# Questions tagged [frequency-response]

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### Relationship between antenna length and wavelength in radar

This is a question about radar design and how it works, because I'm trying to figure out some elements that are unclear to me. My understanding so far is that to detect an objet with a given size, the ...
• 161
22 views

### What does the resonance frequency mean in inertia matching

Like Kollmorgen shows in this PDF how you can calculate the resonance frequency of a motor coupled to a load. But with what can I Compare this frequency? It is clear that a higher resonance frequency ...
• 1
65 views

### Changing the relative equilibrium position for a 2-mass spring-mass system

I am trying to solve a double spring-mass system that is positioned vertically (I currently have the pendulum at an angle of 0 in my code below). I derived the system of ODE's required, and I get this ...
117 views

### How does frequency-response and lead-lag compensators fit in with PID or State Space control

I am new to control theory, as my background is in statistics. In watching a wonderful set of lectures by John Rossiter, and am feeling pretty comfortable with my understanding of the basic concepts ...
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### Topology optimization issue (or not an issue, which is the issue)

I am currently doing some work in topology optimization regarding optimizing for the dynamic compliance of a beam structure but I am running into some issues. Well actually I am not running into some ...
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1 vote
2k views

### What is the bandwidth for a 2nd order system?

I know that for a first-order system, the bandwidth can be computed known the time constant, tau, where the bandwidth is equal to 1/τ. Is there an equivalent formulation for a second-order system, ...
52 views

### How to push apart the first two natural frequencies of a cantilever beam

We have first two natural frequencies of a composite Cantilever Beam obtained through experiment and analytical calculation. Experiment gives 31 and 250 Hz whereas formulae give 30 and 200 Hz. ANSYS ...
1 vote
217 views

### Do sound waves caused by a vibrating machines correlate to the vibration waves of the machine itself?

I'm a computer engineer, so please excuse my lack of mechanical knowledge :). We have a machine that has large electrical motors causing massive amounts of vibrations, the machine also consists of ...
128 views

### Fundamental Frequency values for Rexnord ZA-2115 bearing

I am having difficulty coming to terms with the Rexnord ZA-2115 bearing technical specifications. This bearing is used in the NASA Bearing Dataset where the Rexnord bearings are tested at 2000 RPM ...
27 views

### Failure of component due to natural frequency vs stress

lets take a component like a fan blade as an example. Is it right to conclude that it will fail even when the stress is within permissible limits but its operating frequency is close (close enough ...
1 vote
72 views

### why Type III systems has at least two gain margins?

I heard the following statement https://engineering.stackexchange.com/a/54322/40848 if we have a type III system, or one that has three or more low-frequency poles that we're closing around, then we ...
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100 views

### Why are the phase indicators different between the open loop bode plot and the closed loop bode plot?

I have an open-loop transfer function G num=105*conv([1 1],[1 2 43.25]); den=conv([2 0 0],conv([1 2 82],[1 2 101])); G=tf(num,den); and a closed-loop function of G/(1+G). Here are the open-loop bode ...
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90 views

### How simultaneous can we trigger multiple cameras' frame acquisition

Say we have ten cameras surrounding an object. The object changes its color with a certain frequency (or any information other than color, such as a text on it). The point is if all cameras are ...
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### Contradiction of bandwidth and damping

I am studying control theory and mechanical vibrations. From control theory aspect, I know that bandwidth and response time is inversely proportional, which means bandwidth and damping as well. But in ...
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111 views

### Forced vibration single degree of freedom system

so for the Single Degree of freedom system, I obtained the equation in blue, where I think the equation below in black is missing the ‘m*a’ from F=ma? So I see that there is one ‘m*a’, but is that ...
437 views

### Modeling a second order system in time and frequency domain

For school I was asked to model the transfer function $H(s)=\frac{3}{(s+4)(s+5)}$ in both the time and frequency domains using initial conditions $y(0)=2,y'(0)=3$, a step input, and Simulink. I would ...
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1 vote
70 views

### Area under Frequency response function (amplitude vs frequency)

Recently, I was plotting frequency responses of multi-degree spring-mass systems and I was wondering what does the area under the FRF (amplitude vs frequency) (or in general FFT) mean? Does it have ...
115 views

### How can I find the right resonant frequency of a chassis?

Structures have infinite DOFs, so it possess infinite mode shapes. How can we find the right resonant frequency out of the infinite resonant frequencies so that we can save our structure? For example, ...
1 vote
568 views

### How to find out the sampling rate of an acceleration sensor?

In the sensor catalogs, I cannot find this field. They only depict the frequency response range. For example, Bently Nevada's sensors. How we can find out their maximum sampling rate?
236 views

### How to determine the dynamic response of a spring-mass system?

The Problem I have the following system for which I would like to determine its dynamic response, taken from these lecture notes pg.20: where the forcing functions are $u_1 = 1-U(t - t_0)$, $u_2=0$, ...
68 views

### Controls System experiment

We performed an experiment in which we turned a bicycle on its side and placed a piece of green tap on one of the spokes. We spun the wheel and recorded the wheel spinning until it came to a complete ...
154 views

### How do I study the frequency response of a physical system with Arduino?

I am a control engineering student and I am studying the frequency response of a system, so the Laplace domain, the Bode plot, poles, zeros,etc. ... I have clear grasp of their meaning, but if I think ...
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1 vote
21 views

### Transforming a Wireless Computer Mouse into a Wireless Switch [closed]

With no computer involved whatsoever, I want to be able to read oscillator outputs from my wireless mouse and switch an LED on a left click AND off on a right click. I have taken my mouse apart to try ...
589 views

### Boundary Conditions of a Stepped Beam

I would like to ask about the boundary conditions to be considered in a stepped beam. For a cantilever beam wherein the one end is fixed while the other end is free to oscillate along the z-axis, we ...
1 vote
33 views

### Finding force distribution using accelerometer data

The team I'm currently working for is trying to compare bushings with different durometer ratings in the front suspension using single axis(z) accelerometer data during curb impacts. The current ...
1 vote
52 views

### Where do I start with learning how to transfer data via RF

So I literally have no idea where to start but I know what I want to make. The goal is to somehow transmit 25mb/s of data across 15km with high penetration. Acceptable for reaching through trees and ...
27 views

### What do the rectangular components of the complex frequency (s) in Laplace transform stand for?

I tried doing a quick search on this question and was very surprised that this information feels very obscure as if it is almost never discussed. Complex frequencies appear in many mathematical ...
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### Deflection Equation of a Stepped Beam

Help out a college student. How do you derive the deflection equation y(x) of the shown stepped cantilever beam in the figure? Each segment has a unique Young's modulus and moment of inertia. The ...
1 vote
350 views

### Z - transform of white noise

I am taking a graduate course in Digital signal processing with no prior knowledge in DSP. So I am struggling because I don't have the foundational knowledge. Please I need help with the following. ...
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### How to calculate frequency response of the system? and find missing values [duplicate]

I can convert the H(s) into the frequency response which is: 𝐻(𝑗𝜔) = 𝜇(𝑗𝜔/(1+ 𝑗𝜔𝜏)) and the output in the steady state is: 𝑦(𝑡) = |𝐻(𝑗2)|sin(2𝑡 + ⟨𝐻(𝑗2)) The phase: ⟨𝐻(𝑗2), has to ...
601 views

### Phase shift of transfer function using MATLAB

I'm trying to compute the phase shift of a transfer function (accelerance) in MATLAB, but I'm having issues. The transfer function was computed by dividing the magnitude of the system output by the ...
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### Getting the damping ratio from a frequency response function v.s. transfer function

I'm trying to find the damping values of a specimen, based on sweeping the forcing frequency from 0-10 kHz. As shown in the diagram, I measure the input force from the shaker, and the subsequent ...
• 129
526 views

### Could Tesla have REALLY shaken a building with a little oscillator?

I came across this story while reading about Nikola Tesla ground-power scheme. Supposedly, he created a little oscillator that could be plugged into the ground, tuned to the right (resonant) frequency,...
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106 views

### What is the frequncy range of seismic vibrations?

I'm working on a structure which needs to sustain common seismic vibrations due to earthquakes. So I want to do some modal analysis to find natural frequencies of the structure and make sure they are ...
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1 vote
775 views

### Physical interpretation of a Bode plot

I have a few questions regarding the physical interpretation of the information presented on a Bode plot. I believe it is one of those cases where I "don't know what I don't know", so please bear with ...
1 vote
6k views

### Why phase margin and gain margin should be positive?

In many textbooks it's given that gain margin (in db) and phase margin of the system needs to be positive for the system to be stable. I could not find the reason behind this. Could someone explain ...
1k views

### Relation between natural frequency and the thickness

If I have a solid material, let's say two bricks, one of which is thicker and I do modal/vibration testing. What would be the relation between thickness and natural frequency of any of them, is there ...
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### Construct "Modal Coordinates Time History" from transfer function and test accel-time data

I have a query regarding the calculation of the so called “Modal Participation Factor time signal” from a combination of a) transfer functions (amplitude and phase for each eigenmode) obtained from "...
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1 vote
32 views

### Mobile Frequency and Carrier Frequency not Matching

I am using a Google Nexus 6 Mobile in India with Airtel as Network Provider. Recently Airtel has upgraded their Network to 2300 Mhz 4G. Whereas Google Nexus 6 Operates on Band 3 (1800Mhz) LTE. When ...
175 views

### How do I verify the reaction forces of an FE model due to a response spectrum

In the case of a static calculation of a structural model, one can verify the model by checking the applied and reacting forces to be equal zero. I would like to adapt the same principle for a ...
• 207
434 views

### Nastran / Frequency Response / Free-Free

There are examples of using SOL 108 and SOL 111 to create a frequency response. In Siemens Simcenter (NX Nastran), the examples focus on a tower with a seismic mass. The model drives the mass with ...
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### Do internal / external stresses affect modal frequency?

Imagine a cantilevered beam, fixed on one end and with a tension line connecting the other end to ground (e.g. perpendicular to the length of the beam). If I increase the tension, does the modal ...
• 163
4k views

### What can be the reason of the constant 50 Hz sound in my home?

I am suffering from a strange hum in my home. I have just bought my home and living in 3 months. A month ago I've started to hear a humming noise. Then, I recorded the sound and looked at its ...
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### Frequency domain analysis of steering system of a car

Can anyone share the equations involved, or some relevant theory material for frquency domain analysis of steering rack and pinion using bode plot?
1 vote
39 views

### What's the best way to get an ultrasonic sensor that can vary its operating frequency

Long story short I'm looking to build an ultrasonic sensor that can also be used to communicate with a seperate sensor. (So it must be able to send out a pitch around ~42kHz, but also alter the pitch ...
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### Base Driven Tuning Fork Mechanical Response Spectrum

I am new to vibration analysis/simulation etc. so I may be missing something very basic here so please forgive me if I'm explaining things poorly or not making sense. To familiarize myself with ...
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### Fourier series with frequency response

I have seen many times that people gets the frequency response function using DTFT. Can I use the Fourier series, and when I do that?
1 vote
78 views

### MIMO control: static inverse plant decoupling

I am using techniques explained in the book of Skogestag, Multivariable feedback control, for feedback control of a MIMO plant. In this book they explain the phenomena of static inverse plant ...