The boundary conditions may be boundary conditions of a start point and an end point of the trajectory of the center of gravity, which includes a first single leg grounded period in which {HEAD ~ the biped walking robot} stands with {TAIL ~ a first leg} only and a second single leg grounded period in which the robot stands with a second leg only, following the first single leg grounded period 
The boundary conditions may be boundary conditions of a start point and an end point of the trajectory of the center of gravity , which includes a first single leg grounded period in which { HEAD ~ the biped walking robot } stands with { TAIL ~ a first leg } only and a second single leg grounded period in which the robot stands with a second leg only , following the first single leg grounded period
OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD HEAD HEAD REL REL TAIL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH