Dynamic of Biped Movement on a Mobile Platform in the Presence Elasticity Elements

 

Mirjana Filipović,

 

This work is concerned with the modeling and analysis of a complex humanoid robotic system walking on a mobile platform. For this purpose, a software package was synthesized allowing the selection of configurations of both the humanoid and the platform. Each joint of the biped and the platform can be defined by the user via the motor state (active or locked) and the gear type (rigid or elastic). In the moment when the biped steps on the platform, the latter, by its dynamics, acts on the biped dynamics and the biped on the other hand, by its characteristics, influences the dynamics of the platform motion. These two complex contacting systems form a more complex system, the mathematical model of which has to encompass all the elements of coupling between the humanoid joints and the platform joints. It has been shown that coupling is more influenced when elasticity elements are included into the configuration. Reference trajectory of each joint can be defined so as to encompass or not encompass elastic deformations as well as known or unknown characteristics of coupling between the humanoid and the platform. The control structure for the biped walking on the platform should be defined so that it satisfies the requirement for the ZMP (Zero-Moment Point) to be within the given boundaries in every sampling instant, which guarantees a dynamic balance of the locomotion mechanism in the real regime. The synthesized new software FLEXI makes it possible to choose a robotic configuration. The analysis of simulation results of the humanoid robot motion on an immobile platform gives evidence for all the complexity of this system and shows how much system parameters (choice of trajectory, configuration, geometry, elasticity characteristics, motor, etc.) influence stabilization of its humanoid motion. All research in humanoid robotics has an aim to create a robot similar to a human that would be his servant, worker or soldier and that would replace him in all dangerous situations.

Key words: robotics, humanoid robot, movement dynamics, mobile platform, modeling, coupling, joint elasticity, programmed trajectory, software package.