Who here detests walking long distances to return your trays when dining in at the food court?
For those of you who do, not to worry! You are not alone.
Thankfully, with smart tray return robots becoming more prevalent in food courts, returning trays is more convenient than before.
These smart tray return robots not only make their way to our seats for us to return our trays, but they can even stop by with a cheery greeting to lift our spirits.
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However, there are some people in Singapore who have reservations about the use of smart tray return robots due to safety reasons. They are afraid that the tray return robot might collide with the diners and injure them.
To address the above concern, I will be discussing a question from the 2019 Nanyang Primary School (NYPS) P6 SA1 Examination Paper. From this question, we can gain an understanding of the working principles behind the smart tray return robots and find out if their worries are unfounded!
Let’s Take A Look At This Question
Source: Nanyang Primary School (NYPS) – 2019 P6 SA1 Examination Paper [Q37]
Thought Process
To answer the above question, we have to understand how the tray return robot works.
First, let us understand how the tray return robot responds when there is no one standing in front of it.
Scenario 1: When There Is No One Standing In Front Of The Robot
Remember what the question mentioned earlier? Whenever a person blocks light from reaching the light sensors at position Z, the robot will stop moving to allow trays to be slotted in.
At this point, I would pose the first question to my students:
“Will the light from the light sources in the food court be able to travel into the light sensors when there is no one standing in front of it?”
Think about it! Without anyone standing in front of the tray return robot, will light from the light sources in the food court be blocked from reaching its light sensors at position Z? No.
This means that light from the light sources in the food court can reach the light sensors at position Z as shown in the diagram below.
Here comes the second question:
“What does the tray return robot do if light from the light sources in the food court can reach its light sensors at position Z?”
When the light from the light sources in the food court is able to reach the tray return robot’s light sensors at position Z, this is a signal to the tray return robot that there are no incoming objects/persons.
As a result, the tray return robot is free to move to the diners’ tables for them to return their trays as shown in the diagram below.
In a nutshell:
After understanding what happens to the tray return robot when there is no one in front of it, let us find out what happens to the tray return robot when there is someone standing in front of it.
Scenario 2: When There Is Someone Standing In Front Of The Robot
Using the same set of guiding questions as in Scenario 1,
“Will the light from the light sources in the food court be able to travel into the light sensors when there is someone standing in front of it?”
As what the question mentioned, the moment someone is standing in front of the tray return robot, light from the light sources in the food court is blocked by the person as shown in the diagram below.
This means that the light from the light sources in the food court cannot enter the light sensors at position Z.
Here comes the second question:
“What does the tray return robot do if the light from the light sources in the food court cannot enter its light sensors at position Z?”
This is a signal to the tray return robot that there are objects/people in front of it and it will stop moving as shown in the diagram below.
“Why is it important for the tray return robot to stop moving when there are people in front of it?”
This prevents the robot from running into the people in front of it and injuring them.
In a nutshell:
Let’s Analyse The Question
“Explain why the light sensors have to be placed at position Z instead of Y.”
Since the light sensors have to be placed at position Z instead of Y, there must be an advantage of placing them at position Z over position Y.
To find out the disadvantage of placing the light sensors at position Y, let us identify the difference between positions Y and Z.
We can see that position Y is much higher than position Z.
Why is that an issue?
To answer the question above, we must first ask ourselves: what is the height of a tray return robot? Tray return robots are usually around 1.5 metres tall.
Scenario 1: When The Light Sensors Are At Position Y
Since Position Y is at the top of the tray return robot, which is around 1.5 metres tall, there will be people that are shorter than position Y, especially children.
“For people shorter than position Y standing in front of the tray return robot, would the light from the light sources in the food court be blocked by them from travelling into the light sensors at position Y?”
The answer is no. Thus, light from the light sources in the food court would still be able to travel into the light sensors at position Y as shown in the diagram below.
“Remember what happens to the tray return robot when light is able to travel into its light sensors?”
The tray return robot would continue moving forward and collide with the people shorter than position Y as shown in the diagram below, which may cause them to be injured.
So, is it wise to place the light sensors at position Y? Definitely not!
How about placing the light sensors at position Z then? Would it then be able to cater to people of different heights?
Scenario 2: When The Light Sensors Are At Position Z
Since position Z is placed at the base of the tray return robot:
“Is everyone (including those shorter than position Y) able to block light from reaching the light sensors at position Z when standing in front of the tray return robot?”
Definitely! Thus, the light from the light sources in the food court cannot enter the light sensors at position Z as seen in the 3 diagrams above.
“Do you recall what happens to the tray return robot when light cannot travel into its light sensors?”
The tray return robot will stop moving.
As a result, will it knock into anyone, short or tall? No.
We have now shown that the tray return robot is definitely safe to use, provided the light sensors are placed at position Z and not Y.
Suggested Answer
Some people may be shorter than position Y and may not be able to block light from travelling into the light sensors at position Y for the robot to stop moving.
Putting the light sensor at position Z ensures that people of different heights will still be able to block light from travelling into the light sensor for the robot to stop moving.
Summary
After discussing how the tray return robot works, I hope I have convinced everyone that the tray return robots are safe to use in food courts.
No matter how tall the person is, with the light sensor attached at the base of the tray return robot, they would be able to block light from entering the light sensors, stop the tray return robot from moving, colliding with them and injuring them.
An even more amazing feature is that if some cheeky diners choose to block the way of these tray return robots for an extended period of time, it will tell them to move aside!
This is to allow it to continue moving and facilitate the collection of trays from other diners.
💡 Fun fact: Did you know that light sensors have many other real-life applications?
They are used in factories to count the number of mass produced objects as well as in robot vacuums to prevent it from knocking into objects at home.
After reading this article, I hope that you now have more confidence in tackling unique application questions on Light Energy!
Stay tuned for more articles! 🙂
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