The align platform function is another of the fuzzy logic functions. It calculates the

difference between the reported stair heading and the current heading of the Andros,

obtained from the Andros' onboard digital compass. The absolute value of the difference

is then compared against the defined fuzzy sets.







 Total Length

 Total Rise

 Run -


 Rise

 Total Run
Figure 3-5: Stair data representation

 If the absolute value is greater than 90 degrees, the Andros is rotated at its maximum

speed. If the absolute value is between 90 and 60 degrees of error, the Andros is rotated

at 75% of its maximum speed. If the absolute value is between 60 and 25 degree of error,

the Andros is rotated at 50% of its maximum speed. Finally, if the absolute value is less

than 25 degrees, the Andros is rotated at 25% of its maximum speed. This function has

an allowable angular tolerance of +/-4 degrees. The direction of the commanded rotation

is also dependent upon a fuzzy interpretation of the angular difference. If the absolute

value of the difference is less than 180 degrees and the actual difference is negative, the

Andros is rotated counterclockwise at the desired speed. If the absolute value of the

difference is less than 180 degrees and the actual difference is positive, the Andros is

rotated clockwise at the desired speed. The direction of rotation relative to the actual