# Behaviour patterns for omnidirectional hexapod

### 1. Figure of eight sequence

##### Here the hexapod rotates in partial circles or arcs about two points that are separated. These points are called “Instantaneous centres of rotation”. “ICofR” and are specified as x-y coordinates with respect to the hexapod body. The +ve x-axis is to the right side of the body and the +ve y-axis is to the front of the body.

n varies from 0 to 255 where n=0 is the leg tip positioned at its origin, n=63 is the leg tip positioned at the end of its walking-on-the-ground stroke and just beginning its walking-in-the-air stroke, n=127 is the leg tip half way through its cycle and directly above the origin in the air, n=191 is the end of the walking-in-the-airstroke and just at the point of the leg tip placing its tip back on the ground, n=255 is just short of being back at the origin with the leg tip on the ground. Note that there are two values of n called bp1 and bp2, (bp=”breakpoint”), where bp1 is a computed value dependent on the height of the locus walking rectangle called “zag”, (Z air-to-ground value). For example, if the step amplitude, “amp” is amp=40 mm, (i.e. step length of 80 mm), and the height, zag=40mm then bp1=95 and bp2=223; and if zag=0 (not practical) then bp1 merges to 63 and bp2 merges to 191. The purpose of this number design is to ensure that the leg tip spends the same amount of time in the air as on the ground. Remember, that for a double tripod gait that this is the case, i.e. equal time in air as on the ground; but zag will always be greater than zero in order to walk so the path length through the air will be greater than on the ground, thus, the speed of the leg tip through the air has to be greater (and constant) than on the ground. Tricky eh! to compute in real-time. Anyway Frank has worked out a technique where you can still walk in all the other gaits other than double-tripod gait (=3-leg-support-3-swinging), i.e 4-leg support-2-swinging which has numerous variations and 5-leg-support-1-swinging which also has numerous variations.