The servo is a modified R/C type with the gear train reduced by one gear to increase speed. The output gear, to which the wheel assembly is fixed, is mounted on the shaft of a quality servo potentiometer. The servo amplifier is unmodified and accepts the normal pulse of about 1 - 1.5 mS width at a repetition rate of about 15mS. The nosewheel runs on a pair of small ball races and is coupled to the optical counter (ex PC mouse). The output is shaped and the leading and trailing edges produce pulses which are combined before being applied to a computer counter to record distance travelled.
In forward motion the L/Hand (1,2 or3), R/Hand (4,5 or6) and single
front (7) sensors are read and, if there is a response, the sensor number is
recorded. A computer timer produces the applied servo pulse and, dependant
on the recorded number, the length of the pulse is adjusted to provide steering
correction.
When running straight, the presence of an adjoining wall to a corner post will be recognized by the outer sensor and can cause a steering error. The read-sensor algorithm takes this into account.
At a suitable time during the passage through a maze square the response from the sensors is noted in memory to indicate the presence or absence of walls and thus builds up a wall map.