Eksperimentalni postav za mjerenje visine iskakanja objekta iz vode

undergraduate thesis

• Title (english): Experimental Setup for Measuring the Height of Objects Jumping out of the Water
• Author: Bojan Spahija
• Mentor: Nikola Mišković (mentor)
• Committee member: Nikola Mišković (predsjednik povjerenstva)
• Committee member: Antonio Vasilijević (član povjerenstva)
• Committee member: Filip Mandić (član povjerenstva)
• Granter: University of Zagreb; Faculty of Electrical Engineering and Computing; Zagreb
• Defense date and country: 2016-07-11, Croatia
• Scientific / art field, discipline and subdiscipline: TECHNICAL SCIENCES; Electrical Engineering

Abstract

Cilj završnog rada je poboljšati rezultate projekta u kojem se određivala visina
iskakanja stiropornih kuglica različitih veličina s različitih dubina iz bazena. Objekt
iskakanja mora izroniti iz vode okomito da bi detekcija maksimalne visine bila što
preciznija. U prvom eksperimentu su kuglice zbog turbulencija iskakale u stranu i na
kraju je bilo vrlo malo dobrih mjerenja. Kako bi se to poboljšalo, lijepi se stožac na
kuglicu koja se prethodno trebala precizno odrezati. Takav spoj daje model objekta za
otpuštanje sličnog obliku suze koji je aerodinamičan i trebao bi smanjiti turbulencije,
a time i skretanje. Vrh objekta (kuglica) se obojala crvenom bojom da bi se mogla
detektirati u Matlabu.
Otpuštanje se vrši s betonskog bloka iznad kojeg je postavljena GoPro Hero3 kamera.
Za svaki od 2 objekta radimo po 15 snimanja na svakoj od 3 dubine otpuštanja.
Za veći se objekt iz snimki detektiraju crveni pikseli i iz njihove ukupne površine
izračunava se polumjer u pikselima. Taj se polumjer za manji objekt dobiva aproksimacijom
kružnice oko detektiranih crvenih piksela. Računa se fokalna udaljenost
kamere te se računa preko nje i poznatih dimenzija objekta, za svaki polumjer u pikselima,
udaljenost objekta od kamere u centimetrima. Na kraju se sve dobivene krivulje
promjene visine od površine u vremenu iscrtavaju na zajednički graf.
Rezultati su mnogo bolji od prvog eksperimenta, ali na većim dubinama i dalje
dolazi do čestog iskakanja u stranu. To bi se moglo riješiti dodavanjem krilaca za
usmjeravanje putanje kroz vodu.

Abstract (english)

The goal of the thesis is to improve upon the results of an earlier project in which
students were trying to determine the jumping height of different sized styrofoam balls
from different depths bellow water. The balls must jump out of the water vertically for
the maximal height detection to work as precise as possible. In the first experiment,
turbulence caused the balls to jump out of the water sideways and there were few good
measurements. To fix the turbulence problem, a styrofoam cone was glued to the ball
which was beforehand precisely cut. The created object resembles the shape of a tear
drop which is very aerodynamic and should reduce the amount of created turbulence,
and with that, reduce the trajectory errors. The top of the object (the ball) is colored
red so it will be detectable in Matlab.
The object is being released from a submerged concrete block above whom a Go-
Pro Hero3 camera was placed. For each of the 2 objects, on each of the 3 release
depths, 15 recordings of the jump are filmed. For the larger object, red pixels are detected
and summed in order to get the red pixel area of each frame. Than we use the
pixel area to calculate the ball radius in pixels. For the smaller ball, we use a built-in
Matlab function for circle approximation on the frames with detected pixels. Once the
circle radius of each frame is calculated, the focal distance of the camera is calculated
and later used along the known object dimensions to calculate the distance between
the object and the camera in centimeters. Last thing that must be done in Matlab is
aligning and plotting all of the height curves on one figure.
The results are much better compared to the first experiment, however on deeper
release depths the jump trajectory tilts away from the vertical path and the object jumps
to the side. This could be fixed by adding wings which will help to keep the object on
the vertical trajectory.

• Keywords: uzgon; visina iskoka; voda; eksperiment; aerodinamika; turbulencije; obrada snimaka; terminalna brzina; otpor vode
• Keywords (english): buoyancy; jump height; water; experiment; aerodynamics; turbulence; video processing; terminal velocity; drag
• Language: croatian
• URN:NBN: urn:nbn:hr:168:875664
• Study programme: Title: Electrical Engineering and Information Technology; Study programme type: university; Study level: undergraduate; Academic / professional title: sveučilišni/a prvostupnik/ prvostupnica (baccalaureus/baccalaurea) inženjer/inženjerka elektrotehnike i informacijske tehnologije (sveučilišni/a prvostupnik/ prvostupnica (baccalaureus/baccalaurea) inženjer/inženjerka elektrotehnike i informacijske tehnologije)
• Type of resource: Text
• File origin: Born digital
• Access conditions: Closed access
• Created on: 2018-02-06 11:52:43