  Hybrid driving-stepping locomotion is an effective approach for navigating in
a variety of environments. Long, sufficiently even distances can be quickly
covered by driving while obstacles can be overcome by stepping. Our quadruped
robot Momaro, with steerable pairs of wheels located at the end of each of its
compliant legs, allows such locomotion. Planning respective paths attracted
only little attention so far.
  We propose a navigation planning method which generates hybrid locomotion
paths. The planner chooses driving mode whenever possible and takes into
account the detailed robot footprint. If steps are required, the planner
includes those. To accelerate planning, steps are planned first as abstract
manoeuvres and are expanded afterwards into detailed motion sequences. Our
method ensures at all times that the robot stays stable. Experiments show that
the proposed planner is capable of providing paths in feasible time, even for
challenging terrain.
