Experimental Study on Modifiable Walking Pattern Generation for Handling Infeasible Navigational Commands

Abstract

-To accommodate various navigational commands, a humanoid should be able to change its walking motion in real time. Using the modifiable walking pattern generation (MWPG) algorithm, a humanoid can handle dynamic walking commands by changing its walking period, step length, and direction independently. If the humanoid is given a command to perform an infeasible movement, the algorithm substitutes the infeasible command with a feasible one using binary search. The feasible navigational command is subsequently translated into the desired center-of-mass (CM) state. Every sample time CM reference is generated using a zero-moment-point (ZMP) variation scheme. Based on this algorithm, various complex walking patterns can be generated, including backward and sideways walking, without detailed consideration of the feasibility of the navigational commands. In a previous study, the effectiveness of the MWPG algorithm was verified by dynamic simulation. This paper presents experimental results obtained using the small-sized humanoid robot platform DARwIn-OP.

Stable Walking of Humanoid Robots Using Vertical Center of Mass and Foot Motions by an Evolutionary Optimized Central Pattern Generator

“…This means that the humanoid robot is unable to independently modify the elements of the walking pattern, i.e., the single and double support times, the sagittal and lateral step lengths and the foot direction of the swinging leg. However, in the MWPG, by utilizing the particular solution component for the ZMP variation, the COM position and velocity can be changed independently at any time during the single support phase [6–9]. Thus, the MWPG enables the humanoid robot to modify the elements of the walking pattern independently by means of the ZMP functions p(t) and q(t), without any additional footsteps required for adjusting the COM motion.…”

“…In this paper, the MWPG is employed to generate the modifiable walking pattern for the humanoid robot. As the input of the MWPG, the command state (CS) is defined as follows [6–9]:…”

“…In the 3-D LIPM, to decouple the sagittal and lateral centre of mass (COM) motion equations, the vertical COM motion is not considered. Various walking-pattern generation methods have been developed based on the 3-D LIPM [5–9]. However, the constant COM height only allows the humanoid robot to walk with a limited step length and makes the walking unnatural.…”

“…This paper proposes a method to produce the stable walking of humanoid robots by incorporating the vertical COM and foot motions, which are generated by the evolutionary optimized CPG, into the modifiable walking pattern generator (MWPG) [6–9]. The MWPG extended the conventional 3-D LIPM by allowing a ZMP variation.…”

An Evolutionary Optimization Approach for Optimal Hopping of Humanoid Robots

“…Research on humanoid robots has made rapid progress in dexterous motions along with hardware development [1][2][3][4][5]. Stable walking and running motions are especially representative research issues in humanoid robotics.…”