to digitally implement a static reference frame PLL (SRF-PLL), which is a quite popular PLL used for extracting three-phase grid angle. This PLL works by using the DQ0 ...
3
votes
1answer
595 views

For a standard second order transfer function, what is the equivalent time domain significance of $\zeta>0.707$?

In frequency domain $\zeta>0.707$ implies no resonant peak in frequency response. But I am unable to correlate what is the exact time domain effect of this? If $\zeta=0.707$ acts like an '...
3
votes
1answer
112 views

Iterative Kalman filters and system parameters estimation

i am working recently on a project in which i want to implement a Kalman filter as being an observer, and i couple this observer with a state feedback controller that produces control actions ...
3
votes
1answer
102 views

Effects of delay in a discrete-time controller for a continuous-time plant

I'm trying to understand the effects of sample-to-update delay in digital control of power electronics. I am aware of the issue but not 100% sure how to quantify it. There is an interesting paper by ...
3
votes
1answer
53 views

Is it possible to use a control scheme with a delay as prefilter?

I am studying control systems, and in my studies I have encountered the topic of control scheme of the form and I have seen thaht this control scheme is really useful since it is possible to add a ...
3
votes
1answer
72 views

General tips for PID tuning of super low-friction actuator?

I realize this question is not directly related to signal processing, however, it's relevant to system analysis which is relevant to most signal processing engineers. There's also no good alternative ...

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