Section: New Results
Virtual Human Animation
Participants : Julien Pettré, Franck Multon, Steve Tonneau.
Multiped locomotion in cluttered environments is addressed as the problem of planning acyclic sequences of contacts, that characterize the motion. In order
to overcome the inherent combinatorial difﬁculty of the problem, we separate it in two subproblems  : ﬁrst, planning a guide trajectory for the root of the robot and then, generating relevant contacts along this trajectory. This paper proposes theoretical contributions to these two subproblems. We propose a theoretical characterization of the guide trajectory, named “true feasibility”, which guarantee that a guide can be mapped into the contact manifold of the robot. As opposed to previous approaches, this property makes it possible to assert the relevance of a guide trajectory without explicitly computing contact conﬁgurations, as proposed in our previous works. This property can be efﬁciently checked by a sample-based planner (e.g. we implemented a visibility PRM). Since the guide trajectories that we characterized are easily mapped to a valid sequence of contacts, we then focused on how to select a particular sequence with desirable properties, such as robustness, efﬁciency and naturalness, only considered for cyclic locomotion so far. Based on these novel theoretical developments, we implemented a complete acyclic contact planner and demonstrate its efﬁciency by producing a large variety of movements with three very different robots (humanoid, insectoid, dexterous hand) in ﬁve challenging scenarios. The planner is very efﬁcient in quality of the produced movements and in computation time: given a computed RB-PRM, a legged ﬁgure or a dexterous hand can generate its motion in real time. This result outperforms any previous acyclic contact planner.