LEGO MINDSTORMS Robots, Manual, Page: 30 / 226

Figure 2-6.
Hank's program
To create this program, enter the RIS software. Choose Program RCX from the main menu, then RCX Code. Use the menus on the left side of the screen to click and drag out different program
''blocks." If you're not familiar with this process, you should probably go back and take a look at LEGO's official documentation, either the printed material or the computer-based tutorial.
Once you have created the program, download it and run it. (You can download or save a program by right-clicking on the main program block.) If everything goes right. Hank should amble
around on your floor, trying to avoid things he bumps into. If you have pets, this would be a good time to introduce them to your new toy.
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Hank is a pretty simple robot, but you still may run into trouble:
• If your robot spins in place or goes backward instead of forward, you may need to adjust the wires that connect the motors to the outputs. Remove one of the wires and turn it 180° around. This
will reverse the direction of the attached motor. If the robot is moving backward instead of forward, turn both wires around.
• Hank may not run well on very thick carpet, because there's not much space between the bottom of the body and the floor.
Once you've got things running smoothly, read on. I'll describe Hank's most interesting features in the rest of this chapter.
Locomotion
Hank gets around in the world on a pair of treads, like a tank or a bulldozer. This is just one approach to the general problem of locomotion. Different designs have different merits—you should
choose a locomotion method based on what kind of terrain you're expecting your robot to encounter.
Treads
Hank's treads have some interesting properties. Foremost among these is zero turning radius, which is a fancy way of saying that a treaded robot can turn around in one place. (I'll explain why it's
a radius a little later.) Each tread is driven by one of the motors, so all you need to do to turn is move the treads in opposite directions at the same speed. This turning, however, is accomplished
with a good deal of friction. Both treads slip on the driving surface. Tanks in Veteran's Day parades can really chew up roads this way.
The large surface of the treads is one of their other assets. Treads are good for driving on jagged or slippery terrain. Hank should do pretty well driving over uneven obstacles, like a small pile of
LEGO bricks.