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Semi-Autonomous Battle Robots

For the final project in the Advanced Robotics Club that I teach at our local middle school, I made up a challenge called SARB: Semi-Autonomous Robot Battle, which is an extension of Sumo-like challenges. Although we used RCX kits (because we have a bunch), it could just as easily be done with the NXT, so I will explain it here and reference several NXT projects on that you could use to get started with a challenge like this using the NXT.

For the fighting ring, (er, ahem, "Playing Surface"), I used our FLL table, turned the mat upside down, and then used electrical tape to mark out an elongated octagon-shaped ring. Like Sumo, one of the goals is to push the other robot outside of the ring. However, the SARB robots can also have some kind of striking (motorized) weapon and get points for successful strikes on the other robot. Like a Karate match, only a "controlled strike" will count as a point. Random spinning/flailing weapons that happen to make contact with the other robot do not count. The strike must be triggered by a sensor that had a reason to hope it might hit the other robot. We did the scoring like this:
  • 1 point for a controlled strike that makes contact with the other robot
  • 2 points for a controlled strike that does damage to the other robot (damage is much more likely with the typically studded building of the RCX kit)
  • 3 points if the other robot goes completely outside the ring (due to your push or accidentially on its own)
Then to make it even more complicated (this was the Advanced Robotics Club, after all), each robot was required to be operated in two different modes: fully autonomous (no remote control), and semi-autonomous, with a single touch sensor on a long wire as a simple remote control. A match was done by putting robot A in fully auto mode vs. robot B in semi-auto mode until one robot scores at least 5 points, then reversing it so that robot A is in semi-auto mode and robot B is in fully auto mode until again a robot scores 5 points, then the total score for each robot is the total of their scores from each half of the match.

One of the reasons for this strange arrangement (aside from making it harder) is that it means that a total of only 1 wire is leading from the hands of the kids to the playing field at any given time, which greatly reduces wire tangling problems. In my Beginning Robotics Class, the final project is two or three-button fully remote controlled (RCX) battle bots, which is a blast, but always ends in a mass of tangled wires...

So, given the requirements, the students were left to figure out how to make the best of a fully auto mode and a semi-auto mode, build it, and program it. Several different strategies are possible in each mode. Here are a few examples:

Fully Autonomous: A light sensor keeps the robot inside the ring with a simple driving strategy such as the Mini Sumo Bot, and a front-bumper touch sensor such as the Bumper Car triggers the weapon when you collide with the other robot. The robot on the right in the picture above is doing this, although its weapon has been damaged and is dangling...

Semi-Autonomous: A light sensor keeps the robot inside like Mini Sumo Bot, and the remote control touch sensor allows the kids to trigger the weapon (the robot on the left in the picture is doing this).

Semi-Autonomous: The remote control touch sensor is used to drive/steer like the 1-Button Remote Control robot, and a second touch sensor on a front bumper triggers the weapon.

Semi-Autonomous: For the programming whizzes, a single button remote control could control both the driving and the weapon, as for the Hammer Car.

There are several other possibilities, and clearly the NXT's ultrasonic senor could add another possibility (as long as only one robot was allowed to use it at a time -- perhaps the fully autonomous one). For wired remote control using the NXT, it might be a good idea to use 3rd party longer wires, or the old RCX touch sensors and long wires if you have them. You could also just do a straight fully autonomous battle with no wires.

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