Lego Sweeper Robot

So… I seem to have a couple of unfinished posts waiting in my drafts section. I’ll try to see if I can take some time before long, and really get some updates done.

In the mean time, I’m following the summer course AM36, at the institute, which takes up most of my time. The course is about basic robot construction, dynamical agents and the transferral of human activities to the robots. So far our practical work has consisted of designing and building a prototype robot, for sweeping Lego bricks of a whiteboard. The robot is build in Lego, using the newest type of Mindstorm, the NXT.

The robot features two wheels driven by a motor each, which propels and turns the robot. There is a small wheel on the backside of the robot, for supporting the upright position. The robot had some size requirements (20×20 cm), so we build the robot in an upright position, rather than horizontal. For sweeping we attached a propeller underneath the robot, between the two main wheels. The propeller is driven by a third motor, connected by a gear, so the rotation would be fast enough to shoot bricks off the field.

The test of the robot was done in competition with the other 5 groups robots. The main criteria was sweeping the board clear of all the bricks, in the shortest time.

Three heats was done, two with predetermined starting positions and directions, and one were the team could choose the start position and direction freely. Additionally the robot was judged by a number of criteria like aesthetics, robustness and morphology.

Disappointingly our robot ended at a total fifth place, mostly due to an unfortunate human error in the third heat, involving mixing up the wires for one of the wheels and the propeller.

Sweeper Robot Video 1 shows the first heat, where the robot completes in 43 seconds. Sorry about the pour quality of my mobile phone video camera.

The controlling program for the robot, was made in the Lego Mindstorm graphical language, and was very simple. We were only allowed two use the light sensors, so the robot is simply looking for the black border of the field, and reacting to it. Basically just running forwards with a slight right turn, and back again when detecting the black border of the field. We later found that if we are going to build and program more robots, we are definitly going to program them in NXC, which would have allowed us to access the build-in PID regulator of the NXT, and driving a much more precise route.