Question L6-C2

The question is about the sensors that can be used for the localisation of a robot working in a dark environment with light-absorbing walls. On the right there is an illustration of the robot, holding a spot for lighting in theaters. The question is: "You need to design a mobile robot used to generate light effects in theaters, stages, or galleries. The robot does not need to be fast and will mainly evolve on the side of the stages, but has to be equipped with a steerable light beam moving quickly. The typical environment is mainly dark with light-absorbing solid walls. You need to localize the robot, what sensor would you use? You have to keep the costs as low as possible.". Four answers are proposed:

Answer A. "Ultrasound distance sensor". This answer is correct, as ultrasound can be cheap and reflexion on “solid walls” could work.
In the explanation of the student we would like to see that they understand that this sensor seems the only one to work in dark environments, with light absorbing walls and without visual features.

Answer B. "Laser TOF sensor". This answer is wrong, as the laster TOF relies on reflected light signals and here we face a specifically designed light-absorbing environment.
In the explanation of the student we would like to see that they understand that there is a mismatch between the type of environment and the working mechanism of this sensor.

Answer C. "Stereo camera". This answer is wrong, as this sensor relies on visual features that can be visible. The information on the environment is that it is mainly dark and black, reducing the number of potential visual features.
In the explanation of the student we would like to see that they understand that there is a mismatch between the type of environment and the working mechanism of this sensor.

Answer D. "Custom localisation sensor based on external cameras and active infrared markers on the robot". This answer is wrong, as this localisation method can become very expensive, while the question insist on "You have to keep the costs as low as possible.".
In the explanation of the student we would like to see that they understand that this type of localisation is based on heavy equipment.
