Lego Mindstorms EV3 ping pong challenge

Bournemouth University’s STEM outreach program came to visit Purbeck School on Monday, and bought with them 15 Lego Mindstorms EV3 kits. The kits had been made into pre-assembled robots with a Large Servo motor for lateral movement, and a medium motor to lift the arm assembly.  They had ultrasound sensors for distance sensing, and an IR sensor for manual control via the IR Beacon.

The brief of the day was simple: Write code for a Robot to be able to play a game of Ping Pong against another robot.  The challenge turned out to require problem solving, mathematics,  iterating, collaboration, failure, resilience and sabotage.

Mean looking Ping-Pong robots.   Note the Ultrasound sensor at the front.  The whole paddle assembly flipped up when the motor was set to turn.
Mean looking Ping-Pong robots. Note the Ultrasound sensor at the front. The whole paddle assembly flipped up when the motor was set to turn.

The challenge was really well structured, with the students learning the basics of connecting, writing code blocks and downloading them to the brick, and within about 20 minutes of starting, most groups had control of the servo motors, and shortly afterwards, they were able to add another loop to their program to control the flipper.  They had to figure out the correct number of degrees to rotate the arm in order for an efficient flip! IMG_1784

The code challenges were well-thought out, and got the students to learn the rudiments of controlling the robot successfully by thinking about how far the robots had to move by setting rotation limits on the motors, and learning to use logic and loops to make the robots respond to the infrared remotes.  They had time to test the robots out in the test arena,  and make sure that the robots were responsive to input, and could also hit the ball with the paddle.  There was  a key trade-off between Power and Speed at which the paddle moved, that the students had to find to hit the sweet spot.

Customisation was also a large part of the day, with some groups recording audio samples, or drawing their own pictures, or playing short musical sequences at the press of a button.  3 groups had ‘entrance moves’ and intimidating aggressive moves.

Once the matches began, it became evident that there were issues with IR interference from other groups since the EV3 kits limit you to 4 channels, and even in a large room, there was significant crosstalk between the groups.  (There was also a good amount of comedy sabotage to be had).

Playing the great game.  Getting the ball off the end of the table gains you a point.  The IR beacon was used to control the robots.
Playing the great game. Getting the ball off the end of the table gains you a point. The IR beacon was used to control the robots.
A Match in progress.  The board shows the channel choices.  Teams had to reprogram their 'bots to change channels between games .
A Match in progress with teams that finished 2 and 3rd.

There were 20+ matches, the competetive element was very strong and the quality of the sport got much better as the day went on.  In particular, the single-member teams did particularly well, ranking in 3rd and 4th place even though they had no previous experience with the NXT-G programming environment.   There had to be an overall winner, and team Virginia Tech prevailed in the end.

IMG_1814
The winning team. Their robot’s unique skill was to shout ‘BANTER!’ during matches. It also played a nice jazzy arpeggio. They managed to overcome significant issues with controlling their robot.

We hope to be involved with Naomi and the STEM outreach team again.  The feedback was really positive from the students, and this would work really well with a younger cohort of students.

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