| Date | November 2020 | Marks available | 3 | Reference code | 20N.1.HL.TZ0.11 |
| Level | HL | Paper | 1 | Time zone | no time zone |
| Command term | Explain | Question number | 11 | Adapted from | N/A |
Question
A company produces and sells domestic floor-cleaning robots.
The floor-cleaning robots can clean different surfaces like wood and carpet. The floor‑cleaning robots can also avoid obstacles or stairs.
Sensors are used by the processor that controls the floor-cleaning robot so that it can move safely.
A computerized security system for the company’s headquarters protects against unauthorized access using a swipe-card system. Each door has a swipe-card reader that is connected to the central computer. A database stores the IDs of all employees and the rooms they are allowed to access.
Describe two types of sensors used in the floor-cleaning robots.
Explain the function of an output transducer in this situation.
Identify one alternative computerized method that could be used in place of the swipe-card readers.
Describe how the method identified in (c)(i) functions.
Compare polling and interrupts as mechanisms for the swipe-card readers to interact with the central computer.
Markscheme
Award [4 max]
Proximity sensors/ range sensors;
Which are used to determine how close an object is to the sensor;
Optical sensors /Photocells and other photometric devices (often used in conjunction to proximity sensors);
which are used to detect the presence or absence of objects;
Tactile sensors / Contact sensors / Bumpers;
which are used to determine whether contact is made between sensor and another object;
Touch sensors;
which indicate when contact is made;
Force sensors;
which indicate the magnitude of the force with the object;
Machine vision;
which is used in robotics for inspection / parts identification / guidance (accept other uses);
Mark as 2 and 2
Award marks for other miscellaneous category of sensors which also are used in robots. For example, devices for detecting / measuring temperature / fluid pressure / fluid flow / electrical voltage / other physical properties/.
Award [3 max]
Output transducer is a device that accepts a (digital) signal from processor;
and turns it into a physical movement;
to make the floor cleaning robot move in different direction;
Award [1 max]
Any biometric device (finger print, eye scanner);
pin pads/Key pads on doors;
smartphone access(cloud-based) / mobile access control;
Award [3 max]
The answer to partc (ii) should match the candidate’s answer to part (i). For example:
a camera is used to scan the iris / finger print is scanned;
a database stores images (scanned iris/finger print of each employee) and the rooms they are allowed access to;
computer compares the scanned image to images stored in the database;
if found, the employee is allowed to enter;
Award [4 max]
Polling requires the computer to actively interact with each swipe device;
the computer periodically checks each swipe device whether it has requested service, if it does not require servicing, the computer examines the next one, etc. If one of them requires servicing, the computer switches to running the serving program;
polling will waste processing time whilst the device is idle;
whilst:
interrupt requires the device to flag the computer;
processor receives interruption signal and services the interrupt by calling the appropriate system subroutine for interrupt processing/interrupt handler;
and hence the computer’s time is not wasted whilst the swipe device is idle;
Examiners report
Mostly a well answered question.
Candidates mostly gave good responses for this question. Some candidates confused output transducers with sensors.
Almost all were able to identify one alternative method and to give a good description.
Almost all were able to identify one alternative method and to give a good description.
It is evident that students generally have problems with compare questions, describing the issues individually without performing any comparison, as was the case here.
