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phyphox Forums › Discussion › Experiments and Ideas v
Velocity from accelleration

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Velocity from accelleration
henfri Offline
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#1
03-22-2020, 11:37 AM
Hello,

can phyphox determine the velocity from the accelleration? 
I assume, that a pure integration would not be accurate enough, but that a Kalman Filter would be needed..

Greetings,
Hendrik
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Sebastian Staacks Offline
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#2
03-23-2020, 05:12 PM
The naive version without filtering is problematic indeed (see example in our wiki at https://phyphox.org/wiki/index.php/Exper...celeration). Unfortunately, we have not yet implemented any filtering beyond the simple methods that can be done in our file format via FFT or simple math operations.
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henfri Offline
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#3
03-23-2020, 06:40 PM
Hello Sebastian,

thanks for your reply.
Do you think that this would be a possible future development?

Regards,
Hendrik
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Sebastian Staacks Offline
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#4
03-23-2020, 08:27 PM
No, unfortunately I don't think so. Our list of planned features is growing faster than we can implement them and I do not have high hopes that this would work reliably as a "general purpose" tool. Integrating the sensor should work quite good if you optimize it for a specific tasks (i.e. putting in assumptions like times at which the device is at rest) and tweak some parameters for your phone, but I do not think that it is realistic to actually use it in class. After all, sensor fusion to achieve absolute positioning is useful in so many other tasks (especially AR and VR), but still it is only well-achieved in combination with the camera and only for specific devices. Maybe, we will at some point implement tools like AR-kit which will easily enable absolute positioning via the camera, but I do not expect that we will see sensor fusion by us.

By the way, if you have some background in data analysis (as you are asking for a Kalman Filter) and some programming skills, you can try a few things yourself. Phyphox is open source and even if you have never developed an app, you could probably just modify the analysis code to add filter functions in the same way that other analysis modules are implemented.
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henfri Offline
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#5
03-23-2020, 09:14 PM (This post was last modified: 03-23-2020, 09:26 PM by henfri.)
Hello,

thanks for your reply. I understand the conflict of Ideas vs. Resources.
I do not have enough background to implement a Kalman Filter - not in Phyphox nor elsewhere. I understand the background, but I have never done it (but my drone does regularly; that's where I would 'steal' the code).

In case someone wants to try, here some reading material:
https://www.nxp.com/docs/en/application-note/AN3397.pdf
https://makersportal.com/blog/2017/9/25/...n-elevator


Greetings,
Hendrik
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