Robotics Monday: Gantry Crane

Name of Model: NXT Gantry Crane

Created by: asztalosdani

Found at: http://www.youtube.com/watch?v=Pqq34F3BqX0&feature=player_embedded

Details: Here's a fun idea: what do you get when you mix a large, simple, and sturdy Technic frame, a spiffy PID controlled line follower, a 9V-motor controlled gripping device, and a winch setup that holds the gripper? You get this nifty crane setup. The construction of the top frame takes advantage of some of the more strangely shaped liftarms - note how the weight of the crane and cargo never makes the crane's frame bow. The "simple" line following portion of this is handles very smoothly - a sure sign that the program for it is using a PID control system (while proportional error correction is a bit more complex to program than the "classic project" style of zig-zagging line follower, I think that the performance improvement is worth it). You don't see string in many Technic and Mindstorms creations - truth be told, string is one of the few elements LEGO has a hard time manufacturing with a satisfactory amount of strength (I frequently use fishing line instead of official LEGO string) - but here, the 4 strings used as a winch have no problem holding up the gripper and moving it up and down smoothly. Personally, I'm a big fan of the way a 9V motor was used (with a visible 9V/NXT adapter cable) to control the gripping mechanism - when you just need to move something back and forth, you really don't need to use up one of the more expensive NXT motors (which come with built in rotation sensors). This is just a fantastic design overall, and it's even more impressive that it doesn't rely on rare special parts - it's all fairly standard Mindstorms and Technic parts and mechanisms, arranged well and programmed perfectly. Many of the models I feature here aren't really something I'd try building myself, but I'm inspired to give this one a try.