Changes for page Ball Physics

Last modified by Soeren Domroes on 2025/01/30 12:18

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From 3.1 to 2.1 From 13.1 to 12.1

From version 12.1

edited by stu104225
on 2020/03/09 11:13

Change comment: There is no comment for this version

To version 3.1

edited by stu104225
on 2020/03/03 18:55

Change comment: There is no comment for this version

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@@ -1,140 +1,55 @@
--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.
--The code for what is described in this section can be found in the files "physics.cpp" and "physics.h".
++\\
++== Task ==
++The ball physics model is meant to do things ...
--{{toc/}}
++\\
--== Ball trajectory ==
--
------
--
--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.
--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.
--
--[[image:attach:Bildschirmfoto von 2020-03-07 12-21-22.png]]
--
--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//.
--The value of 6° is the incline of the playfield  measured on the physical device.
--
--== Prediction ==
--
------
--
--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.
--Along the trajectory future times  are stepwisetested for whether the corresponding predicted position is in the flipper range.
--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.
--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.
--
--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.
--The computed velocity is also passed to the controller and used is some more advanced  tactical decisions like catching balls.
--
  == Configuration ==
------
++=== Points of interest ===
--=== Prediction parameters ===
++\\
--(% class="wrapped" %)
--|=(((
--Parameter
--)))|=(((
--Description
--)))|=(((
--Default value
--)))
--|(((
--PREDICTION_FRAME
--)))|(((
--window size for prediction - How far
++[[image:attach:physics_points.png]]
--into the future are predctions calculated at most.
--)))|(((
--70ms
--)))
--|(((
--PREDICTION_STEP_SIZE
--)))|(((
--size of the steps for the forward search
--)))|(((
--10ms
--)))
--|(((
--REFINEMENT_FACTOR
--)))|(((
--The prediction step size for the reverse search is
--PREDICTION_STEP_SIZE divided by REFINEMENT_FACTOR.
--)))|(((
--10
--)))
++=== Flipper range ===
--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.
--Nevertheless it is reasonable to calculate predictions beyond the next frame in case a ball is not recognized on the next frame.
++\\
--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.
++\\
--The REFINEMENT_FACTOR is also the worst case number of predictions calculated during the reverse search part of the prediction process.
++\\
  \\
--=== Flipper range ===
++[[image:attach:physics2.png]]
--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
++\\
--and should not need further adjustment after the camera is correctly calibrated (see [[doc:World Coordinate System]]).
++=== Inlane Area ===
--The values for the left flipper are set to be symmetrical.
++[[image:attach:physics_inlane.png]]
--[[image:attach:physics_points.png]]
++\\
--(% class="wrapped" %)
--|=(((
--Point#
--)))|=(((
--Description
--)))
--|(((
--1
--)))|(((
--center point of the circle that the flippers tip moves o
--)))
--|(((
--2
--)))|(((
--highest point a ball can be at when it hits the resting flipper
--)))
--|(((
--3
--)))|(((
--lowest point a ball can be at when it hits the resting flipper
--)))
--|(((
--4
--)))|(((
--lowest point a ball can be at when it hits the fully triggered flipper
--)))
--|(((
--5
--)))|(((
--highest point a ball can be at when it hits the fully triggered flipper
--)))
++=== Prediction parameters ===
  \\
--From these points an area, where the ball is deemed to be hittable, is computed.
++\\
--[[image:attach:physics2.png]]
++\\
  \\
--=== Inlane Area ===
++\\
--Since the trajectory prediction does not consider collisions in general, we need a different kind of predictions for the inlanes,
--i.e. the path feeding a falling ball from the playfield to the flippers, behind the slingshot.
--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
--and the other by a point at highest, outermost position of the angled part of the inlane.
++\\
--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.
--Though in reality the still is some accelleration, a simple linear prediction has shown to be practical in this less critical area.
++\\
--[[image:attach:physics_inlane.png]]
++\\
++
++\\

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Id

@@ -1,1 +1,1 @@
--73072930
++71401639

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@@ -1,1 +1,1 @@
--https://rtsys.informatik.uni-kiel.de/confluence//wiki/spaces/PP18/pages/73072930/Ball Physics
++https://rtsys.informatik.uni-kiel.de/confluence//wiki/spaces/PP18/pages/71401639/Ball Physics

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