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@@ -45,7 +45,7 @@ camera frames.
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In the \textbf{Head Adjustment} part all necessary head movements are covered.
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In this part of the algorithm the head is rotated by a calculated angle, which
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depends on the ball yaw angle, which was provided by the \textbf{Ball
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Detection} part. Therefore, the ball should now be aligned in the center of
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Detection} part. Therefore, the ball should now be aligned in the centre of
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the robots' camera frames. If the angle between the head and the rest of the
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body is now below a specified threshold, the ball is locked and the algorithm
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stops, otherwise the algorithm continues with \textbf{Body Adjustment}.
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@@ -56,7 +56,7 @@ current movement. Then the robot starts to rotate around its z-axis depending
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on the current head yaw angle. To ensure that the head and body of the robot
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are aligned, like in the beginning of the whole algorithm, the head is rotated
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back into zero yaw. The algorithm continues then with another \textbf{Ball
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Detection}, to ensure that the robot is properly centered at the ball.
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Detection}, to ensure that the robot is properly centred at the ball.
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The proposed algorithm provided decent results during many test runs. It allows
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the robot to align itself to the ball fast, while some strategies are in place
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@@ -11,8 +11,8 @@ image itself needs to be transformed into HSV colorspace, so that the regions
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of interest can be extracted into a \textit{binary mask}. The contours of the
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regions can then be identified in a mask \cite{contours}, and the areas of the
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regions can be calculated using the routines from the OpenCV library. The
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center and the radius of the region with the largest area are then determined
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and are assumed to be the center and the radius of the ball.
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centre and the radius of the region with the largest area are then determined
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and are assumed to be the centre and the radius of the ball.
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\begin{figure}[ht]
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\includegraphics[width=\textwidth]{\fig ball-detection}
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@@ -30,13 +30,13 @@ binary mask with erosions and dilations, which allowed us to detect the ball
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even over long distances.
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The advantages of the presented algorithm are its speed and simplicity. The
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major downside is that the careful color calibration is required for the
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major downside is that a careful color calibration is required for the
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algorithm to function properly. If the HSV interval of the targeted color is
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too narrow, then the algorithm might miss the ball; if the interval is too
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wide, then other big red-shaded objects in the camera image will be detected as
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too narrow, the algorithm might miss the ball; if the interval is too
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wide, other big red-shaded objects in the camera image will be detected as
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the ball. A possible approach to alleviate these issues to a certain degree
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will be presented further in the section \ref{p sec field detect}. To
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conclude, we found this algorithm to be robust enough for our purposes, if the
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conclude, we found this algorithm to be robust enough for our purposes, if a
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sensible color calibration was provided.
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\section{Goal Detection}
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@@ -64,7 +64,7 @@ contours with the largest areas are considered further (in our experiments it
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was empirically determined that $N=5$ provides good results). Furthermore, all
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convex contours are rejected, since the goal is a highly non-convex shape.
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After that, a check is performed, how many points are necessary to approximate
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the remaining contours. The motivation behind this is the following: it is
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the remaining contours. The motivation behind this is the following: It is
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clearly visible that the goal shape can be perfectly approximated by a line
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with 8 straight segments. On an image from the camera, the approximation is
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almost perfect when using only 6 line segments, and in some degenerate cases
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@@ -74,7 +74,7 @@ of line segments to be approximated is probably not the goal. The preselection
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stage ends here, and the remaining candidates are passed to the scoring
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function.
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The scoring function calculates, how different are the properties of the
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The scoring function calculates, how different the properties of the
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candidates are from the properties, that an idealized goal contour is expected
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to have. The evaluation is happening based on two properties. The first
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property is based on the observation, that the area of the goal contour is much
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@@ -90,7 +90,7 @@ scoring function can then look like the following:
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The contour, that minimizes the scoring function, while keeping its value under
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a certain threshold is considered the goal. If no contour scores below the
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threshold, then the algorithm assumes that no goal was found. An important note
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threshold, the algorithm assumes that no goal was found. An important note
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is that the algorithm is designed in such a way, that the preselection and
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scoring are modular, which means that the current simple scoring function can
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later be replaced by a function with a better heuristic, or even by some
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@@ -104,7 +104,7 @@ Figure \ref{p figure goal-detection} demonstrates the algorithm in action. On
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the right is the binary mask with all found contours. On the left are the goal,
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and one contour that passed preselection but was rejected during scoring.
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One downside of this algorithm, is that in some cases the field lines
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One downside of this algorithm is that in some cases the field lines
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might appear to have the same properties, that the goal contour is expected to
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have, therefore the field lines can be mistaken for the goal. We will describe,
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how we dealt with this problem, in the section \ref{p sec field detect}.
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@@ -129,7 +129,7 @@ objects on the field are properly consumed.
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Such rather simple field detection has two important applications. The first
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one is that the robot should be aware, where the field is, so that it doesn't
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try to walk away from the field. Due to time constraints, we didn't implement
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this part of the behavior. The second application of field detection is the
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this part of the behaviour. The second application of field detection is the
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improvement of the quality of goal and ball recognition. As was mentioned in
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the section on ball detection, the current algorithm might get confused, if
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there are any red objects in the robot's field of view. However, there
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@@ -5,29 +5,29 @@ completed, which are:
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\begin{enumerate}
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\item Ball detection;
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\item Ball detection
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\item Goal detection;
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\item Goal detection
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\item Field detection;
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\item Field detection
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\item Turning to ball;
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\item Turning to ball
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\item Distance measurement;
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\item Distance measurement
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\item Approach planning;
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\item Approach planning
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\item Ball approach;
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\item Ball approach
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\item Goal alignment;
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\item Goal alignment
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\item Ball alignment;
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\item Ball alignment
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\item Kick.
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\item Kick
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\end{enumerate}
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In this chapter we will give our solutions to the problems posed by each of the
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milestones, and at the end the resulting goal scoring strategy will be
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presented. We will now start with the lower level detection milestones and
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will gradually introduce higher level behaviors.
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will gradually introduce higher level behaviours.
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@@ -56,15 +56,14 @@ to ensure their proper functioning on the robot.
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\section{Rejected Software Alternatives}
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Here we will briefly discuss what alternative options were available for the
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choice of the base framework, and why we decided not to use those. One
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choice of the base framework and why we decided not to use those. One
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available option was the official \textit{NAOqi C++ SDK}. Being based on the
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C++ language, this SDK can naturally be expected to have better performance and
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be more resource-efficient, than the Python-based version. We still chose the
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C++ language, this SDK can naturally be expected to have better performance and to be more resource-efficient, than the Python-based version. We still chose the
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Python SDK, because C++ is not particularly suitable for fast prototyping,
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because of the complexity of the language. It is also worth noting, that we
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never really hit the performance constraints, that couldn't have been overcome
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by refactoring our code, but in the future it might be reasonable to migrate
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some of the portions of it to C++.
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some portions of it to C++.
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Another big alternative is \textit{ROS} \cite{ros} (Robotic Operating System).
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ROS is a collection of software targeted at robot development, and there exists
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@@ -79,7 +78,7 @@ in ROS, it should be possible in the future to incorporate our work into ROS.
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Finally, as was already mentioned in the introduction, \textit{B-Human
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Framework} is a popular choice for beginners, thanks to the quality of the
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algorithms and good documentation. However, B-Human has been in development
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over many years and is therefore a very complex system. The amount time needed
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over many years and is therefore a very complex system. The amount of time needed
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to get familiar with the code, and then to incorporate our changes would have
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been too big, for this reason we decided to use the simpler option as a
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been too big. For this reason we decided to use the simpler option as a
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starting point.
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