Question L1-C4

The question is about the degrees of freedom and degrees of motion of a mobile robot. The question is: "A toy company wants to invest in robotics toy and requests you to evaluate three products and give them a feedback in terms of mobility, to have nice elegant movements and be able to dance. Which of the following sentence you can write in your report because it is correct?". Are depicted three robots: A: a robot base with 6 independent wheels but mounted as two tracks, 3 on each side. B: DJI RobotMaster S1 with aa base with 4 omnidirectional weeks (also called swedish wheeels). C: a Thymio differential drive educational robot.
Four statements are proposed:

Statement 1: Robots A and C have the same DOF and DOM, but A. has three times more actuators.
This answer is correct: A and C have the same architecture, meaning a differential drive, but A has 6 motors and C has 2 motors.
In the explanation we would like that the student mentions that both have differential drive architecture and that A has 6 motors although C has 2 motors.

Statement 2: With 4 motors, robot B is redundant.	
This answer is correct: 3 motors would be sufficient for the 3 DOF. The 4th motor is redundant.
In the explanation of the student we would like that the student mentions that 3 motors should be sufficient. 

Statement 3: Robot B has more DOM than the other two, allowing movements that cannot be made by A or C.
This answer is correct: B is holonomic, having 4 Swedish wheels (omnidrive). This allows the robot to turn and move in any direction directly, without manoeuvre.
In the explanation we would like that the student mentions that this robot is holonomic and has therefore more DOM.

Statement 4: With small irregularities of the ground, robot C will keep all wheels touching the ground, which is not the case of robot A.
This answer is correct: With 3 points of contact, C will always touch the ground with the two wheels. With six contact points, this is not guaranteed for robot A.
In the explanation we would like that the student mentions that robot C has 3 points of contact while A has 6, not ensuring contact with the ground for all wheels.


