Fixed length chromo somes offer distinct advantages when using CGAs since like areas of each chromosome are more likely to correspond to similar tasks. In order to formulate the problem in such a way as to be able to use a fixed length chromosome some observations of a leg c ycle had to be made. This level of position accuracy is sufficient for our problem, so we can represent all pulses from 0 to 2400 by the numbers 0 to 120 considering each to be in increments of 20 microsecond pulses. This allows us to use a 7 bit number to represent each pulse. It takes 14 bits to represent pulses for both servos.
Smooth movement is required by the horizontal servo, especially while on the ground.
The chromosome representation needed to allow smooth horizontal movement, but smooth vertical movement was not needed since vertical moveme nt does not effect the smoothness of the robot's movement over the ground. Figure 1 . Leg cycle chromosome. In order to accommodate these considerations, the chromosome representation shown in Figure 1 was used. The chromosome was made up of 8 genes.