  We present a legged motion planning approach for quadrupedal locomotion over
challenging terrain. We decompose the problem into body action planning and
footstep planning. We use a lattice representation together with a set of
defined body movement primitives for computing a body action plan. The lattice
representation allows us to plan versatile movements that ensure feasibility
for every possible plan. To this end, we propose a set of rules that define the
footstep search regions and footstep sequence given a body action. We use
Anytime Repairing A* (ARA*) search that guarantees bounded suboptimal plans.
Our main contribution is a planning approach that generates on-line versatile
movements. Experimental trials demonstrate the performance of our planning
approach in a set of challenging terrain conditions. The terrain information
and plans are computed on-line and on-board.
