C - Underground Exploration

First, we need to make a system of tunnels to test the robot exploration program with. You can do this individually, or in groups.

The tunnel system under the planet is made of straight walls all at 90 degrees to each other, like the maze in the picture.

For now, make a small section of maze like the second picture - just a simple right turn.

You can use books, cardboard and tape or anything else sensible you can think of! Make sure the walls are taller than your robot.

The walls must be at least 25cm apart so your robot has room to turn - this is very important!

Setup your robot like the picture - make sure everything is in exactly the right place or your robot won't balance properly.

The left motor should be in M1, the right motor in M2, and the switch in A.

The trackball goes directly underneath the switch.

Let's write a simple program to make the robot navigate the right turn. Your program should:

Drive forwards

If the switch is pressed, reverse slightly, then turn right 90 degrees

Drive forwards again

You should just need 1 IF block to complete this - check the second image for a hint of the blocks required if you need to.

Be sure to test it properly on your maze section until it works reliably!

When your robot is able to make the right turn correctly, try running it through the maze section from the other direction, to try a left turn.

Did it behave how you expected?

Your robot probably turned right 90 degrees, hit the other wall, turned right 90 degrees again and went back where it came from!

This is no good - the robot will never make it through the tunnels! Can you think how to fix it?

To fix this, we need to write a program that can work out whether we need to turn left or right.

If you think you know how to do this, great - try it out! If not, here is a way that might work:

If the switch is pressed, always turn right 90 degrees.

Move forward a small amount, and if the switch is pressed again, we must be at a left turn!

Spin 180 degrees, then continue driving forwards

Check out the video for how your robot should handle the left turn if you're still not sure!

Here's a hint - you will need to put an If block inside another IF block.

Now our robot can handle almost anything underground, but what about a dead end?

Add another IF block to your program to check if the switch is being pressed after the 180 degree turn, and if it is, turn back!

There's some example code for a program that can deal with left and right turns in the second image if you are stuck.

Add another wall to your test maze so you can properly test your code!

Time for a real test of your program!

As a group, combine all the small maze pieces into one large maze, with at least one left turn, one right turn and a dead end. The bigger the better!

Time each other's robots and see who can get through the maze the fastest!

You will probably want to do some test runs first so you can adjust your program so it is as fast as possible.

For the super advanced explorers, you could try using two switch modules like in the obstacle avoidance challenge, to see if you can do the maze any faster.

You could also experiment with the positioning of the wheels, switches and trackball on your robot to see which positions work the best.

In short, try experimenting with anything you think might improve the performance of you robot!