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Changes for page Ball Physics

Last modified by Soeren Domroes on 2025/01/30 12:18
From version 13.1
edited by stu122612
on 2023/07/06 14:48
Change comment: Renamed from xwiki:PP18.Ball Physics
To version 12.1
edited by stu104225
on 2020/03/09 11:13
Change comment: There is no comment for this version

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1 -Project Documentation
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1 +XWiki.stu104225
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10 10  ----
11 11  
12 12  The trajectory of a ball can be modeled to be parabolic. From two point //p// and //p_old// with corresponding timestamps, the velocity //v// is computed.
13 -For a future point in time //t//, with //t=0 //being the timestamp of// p//, we can then approximately predict the corresponding ball position using the following formulas.
13 +For a future point in time //t//, with //t=0 //being the timestamp of// p//, we can then approximately approximately predict the corresponding ball position using the following formulas.
14 14  
15 15  [[image:attach:Bildschirmfoto von 2020-03-07 12-21-22.png]]
16 16  
17 -The incline of the playfield causes a vertical acceleration, which is modeled via a gravitational pull with the factor //g = sin(6°) * 9.81 m/s²//.
17 +The incline of the playfield causes a vertical acceleration, which is modeled via a graviatational pull with the factor //g = sin(6°) * 9.81 m/s²//.
18 18  The value of 6° is the incline of the playfield  measured on the physical device.
19 19  
20 20  == Prediction ==
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21 21  
22 22  ----
23 23  
24 -The controller calls the function //full_prediction// passing it two subsequent ball positions with timestamps. From these a ball trajectory is inferred as described above.
25 -Along the trajectory future times are stepwise tested for whether the corresponding predicted position is in the flipper range.
26 -Once a position inside the flipper range is found the search is continued both forwards and backwards in smaller steps in order to find a good enough estimate of the first and last possible time to hit the ball.
24 +The controller calls the function //full_prediction// passing it two subsequent ball positions with timestamps. From these a ball trajectory is infered as described above.
25 +Along the trajectory future times  are stepwisetested for whether the corresponding predicted position is in the flipper range.
26 +Once a position inside the flipper range is found the search is contiunued both forwards and backwards in smaller steps in order to find a good enough estimate of the first and last possible time to hit the ball.
27 27  If the trajectory does not intersect the flipper range within a certain prediction frame (see below "**Prediction parameters**") a value far enough into the future is returned, that will be overwritten by subsequent predictions.
28 28  
29 29  With the current configuration the controller uses the middle point in time between the first and last possible time in order to be most positive to hit the ball.
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48 48  )))|(((
49 49  window size for prediction - How far
50 50  
51 -into the future are predictions calculated at most.
51 +into the future are predctions calculated at most.
52 52  )))|(((
53 53  70ms
54 54  )))
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68 68  10
69 69  )))
70 70  
71 -When setting the PREDICTION_FRAME keep in mind that predictions, that reach multiple frames into the future, are likely to be overwritten, when new frames arrive and new predictions are calculated.
71 +When setting the PREDICTION_FRAME keep in mind, that predictions, that reach multiple frames into the future, are likely to be overwritten, when new frames arrive and new predictions are calculated.
72 72  Nevertheless it is reasonable to calculate predictions beyond the next frame in case a ball is not recognized on the next frame.
73 73  
74 74  With the default values up to 7 predictions are calculated if the ball is not predicted to be in flipper range roughly within the next two frames.
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79 79  
80 80  === Flipper range ===
81 81  
82 -The model of the area, where the the flippers can hit a ball is computed from a set of five points. These points are set to real world coordinates in meters
82 +The model of the area, where the the flippers can hit a ball is computed from a set of five points. These points are set to real world coordinates in meter
83 83  
84 84  and should not need further adjustment after the camera is correctly calibrated (see [[doc:World Coordinate System]]).
85 85  
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131 131  
132 132  Since the trajectory prediction does not consider collisions in general, we need a different kind of predictions for the inlanes,
133 133  i.e. the path feeding a falling ball from the playfield to the flippers, behind the slingshot.
134 -A ball is considered to be in an inlane, when it is in a rectangular area, with one edge given by the beginning of the flipper
134 +A ball is considered to be in an inlane, when it is in a rectangualar area, with one edge given by the begin of the flipper
135 135  and the other by a point at highest, outermost position of the angled part of the inlane.
136 136  
137 -In this area the vertical acceleration is deactivated in the prediction, since it would cause the prediction to assume the ball would slide into the wall.
138 -Though in reality there is still some acceleration, a simple linear prediction has shown to be practical in this less critical area.
137 +In this area the vertical accelleration is deactivated in the prediction, since it would cause the prediction to assume the would slide into the wall.
138 +Though in reality the still is some accelleration, a simple linear prediction has shown to be practical in this less critical area.
139 139  
140 140  [[image:attach:physics_inlane.png]]
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1 -71401594
1 +73072930
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1 -https://rtsys.informatik.uni-kiel.de/confluence//wiki/spaces/PP18/pages/71401594/Ball Physics
1 +https://rtsys.informatik.uni-kiel.de/confluence//wiki/spaces/PP18/pages/73072930/Ball Physics