Question L1-C6

The question is about the capabilities and configuration of the Astolfi controller. The question is: "You need to make a demonstration of Thymio moving in a narrow corridor described in the
figure on the right, without touching the walls. You have the position of Thymio through a tracking system and you have the path that the robot should follow, composed of 5 way-points (WP0-WP1-WP2-WP3-WP4). WP0 is the start, WP4 is the goal. You have to choose a method to follow the path. What among the following statements are correct (several answers possible)?". A picture illustrates the path, made of corridors with 90-degrees angles, and the start and goal points. The corridors are narrow and allow just the robot to move. Therefore the changes of orientations at the corners are quite tricky to do. Three possible answers are proposed:

Answer A: "I can use the Astolfi controller on each segment (START – WP1, then WP1- WP2,…) with an angle at the of each segment oriented toward the next WP (excepted goal, direction aligned with segment)". 
This answer is wrong: the orientation at the end of the segment will force the Astolfi controller to have a large curve to reach the WP with the correct angle, and this will generate a collision with the walls.
In the explanation of the student we would like that the student mentions that the large curve made by the controller to match the angle at the end of the segment is not compatible with the size of the corridors. 

Answer B: "I can use the Astolfi controller on each segment (START – WP1, then WP1- WP2,…) with an angle at the of each segment aligned with the last WP (excepted start, direction aligned with segment)"
This answer is wrong: the orientation at the end of the segment will force the Astolfi controller, at the beginning of the next segment, to make a large curve to reorient toward the next WP, and this will generate a collision with the walls.
In the explanation of the student we would like that the student mentions that the large curve made by the controller at the beginning of the next segment is not compatible with the size of the corridors. 

Answer C: "I can use the Astolfi controller without considering the angle at the target WP, then turning on place with a regulator, before starting the next segment."
This answer is correct: Using the Astolfi only on a straight line can allow to stay on the line without touching the walls. The turning on the spot between the segments allows to respect the size of the corridors.
In the explanation of the student we would like that the student mentions that this type of movement (straight movement and the turn on the spot) is compatible with the geometry of the corridors.
