Online trajectory generation for wide ditch crossing of biped robots using control constraints

Abstract

This work proposes a multibody dynamics approach to generate joint trajectories for a five degrees of freedom biped robot crossing a wide ditch whose width is greater than or equal to the robot’s leg length. Trajectories are generated using control constraints that depend on the horizontal distance traveled by the center of mass and are not explicitly dependent on time. Behavior of the biped robot for various initial postures is studied considering dynamic balance, friction, and impact in order to find the preferred initial postures considering the net energy consumption and peak power requirements at various joints. Several cases of friction, zero moment point location, and the center of mass height variation are considered in the study. Using the proposed approach, feasible trajectories for an adult sized biped robot could be generated for a wide ditch of 1.05 m width at coefficients of friction as low as 0.2. The results obtained are useful for designing reference trajectories and actuation systems for biped robots that need to cross wide ditches or take large steps. Time needed for trajectory generation is found to be sufficiently low for online implementation.