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Amphibionics 05 3/24/03 8:44 AM Page 172
Amphibionics
easy because all that is needed to coordinate this pattern is to give
each of the servos two sets of movement positions. The body seg-
ments will move through the complete range of motion between the
two sets of points determined by the position values. This means
that we really only need to set the servo positions for all of the ser-
vos twice, and then repeat the pattern to get the snake to move for-
ward. The same holds true when sequencing the servos and body
segments for a left or right turning movement. Figure 5.59 shows
the pulsout values for the extreme and middle positions, along with
the microcontroller port address for each servo. This information
will be needed when putting the control program together.

To sequence the forward movement of the snake, a sine wave pat-
tern can be generated by using the servo position values shown in
Table 5.7. The servos that move the horizontal body segments
also move in a slight side to side movement to aid in locomotion.
Figure 5.60 shows the sequence that the snake’s body goes
through when moving in a forward direction. Frame number 1
shows the snake resting before the sequence begins. Frame num-
ber 2 shows the body segment positions that correspond to the
first set of positions in Table 5.7. Frame number 3 shows that the
snake’s body moves through the original position on its way to the

FIGURE 5.59
Microcontroller port
addresses for each of
the body segment
servos.

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