Guard Robot Project

© 2006 Carnegie Mellon Robotics AcademyDesigned for use with the LEGO MINDSTORMS® Education NXT Software and Base Set #9797

Guard RobotProject


Opening ActivityWhat are some simple, common sense ways to maintain security in an office building?


SecuritySecurity in an office setting remains important to both individuals and the company

– Workers typically leave portable items of moderate value (briefcases, radios, CDs, etc.) at their desks

– The company has items of significant value in every office (computers, specialized equipment like cameras) Typical Office Desk

Can you spot items that are less secure?


SecurityInformation is also extremely important to keep safe

– Company secrets

– Customer information

– Employee data

– Computer passwords

– Credit card information

– Legal and other sensitive documents

Sensitive InformationSensitive information was hidden in this publicly

released document. What if the unmodified versionwere to be stolen from an unsecured office?


SecuritySimple measures can help to reduce “crimes of opportunity”

– Report suspicious persons– Keep track of people entering

and leaving the building– CLOSE AND LOCK DOORS

Open DoorIt doesn’t matter how many locks you have

if you forget to close the door…


Security

Checking doors can be tedious and expensive

– How many doors are in your school or home?

– How long would it take to check them all?

– How much would you have to pay someone trustworthy to check every one of those doors every night, including on weekends?

– Could a robot save money here? Door CheckChecking all the doors in a facility

can take a very long time


Guard Robot:Programming Review

Switch BlockLoops

GUI image courtesy of Cybermotion


Switch Block: Ultrasonic SensorSwitch Blocks… allow the program to observe a value, and choose between different paths of code to follow, based on the observed value.

Sensor Switch Blocks… check a specified sensor to determine which group of blocks to run.

Ultrasonic Sensor Switch Blocks… check an Ultrasonic Sensor reading against a pre-set threshold to decide which blocks to run. If the sensor reading is less than the threshold, the top “near” (flower) branch will run. If the sensor reading is greater than the threshold, the block will run the bottom “far” (mountains) branch.

Keep Your DistanceBased on the value of the Ultrasonic Sensor,

this Switch will either move backward (if the sensor value is less than the threshold),

or move forward (if the sensor value exceeds the threshold)


Infinite Loop

The Loop Block runs the blocks inside it over and over again, until a certain stopping condition is met.

The infinite loop or “forever” loop has no stopping condition, and therefore will repeat the blocks inside over and over, forever.

Back and ForthThe loop causes the robot to repeat the

forward-then-back motion forever


• Simple practices like closing doors when leaving the office can help to reduce significant security risks

• It is time-consuming and tedious to check all the doors by hand

• A robot can potentially save time and resources by performing this task

Summary

• The Ultrasonic Sensor Switch Block lets you choose which code to run based on the value of an Ultrasonic Sensor versus a threshold

• Loops run the same piece of code over and over again until a certain condition is met

Documents

Guard Robot Project