Marble Maze

This Marble Maze tutorial shows how to use image processing and custom path planning to solve the maze by rolling a white marble from any starting point to a defined end point within the maze.

In this tutorial we use the setup from a partner site Tele Toyland called the Marble Maze. The goal of the Marble Maze is to command the platform from over the web to pan or tilt in order to solve the maze by moving the white marble from the start point in the maze to the end point. The trick with this installation is that you need to take into account that the ball will not stop unless there is a Lego brick in its path and that the ball does not always roll in a straight line nor stop exactly where desired. Thus while the maze does not appear to have many "walls" in the maze it is nevertheless a maze and requires some strategic thought to solve.

The task of this tutorial was to take the manual web interface and create a RoboRealm application that could solve the maze and move the ball from the start to the end. This required no additional hardware than is currently functioning. There is already an overhead camera and a servo board controller (in this case a Parallax USB servo controller) so the hardware build is already done.

The main task of automatically solving this maze is to process the image in order to create a idealized model of the maze and then solve the path planning issue using that model. Using the overhead camera we can acquire an image from the maze to process before each move is made. But first let's see what the maze looks like from the overhead camera's point of view.

The image above shows the view from the overhead camera looking down at the maze. The main part of the maze is the green background which is the "floor" of the maze. The gray Lego blocks outline the border of the maze. The inner blue blocks are the maze walls. The white ball can be seen in the upper left corner with the destination goal in the lower left specified by the red square.

On first view you can notice that the camera is not perfectly centered above the square maze. Our ideal model of the maze would be a perfect square. In order to align the image better we have to start the image processing part of the tutorial.