Trajectory generation and motion analysis of a four degrees of freedom spatial biped robot for walking with different speeds using Euler parameters

摘要

This article aims at studying the spatial walking motion behavior of a biped robot with only 4 Degrees of Freedom (DoF). Different strategies proposed and trajectories are generated, feasibility of locomotions such as turning and walking in a desired direction are also studied. Implementation of these locomotion features with only four actuators, makes the robot an economic option for many domestic and industrial needs. To study different locomotions mentioned, a stepwise approach to model the kinematics of robot using Euler Parameters is proposed. To study the motion behavior of the robot, a single cycle of walking is divided in two single support phases (SSPs). With the 4 DoF configuration it is not possible to plan the motion trajectories for the entire phase of spatial walking at a stretch, to address this issue motion in each phase is divided further into small segments. These two phases are repeated over a particular duration for continuous walking motion generation. The trajectories are defined for the forward motion such that robot swing foot lands on the ground without any impact. The motion behavior of robot for repeated walking cycles is studied and peculiar motion patterns away from the regular behavior of biped robots is observed. Alternative motion strategy for walking is proposed to rectify the issues using geometric analysis. An approach for generating trajectories for walking with different speeds is proposed based on time scaling approach. Analysis is performed to find the limits of walking speed using zero moment point criteria. Walking strategy for turning right and left are proposed based on geometric analysis of motion. The proposed approach can be used on any 4 DoF robot any size with the same joint configuration. The results obtained from the kinematic analysis can be further used to design the actuation system for developing the robot.