Three Motor Sumo Robot

An LDD Screenshot of the robot

This is a video from a Mindstorms class that I taught at InZone

This is a video from a Mindstorms class that I taught at InZone

I wanted to share my sumo robot with you. My sumo robot is pretty cool. In the scheme of things, there are better sumo robots, however, mine has proven to be decent and fun to work with. One of the things that makes my robot special is that it uses all three of the NXT motors for movement. This is accomplished with the third motor powering a differential which aides the other two motors. The other two motors each power a wheel directly. I have a Lego Digital Designer file so you can see it and build your own. The nifty part are the geometries that I used to make the three motor core solid. With lithium batteries, mine weighs in at 2.16 pounds which is right below the 2.2 maximum. You can get all the files for the robot here. The files include the Mindsensors firmware, NXT-G program, additional software blocks, and a Lego Digital Designer file. If I were to build another robot, I would change the pusher design so that there was a angled edge running on the ground. The Lego Technic beams have rounded edges which do not really make a good wedge to get under an opponent.

I programmed it in NXT-G. The program is a finite state machine. There are three parts of the program running at the same time. One part gets the values from the sensors, one part checks the state and then executes the state, and the other part is the logic which sets the state. The robot has the following states: forward, backward, turn left, turn right, or stop. Based on the sensor values coming in, the state is set and then executed. I am using the Mindsensors firmware which helps to make the operation smoother when compared to the stock firmware. I am also using the "mini blocks" which seem to be a bit better.

There are three programs for this robot. The first one is called JAYSUMOFINAL. It is a full sumo program meant to conform to the rules of official Lego sumo competitions. It has the 5 second countdown after the start and can choose the the initial turn direction. JAYSUMOEXPRESS is similar to the previous program except it does not have a countdown and the user doesn't choose the initial turning direction. The last program is called JAYSUMOPSPNX-4. It  is meant to be use with a Mindsensors PSP-Nx-v4 for remote control. To use this program, one simply unplugs the rear light sensor and plugs in the receiver. The receiver is easily mounted sideways in front of the NXT. This gives the user a slick and responsive interface for remote control operation.