3-D Command state-based modifiable walking of a humanoid robot on uneven terrain with different inclinations and heights

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.