Comparison of different gaits with rotation of the feet for a planar biped

International audienceFast human walking includes a phase where the stance heel rises from the ground and the stance foot rotates about the stance toe. This phase where the biped becomes under-actuated is not present during the walk of humanoid robots. The objective of this study is to determine if this phase is useful to reduce the energy consumed in the walking. In order to study the efficiency of this phase, six cyclic gaits are presented for a planar biped robot. The simplest cyclic motion is composed of successive single support phases with flat stance foot on the ground. The most complex cyclic motion is composed of single support phases that include a sub- phase of rotation of the stance foot about the toe and of finite time double support phase. For the synthesis of these walking gaits, optimal motions with respect to the torque cost, are defined by taking into account given performances of actuators. It is shown that for fast motions a foot rotation sub-phase is useful to reduce the criteria cost. In the optimization process, under-actuated phase (foot rotation phase), fully- actuated phase (flat foot phase) and over-actuated phase (double support phase) are considered

Periodic walking motion of a Humanoid robot based on human data

International audienceHuman walking has been intensely studied, but it is di cult to reproduce on humanoid robots that maintain awkward movements. Three main di culties exist. (i) Di↵erent joint kinematics and size between humans and robots. (ii) A rolling motion of the foot which is often impossible to execute with humanoid robots that walk with their feet flat. (iii) A di↵erence in the dynamic model of a robot compared to a human that makes a copy of a human movement lead to unstable walking. In order to take into account the first two di culties, the specifications for reproducing human movements are adjusted. To ensure stability, a previously developed dynamic model called Essential Model is used. The zero moment point (ZMP) is imposed, and the horizontal evolution of the centre of mass (CoM) is computed to satisfy the ZMP