Maze Construction

From Tekkotsu Wiki

Jump to: navigation, search

Robot mazes serve three functions. The primary one is to provide a simple, uncluttered sensory environment to make navigation easier. Within the maze you have absolute control over what the robot sees using its camera and/or rangefinder sensors. (This requires that the walls be high enough that the robot can't see over them.) The second function of a maze is to constrain the robot's motion to a specified area so it doesn't fall off the table or wander out of the lab. The third function is to make motion more challenging: the robot must be able to negotiate turns, avoid getting stuck in corners or dead end corridors, and, if the robot has a map, determine which landmarks should be visible from its current position.

Box Maze

A box maze at Spelman College

One of the fastest ways to make a maze is to purchase a set of packing boxes from a U-Haul store and line them up to form walls. You can get boxes in different shapes and sizes, and use some as obstacles as well as walls. You can also use the walls of the room to form part of your maze, as in the box maze below.

The drawbacks of the box maze are that it is labor intensive to take apart (all the boxes must be disassembled and pressed flat) and can take up a lot of room to store when not in use. Also, moving boxes are expensive relative to other potential maze materials such as posterboard. And the boxes typically have printing on them that may confuse the robot's vision system.


Posterboard Maze

A posterboard maze

Making a maze from posterboard takes a bit more work, but affords greater control over the size, shape, and visual appearance of the maze. Posterboard mazes are also lighter and cheaper than box mazes and can be folded up into a very compact space. Unlike the box maze, whose components are inherently stable, a posterboard maze relies on corners for stability.

Actual posterboard is somewhat fragile and doesn't hold up well to repeated assembly/disassembly. A better choice of materials is Plasticor, which is used in sign-making and can be purchased at art supply stores. Use 4mm opaque white Plasticor, not the thinner 2mm variety. You can order Plasticor in large sheets from distributors such as ArtSupply.com or Pioneer Supply. Use a box cutter to cut the sheets down to the size you need.

The sheets are fastened together using adhesive-backed velcro. Go to McMaster-Carr and purchase 2 inch wide, adhesive-backed nylon hook material (item # 9489K544) and adhesive-backed nylon loop material (item # 9489K878). Put 1 inch wide by 2 inch high strips of hook material at each corner of each panel. (Put it on the outside wall, not the inside wall.) Cut 2 inch wide by 2 inch high strips of loop material and use these to join the walls together. Do not remove the adhesive backing from the loop material when you use it to join maze walls.

You can use either Cylindrical Markers or Planar Markers in your maze. For planar markers, attach a square of velcro hook material to the wall at the desired marker heigh, and a square of loop material to the back of the marker.

Close-up of a planar marker on the wall of the maze
Tekkotsu world map representation of a posterboard maze showing the markers affixed to each wall segment.

Elevated Maze

An elevated maze at Carnegie Mellon University

You can make an elevated maze by putting several small tables together to form a complex shape. The advantage of an elevated maze is that it's easier to work with robots and other objects if you don't have to bend down to reach them; you can also reach farther into the maze when it's at roughly waist height. The disadvantage is that it takes time to assemble and disassemble the maze, so you'll need to find a semi-permanent space for it.

There are two ways to construct walls for an elevated maze. Short walls rest on the table surface. They can be supported and fixed to the table using metal L-brackets (available at any hardware store) and duct tape. The corners where two walls meet can be reinforced with metal right-angle pieces (hardware store) and/or duct tape. Tall walls rest on the floor, so they must be tall enough to extend past the table surface to the height you need. They don't require L-brackets for support; you can just join the panels together with tape or velcro, as in a posterboard maze, and let them rest against the edges of the table for additional support.

When choosing materials for the maze walls, consider the robot's vision system and camera characteristics. You might want to purchase sample sheets of several materials to see which works best in your lab. Both posterboard and Plasticor work well.

The floor of the maze can be covered with indoor/outdoor carpet to provide a uniform color and good traction for the robot. You can purchase inexpensive carpet at Home Depot or Lowes.