NXT Alpha Rex building instruction

The Alpha Rex comprises probably the most complex of the RoboCenter series of robots, both from the mechanical design perspective and the software programming perspective. The following discussion will concentrate on software programming of the Alpha Rex. The program described below illustrates two advanced programming techniques: state machines and abstraction. A state machine design handles basic movements such as tilting side to side and striding the robot’s feet forward and backward. Abstraction handles combining the basic movements into more complex movements, such as walking forward and turning right and left.

The inspiration for this program comes mainly from sources other than the Mindstorms RoboCenter software examples for the Alpha Rex. The RoboCenter examples perform basic movements such as walking forward and turning. However the examples are rather inadequate when it comes to combining basic movements into more complex movements, such as having your Alpha Rex move in a figure eight pattern. Furthermore, including such functionality as having the Alpha Rex walk around avoiding obstacles behooves the application of more advanced programming techniques.

The following sections describe these techniques in much more detail. The final section, following the description of these techniques, presents the development of a complete program for avoiding obstacles.
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Download AlphaRex building instruction(pdf)
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Download AlphaRex obstacle(zip)

Refference :* http://www.parallax.com/dl/docs/books/edu/toddler.pdf