Відео

Thank u sir.

Professor Holden, I just viewed FFT in Excel for spectral analysis and really enjoyed it. I'm hoping you'll be able to help me with one problem. I use it on an Excel file with a 60 Hz wave with a significant 5th harmonic. The data was sampled at 100 kHz. One cycle of 60 Hz was displayed. I want to perform an FFT, but of course, there are 1,064 rows of data. The time domain plot shows a 1.2 A peak and a -1.2 A peak. The frequency domain plot shows a peak of 465 at 0 and 135 at 293 Hz. I have to be doing something incorrect. The sampling rate is more than needed for looking at 300 Hz. There should be no aliasing. Is there some guidance you can provide me?

Great video

Works great. Thanks

I love you ! your VOD just save my life !!! THX THX THX

5:30

Hi. Im interested in building and programming an autonamous sailboat of my own. I'm wondering what kind of board you have running and i'd be very interested to see what other sensors you have onboard

It Is only a Fourier transform example not FFt. Anyway Is a goog video.

Is the frequency for FFT's or function's?

Thanks!

You could get the habit to move aside the cursor of the mouse when typing in. Seeing things really help. Good video though.

Thank you sir ! This was extremely helpful for my Phd research.

I wanna ask something, if you dont mind, can you help me to analize a sin wave with a distortion, I just confused how to analize, what data I can produce from a sine waveform, this all regarding my thesis for master degree, maybe you can help me pls

Hi! Thanks for sharing this video. It is easy to understand. I wonder what if my data points are not in power 2. Now, I just add more 0 until the data points are power 2. But what about the frequency calculation. Should I use N only for my real data points (not include 0 data point)?

hello sir, sorry I'm new in FFT analysis, what is y axis unit? I knew that x axis is Hertz

Nice

Im kind of confused by a practical application that doesnt involve Hz. I have, for example, midday temperature data for every day throughout a 365 day year. My sampling frequency is 1/365, correct? My FFT must be done on a dataset that has a power of 2 samples, so I pick 256. Presumably I can model the entire year with this truncated dataset, though?! Of the coefficients that are generated, the 129th is the last before it repeats in reverse. What frequencies are represented? And how does the sampling theorem limit my results? And why am I getting a coefficient at the 0 Hz value that is orders of magnitude larger than the average of the dataset?

Does the sailboat take into account lifts or headers? I noticed that the wind angle is linear, but didn't see if the xtrack could be dynamically adjusted if, say you are in a major header heading away from the waypoint (weather mark) and the boat should tack at that point. And then as you get closer to the mark, the shifts are ignored as its more of a priority to get to the mark.

Thanks for sharing the great video, Prof. After watch it, that also made me thinking deeper to an another question. At 1:15 You made the g(t)= Cos(wt)=[2*pi*f*t], and the f=1Hz. That's the main reason that your FFT at frequency domain is peak at 1Hz 7:35, right? The reason that we do this analysis is to learn what frequency component we have in the waveform. If you use f=1Hz at the beginning of the analysis, that made the analysis simple. In a more complicated situation, say that the fundamental frequency is 10MHz but there is harmonics there, how should I perform the analysis using g(t)?

What's the dimensions! Seems like a winner!

Sir you can use 4G Hat for raspberry pi and insert sim card into it. Then you can use internet after that no range issue came. You can also use own private vps on raspberry pie because you have internet on raspberry pie. My suggestion i hope you like it😊

Fantastic! That was a lot of fun to watch. Thanks for posting the video and sharing how you setup the course.

Ok so much better then paying a subscription, hope it still works. If you connect a camera to the pi will it stream the video with same setup? Thanks in advance

Wonderful lecture, thank you so much!!!

couldn't stand it when your cursor is always in the way! blocking the view of what's being done, it's frustrating when struggling to see what's behind the cursor! good video but please pay attention to that in your next video.

Hello, thank you so much for the demonstration. I just can't understand why the FFT must be used with a sampling number at power 2. Can someone explain me this please ? :)

This is awesome. What are some great entry points to the topic if I wanted to build and program my own autonomous sailboat?

*Simulateur afficheurs cristaux liquide très pratique! Merci.*

What parts would I need to be able to do this?

Thank you.

Many have asked, why not only the frequency 1 Hz is present in the spectrum, and the answer were also given. Nevertheless just an addition for easier understanding: The time steps were selected to be 0.1s and the number of samples were 32. So, that means, you will have 3 complete cycles of the cosign function by the 30th sample, and than you have 2 more samples (or points) which actually mess up a little bit the nice complete function. So, when you repeat the data set - that is you continue the sequence with he first sample -, you actually have a "glitch" and the transition will not be smooth. This is why additional frequencies appear (the function whose spectrum was calculated here is actually not a pure cosign function in the time domain). If you want a smooth match between the start and the end of the period, the sampling frequency needs to be matched with the number of samples. In this case for example 8Hz instead of 10Hz (time step 0.125s instead of 0.1s), than it will really be a cosign function, and there will be only one value at 1Hz in the spectrum, all other frequencies will be zero.

Really helped me .... thanks a lot man.....if you have time....need your insights on sensor modification like adding proximity, custom imu and so on in ardusub firmware

Could you explain why the Amplitude of FFT ist not 1(because cos)?

which pixhawk version are you using ?

Awesome!

👍

what is the unit of FFT magnitude (mG) which is calculated in your video ?

When I try to use the fourier analysis on my percentage data it gives me the "The number of input values must be a power of two for example 2,4,8, 16... some of my data is odd number ie' 7%. 3 % ... Can this still be used on my percentage data or not?

great, thanks :)

This is great, thanks.

this was a wonderful video, very streamlined and to the point. Thank you :D

Very impressive indeed. I love to sail my DF95 and always wanted to identify speed so I could manually adjust tack with radio and get her to scream. Much simpiler then what you are doing. Any ideas how that may be accomplished?

How can I get a natural frequency from the FFT graph?

A huge Merci (:

Hi, putting something together for a friend using ardupilot, i have it working on the bench, do you have any tips? Unfortunately I don't have any rudder position feedback hoping not to need it.

should deltaf have been calculated with 1/(N-1)xdt rather than 1/nxdt? In your example, Nxdt = 3.2s but you only have data for 3.1s. I ask because I have seen a recommendation elsewhere to use f = k(total time).

I have a couple questions with a bit of context as necessary: I’m a software developer and I could make a relatively calm and deliberate instruction video on a setup I’ve just completed and know the outcome with near certainty, but if I was filming the first attempt it would be a very different outcome. There’d be rapid mood swings, curse words, name calling, moments of joy and happiness, in no particular order. How about yourself? I feel like I could be stating the obvious here, but I think you could have ratcheted up the coolness factor of this video and your project with a small but important addition. I think you might be more of the traditional (nothing wrong with that) back end developer that will architect an entire platform, write some scripts to get all the parts hooked up, build the data schemas and tables, basically the hard/skilled labor part, and then switch to optimization. Then some kid comes along, one that doesn’t know how to spell schema and shows up late with a Starbucks cup in hand every day, adds some massive front end javascript framework package on top of your app. Within a day the office is buzzing with excitement about the new app that you built, with a flash UI on the front end. But nobody seems to think you had anything.to do with it. That very well could be desired, but a little recognition every now and then keeps things interesting. That got a bit long winded, but what I am trying to say is if you added FPV video streaming to this setup then you’d have ladies lined up around the block waiting to take you to dinner! That may have been an exaggeration, but don’t let that distract from the point. How difficult would that be to add a live stream? Cheers. Thanks for the video

Cuter and apparently faster too.

How to get the phase of the signal in excel? I have tried FFT on an example sinusoidal in excel, FFT gives back correctly the frequency and the amplitude, but the phase doesn't seem right for me. I've just used =IMARGUMENT("FFT result at the desired frequency" ) but it didn't give back the correct value.

A huge thank you!! - that was what I needed to start the everything correct!