  The ability to generate robust walking gaits on bipedal robots is key to
their successful realization on hardware. To this end, this work extends the
method of Hybrid Zero Dynamics (HZD) -- which traditionally only accounts for
locomotive stability via periodicity constraints under perfect impact events --
through the inclusion of the saltation matrix with a view toward synthesizing
robust walking gaits. By jointly minimizing the norm of the extended saltation
matrix and the torque of the robot directly in the gait generation process, we
demonstrate that the synthesized gaits are more robust than gaits generated
with either term alone; these results are shown in simulation and on hardware
for the AMBER-3M planar biped and the Atalante lower-body exoskeleton (both
with and without a human subject). The end result is experimental validation
that combining saltation matrices with HZD methods produces more robust bipedal
walking in practice.
