Stem fair project Can LEGO MINDSTORM robots detect and react to objects within a certain range?

What is the challenge and What are the constraints?  The challenge was to build a robot that guarded something, possibly a room or an object.  The constraints were to use parts from an NXT LEGO Mindstorm set to build a semi-intelligent robot.

Ideas for designs  Some possible ideas were:  1. Build a robot that moved around, patrolling the area with an ultrasonic sensor that would allow the robot to see. If it saw an object within a certain distance, it would first give a warning, then attack with its robot teeth by snapping its jaws.

Ideas for designs  2. Build a robot that was stationary, and had an ultrasonic sensor, enabling the robot to see. It would flash a warning blue light out of the color lamp installed on it, then give a verbal warning, and if the object did not move, the robot would shoot plastic balls out of a chute and continue to do so until the object moved. When the object moved, the robot would say, “ Lost object”.

Sketches of ideas

Which idea should I choose?  I decided to make Robot2 instead of Robot1, because I imagined a situation where, if I had chosen Robot1, the robot would be guarding a room. If the room happened to be in a hallway, Robot1 might patrol the area and then sense the wall, in which case it would attack the wall.  I thought also shooting balls might be more useful than having a robot attack with biting, because then the robot would protect a larger area.

Needed materials These are the main parts I will use for my robot. These are the names of the parts, from top left going clockwise: Ultrasonic sensor, Color sensor/ color lamp, ball shooter with balls, and the NXT computer. I will also need many other small parts for this robot, including axels, connectors, and a few straight or elbow pieces, along with some wires to connect the NXT computer to the sensors and motors.

Needed materials  I will also need 3 motors, two for the traction wheels, which are mostly decorative, and one for poking the balls out of the ball shooter.

Building the robot  Here are some pictures of me building Robot2.

What changes to robot2 can I make?  The changes I made to robot2 were:  I made it so that the color lamp changed different colors then originally programmed.  I attached the ball shooter in a more convenient spot.  I made the ultrasonic sensor sense objects within 40cm instead of 30cm.

Robot2

Did my robot complete the challenge?  I think that Robot2 completed the challenge, because 1) It can detect objects, and when I tested it out it detected the object. 2) It reacted to the object, by shooting balls out of the ball shooter 3) There was a certain range in which the objects had to be in for them to be sensed.