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Changes for page Ball Physics

Last modified by Soeren Domroes on 2025/01/30 12:18
From version 9.1
edited by stu104225
on 2020/03/07 12:25
Change comment: There is no comment for this version
To version 1.1
edited by stu104225
on 2020/03/03 18:03
Change comment: There is no comment for this version

Summary

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Content
... ... @@ -1,131 +3,55 @@
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 -
3 3  \\
4 4  
5 -\\
3 +== Task ==
6 6  
5 +The ball physics model is meant to do things ...
7 7  
7 +\\
8 8  
9 -{{toc/}}
10 -
11 -== Ball trajectory ==
12 -
13 -----
14 -
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.
17 -
18 -[[image:attach:Bildschirmfoto von 2020-03-07 12-21-22.png]]
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.
22 -
23 23  == Configuration ==
24 24  
25 -----
11 +=== Points of interest ===
26 26  
27 -=== Prediction parameters ===
13 +\\
28 28  
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
15 +[[image:attach:physics_points.png]]
41 41  
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 -)))
17 +=== Flipper range ===
61 61  
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.
19 +\\
64 64  
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.
21 +\\
66 66  
67 -The REFINEMENT_FACTOR is also the worst case number of predictions calculated during the reverse search part of the prediction process.
23 +\\
68 68  
69 69  \\
70 70  
71 -=== Flipper range ===
27 +[[image:attach:physics2.png]]
72 72  
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
29 +\\
74 74  
75 -and should not need further adjustment after the camera is correctly calibrated (see [[doc:World Coordinate System]]).
31 +=== Inlane Area ===
76 76  
77 -The values for the left flipper are set to be symmetrical.
33 +[[image:attach:physics_inlane.png]]
78 78  
79 -[[image:attach:physics_points.png]]
35 +\\
80 80  
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 -)))
37 +=== Prediction parameters ===
112 112  
113 113  \\
114 114  
115 -From these points an area, where the ball is deemed to be hittable, is computed.
41 +\\
116 116  
117 -[[image:attach:physics2.png]]
43 +\\
118 118  
119 119  \\
120 120  
121 -=== Inlane Area ===
47 +\\
122 122  
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.
49 +\\
127 127  
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.
51 +\\
130 130  
131 -[[image:attach:physics_inlane.png]]
53 +\\
54 +
55 +\\
Confluence.Code.ConfluencePageClass[0]
Id
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1 -71401661
1 +71401601
URL
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1 -https://rtsys.informatik.uni-kiel.de/confluence//wiki/spaces/PP18/pages/71401661/Ball Physics
1 +https://rtsys.informatik.uni-kiel.de/confluence//wiki/spaces/PP18/pages/71401601/Ball Physics