Conference Paper

A walking pattern generator for biped robots on uneven terrains

Dept. of Comput. Sci., Univ. of North Carolina at Chapel Hill, Chapel Hill, NC, USA
DOI: 10.1109/IROS.2010.5653079 Conference: Intelligent Robots and Systems (IROS), 2010 IEEE/RSJ International Conference on
Source: IEEE Xplore

ABSTRACT We present a new method to generate biped walking patterns for biped robots on uneven terrains. Our formulation uses a universal stability criterion that checks whether the resultant of the gravity wrench and the inertia wrench of a robot lies in the convex cone of the wrenches resulting from contacts between the robot and the environment. We present an algorithm to compute the feasible acceleration of the robot's CoM (center of mass) and use that algorithm to generate biped walking patterns. Our approach is more general and applicable to uneven terrains as compared with prior methods based on the ZMP (zero-moment point) criterion. We highlight its applications on some benchmarks.

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    ABSTRACT: Bipedal robots in previous research work were unable to independently modify the elements of a walking pattern on uneven terrain without any extra footstep for adjusting the center of mass (COM) motion. To solve this problem, this paper extends the modifiable walking pattern generator (MWPG). The MWPG can independently modify the elements of the walking pattern without any extra footstep on flat terrain only. The extended MWPG can be applied on uneven terrain. In the extended MWPG, a 3-D command state is defined to generate the walking pattern on uneven terrain. Instead of using the constant COM height, the vertical COM trajectory is generated to satisfy the foot height of the swing leg. Also, an additional trajectory, generated by the cubic spline interpolation, is supplied to the vertical foot trajectory of the MWPG. The proposed MWPG is implemented on the small-sized bipedal robot, HanSaRam-IX (HSR-IX) and the effectiveness of the proposed MWPG is demonstrated through the experiment.
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    ABSTRACT: This paper proposes 3-D command state (3-D CS)-based modifiable walking pattern generator (MWPG) on the uneven terrain with the different inclinations and heights for humanoid robots. In the previous researches on walking pattern generation on the uneven terrain, the humanoid robot was unable to modify a walking pattern on the uneven terrain without any additional footstep for adjusting the center of mass (COM) motion. Thus, a novel MWPG is developed to solve this problem. It is based on the conventional MWPG which allows the zero moment point (ZMP) variation in real-time by closed form functions. Initially, a 3-D CS is defined as a navigational command set which consists of the foot height and foot pitch and roll angles of the swing leg in addition to the single and double support times and sagittal and lateral step lengths of the swing leg, for walking on the uneven terrain. Next, the COM trajectories in the single and double support phases are generated to satisfy the 3-D CS. Also, the foot trajectory of the swing leg is generated according to the commanded sagittal and lateral step lengths, foot height, and foot pitch and roll angles to walk on the uneven terrain. The proposed algorithm is implemented on a simulation model of the small-sized humanoid robot, HanSaRam-IX (HSR-IX), developed at the Robot Intelligence Technology laboratory, KAIST and the effectiveness is demonstrated through the simulation.

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May 22, 2014