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Changes for page Ball Physics

Last modified by Soeren Domroes on 2025/01/30 12:18
From version 3.1
edited by stu104225
on 2020/03/03 18:55
Change comment: There is no comment for this version
To version 9.1
edited by stu104225
on 2020/03/07 12:25
Change comment: There is no comment for this version

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... ... @@ -1,55 +1,131 @@
1 +The **ball physics model**'s main objective is to provide a point in time to the controller, when the ball is predicted to be hittable, in order to not let the ball fall into the drain.
2 +
1 1  \\
2 2  
3 -== Task ==
5 +\\
4 4  
5 -The ball physics model is meant to do things ...
6 6  
7 -\\
8 8  
9 -== Configuration ==
9 +{{toc/}}
10 10  
11 -=== Points of interest ===
11 +== Ball trajectory ==
12 12  
13 -\\
13 +----
14 14  
15 -[[image:attach:physics_points.png]]
15 +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.
16 +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.
16 16  
17 -=== Flipper range ===
18 +[[image:attach:Bildschirmfoto von 2020-03-07 12-21-22.png]]
18 18  
19 -\\
20 +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//.
21 +The value of 6° is the incline of the playfield  measured on the physical device.
20 20  
21 -\\
23 +== Configuration ==
22 22  
23 -\\
25 +----
24 24  
25 -\\
27 +=== Prediction parameters ===
26 26  
27 -[[image:attach:physics2.png]]
29 +(% class="wrapped" %)
30 +|=(((
31 +Parameter
32 +)))|=(((
33 +Description
34 +)))|=(((
35 +Default value
36 +)))
37 +|(((
38 +PREDICTION_FRAME
39 +)))|(((
40 +window size for prediction - How far
28 28  
29 -\\
42 +into the future are predctions calculated at most.
43 +)))|(((
44 +70ms
45 +)))
46 +|(((
47 +PREDICTION_STEP_SIZE
48 +)))|(((
49 +size of the steps for the forward search
50 +)))|(((
51 +10ms
52 +)))
53 +|(((
54 +REFINEMENT_FACTOR
55 +)))|(((
56 +The prediction step size for the reverse search is
57 +PREDICTION_STEP_SIZE divided by REFINEMENT_FACTOR.
58 +)))|(((
59 +10
60 +)))
30 30  
31 -=== Inlane Area ===
62 +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.
63 +Nevertheless it is reasonable to calculate predictions beyond the next frame in case a ball is not recognized on the next frame.
32 32  
33 -[[image:attach:physics_inlane.png]]
65 +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.
34 34  
67 +The REFINEMENT_FACTOR is also the worst case number of predictions calculated during the reverse search part of the prediction process.
68 +
35 35  \\
36 36  
37 -=== Prediction parameters ===
71 +=== Flipper range ===
38 38  
39 -\\
73 +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
40 40  
41 -\\
75 +and should not need further adjustment after the camera is correctly calibrated (see [[doc:World Coordinate System]]).
42 42  
43 -\\
77 +The values for the left flipper are set to be symmetrical.
44 44  
45 -\\
79 +[[image:attach:physics_points.png]]
46 46  
47 -\\
81 +(% class="wrapped" %)
82 +|=(((
83 +Point#
84 +)))|=(((
85 +Description
86 +)))
87 +|(((
88 +1
89 +)))|(((
90 +center point of the circle that the flippers tip moves o
91 +)))
92 +|(((
93 +2
94 +)))|(((
95 +highest point a ball can be at when it hits the resting flipper
96 +)))
97 +|(((
98 +3
99 +)))|(((
100 +lowest point a ball can be at when it hits the resting flipper
101 +)))
102 +|(((
103 +4
104 +)))|(((
105 +lowest point a ball can be at when it hits the fully triggered flipper
106 +)))
107 +|(((
108 +5
109 +)))|(((
110 +highest point a ball can be at when it hits the fully triggered flipper
111 +)))
48 48  
49 49  \\
50 50  
51 -\\
115 +From these points an area, where the ball is deemed to be hittable, is computed.
52 52  
53 -\\
117 +[[image:attach:physics2.png]]
54 54  
55 55  \\
120 +
121 +=== Inlane Area ===
122 +
123 +Since the trajectory prediction does not consider collisions in general, we need a different kind of predictions for the inlanes,
124 +i.e. the path feeding a falling ball from the playfield to the flippers, behind the slingshot.
125 +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
126 +and the other by a point at highest, outermost position of the angled part of the inlane.
127 +
128 +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.
129 +Though in reality the still is some accelleration, a simple linear prediction has shown to be practical in this less critical area.
130 +
131 +[[image:attach:physics_inlane.png]]
Confluence.Code.ConfluencePageClass[0]
Id
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1 -71401639
1 +71401661
URL
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1 -https://rtsys.informatik.uni-kiel.de/confluence//wiki/spaces/PP18/pages/71401639/Ball Physics
1 +https://rtsys.informatik.uni-kiel.de/confluence//wiki/spaces/PP18/pages/71401661/Ball Physics